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Three typical calibration patterns, including checkerboard, Gaussian point grid, and crossed fringe patterns, are chosen to find a good one for camera calibration. Through computer simulation and camera intrinsic parameter calibration experiment, the crossed sine fringe pattern using fringe analysis method is defined as the one with the best precision. However, the phase information is obtained by Fourier transform (FT), which cannot detect the points located in the edge of the point grid. Thus, an innovative method uses phase shifting in the fringe analysis process is proposed, it can avoid the extraction misplacement in the edge of the point grid by the FT method, and make the crossed sine fringe pattern more usable in camera calibration. The camera extrinsic parameter calibration experiment proves the effectiveness of the recent method. [ABSTRACT FROM AUTHOR]

Based on the two-step phase-shifting interference (PSI) technique in fractional Fourier transform (FRT) domain and random mixed encoding, we present a new scheme for double image encryption. In the proposed scheme, information of each primitive image is recorded in two intensity interference patterns of FRT spectra by PSI technique, from which an encrypted image for each primitive image can be digitally derived. Random mixed encoding is then employed to divide and recombine both encrypted images into a single synthetic encrypted image. During the mixed encoding process, repositioning operations based on shift-variance of FRT are performed on the encrypted images to realize the spatial separation of decoded results in the output plane. By inverse FRT with correct fractional order, any of the primitive images can be easily retrieved directly from the synthetic encoded image with the corresponding phase encoding key. Crosstalk effect due to the overlapping of decoded images is alleviated for their spatial separation. Computer simulation and experimental results are presented to verify the validity and efficiency of our scheme. [ABSTRACT FROM AUTHOR]

The exposure lens is a useful tool for fast and convenient chirpiness detection. An exposure lens is proposed by adopting square-root space mapping within the framework of transformation optics, thereby exposing a portion of the optical axis within the body of a conventional graded index lens at the lens surface, while compressing the input facet. This compression enables the proposed lens to detect higher chirpiness than conventional lenses. The results of numerical simulations verify the enhanced chirpiness detection. The family of exposure lenses provides a complete kit for investigating a wide chirpiness range, which has potential for optics signal processing. [ABSTRACT FROM AUTHOR]

The morphological joint fractional Fourier transform correlator (MJFTC), as a modified nonlinear joint fractional Fourier transform correlator (JFTC), is introduced in this paper. An optoelectronic setup that can implement such a nonlinear JFTC is advised and constructed. We investigate the correlation properties of the MJFTC using computer simulation and optical experiments. Numerical and experimental results show that the MJFTC exhibits remarkable improvement in terms of discriminability and peak sharpness compared with the classic JFTC. Moreover, the MJFTC provides better noise tolerance to the salt-and-pepper noise or normally distributed white additive noise than the JFTC and the other nonlinear processing or fractional-order filtering JFTC. [ABSTRACT FROM AUTHOR]

An optical joint transform correlation-based cryptographic system is a used to feed multiple phase-shifted encryption keys into four parallel channels along with a to-be-encrypted signal in the form of an image. The resulting joint power spectra (JPS) signals are phase-shifted and then combined to yield a modified JPS signal. Inverse Fourier transformation of the modified JPS signal yields the secured encrypted image. For decryption purpose, the received encrypted signal is first Fourier transformed and multiplied by the encryption key used in encryption. The derived signal is then inverse Fourier transformed to generate the output signal. The proposed system offers a nonlinear encryption without the involvement of any complex mathematical operation on the encryption key otherwise required in similar encryption techniques and is invariant to noise. Computer simulation results are presented to show the effectiveness of the proposed scheme with binary, as well as gray images in both noise-free and noisy environment. [ABSTRACT FROM AUTHOR]

We propose a high-speed surface profiler using a modified Fourier transform profilometry (FTP) approach. Our system geometry is different from a conventional profiler in that the fringe-projection lens and the imaging lens are at different heights from a reference plane. FTP computer simulation and experimental data are provided that supports our theoretical development. Our profiler provides a 1σ rms error of about 4 μm for an integrated circuit chip sample in an area of 14 mm × 6.5 mm with a 0.13 second data acquisition time. It is shown that our theoretical derivation is suitable for a micrometer scale object measurement. [ABSTRACT FROM AUTHOR]

The joint transform correlator (JTC) is a classical optical architecture, recently associated with interesting applications in optical security. In addition, multiplexing is a tactic associated with optical encrypting mechanisms that provide security for multiple users. However, experimental constraints arise when we intend to reproduce a diffuser shifting multiplexing option. This is due to the invariance to lateral shifts under a JTC setup. To overcome this problem, we propose a setup modification that allows its use under a multiplexing approach. Instead of placing the encrypting mask in contact with the input JTC plane, we use the actual optical Fourier transform of a diffuser projected over the entrance plane of the JTC. We present a theoretical explanation, along with computer simulations and experimental results, that support our proposal. [ABSTRACT FROM AUTHOR]