Method and system for displaying colors utilizing tristimulus values

• US 4,379,292 A
• Filed: 12/04/1980
• Issued: 04/05/1983
• Est. Priority Date: 02/22/1978
• Status: Expired due to Term

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Minato, Sachie, Kamata, Haruo
• Primary Examiner(s): Trafton, David L.
• Application Number:
  US06/213,116
• Time in Patent Office: 852 Days
• Field of Search: 315/11, 315/12 R, 315/12 ND, 315/383, 358/10, 358/29, 358/80, 340/701, 340/703
• US Class Current: 345/603
• CPC Class Codes: H04N 1/6011 with simulation on a subsidiary picture reproducer H04N1/622 takes precedence; matching two or more picture reproducers H04N1/6052
• CPC Class Codes: H04N 1/6033 using test pattern analysis H04N1/6055 takes precedence
• CPC Class Codes: H04N 23/84 for processing colour signals
• CPC Class Codes: H04N 9/64 Circuits for processing colour signals H04N9/77 takes precedence; camera processing pipelines for processing colour signals H04N23/84

Abstract

A color displaying method comprises determining the CIE (Commission Internationale d'"'"'Eclairage) tristimulus values of a desired color to be displayed. The tristimulus values are converted into corresponding electrical signals in accordance with the relative luminance value of the source of radiations employed to produce the desired color. A system for displaying colors is also disclosed which includes an electro-optical color imaging device. The tristimulus values of the desired color are generated in a computer in response to a set of numerical data keyed through a data input device. The tristimulus values are converted into corresponding electrical signals which are then corrected in amplitude in accordance with the emission characteristics of the imaging device. The latter is driven in response to the amplitude-corrected electrical signals to produce the desired color. The electrical signals are amplitude corrected by having the imaging device produce a white light emission on a specified area of its imaging surface. A spectral analyzer analyzes the spectral components of the emitted white light to generate a set of signals representing the tristimulus values of the imaging device white light. The so-obtained tristimulus signals are compared with a set of reference signals representing the tristimulus value of a reference white light to generate a set of error signals, representing the differences between the imaging device white light and the reference white light, which are subtractively combined with the signals representing the tristimulus values of the desired color.

Claims

1. A method for displaying a desired color, said method comprising the steps of:

(A) converting in a computer the tristimulus values of a desired color into corresponding electrical signals;

(B) providing said so-converted electrical signals to a color display means that displays a color representative of the desired color in a color display area in response to said so-provided electrical signals;

(C) causing said color display means to display a reference light in a display area thereof other than said color display area;

(D) determining the tristimulus values of said reference light;

(E) generating tristimulus values representative of a predetermined standard light, said generating step being independent of step (C);

(F) comparing the so-determined tristimulus values of said reference light with said tristimulus values representative of said predetermined, standard light;

(G) generating in said computer an error signal representative of the compared difference between said tristimulus values of said reference light and said predetermined standard light; and

(H) combining said error signal with said electrical signals representative of the tristimulus values of the desired color to correct the displayed color for the differences between the reference light provided by said display means and said predetermined standard light.

2. The method claimed in claim 1 further comprising, prior to the step of converting, the steps of:

providing input information representative of a desired color in accordance with a first color specification system; and

converting said so-provided input information into equivalent tristimulus values.

3. The method claimed in claim 2 wherein said providing step includes:

providing input information defining the desired color in terms of the hue, chroma, and value of the Munsell color system.

4. The method claimed in claim 1 wherein said reference light is a white light.

5. The method of claim 1 wherein said determining step further comprises the steps of:

(A.1) imaging the reference light on an optical analyzing means;

(A.2) causing said optical analyzing means to optically analyze the so-imaged reference light to provide electrical signals representative of the reference light tristimulus values.

6. The method claimed in claim 5 wherein said comparing step further comprises:

(E.1) providing an electrical signal representative of the tristimulus values of said predetermined standard light; and

(E.2) comparing the electrical signals representative of the tristimulus values of said predetermined standard light with the electrical signals representative of the tristimulus values of said analyzed reference light.

7. A system for displaying color comprising:

display means for generating and displaying an image including a reference light image in a first display area of said display means and a color image in another display area of said display means in response to applied electrical signals;

information input means connected to said display means for receiving, as an input, information representative of a desired color to be displayed and for converting said input information into said applied electrical signals to cause said display means to generate and display in the other display area a color representative of said input information;

analyzing means optically coupled to said display means for analyzing the reference light image and providing analyzed values representative thereof;

standard means independent of said analyzing means for continuously producing standard values which represent a predetermined standard light;

comparator means for continuously comparing said analyzed values and said standard values and for producing error signals representative of the difference between said analyzed values and said standard values, said error signals being provided to said display means for modifying said applied electrical signals in accordance with the difference between the reference light image values and said predetermined standard image value.

