Error Reduction in Two-Dimensional Pulse-Area Modulation, with Application to Computer-Generated Transparencies

摘要

The synthesis of band-limited functions that are generated by properly low-pass filtering a regular array of area-modulated unit-height pulses is considered. Simply choosing the pulse areas proportional to the corresponding sample values of the band-limited function to be generated, would result in an error. The exact relationship between the pulse areas and the corresponding sample values of the band-limited function to be synthesized is derived. Error reduction can be achieved by using this relationship to calculate the pulse areas from the required sample values; in principle, a band-limited function can thus be realized to any degree of accuracy. It is shown which amount of error reduction can be obtained, when only a limited number of terms of the exact relationship is taken into account. The application to computer-generated half-tone transparencies is described.