Prototype Image Spectrum Analyzer (PISA) for Cartographic Feature Extraction

摘要

An electro-optical system for obtaining two-dimensional Walsh transforms of cartographic images was developed. The system uses a plasma discharge device to generate visible two-dimensional Walsh function pattern masks. The cartographic imagery is placed in contact with the plasma tube, and the product of the mask and image is integrated with a single photodetector. The sytem is capable of producing 512 by 512 (262, 144), two-dimensional Walsh functions, and the same number of associated Walsh transform coefficients in about 14 seconds. The quantitative measurement and display of the relative magnitude of the first block of Walsh transforms (64 x 64) was facilitated with a system minicomputer and a CRT display. A set of selected cartographic images and targets were used to evaluate the system. It was discovered that most of the significant transform information appeared in the lower order Walsh transform coefficients, and further that each Walsh transform pattern is unique in itself and can be distinguished from the others for a limited set of well defined inputs. The dynamic range, the temporal response, and the symmetry of responses of the Prototype Image Spectrum Analyzer (PISA) were found to be relatively poor. (Author)