Simple interferometer for monitoring Rayleigh waves.

An improved interferometer for monitoring Rayleigh waves is described. Consisting of a light source, reflective grating, lens, and detector, the design is simple and inexpensive. It can be employed with specular as well as diffuse reflecting surfaces to monitor surface deformations with the sensitivity of a Michelson interferometer. By spinning the grating element, sensitivity variations with grating position are removed, resulting in stable operation. The interferometer response does vary with acoustic wavelength; a discussion of acoustic bandwidth shows that proper design can result in either a wide or narrow bandwidth response.

Galvanometer deflection: a precision high-speed system.

An X-Y galvanometer deflection system capable of high precision in a random access mode of operation is described. Beam positional information in digitized form is obtained by employing a Ronchi grating with a sophisticated optical detection scheme. This information is used in a control interface to locate the beam to the required precision. The system is characterized by high accuracy at maximum speed and is designed for operation in a variable environment, with particular attention placed on thermal insensitivity.

Restoration of degraded images by composite gratings in a coherent optical processor.

A study has been made on restoration of degraded images utilizing spatial filtering techniques in a coherent optical processor. This study differs from other coherent approaches in that the spatial filters employed contain only composite gratings that are quite simple to produce. A general method of synthesizing the appropriate composite gratings for the linearly smeared as well as multiply exposed and out-offocus images will be presented in some detail with experimental results. The extension of the method of synthesis to other types of degradation will be briefly discussed. in Appendix A.

Single step detection of blurred images in a coherent optical processor.

Two important operations that can be performed by coherent optical processing systems are image detection and image restoration. These operations require complex spatial filters, and if both operations are to be performed, cascaded processing stages employing two separate spatial filters are usually needed. Spatial filters are described that will perform in a single step both operations simultaneously, thus eliminating the need of extra processing stages while providing the advantages of higher efficiency and smaller space requirements. The filters are characterized by their simplicity and are easily fabricated using conventional techniques. Experimental results are presented.

Matrix multiplication by optical methods: experimental verification.

Matrix multiplication has been performed by optical analog methods using the scheme of Heinz et al. The most critical element was F(a), the spatial filter corresponding to the two-dimensional Fourier transform of a. In the operation c = b x a, errors in the c elements were 1-2% when the a elements were all approximately the same. Very large errors occurred when the a elements differed significantly, and these were used directly [instead of the F(a) derived values] in the numerical comparisons. These errors were attributed to the limited linear range of the amplitude transmittance characteristic of the film used. Suggestions for future work are made.