Implementation of arbitrary real-valued correlation filters for the shadow-casting incoherent correlator

Active contour segmentation by use of a multichannel incoherent optical correlator

We describe an optoelectronic incoherent multichannel processor that is able to segment an object in a real image. The process is based on an active contour algorithm that has been transposed to optical signal processing to accelerate image processing. This implementation requires exact-valued correlations and thus opens attractive perspectives in terms of optical analog computation. Furthermore, this optical multichannel processor setup encourages incoherent processing with high-resolution images.

Analysis and evaluations of logical instructions called in parallel digital optical operations based on optical array logic

The authors have analysed and evaluated a two-dimensional instruction set of parallel operation based on optical array logic (OAL), which is a digital optical computing paradigm, to clarify efficient composition of an optical computing system based on OAL. To evaluate parallel operation based on OAL, the author have introduced new indices and evaluated a logical instruction set of various parallel operations with the indices, so that a guideline for composing a simple and efficient OAL computing system is clarified. Also, the authors have proposed the reduced operation kernel set correlation technique to perform parallel operations more efficiently by a simple OAL computing system. It has been clarified that the technique can reduce the required hardware necessary for an OAL computing system for efficient general-purpose processing.

Fully complex synthetic discriminant functions written onto phase-only modulators

Synthetic discriminant functions (SDF's) are an effective tool for pattern-recognition applications. However, their experimental implementation is difficult because of the difficulty in writing full complex modulation functions onto spatial light modulators (SLM's) with restricted coding domains. Iterative methods are required for the implementation of SDF filters in real SLM's. A great deal of experimental research has been done with phase-only filters because they can be successfully implemented with liquid-crystal SLM's. We have recently introduced a technique for encoding arbitrary amplitude information onto the phase-only filter, thus allowing us to encode an arbitrary complex function onto a phase-only SLM. We apply this technique to the generation of arbitrary complex SDF filters, thus avoiding the necessity of iterative algorithms. We examine the discrimination capabilities of fully complex SDF filters designed with different parameters and constraints. Experimental results obtained with liquid-crystal SLM's are included.

Spatial-domain implementation of optimal multicriteria correlation filters

We show that optimal regions of support for correlation filters in the frequency domain can be approximated by relatively small convolution kernels in the spatial domain. We present an optimal approach for generating regions of support, as well as a fast nonoptimal approach for conventional optical correlators. Because the convolution kernels are similar to low-pass filters, the resulting input image to a correlator is always positive valued. We show that the performance of the convolution-based approach is comparable with the optimal frequency-domain approach. An important advantage of our method is that it can be implemented on low-cost arithmetic frame grabbers that can perform convolution with small kernels in real time. In addition, our method can be used in conjunction with a filter spatial light modulator that cannot produce a zero state.