Real-time joint transform correlation with photoanisotropic dye-polymer films

Real-time objects recognition by photoanisotropic copies

The method of object recognition is described by the example of objects of amplitude transparent type. The method is to obtain a photoanisotropic copy of object images on polarization-sensitive material. At consequent illumination of the photoanisotropic copy with a parallel circularly polarized beam of nonactinic light, the transmitted light becomes elliptically polarized. It is shown that the characteristics of the summary polarization ellipse in the Fraunhofer diffraction region uniquely identify the given object. The real-time determination of the characteristics of the summary polarization ellipse is made by means of diffraction gratings of anisotropic profile and by comparison of these characteristics with etalon from the database.

Bifocal-polarization holographic lens

We present a holographic lens with novel features recorded in an azopolymer film. Two holographic modulations, bulk birefringence and surface relief, are induced in the medium at the same time. The resultant holographic element has two focal planes, and the polarization of light in the focal points depends on the polarization of the incident light. Applications of this device for writing-reading information in two planes simultaneously or separately are described.

Polarization gratings with surface relief in dyed gelatin and their postdevelopment diffraction

Some characteristics of dyed gelatin films when polarization gratings are recorded are reported. Two dyes, Malachite Green and Methylene Blue, are used in our experiment. In particular, no dichromate was added to Methylene Blue plates before or after exposure. It is shown that, in spite of its having high viscosity, a relief grating is formed when orthogonal linearly polarized beams are superimposed upon the plates. In contrast with previous observations in another photoanisotropic medium, the frequency of the gelatin relief grating does not depend on the directions of the electric field of the orthogonal recording beams. Besides, when orthogonal circularly polarized beams are used in the formation of polarization gratings, no relief grating is produced. Finally, we study the phase modulation obtained after dehydration of the gelatin plates in which the polarization gratings were formed. Postdevelopment phase gratings do not preserve the polarization information of the interference pattern. Also, the grating frequency is increased by a factor of 2 for linear polarization, whereas for circular polarization there is no phase modulation.