Glossary of Documents

Glossary of Documents

ANTI-SCAN / ANTI-COPY PATTERN

A background image which consist of raster elements or strokes forming a pattern. When copying/scanning a document, text ("COPY", "VOID", etc.) invisible to the naked eye appears on copies or moire appears as rainbow lines, bright and dark stripes, and spots, etc.

Fig. 1. Egypt. Special passport issued in 1999:
a — page 52. Polymer substrate. The area with the anti-copy pattern is marked with a frame; b — the same. Black-and-white copy made on a copy machine. The word COPY in the bottom part of the page has dark contours, is visualized when copying at 200 dpi resolution; c — the same. The symbols of the word COPY are invisible to the naked eye. They are formed by inclined strokes printed at high-resolution. Offset printing


Fig. 2. Latvia. Passport issued in 2002:
a — data page. Paper substrate. The fragment of the anti-copy pattern is marked with a frame; b — the same. Zoomed fragment of the anti-copy pattern formed by lines. Offset printing; с — the same. Moire in the form of dark and bright multidirectional stripes is visualized when copying/scanning at 200 dpi resolution. It appears as a result of two regular patterns overlay: strokes of the original printed image and CCD (charge-coupled device) image sensors of digital printers or copiers


ANTI-STOKES INK

An ink which contains crystals of rare-earth metals (ytterbium, thulium, etc.) and luminesces when exposed to high-intensity IR light 970-990 nm.

Fig. 1. USA. Passport issued in 2006:
a — сover. Gold stamping. White light; b — the same. Anti-Stokes, green luminescence: text, emblem, biometric symbol


Fig. 2. Russian Federation. Residence permit to a stateless person issued in 2012:
a — front endpaper. Paper substrate. Green decorative frame, intaglio printing. White light; b — the same. Anti-Stokes, green and red luminescence of the guilloche frame


Fig. 3. Poland. Service passport issued in 2012:
a — front endpaper. Paper substrate. White light; b — the same. Anti-Stokes, green luminescence over the whole document page


Fig. 4. Poland. Visa issued in 2011:
a — paper substrate; b — the same. Anti-Stokes, green luminescence of the number


BACKGROUND PATTERN

An image or an ornamental pattern which is a background for other images, serial numbers, text, etc. It makes document fraud more complicated as in case of mechanical erasure or etching of either text data, or security features, the background pattern is damaged.

The background pattern consists of:

  • thin parallel or intertwined lines that can have variable thickness and form pseudo-three-dimensional elements due to line curves (regular grid). The lines of the grid may be of one color or multiple colors;
  • microprinting;
  • design elements formed by solid colors;
  • special raster elements, anti-copy and guilloche patterns.

Background patterns are printed by offset, rainbow and Orlov printing.

Fig. 1. Belarus. Diplomatic passport issued in 2010:
a — page 31. Paper substrate; b — the same. Background pattern in the form of a straight-line grid. Rainbow printing


Fig. 2. Tunisia. Diplomatic passport issued in 2003:
a — back endpaper. Paper substrate; b — the same. Background pattern with pseudo-three-dimensional elements formed by intersecting lines. Rainbow printing


Fig. 3. Kuwait. Passport issued in 2005:
a — front endpaper. Paper substrate; b — the same. Background pattern formed by solid colors. Rainbow printing


Fig. 4. Moldova. Permanent residence permit for persons without citizenship issued in 2016:
a — polymer substrate; b — the same. Background pattern formed by microprinting. Rainbow printing


BARCODE

Graphic information in the form of a sequence of lines varying in thickness and (or) rectangular geometric figures. This information is intended to be read by special devices. A barcode may have security features (UV luminescence, magnetic ink, etc.).

Depending on the encoding method, the following types of barcodes are distinguished:

  • a linear barcode is encoded and read in one direction;
  • a two-dimensional barcode is encoded and read not only horizontally but also vertically.

Fig. 1. Brunei. Passport issued in 2008:
a — page 1. Paper substrate; b — the same. Linear barcode. Letterpress; c — the same. Linear barcode. Reverse side of the print. Oblique light


Fig. 2. Azerbaijan. Passport issued in 2007:
a — page 4. Paper substrate; b — the same. Two-dimensional barcode. Zoomed fragment. Laser printing


BINDING TECHNIQUE

A method of fastening the sheets of a folded book block with the cover.

The main techniques used for binding a passport book block:

  • side sewing;
  • thread sewn binding;
  • saddle stitching.

As for side sewing, sheets of a book block are folded and bound with a thread that is passed through the thickness of the book block on the gutter margin, i.e. at a certain distance from the spine. In the other two cases, the sheets are folded and bound with a thread or metal staples along the binding edge.

Fig. 1. Great Britain. Passport. Bottom edge. Side sewing of a book block made of folded sheets (the place of stitching is marked with an arrow)


Fig. 2. Latvia. Travel document issued in 2007:
a — page spread (pages 18-19); b — the same. Top edge. Thread sewn binding of a book block made of folded sheets. The seam of the stitching thread goes 4 mm away from the binding edge


Fig. 3. Kyrgyzstan. Passport issued in 2007:
a — page spread (pages 16-17); b — the same. Top edge. Thread sewn binding of a book block made of folded sheets. The seam of the stitching thread goes through the center of the binding edge


Fig. 4. Belarus. Refugee identity certificate issued in 2000:
a — saddle stitching (binding with metal staples); b — the same. Cover. Zoomed fragment. Metal staple


BLIND EMBOSSING

A colorless relief image applied to the substrate by deforming the material under pressure. On the paper substrate the image is produced by pressure, on the polymer substrate — by pressure and heat (embossing). Visualised in oblique and/or sliding light, has a tactile effect, may have convex or concave relief.

Fig. 1. Madagascar. Passport issued in 2014:
a — back cover. Blind embossing (text and country outlines); b — the same. Zoomed fragment. Oblique light


Fig. 2. New Zealand. Certificate of identity issued in 2016:
a — data page. Polymer substrate. Embossing (marked with arrows); b — the same. Zoomed fragment. An image of a bird with the contours formed by microprinting. Sliding light


Fig. 3. Australia. Emergency passport issued in 2009:
a — front endpaper. Paper substrate; b — the same. Blind embossing. Oblique light


BOOK BLOCK

A type of document construction in the form of a set of folded sheets or sections which are bound together with no cover. Book block elements: inner pages, inserts, endpapers. The book block of passports/travel documents is usually formed by inserting folded sheets in each other. A thread, a metal staple or a thermo thread are used for binding book blocks. A book block has a top edge, a bottom edge and a fore edge. After cutting, the corners of a book block may be square or rounded.

Fig. 1. Forming a book block by inserting folded sheets one into another


Fig. 2. Kuwait. Special passport issued in 2017:
a — a top edge, a fore edge and a bottom edge of the book block; b — the same. Top edge; c — the same. Bottom edge. Book block elements: endpaper, inner pages inserted one into another and sewn to form the spine


CARD

A type of document construction in the form of a rectangle of a standard size.

According to ISO/IEC 7810 there are 4 sizes of identification cards:

Type Size The main use
ID-1 85.60 mm×53.98 mm ID cards, driver's licenses
ID-2 105 mm×74 mm ID cards, driver's licenses, vehicle documents, visas
ID-3 125 mm×88 mm Passports (plastic inserts)
ID-000 25 mm×15 mm SIM cards

A card can be made of a single-layer or multilayer material.

Types of cards:

  • without digital data;
  • with a barcode;
  • with a magnetic stripe;
  • with a chip;
  • combined.

Fig. 1. Germany. Identity card (ID-2 format) issued in 2007:
a — front side. Double-layer paper substrate; b — the same. Transparent laminate covering the paper substrate of the card from both sides; c — the same. Cross-section


Fig. 2. Moldova. Identity card (ID-1 format) issued in 2015:
a — front side. Multilayer polymer substrate; b — the same. Back side. Barcode


Fig. 3. Ireland. Passport card (ID-1 format) issued in 2015:
a — front side. Multilayer polymer substrate; b — the same. Back side. Magnetic stripe at the top of the card


Fig. 4. Croatia. Identity card (ID-1 format) issued in 2015:
a — multilayer polymer substrate. Contact smart card; b — the same. Back side


COVER

An external document coating. A design element in the form of a sheet of thick paper, plastic or cardboard covered with synthetic material. Images and text on the front side of the cover are applied by foil stamping, blind embossing or printed in ink. Printing with UV luminescent or anti-Stokes inks is an additional security feature for the cover. By the properties of document coating, covers can be soft (easily bent) and hard (bent with effort). The cover is attached to the book block. It can be glued, stapled or attached with a thermo thread.

Fig. 1. Denmark. Travel document (Convention of 28 July 1951) issued in 1993:
a — soft polymer cover without endpapers. The cover is bound to the book block with a thermo thread; b — the same. Page spread of a passport book; c — the same. Design element of the cover. Blind embossing and letterpress


Fig. 2. Mongolia. Diplomatic passport:
a — cover; b — the same. Page spread. The cover is attached to the endpapers (marked with arrows) of the book block; c — the same. Material of the cover. Leather texture; d — the same. Stamping with gold foil


Fig. 3. Switzerland. Temporary passport issued in 2003:
a — synthetic cloth covering the soft cover; b — the same. Texture of the cover. Blind embossing (crosses); c — the same. Structure of the cover. Top edge. The cover is bound to the book block with a thread; d — the same. Front side of the cover. UV light


COVERT LASER READABLE (CLR) IMAGE

An image in a hologram that is invisible to the naked eye and cannot be viewed with a microscope. It is visualized in laser light with the help of special devices. It is formed when recording a hologram image using the method of electron-beam lithography. A covert laser readable image is an area on the hologram surface which has specific microrelief of 1 micron in size and less than 1 micron in depth. A laser beam, directed perpendicularly to the surface of this area, is reflected from microrelief elements and forms an image on the device screen.

Fig. 1. Scheme of observing a covert laser readable image. Incident laser beams (red arrows) and reflected laser beams (green arrows) visualize CLR images


Fig. 2. Russian Federation. Passport issued in 1998:
a — data page. Paper substrate; b — the same. Area of CLR image location on the hologram (marked with a frame); c, d, e — CLR images observed when exposed to a green laser 532 nm. Revealed by the visualizer of CLR images in holograms Regula 2305


DATA PAGE

A page of a passport or a travel document on which the issuing authority applies holder’s personal data and data concerning issue and validity. The main holder’s portrait is located on the data page.

The data page of a machine-readable travel document contains a visual inspection zone and a machine-readable zone. The data page may be located on an inner page, an insert or an endpaper.


DATA PAGE INTEGRATION INTO A BOOK BLOCK

A data page is a multilayer polycarbonate construction which is thread-sewn into a book block.

Types of integration:

  • data page is sewn along the inner (binding) edge without using fasteners;
  • data page is sewn using a band;
  • data page is sewn using a band and an additional binding band.