8. The system claimed in claim 7 wherein:

said reference light provided by said display means is a white light.

9. The system claimed in claim 7 wherein:

said display means includes a display surface having an ordered matrix of red, green, and blue color emitters, said emitters selectively responsive to said applied electrical signals to emit their respective colors to generate the primary and secondary colors in accordance with said input information and to generate said reference light area.

10. The system claimed in claim 9 wherein said display means comprises:

a cathode ray tube means having an ordered matrix of red, green, and blue phosphers selectively caused to emit light in response to electron beam irradiation.

11. The system claimed in claim 7 wherein:

said input information is the hue, chroma, and value of the desired color in the Munsell color system.

12. The system claimed in claim 11 wherein:

said information input means converts said input information into the red, green, and blue tristimulus values of said input information.

13. The system claimed in claim 7 wherein said analyzing means comprises:

a spectral component analyzer for receiving light from said reference light image and analyzing said reference light image to provide the tristimulus values of said received reference light image,

and wherein said standard means provides tristimulus values of said predetermined standard light.

14. The system claimed in claim 13 wherein:

said comparator means compares the soanalyzed tristimulus values of said reference light with said tristimulus values of a predetermined standard light and provides said error signals representative of the difference between the emission characteristics of said display means and said predetermined standard light.

15. A color display system comprising:

a data input device for keying a set of numerical data;

first means for generating a set of first electrical signals representing the tristimulus values of a desired color in response to said keyed numerical data; and

second means for generating radiations of different basic colors in response to said electrical signals;

said first means comprising a plurality of comparators 14, 15, 16 each having a first input terminal receptive of a respective one of said first electrical signals and a second input terminal receptive of an error correction signal to generate a set of second electrical signals X_c '"'"', Y_c '"'"', Z_c '"'"',

said second means comprising a cathode ray tube 18 having a plurality of electron beam generating means and a plurality of light emissive areas for generating radiations of different wavelengths in response to impingement of the electron beams thereo, means 12 for converting said second electrical signals in accordance with the emission characteristics of said light emissive areas to modulate the intensity of said electron beams, means for causing said electron beams to produce a white light in a specified area 21 of said cathode ray tube screen, means for deflecting the intensity modulated electron beams to produce an image which is a blend of said radiations of different wavelengths in different areas of said cathode ray tube screen, a spectral component analyzer 23 for analyzing the spectral components of said white light for generating a set of third electrical signals Xw'"'"', Yw'"'"', Zw'"'"' representing the tristimulus values of said white light, a plurality of second comparators each having a first input terminal receptive of a respective one of said third electrical signals Xw'"'"', Yw'"'"', Zw'"'"' and a second input terminal receptive of a respective one of a set of reference signals Xw, Yw, Zw representing the tristimulus values of a reference white light to generate a set of fourth electrical signals Δ

Xw, Δ

Yw, Δ

Zw representing the difference between said third and reference signals, and means for multiplying said fourth electrical signals by the inverse matrix of a set of said input data to generate a set of fifth electrical signals Δ

α

_1w, Δ

α

_2w, Δ

α

_3w for application to the second input terminals of said first comparators.

16. A method of color control in a visual display using a cathode ray tube which has a separate electron source for each of three primary colors comprising:

(a) inputting values for Hue, Value and Chroma according to the Munsell color system into a computer from a data input device;

(b) determining the tristimulus values for each of the three primary colors in said computer corresponding to the Munsell color system values inputted to the computer;

(c) using the determined tristimulus values to produce signals and energizing said electronic sources with said signals;

(d) focusing at a given position on the screen of said cathode ray tube, the beams produced by each of said electron source to produce a white spot;

(e) analyzing said white spot and producing tristimulus values for each of said three primary colors;

(f) generating tristimulus values for each of said three primary colors which values represent absolute white, said step of generating being independent of step (e);

(g) continuously comparing in said computer each of the tristimulus values obtained in step (e) with said values obtained in step (f) which represent absolute white;

(h) producing error signals for each of the three primary colors determined from the comparison of step (e);

(i) modifying the values determined by said computer in step (b) using said error signals;

(j) repeating step (c) using the modified values obtained in step (i) in place of the original values used in step (c); and

(k) repeating steps (d) to (j).