METHOD OF TESTING THE LINEARITY OF A RASTER SCAN

摘要

The method for testing the linearity and other raster scan geometry of a television display apparatus or a television camera. The method is used when the display apparatus or camera being tested has a scan rate which cannot match the currently used EIA linearity chart due to fundamental differences in the raster structure and can also be used on the 525/60 scan rate as used in broadcast mode without requiring the unusual alternate count required for the EIA chart. In testing a display apparatus, a bar or dot pattern is formed on the screen by a test pattern generator wherein the spacing of the horizontal rows of dots or bars is selected to correspond to a particular scan rate. A linearity chart having a geometry corresponding to that scan rate is selected from a plurality of test charts and the image thereof is projected on the screen to match, as closely as possible, the dots or bar intersections on the screen. The amount of non-linearity can be quantified by noting the positions of the dots or bar intersections relative to the concentric annuli of each graphic element making up the chart. The television camera can be tested in a similar fashion by viewing the selected linearity chart and superimposing the image produced by the camera with the dot or bar pattern of the selected scan rate produced by the test pattern generator.