Television – Display or receiver with built-in test signal generator,... – Setup
Reexamination Certificate
2001-03-01
2004-02-03
Lee, Michael H. (Department: 2614)
Television
Display or receiver with built-in test signal generator,...
Setup
C348S181000
Reexamination Certificate
active
06686953
ABSTRACT:
FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
CD-R APPENDIX
This application includes a one-disk CD-R Appendix, the full contents of which are incorporated by reference herein. The disk contains the following files, listed by file name, creation date and file size in bytes: “ColorBlind Video Startup” created Jun. 22, 1999, 100K; “ColorBlind_Video_Startup.exe” created Sep. 16, 1999, 160K; “Complete_Text.txt” created Feb. 22, 2001, 40K; “Contents_of_CD.txt” created Feb. 22, 2001, 4K; “Lab Color Space Profile” created Aug. 4, 1997, 7K; “Prove it!” created Aug. 27, 1999, 4,116K; “Prove it! Installer” created Jul. 20, 1999, 2,251K; “Prove it_Beta.exe” created Jul. 16, 1999, 11,555K; and “Prove_it_Setup.exe” created Nov. 18, 1999, 7,432K.
FIELD OF THE INVENTION
This invention relates to the calibration of computer monitor displays, more particularly to a method of monitor calibration using target set screen displays and no supplemental light-measuring instrument.
BACKGROUND OF THE INVENTION
Introduction
The invention makes possible a new and superior method for calibrating visual display devices. When using computer systems to view, control and/or print graphics or photographs, it is often critically important that the computer displays be calibrated to a chosen standard condition.
Once a display (also called a “monitor,” particularly when referring to computer displays) is calibrated to a known state, techniques can then be employed to cause the display to accurately simulate the appearance of an image or graphic as it appears on, or when printed from, or as seen by another digital imaging device. Absent correct calibration, such simulations become inaccurate in like degree. The capability for accurate simulation is of tremendous importance to digital imaging in general. Therefore, display calibration is an important issue for many people.
The current invention can also be applied to the calibration of television set displays and all other types of analog or digital displays having many levels of intensity in each color channel—typically three channels, one each for red, green and blue.
The current invention is embodied in commercially available software for display calibration called ColorBlind Prove it! from ITEC Color Solutions, San Diego, Calif. The software exists in both Macintosh and Windows versions.
About the Prior Art for Visual Calibration
The prior art makes visual (instrumentless) calibration possible, but in no case does it teach a complete method for obtaining high-quality calibration. The prior art furthermore fails to address a variety of significant problems inherent in display calibration.
The Knoll Gamma version 2.0 application (see FIG.
2
), published by Adobe Systems Incorporated of San Jose, Calif., provides an incomplete system, which is capable of visual calibration of low to moderate quality.
U.S. Pat. No. 5,298,993 by Albert Edgar and James Kasson teaches certain useful principles of visual calibration, including the use of targets.
U.S. Pat. No. 5,638,117 by Peter Engledrum and William Hilliard uses areas of parallel lines in a visual characterization process.
The Default Calibrator application from Apple Computer, Inc. of Cupertino, Calif. (see FIG.
3
), which is a part of the program entitled ColorSync 2.5 and later, teaches a crude method for display calibration. This is prior art for only that part of the present invention called Gray Balance Method One (see
FIG. 11
, “Gray Balance Method One Target”). The three lined blended-region-and-solid sub-targets of
FIG. 3
are red, green and blue, from left to right.
The image file “Gamma_Estimation” (see FIG.
4
), from Candela, Ltd. (now Pictographics International Corporation) of Burnsville, Minn., teaches a method of identifying the current overall gamma from a broad range of possible overall gammas with the use of a gradient.
The image file “Current Gamma” (see FIG.
5
), published by Adobe Systems Incorporated of San Jose, Calif., in the program entitled PageMaker 6.5, teaches another method to identify the current overall gamma from a broad range of possible overall gammas.
The image file “Gamma 1.8.tif” (see FIG.
6
), also included with Adobe PageMaker version 6.5 software, from Adobe Systems Incorporated of San Jose, Calif., together with Knoll Gamma 2.0.1 and an explanatory text file entitled “Gamma Read Me,” teaches an improvement in the accuracy of the verification of a fixed gamma. However, “Gamma 1.8.tif” has significant limitations with regard to its ability to reliably reveal the correct gamma within each of several distinct subsegments of the tone scale because of the way in which tones were chosen to construct the target and the limited number of sub-targets used. “Gamma 1.8.tif” looks at six regions of the tone scale which all overlap a great deal and therefore can obscure the true nature of any observed departure from the gamma curve being sought, thus hindering efficient adjustment to achieve ideal gamma 1.8 tonality. Like all visual gamma adjustment targets, “Gamma 1.8.tif” also cannot be used to verify conformity of any display to other gamma curves, such as 2.2. The target of
FIG. 6
comprises various lined blended-region-and-solid sub-targets each having a repeating pattern comprising the alternation of a single lighter row with a single darker row (each row being the same height) juxtaposed with a gray solid region of a value between the lighter and darker values.
The Basic Elements of the Calibration Process
The standard condition to which a display is calibrated is defined partially by the inherent colors, or chromaticities, of the display's purest red, green and blue colors. In the case of a common CRT (cathode ray tube) type display, these colors of red, green and blue are determined primarily by the colors, or chromaticities, of the phosphors used in the tube. In the case of a flat panel display (FPD), these colors are determined by the mechanism of the display which created the primary colors, which is always different from that of CRTs.
The three other principal aspects of display calibration are not fixed by the nature of the hardware itself (that is, the display or monitor). These three other aspects of display calibration are:
1) Calibrating the white point, i.e. the color of the display's white (independent of its brightness), also known as its Hue and Chroma, also known as its x,y coordinates from the X+Y+Z=1 plane of the CIE XYZ color space;
2) Calibrating its gray balance so that each gray that it displays—from black (the darkest color the display can display in a given state of calibration) all the way to white (the brightest color the display can display in a given state of calibration)—has the same color as the white (also known as the same Hue and Chroma, also known as the same x,y coordinates); and
3) Calibrating the “gamma” or tone curve of the display so that the way it displays the full range of input values from black to white follows the desired progression of luminous intensities. Typically, the full range of digital input values sent from the computer's video circuitry to the display is the range from RGB (
0
,
0
,
0
) to RGB (
255
,
255
,
255
) where each color channel has a range of 256 (two to the eighth power) values. Gamma curves are a subset of all possible tone curves and have certain mathematical properties. Displays generally need to be calibrated to a gamma curve to function properly as a calibrated display in a color managed system of imaging devices.
Two other aspects of display calibration are:
1) Calibration of absolute white intensity; and
2) Calibration of absolute black intensity.
In addition to the aspects of display calibration mentioned above, there are particular adjustments of so-called hardware controls, such as the Brightness, Contrast, Color, Bias, and Gain controls on CRT displays, which adjustments affect and/or are part of the processes of calibration mentioned above. The affected processes include calibration of the white point, the gray balance, the gamma,
Johnson Larry D.
Johnson & Stainbrook LLP
Lee Michael H.
Stainbrook Craig M.
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