Shading compensation for scanning apparatus

Details Shading compensation for scanning apparatus Shading compensation for scanning apparatus

H - Electricity

04

N

350/16, 400/6304

H04N 1/38 (2006.01) H04N 1/40 (2006.01)

Patent

CA 1181841

-1- ABSTRACT OF THE DISCLOSURE An image input terminal (IIT) with automatic document handler for feeding documents to be scanned into registered position on the IIT platen. The IIT includes a pair of multi-element scanning arrays with cooperating scan lamp and optics on a movable carriage disposed in scanning relationship with the platen. Analog image signals gener- ated by the scanning arrays are initially processed in separate channels and then combined into a serial stream. The stream of analog image signals may optionally be thresholded or screened to provide binary level image signals or converted to multi-bit gray scale. A control system including microprocessor provides timing and control signals for synchronizing operation of the scanning carriage, document handler, and image signal reading and processing together with elec- tronic crossover between arrays to avoid loss of data, automatic signal gain control, and deletion of bad image signals or pixels. A defocused calibration strip is scanned to provide shading signals for calibrating the individual scanning elements of the arrays, the shading signals being processed in successive blocks each of which comprises a preset number of shading signals. Following processing, the shading signals are stored in memory and accessed during normal scanning. The shading signals are employed in all operational modes to compensate the image signals produced by the IIT for deficiencies in the scanning com- ponents.

432786

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