Pulse Density Modulation: Synthetic Formation Of Binary Images And Holograms

A large portion of our world concerned with manipulation and communication of information has turned binary. A consequence has been hardware with improved SNR. A demand and interest for binary coding procedures has arisen from this trend. Several 1-0 schemes in electronics like PWM, PPM, and PCM have been extended to 2-D optical counterparts in a straightforward way. In contrast to these cases with equidistant sampling we will also discuss situations with nonequidistant sampling where the information is coded by the positions of the pulses in such a way that the two dimensions are inseparable. This implies that no constant carrier frequency is introduced. In pulse density modu-lation (POM) the pulse separations are inversely proportional to the local signal level. Characteristic for POM is that a large number of degrees of freedom exists. They have to be handled by the coding algorithm. We will show examples how these degrees of freedom can be coupled to certain directional properties of the 2-0 signal.