We describe the experimental setup of the image domain joint transform correlator intended for holographic security application. The security verification routine demands two channels. The first one corresponds to the reference hologram stored in the security device. The other is a security holographic mark with several test sub-holograms, applied to a carrier: ID-card, paper seal etc. Each of the holograms stores a part of entire image, stored in the reference hologram. Image domain JTC is used to match the images retrieved from the holograms. The images are recorded by a light addressed spatial light modulator (LASLM). Being recorded and retrieved, the images provides correlation peaks with special positions, with a strict dependence on the tested and reference holograms mutual shifts.
We prove experimentally that the image domain recognizing provides as more effective usage of the LASLM work pupil and resolution as a less device size. The system also has a good tolerance to shift and rotation of the security holographic mark. Few correlation peaks respected to test holograms enhances the device recognizing probability. We provide computer simulations based on the mathematical analysis of the optical signal transforming. The real-time experimental results corresponded with computer simulations are presented.
We describe holographic security system providing machine reading of the holographic information and matching it with the reference one by optical means. The security holographic mark includes several test holograms and should be applied to a carrier: ID-card, paper seal etc. Each of the holograms stores a part of entire image, stored in the reference hologram. Image domain JTC is used to match the images retrieved from the holograms. Being recorded and retrieved, the images provides correlation peaks with special positions, with a strict dependence on the tested and reference holograms mutual shifts. The system proposed works like usual JTC with a few useful differences. The image domain recognizing is a result of Fresnel holographic technique of the images recording. It provides more effective usage of the light addressed SLM (LASLM) work pupil and resolution in more simple and compact device. Few correlation peaks enhances the device recognizing probability. We describe the real-time experimental arrangement based on LASLM. The experimental results are in a good correspondence with computer simulations. We also show in practice that good results may be obtained while using the image domain JTC technique in despite of the low LASLM resolution and the device compact size.
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