Optical encryption system that uses phase conjugation in a photorefractive crystal

We implement an optical encryption system based on double-random phase encoding of the data at the input and the Fourier planes. In our method we decrypt the image by generating a conjugate of the encrypted image through phase conjugation in a photorefractive crystal. The use of phase conjugation results in near-diffraction-limited imaging. Also, the key that is used during encryption can also be used for decrypting the data, thereby alleviating the need for using a conjugate of the key. The effect of a finite space-bandwidth product of the random phase mask on the encryption system's performance is discussed. A theoretical analysis is given of the sensitivity of the system to misalignment errors of a Fourier plane random phase mask.     

Recoded and nonrecoded trinary signed-digit adders and multipliers with redundant-bit representations

Highly-efficient two-step recoded and one-step nonrecoded trinary signed-digit (TSD) carry-free adders-subtracters are presented on the basis of redundant-bit representation for the operands' digits. It has been shown that only 24 (30) minterms are needed to implement the two-step recoded (the one-step nonrecoded) TSD addition for any operand length. Optical implementation of the proposed arithmetic can be carried out by use of correlation- or matrix-multiplication-based schemes, saving 50% of the system memory. Furthermore, we present four different multiplication designs based on our proposed recoded and nonrecoded TSD adders. Our multiplication designs require a small number of reduced minterms to generate the multiplication partial products. Finally, a recently proposed pipelined iterative-tree algorithm can be used in the TSD adders-multipliers; consequently, efficient use of all available adders can be made.     

Two-wavelength interferometry that uses a fourier-transform method

Two-wavelength interferometry that is based on a Fourier-transform method has been investigated. A phase profile at a synthetic wavelength has been measured from a two-wavelength interferogram with two spatial carrier frequencies. A phase error caused by the difference between modulation intensities at two wavelengths has been theoretically and numerically analyzed. A phase map without the error can be obtained from a power-spectrum adjustment in the two-wavelength interferogram.     

Novelty filter that uses a bacteriorhodopsin film

We propose a new novelty optical filter that uses a bacteriorhodopsin film. This filter is based on the time-dependent nonlinear diffraction efficiency of real-time holograms recorded in the film. As soon as the signal beam carrying a pattern is diffracted by the polarization hologram recorded in the bacteriorhodopsin film, it begins to erase the hologram and suppresses the diffraction of the beam at the position of the stationary part of the pattern. This filter enhances only leading edges of moving patterns. In this system undesired scattered light, which is orthogonally polarized to the diffracted beam, is discriminated by a polarizer.     

Optoelectronic Systems Based on InGaAs- Complementary-Metal-Oxide-Semiconductor Smart-Pixel Arrays and Free-Space Optical Interconnects

Free-space optical interconnects have been identified as a potentially important technology for future massively parallel-computing systems. The development of optoelectronic smart pixels based on InGaAs/AlGaAs multiple-quantum-well modulators and detectors flip-chip solder-bump bonded onto complementary-metal-oxide-semiconductor (CMOS) circuits and the design and construction of an experimental processor in which the devices are linked by free-space optical interconnects are described. For demonstrating the capabilities of the technology, a parallel data-sorting system has been identified as an effective demonstrator. By use of Batcher's bitonic sorting algorithm and exploitation of a perfect-shuffle optical interconnection, the system has the potential to perform a full sort on 1024, 16-bit words in less than 16 mus. We describe the design, testing, and characterization of the smart-pixel devices and free-space optical components. InGaAs-CMOS smart-pixel, chip-to-chip communication has been demonstrated at 50 Mbits/s. It is shown that the initial system specifications can be met by the component technologies.     

Optical associative memory with bipolar edge-enhanced learning that uses a binary spatial light modulator and a BaTiO(3) crystal

An optical associative memory with bipolar edge-enhanced feature learning that uses a ferroelectric liquid-crystal spatial light modulator and a barium titanate crystal is presented. During the learning procedure the bipolar edge-enhanced versions of the patterns are employed, which enable the associative memory to have a high discrimination capability. Experimental results and computer simulations are given.     

