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In this paper an image authentication scheme is proposed based on double-image encryption and partial phase decryption in nonseparable Fractional Fourier transform domain. Two original images are combined and transformed into the nonseparable fractional Fourier domain. Only part of the phase information of the encrypted result is kept for decryption while the rest part of phase and all the amplitude information are discarded. The two recovered images are hardly recognized by visual inspection but can be authenticated by the nonlinear correlation algorithm. The numerical simulations demonstrate the viability and validity of the proposed image authentication scheme. [ABSTRACT FROM AUTHOR]

In this paper, a new method for optical image encryption based on multi-beams interference principle and vector composition is proposed. In this encryption, the original image is encoded into n −1 phase only masks which are regarded as the keys of the encryption system and a ciphertext according to multi-beams interference principle and vector composition. In decryption process, n beams of parallel incident light illuminate at the phase only masks and the ciphertext, and we can obtain the decrypted image at output plane after Fourier transforms. The security of the proposed method is discussed, finding that no decrypted image can be obtained only when all the keys used are right. Furthermore, the keys can be stored separately resulting in improving the security of encryption system. Computer simulation results are presented to verify the validity of the proposed method. [ABSTRACT FROM AUTHOR]

Abstract: The geometric phase analysis (GPA), an important image-based deformation measurement method, has been used at both micro- and nano-scale. However, when a deformed image has apparent distortion, non-ignorable error in the obtained deformation field could occur by using this method. In this paper, the geometric phase analysis based on the windowed Fourier transform (WFT) is proposed to solve the above-mentioned issue, defined as the WFT–GPA method. In WFT–GPA, instead of the Fourier transform (FT), the WFT is utilized to extract the phase field block by block, and therefore more accurate local phase information can be acquired. The simulation tests, which include detailed discussion of influence factors for measurement accuracy such as window size and image noise, are conducted with digital deformed grids. The results verify that the WFT–GPA method not only keeps all advantages of traditional GPA method, but also owns a better accuracy for deformation measurement. Finally, the WFT–GPA method is applied to measure the machining distortion incurred in soft ultraviolet nanoimprint lithography (UV-NIL) process. The successful measurement shows the feasibility of this method and offers a full-field way for characterizing the replication quality of UV-NIL process. [Copyright &y& Elsevier]

Abstract: A novel numerical simulation method for the shaping of an excimer laser beam by an acoustic grating is proposed. Partially coherent theory and extended Huygens–Fresnel principle are used to analyze the light intensity diffraction pattern. Fast Fourier transform function FFT in the Matlab is used to calculate the numerical integral, which makes the integral operation simple and efficient. It is shown by a numerical simulation that the output intensity distribution is closely related to the coherence width, Raman–Nath comprehensive parameter, diffraction distance and ultrasonic wave frequency. The simulation results show that a flat top beam can be obtained by controlling these parameters. On the other hand, the results are used as an effective analytic tool for the determination of the design parameters of acousto-optic modulator. [Copyright &y& Elsevier]

Abstract: A multiple-image encryption scheme based on the optical wavelet transform (OWT) and the multichannel fractional Fourier transform (MFrFT) is proposed. The scheme can make full use of multi-resolution decomposition of wavelet transform (WT) and multichannel processing of MFrFT. The mentioned properties can achieve the encryption of multi-image and the encryption of single image. When encryption finished, each image gets its own fractional order and independent keys. Analysis of encrypted effects has been completed. Furthermore, the influence of WT type and order are analyzed, and the application and analysis of MFrFT are accomplished as well. Numerical simulation verifies the feasibility of the scheme and shows that the problem of insufficient capacity is better solved, and the flexibility of scheme increases. A simple opto-electronic mixed device to realize the scheme is proposed. [Copyright &y& Elsevier]

Abstract: Based on random fractional Fourier transform (RFrFT), a novel adaptive watermarking algorithm using fractal dimension is proposed. Under fractal dimension, this algorithm is adaptive in the embedding position and the embedding intensity. The robustness and the imperceptibility of the watermarking algorithm are in good balance when block selection, high amplitude selection and amplitude shift keying are employed in this algorithm. Numerical simulation results have demonstrated the effectiveness of the proposed scheme and shown the robustness against attacks of noising, cropping and JPEG compression. [Copyright &y& Elsevier]

Abstract: We propose two approaches to encrypt color images based on interference and virtual optics. In the first method, a color image is first decomposed into three independent channels, i.e., red, green and blue. Each channel of the input image is encrypted into two random phase-only masks based on interference. In the second method, a color image is first converted into an image matrix and a color map, and only the image matrix is encrypted into random-phase masks based on interference. After the phase masks are retrieved, a concept based on virtual optics is further applied to enhance the security level. Numerical simulations are demonstrated to show the feasibility and effectiveness of the proposed methods. [Copyright &y& Elsevier]