Correction circuit individual clocks of bits of a scanning mechanism; circuit generate a train of pulses for the time and process of correction of frequency of pulse of a equipamenTo sweeper (illuminated) points for each facet of a polygonal prism.

摘要

Controlling the clock rate separately for each facet of a polygon used in a driven raster output scanner whereby the clock rate for facet zero is served using a first order integrator (11) driven by a digital correction circuit which compares the actual number of pulses against the required number, and produces therefrom an analog correction pulse width which is applied to the integrator (11). A second order integrator (19) is used to compensate for leakage of charge from the parallel capacitor of the first order integrator (11), to improve performance. The remaining facets are then corrected for by assigning to each individual correction voltage. This correction voltage is generated by counting clock pulses for each additional facet and using these pulse totals to generate individual analog correction voltages which are added to, or subtracted from, the facet zero voltage in an adder (18) which combines the facet zero correction voltage with each individual voltage in sequence.