Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1990-08-13
1991-06-25
Hix, L. T.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
35821316, G03B 1300
Patent
active
050271482
ABSTRACT:
The present invention is an autofocus chip which produces reference levels or voltages from CCD charge sources rather from voltage sources chip. The CCD sensor of the chip has normal photodiodes and bright diodes. A high voltage reference is produced from the maximum charge or full well level of one of the bright diodes of the sensor, stored and used as the high reference of an A/D converter in the chip. The reference traverses the same path as the image values produced by the photodiodes. A low voltage reference for the A/D converter is produced by storing the reset level voltage of the bright diode or of each pixel. Correlated double sampling for each pixel is accomplished when the low reference level in the A/D converter is updated with the reset value of each pixel. The reset level also traverses the same path as the image signals. By setting the high reference level each time the chip is enabled and the low reference level for each pixel, the reference levels are adapted to the environmental changes experienced by the chip or to changes due to manufacturing tolerances. The bright diode level is used to determine the integration time for the sensor during an autofocus operation by comparing the charge in the bright diode with the photodiode having the largest charge.
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Dugas Edward
Eastman Kodak Company
Gray David M.
Hix L. T,.
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