The sewn-in band is made of polymer materials with high flexural strength. One side of the band is bound to the data page, the other side remains loose in the form of a fold. The binding band is laid over the sewn-in band in the place of connection to the data page. Both sewn-in and binding bands may have additional security features, e.g. embossing, UV-luminescent inks, etc.

a

b

c

d

e

f

g

h

Types of data page integration into a document blank:
a — data page is sewn along the inner (binding) edge without using fasteners. Scheme; b — data page is sewn using a band. Scheme; c — data page is sewn using a band and an additional binding band. Scheme; d — Norway. Passport. One of data page inner layers is sewn in along the binding edge; e — Bosnia and Herzegovina. Passport. Data page is sewn using a band; e — Interpol. Passport. Data page is sewn using a band and an additional binding band; f — the same image. Security elements of the sewn-in band: embossing in the form of repeated characters «XO»; g — Sweden. Temporary passport. Security elements of the sewn-in band: UV-luminescent pink ink. View in UV light of 365 nm

DEMETALLIZATION

The process when text or design elements are removed from the metallic layer by a laser or chemical erasure and become visible when viewing in transmitted light.

Fig. 1. Great Britain. Passport issued in 2015:
a — data page. Paper substrate; b — the same. Number made by foil demetallization. Transmitted light; c — the same. Zoomed fragment


Fig. 2. Russian Federation. Passport issued in 2010:
a — data page. Polymer substrate. The Blik security element is marked with a frame; b — the same. View at a right angle of observation and illumination to the document surface. The image on the background is printed in red ink (offset). It is visible through demetallized areas; c — the same. View at an angle of 45°. Holder's portrait; d — the same. Zoomed fragment. The anti-copy pattern and the image are visible through the demetallized areas


DID® DIFFRACTIVE IDENTIFICATION ELEMENT

A diffractive optically variable image (developed by SURYS, France) which contains elements that change their color when rotating the image by 90° (the angle of observation is not changed). DID® is transparent at a right angle of observation that makes it easy to read personal data.

Fig. 1. France. Passport issued in 2013:
a — data page. Paper substrate; b — the same. DID®. View at an angle of 45º in oblique light; c — the same. A color change observed while rotating the image by 90° without changing the angle of observation and illumination. Blue elements become green and vice versa


Fig. 2. Slovakia. Passport issued in 2014:
a — data page. Polymer substrate; b — the same. DID®. View at an angle of 45º in oblique light; c — the same. A color change observed while rotating the image by 90° without changing the angle of observation and illumination. Green elements become orange and vice versa


DOCUMENT / BLANK NUMBER

A unique combination of numbers and (or) letters which is given to every document. It may be applied by letterpress, laser engraving, perforation or printed by a printer. An ink which is used for printing numbers may luminesce in UV and (or) IR light and have magnetic properties. Special fonts and numbering devices are used for applying blank numbers.

Fig. 1. New Zealand. Travel document (Convention of 28 July 1951) issued in 2016:
a — page spread (pages 2-3). Polymer (data page) and paper substrate (page 3); b — the same. Data page. Document number. Relief laser engraving; c — the same. Zoomed fragment. Foaming and blackening (carbonization) of the substrate surface caused by the laser beam; d — the same. Page 3. Blank number. Letterpress; e — the same. Magnetic ink. Image captured by the magnetooptical scanner Regula 7701M; f — the same. Page 3. Blank number. Laser perforation; g — the same. Zoomed fragment. Perforated holes are flat. The edges of the holes and the adjacent areas of the substrate have traces of burning left by the laser beam


DOCUMENT CONSTRUCTION

A form, a material and a structural design of a document. There are following types of a document according to these characteristics: a passport book, a sheet document, a booklet, a card.

DOCUMENT PERSONALIZATION

The process whereby a variable data incorporated into a document. The data allows identifying the document and its holder and verifying whether the document belongs to the holder. According to the way of personalization the data can be read and proceeded both manually and automatically with the help of special scanners, card-readers, etc.

The personal data is applied by laser perforation, laser engraving, or with the help of a printer.

DOT MATRIX (NEEDLE) PRINTING

The print is formed by a print head which consists of a set of pins driven forward by the power of electromagnets. The print head moves line by line along the sheet, with the pins hitting the paper through the ink-soaked ribbon to form a dot matrix image. Dot matrix (needle) printers are used for printing monochrome texts.

Characteristic features of the print:

  • dotted structure of text symbols is noticeable;
  • slight indentation of each dot into the paper.

Fig. 1. Russian Federation. Passport issued in 2010:
a — page spread (pages 2-3). Paper substrate; b — the same. Personalization data. Dot matrix printer; c — the same. Zoomed fragment. Dotted structure of the print. Uneven, blurry contours of the stroke; d — the same. Personalization data. The ink layer left by the ink ribbon of the printer covers the substrate unevenly


ELECTRONIC DOCUMENT (E-PASSPORT)

A document in the form of a book or a card with an electronic chip and an antenna. A microchip contains scrambled holder’s personal data: digital photo, name, data from a machine-readable zone, fingerprints and iris, etc. This data is read by special devices and compared to document personalization data, holder’s physical data and the database. Documents with bio data usually have special mark (fig. 1).

Fig. 1. Azerbaijan. Passport.
Mark which determine the presence of a microchip in the passport.

ENDPAPER

An element of a document construction in the form of a paper sheet which binds a book block to the inner side of the cover. Endpapers are usually manufactured from special security paper which differs from the paper of inner pages. Some documents may not have endpaper made of paper.

Types of endpapers in passports and travel documents:

  • front endpaper (inner side of the cover that precedes the title page);
  • back endpaper (inner side of the cover at the end of the document).


EYELETS / RIVETS

A fixing method which is applied for connection of flat details, for example, a holder’s portrait and a passport page by using a tube section with the flared head (fig. 1).

a

b

c

Fig. 1. Netherlands. Travel document. Convention of 1951:
а — data page with a holder’s portrait fixed by using rivets;
b, c — rivet: frond and back view

FINGERPRINT

A visible graphic reproduction of a holder’s fingerprint uppermost layer (fig. 1). It is a relief lines (papillary pictures). Their structure is determined by a number of friction ridges divided by grooves. These friction ridges form a complex skin pattern which has the following characteristics:

  • individuality — a structure of papillary ridges is individual by its location, configuration and mutual arrangement. They form a special pattern which is unique for every person;
  • relative stability — permanent structure of the uppermost skin layer which remains unchanged throughout the life;
  • ability to recover — After the skin damage papillary ridges recover to the initial state.

Fingerprint identification is the most common, effective and reliable biometric technology.

a

b

c

Fig. 1. Kosovo. Passport:
а — spread (data page and page 3); b — fingerprint image; c — the same zoomed fragment. Inject printing

FLOATING IMAGE

Optically variable element visually perceived as an image hovering or floating in space above or below the document surface.

Characteristic features of the floating image:

  • the effect of floating in space emerges when the image is viewed at a right angle and disappears when viewed at an acute angle;
  • the kinetic effect is perceived as a slight movement of the image together with the observer when the viewpoint is changed.

The effect of floating images is achieved due to multilayer cell-structured laminate which consists of an array of spherical diverging and converging microlenses. According to the laws of geometrical optics, microlenses produce false images which are perceived by the human eye as floating above or below the document surface.

Retroreflective effect characterized by bright luminescence and color changing is observed when color images are viewed in coaxial light.

The effect of floating images. Scheme

a

b

c

Australia. Emergency passport (2014):
a — uneven laminate structure; b — floating images in the form of black-and-white animal figures. View at a right angle; c — the same image viewed when tilted. The figures move in respect to the text lines

d

e

f

Australia. Diplomatic passport (2014):
d — regular laminate structure (3M™ Color Floating Image Security Laminate); e — floating images in the form of red and blue animal figures. View at a right angle; f — the same image viewed when tilted. The figures move in respect to the text lines

g

h

Australia. Diplomatic passport (2014):
g — retroreflective effect. View at a right angle in coaxial light; h — the same image. Zoomed fragment — bright luminescence of the animal figures

FOLDED DOCUMENT

A type of document construction in the form of a sheet folded once or several times.

Fig. 1. Italy. Identity card issued in 1994:
a — front side. Page spread. Paper substrate. The arrow shows the fold line; b — back side. Page spread


Fig. 2. Germany. Travel permit in lieu of passport issued in 1996:
a — folded document. Front side. Paper substrate; b — page spread. The arrows show the fold lines


Fig. 3. Austria. Vehicle registration certificate issued in 1999. Page spread. Paper substrate


GRAVURE PRINTING

A printing technique which uses printing plates where printing elements are recessed as compared with spacing elements. Printing elements are in the form of small raster cells separated by thin dividers. A printing plate is produced on a metal cylinder. During the printing process ink is applied in plenty over the whole surface of the rotating plate. Then a special knife (scraper) removes the ink totally from spacing elements and its excess from printing elements. The ink is transferred to the substrate under the contact pressure.

Special features of the print:

  • no sharp contours and lines;
  • raster lines of spacing elements are visible in the areas of solid fill;
  • minor ink relief;
  • notched edge of an image or stroke contour.

Fig. 1. Republic of Belarus. Passport issued in 1997:
a — back endpaper (data page). Paper substrate; b — the same. Laminate overprint. Fuzzy image contours. White light; c — the same. UV light. Small cells left by spacing elements of the printing plate


Fig. 2. Azerbaijan. Passport issued in 2007:
a — data page. Insert. Paper substrate; b — the same. Text. Notched edge of a stroke contour. White light; c — the same. Text. Small cells left by spacing elements of the printing plate


GUILLOCHE

A graphic element in the form of a complex geometrical pattern which consist of repeated thin curved lines formed according to certain mathematical rules. Guilloche elements form rosettes, frames, borders, vignettes and elements of a background pattern. Guilloche elements can be both positive and negative.

Fig. 1. Russian Federation. Diplomatic passport issued in 1995:
a — front endpaper. Paper substrate; b — the same. Negative (light-coloured, non-printed lines on the dark background) and positive (dark lines on the light-coloured background) guilloche. Intaglio printing


Fig. 2. The Czech Republic. Diplomatic passport issued in 2005:
a — page 17. Fragment of the background pattern formed by guilloche elements. Paper substrate; b — the same. Zoomed fragment. Guilloche. Offset printing; c — the same. Front endpaper. Vignette; d — the same. Zoomed fragment. Vignette. Intaglio printing


HOLDER’S PORTRAIT

An image obtained as a result of taking a photograph of the holder's face. The holder's portrait can be printed by laser engraving, produced on the photographic paper, applied with the help of a printer (except for a dot matrix printer). It is either applied directly to the substrate (an integrated photograph), or glued, or attached with brackets, eyelets to the data page.

