JPS5782814A - Optical scanner - Google Patents

Abstract

PURPOSE:To automatically compensate the position error of the optical scan which is caused by the zero-point drift of a survo amplifier that drives an optical scanner as well as by the gain drift, by providing a position detector to the optical scanner including at least >=1-dimensional optical scan system. CONSTITUTION:An incident beam 1 is reflected by a scanning mirror 3 which is driven by a scanner 2 and then scanned on a scanning surface 6 by a scanning lens 4 and a beam splitter 5. On the other hand, the beam transmitted through the splitter 5 is irradiated on position detectors 9a and 9b. The distance between the detectors 9a and 9b is set equal to the maximum distance X of the scanning range. The electric output is set at zero when the beam is irradiated to the center of the position detector; and the position differential signal proportional to the distance measured from the center of the detector is obtained when the beam is irradiated at an off-center position, respectively. The position differential signals given from both detectors 9a and 9b are amplified by a position differential amplifier 11 to control both the zero point and the gain of a variable zero point/gain amplifier 13. This output signal is supplied to a servo amplifier 8 to control the scanner 2.