Patent ID: 8531499

Claim:
An optical scanner, comprising: a light source to emit a laser beam; a scan-deflecting portion including a resonance mirror to scan and deflect along a scan line including an effective scan area of a scan object while reflecting the laser beam; a plurality of light-receiving sensors for synchronous detection provided on the scan line; a phase controller configured to obtain a difference between a true phase that is signal-processed based on pulses from at least one of the plurality of light receiving sensors and a target phase, and generate a drive signal that incorporates the difference; a driving device to supply the drive signal generated by the phase controller to drive the resonance mirror; an amplitude controller configured to measure time intervals during which the laser beam scanned and deflected by the scan-deflecting portion passes each of the plurality of light receiving sensors, obtain a first value equivalent to a true amplitude of scan deflection of the scan deflecting portion based on the time intervals, incorporate the difference between the first value and a second value equivalent to the target amplitude into the drive signal generated by the phase controller, control the amplitude of the drive signal, and control amplitude at a control sampling frequency that is 2N times a resonance frequency of the scan deflecting portion when the number of the plurality of the light receiving sensors is N, where N is a positive integer equal to or greater than two; and an offset controller configured to measure time intervals during which the laser beam scanned and deflected by the scan deflecting portion passes each of the plurality of light receiving sensors, calculate an offset value based on the difference between each of the time intervals, incorporate the difference between a true offset value and a target offset value into the amplitude-controlled drive signal, and supply the offset-controlled drive signal to the driving device.