Patent ID: 7889251

Claim:
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.