Abstract: A method for defeating illegal receivers sensitive to the edges of synchronization signals in a scrambled video signal is provided. The scrambled video signal includes synchronization signals having levels which prevent a standard receiver from detecting the synchronization signals by using the levels of the synchronization signals. The synchronization signals also have one or more pulses with level transitions above or below a signal detection threshold level of the standard television receiver which prevent the illegal receivers from detecting the synchronization signals by using the edges of the synchronization signals.

Abstract: A method and apparatus for linear shading of a polygon rendered in a raster graphics display is disclosed. Apparatus is included for selecting a key vertex which is located opposite to an edge of the polygon having a selected orientation. Apparatus is further included for dividing the polygon into a group of triangles so as to create a base leg for each of the triangles in the selected orientation. Apparatus is further included for calculating the horizontal endpoints and their associated luminance values for each scan line between each triangle's base and the bases opposite vertex so as to describe a plurality of scan lines further comprising a plurallity of pixels within each triangle. Apparatus for interpolating the luminance of each of the scan line pixels so as to shade each of the triangles completes the linear shading. In one embodiment of the invention, the pixel luminance values for several pixels can be simultaneously calculated resulting in greatly improved throughput as compared to known systems.

Abstract: An improved system for the automatic correction of centering and convergence errors in a cathode ray tube display is disclosed. The system includes a first masked light sensor (12) positioned on the major axis of the display and a second masked light sensor (14) positioned on the minor axis of the display. A light blip generator (16) is responsive to the horizontal and vertical timing pulses for unblanking the video circuits during the horizontal and vertical blanking intervals in order to generate light pulses in the vicinities of said first and second light sensors. A microprocessor based feedback controller (10) is responsive to the outputs of the light sensors and programmed to iteratively generate correction signals whenever no output is received from one or both of the light sensors.