Coherent Optical Methods Research Articles

An optical processor for radio pulses from an antenna array

A coherent optical method of processing pulsed radio signals received by a planar antenna array is described. The output is the two-dimensional optical image of the brightness distribution of the radio sky. Experimental results for a 4 × 4 array are presented.

Limits to the Detection of Small Internal Voids in Solids with Holographic Techniques

The ability to find small voids in acoustically excited solid specimens using coherent optical detection methods is limited by three factors: available ultrasonic power levels; noise elements; and nonlinear properties of the working materials. Detection sensitivity constraints due to power limitations are established here. A void embedded in an elastic half-space is used as a physical model. Free surface deformations due to internal void-scattered ultrasonic waves are computed for select cases. Deformations are too small for direct optical measurement. Deflections of a liquid layer free surface above the elastic halfspace represent an amplified copy of the elastic boundary deformation and improved detection sensitivity. Holographic techniques with noise reduction features to observe the liquid surface profile are discussed.

Measurements of the Correlation Length of Random Scenes by a Coherent Optical Method

Measurements of the Correlation Length of Random Scenes by a Coherent Optical Method

Comments on: Measurements of the Correlation Length of Random Scenes by a Coherent Optical Method

Comments on: Measurements of the Correlation Length of Random Scenes by a Coherent Optical Method

Variance Measurements by a Coherent Optical Method, with Application to Image Processing

A procedure for measuring the point-to-point local variance of a spatial random scene is discussed. The relations that are required between the second-order statistics of the random process and the parameters of the optical configuration to furnish accurate and stable variance estimates are established. The procedure is experimentally verified by using calibrated samples of the random checkerboard and the overlapping circular grain models. A modification of the procedure enables the generation of spatial masks that are useful in automatic image processing. The spatial masks are used as binary spatial gates to isolate certain classes of objects within a scene and reject all others. Typical masks are synthesized and their applications illustrated.