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US 7,889,251 B1Granted
Method and device for white level calibration
AssigneeNational Semiconductor Corporation
InventorsChung Wai Ng, David Boisvert, Kunhong Qu, Mehmet Aslan
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Abstract
Calibrating a white level in an image scanning device. A target white level is accessed. A high white level is determined for pixel data output by an amplifier. A gain adjustment to the amplifier is determined to correct a portion of an error between the target white level and the high white level. The gain adjustment is applied to the amplifier.
Claims15
A method of calibrating a white level in an image scanning device, said method comprising:
- a) accessing a target white level in said image scanning device;
- b) determining a high white level for pixel data output by an amplifier, wherein said pixel data output is obtained by scanning white reference data;
- c) determining a gain adjustment for said amplifier to correct an error between said target white level and said high white level, wherein said gain adjustment is based on a change in said high white level, and wherein said gain adjustment is not yet applied to said amplifier;
- d) determining a single gain factor, wherein said single gain factor is applied to said gain adjustment such that said gain adjustment when applied to said amplifier will correct a portion of said error, wherein said portion is less than the entire said error, wherein said determining said single gain factor comprises accessing a first value from a pattern of predetermined values, wherein said predetermined values are in a predetermined order;
- and
- e) applying said gain adjustment with said single gain factor to said amplifier;
- further comprising, after applying said gain adjustment to said amplifier:
- f) determining a new high white level for pixel data output by said amplifier;
- g) determining a new gain adjustment to correct an error between said target white level and said new high white level, and wherein said new gain adjustment is not yet applied to said amplifier;
- h) determining a new single gain factor, wherein said new single gain factor is applied to said new gain adjustment such that said new gain adjustment when applied to said amplifier will correct a portion of said error, wherein said portion is less than the entire said error, wherein determining said new single gain factor comprises accessing a second value from said pattern of predetermined values, wherein said second value is the next value in said pattern of predetermined values after said first value;
- and
- i) applying said new gain adjustment with said new single gain factor to said amplifier.
9 more elements
A white level calibration device, said device comprising:
- an amplifier that is operable to receive and amplify pixel data;
- a high white level logic that is operable to receive amplified pixel data from said amplifier and is further operable to determine a high white level of said amplified pixel data;
- and
- a gain calibration logic that is operable to calculate a gain adjustment for said amplifier to correct an error between a target white level and said high white level, wherein said target white level is a value stored in a register of said device, and wherein said gain adjustment is based on a change in said high white level, and wherein said calculated gain adjustment is not yet applied to said amplifier, and wherein said gain calibration logic is operable determine a first gain adjustment for said amplifier to correct a portion of said error between said target white level and said high white level, wherein said portion is less than the entire said error, wherein said portion is based on a gain factor, wherein said gain adjustment is based on a change in said high white code level, wherein said gain calibration logic is further operable to program said amplifier to implement said first gain adjustment prior to receiving additional pixel data, and wherein prior to determining a second gain adjustment for said additional pixel data, modifying said gain factor based on an analysis of results of applying said first gain adjustment for said pixel data.
1 more element
A method of calibrating a white level in an image scanning device, said method comprising:
- accessing a target white code level in said image scanning device;
- determining a gain correction factor;
- for a plurality of scan lines of a white reference region of a scan page performing the following:
- receiving one of said scan lines of said white reference region as pixel data;
- amplifying said pixel data with a programmable amplifier;
- digitizing said pixel data after said amplifying to generate white codes;
- determining a high white code level of said white codes;
- determining a gain adjustment for said programmable amplifier to correct a portion of an error between said target white code level and said high white code level, wherein said portion is less than the entire said error, wherein said portion is based on said gain correction factor, and wherein said gain adjustment is based on a change in said high white code level;
- and
- programming said programmable amplifier to implement said gain adjustment prior to receiving another of said scan lines, wherein prior to determining a gain adjustment for a second of said scan lines, modifying said gain correction factor based on an analysis of results of applying said gain adjustments for a first of said scan lines.
7 more elements
Dependencies are inferred from the claim text.