Fig. 1. Latvia. Diplomatic passport issued in 2015:
a — data page. Polymer substrate; b, c — the same. Holder's portrait. Laser engraving


Fig. 2. United Nations Organization. Laissez-passer issued in 2001:
a — data page. Paper substrate; b, c — the same. Holder's portrait. Color laser printing. Regular bitmap structure


Fig. 3. Somalia. National identity card issued in 2016:
a — front side. Polymer substrate; b, c — the same. Holder's portrait. Thermal dye sublimation printing, full-color


Fig. 4. Lithuania. Temporary passport issued in 2016.:
a — data page. Paper substrate; b, c — the same. Holder's portrait. Inkjet printing. Irregular bitmap structure


HOLOGRAM

A diffractive optically variable device. Optical properties of the hologram are defined in terms of diffraction of light going through a diffraction grating. Optical effects occur when changing the angle of observation or illumination. Holograms may contain nano-, microprinting, microimages, covert laser readable images, etc.

Classification of holograms by optical properties:

  • Reflection holograms form an image in reflected light. Aluminum foil or a transparent dielectric which reflects not more than 10-20% of light (transparent hologram) are used as a reflection layer.
  • Transmission holograms form an image in transmitted light.

KINEGRAM® is a patented solution produced by the Swiss manufacturer OVD Kinegram and used for protection of security documents and banknotes.

Fig. 1. Romania. Temporary passport issued in 2016:
a — page 2; b — the same. Holograms over the whole document page; c — the same. Diffractive identification device DID® (lower frame, fig. 1b); d — the same. Microtext (upper frame, fig. 1b)


Fig. 2. Iraq. Special passport issued in 2011:
a — page 3; b, c, d — the same. Zoomed fragment. View at different angles of observation


Fig. 3. Great Britain. Visa issued in 2004:
a — visa in the form of a sticker; b, c — the same. KINEGRAM®. View at different angles of observation; d — the same. Nanotext (zoomed fragment of the letter K)


HOLOGRAPHIC MICROPARTICLES OVDot

Faceted metallic particles with the size of 100-600 mcm which are randomly embedded in a substrate all over a document page. Holograms are applied over the surface of microparticles by the electron-beam lithography method and contain a nanoimage or a nanotext. Magnification mode shows how elements of a holographic image change their color at different angles of illumination and observation (fig. 1).

a

b

c

Fig. 1. South Africa. Passport:
а — page 17; b — holographic microparticle embedded in the paper substrate; c — nanotext «SOUTHAFRICA»

HOT FOIL STAMPING

An image formed with the use of a heated die (a form of letterpress printing) which forces the foil against the substrate. The image can be applied to paper, cardboard or a polymer substrate. Due to high pressure, foil particles penetrate deeply into the substrate, making mechanical separation virtually impossible.

Fig. 1. DPRK. Seaman’s passport issued in 2007:
a — data page. Paper substrate; b — the same. Laminate. Silver stamping; c — the same. Zoomed fragment


Fig. 2. Australia. Emergency passport issued in 2009:
a — cover; b — the same. Zoomed fragment. Silver stamping

Fig. 3. Belarus. Passport issued in 1996:
a — cover; b — the same. Zoomed fragment. Gold stamping


Fig. 4. Australia. Travel document (Convention of 28 July 1951) issued in 2009:
a — cover; b — the same. Zoomed fragment. Stamping with black foil


ILLUMINATION

Main terms and definitions:

  • pivot point — a point which is located on the surface of the object (document) and identified as a center when describing its characteristics;
  • axis of illumination — a line connecting the light source and the pivot point of the object;
  • axis of observation — a line connecting the optical system of the observer’s eyes and the pivot point of the object;
  • angle of illumination — an angle between the axis of illumination and the object surface;
  • angle of observation — an angle between the axis of observation and the object surface.

Types of light classified by the wavelength:

  • UV light — UVA (320–400 nm), UVB (290–320 nm), UVC (200–290 nm);
  • white light — visible light with the wavelength of 380–780 nm;
  • IR light — IR (740–1500 nm).

Illumination direction (azimuth):

  • front illumination is directed from the observer’s side towards the X-axis;
  • back illumination is directed from behind the object towards the X-axis;
  • side illumination is directed from the right or left sides of the object towards the Y-axis.

Types of light classified by the angle of incidence:

  • incident (60-90°);
  • oblique (30–60°);
  • sliding light (0–30⁰) is used for visualization of surface relief details;
  • bottom light is used for image visualization in transmitted light.

Illumination classified by the type of the light flow:

  • direct light is a harsh light that creates visible shadows on the object as well as glares on the surface;
  • diffused light is a soft indirect light that casts soft shadows and hides relief details of objects.


INKJET PRINTING

The print is formed of dots as a result of spraying ink from the printer nozzle onto the print-receiving surface.

Characteristic features of the print:

  • images are formed by randomly spread ink blots;
  • ink dots form something like a halo along the contours of letters and digits;
  • color halftone images do not have a regular structure.

Fig. 1. Estonia. Passport issued in 2009:
a — data page. Paper substrate; b — the same. Holder's portrait. Full-color inkjet printing; c — the same. Zoomed fragment. The print is formed by randomly spread colorful ink dots; d — the same. Personalization data. Zoomed fragment. Ink blots of various forms and sizes form a halo along the contours of the letters


INSERT

An additional element of a book block in the form of a separate sheet with numbered or unnumbered pages attached to the main block. Material and method of fixing an insert may differ from typical pages of a book block. One book block can contain more than one insert. The insert can be printed separately.

Types of inserts in travel documents:

  • multilayer integrated card with holder’s data;
  • multilayer polycarbonate sheet with an RFID chip;
  • paper sheet with or without lamination;
  • transparent polycarbonate sheet with a verification filter for visualizing a latent scrambled image.


INTAGLIO PRINTING

A method of printing from metallic printing plates where printing elements are located below spacing ones. The design is cut, scratched, or etched into the printing plate. The printing process is carried out using high-viscosity inks. The ink fills in the recessed areas of the printing plate and is transferred to the print-receiving material under high pressure (about 10000 kg / cm2). The paper substrate is significantly deformed.

Special features of the print:

  • the thick ink layer produces a tactile relief;
  • substrate deformation: concave on the reverse side of the page in the image area;
  • ink spreads at the edges of a print.

Fig. 1. Great Britain. Passport issued in 2010:
a — page spread (pages 2-3). Paper substrate; b — the same. Page 3. Intaglio prints (text) at the top of the page; c — the same. Zoomed fragment. Intaglio print. The arrows show ink spreads at the edges of the print. Oblique light; d — the same. Reverse side of the print. The arrows show substrate deformation in the direction of the front side of the print. Mirrored word OBSERVATIONS. Oblique light



IR FLUORESCENT INKS

Inks containing fluorescent pigments which glow when exposed to visible light of 400-530 nm. Fluorescence appears in IR light of 850-950 nm as bright light images on a dark background.

Fig. 1. Oman. Passport issued in 2014:
a — central page spread with a stitching thread. Paper substrate. White light; b — the same. IR fluorescent inks. A picture on the page spread, a stitching thread


Fig. 2. Slovenia. Diplomatic passport issued in 2009:
a — page 17. Paper substrate. White light; b — the same. IR fluorescent inks. Text, security fibers, a security thread


IR METAMERIC INKS

Inks which have similar spectral features in visible light (perceived as having the same color) but different under IR illumination (some inks absorb IR light, others reflect). When examining an image printed using IR metameric inks, only a part of the image is visible in IR light. This security feature is based on the ability of document materials and inks to absorb or reflect IR light.

Fig. 1. Brunei. Passport issued in 2008:
a — back endpaper. Paper substrate. White light; b — the same. Text fragments which absorb IR light look dark. The background image is transparent in IR light. IR light


Fig. 2. Macau. Passport issued in 2009:
a — page 48. Paper substrate. White light; b — the same. Fragments of the image and text are different in the degree of IR light absorption. So, they look semitransparent or dark on the light background. IR light


IRIDESCENT INK

Semitransparent ink with pearl luster caused by an interference structure of a thin film. The ink contains scaly mica pigments covered by a thin film of titanium dioxide (TiO2), ferric oxide (Fe2O3) or other metal oxides. When falling on pigments, one part of light is reflected, the other part is transmitted into the underlying layers. As a result, multiple reflection and transmission of light by different layers occur and result in interference. The luster is almost unnoticeable at a right angle of observation and illumination. When changing the angle of observation or illumination, the intensity of luster and the hue slightly changes.

Fig. 1. France. Emergency passport issued in 2006:
a — page 8. Paper substrate; b — the same. Zoomed fragment. Iridescent ink. View at a right angle of observation and illumination; c — the same. Zoomed fragment. Iridescent ink pigments


Fig. 2. Japan. Travel document for return issued in 2013:
a — folded document. Front side. Paper substrate; b — the same. The letters JPN printed with iridescent ink. Oblique light; c — the same. Zoomed fragment. Iridescent ink pigments


LAMINATE

A transparent polymer film applied on a document page in order to protect data entries against falsification. May cover the page from one or from both sides. In the latter case, laminate sheets are welded together and form a pouch. The laminate can also be integrated into the passport book by binding. By surface texture, laminates can be glossy, matte or bubble.

Fig. 1. France. Emergency passport issued in 2005:
a — data page. Paper substrate; b — the same. Glossy laminate is bound into the passport book


Fig. 2. Slovakia. Travel identity card issued in 1993:
a — matte laminate; b — the same. Top edge. The laminate base is integrated into the passport book (marked with an arrow)


Fig. 3. Japan. Passport issued in 2013:
a — data page. Paper substrate. Glossy laminate is not integrated into the passport book. The arrows show page fragments not covered with laminate; b — the same. The arrow shows a fragment without laminate


Fig. 4. Australia. Emergency passport issued in 2009:
a — data page. Paper substrate; b — the same. Bubble texture of laminate


Fig. 5. Azerbaijan. Passport issued in 2008:
a — paper substrate. The laminate is integrated into the passport book; b, c — the same. Laminate covers the card from both sides. Front side (b). Back side (c)


LAMINATE OVERPRINT

An image (alphanumeric data) which is applied to the inner surface of the laminate by various printing techniques using special protective inks. When trying to separate the laminate from the data page, the image is destroyed.

Fig. 1. Korea. Travel certificate issued in 2008:
a — data page. Insert. Paper substrate; b — the same. Laminate overprint. Zoomed fragment. Gravure printing


Fig. 2. Belarus. Official passport issued in 2011:
a — data page. Paper substrate; b — the same. Laminate overprint. Offset printing; c — the same. UV light


Fig. 3. Jamaica. Official passport issued in 2001:
a — data page. Insert. Paper substrate; b — the same. Fluorescent overprint. Offset printing. UV light; c — the same. Zoomed fragment. The image is applied to the laminate (not to the paper) as it extends beyond the limits of the paper sheet


LASER ENGRAVING

Applying an image or a photo, letters or figures on a paper or polymer substrate using the energy of a laser beam. A laser beam heats the surface of a substrate (e.g. polycarbonate) releasing carbon into the upper transparent layers. The released carbon is visualized in the form of black dots of different tones which form an image.

