A modulator for modulating an incident beam of light, the modulator comprising a plurality of equally spaced-apart elements, each of which includes a light-reflective planar surface. The elements are arranged parallel to each other with their light-reflective surfaces parallel to each other. The modulator includes means for supporting the elements in relation to one another and means for moving particular ones of the elements relative to others so that the moved elements transit between a first configuration wherein the modulator acts to reflect the incident beam of light as a plane mirror, and a second configuration wherein the modulator diffracts the light reflected therefrom. In operation the light-reflective surfaces of the elements remain parallel to each other in both the first and second configurations. The perpendicular spacing between the reflective surfaces of the respective elements is equal to m/4 × the wavelength of the incident beam of light, wherein m equals an even whole number or zero when the elements are in the first configuration and m equals an odd whole number when the elements are in the second configuration.

Method and apparatus for modulating a light beam

Music perception and performance rely heavily on temporal processing: for instance, each event must be situated in time in relation to surrounding events, and events must be grouped together in order to overcome memory constraints. The temporal structure of music varies considerably from one culture to another, and so it has often been supposed that the specific implementation of perceptual and cognitive temporal processes will differ as a function of an individual’s cultural exposure and experience. In this paper we examine the alternative position that some temporal processes may be universal, in the sense that they function in a similar manner irrespective of an individual’s cultural exposure and experience. We first review rhythm perception and production studies carried out with adult musicians, adult nonmusicians, children, and infants in order to identify temporal processes that appear to function in a similar fashion irrespective of age, acculturation, and musical training. This review leads to the identification of five temporal processes that we submit as candidates for the status of ‘temporal universals’. For each process, we select the simplest and most representative experimental paradigm that has been used to date. This leads to a research proposal for future intercultural studies that could test the universal nature of these processes.

The Cognitive Neuroscience of Music

Tonal music is a highly structured system that is ubiquitous in our cultural environment. We demonstrate the acquisition of implicit knowledge of tonal structure through neural self-organization resulting from mere exposure to simultaneous and sequential combinations of tones. In the process of learning, a network with fundamental neural constraints comes to internalize the essential correlational structure of tonal music. After learning, the network was run through a range of experiments from the literature. The model provides a parsimonious account of a variety of empirical findings dealing with the processing of tone, chord, and key relationships, including relatedness judgments, memory judgments, and expectancies. It also illustrates the plausibility of activation being a unifying mechanism underlying a range of cognitive tasks.

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Implicit learning of tonality: A self-organizing approach

A display system for providing a two dimensional image includes an essentially one dimensional light valve array. The diffractive light valve array includes modulator elements which diffract or reflect light incident thereon to an extent determined by an image element to be represented. The display system is arranged such diffracted light from the light-valve array passes through a magnifying lens and is separated from the reflected light from the array. A magnified virtual image of the array formed by the diffracted light is viewed through the magnifying lens. A scanning arrangement between the viewer and the magnifying lens scans the image of the light-valve array across the field of view of the viewer sufficiently quickly that the viewer perceives the scanned image as a two-dimensional image. In another arrangement a printer is formed by scanning a real image of the diffractive light valve array over a printing or recording medium.

Display device incorporating one-dimensional grating light-valve array

One embodiment provides an apparatus for displaying an image comprising: a first optical substrate comprising at least one waveguide layer configured to propagate light in a first direction, wherein the at least one waveguide layer of the first optical substrate comprises at least one grating lamina configured to extract the light from the first substrate along the first direction; and a second optical substrate comprising at least one waveguide layer configured to propagate the light in a second direction, wherein the at least one waveguide layer of the second optical substrate comprises at least one grating lamina configured to extract light from the second substrate along the second direction; wherein the at least one grating lamina of at least one of the first and second optical substrates comprises an SBG in a passive mode.

