Diffractive Optical Element WinDOE
DOE – Diffractive Optical Element
An optically variable device that appears in a transparent window and is only visible in transmitted light with the assistance of a distant point light source. The transparent window is transformed into an image (usually a banknote denomination) via light diffraction. This device is unique for its ability to be seen best at night or against dim light (fig. 1).
a
b
Fig. 1. Diffractive optical element WinDOE. 50 Kina of Papua New Guinea (2010):
a – view under reflected light ; b – view in transmitted light.
WinDOE is placed in front of a distant point light source