When the laser beam affects paper surface, its discoloration occurs, and the ink layer is removed.

Types of images created by laser engraving:

  • vector — when the laser outlines contours of letters or figures, or images with thin lines;
  • raster — when the laser forms a great number of dots applied with different density.

By relief:

  • flat (2D) — applied on materials with nontransparent surface;
  • raised (3D) — felt to touch.

Fig. 1. Slovenia. Official passport issued in 2016:
a — page 1. Paper substrate; b — the same. Laser engraving. Fragment of the blank number. Discoloration and slight charring of paper. Relief is felt to touch; c — the same. Vector image formed as a result of laser engraving on a paper substrate


Fig. 2. Montenegro. Passport issued in 2008:
a — data page. Polymer substrate; b — the same. Zoomed fragment. Holder's portrait. Flat laser engraving. Raster image; c — the same. Fragment of the date. Raised laser engraving. Felt to touch, has raised relief. The surface is foamed and melted by a laser beam


LASER PRINTING

The print is formed as follows: a laser beam illuminates the points on the photoreceptor drum that correspond to the symbols to be printed. The points acquire an electric charge and subsequently, tiny particles of powdered ink (toner) stick to them. The toner is transferred from the drum onto the paper and fixed on it when heated up to +200˚ C.

Characteristic features of the print:

  • strokes are lumpy in dark areas of the image and shiny in oblique light;
  • parched toner particles are scattered chaotically along the contours of letters and digits forming a halo around them;
  • toner particles appear on the non-printed areas of the substrate;
  • color and monochrome halftone images have a regular bitmap structure.

Fig. 1. Moldova. Passport issued in 2009:
a — data page. Paper substrate; b — the same. Zoomed fragment of personalization data Text. Monochrome laser printing. A halo of melted black toner particles at the edges of the stroke; c — holder's portrait. Full-color printing; d — the same. Zoomed fragment. The print has a bitmap structure in the form of a rosette. The rosette is formed by elements of cyan, magenta, yellow and black (CMYK) colors


LATENT FILTER IMAGE LFI

LFI — Latent Filter Image

An image which is applied by the slit raster technology. The scene of the image changes when changing the angle of observation. A latent filter image consists of a slit raster printed inside a transparent polycarbonate which serves as an optical filter and a scrambled image stripped from two initial images (fig. 1). Lightness of the image changes regarding to the background when changing the angle of observation. Latent (second) image is visualized at an acute angle of observation and printed by offset (fig. 2).

Fig. 1. Scheme of a latent filter image visualization:
1 — scrambled interlaced image stripped from initial images A and B;
2 — slit raster; 3 — initial images are visualized at different angles of observation

a

b

c

d

Fig. 2. Estonia. National identity card:
а — reverse side; b — latent filter image: «EST» abbreviation. View at a right angle; c — the same image. View at an acute angle of observation; d — the same image. Slit raster. View at a right angle of observation

LATENT IMAGE KIPP

(from German kippen – to tilt)

An image which consists of parallel lines that are perpendicular to the lines of the background. The latent image KIPP is applied using the intaglio printing plate and appears as an achromatic image in sliding light at an acute angle of observation. It can be visible due to the shadows cast by the raised lines of surface relief. When the document is rotated by 90° without changing the angle of observation, the latent image KIPP becomes either light, or dark compared to the background color.

Fig. 1. Scheme of observing the latent image KIPP


Fig. 2. Kuwait. Passport issued in 2017:
a — front endpaper. Paper substrate; b — the same. Area with a latent image. Latent image is almost invisible. Viewed at a right angle of observation and illumination; c — the same. Zoomed fragment. Parallel lines of the latent image are perpendicular to the lines of the background. Intaglio printing; d — the same. Latent image KIPP. Viewed at an acute angle in sliding light; e — the same. Viewed when the document is rotated by 90° without changing the angle of illumination and observation


LATENT IMAGE PEAK®

(PEAK — Printed and Embossed Anti-Copy Key, developed by Giesecke+Devrient)

An image is formed by two types of lines that are combined during the printing process: 1) parallel lines applied by blind embossing 2) one-color parallel lines of the background applied by offset printing. At a right angle of observation and illumination, the latent image PEAK® is almost invisible. When viewed in sliding light, the lines of the background are visualized on the ridges of relief lines applied by blind embossing and form the latent image PEAK®.

Fig. 1. Scheme of observing the latent image PEAK®


Fig. 2. Kosovo. Diplomatic passport issued in 2008:
a — front endpaper. Paper substrate; b — the same. Area with the latent image PEAK®. Viewed at a right angle of observation and illumination; c — the same. Zoomed fragment. The word KOSOVO is applied by blind embossing. The background (blue lines) is applied by offset printing; d, e — the same. Viewed at different angles of observation and illumination


LATENT MASKED IMAGE

An image formed by lines, strokes of a certain geometrical shape, or raster elements. The latent image is applied by the same printing technique as the background pattern and does not differ from it in color. Its contours are hardly visible to the naked eye. The image can be visualized as a letter, figure, or geometric shape under magnification in white light.

Fig. 1. Sudan. Passport issued in 2014:
a — page spread (pages 26–27). Paper substrate; b — the same. Page 27. Background pattern containing a latent image. The symbols SDN are formed by inclined strokes invisible to the naked eye against the background pattern. Offset printing; c — the same. Page 26. Background pattern containing a latent image. The background pattern masks the symbols SDN that are invisible to the naked eye. Offset printing; d — the same. Zoomed fragment. The symbols SDN are visible under magnification


LATENT MULTICOLOUR IMAGE

An image formed by parallel lines applied by blind embossing and multicolor parallel lines of the background pattern applied by offset printing. The lines are combined during the printing process. At a right angle of observation and illumination, the latent multicolor image is almost invisible. It is visualized in sliding light at an acute angle of observation. When the document is rotated clockwise without changing the angle of observation, the color of every element of the multicolor image changes.

Fig. 1. Scheme of observing a latent multicolor image


Fig. 2. Kosovo. Passport issued in 2011:
a — page spread (page 34 – back endpaper). Paper substrate; b — the same. Back endpaper. Latent multicolor image. Viewed at an acute angle in sliding light; c — the same. The color of the RKS symbols has changed. Viewed when the document is rotated by 90° clockwise without changing the angle of illumination and observation; d — the same. Zoomed fragment. The lines of the latent multicolor image are parallel with the lines of the background pattern


LATENT SCRAMBLED IMAGE

An image formed by strokes or raster elements that are printed in the background pattern or portrait so that the image is not visible to the naked eye. The image is pre-fragmented and encoded using special algorithms. A latent scrambled image is visualized and decoded with the use of decoding devices (filters for visualizing latent scrambled images) or special software.

Fig. 1. Ecuador. Diplomatic passport issued in 2015:
a — front endpaper. Paper substrate; b — the same. Background pattern containing a latent scrambled image. Rainbow printing. Viewed at a right angle of observation and illumination; c — the same. Latent scrambled image № 1 visualized with a filter; d — the same. Latent scrambled image № 2 visualized with a filter; e — the same. Back endpaper. Paper substrate; f — the same. Microprinting in the form of wavy lines containing a latent scrambled image. Intaglio printing. Viewed at a right angle of observation and illumination; g — the same. Latent scrambled image visualized with a filter


Fig. 2. Bulgaria. Passport issued in 2010:
a — data page. Paper substrate; b — the same. Invisible personal information (IPI) on the holder's portrait. Inkjet printer. Decoded and visualized with the Regula Forensic Studio software


LENTICULAR TECHNOLOGY

A method of printing and visualizing an image using lenticular lenses which are used to produce printed images which seem to change or move when viewed from different angles. The term Lenticular is used to define the repeating rows of convex lenses on the front surface of a plastic sheet. The reverse side of the material, however, is a flat surface. Each lens magnifies and projects micro-slices of image data printed on the reverse side. The lenticular technology means that initial images are cut into stripes which are joined so that there is a pair of stripes under each lens — one stripe from one image and the other stripe from the other image. Each lenticular operates as a magnifier which magnifies and isolates only one of the initial images. Coded images are applied by means of printing or laser engraving.

Fig. 3. Latvia. Service passport issued in 2015:
a — data page. Polymer substrate; b — the same. Multiple laser image (MLI). Consists of two initial images: holder's photo and signature. Each image is clearly visible under a certain angle of observation; c — the same. Zoomed fragment. An array of parallel cylindrical lenses with relief surface. Felt to touch. Blind embossing

Fig 4. Estonia. Identity card issued in 2011:
a — front side. Polymer substrate; b — the same. DYNAPRINT® security feature. View at an observation angle of 45°. Image of a bird in the foreground; c — the same. Depending on the angle of observation, one or the other initial image is visible. View at an observation angle of 135º. Image of a flower in the foreground; d — the same. Scheme of forming a coded image. The initial images of the bird and the flower are cut into stripes. The stripes interchange


LETTERPRESS PRINTING

A printing technique when ink is applied to a substrate from a printing plate with printing elements raised above spacing elements. During printing spacing elements do not touch the print-receiving material. The process is carried out under high pressure (at least 15 kg/cm2) with the use of fast-drying inks.

Special features of the print:

  • uneven ink distribution in strokes: less ink in the middle than along the edges;
  • a rim formed by the ink along the edges of a stroke;
  • deformation of the print-receiving material: protuberance on the back side of a sheet and indentation on the front side of a sheet in the area where the print is applied.

Letterpress printing is often used for printing serial numbers, barcodes, and design elements of covers.

Fig. 1. Qatar. Travel document issued in 2005:
a — page 32. Paper substrate; b — the same. Serial number. Front side of the print. Letterpress. Uneven ink distribution in strokes. White light; c — the same. Substrate deformation: protuberance on the back side of a sheet caused by the pressure of the printing plate. Oblique light; d — the same. Zoomed fragment. A rim along the edge of the stroke (marked with arrows)


Fig. 2. China. Passport issued in 2013:
a — data page. Paper substrate; b — the same. Serial number. Two inks applied while using the Orlov printing method. Letterpress. White light; c — the same. UV light


MAGNETIC INK

Ink containing ferromagnetic components which have a specific reaction to the external magnetic field. Images, inscriptions or symbols applied in such ink can be identified by special magnetic sensors or visualized by magneto-optical converters.

Fig. 1. Sweden. Alien's passport issued in 2006:
a — front endpaper. Paper substrate; b — the same. The document number and the background image are printed in ink which contains ferromagnetic components. Visualized by the magneto-optical scanner Regula 7701M


Fig. 2. Azerbaijan. Visa issued in 2012:
a — sticker. Front side. Paper substrate; b — the same. The document number and the barcode are printed in ink which contains ferromagnetic components. Visualized by the magneto-optical scanner Regula 7701M


MAGNETIC STRIPE

A medium in the form of a stripe with the limited storage space. A magnetic stripe is usually placed at the reverse side of a card. The data which has previously been coded recorded on magnetic stripes. The data reading process is carried out by using special devices – readers (fig. 1).

