Robert A. Sprague

Surface Roughness Measurement Using White Light Speckle

An experimental investigation is made of a technique for measurement of surface roughness. A speckle pattern is formed near the image plane of a lens in spatially coherent light having a broad spectral bandwidth. The contrast of the speckle is found to be related to surface roughness when the roughness and the coherence length of illumination are comparable in magnitude. Implementation techniques are discussed and results shown that indicate good correlation with profilometer measurements for a wide range of roughness values produced with a variety of finishing procedures.

Time integrating acoustooptic correlator

This paper describes an acoustooptic technique for achieving signal correlation with a time-bandwidth product of 10(6)-10(8), using existing devices. One signal is used to intensity modulate a light beam that illuminates an acoustic cell. The other signal appears in the cell as a traveling wave and is Schlieren imaged onto a detector array. The detected image intensity is integrated in time, achieving the desired correlation function. Since the correlation integration is performed in time rather than space, the time-bandwidth limitations of earlier acoustooptic correlators are greatly reduced. Experimental procedures for implementation of this technique are discussed and results shown.

Quantitative Visualization of Large Variation Phase Objects

This paper describes a technique by which a large variation phase object may be visualized in an image having an irradiance which is directly proportional to the object phase. An image of the phase object derivative is formed in a coherent optical system and recorded on photographic film. This photograph is used as the input to a second coherent optical system, in which the image is an integral of the input. No limitations are imposed on the maximum object phase, only on its maximum slope. Experimental techniques for implementation of this system are discussed and results shown.

Real-time optical correlation

A real-time coherent optical correlator is described that uses the Itek PROM as a recyclable filter recording medium. Operation of a joint transform correlator is compared to a conventional Vander Lugt system. Experimental results are shown for the joint transform system, including demonstrations of the effects of target alignment and scale and the correlation of random bit rasters for signal processing applications.

The PROM - A Status Report

The PROM is a solid-state, rapidly recyclable, image storage device having a number of applications in image and signal processing. Some of its important characteristics include 1/10-wave optical surface quality, 100-1p/mm three-bar resolution, 10 ergs/cm2 light sensitivity, and image plane contrast of 10 4 :1. One of the unique features of the PROM is that the bias level of stored patterns can be adjusted through application of an external voltage, resulting in image contrast inversion or enhancement. This same operation (baseline subtraction) is used to null the zero order in an optical Fourier transform, achieving a Fourier plane signal-to-noise ratio approaching 106:1. This paper reports on the current status of this device and a number of applications for which it has been tested in several areas of image and signal processing. Results are shown for coherent optical processing by computer-controlled Fourier plane filtering and real-time image correlation, and signal processing systems are described which couple the PROM with an acousto-optic raster recorder to perform spectrum analysis and correlation on radio frequency signals.

Acoustooptic snapshot PROM: a real-time optical-signal spectrum analyzer

This paper describes a system which performs real-time optical processing of electrical signals. The signals of interest are recorded in a raster format on the Itek PROM (Pockels Readout Optical Modulator), a light addressed electrooptic imaging device. The PROM is then read out with laser light to perform optical Fourier transformation, achieving spectrum analysis in near real time. A technique called acoustooptic snapshot recording is used to generate the required low distortion raster at rf bandwidths.

VLSI-based image bar for laser beam recording

There are many image bar technologies which make use of a full width light modulator which projects one-to-one onto the photoconductor. An alternative to these full width image bars makes use of a micro image bar, in which all of the drive electronics are integrated on a single monolithic VLSI circuit. The TIR linear spatial light modulator is such a device which is built using an integrated circuit in conjunction with an electro-optic crystal to achieve light modulation.There are many image bar technologies which make use of a full width light modulator which projects one-to-one onto the photoconductor. An alternative to these full width image bars makes use of a micro image bar, in which all of the drive electronics are integrated on a single monolithic VLSI circuit. The TIR linear spatial light modulator is such a device which is built using an integrated circuit in conjunction with an electro-optic crystal to achieve light modulation.

The ITEK PROM - A Status Report

The PROM is a solid state, rapidly recyclable, image storage device having a number of applications in image and signal processing. Some of its important characteristics include 10th-wave optical surface quality, 100 1p/mm three-bar resolution, 10-ergs/cm2 light sensitivity, and image plane contrast of 104:1. One of the unique features of the PROM is that the bias level of stored patterns can be adjusted through application of an external voltage, resulting in image contrast inversion or enhancement. This same operation (baseline subtraction) is used to null the zero order in an optical Fourier transform, achieving a Fourier plane signal-to-noise ratio approaching 106:1. This paper will report on the current status of this device and a number of applications for which it has been tested in several areas of image and signal processing. Results will be shown for coherent optical processing by computer controlled Fourier plane filtering and real time image correlation, and sig-nal processing systems will be described which couple the PROM with an acousto-optic raster recorder to perform spectrum analysis and correlation on radio frequency signals.