Facsimile and static presentation processing – Natural color facsimile – Scanning
Reexamination Certificate
1996-05-23
2001-04-24
Grant, II, Jerome (Department: 2624)
Facsimile and static presentation processing
Natural color facsimile
Scanning
C358S513000
Reexamination Certificate
active
06222649
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to color image sensor devices such as image scanners, facsimile machines and copy machines, and in particular relates to compression techniques in conjunction with such image acquisition devices.
Many different types of devices exist for sensing color images. These can be desktop or hand held scanners, copy machines, facsimile machines, or other devices. A number of different methods are used. In one, a fluorescent lamp is used to illuminate the image, with different color filters being positioned to intercept either the transmitted or reflected light before it is sensed. Alternately, multiple fluorescent lamps with their own dedicated filters used for emitting different colors of light could be used. In yet other devices, instead of fluorescent lamps, light-emitting diodes (LEDs) are used, with different LEDs having different color emissions. For example, a typical configuration might have three types of LEDs, one in the blue range of wavelengths, another in the green range of wavelengths, and another in the red range of wavelengths.
One problem with existing scanning techniques is the large amount of data that needs to be acquired and stored or transmitted to a computer. Typically, each pixel in the image must be digitized three (or more) times, for each of the desired color components (RGB). This consumes a significant amount of time for scanning the image, and also requires a large amount of data be stored or transmitted. In a typical embodiment, each line of the image is read first with red light, then with green, then with blue, and then the scanner moves on to the next line. Existing compression methods require additional time to reduce the amount of data actually stored or transmitted.
SUMMARY OF THE INVENTION
The present invention provides a method and apparatus for compressing a color image by reducing the amount of color information initially acquired. The color information can later be restored by interpolation from other portions of the image where the color information is available. This not only reduces the amount of data that needs to be stored, but improves the scanning time for an image scanner by reducing the amount of time needed to scan the image. In a preferred embodiment, both the scanning time and the amount of data can be cut in half.
In one embodiment, a color scanner has red, green and blue LEDs which are alternately activated in a normal mode to illuminate each line of an image. In the present invention, not all three colors are illuminated for each line. In one embodiment, only luminance information is obtained by activating all three LEDs simultaneously for most lines, and then periodically sampling (such as every fourth line) the individual R, G and B components.
Alternately, the red can be activated for one line, the green for a subsequent line, and the blue for another subsequent line. The green and blue color information for the first line can later be interpolated from the second and third line values. Other combinations of luminance only, full color, and individual colors can be used to generate the time and data bandwidth savings of the present invention.
The present invention recognizes that the human eye is more sensitive to the luminance component at a higher resolution than the chrominance component of an image. Accordingly, less chrominance information than luminance information can be acquired without noticeable impact on image quality.
REFERENCES:
patent: 3716286 (1973-02-01), St John et al.
patent: 4658289 (1987-04-01), Nagano et al.
patent: 4992860 (1991-02-01), Hamaguchi
patent: 5550653 (1996-08-01), Te Winkle
patent: 5729361 (1998-03-01), Suggs
Lavelle Mark T.
Suggs Bradley N.
Grant II Jerome
Silitek Corporation
Townsend and Townsend / and Crew LLP
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