B. Keith Jenkins

First-harmonic diffusion model for holographic grating formation in photopolymers

We present a model with which to describe and predict the formation of gratings during exposure in holographic photopolymers. This model combines the action of photopolymerization and of free-monomer diffusion during holographic exposures. We consider the free-monomer density to be spatially varying, during exposure, with a single first-harmonic term out of phase with respect to the intensity interference pattern. Examples of behavior predicted by the model include the variation of the saturation diffraction efficiency with recording exposure intensity and with beam intensity modulation, as well as the variation of recorded grating modulation during dark diffusion transient. The model is supported by experiments carried out by exposure of DuPont HRF-150-38 holographic photopolymers.

A Neural Network Model for Pitch Perception

In this paper we will examine the human ear-and cochlear mechanics in particular-in order to better understand the signals sent to the brain. We will also discuss some theories of pitch perception. We propose a neural network model to examine the sensitivity discrepancy in general and pitch perception in particular, with emphasis on the neural representation of pitch perception. The resulting model concentrates on the preprocessing of the auditory stimulus, reducing it to a simple pattern classification problem. Western music defines an octave as an interval that represents a frequency ratio of 2: 1. The most commonly used scale is the dodecaphonic (twelvetone), well-tempered scale. It divides the octave into 12 evenly spaced halftones, 6 percent (12VN2) apart in frequency. Frequency detection is performed by an array of sensory hairs in the cochlea in the ear. The characteristic frequency of these hairs depends on their location along the cochlea and increases monotonically along the array. Each hair behaves as a bandpass filter with a bandwidth of approximately 10 percent of the characteristic frequency. The human auditory system is sensitive to as little as .3 percent to 1.5 percent changes at certain frequencies (Evans 1982). This sensitivity discrepancy between the human auditory system and its components may be explained by neural processing performed by the brain on the output from the cochlea. The Human Ear

Dynamic Optical Interconnections for Parallel Processors

This paper discusses the need for dynamically reconfigurable interconnection networks in parallel computing systems and describes some of the important physical parameters, limitations and tradeoffs of optical and electronic interconnection architectures. Several optical matrix-vector realizations of generalized crossbar networks are given and compared. These systems may utilize acousto-, electro-, or magneto-optic spatial light modulators as their active switching elements, and moderately large crossbar networks (64x 64 to 512 x 512) appear feasible. Finally, the use of general optical sequential logic architectures to implement crossbar and multistage networks is considered.

Dynamics during holographic exposure in photopolymers for single and multiplexed gratings

Under the assumption that at low recording intensity the grating formation process is much slower than the free monomer diffusion, we present a model that describes the dynamics of the holographic grating formation in photopolymers. The model indicates how the beam intensity modulation influences the saturation value of the grating modulation, while the average recording intensity is related in a nonlinear fashion to the process time constant. An extension of this model describes and predicts the recording of a single grating in the presence of an additional mutually incoherent light beam, and the simultaneous recording of angularly mutliplexed gratings. The model is validated by comparing with experimental results obtained using DuPont HRF-150-38 photopolymer.

Single-step copying process for multiplexed volume holograms.

A technique for copying the index or absorption modulation of a multiplexed volume holographic element into a second volume holographic medium is presented. The technique utilizes a set of coherent but mutually incoherent optical sources and can perform the copy process in a single exposure step. The concept is demonstrated experimentally for the case of three angularly multiplexed holographic gratings in dichromated gelatin.

Cascaded diffractive optical elements for improved multiplane image reconstruction

Computer-generated phase-only diffractive optical elements in a cascaded setup are designed by one deterministic and one stochastic algorithm for multiplane image formation. It is hypothesized that increasing the number of elements as wavefront modulators in the longitudinal dimension would enlarge the available solution space, thus enabling enhanced image reconstruction. Numerical results show that increasing the number of holograms improves quality at the output. Design principles, computational methods, and specific conditions are discussed.

Superposition in Optical Computing

The design of an optical computer must be based on the characteristics of optics and optical technology, and not on those of electronic technology. The property of optical superposition is considered and the implications it has in the design of computing systems is discussed. It can be exploited in the implementation of optical gates, interconnections, and shared memory.

Parallel Processing Paradigms And Optical Computing

Parallel processing models as computational paradigms are discussed and related to optical computing. Two classes of parallel computing models are discussed - shared memory models and graph/network models. These models are used to analyze some of the possible effects of optical technology on parallel computing. It is found that the use of optics potentially provides certain fundamental advantages. In addition, some factors that limit the communication capabilities of optical systems in the case of network models are found.

Autonomous ship classification using synthetic and real color images

This work classifies color images of ships attained using cameras mounted on ships and in harbors. Our data-sets contain 9 different types of ship with 18 different perspectives for our training set, development set and testing set. The training data-set contains modeled synthetic images; development and testing data-sets contain real images. The database of real images was gathered from the internet, and 3D models for synthetic images were imported from Google 3D Warehouse. A key goal in this work is to use synthetic images to increase overall classification accuracy. We present a novel approach for autonomous segmentation and feature extraction for this problem. Support vector machine is used for multi-class classification. This work reports three experimental results for multi-class ship classification problem. First experiment trains on a synthetic image data-set and tests on a real image data-set, and obtained accuracy is 87.8%. Second experiment trains on a real image data-set and tests on a separate real image data-set, and obtained accuracy is 87.8%. Last experiment trains on real + synthetic image data-sets (combined data-set) and tests on a separate real image data-set, and obtained accuracy is 93.3%.

Multi-Plane Image Reconstruction Using Cascaded Phase Elements

Cascaded phase only holograms, designed by a deterministic iterative algorithm, are used for multi-plane image formation. Numerical results show that, increasing the number of holograms decreases the error in all output planes. Therefore, this technique might be promising for the ultimate construction of a static micro-holographic 3D display.