The existing optical cryptosystems always process the plaintexts into a random noise image, and the length of the key in the encryption progress is generally much longer than that of the plaintext. In this work, a Harr-wavelet-based optical cryptosystem using the convex lens is proposed. This scheme only needs recording the amplitude. The encryption key includes a series of parameters which is quite shorter than the length of the plaintext. These keys are natural inherent parameters. The Harr transform is introduced to improve the sensibilities of encryption keys and reduce the length of the ciphertexts. The ciphertext is a diffraction-pattern-like image which contains no information of plaintext. Besides, the cost of the whole optical encryption is reduced heavily. Extensive numerical simulations are carried out to verify the security, feasibility, and sensibilities of encryption keys of the proposed encryption scheme. In addition, how to properly select encryption keys is also discussed.
All optical systems are affected by aberrations, and optical encryption systems with lens are no exception. In order to improve the practicality of the optical encryption system, the influences of aberration on the double random phase encoding (DRPE) system are studied. In this paper, Zernike polynomials are used to express the aberration of the lens. Simulation has been carried out. The influences of different types, coefficients, and combinations of aberrations on DRPE system are analyzed. The results of the study indicate that some Zernike polynomials(such as the 4th Zernike polynomial, etc.)will have a greater impact on DRPE system, while some combinations, such as the combination of the 4th and 9th Zernike polynomials, will reduce the influences of aberrations on DRPE system. Besides, the degree to which DRPE system is affected by aberrations is evaluated by the correlation coefficient between the decrypted image and the plaintext. In order to solve the problem of aberration, two solutions are proposed.
Recently the combination of adaptive optics and ophthalmology has made great progress and become highly effective. The retina disease is diagnosed by retina imaging technique based on scanning optical system, so the scanning of eye requires optical system characterized by great ability of anti-moving and optical aberration correction. The adaptive optics possesses high level of adaptability and is available for real time imaging, which meets the requirement of medical retina detection with accurate images. Now the Scanning Laser Ophthalmoscope and the Optical Coherence Tomography are widely used, which are the core techniques in the area of medical retina detection. Based on the above techniques, in China, a few adaptive optics systems used for eye medical scanning have been designed by some researchers from The Institute of Optics And Electronics of CAS(The Chinese Academy of Sciences); some foreign research institutions have adopted other methods to eliminate the interference of eye moving and optical aberration; there are many relevant patents at home and abroad. In this paper, the principles and relevant technique details of the Scanning Laser Ophthalmoscope and the Optical Coherence Tomography are described. And the recent development and progress of adaptive optics in the field of eye retina imaging are analyzed and summarized.
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