VIDEO CLOCK GENERATOR, IMAGE FORMING APPARATUS COMPRISING IT AND VIDEO CLOCK GENERATING METHOD

摘要

PROBLEM TO BE SOLVED: To provide a simple and inexpensive video clock generator operable at the maximum oscillation frequency of a PLL and capable of highly accurate digital frequency modulation, and to provide an image forming apparatus comprising it and a video clock generating method. SOLUTION: A video clock generating means 12 generates a video clock having a period an integer N times as long as the specified period of a reference clock generated from a reference clock generating means 11. An error calculating means 15 calculates the error between the period of a target video clock dependent on the number of pixels and scanning width of one scanning line and the period of an actual video clock, and an error accumulating means 14 accumulates the results. The error accumulating means 14 is preset with a threshold value and modulates the period of one video clock based on the reference clock when the accumulated error exceeds the threshold value. COPYRIGHT: (C)2004,JPO&NCIPI