Variable field-of-view visible and near-infrared polarization compound-eye endoscope.

A multi-functional compound-eye endoscope enabling variable field-of-view and polarization imaging as well as extremely deep focus is presented, which is based on a compact compound-eye camera called TOMBO (thin observation module by bound optics). Fixed and movable mirrors are introduced to control the field of view. Metal-wire-grid polarizer thin film applicable to both of visible and near-infrared lights is attached to the lenses in TOMBO and light sources. Control of the field-of-view, polarization and wavelength of the illumination realizes several observation modes such as three-dimensional shape measurement, wide field-of-view, and close-up observation of the superficial tissues and structures beneath the skin.

Wavelength-multiplexing diffractive phase elements: design, fabrication, and performance evaluation.

We report on the wavelength-multiplexing diffractive phase element (WMDPE) capable of generating independent spot patterns for different wavelengths. The iterative method proposed by Bengtsson [Appl. Opt. 37, 1998] for designing a kinoform that produces different patterns for two wavelengths is extended to the WMDPE for multiple wavelengths (more than two wavelengths). Effectiveness of the design algorithm is verified by design and computer simulations on the WMDPE's for four and nine wavelengths. The WMDPE for three wavelengths (441.6, 543.5, and 633 nm) is designed with five phase levels and is fabricated by electron-beam lithography. We observed that the individual spot patterns are reconstructed for the design wavelengths correctly. Performance of the WMDPE is evaluated by computer simulations on the uniformity error, the light efficiency, and the contrast. On the basis of the results, the characteristics of the WMDPE's are discussed in terms of various conditions of fabrication and usage.

Optoelectronic parallel-matching architecture: architecture description, performance estimation, and prototype demonstration.

We propose an optoelectronic parallel-matching architecture (PMA) that provides powerful processing capabilities in global processing compared with conventional parallel-computing architectures. The PMA is composed of a global processor called a parallel-matching (PM) module and multiple processing elements (PE's). The PM module is implemented by a large-fan-out free-space optical interconnection and a PM smart-pixel array (PM-SPA). In the proposed architecture, by means of the PM module each PE can monitor the other PE's by use of several kinds of global data matching as well as interprocessor communication. Theoretical evaluation of the performance shows that the proposed PMA provides tremendous improvement in global processing. A prototype demonstrator of the PM module is constructed on the basis of state-of-the-art optoelectronic devices and a diffractive optical element. The prototype is assumed for use in a multiple-processor system composed of 4 x 4 PE's that are completely connected through bit-serial optical communication channels. The PM-SPA is emulated by a complex programmable device and a complementary metal-oxide semiconductor photodetector array. On the prototype demonstrator the fundamental operations of the PM module were verified at 15 MHz.

Thin Observation Module by Bound Optics (TOMBO): Concept and Experimental Verification.

A compact image-capturing system called TOMBO (an acronym for thin observation module by bound optics) is presented in which the compound-eye imaging system is utilized to achieve a thin optical configuration. The captured multiple images are processed to retrieve the image of the target object. For image retrieval, two kinds of processing method are considered: image sampling and backprojection. Computer simulations and preliminary experiments were executed on an evaluation system to verify the principles of the system and to clarify the issues related to its implementation.

Optical manipulation of microscopic objects by means of vertical-cavity surface-emitting laser array sources.

We report on experimental verification of optical trapping using multiple beams generated by a vertical-cavity surface-emitting laser (VCSEL) array. Control of the spatial and temporal emission of a VCSEL array provides flexibility for manipulation of microscopic objects with compact hardware. Simultaneous capture of multiple objects and translation of an object without mechanical movement are demonstrated by an experimental system equipped with 8 x 8 VCSEL array sources. Features and applicability of the method are also discussed.

Two-Dimensional Image Transmission Based on the Ultrafast Optical Data Format Conversion between a Temporal Signal and a Two-Dimensional Spatial Signal.

We have experimentally demonstrated a two-dimensional (2-D) image transmission based on the ultrafast optical data format conversion between a temporal signal and a spatial signal with an ultrashort optical pulse. In the proposed system we adopt a spectral holography technique to transmit a one-dimensional (1-D) spatial signal and use a spatial-domain time-frequency transform to realize a transform between 1-D and 2-D spatial signals. By use of these techniques, a low-optical-loss transmission system can be constructed. To demonstrate a 2-D image transmission with this technique, we achieved experimentally transmission of the alphabet letter T as a 3 x 3 pixel 2-D spatial image.

Stream cipher based on pseudorandom number generation with optical affine transformation.

We propose a new, to our knowledge, stream cipher technique for two-dimensional (2-D) image data that can be implemented by iterative optical transformation. The stream cipher uses a pseudorandom number generator (PRNG) to generate a pseudorandom bit sequence. The proposed method for the PRNG is composed of the iterative operation of 2-D affine transformation achieved by optical components and by modulo-n addition of the transformed images. We expect efficient execution of the method by optical parallel processing. We verify the performance of the proposed method in terms of security strength and clarify problems on optical implementation by the optical fractal synthesizer.

Direct control of fractal pattern generation on an optical fractal synthesizer.

We propose a method for direct control of position, rotation, and scaling of fractal patterns generated on an optical fractal synthesizer. In this method we introduce an iterated-function-system mother function to produce control parameters for arbitrary fractal patterns. We implemented the method experimentally and verified the effectiveness of the method.

String data alignment by a spatial coding and moirA technique.

A method for string alignment is presented in which a moiré technique is applied to one-dimensional spatial encoding patterns. String alignment, an essential operation in genome analysis, evaluates local similarity between sequences of bases or amino acids. The method uses a simple procedure to provide matching results for not only the same locus but also neighboring loci. Experimental verification shows the effectiveness of the proposed method.

