KEYSTONE COLLECTION CIRCUIT

PROBLEM TO BE SOLVED: To provide a keystone correction circuit which corrects to a normal aspect ratio even if the boundary between a video image and a screen is unclear. SOLUTION: The keystone correction circuit comprises: a coordinates calculator for calculating coordinates positions on the LCD panel at four vertexes of the video image distorted reversely, so that the distortion of a video image region on the screen is canceled out based on parameters, such as a vertical pitch angle θ and a horizontal one ; a parameter calculator for calculating a parameter required for arranging each pixel of video image data in the coordinates positions on the LCD panel at four vertexes obtained by the coordinates calculator; a keystone corrector for arranging the inputted video image data in the coordinates positions on the LCD panel at four vertexes to generate a video image output signal by using the parameters obtained by the parameter calculator; a guide video image generator for generating a guide video image, where the portion between adjacent coordinates is connected by a straight line in the coordinates on the LCD panel at four vertexes obtained by the coordinates calculating section; and an addition processor for adding the video image output signal to the guide video image, and for outputting the result. COPYRIGHT: (C)2007,JPO&INPIT