JPS5797267A - Optical scanning device - Google Patents

Abstract

PURPOSE:To detect an accurate phase synchronizing signal and to achieve optical scanning with high accuracy, by compensating the amount of light of scanning light flux at a phase synchronizing period so as to keep said amount of light a constant value at all times independently of the amount of light at other period such as picture period or the like. CONSTITUTION:A light flux from a light source 1 is incident to a rotating mirror 6 via an ultrasonic wave photo modulator 4 and scans an optical scanning plane 8. When a phase synchronism detector 9 provided at a phase synchronism period B of the optical scanning plane 8 detects a scanned light flux, a detection signal (b) is outputted and it is converted into a phase synchronizing signal (e), inputted to a mirror plane synchronism circuit 12, a mirror plane synchronizing signal g-i is formed and it is inputted to an AND gate 25-i of each plane light amount correction circuit 15 at phase synchronism period together with a phase synchronizing period signal (k) to turn on an analog switch 23-i. On the other hand, a signal (d) from a phase synchronism amplifier 10 is held and compared with a reference level at a level comparator 28, and the output O is inputted to a photo modulator drive circuit 5 via a switch 23-i.