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The challenge in rendering integral images is to use as much information preserved by the light field as possible to reconstruct a captured scene in a three-dimensional way. We propose a rendering algorithm based on the projection of rays through a detailed simulation of the optical path, considering all the physical properties and locations of the optical elements. The rendered images contain information about the correct size of imaged objects without the need to calibrate the imaging device. Additionally, aberrations of the optical system may be corrected, depending on the setup of the integral imaging device. We show simulation data that illustrates the aberration correction ability and experimental data from our plenoptic camera, which illustrates the capability of our proposed algorithm to measure size and distance. We believe this rendering procedure will be useful in the future for three-dimensional ophthalmic imaging of the human retina.

Two new optical free-space collinear cross-over interconnect schemes are suggested. The first optical implementation uses mirrors and beam splitters, while the second uses a Fresnel zone plate and lens combination. Some proof-of-principle experimental results are also presented.

Because of the lack of fast, accurate, and large dynamic range analog-to-digital converters (ADCs), optical implementation of the digital multiplication through analog convolution (DMAC) algorithm yields a slow digital multiplier. By replacing both the optical adder and ADC arrays by an optical combinatorial logic counter array, a new optical fast digital multiplication method is proposed. Compared to the existing optical DMAC scheme, the new method promises both higher processing speed and accuracy. A comparison of this and some of the other optical and electronic fast digital multiplication schemes is also presented.

A compact white light optical tracking novelty filter is demonstrated. Based on the use of two inexpensive liquid crystal televisions, a filtered and collimated white light source, digital delay, and video recorder, this portable white light device performs two major image comparison operations, a real time image subtraction and novelty tracking operations. Some preliminary experimental results are presented.

Optical register transfer microoperations are proposed. Based on an optical holographic associative symbolic substitution, a hybrid optical word-parallel bit-serial register transfer processor architecture is described. Preliminary experimental results are included.

The long-standing problem of the superresolving reconstruction (restoration) of an object of known finite spatial extent from a noisy linearly degraded image is considered. The resolution of two-point sources (objects) spaced less than one Rayleigh distance apart is an ill-posed problem. To determine a superresolving inverse of an ill-conditioned linear degradation operator with a known set of input/output training signals, a linear associative memory (LAM) technique is employed. By limiting the set of reconstructable signals, an exceptionally robust inverse filter has been obtained. This filter is based on a new constrained LAM matrix operator technique. Superresolving restoration of 1-D and 2-D two-point sources as well as some typical edge-type signals in the presence of considerable measurement noise is demonstrated.

After a short introduction, a brief overview of the research papers contained in this special issue is presented.

There are many pattern recognition problems where the pattern's structural information is important. In these problems, a syntactic method of pattern recognition is of value. In this paper, both parallel syntactic pattern recognition algorithm and optical architecture implementation approaches are described. In particular, the applications of syntactic pattern recognition algorithm to shape classification are illustrated. A number of parallel optical syntactic pattern coding methods, a structural matched filter and associative memory filter, and an optical symbolic substitution syntactic parser are discussed.

One-dimensional signals have complementary attributes, their space and spatial frequency properties. Recently, another signal representation was introduced in optics, the Wigner distribution (WD) function, which allows the simultaneous display of the two attributes of a 1-D signal. In this paper optical implementation of a generalized space–spatial frequency (GSF) function is discussed. Special cases of the GSF representations are the WD, the radar ambiguity function (AF), the energy distribution function, the various pseudo-WD functions, the spectrogram, the local frequency and the local Doppler frequency spectrum. The GSF representation allows the simultaneous filtering of both the spatial and the spatial frequency content of a 1-D signal. The 2-D filtering of a 1-D signal allows sidelobe reduction of the WD and AF of quasi-periodic 1-D signals, display of the instantaneous spatial frequency content of a 1-D signal, space–spatial frequency excision of a desired portion of a 1-D signal as well as the usual matched filter detection. Experimental results using coherent space-integrating techniques for the realization of different GSF are presented.

Holographic interferometry measurements have been performed on high-speed, high-temperature gas flows with a laser output tuned near a resonant sodium transition. The technique allows the detection and quantification of the sodium concentration in the flow. By controlling the laser detuning and seeded sodium concentration, we performed flow visualization in low-density flows that are not normally detectable with standard interferometry. The technique was also successfully used to estimate the temperature in the boundary layer of the flow over a flat plate.

