Jong-Yun Kim

Fourier-plane encryption technique based on removing the effect of phase terms in a joint transform correlator

We propose a Fourier-plane encryption technique based on a joint transform correlator (JTC). The technique is based on removing the effect of phase terms in JTC and the auto-correlation terms contribute to reconstructing the original image. Computer simulations and optical experiments show the proposed method is very useful for JTC architecture.

Visual cryptography based on optical interference encryption technique

In this paper, we proposed a new visual cryptography scheme based on optical interference that can improve the contrast and signal to noise ratio of reconstructed images when compared to conventional visual cryptography methods. The binary image being encrypted is divided into any number of n slides. For encryption, randomly independent keys are generated along with another random key based on a XOR process of random keys. The XOR process between each divided image and each random key produces the encryption of n encrypted images. These encrypted images are then used to make encrypted binary phase masks. For decryption, the phase masks are placed on the paths of a Mach-Zehnder interferometer.

Binary image encryption technique and decryption system using joint transform correlator

In this paper a binary image encryption technique and decryption system based on a joint transform correlation are proposed. IN this method, an encrypted image is obtained by multiplying a phase encoded original binary image with a random phase. A Fourier transform of the encrypted, image is used as the encrypted data and a Fourier transform of the random phase is used as the key code. For decryption, the encrypted data is used for one half of the joint input plane, while the key code is used for the other half. After the joint input plane is inverse Fourier transformed, the original binary image can then be reconstructed on a square law device, such as a CCD camera. The proposed encryption technique does not suffer from strong auto-correlation terms appearing in the output plane. In addition, the reconstructed data can be directly transmitted to a digital system for real-time processing. Based on computer simulations, the proposed encryption technique and decoding system were demonstrated as adequate for optical security applications.

Finding the information of the ellipse from the optical Hough transform

A new method to find five parameters of an ellipse from the optical Hough transform results is described. The method employs the Hough transform for detection of a straight line and the 1D analysis of the resultant parameter domain. By using this algorithm, we simulated about the ellipses with different positions, and we obtained the information of the ellipse with 94% accuracy in the worst case. To compare the simulation results with the experimental results, we performed optical experiments by using a HT CGH filter. Through the experiments, we showed that our results were very similar to those of the simulation results.

Binary phase-based optical encryption system using interferometer

In this paper, we propose a new image encryption and decryption system using a phase-modulated random key and the principle of interference. This optical system makes an encrypted image by the multiplication of a random phase key and a phase-modulated image. The random key and an image consist of only binary values. Thereafter a phase value of every pixel of the encrypted image is 0 or pi. The reconstructed pattern of the original image is simply performed by interfering between reference wave and a direct pixel to pixel mapping image of the encrypted image with the same random phase key. In optical experiment, both computer simulation and optical experiment show a good performance of the proposed optical method as encryption scheme.

Optical security system based on computer-generated hologram

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.

Optical Encryption System using a Computer Generated Hologram

A new image encoding and identification scheme is proposed for security verification by us-ing a CGH(computer generated hologram), random phase mask, and a correlation technique. The encrypted image, which is attached to the security product, is made by multiplying a QP- CGH(quadratic phase CGI) 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 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.

Implementation of a holographic optical memory system using a new input and angular multiplexing method

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.