A. Mahapatra

DEFT Sensor Operating at 100 MHz

Two years ago we reported on a two-dimensional SAW device capable of producing electronic signals representative of Fourier transforms of twodimensional optical intensities. frequencies of 89 MHz and 110 MHz with corresponding image sampling to remove the redundancy in the cransform, and a thinner (.5pm) CdS film in order to reduce attenuation. alization to provide image sampling, rather than using a suspended grating. tify spatial frequencies of up to 50 lines/cm in magnitude along any desired direction. The programmability of the device will permit it to produce any integral decomposition as long as the kernel is separable and requires finite bandwidth. The current device uses much higher center

Image Processing Via Ultrasonics: Status And Promise

We here discuss acousto-electric devices for electronic imaging of light. These devices are more versatile than line scan imaging devices in current use. They have the capability of presenting the image information in a variety of modes. The image can be read out in the conventional line scan mode. It can be read out in the form of the Fourier, Hadamard, or other transform. One can take the transform along one direction of the image and line scan in the other direction, or perform other combinations of image processing functions. This is accomplished by applying the appropriate electrical input signals to the device. Since the electrical output signal of these devices can be detected in a synchronous mode, substantial noise reduction is possible.

Programmable Multifunction Processor

A new two-dimensional DEFT sensor (for Direct Electronic Fourier Transform) for multi-processing will be described. Operating at a center frequency of 100 MHz, it is capable of resolving 1800 unique spatial Fourier image components in a random access mode. As a Fourier transformer it can identify vector spatial frecuencies, their amplitude and phase. By suitable change of input functions, the device can be operated as a spatial raster scanner, Hadamard transformer, matrix multiplier, or convolver. The device achieves this flexibility by virtue of producing the spatial integral of the product of two electronic signals with an optical signal.

Doubled‐layered polycrystalline cadmium sulfide on lithium niobate

We have developed a technique for fabricating polycrystalline thin films of CdS on z‐cut LiNbO3. A single film will show a light‐to‐dark–conductivity ratio of approximately unity with very high sheet resistance after curing. To make a good photoconductor, a second film is then deposited. This film is protected during the subsequent curing from out‐diffusion from the LiNbO3 by the first film and develops a light‐to‐dark–conductivity ratio of 10 000 in room light with a sheet conductivity of 10−10 s/⧠ mcd. Films produced by this layered process also possess a remarkably large conductivity‐modulation dependence (20%) on the square of an impressed electric field provided by a traveling surface acoustic wave in the LiNbO3 substrate.

Spurious acoustic modes in two-dimensional Fourier transform devices

Experiments conducted on two-dimensional (2D) Fourier transform sensors using CdS films on z-cut LiNb03 show evidence for the presence of more than one acoustic velocity in the substrate. Pulsed experiments conducted with two transducers and detailed measurements of transducer frequency response confirm the presence of these additional modes. As a result, the Fourier transform of any image repeats itself in frequency space, the number of repetitions depending on the number of additional acoustic modes. The detrimental effects of these spurious modes can be eliminated entirely by suitable sampling of the image projected on the sensor.