Method of generating image scanning clock signals in optical scanning

Abstract

Reference clock signals of the same frequency as that of image scanning clock signals are applied to a shift register, and corrective clock signals of a higher frequency than that of the reference clock signals C.sub.0 are applied as shift clock signals to the shift register, which generates n output signals C.sub.1, C.sub.2, . . . C.sub.n (n.gtoreq.2) which are applied to delay circuits. The delay circuits produce pulse signal groups which are successively delayed .DELTA.t in phase. Assuming that the frequency of the reference clock signals is f.sub.0 MHz and the frequency of the corrective clock signals is n.multidot.f.sub.0 MHz, the above phase .DELTA.t is selected to meet meets the relationship: ##EQU1## One of the pulse signal groups thus delayed .DELTA.t in phase is selected as image scannnig clock signals in response to an output signal from a light sensor that detects a scanning beam for synchronizing main scanning cycles.