• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.32A no.9
• /
• pp.135-141
• /
• 1995

An optical digital parallel processor using Self-Pumped Phase Conjugate Mirror and liquid crystal spatial light modulator is presented and experimentally implemented. To use self-pumped PCM as memory, the mechanism for phase conjugation in two coupled interaction regions with the photorefractive crystal BaTiO$_{3}$ is investigated, especially the temporal behavior and effects of incident beam position. The optical design and implementation of matrix-vector multiplication using LCSLM and PCM memory is presented.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.29A no.4
• /
• pp.14-21
• /
• 1992

An optical novelty filter is implemented using photorefractive materal(BaTiO$_{3}$) as a recording materal and commercial liquid crystal TV as a spatial light polarization modulator. If a signal beam incident at the proper, the loop and the crossing angle inside th e crystal is formed to get maximum diffraction efficiency and BaTiO$_{3}$ as a self-pumped phase conjugation mirror show that phase conjugate reflectivity was 20 times as much as ordinary polarization if signal beam is extraordinary. In this paper, the stoke's theorem which is a reciprocal theorem for which is a reciprocal theorem for beam path is experimentally proved, and good output images were obtained with optical experiment of novelty filter which is formed by use of Michelson interferometer.

• Proceedings of the Korea Society for Industrial Systems Conference
• /
• 2001.05a
• /
• pp.64-76
• /
• 2001

In this paper, A simple image hologram encryption and decryption technique based on the principle of interference are proposed. The technique using the photorefractive material for getting a stable interference pattern is also proposed. And combine these two techniques, I would like to implement a stable optical information security system. In the encrypting process, I would generate binary phase hologram which can reconstruct original image perfectly, and regard this hologram as original image to be encrypted image. And then the hologram is encrypted as randomly generated binary phase image. Reference image is also generated from the encrypted image by applying interference rule. In the decrypting process, I can get a interference intensity by interfering the reference image and the encrypted image in the interferometer. and transform inferference intensity information into phase information. I recover original image by inverse Fourier transforming the phase information. In this process, the intensity information generated by interference of two images is very sensitive to external vibrations. So, I would like to get a stable interference using the characteristic of SPPCM(self pumped phase conjugate mirror) in photorefractive materials, especially BaTiO₃.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.28 no.8C
• /
• pp.827-834
• /
• 2003

In this paper, we implemented an optical information security system using computer generated hologram based on the principle of interference and BaTiO$_3$that is photorefractive material. First of all, we would generate binary phase hologram which can reconstruct the original image perfectly, and regard this hologram as the image to be encrypted. And then applying the interference rule to the hologram, encrypted and reference (fkey information) images are generated. In the decrypting process, we can get an interference intensity by interfering the reference image and the encrypted image in the Mach-Zehnder interferometer. and transforming interference intensity information into phase information using LCD(liquid crystal display) and finally recover original image by inverse Fourier transforming the phase information. In this process, the Intensity information generated by interference of two images is very sensitive to external vibrations. So, we get a stable interference using the characteristic of SPPCM(self pumped phase conjugate mirror) of BaTiO$_3$that is photorefractive material. The proposed method has an advantage of double image encryption by encrypting the hologram of the image instead of original image.

• Journal of the Korean Institute of Telematics and Electronics D
• /
• v.36D no.9
• /
• pp.56-63
• /
• 1999

Conventional method to improve the response time of the Cat-SPPCM was to increase fanning beam using cylindrical lens. But, in this case the temporal instability of this SPPCM is increased, and fanning beam plays a role as noise, so that it decreases the reflectivity. Thus, fanning beam must be controlled to improve the properties of SPPCM. In this paper, we propose the method to increase the reflectivity of SPPCM and decrease the response time by focusing line-shaped input beam into photorefractive crystal using cylindrical lens and decrease the temporal instability of output beam by using mixed-polarized beam instead of simple extraordinary polarized beam. Optical experiments show that the reflectivity of proposed SPPCM is increased twice and the response time is reduced by 15 times. Also, we observed that the temporal instability of SPPCM is reduced when the polarization angle of the mixed-polarized beam is between $10^{\circ}$ and $30^{\circ}$ . We used a $45^{\circ}-cut\;BaTiO_3$ crystal which has high electro-optical coefficients in optical experiments.