Digital ρ-θ to XY scan converter for use with limited access or random access reiteration memory

Claim 1

A scan converting display system for displaying digitized data available in a polar format defined by ρθ addresses and comprised of a plurality of lines radiating from a common focus, each said line being defined by a predetermined θ address onto a rectangular raster defined by XY addresses wherein the raster is comprised of a plurality of substantially parallel raster lines, each said raster line having a Y address comprising: means for generating a repeating sequence of X and Y addresses; means for generating said raster in response to said repeating sequence of X and Y addresses; a reiteration memory means responsive to said repeating sequence of X and Y addresses for reading data stored in said reiteration memory means onto said means for generating said raster synchronously with said raster whereby said data is displayed on said raster; means for temporarily storing a line of the polar format digitized data in uniform increments of ρ; means for generating as a function of the θ address of the line of the polar format digitized data in said means for temporarily storing and said X and Y addresses ρcal signals corresponding to ρ addresses of data in said means for temporarily storing and a signal defining the cells of said reiteration memory to be up-dated during the generation of a particular raster line; and, means for comparing said X address with the signal defining the cells of said reiteration memory to be up-dated for generating an up-date signal, said means for temporarily storing being responsive to the ρcal signals and said up-date signal to up-date said reiteration memory with data at corresponding ρ addresses in said means for temporarily storing.