Discrete correlation processor as a building core of a digital optical computing system: architecture and optoelectronic embodiment.

In this paper we present a general-purpose discrete correlation processor (DCP) expected to be the building core block of a digital optical computing system. The DCP-1 is embodied by optoelectronic devices such as a VCSEL and a complementary metal-oxide silicon photodetector. The application targets of the DCP-1 are optical interconnection and various types of digital optical computing. It is expected that digital optical computing techniques coupled with the optoelectronic technology will provide large capability and flexibility in information processing. Introduction of a processing scheme of optical array logic enlarges the applicable field of the DCP-1 as well as its processing capability. With the experimental DCP-1 a bit error rate smaller than 10(-9) was obtained for A . B? operation under a 500-kHz clock rate.

Optical computing: introduction by the feature editors.

This feature issue of Applied Optics: Information Processing contains 19 papers on Optical Computing. Many of these papers are expanded versions of presentations given at the Optical Society of America's Sixth Topical Meeting on Optical Computing held in Salt Lake City, Utah, in March 1995. This introduction provides a brief historical account of the series of optical computing meetings and a brief review of the papers contained in this special issue.

Optical implementation of visible gray-image morphology with the visual-area-coding technique.

We present a novel scheme of visible gray-image morphology with the visual-area-coding technique (VACT). The VACT is a technique of digitized analog-optical computing in which data are converted into visible coded patterns and processed with the visible form. Because the achievable operations in the VACT are identical to those of mathematical morphology, mathematical morphology is adapted to gray-image morphology with the VACT. Computer simulation and optical experiments of the several operations in mathematical morphology verify the correctness of the proposed technique. The processing capacity of the proposed method is estimated in terms of the space-bandwidth product.

High-accuracy optical computing based on interval arithmetic and the fixed-point theorem.

A method for high-accuracy analog optical computing based on interval arithmetic and the fixed-point theorem is considered. Two-variable simultaneous equations are studied to investigate the proposed method. An optical implementation is considered by the use of spatial coding of intervals, affine transformation, and image magnification. Computational simulation verifies the principle of the method.

Visual-area coding technique (VACT): optical parallel implementation of fuzzy logic and its visualization with the digital-halftoning process.

A novel technique, the visual-area coding technique (VACT), for the optical implementation of fuzzy logic with the capability of visualization of the results is presented. This technique is based on the microfont method and is considered to be an instance of digitized analog optical computing. Huge amounts of data an be processed in fuzzy logic with the VACT. In addition, real-time visualization of the processed result can be accomplished.

Reflective block optics for packaging of optical computing systems.

A new optical packaging technique, which we call reflective block optics, for optical computing systems is proposed and demonstrated experimentally. This technique is based on solid optics, which is advantageous with respect to stability, reliability, and alignability. Reflective lenses are used to attain high lens power, compactness, and a large space-bandwidth product. Glass blocks, cube beam splitters, and reflective optical elements are combined to form optical blocks. We can construct several optical systems by assembling the optical blocks.

Extended coding for optical array logic.

We present extended coding for optical array logic (OAL) to avoid the marginal effect. The marginal effect is defined as an effect caused by the finite size of the image region, and it is a problem in massively parallel processing by OAL. OAL is a paradigm of optical computing suitable for optical implementation utilizing image coding and discrete correlation. To avoid the marginal effect in the context of OAL, we propose a new coding rule and consider possible operations with this coding. With extended coding, binary data can be identified from background with the same number of pixels as that used in the original OAL. Simulation results of the operations verify the correctness of the proposed technique.

Optical fractal synthesizer: concept and experimental verification.

An application of optical parallel processing in the generation of fractal images is presented. Iterated function systems [M. Barnsley, Fractals Everywhere (Academic, Boston, Mass., 1988), Chap. 3] are the basis of the operation, which can be easily implemented with optical techniques. An optical fractal synthesizer is considered to compute iterated function systems effectively with the advantages of optical processing in data continuity as well as parallelism. As an instance of the optical fractal synthesizer, an experimental system consisting of two optical subsystems for affine transformation and a TV-feedback line is constructed. Several experimental results verify the principle and show the processing capability of the optical fractal synthesizer.

Database management using optical array logic.

Database management is considered as an application of optical array logic. To generalize the problem, a systematic procedure for massively parallel data processing that consists of pattern expansion, template matching, magnitude comparison, and sorting is presented. With this procedure, a method for implementing basic operations for relational database models is developed. Basic operations are described by parallel programs in optical array logic. Developed programs are evaluated by their performance. To improve the performance, the development of specialized optical functional modules is needed.

Iterative processing on a hybrid optical parallel array logic system with a selectable coherent correlator.

A new version of an experimental system of an optoelectronic hybrid optical parallel array logic system is constructed. The experimental system is composed of a two-dimensional correlator with selectable holographic filters and parallel electronic circuits. The system can process images consisting of 3 × 3 pixels at a time. Several types of processing are achieved both without and with dynamic selection of the holographic filters. On the experimental system, parallel operations of several logical functions and data transmission are demonstrated. Processing rates of iterative operation without and with filter selection are 278 and 143 frames/s, respectively.

Gray-image processing using optical array logic.

A method for digital image processing that uses optical array logic (OAL) is presented. Parallel thresholding and digital filtering are demonstrated. OAL is a promising computational paradigm for digital optical computing based on parallel neighborhood operations for two two-dimensional binary images. In the proposed method, virtual processing elements are assumed on an image plane and a gray pixel in an original gray image is stored in each processing element. Efficient gray-image processing can be achieved by data manipulation in the virtual processing elements and in the data communication among them by using OAL. Several simulation results are presented. Finally, hardware requirements for the developed algorithms and their capabilities are discussed.