Patent ID: 7830406

Claim:
An LED printer comprising: a photosensitive drum mounted to undergo rotation about a rotating shaft in a sub scanning direction; a resist roller that feeds a printing medium to the photosensitive drum at a first constant speed; a fixing device that discharges the printing medium from the photosensitive drum at a second constant speed different from the first constant speed; a separation type LED head having a first portion LED head and a second portion LED head, the first portion LED head and the second portion LED head being arranged parallel to a main scanning direction at an LED head interval which is a predetermined interval in the sub scanning direction while end portions thereof are overlapped with each other, and the first portion LED head being disposed before the second portion LED head relative to the rotation of the photosensitive drum; and a printing control circuit that (a) detects a position of the printing medium fed by the resist roller or the fixing device, (b) adjusts printing timings of the first portion LED head and the second portion LED head based on the detected position and the LED head interval, (c) outputs a line clock pulse signal at a reference cycle corresponding to the LED head interval in the position of the printing medium in which the printing medium is fed by the resist roller and the fixing device, (d) sets print timings of the first portion LED head and the second portion LED head as a timing of the line clock pulse signal outputted at the reference cycle when the detected position is the position of the printing medium in which the printing medium is fed by the resist roller and the fixing device, (e) delays a cycle of the reference cycle and sets the print timing of the first portion LED head as a timing delayed by a predetermined time from the line clock pulse signal outputted at the delayed reference cycle, when the detected position is the position of the printing medium in which the printing medium is fed by only the resist roller, and (f)advances the cycle of the reference cycle and sets the print timing of the second portion LED head as a timing delayed by a predetermined time from the advanced reference cycle, when the detected position is the position of the printing medium in which the printing medium is fed by only the fixing device.