The Electrical and Optical Properties of Organometal Halide Perovskites Relevant to Optoelectronic Performance

Organometal halide perovskites are under intense study for use in optoelectronics. Methylammonium and formamidinium lead iodide show impressive performance as photovoltaic materials; a premise that has spurred investigations into light‐emitting devices and photodetectors. Herein, the optical and electrical material properties of organometal halide perovskites are reviewed. An overview is given on how the material composition and morphology are tied to these properties, and how these properties ultimately affect device performance. Material attributes and techniques used to estimate them are analyzed for different perovskite materials, with a particular focus on the bandgap, mobility, diffusion length, carrier lifetime, and trap‐state density.     

Secure optical storage that uses fully phase encryption

A secure holographic memory system that uses fully phase encryption is presented. Two-dimensional arrays of data are phase encoded. Each array is then transformed into a stationary white-noise-like pattern by use of a random-phase mask located at the input plane and another at the Fourier plane. This encrypted information is then stored holographically in a photorefractive LiNbO(3):Fe crystal. The original phase-encoded data can be recovered, by use of the two random-phase masks, with a phase-conjugate readout beam. This phase information can then be converted back to intensity information with an interferometer. Recording multiple images by use of angular multiplexing is demonstrated. The influence of a limited system bandwidth on the quality of reconstructed data is evaluated numerically. These computer simulation results show that a fully phase-based encryption system generally performs better than an amplitude-based encryption system when the system bandwidth is limited by a moderate amount.     

Prism fingerprint sensor that uses a holographic optical element

A prism fingerprint sensor is described that uses a holographic grating glued to a right-angled prism. A light source normally illuminates the hypotenuse side of the prism with the finger pressed against the grating. The ridges and valleys of the finger are sensed on the basis of the principle of total internal reflection. The grating is used essentially to correct the distortion usually present with prism sensors. The quality of the fingerprint is very good: the pores on the ridges can be seen.     

UV Microstereolithography System that uses Spatial Light Modulator Technology

A new stereophotolithography technique utilizing a spatial light modulator (SLM) to create three-dimensional components with a planar, layer-by-layer process of exposure is described. With this procedure it is possible to build components with dimensions in the range of 50 mum-50 mm and feature sizes as small as 5 mum with a resolution of 1 mum. A polysilicon thin-film twisted nematic SVGA SLM is used as the dynamic photolithographic mask. The system consists of eight elements: a UV laser light source, an optical shutter, beam-conditioning optics, a SLM, a multielement reduction lens system, a high-resolution translation stage, a control system, and a computer-aided-design system. Each of these system components is briefly described. In addition, the optical characteristics of commercially available UV curable resins are investigated with nondegenerate four-wave mixing. Holographic gratings were written at a wavelength of 351.1 nm and read at 632.8 nm to compare the reactivity, curing speed, shrinkage, and resolution of the resins. These experiments were carried out to prove the suitability of these photopolymerization systems for microstereolithography.     

Corneal surface reconstruction algorithm that uses Zernike polynomial representation

We developed an algorithm that directly determines Zernike coefficients for the corneal anterior surface derived from the reflection image of a stimulus with pseudorandom encoding. This algorithm does not need to include calculation of corneal height maps. The numerical performance of the algorithm is good. It has the potential of determining corneal shape with submicrometer accuracy in obtaining Zernike coefficients. When applied to real eye measurements the accuracy of the procedure will be limited by the topographer that is used.     

Compact optical smoke sensor that uses an integrating cylinder

We report a new kind of compact and portable optical smoke sensor that uses an integrating cylinder as the light collector. Theoretical analysis shows that this smoke sensor can have high sensitivity and good linearity because a number of reflected lights participate in the measurement of smoke concentration. A smoke sensor has been constructed, and it has demonstrated improved sensitivity and linearity compared with the conventional direct-beam-based smoke sensor. Good agreement of theoretical and experimental results has been obtained.     

