Optical pattern recognition system and method for verifying the authenticity of a person, product or thing

DETAILED DESCRIPTION Invisible patterns that cannot be seen and cannot be copied by a detector such as the CCD camera are utilized for verification of the authenticity of items bearing the pattern.
The pattern consists of a two-dimensional phase mask with up to several millions of pixels or higher and it is not holographic.
The large dimensions of the mask make it extremely difficult (if not impossible) to guess the contents of the mask.
The nature of this mask is known only to the authorized producer of the card.
The phase nature of the mask makes it invisible to any conventional intensity detector such as a CCD camera.
This includes the human eye.
For example, one cannot analyze the mask by looking at the card under a microscope or photographing it, or reading it with a computer scanner in an attempt to reproduce it.
The phase mask can be used alone.
For example it can be affixed to a product such as a designer handbag or a computer chip and read by Fourier transform correlators or processors to verify authenticity.
Or the mask can be bonded to another image such as a fingerprint or a picture of a person, and used on an ID or credit card.
It can not be removed without destroying the phase mask and/or the underlying image, which destruction can be verified visually.
In the preferred embodiment, the phase mask and an image of a corresponding reference phase mask are illuminated by coherent light in the input plane of a joint transform correlator (JTC) and the joint power spectrum (JPS) of the two images is inverse Fourier transformed to produce a correlation spot.
If the phase mask is genuine, the intensity of the correlation spot will exceed a predetermined intensity level to produce a verification output signal.