Computer-generated holograms and diffraction gratings in optical security applications

Pawel J. Stepien

doi:10.1117/12.382191

7 April 2000 Computer-generated holograms and diffraction gratings in optical security applications

Pawel J. Stepien

Proceedings Volume 3973, Optical Security and Counterfeit Deterrence Techniques III; (2000) https://doi.org/10.1117/12.382191
Event: Electronic Imaging, 2000, San Jose, CA, United States

Abstract

The term 'computer generated hologram' (CGH) describes a diffractive structure strictly calculated and recorded to diffract light in a desired way. The CGH surface profile is a result of the wavefront calculation rather than of interference. CGHs are able to form 2D and 3D images. Optically, variable devices (OVDs) composed of diffractive gratings are often used in security applications. There are various types of optically and digitally recorded gratings in security applications. Grating based OVDs are used to record bright 2D images with limited range of cinematic effects. These effects result form various orientations or densities of recorded gratings. It is difficult to record high quality OVDs of 3D objects using gratings. Stereo grams and analogue rainbow holograms offer 3D imaging, but they are darker and have lower resolution than grating OVDs. CGH based OVDs contains unlimited range of cinematic effects and high quality 3D images. Images recorded using CGHs are usually more noisy than grating based OVDs, because of numerical inaccuracies in CGH calculation and mastering. CGH based OVDs enable smooth integration of hidden and machine- readable features within an OVD design.

Citation Download Citation

Pawel J. Stepien "Computer-generated holograms and diffraction gratings in optical security applications", Proc. SPIE 3973, Optical Security and Counterfeit Deterrence Techniques III, (7 April 2000); https://doi.org/10.1117/12.382191

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