Unusual waveforms are defined in terms of how many 'new' pixels are affected by the process of rasterizing them. New pixels can be those not yet affected by the rasterization of any waveform in the current set of acquisitions, or to be those that have had higher values in their raster memory location but have now been decayed to below a defined value. Once detected, such waveforms can be re-rasterized with extra intensity or into a different color by using a reserved range of values of those storable in the raster memory. Alternatively, the special region of values can be used as a counter/timer to maintain the pixels associated with unusual waveforms at a brightest intensity value, or in the color equivalent, for an extended period of time. User input can be used to affect the definition of 'new' pixels and to control the special persistence given to unusual waveforms. Unusual waveforms can also be saved in long term memory. Multiple decay functions and regions of values in the raster memory locations can be used as described above, or to produce a fast rate of decay in a bright visible region and a user adjustable slower rate of decay in a dimmer region, thus making recently acquired waveforms look bright and 'lively', while older waveforms appear to be relatively gray and stable. The same techniques can be employed when color is used either along with or as a substitute for intensity variations. <IMAGE>
Multi-function digital persistence decay