Exposure control for a CCD scanner
AssigneeHewlett-Packard Development Company, L.P.
InventorPaul L Jeran
Life of this patent
Estimating the term…
Abstract
A scanner is disclosed that operates to maintain the image sensor in the scanner at a proper exposure level during the scanning of a page despite variations in the scan rate. The scanner includes an illumination system operable to produce light in response to receiving power and to project the light, as a scanning light, onto the page being scanned. In addition, the scanner includes apparatus for moving the scanning light relative to the page at a scan rate, an image sensor for measuring the light reflected from the page and an exposure control device for controlling the exposure of the image sensor. The exposure control device operates to control the exposure of the image sensor by regulating the power in relationship to the scan rate.
Claims20
A page scanner, comprising:
- an illumination system for producing light in response to receiving power from a power source and for projecting said light onto said page;
- means for moving said projected light relative to said page at a variable scan rate;
- an image sensor for measuring light reflected from said page;
- and
- means for controlling exposure of said image sensor to said reflected light by regulating said power in relationship to said variable scan rate;
- wherein the exposure controlling means operates to increase, while the page is being scanned, said power when the scan rate is increased;
- and
- wherein the exposure controlling means operates to decrease, while the page is being scanned, said power when the scan rate is decreased.
An illumination system for a digital scanner, said digital scanner capable of scanning a page by using said illumination system to project a scanning light onto said page and to move said scanning light relative to said page at a scan rate while exposing an image sensor to light reflected from said page, said illumination system comprising:
- a light source operable to produce said light in response to receiving power;
- a drive circuit operable to apply power to said light source;
- and
- means for regulating said power in relationship to said scan rate so as to control the exposure of said image sensor while a page is being scanned;
- and
- wherein the regulating means operates to increase said power when the scan rate is increased and to decrease the power when the scan rate is decreased.
A method of operating a page illumination system for a page scanner capable of scanning said page by using said illumination system to project a scanning light onto said page and to move said scanning light relative to said page at a scan rate while exposing an image sensor to light reflected from said page, said method comprising:
- providing a light source operable to produce said light in response to receiving power;
- applying power to said light source;
- and
- regulating said power as a function of said scan rate while said page is being scanned.
Dependencies are inferred from the claim text.