Employment of confocal microscopy, scatterometry & light spectrometry in inspection of diffraction and interference based optical devices for document security

The use of confocal microscopy, scatterometry and light spectrometry in inspection of mass-producible optical devices is addressed. Confocal microscopy enables to locally map the device in 3D. Scatterometry and light spectrometry provide integral information about an internal structure, encoded in spectral and angular variations of reflected or diffracted light power. As the device itself is covered beneath foil or card layers, retrieving objective parameters or characteristics of the device is rather difficult and limited. Examples of measurements on samples are presented using the mentioned techniques and practical usability for expertise analyses is discussed.