I. Glaser

Lenslet array processors

By combining a lenslet array with masks it is possible to obtain a noncoherent optical processor capable of computing in parallel generalized 2-D discrete linear transformations. We present here an analysis of such lenslet array processors (LAP). The effect of several errors, including optical aberrations, diffraction, vignetting, and geometrical and mask errors, are calculated, and guidelines to optical design of LAP are derived. Using these results, both ultimate and practical performances of LAP are compared with those of competing techniques.

Pattern recognition using incoherent OTF synthesis and edge enhancement.

This paper describes a system for pattern recognition using an incoherent-optical correlator. The system uses optical transfer function synthesis to perform correlations with an edge-enhanced image of the object or pattern being sought. The resulting correlations are free of bias and show good discrimination between objects. In addition, the difficult or time-consuming computations are performed before the operation of the system; this reduces the amount of postprocessing by computer and should allow real-time operation at video rates.

Incoherent optical two-dimensional Fourier transform using the chirp-z algorithm

An incoherent optical method for computing two-dimensional complex-valued Fourier transforms is described. It is based on implementing the two-dimensional chirp-z algorithm with incoherent optical convolutions and indirect representation of complex-valued functions.

Optical interconnections for digital processing: a noncoherent method

We describe the use of a lenslet-array-based device for interconnections in optical digital computing systems. This new device, the digital lenslet array processor, operates in polychromatic and spatially incoherent light, so it can use a wide spectrum of electro-optical light sources. An experimental example is presented.

Separation of in-plane and out-of-plane motions in holographic interferometry.

A technique for separating the in-plane and out-of-plane motions of a tested object in hologram interferometry is described. In this technique, the object is illuminated with two symmetrically oriented beams, and an image plane hologram is recorded in photoconductor-thermoplastic devices which can be developed in situ and in virtually real time. Then the hologram is read out with the object waves only, thereby reconstructing the reference beam. If the object is moved or deformed during readout, fringes denoting equal in-plane motion appear as long as the motion is less than the speckle size. The exact arrangement is presented along with experimental results, which are compared with conventional holographic interferometry results.

Holographic Nondestructive Evaluation With On-Line Acquisition And Processing

A holographic non-destructive evaluation (HNDE) system with on-line acquisition and processing of real-time interferograms is presented. The system comprises photoconductor-thermoplastic recording materials, an image acquisiton system based on a photodiode-array line scanner. A microprocessor for controlling acquisition and other system functions and a link to a large computer. The system is capable of fringe detection down to an accuracy of 1/100th of a fringe. Applications for the non-destructive evaluation of an actual industrial specimen, as well as mapping the derivatives of deformation of a 2-D object are presented.

Registration fiducials for automated alignment with optical processing

Since automated assembly, as well as automated inspection and sorting, usually require prealigned work-pieces, the availability of rapid and simple automatic alignment is a prerequisite to widespread acceptance of such systems. Coherent optical correlators potentially offer the necessary speed, but they have required mechanically coupled image rotation prisms and spatial light modulators and are, therefore, quite complicated and cumbersome. We describe here an alternative approach in which circularly symmetric fiducials are incorporated into the object itself and detected with an incoherent optical correlator. With incoherent correlators there is no need for spatial light modulators; also, the fiducials are so chosen that the correlation is not rotation sensitive. Since several (typically three) identical fiducials are used, their location can provide sufficient information on the object orientation. The approach was tested in the laboratory, and some experimental examples are included.

COMPACT LENSLET-ARRAY-BASED HOLOGRAPHIC CORRELATOR/CONVOLVER

Although electronic systems continue to shrink in size, optical processors, particularly correlators/convolvers, remain relatively bulky. Here a compact holographic correlator/convolver, based on the use of multiple lenslet arrays, is presented. This compact lenslet-array holographic correlator/convolver approach offers most of the advantages of conventional optical correlators, including fully parallel high-speed operation, yet its physical size is comparable with that of monolithic optoelectronic units such as VLSI spatial light modulators and CCDs. Thus hybrid optoelectronic systems based on the lenslet-array holographic correlator/convolver (pattern recognition, optically interconnected computers, artificial neural networks, etc.) can be both compact and fast.

Orthogonal in-plane and out-of-plane fringe maps in holographic interferometry

A new technique that combines holographic and speckle interferometry in one recording is described. The technique produces two different fringe maps, which correspond to the in-plane and out-of-plane deformation separately. Experimental results demonstrating the feasibility of the technique to determine complex deformations are presented.

Digital Incoherent Optical Interconnections

This presentation deals with the use of an incoherent optical processing device for optical interconnections in digital systems. Our device is based on a lenslet-array/mask assembly. The lenslet array creates multiple images of the input. The mask controls the interconnections pattern by blocking parts of these images. The device can operate with polychromatic and spatially incoherent light, so it can use many electro-optical light sources. Device limitations and capabilities are analyzed. This analysis shows that up to 107 elements may be connected by such devices. A demonstration of a simple digital circuit is presented.