ADAPTIVE CORRECTOR OF FACET ERRORS IN MIRROR SCANNING SYSTEMS

摘要

A beam deflection system is provided with electrical circuitry for adaptively correcting the deflection of a beam of radiant energy in a scanning system incorporating a rotating scanning mirror to compensate for misalignment in facets of the mirror. With the use of an acousto-optic modulator providing a deflected beam at an angle dependent on the frequency of an acoustic drive signal, the orientation of the beam can be altered to compensate for the misaligned facets by varying the acoustic frequency. A sensor and bridge circuit signal the position of a beam scan. A memory stores the value of the frequency for scans by each facet, the value being altered with each scan to optimize the frequency. A drift compensation circuit provides for an averaging of the parameter values, and provides a voltage to adjust the balance of the bridge to drive the average value towards a reference value.