Laser beam scanning device

Abstract

Abstract PURPOSE:To correct the scanning irregularity of an image resulting from the use of a rotary polygon mirror by controlling the frequency of a clock for modulating a laser beam in picture element units according to the check result of the state of a surface to be scanned which is one scan before. CONSTITUTION:One surface of the rotary polygon mirror 22 is scanned with a laser beam of a 1st system and then scanned with a laser beam of a 2nd system. Then, the detection output of a 2nd scanning start photodetector 35 becomes a 1st input to a function oscillator 58 and another voltage-controlled oscillator 59. The voltage outputted by a 2nd scanning end photodetector 36 becomes a 2nd input to the voltage- controlled oscillator 59. Further, the voltage outputted by the function generator 58 is added to the output voltage of a DC converter 47 by an adder 55 to generate a 3rd input to the voltage-controlled oscillator 59. Then, the oscillation output 67 of the voltage-controlled oscillator 59 is supplied to a frequency divider 68, a clock 69 which is obtained by frequency division is corrected in response to variation in scanning speed, and an information signal of each picture element is read out in synchronism with the clock 69. Consequently, proper correction corresponding to variation in the rotating speed of the rotary polygon mirror and the states of respective surfaces is enabled.

Inventors

• 👤 Atsushi Hakamata
• 👤 袴田　厚

Bibliographic Details