TIME AND SPACE INTEGRATING ACOUSTO-OPTIC SIGNAL PROCESSING.

摘要

One dimensional acousto-optic signal processing techniques are examined from the systems and functional viewpoint, and are then used as building blocks to synthesize multidimensional time and space integrating architectures. Time and space integrating signal processing systems are capable of performing 2-dimensional linear transformations upon images or matrices, by sequentially entering rows of the image with a travelling wave acousto-optic Bragg cell. The travelling rows are frozen by a pulsed laser diode, and the stationary diffracted fields are spatially processed by an optic system. The successively transformed rows are sequentially multiplied by a time varying reference wavefront, and accumulated on a time integrating CCD detector array to complete the two dimensional processing. Long 1-dimensional signals can also be linearly transformed by a time and space integrating system, by using a similar strategy upon a folded, or rastered, version of the high time bandwidth product signal. Small pieces of the long signal are slid into the system with an acousto-optic device, and are spatially transformed over the device aperture. Then, successively transformed portions of the long signal are multiplied by a reference, appropriately delayed and accumulated on a 2-D CCD in order to perform multichannel time integrations in the orthogonal dimension. The desired high time bandwidth one dimensional linear transformation is represented in the folded coordinate space of the 2-dimensional output detector.;The final chapter is a detailed theoretical and experimental investigation into the operating characteristics of systems designed to perform a folded spectrum analysis of very high time bandwidth signals. The 1-dimensional space integrating spectrum analysis operation performed by a lens on the diffracted field produced by a Bragg cell is used to produce a coarse spectral channelization of the input signal. Each resolvable spectral channel is fine frequency analyzed in the orthogonal direction by temporal integration, thereby forming a folded representation of the desired high time bandwidth spectrum analysis on a two dimensional detector array. The information which is needed to perform the fine frequency analysis is carried on the optical phase, so interferometric techniques are employed in order to detect and process the phase information.