Apparatus and method for correcting offset and gain drift present during communication of data
First Claim
1. A method for correcting gain drift in a fast scan direction during an image forming process in an image apparatus having image sensors including a plurality of active pixels and permanently darkened pixels and control circuitry therefor, comprising the steps of:
- (a) sampling the plurality of active pixels during a scanning of a calibration strip;
(b) calculating a gain corrective value from the samples collected during the scanning of the calibration strip;
(c) sampling the active pixels during scannings of a platen background;
(d) calculating a difference between sequential samples of the active pixels during the scannings of the platen background; and
(e) adjusting continually the gain corrective value according to the difference and applying the adjusted gain corrective value to image data signals produced by active pixels.
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Accused Products
Abstract
The present invention is directed to a system and method for compensating for offset and gain drift in a fast scan direction during an image forming process. To achieve compensation, the present invention samples a plurality of permanently darkened pixels upon powering up image sensors and circuitry therefor and during a sub-scanning process of an image and feeds this information into an offset value generating circuit. The offset generating circuit continually adjusts a pixel offset voltage according to a difference between sequential samples of the permanently darkened pixel, thereby compensating for fast scan offset drift. The present invention also samples a plurality of active pixels during a scanning of a calibration strip. From this scan, a gain corrective value is calculated. The present invention then samples active pixels during a scanning of a platen background. In response to this sampling, the gain corrective value is continually adjusted according to a difference between sequential samples of the platen background, thereby compensating for fast scan gain drift. The present invention can also compensate and balance transfer functions for a plurality of communication channels in a multi-channel system by using the same target values and same reference signals for each channel.
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Citations
28 Claims
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1. A method for correcting gain drift in a fast scan direction during an image forming process in an image apparatus having image sensors including a plurality of active pixels and permanently darkened pixels and control circuitry therefor, comprising the steps of:
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(a) sampling the plurality of active pixels during a scanning of a calibration strip; (b) calculating a gain corrective value from the samples collected during the scanning of the calibration strip; (c) sampling the active pixels during scannings of a platen background; (d) calculating a difference between sequential samples of the active pixels during the scannings of the platen background; and (e) adjusting continually the gain corrective value according to the difference and applying the adjusted gain corrective value to image data signals produced by active pixels. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A system for balancing an offset characteristic for a multi-channel system in an image apparatus having image sensors including a plurality of active pixels and permanently darkened pixels and control circuitry therefor, comprising:
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first means for sampling an output of each channel; channel offset means for generating and applying a separate channel offset voltage to each channel, said channel offset voltage continually changing according to sequential samples of each channel, thereby balancing an offset characteristic of the multi-channel system; sampling means for sampling the plurality of permanently darkened pixels upon powering up the image sensors and the control circuitry therefor and during a fast scan of an image; first difference means for calculating a difference between sequential samples of the permanently darkened pixels upon powering up the image sensors and control circuitry therefor and during the fast scan of the image; pixel offset means for generating and applying a pixel offset voltage to image data signals produced by the plurality of active pixels according to the difference between sequential samples of the permanently darkened pixel; said sampling means sampling a plurality of active pixels during a scanning of a calibration strip; second means, operatively connected to said sampling means, for calculating a gain corrective value from the samples collected during the scanning of the calibration strip; said sampling means sampling the active pixels during scannings of a platen background; second difference means for calculating a difference between sequential samples of the active pixels during the scannings of the platen background; pixel gain means for continually adjusting the gain corrective value according to the difference between sequential samples of the platen background.
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8. A system for correcting gain drift in a fast scan direction during an image forming process using a platen background in an image apparatus having image sensors including a plurality of active pixels and permanently darkened pixels and control circuitry therefor, comprising:
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sampling means for sampling the plurality of active pixels during a scanning of a calibration strip; first means, operatively connected to said sampling means, for calculating a gain corrective value from the samples collected during the scanning of the calibration strip; said sampling means sampling the active pixels during scannings of the platen background; first difference means for calculating a difference between sequential samples of the active pixels during the scannings of the platen background; pixel gain means for adjusting said gain corrective value according to the difference between sequential samples of the platen background and applying the adjusted gain corrective value to image data signals produced by active pixels. - View Dependent Claims (9, 10, 11, 12, 13)
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14. A system for balancing a gain characteristic for a multi-channel system in an image apparatus, comprising:
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first means for sampling an output of each channel; channel gain means for generating and applying a separate channel gain to each channel, said channel gain continually changing according to sequential samples of each channel, thereby balancing a gain characteristic of the multi-channel system; sampling means for sampling a plurality of active pixels during a scanning of a calibration strip; second means, operatively connected to said sampling means, for calculating a gain corrective value from the samples collected during the scanning of the calibration strip; said sampling means sampling the active pixels during scannings of a platen background; first difference means for calculating a difference between sequential samples of the active pixels during the scannings of the platen background; and pixel gain means for continually adjusting the gain corrective value according to the difference between sequential samples of the platen background. - View Dependent Claims (15, 16)
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17. A method for correcting a gain characteristic for a communication channel of a video system, comprising the steps of:
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(a) injecting a channel white reference signal onto a channel; (b) sampling an output of the channel downstream of a point where the channel white reference signal was injected in said step (a); (c) calculating a gain value for the channel in accordance with the output sampled in said step (b); (d) applying a gain to the channel according to the calculated gain value, thereby correcting a gain characteristic of the channel; (e) sampling an initial output from a plurality of active pixels produced as a result of scanning a calibration strip; (f) calculating a gain corrective value from the output sampled in said step (e); (g) sampling an output from each active pixel produced as a result of scannings of a platen background between complete scannings; (i) determining changes between sequential samples of the active pixels during the scannings of the platen background; and (i) adjusting the pixel gain corrective value according to the changes in the sampled output of step (g). - View Dependent Claims (18, 19, 20, 21, 22, 23)
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24. A method for correcting an offset characteristic for a communication channel of a video system, comprising the steps of:
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(a) injecting a channel black reference signal onto a channel; (b) sampling an output of the channel downstream of a point where the channel black reference signal was injected in said step (a); (c) calculating an offset value for the channel in accordance with the output sampled in said step (b); (d) applying an offset voltage to the channel according to the calculated offset value, thereby correcting an offset characteristic of the channel; (i) sampling an initial output from each active pixel produced as a result of scanning a calibration strip; (j) calculating a gain corrective value from the output sampled in said step (i); (k) storing the gain corrective value; (l) sampling an output from each active pixel produced as a result of an initial scanning of a background; (m) calculating an average claim value from the output sampled in said step (k); (n) storing the average gain value as a reference value; (o) sampling an output from each active pixel produced as a result of a scanning of a background between complete scannings of an image; (p) calculating an average gain value from the output sampled in said step (o); (q) determining a difference between the stored reference value and the average gain value calculated in said step (p); and (r) adjusting the gain corrective value according to the difference determined in said step (q). - View Dependent Claims (25, 26, 27, 28)
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Specification