Fig. 1. The United States of America. Arizona. Identity card.
Magnetic stripe at the reverse side of a card

METALLIC INK

Ink containing a fine-dispersed metal powder. It has a specific metallic gloss. Only gloss intensity changes when changing the angle of observation and illumination of the image applied in metallic ink. No significant changes in color are observed. Metallic inks look dark in IR light.

Fig. 1. Estonia. Alien's passport issued in 2014:
a — front endpaper. Paper substrate; b — the same. The coat of arms elements are applied in metallic ink of gold color; c — the same. Front endpaper. IR light


Fig. 2. New Zealand. Diplomatic passport issued in 2016:
a — page 27. Paper substrate; b — the same. Fragment of the see-through register applied in metallic ink of silver color; c — the same. In the bottom right corner, the see-through register looks dark on a light background. IR light



METAMERIC INK PAIR

Special security inks (usually a pair of inks) which look similar in one type of illumination (e.g. in visible light) but show a noticeable difference in another type of illumination (when using a light filter).

Fig. 1. Qatar. Travel document issued in 2016: back endpaper. Paper substrate
a — data page. Paper substrate; b — the same. Parts of the image are printed in different inks (metameric ink pair). In visible light there is no difference in the colour of image parts; c — the same. Image parts differ in colour. Viewed through a red optical filter


Fig. 2. Qatar. Travel document issued in 2016:
a — back endpaper. Paper substrate; b — the same. Parts of the image are printed in metameric inks. Offset printing; c — the same. A dark profile of a bird is clearly visible. Viewed through a red optical filter


Fig. 3. Japan. Passport issued in 2013:
a — page with an RFID chip. Hybrid substrate. The text DO NOT STAMP THIS PAGE is printed in metameric inks; b — the same. In the text DO NOT STAMP THIS PAGE the words do not differ in colour. White light; c — the same. The words STAMP and THIS differ in colour. Viewed through a red optical filter


MICROPRINT

An image (figure / symbol / text) being 0,15–0,3 mm high which is performed by means of printing, blind embossing, demetallization, holography and etc. Microprinting is widely used in security documents where it comes as a background, forms patterns and images, enhances protection of holograms, security threads, etc.

Types of microprinting:

  • positive — dark letters or figures on a light background;
  • negative — light letters on a dark background (so-called "reverse printing", demetallization).

Fig. 1. USA. Permanent residence permit issued in 2010:
a — back side. Polymer substrate; b — the same. Microprint. Stripe with micro images of the U.S. presidents; c — the same. Zoomed fragment. Portrait of Barack Obama


Fig. 2. Ukraine. Passport card issued in 2016:
a — front side. Polymer substrate; b — the same. Negative and positive microprinting. Offset printing


Fig. 3. Greece. Passport issued in 2006:
a — page spread (pages 16-17). Background pattern. Paper substrate; b — the same. The background pattern is formed by microprints. Offset printing


MOIRE VARIABLE COLOR (MVC)

(MVC — Moire Variable Colour, developed by GOZNAK, Russia)

An image formed by parallel lines (applied by blind embossing) which are located at an acute angle to multicolor parallel lines of the background pattern (applied by offset printing). The element is monochrome when viewed at a right angle of observation and illumination. Multicolor moire (rainbow) stripes appear when the image is viewed at an acute angle of observation and illumination. When the document is rotated clockwise without changing the angle of observation, the moire patterns appear and disappear from time to time.

Fig. 1. Scheme of observing the MVC


Fig. 2. Russian Federation. Passport issued in 2010:
a — page 3. Paper substrate; b — the same. MVC. The element is monochrome. Viewed at a right angle of observation and illumination; c — the same. Viewed at an acute angle in sliding light. Multicolor moire stripes are observed; d — the same. Zoomed fragment. Yellow and blue lines of the background pattern — offset printing. The lines applied by blind embossing are at an acute angle to the lines of the background pattern. View at a right angle of observation and illumination


MULTIPLE LASER IMAGE / CHANGEABLE LASER IMAGE (MLI / CLI)

A composite image which consists of several initial images. It is applied and visualized with the use of the lenticular technology. Depending on the angle of observation, one or the other initial image is visible. Consists of lenticular lenses which are embossed into the polymer substrate. Several initial images are cut into stripes and combined into one composite image which is applied by laser engraving under lenticular lenses. Initial images usually contain personal data.

Fig. 1. Scheme of MLI visualization


Fig. 2. Sweden. Emergency passport issued in 2012:
a — data page. Polymer substrate; b — the same. Multiple laser image. Visualization of the holder's portrait at a 45º angle of observation; c — the same. Visualization of the holder's date of birth (yy-mm-dd) at a 135º angle of observation; d — the same. The array of lenticular lenses is applied by blind embossing. Horizontal orientation of the array of lenses


Fig. 3. Finland. Identification card issued in 1999:
a — front side. Polymer substrate; b — the same. Multiple laser image. Visualization of the holder's date of birth at a 45º angle of observation; c — the same. Visualization of FIN abbreviation at a 135º angle of observation. Vertical orientation of the array of lenses


OFFSET PRINTING

A printing technique which uses printing plates where printing and spacing elements lie in one plane. Inks are transferred to the print-receiving surface not directly from the printing plate but via the offset cylinder covered with a rubber blanket.

Traditional offset is a printing technique that includes moistening. Moistening enables the separation of printing and spacing elements due to the difference in their physicochemical properties. The spacing elements attract water while the printing elements attract ink. Every time before ink is applied, the printing plate is dampened with water which adheres to the spacing elements. So they do not attract ink afterwards.

Characteristic features of traditional offset printing:

  • the substrate is not deformed;
  • ink in the strokes is evenly distributed, the thickness of the ink layer is constant;
  • paper fibers can be seen under the strokes.

Dry offset is a printing technique that does not include moistening. In this case, silicone is used to create a layer of spacing elements on the printing plate.

Letterset (indirect letterpress printing) is a technique which combines the elements of letterpress and offset printing. An image is transferred from the letterpress printing plate to the intermediate offset cylinder and then to the print-receiving material.

Letterset prints are characterized by an obviously thicker layer of ink along the boundaries of the print which is typical for letterpress printing (but not for traditional offset printing).

Fig. 1. Switzerland. Service passport issued in 2003:
a — back flyleaf. Paper substrate; b — the same. Background design pattern. Zoomed fragment. Offset printing. No relief. Even ink distribution. Paper texture is seen under the strokes


Fig. 2. Sweden. Emergency passport issued in 2005:
a — page 1. Paper substrate; b — the same. Text. Zoomed fragment. Letterset. A thick layer of ink along the boundaries of the print (marked with an arrow)



OPTICALLY VARIABLE IDENTIFICATION ELEMENT FEEL-ID

A composite security feature based on colour changing and thermochromic effect. It was developed by Giesecke&Devrient company. FEEL-ID has a multilayer structure: 1) The top layer is made using STEP security feature with liquid crystal pigments; 2) The middle layer is made of thermochromic ink; 3) The bottom layer contains laser-engraved identification information (holder's portrait, etc.).

FEEL-ID characteristic features:

  • its colour changes at different angles of observation and illumination (colour changing effect, STEP element);
  • identification information hidden beneath the thermochromic ink layer is revealed when exposed heat (thermochromic effect).

FEEL-ID element structure

a

b

c

d

e

f

Hungary. Passport (2006):
а — data page. FEEL-ID element location; b — FEEL-ID element viewed at a right angle of observation and illumination; c — the same image viewed at an acute angle of illumination and observation; d — view through a polarizer: the dark area on the right indicates that the light reflected from the FEEL-ID element is circularly polarized; e — thermochromic effect: when exposed to heat, thermochromic ink becomes transparent revealing the document holder's portrait; f — laser engraved holder's portrait on the bottom layer. View in IR 840 nm

OPTICALLY VARIABLE IDENTIFICATION ELEMENT FUSE-ID

A composite security feature with identification information about the document holder. FUSE-ID was developed by Giesecke&Devrient company. It is printed with optically variable ink (OVI) and laser engraved afterwards. The element is produced by a laser beam which moves sequentially over the image background area and leaves the image outline untouched. The laser energy discolors optically variable ink by changing its surface nanorelief and optical features. The image contrasts with the brightened background and looks darker. The image color is determined by interference effect which appears on the layered structure of ink pigments.

a

b

c

d

Fig. 1. Latvia. Passport:
а — data page, FUSE-ID element location; b — document holder's portrait viewed at a right angle under front illumination; c — the same image viewed at an acute angle of illumination and observation; d — scheme of image formation by laser engraving the background

OPTICALLY VARIABLE INK (OVI)

An ink that changes its color depending on the angle of observation and illumination. The ink contains a nontransparent scaly pigment with a layered structure that includes a reflective metallic layer, a transparent dielectric layer, and a translucent metallic layer. White light is partially reflected from the translucent metallic layer (surface layer) and partially from the reflective metallic layer (bottom layer). Interference and multiple reflections of light beams by the two reflective layers result in selective absorption of the waves that make up the white light spectrum. The reflected light waves cause the ink color we observe. The ink does not contain coloring pigments. It has metallic sheen. The ink color depends on the thickness of the dielectric layer (MgF2), the angle of illumination and the angle of observation.

Fig. 1. Scheme of OVI visualization. Structure of the ink pigment


Fig. 2. Greece. Passport issued in 2014:
a — data page. Paper substrate; b — the same. OVI: angle of illumination 90°, angle of observation 90°; c — the same. Change of color: angle of illumination 45°, angle of observation 45°; d — the same. Zoomed fragment. OVI pigments: metallic sheen, scaly shape, irregular outline, 100% opacity


OPTICALLY VARIABLE INK WITH EMBOSSING

A complex optically variable security element. It contains an image printed by an optically variable ink OVI which plays a role of the background for the second image applied by blind embossing.

A dual optical effect appears when viewed at different angles of observation and illumination: a color change of the background image and visualization of the second image due a treatment of light and the shade which appears at the ridges of relief elements. An image which applied by blind embossing is not visible at a right angle (fig. 1).

a

b

c

d

e

Fig. 1. Belgium. Passport:
а — data page; b — optically variable ink with embossing. View at a right angle of observation; c, d — the same image at different angles of observation and illumination. Colour and lightness changing effect of an image applied by blind embossing; e — optically variable ink used as a background and blind embossing applied over it

OPTICALLY VARIABLE INK WITH POLARIZING EFFECT STEP

An optically variable iridescent ink which changes its colour at different angles of illumination and observation. It contains liquid crystal pigments with periodic spiral molecular structure. Ink colour depends on the lead of the spiral and angle of illumination. Colour changing effect is achieved due to interference. Incident light reflected from the ink interacts with the spiral of a liquid crystal molecule and becomes polarized.

a

b

c

d

e

f

Latvia. Travel document (2015):
a - page 1, general view, STEP element location; b - observation of optically variable ink properties: colour changing effect at different angles of illumination and observation; c - STEP element at a right angle of observation and illumination; d — the same image at an acute angle of observation and illumination; e - ink structure: iridescent and liquid crystal pigments; f - view through a polarizing filter (dark area on the right) proves that the reflected light is polarized

OPTICALLY VARIABLE MAGNETIC INK (SPARK®, OVMI)

Dynamic color-shifting ink developed by the Swiss company SICPA. Pigments of the magnetic ink used in SPARK® are oriented with the help of the magnetic field so that when the angle of illumination or observation changes, the image changes its color. As result, there is a rolling-bar dynamic effect (a beam of light moving diagonally across the image). Is applied by screen printing, contains ferromagnetic pigments.