Volume-scanning three-dimensional display that uses an inclined image plane

A novel three-dimensional display based on a volume-scanning method that uses an inclined light-source array and a mirror scanner is proposed. With this technique it is possible to display three-dimensional images that satisfy all factors for human stereoscopic vision. Three-dimensional images of 8 x 8 x 8 pixels, 40 mm x 40 mm x 40 mm in size, with a frame rate of 12.7 Hz were obtained as real images through an experimental system that uses a galvanometer mirror and a LED array.     

Optical Joint of Optoelectronic Radiation Converters with Immersion Light Guides and Calculation of Their Characteristics

In the present work, equations are obtained that establish relationships between the optical characteristics of optoelectronic radiation converters and straight cylindrical immersion light guides with straight faces manufactured from isotropic and anisotropic materials with different refractive indices. Engineering procedures to calculate the schemes of optical joint of pyrometric converters with light guides that improve the metrological characteristics of the immersion light-guide thermometry of radiation are developed.     

High-performance nonscanning Fourier-transform spectrometer that uses a Wollaston prism array

A high-performance nonscanning Fourier-transform spectrometer is reported that is composed mainly of a Wollaston prism array and a two-dimensional photodetector array. It is a substantial improvement over existing Wollaston prism based nonscanning Fourier-transform spectrometers because it offers finer spectral resolution and smaller size. Such spectrometers will find important applications in remote chemical and biological sensing, environmental monitoring, medical diagnosis, etc. Experimental results are consistent with theoretical analyses.     

Viewing-zone enlargement method for sampled hologram that uses high-order diffraction

We demonstrate a method of enlarging the viewing zone for holography that has holograms with a pixel structure. First, aliasing generated by the sampling of a hologram by pixel is described. Next the high-order diffracted beams reproduced from the hologram that contains aliasing are explained. Finally, we show that the viewing zone can be enlarged by combining these high-order reconstructed beams from the hologram with aliasing.     

Phase-shifting real-time holographic interferometry that uses bismuth silicon oxide crystals

A bismuth silicon oxide crystal is used in the diffusion regime as a dynamic recording medium in a real-time holographic interferometer based on anisotropic self-diffraction. This device is connected with an interferogram-analysis method that uses the phase-shifting technique for quantitative measurement of diffusive-reflecting object deformations. In addition to the usual error sources in phase shifting, the temporal interferogram erasure is studied and is found weakly perturbative for the measured phase. It is shown that quantitative measurements are possible for low-intensity object beams (8 μW/cm(2)) and a large observed area. Apractical situation of defect monitoring in a composite structure is presented.     

Tunable microwave filter that uses a high-birefringent fiber and a differential-group-delay element

We propose and experimentally demonstrate a novel and simple photonic microwave notch filter that uses a high-birefringent fiber that gives a fixed differential group delay (DGD), together with a DGD element that gives a tunable DGD. This configuration overcomes the problems of optical coherence interference and chromatic dispersion, which may occur in schemes that use fiber delay lines or fiber gratings. Also presented is a theoretical analysis for the performance of the microwave filter that uses the present configuration. The present scheme provides a continuous tuning capability for changing the notch frequency. Measured notch rejection is greater than 40 dB. This scheme can operate over a wide wavelength range of the optical carrier. There is good agreement between experiment results and theoretical analysis.     

三值全局空间自相关指标及其应用研究

Join-Count统计量是衡量空间自相关的全局指标.针对其用于处理二值名义变量的特性,将Join-Count统计量处理的属性值扩展到了三值变量,推导出了三值变量的邻接计数、邻接计数期望及方差的计算式,采用模拟数据进行了验算,证明所推导的公式是正确可行的,对计算结果的解释是合理的,这对三值Join-Count统计量应用于图像空间统计中的自相关分析有理论意义和实用参考价值.