Display systems

Abstract

In a cathode-ray tube display system, signals defining the coordinates of the element of the screen on which the cathode-ray beam is incident in its raster scan are supplied to a comparator together with signals defining the coordinates of a series of points defining the image to be displayed. The comparator derives a brightness-weighting signal in respect of each element in accordance with the proximity of that element to those of the points defining the image within a predetermined proximity. The predetermined proximity may be equal to the separation between the points. The system also includes a store, brightness-weighting signals being added together in the store to produce a total signal for each element that is used to control bright-up of the element. The store may include two units that each receive the brightness-weighting signals in respect of elements in two regions comprising several raster lines each, signals from one region being read out of one unit while signals from the other region are written into the other unit. Alternatively, the store may include a plurality of units associated with respective regions of the screen, the units being written into and associated with a particular region only if brightness-weighting signals indicate the presence of a part at least of the image in that region. The system may also include a delay unit that receives first brightness-weighting signals in respect of odd numbered elements along the raster lines and a processor that interpolates from the first signals second signals in respect of the even numbered elements, the second signals being output intermediate the first signals.