Fig. 1. Ireland. Official passport issued in 2013:
a — page spread (front endpaper – page 1). Paper substrate (front endpaper), polymer substrate (page 1); b — the same. Zoomed fragment. SPARK® security feature. Nontransparent metallized pigments; c, d, e, f — the same. A rolling-bar dynamic effect (a beam of light moving diagonally across the image). Color shifting. View at different angles of observation


OPTICALLY VARIABLE PRINTED IMAGE DYNAPRINT®

A composite image which consists of several initial images. It is applied and visualized with the use of the lenticular technology. Depending on the angle of observation, one or the other initial image is visible. The tone, brightness and color saturation of symbols in relation to the background may change. Consists of lenticular lenses which are embossed into the polymer substrate. A number of initial images are cut into stripes and combined into one composite image which is printed under lenticular lenses. Developed by the Swiss company TRÜB AG.

Fig. 1. Estonia. Identification card issued in 2002:
a — back side. Polymer substrate; b — the same. DYNAPRINT® security feature. View at an observation angle of 45º. Light-colored EST symbols on a dark background; c — the same. View at an angle of 135°. Blue EST symbols on a dark background


Fig. 2. Estonia. Identification card issued in 2011:
a — front side. Polymer substrate; b — the same. DYNAPRINT® security feature. View at an observation angle of 45°. Image of a bird in the foreground; c — the same. Depending on the angle of observation, one or the other initial image is visible. Image of a flower in the foreground. View at an observation angle of 135º. Image of a flower in the foreground


ORLOV PRINTING

A method of a single-run multi-color printing invented by Ivan Orlov in 1890 in Russia. It is used for getting prints in which the change of color in strokes is sharp. No displacement, no superimposition or breaking of color. The peculiarity of this printing method: the formation of separate ink layers on color-separated plates and the transfer of the inks to the common plate and then to the receiving surface.

Fig. 1. Russian Federation. Passport issued in 2010:
a — page spread (pages 4-5). Paper substrate; b — the same. Background design pattern. Orlov printing. Sharp and accurate change of color in lines; c — the same. Zoomed fragment. Red and blue lines do not break, overlap or displace in the area where two colours meet


Fig. 2. Japan. Passport issued in 1999:
a — page spread (page 32 - back endpaper). Paper substrate; b — the same. Background design pattern. Orlov printing; c — the same. Zoomed fragment. Sharp and accurate change of color in lines. The colored lines do not break or displace. The arrow marks the area of the color change


PASSPORT

An official document certifying the holder's identity and entitling them to travel to and from foreign countries. It is issued to all citizens in accordance with national legislation. The passport is a booklet, in either hard or soft cover, loaded with security features. It contains personal data of the holder, information about the issuing country and authority, visas, stamps, and other marks. As a rule, each country issues several types of passports: a passport, a diplomatic passport, a service passport, an official passport, an alien’s passport, etc.

Passports differ in the ways of personalization and methods of data processing:

  • passports without the MRZ and embedded microchips;
  • passports with the MRZ containing mandatory and optional data formatted for machine reading using OCR methods;
  • passports with an embedded electronic microprocessor chip (ePassport) which contains secured graphic and text data about the holder and the document itself.

Fig. 1. Haiti. Passport issued in 1992. No embedded microchip:
a — front cover; b — data page without the MRZ. Paper substrate


Fig. 2. Kuwait. Passport issued in 2017. Document with an embedded microchip (ePassport):
a — front cover. The biometric symbol on the passport cover (marked with an arrow); b — data page with the MRZ. Paper substrate



PASSPORT BOOK

A type of a document construction which consists of a folded block of sheets stitched in the spine. It is binded with the help of endpapers or other techniques and then cut from three sides. Additional elements of a passport book are inserts.

PENETRATING INK

Ink that contains a penetrating dye that goes into the fibers of the print-receiving material and shows through to the back of the document. It is usually used in passports and travel documents for applying numbers by letterpress printing.

Fig. 1. Hungary. Passport issued in 2002:
a — page spread (page 32 – data page). Paper substrate (page 32) and polymer substrate (data page); b — the same. Blank number. Front side. Penetrating ink; c — the same. Document number. Back side. Traces of red dye on the reverse side of the print. Oblique light; d, e — the same. Zoomed fragment. Front (d) and back (e) side of the print. Letterpress


Fig. 2. Slovenia. Travel document (Convention of 28 July 1951) issued in 2016:
a — page spread (front endpaper – page 1). Paper substrate; b, c — the same. Blank number (b). Zoomed fragment of the symbol (c). Penetrating ink. Letterpress


PERFORATION

Holes in the substrate, which are arranged in a certain order. They can form a pattern (a holder’s portrait, a document number, etc.).

Perforation can be laser or mechanical.

Laser perforations are created with a laser beam. In this case the holes are of proper shape, have smooth edges and no ridges. The diameter of laser-perforated holes is smoothly reduced from the first perforated page of the document to the last one. Traces of burning left by the laser beam are visible around the edges of the holes. The holes may differ in form: round, triangular, square, asterisk-shaped, etc.

Mechanical perforation is performed with the help of needles or pins. Consequently, ridges are felt to touch on the back of the substrate.

Fig. 1. Australia. Travel document (Convention of 28 July 1951) issued in 2009:
a — additional page 3. Paper substrate; b — the same. Document number. Laser perforation. Traces of burning (marked with arrows) left by the laser beam are visible around the edges of the holes


Fig. 2. Republic of Belarus. Passport issued in 1997:
a — page 16. Paper substrate; b — the same. Document number. Mechanical perforation. Front side. Indentation of the substrate at the edges of the holes; c — the same. Back side (page 15). Ridges at the edges of the holes (marked with an arrow) left by the perforating tool


Fig. 3. Sweden. Passport issued in 2012:
a — data page. Polymer substrate; b — the same. Secondary image of the holder. Laser perforation. Transmitted light; c — the same. Laser-perforated holes. Flat, smooth edges. Transmitted light


PHOTOCHROMIC INK

An ink containing photochromic pigments which change their color when exposed to UV light. After the UV light source is removed, the image printed in photochromic ink stays visible for some time and then becomes pale and disappears. This process can be repeated an endless number of times.

Fig. 1. Gambia. Passport issued in 2002:
a — data page. Paper substrate; b — the same. Image printed in photochromic ink. UV light; c — the same. Zoomed fragment. View in white light, 10 seconds after the UV light source is removed


Fig. 2. Gabon. Passport issued in 2009:
a — data page. Paper substrate; b — the same. Image printed in photochromic ink. UV light; c — the same. View in white light, 10 seconds after the UV light source is removed


PHOTOGRAPHIC PROCESS

A process that allows obtaining images by an optical device on a light-sensitive film and transferring them to photographic paper by chemical means. Photographic paper is covered with a photosensitive emulsion containing silver bromide crystals that are less than 0.001 mm in size. After chemical treatment, sediments of tiny silver particles are formed in the areas of the emulsion that have been exposed to light. These fragments become blurred and nontransparent. The areas that have not been exposed to light become clear and transparent.

Special features of the obtained image:

  • irregular structure in the form of chaotically arranged clouds of tiny spots;
  • gradual change of color, no raster.

Fig. 1. Belarus. Passport issued in 1997:
a — data page. Paper substrate; b — the same. The photo is glued to the data page; c — the same. Zoomed fragment. Gradual change of color, no raster


PLANCHETTES

Thin round or many-sided discs 1-4 mm in size which are made of polymer or metallized material. Planchettes are embedded into the substrate surface during the paper manufacturing process. They are placed randomly or located in a certain area of a sheet. Planchettes can be colorless, colorful, luminesce in UV light, have holographic effects, contain microprinting.

Fig. 1. Australia. Passport issued in 2009:
a — page 19. Paper substrate; b — the same. Colorless planchette; c — the same. Planchette with microprinting in the form of AUS symbols which luminesce in UV light


Fig. 2. USA. Passport issued in 1994:
a — data page. Paper substrate; b — the same. Planchettes with holographic effect located in the upper part of the data page


POLARIZING FILTER

An optical device which transforms unpolarized light passing through it into polarized light. It is used as an analyzer for examination of light reflected from ink or thin-film coating. It blocks light rays of a specific polarization direction and at the same time it lets light rays of other polarization directions pass. A polarizer is placed between the examiner and examined object and the intensity of transmitted light is observed. If the examined light becomes dark, it means that the object reflects polarized light. If the intensity of the transmitted light does not change or changes slightly, it means that the examined light is not polarized.

A polarizer helps to determine if an ink or polymer coating contains liquid crystal pigments which polarize the light passing through them.

a

b

c

d

e

Operation principle of a polarizing filter. Scheme:
a — the light is not polarized: the polarizer lets the light rays pass; b — the light is polarized: the polarizer blocks linearly polarized light; c — circular polarizer for document authenticity verification (R. L. van Renesse. Optical Document Security. Boston | London. 2005. p.351), front side; d — the same image, reverse side; e — STEP element analysis: the light is polarized, the polarizer blocks the light reflected from the ink layer (dark window on the right). Conclusion: the ink contains optically active substances — liquid crystals which circularly polarize reflected light

RAINBOW EFFECT ON LAMINATE

Thin-film coating in the form of a stripe, text or image with the effect of interference color change under different angles of observation and illumination. Does not contain coloring pigments. The coating looks transparent in diffused light. In direct incident light the coating looks bronze red when viewed at a right angle. In oblique light the color of the coating changes to green when viewed at an acute angle.

Fig. 1. Visualization scheme of the color changing effect. The angle of illumination is equal to the angle of observation


Fig. 2. Sweden. Service passport issued in 2001:
a — page spread (pages 2–3). Rainbow effect on laminate (marked with a frame); b — the same. Page 2. Angle of illumination — 90°, angle of observation — 90°; c — the same. Color change effect. Angle of illumination — 45°, angle of observation — 45°; d — the same. Zoomed fragment. Structure of thin-film coating


RAINBOW PRINTING

A special security printing method using one printing plate to obtain prints where one colour gradually merges into another. The printing is carried out with several inks from one color box divided by plates. Special rollers with fixed axial displacement in horizontal direction are used for printing.

