Method and apparatus for processing colorimetric parameters of a color sample

• US 4,875,032 A
• Filed: 10/26/1987
• Issued: 10/17/1989
• Est. Priority Date: 10/26/1987
• Status: Expired due to Fees

• Current Assignee: Tektronix Incorporated (Fortive Corp.)
• Original Assignee: Tektronix Incorporated (Fortive Corp.)
• Inventors: Beaton, Robert J., McManus, Paul A.
• Primary Examiner(s): Brigance, Gerald
• Assistant Examiner(s): HJERPE, RICHARD A
• Application Number:
  US07/113,022
• Time in Patent Office: 722 Days
• Field of Search: 340/701, 340/703, 340/793, 358/75, 358/78, 358/80, 358/76
• US Class Current: 345/603
• CPC Class Codes: H04N 17/04 for receivers
• CPC Class Codes: H04N 9/73 Colour balance circuits, e.g. white balance circuits or colour temperature control camera processing pipelines for colour balance H04N23/88

Abstract

The colorimetric parameters of a color sample (42) that is illuminated by a reference light are processed for reproduction by a video monitor (20) or the like. A color filter assembly (40) and associated sensor (28) are used to generate signals indicative of the colorimetric parameters of the illuminated color sample (42). A computer (24) transforms the signals into a form suitable for driving a video monitor (20) to reproduce the color sample (42) on the monitor screen.

Claims

1. A method for processing colorimetric parameters of a color sample for reproducing the color of the sample on a video monitor screen, wherein the color sample is illuminated by a reference light having tristimulus values and is definable by a primary intensity vector denoting relative first color, second color and third color luminous intensity levels of the illuminated color sample, and wherein the video monitor includes a plurality of phosphor sets, the luminous intensity of the phosphor sets being variable to produce colors on the monitor screen, any particular color produced on the monitor screen being definable by a phosphor intensity vector that denotes the relative values of the luminous intensity levels of the phosphor sets at the time the particular color is produced on the monitor screen, the method comprising the steps of:

(a) directing through each of three color filters a source light having tristimulus values representing a standard CIE illuminant, and generating a color filters matrix representative of the relative intensity contributions of each filter color to the tristimulus values of the source light;

(b) directing the reference light through each of the color filters, and generating a reference primary vector representative of the relative primary intensity contribution of each filter color to the reference light;

(c) weighting the color filters matrix to reflect the differences between the tristimulus values of the source light and the tristimulus values of the reference light;

(d)detecting the primary intensity vector of the color sample; and

(e) multiplying the detected primary intensity vector of the color sample and the weighted color filters matrix to generate the tristimulus values of the color sample.

2. The method of claim 1 further comprising the steps of:

(a) generating an XYZ-to-RGB matrix for reversibly transforming tristimulus values of a color into a corresponding phosphor intensity vector; and

(b) multiplying the tristimulus values of the color sample and the XYZ-to-RGB matrix to generate the phosphor intensity vector that defines the color sample.

3. A system for processing the colorimetric parameters of a color sample for reproducing the color of the sample on a video monitor screen, wherein the color sample is illuminated by a reference light having tristimulus values and is definable by a primary intensity vector denoting the relative first color, second color and third color luminous intensity levels of the illuminated color sample, and wherein the video monitor includes a plurality of phosphor sets, the luminous intensity of the phosphor sets being variable to produce colors on the monitor screen, any particular color produced on the monitor screen being definable by a phosphor intensity vector that denotes the relative values of the luminous intensity levels of the phosphor sets at the time the particular color is produced on the monitor screen, the system comprising:

(a) a color filter assembly having a first color filter, a second color filter and a third color filter arranged so that each filter filters light passing therethrough into corresponding first, second and third primaries;

(b) sensing means for detecting the intensity of the first, second and third primaries and for generating intensity signals representative of the detected intensities; and

(c) processing means coupled to the sensing means to receive the intensity signals and for

(1) generating a color filters matrix based upon intensity signals generated by the sensing means as source light having tristimulus values representing a standard CIE illuminant is filtered by each filter into first, second and third primaries, the color filters matrix being representative of the relative intensity contribution of the first, second and third primaries of the source light to the tristimulus values of the source light;

(2) generating a reference primary vector based upon intensity signals generated by the sensing means as reference light is filtered by each filter into first, second and third primaries, the reference light primary vector being representative of the relative primary intensity contribution of the first, second and third primaries of the reference light to the reference light;

(3) weighting the color filters matrix to reflect the differences between the tristimulus values of the source light and the tristimulus values of the reference light;

(4) multiplying the primary intensity vector of the color sample that is detected by the sensing means with the weighted color filters matrix to generate tristimulus values for the color sample.

4. The system of claim 3 wherein the processing means includes conversion means for converting the tristimulus values of the color sample into a corresponding phosphor intensity vector for the color sample.