Xerox Corporation

Rudiger W Tietze

Leland D Green

Michael E Wilmer

A video signal white level corrector wherein a digital memory is used to store a correction signal which is applied to a signal multiplier to remove white level shading which results from optic and beam misalignment of a scanner. Video signals are applied to a multiplier 10, the output therefrom being the corrected video signal. The correction signal is stored for future use in a digital memory 14 after being compared to a reference voltage at comparator 20. In a first, or 'store', mode, the output from the comparator 20 is coupled to an integrator 22, the output of which increases or decreases the gain of multiplier 10. In a second, or 'operate', mode, the output from the digital memory is coupled to integrator 22 to also control the gain of multiplier 10.

Video signal white level corrector

The output beam from a laser scans an input document and the signal reflected therefrom, corresponding to information on the document, is detected and amplified in a first amplifier and converted to an electrical signal. The laser beam is also sampled prior to scanning the document, the beam being detected and converted to an electrical signal which is then amplified in a second amplifier. The outputs of the first and second amplifiers are coupled to a gain control device. The gain versus control voltage characteristic of the device is selected such that the voltage from the second amplifier controls the voltage output from the device whereby noise present in the output laser beam which modulates the output signal from the first amplifier is substantially eliminated.

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Altadena, CA, United States of America

Rudiger W Tietze