This paper reports on an investigation of the chemical stability of the common laser-induced fluorescence (LIF) tracers acetone, diethylketone, and toluene. Stability is analyzed using linear Raman spectroscopy inside a heated pressure cell with optical access, which is used for the LIF calibration of these tracers. The measurements examine the influence of temperature, pressure, and residence time on tracer oxidation, which occurs without a rise in temperature or pressure inside the cell, highlighting the need for optical detection. A comparison between the three different tracers shows large differences, with diethylketone having the lowest and toluene by far the highest stability. An analysis of the sensitivity of the measurement shows that the detection limit of the oxidized tracer is well below 3% molar fraction, which is typical for LIF applications in combustion devices such as internal combustion (IC) engines. Furthermore, the effect on the LIF signal intensity is examined in an isothermal turbulent mixing study.

A Sagnac interferometer (SI) has been constructed with a mode-locked Nd3+:YAG laser as its source. The advantages in pulsed laser interferometry of using a SI over a Mach-Zehnder interferometer are analyzed. The autostability property of SI is experimentally demonstrated. Applications of an SI to light-induced index of refraction change measurements and to the picosecond optical switching are discussed. Experimental results are presented.

The Hough transform (HT) is an efficient shape detector that maps straight lines into a two-parameter feature space. Recently it has been pointed out that the forward Radon transform (FRT), well known from the theory of computed tomography, and the HT are equivalent for binary images. In this paper, analog coherent optical implementation of the FRT is discussed. The FRT will not only be of use in implementing the HT shape descriptors but also act as a coherent optical preprocessor for the implementation of multidimensional convolution, correlation, and spectral analysis using 1-D acoustooptical signal processing devices. Several different coherent optical FRT architectures are presented. Experimental results using conventional coherent Fourier transform configuration are given. The relationship between the coherent optical implementation of the FRT and the inverse Radon transform, an important tool in computed tomography, is also detailed.

Two different approaches to decision aids are explored. In one, forced binary decisions are made. In the other, a set of a posteriori probabilities is calculated. In both cases fast inferences can be calculated by optical matrix operations.

Two ternary, an ordinary ternary (OT) and a binary balance ternary (BT), number representations to be used for optical computing are discussed. An unsigned OT number is represented by a string of symbols (0, 1, 2), while for the BT, the three logic symbols take on the set (−1, 0, +1). The BT symbols can represent a signed number. Using a particular binary encoding method, the three ternary symbols are converted to a pair of binary symbols. The binary coded ternary (BCT) representation has two advantages. First, it allows use of the well-developed binary optical components. Second, compared with other optical multiple-valued number encoding schemes, it reduces the number of input–output channels and thus is able to conserve the optical space–bandwidth product. As an example for arithmetic operations, BCT full addition algorithms are given. As examples for multiple-valued logic computing, BCT Post, Webb, and residue logic elements are discussed. Using the two-port Sagnac interferometric switches, optical implementations of various BCT arithmetic and logic operations are described.

Superresolving image restoration (SIR) in the presence of noise is considered. Few SIR algorithms have demonstrated the ability to resolve two point sources spaced one-half of the Rayleigh distance apart. In this paper, it is shown that the SIR of a two-point noncoherent source spaced one-tenth of a Rayleigh distance apart is possible. The method presented uses optimal data fitting techniques based on the methods of linear programming. For noisy images, a combination of linear eigenvalue prefiltering and optimal data fitting is used. It is also shown that for a diffraction-limited image of two-point sources spaced one-half of the Rayleigh distance apart, where the input is contaminated with significant noise, SIR is achievable. These results have important implications in atmospheric physics, geophysics, radio astronomy, medical diagnostics, and digital bandwidth-compression applications where the deconvolution of noisy bandwidth-compressed images is one of the fundamental limitations. The techniques described are specifically designed for impulsive-type images.

In this paper, two optical image skeletonization algorithms are introduced. In both algorithms, the matching between an input and a set of precalculated parallel check patterns is performed. Based on the matching results, multistage symbolic substitution operations are incorporated. For an optical implementation, an optical hologram-based content-addressable memory technique is employed. The corresponding optical architecture as well as character skeletonization examples are presented.

Conjugaison de phase en optique non lineaire applique aux problemes de traitement d'image et de traitement optique du signal en temps reel

An optical isochronous array processing method is proposed. An optical isochronous array processor (OIAP) is a local regularly interconnected processing network that employs an array of identical optical processing elements. In an OIAP, incoming isochronous data are parallel processed in a fashion much like a propagating electromagnetic wavefront. For the various applications, the OIAP processing elements and their interconnections can be different. In this paper, various all-optical OIAP elements are considered. Applications ranging from optical binary number multiplication preprocessing to optical matrix algebra as well as to optical residue arithmetic are presented.