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AssigneeBidco Inc.
InventorsHarvey Bidner, James J. Zuber
Estimating the term…
A laser scanning apparatus is provided with a compensating arrangement whereby deviations of a synchronous drive are compensated for by adjusting the frequency with which the laser beam is modulated. The laser beam is directed onto a rotatable spinner which causes the laser beam to scan a synchronized moving medium in a number of sequential and parallel lines, each of which is determined during a cycle of the movement of the spinner. The spinner is driven by a synchronous motor. During each cycle, a period error is measured to determine a compensating signal which is held for the next successive cycle and is used to control the frequency of a variable oscillator which determines the clocking rate at which information is employed to modulate the laser beam. According to the method of the invention, lines of information are placed on a synchronized moving medium responsive to the aforesaid laser beam during successive cycles. The method involves modulating the laser beam in accordance with the information and at a frequency which is modified for each cycle in accordance with the deviation of the preceding cycle with respect to a characteristic normal time period.
Apparatus comprising a source of a laser beam, a medium adapted for being processed by said laser beam, scanner means adapted for directing said laser beam and causing said laser beam to scan said medium in sequential scan lines, drive means to drive said scanner means to produce said sequential scan lines, said drive means having a rotational speed subject to deviations, compensating means to respond to said deviations to correct subsequent sequential scan lines, modulating means to modulate said laster beam in accordance with pixel information to be placed upon said medium, said compensating means controlling said modulating means to control the rate with which the pixel information is placed upon said medium to compensate for the deviations of the drive means so that the rate at which the pixels are generated for each scan line is corrected relative to the rate at which the pixels were generated in the previous scan line, memory means for storing said information, said compensating means controlling the release of said information from the memory means to the modulating means, counting means to generate an error count during each of said sequential scan lines, the resulting error counts being proportional to said deviations, and a start-of-line sensor means to generate a start-of-line signal for each of said sequential scan lines and to apply the resulting start-of-line signals to the counting means to commence and terminate the count for each of said scan lines.
Dependencies are inferred from the claim text.