Fig. 1. Republic of Belarus. Passport issued in 1997:
a — page spread (front endpaper – page 1). Paper substrate; b — the same. Background pattern. Rainbow printing. The violet color of lines gradually merges into red


Fig. 2. Switzerland. Diplomatic passport issued in 2003:
a — page spread (data page – page 1). Paper substrate (page 1), polymer substrate (data page); b — the same. Rainbow printing. The green color gradually merges into red


RETROREFLECTIVE COATING

Multilayer coating that includes optical elements with retroreflective effect.

It consists of several layers:

  • layer with microlenses (microbeads);
  • layer with graphic images;
  • reflective layer.

When the coating is illuminated by parallel (coaxial) light beams, light semi-transparent images contrasting with the background are visualized (fig. 2). Microbeads focus the light beams so that reflected light returns towards the light source providing a clear visual perception of the image.

Fig. 1. Structure of retroreflective coating


Fig. 2. Netherlands. Travel document for aliens issued in 1995:
a — data page. Paper substrate; b — the same. Retroreflective image. Coaxial light; c — the same. Laminate. Surface microrelief; d — the same. The top layer consists of microbeads (marked with arrows). Cross-section


RIP CUTS

Partial cutting of a substrate upper layer or a laminate coating which prevents a structural damage of a document made with the purpose of its forgery. Rip cuts break down if one tries to separate an upper layer or laminate from the substrate.

Fig. 1. Korea. Passport issued in 1998:
a — data page. Paper substrate; b — the same. Rip cuts on the laminate in the form of dashed lines; c — the same. Zoomed fragment


Fig. 2. Australia. Visa sticker:
a — paper substrate; b — the same. Rip cuts in the form of concentric rings with the crosshairs in the center; c — the same. Zoomed fragment


Fig. 3. United Arab Emirates. Emergency passport issued in 2016:
a — paper sticker over the data page. Paper substrate; b — the same. Rip cuts in the form of concentric rings with the crosshairs in the center; c — the same. Rip cuts in the upper part of the data page"


SCREEN PRINTING

A printing technique that allows obtaining prints by pushing ink through the printing plate. A mesh screen is used as a printing plate. It is made of natural silk, synthetic fabric or metal threads. Spacing elements are covered by a layer that does not let the printing ink through. Printing elements are uncovered. During the printing process, a thin layer of ink is evenly pushed through the mesh screen by a rubber or polymer squeegee onto the print-receiving material. This technique is used for printing images which do not contain thin lines or small details.

Special features of the print:

  • no pressure and substrate deformation;
  • thick ink layer (the layer thickness corresponds to the thickness of the printing plate);
  • zigzag or uneven edges of the image.

Fig. 1. Slovakia. Travel document (Convention of 28 July 1951) issued in 2002:
a — data page. Paper substrate; b — the same. Laminate overprint. OVI. Screen printing; c — the same. Laminate overprint. Screen printing. Zigzag edge of the image. Thick ink layer


SECONDARY HOLDER’S IMAGE

A repeated image of the holder's portrait which is reproduced in the document once or several times. It is reduced in contrast and/or size and applied using the same printing technique as the holder’s portrait or a different one. It can be located on the data page or other pages of a document.

Fig. 1. Cuba. Service passport issued in 2001. Reverse side of the data page. Secondary holder's image. Laserprinting. Paper substrate


Fig. 2. New Zealand. Diplomatic passport issued in 2009. Data page. Secondary holder's image in a transparent window (b). Laser engraving. Polymer substrate. Transmitted light


Fig. 3. Korea. Passport issued in 2002. Data page. Secondary holder's image. Transparent UV fluorescent ink. Paper substrate. UV light


Fig. 4. Sweden. Identification card issued in 2005. Secondary holder's image. Laser perforation. Polymer substrate. Transmitted light (b)


Fig. 5. Russian Federation. Passport issued in 2010. Data page. Secondary holder's image. Demetallization ("Blik" security element developed by Goznak (Russia). Polymer substrate. Oblique light


Fig. 6. Germany. Passport issued in 2005. Data page. Secondary holder's image. Hologram on laminate. Oblique light


SECURE CORE PRINT (SCP)

An image (pattern, alphanumeric characters, etc.) located on the inner layer of a multilayer polycarbonate card. It is printed with special inks and visualized in transmitted light in the form of a dark image against a light-coloured background. SCP is also considered a pseudo watermark.

Fig. 1. Structure of a multilayer polymer card. Layer with Secure Core Print


Fig. 2. Latvia. Passport issued in 2015:
a — polymer substrate; b — the same. Transmitted light; c — the same. Zoomed fragment. Secure Core Print. Transmitted light


Fig. 3. New Zealand. Passport issued in 2016:
a — data page. Polymer substrate; b — the same. Secure Core Print in the form of a fern frond. Transmitted light (the image contours are marked with arrows)


SECURITY FIBRES

Fine synthetic fibres that are added to the paper pulp during the manufacturing process. Security fibres can be found all over the document page or concentrated in a certain area. May luminesce in UV, IR light.

By visibility to the naked eye:

  • visible / colored;
  • invisible / colorless.

By color:

  • monochrome;
  • two-colored or multicolored with alternate fragments of various colors.

By form:

  • simple threadlike security fibres with a constant cross-section;
  • complex security fibres with a variable cross-section (ZONA security fibres developped by GOZNAK, Russia).

Fig. 1. Azerbaijan. Passport issued in 1998. Visible simple monochrome fibres


Fig. 2. Great Britain. Passport issued in 2010:
a — invisible (colorless) simple fibres; b — the same. UV light; c — two-colored simple fibres in white light; d — the same. UV light; e — security fibres concentrated in the area near the stitching thread on page 3


Fig. 3. Russian Federation. Passport issued in 2010:
a — ZONA security fibres, two-colored with a variable cross-section; b — the same. UV light


Fig. 4. Kosovo. Diplomatic passport issued in 2011. Page 17. Colorless simple security fibres luminescing in IR light


SECURITY THREAD

A narrow polymer or metallic stripe embedded in a paper web during the paper manufacturing process. It is verified in transmitted light.

Types of security threads:

  • a latent security thread is completely embedded in paper;
  • a windowed (diving) security thread appears partially on the paper surface. In reflected light it looks like a dashed line, in transmitted light — like a solid dark stripe.

Security threads may be colored and may incorporate microprinting, optically variable, UV and IR luminescent features.

Fig. 1. Poland. Passport issued in 2001:
a — page 1; b, c — The same. Latent security thread. Transmitted light (b). Cross section of a document page (c)


Fig. 2. Kosovo. Passport issued in 2011:
a — page 17; b, c, d — the same. Latent security thread. Transmitted light (b). IR light (c). RKS microprinting on the security thread (d)


Fig. 3. Russian Federation. Passport issued in 2010:
a — page 45. Windowed metallized security thread with a colour shifting effect; b, c, d — the same. Transmitted light (b). Color change effect (c, d) at different angles of observation


Fig. 4. Sweden. Emergency passport issued in 2011:
a — front side; b — the same. MOTION® security thread. UV light; c, d — the same. Transmitted light (c). White light (d). The image of a plane moves when changing the angle of observation or illumination (d)


SEE-THROUGH REGISTER

An image the parts of which are printed on the front and reverse side of a page. In transmitted light, image elements on the front side are complemented by the elements printed on the reverse side. As a result, a complete image is formed without any obvious shifts, overlays or gaps.

Fig. 1. Serbia. Service passport issued in 2008:
a — page spread (pages 16-17). Paper substrate; b — the same. See-through register, the front side. Offset printing; c — the same. See-through register, the reverse side. Offset printing; d — the same. See-through register. Transmitted light. The elements on the front and reverse side of the page are combined to form a whole image without gaps, overlays, and shifts


SELF-VERIFYING FILTER

A transparent part of a multipage document which allows visualizing latent images, texts or codes located on an adjacent page of the document. During the verification process the filter is placed closely to the image area and scrambled data becomes clearly visible.

A self-verifying filter may have the form of a clear window in one of document pages or can be located on a transparent polycarbonate insert stitched into a passport book (fig. 1).

a

b

c

Fig. 1. Belgium. Passport:
а — data page and insert with a self-verifying filter; b — self-verifying filter placed on the holder’s portrait; c — latent scrambled image (personal data), visualized with the help of the filter

SINGLE SHEET DOCUMENT

A type of document construction in the form of a sheet of paper without folds. It can be used as a separate document or a sticker on document pages.

Fig. 1. Sweden. Emergency passport issued in 2011:
a — front side. Paper substrate. Size — 210×297 mm. It is used as a separate document; b — the same. Back side; c — the same. Front side. UV light


Fig. 2. Estonia. Permanent residence permit:
a — sticker. Front side. Paper substrate on a self-adhesive base. Size — 70×91 mm. Applied on a document page; b — the same. UV light


SLIT RASTER TECHNOLOGY

A method of printing and visualization of images using a slit raster which allows getting an image changing effect depending on the angle of observation. A slit raster (optical analog of a lenticular) is a transparent film on which a pattern is printed. The pattern consists of parallel transparent and non-transparent stripes. A scrambled interlaced image is printed under the slit raster (principle of coding is the same as in lenticular technology).

Depending on the angle of observation only one of stripes of the encoded image are visible through transparent stripes of the pattern. Non-transparent stripes blocked up the other stripe. Images are printed by offset or laser engraving (рис. 1–2).

a

b

Fig. 1. Slit raster technology scheme:
1 — initial images А and B divided on a number of stripes which is multiple of a number of lenses; 2 — slit raster; 3 — scrambled interlaced image

Fig. 2. Scheme of image visualization at different angles of observation:
1 — encoded image; 2 — slit raster. Images А and B are visualized alternatively at different angles of observation

SPINE

The edge of a book block where all elements of a passport book are stitched.

a

b

c

Fig. 1. Ireland. Passport. 2013:
а — front side of a cover; b — central spread with a stitching thread; c — the same, top view

STAMP (SEAL)

A seal, an impression, a mark or relief formed as a result of pressing a special tool (stamp) to a paper substrate.

Types of stamps differ according to the application method:

  • ink stamps — flat impressions on the substrate;
  • dry stamps — impressions in relief; no ink is used.

A dry stamp is viewed under oblique light and perceived by touch. Substrate deformation is observed both on the front and back of the stamp. The embossed elements on the front are absolutely similar to the depressed elements on the back.

Fig. 1. Azerbaijan. Passport issued in 2007:
a — page spread (pages 2-3). Paper substrateт; b — the same. Ink stamp; c — the same. Zoomed fragment. No relief


Fig. 2. Viet Nam. Passport issued in 1993:
a — page spread (pages 2-3). The holder's portrait is glued and stamped; b — the same. Dry stamp; c — the same. Zoomed fragment. The surface relief is visible in oblique light


STITCHING THREAD

A material that is used for holding together pages of a book block. Consists of strands that are twisted or stuck together. Stitching threads vary in the number of strands, material, color and formation method. Synthetic threads that may have security features (luminescence in UV and IR light, etc.) are used for stitching passports and travel documents. A stitching thread seam is a succession of stitches placed at regular intervals. Edge stitches can be sewn several times.

