A simple distortion-invariant optical identification (ID) tag is presented for real-time vehicle identification and verification. The proposed scheme is composed of image encryption, ID tag creation, image decryption, and optical correlation for verification. To create the ID tag, a binary-phase computer-generated hologram (BPCGH) of a symbol image representing a vehicle is created using a simulated annealing algorithm. The BPCGH is then encrypted using an XOR operation and enlargement transformed into polar coordinates. The resulting ID tag is then attached to the vehicle. As the BPCGH consists of only binary phase values, it is robust to external distortions. To identify and verify the vehicle, several reverse processes are required, such as capturing the ID tag with a camera, extracting the ID tag from the captured image, transformation of the ID tag into rectangular coordinates, decryption, an inverse Fourier transform, and correlation. Computer simulation and experimental results confirm that the proposed optical ID tag is secure and robust to such distortions as scaling, rotation, cropping (scratches), and random noise. The ID tag can also be easily implemented, as it consists of only binary phase components.
This paper proposes a novel simple image encryption and decryption technique based on the principle of interference and a binary-phase computer-generated hologram (BPCGH). To obtain a stable interference pattern, a technique involving a photorefractive material is also proposed. The proposed scheme is composed of digital encryption and optoelectronic decryption. For the encryption process, a BPCGH that reconstructs the original image perfectly is designed, using a simulated annealing algorithm, and the resulting hologram is regarded as the image to be encrypted digitally. In addition, a reference image with key information is created using a random two-phase generator. The hologram is then encrypted using the reference image and the interference rule. For the decryption process, the interference intensity is obtained by interfering the reference image and the encrypted image, binarized with software, and then transformed into phase information. Finally, the original image is recovered by an inverse Fourier transformation of the binary-phase information. During this process, since the intensity information generated by the interference of the two images is very sensitive to external vibrations, a stable interference pattern is achieved using a self-pumped phase-conjugate mirror made of the photorefractive material BaTiO3.
In this paper, we implemented a three dimensional image display system using stereogram and holographic optical memory techniques which can store many images and reconstruct them automatically. In this system, to store and reconstruct stereo images, incident angle of reference beam must be controlled in real time, so we used BPH (binary phase hologram) and LCD (liquid crystal display) for controlling reference beam. And input images are represented on the LCD without polarizer/analyzer for maintaining uniform beam intensities regardless of the brightness of input images. The input images and BPHs are edited using application software with having the same recording scheduled time interval in storing. The reconstructed stereo images are acquired by capturing the output images with CCD camera at the behind of the analyzer which transforms phase information into brightness information of images. The reference beams are acquired by Fourier transform of BPH which designed with SA (simulated annealing) algorithm, and represented on the LCD with the 0.05 seconds time interval using application software for reconstructing the stereo images. In output plane, we used a LCD shutter that is synchronized to a monitor that displays alternate left and right eye images for depth perception. We demonstrated optical experiment which store and reconstruct four stereo images in BaTiO3 repeatedly using holographic optical memory techniques.
A new image encoding and identification scheme is proposed for security verification by using a CGH (computer generated hologram), a random phase mask, and a correlation technique. The encrypted image, which is attached to the security product, is made by multiplying PCGH (phase CGH) with a random phase function. The random phase function plays a key role when the encrypted image is decrypted. The encrypted image can be optically recovered by a 2-f imaging system and automatically verified for a personal identification by a 4- f correlation system. Simulation results show the proposed method can be used for both the reconstruction of an original image and the recognition of an encrypted image.
In this paper, we implemented a holographic optical memory system which can store and reconstruct many image types using a new input and angular multiplexing methods. As a new input method, the phase information of an image is input in the recording material instead of the brightness information. To do so, we represented the images, which were captured with a CCD camera or displaced on a computer monitor, on a liquid crystal television (LCTV) without a polarizer/analyzer. Therefore, we could achieve a uniform beam power regardless of the total brightness of the input image, and could apply a conventional scheduled recording method for the determination of the recording time for all the images needing to be stored. The reconstructed image was acquired by transforming the phase information into brightness information using an analyzer. The reference beam was generated by a Fourier transform of a binary phase hologram which was designed with a simulated annealing algorithm on a LCTV. The LCTV was then interfaced with a computer. The proposed optical memory system is stable because the incident angle of the reference beam is controlled electronically by computer. We demonstrated the system using an optical experiment which stored and reconstructed various types of images in a 45 degree cut BaTiO3 using the proposed holographic memory system.
In this paper, we propose a new angular multiplexing method for storage of the image in BaTiO3. To perform the angular multiplexing, a SA (simulated annealing) algorithm and a LCTV (liquid crystal television) are used. The SA algorithm is used to design a BPH (binary phase hologram) for reference beam generation, and the LCTV is used to modulate the phase. Reference beam is generated by a Fourier transforming of the phase hologram on the LCTV which is controlled by the computer to record and read images in real time. Recording time of each image is determined by scheduled recording method for uniform diffraction efficiency. Through an optical experiment, we show that four images are recorded and reconstructed by the proposed angular multiplexing method.
The optical wavelet circular harmonic function minimum average correlation energy (WCHF- MACE) filter is proposed. The proposed WCHF-MACE filter uses the wavelet transformed image by Mexican-hat wavelet function for circular harmonic function and the multiple harmonic components of circular harmonic function are used for MACE filter synthesis. The proposed filter has good discrimination compared with the conventional circular harmonic function filter and conventional circular harmonic MACE filter about the limited rotated images. And the filter is made of the type of optical wavelet matched filter (WMF), so that the proposed filter can use the conventional 4f correlator.
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