Transparent waveguide display

Computation-intensive applications such as sensor signal processing, sensor fusion, image processing, feature identification, pattern recognition, and early vision place stringent requirements on the computational capacity, size, weight, and power dissipation of modular computational systems intended for both embedded and high performance computer environments. Such ultra high speed, ultra high density computational modules will typically be configured with multiple processor, memory, dedicated sensor, and digital signal processing chips in close-packed multichip modules. The present invention relates to a novel architecture and associated apparatus for the development of highly multiplexed photonic interconnections between pairs of such electronic chips incorporated in vertical stacks within three-dimensional multichip module configurations. Vertical signal transmission through the chip substrates is accomplished by using a planar-waveguide-based optical power bus to provide a parallel array of beams to read out a modulator array that is flip-chip bonded to each silicon substrate. Local and quasi-local connectivity in the vertical dimension is accomplished by using diffractive optical structures that provide for both point-to-point interconnections and weighted fan-out within a local neighborhood. Global connectivity is incorporated by means of computer-generated volume holographic optical elements that are fabricated as a multilayer diffractive optical element. Several different architectural implementations of such computational modules are provided to address applications that include high-bandwidth two-dimensional displays, multilayer neural networks, image processors, multiple processors with access to shared memory, and rending engines for computer animation and graphics. In addition, subsystems of the computational-module architecture and apparatus are described that provide for compact optical readout of modulator-based flat panel displays.

Modulator-based photonic chip-to-chip interconnections for dense three-dimensional multichip module integration

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.

First-harmonic diffusion model for holographic grating formation in photopolymers

Novel multiplexed volume holographic optical elements for the development of highly multiplexed photonic interconnection and holographic memory systems with maximum optical throughput efficiency and minimum crosstalk, based on parallel incoherent/coherent double angularly multiplexed volume holographic recording and readout principles, are disclosed. These principles further provide for arbitrarily weighted and independent interconnections, which are of potential importance in the development of densely interconnected photonic implementations of neural networks, photonic interconnection networks for telecommunications switching and digital computing applications, optical information processors, and optical memories. Utilization of the principles that are key features of this holographic element allows for the single step transfer of all or part of the information stored in a three-dimensional holographic storage device to a second such device in a single exposure step. Variants of the multiplexed volume holographic optical element include bulk holographic recording media as well as stratified volume holographic optical elements, comprising in either case both holographic (optical) modulation patterns and computer-generated holograms. Further variants of the multiplexed volume holographic optical element incorporate a subhologram structure within the volume holographic optical element that allows for high efficiency recording in certain real time photorefractive media.

Incoherent/coherent double angularly multiplexed volume holographic optical elements

The present invention relates to a novel source array comprising a plurality of sources of optical illumination that are at once both individually coherent and mutually incoherent. A primary application of such a source array is to provide the requisite optical source beams in a novel architecture and associated apparatus for the development of highly multiplexed photonic interconnection networks and holographic optical elements with maximum optical throughput efficiency and minimum interchannel crosstalk, based on parallel incoherent/coherent holographic recording and readout principles that are described herein. In one embodiment, the source array is configured from a plurality of coherent sources of illumination; in a second embodiment, a single source of coherent illumination is expanded to illuminate a phase modulator array, within which each separate phase modulator is driven at a distinct oscillation frequency such that the set of resultant modulated beams exhibits mutual incoherence. Such incoherent/coherent source arrays are critical for providing arbitrarily weighted and independent interconnections, which in turn are of potential importance in the development of neuro-optical computers, as well as photonic interconnection networks and multiplexed holographic optical elements. In addition, the extremely difficult problem of copying the contents of a three-dimensional holographic storage device in one step is enabled by utilization of the incoherent/coherent source arrays that are the key features of the present invention.

Incoherent/coherent source array for multiplexed holographic recording and readout

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

B. Keith Jenkins

Papers

Modulator-based photonic chip-to-chip interconnections for dense three-dimensional multichip module integration

First-harmonic diffusion model for holographic grating formation in photopolymers

Incoherent/coherent double angularly multiplexed volume holographic optical elements

Incoherent/coherent source array for multiplexed holographic recording and readout

A Neural Network Model for Pitch Perception