Fig. 1. Qatar. Travel document issued in 2016:
a — page 25. Paper substrate; b — one-color twisted stitching thread. White light; c — the same. UV light


Fig. 2. USA. Passport issued in 2006:
a — page 15. Paper substrate; b — two-color two-strand stitching thread. Complicated lockstitch. White light; c — the same. Zoomed fragment; d — the same. UV light


Fig. 3. Moldova. Official passport issued in 2015:
a — page 17. Paper substrate; b — three-color three-strand stitching thread. Edge stitches are sewn twice; c — the same. UV light


Fig. 3. Denmark. Allien's passport issued in 1993:
a — page 17. Paper substrate; b — the same. Polymer thermo stitching thread; c — the same. Zoomed fragment


SUBSTRATE

A special material used to produce documents, a background for applying images and embedding of security features.

Main types

Paper is a thin (4–400 mcm) sheet consisting mainly of specially treated small bounded and stitched plant fibers. A special paper is used for printing documents and securities. It contains such security features as watermarks, security fibres and threads, etc. Usually paper doesn’t luminesce in UV-light, contains special supplements and chemical components which prevents mechanical and chemical erasures and other types of forgery.

Photographic paper is a nontransparent material on a paper substrate with light-sensitive chemicals which is used for making positive photo image.

Polymer substrate is an acrylonitrile butadiene styrene, polyester, polycarbonate, polyvinyl chloride.

Fabric is a natural, synthetic, carton, denim or other coating materials which are used for producing document.

THERMAL DYE SUBLIMATION PRINTING / THERMAL TRANSFER PRINTING

The print is formed with the use of an ink ribbon which is placed between the thermal print head and print-receiving material. The ink ribbon is made of a thin synthetic material and then applied to the external surface of a layer of solid ink (yellow, magenta, blue and black).

In the process of thermal dye sublimation printing, the thermal print head is heated and touches the inner surface of the ink ribbon. As a result, the solid ink on the ribbon heats up and evaporates. It is converted from a solid directly to a gaseous state without going through a liquid phase (that is why the process is called thermal dye sublimation). Due to the formation of a gaseous cloud of ink, the ink transfer occurs without direct contact of the print head and the ink ribbon with the surface of the print-receiving material. Therefore, the edges of the raster elements turn out to be blurred.

Characteristic features of the print:

  • halftone color images render smooth transitions in tones;
  • monochrome letters and figures have zigzag contours of inclined elements.

In the process of thermal transfer printing, the thermal print head presses the ink ribbon directly onto the surface of the print-receiving material, forming an impression without the ink turning into a gaseous state. As a result, halftone color images have a regular bitmap structure in the form of oval dots (traces of the print head).

Fig. 1. Zimbabwe. Passport issued in 1998:
a — data page. Paper substrate; b — the same. Holder's portrait. Dye sublimation printing. Smooth transitions in tones, no raster elements; c — the same. Personalization data – text fragment. Thermal transfer printing. Steplike contours of inclined letter elements


Fig. 2. Greece. Passport issued in 2014:
a — data page. Paper substrate; b — the same. Holder's portrait. Thermal transfer printing. Regular bitmap structure of the image; c — the same. Personalization data – text fragment. Thermal dye sublimation printing. Zigzag contours of inclined letter elements. The ink ribbon covers the impression with ink unevenly, when it comes in contact with the substrate


THERMOCHROMIC INK

An ink which changes colour or becomes transparent due to a change in temperature. The thermochromic effect is caused by changes in the chemical composition or physical properties of thermosensitive pigments. Thermochromic ink may have more than two color changes at different temperatures.

Fig. 1. Ireland. Passport card issued in 2015:
a — front side. Polymer substrate; b — the same. Image printed with thermochromic ink. View at a temperature of about 20 ˚С; c — the same. View when heated to 40 ˚С. Change of transparency


Figс. 2. Ireland. Passport issued in 2013:
a — page 6. Paper substrate; b, c, d — the same. Image printed with thermochromic ink. Change of color (grey – green – yellow) as the temperature increases up to 40 ˚С; e — the same. Zoomed fragment. Thermosensitive ink pigments. View at a temperature of about 20 ˚С; f — the same. Zoomed fragment. Thermosensitive ink pigments at a temperature of 40 ˚С


THERMOGRAPHIC PRINTING

Thermographic printing (raised printing) is a post print technology of producing a tactile raised print. The printed area is dusted while wet with low-melting polymer powder which sticks to the ink. The excess powder is removed from non-printed areas by shaking off or blowing off. Then the substrate is heated, and, as a result, the powder melts and forms a raised relief on the substrate. The powder that is used in thermographic printing can be transparent, glossy or matte.

Fig. 1. Moldova. Emergency travel document issued in 2013:
a — single sheet document. Front side. Paper substrate; b — the same. Zoomed fragment. Thermographic printing. Raised relief is formed by transparent melted polymer powder. Glossy prints


Fig. 2. Moldova. Visa:
a — paper substrate; b — the same. Zoomed fragment. Thermographic printing. Raised relief is formed by transparent melted polymer powder with a yellowish tint (marked with arrows); c — the same. Zoomed fragment. Thermographic printing. Glossy melted polymer powder extends beyond the edges of letters (marked with an arrow). View at an acute angle of observation


THIN-FILM INTERFERENCE

Thin-film interference is a phenomenon of two or more light waves superposition which causes their mutual amplification or reduction depending on how the phases of these waves are related to each other. A light beam 1 with a wavelength (λ) falls on the film at an angel (α) and is reflected at the point A. A light beam 2 travels in the film, is reflected from its lower boundary at the point B, is refracted at the point C and returns into the air (fig.1). The path difference appears between two adjacent reflected beams 1 and 2. A light beam 1 passes the distance equal to the interval ABC multiplied by the refractive index (n). But at the point C a part of the light beam is reflected down again, at the point В1 is reflected up, etc. Thus the connection of many waves occurs as a result of consequent reflections of incident light from the lower boundary of the transparent film. This calls multiple beam interference.

If the interval ABC is a whole number of wavelengths, their peaks and troughs will coincide and amplification of all the reflected waves will occur (interference maximum). When the film is illuminated by white light, consisting of waves of different frequency and length, light is refracted at the boundary between the media, and a part of the spectrum is eliminated. The interference maximum occurs for a specific wavelength (red, green or blue) at a certain film thickness and angle. In reflected light the film will have a color corresponding to a certain wavelength. This phenomenon is called “colors in thin films”.

Fig. 1. Multiple beam interference scheme:
λ — wavelength of incident light; α — angle of incidence; β — refraction angle; n — refractive index; h — thickness of the film.
Conditions of the interference maximum: coincidence of peaks and troughs (phase) of waves 1, 2, 3

Fig. 2. Colours in thin films.
The interval ABC is equal to the length of a red light  interference maximum is achieved, phases of reflected and refracted waves are equal.
The film is coloured red

TRANSPARENT / CLEAR WINDOW

A transparent non-printed area in the substrate. It is used as a filter for visualizing latent scrambled images when a secondary holder's image is applied to the adjacent page. This feature protects a security document against illegal copying / scanning.

Fig. 1. Sweden. Passport issued in 2011:
a — page spread (pages 2-3); b — the same. Page 2. Transparent window. Polymer substrate. Transmitted light; c — the same. Page 1. Turning the data page to place the transparent window (marked with a frame) over the secondary holder's image on page 3; d — the same. Zoomed fragment. Transparent window. When capturing the image, a sheet of white paper is placed under the transparent window. The number on the transparent window is laser engraved; e — the same. Transparent window placed over the secondary holder's image on page 3. IPI (invisible personal information) is visualised with the help of a filter


TRAVEL DOCUMENT

An official document issued by a state or an organization which is used by its holder for traveling to different countries and contains the obligatory visual inspection data.

Machine-readable travel document (MRTD) is also contains the obligatory brief data in the form which can be read and verified by machines.

Types of documents:

UV FLUORESCENT HI-LITES

Small colored or colorless particles of different sizes randomly embedded in the paper pulp during paper sheet formation. The particles glow when exposed to UV light.

Fig. 1. Greece. Passport issued in 2014:
a — page 17. Paper substrate. UV light (365 nm); b — the same. UV fluorescent hi-lites of different colors are randomly distributed on the surface of the page; c — the same. Zoomed fragment. UV fluorescent hi-lites of different sizes and forms


UV FLUORESCENT INK

An ink containing luminophores. When exposed to UV light (250–380 nm), the luminophores transform UV light into fluorescent light of different colors visible to the naked eye.

Fig. 1. Kosovo. Passport issued in 2013:
a — data page. Paper substrate; b — the same. UV light (365 nm); c — the same. UV light (254 nm)


Fig. 2. Hungary. Service passport issued in 2012:
a — data page. Hybrid substrate; b — the same. Fluorescent ink: smooth transition of color in vertical direction. Rainbow printing. UV light (365 nm); c — the same. UV light (254 nm)


VARNISH COATING

A transparent 20-40 mcm thick film which is invisible by the naked eye at a right angle. It protects the substrate from getting wet and prevents ink erasure. Varnish coating is visualized as a coating with slight gloss visible at an acute angle. It is applied over a printed image or creates an independent colorless image.

a

b

Fig. 1. Belgium. Vehicle registration certificate:
а — outside spread of a booklet; b — varnish right-angled coating covering the right part of the number «714980» applied by letterpress

VISA

Permission to enter and/or exit the territory of a country made in the form of a sticker, an insert, a stamp or a small sticker. A visa is placed on special pages of a travel document or it can be issued as a separate document.

Fig. 1. Poland:
a — visa in the form of a sticker issued in 2004. Paper substrate; b — the same. UV light; c — the same. IR light


Fig. 2. Turkey:
a — visa in the form of a small sticker. It is applied on visa pages of a travel document. Paper substrate; b — the same. UV light


Fig. 3. Lebanon. Visa in the form of an ink stamp on a visa page of a travel document



WATERMARK

A paper security feature which is visible in transmitted light as an image appeared due to local differences in paper density. A watermark is formed on a wet paper web in the process of paper production. It is formed by the density of fibres on certain areas of an image. Darker areas contain more fibers. Lighter areas contain a smaller amount of fibers. Watermarks differ by several criteria.

By location:

  •  General — an image repeated at regular intervals all over a document page.
  •  Local — an image located in a certain place of a document page.

By general paper tone:

  •  Single-tone — consists of dark or light elements of an image compared to a general paper tone.
  •  Duotone — consists of dark and light elements of an image compared to a general paper tone.
  •  Multitone — consists of dark and light elements of an image compared to a general paper tone which are gradually transforming into each other.