Color corrector in an apparatus for producing color image

• US 5,303,071 A
• Filed: 06/07/1993
• Issued: 04/12/1994
• Est. Priority Date: 12/25/1990
• Status: Expired due to Fees

• Current Assignee: Victor Company of Japan Limited (JVC Kenwood Corporation)
• Original Assignee: Victor Company of Japan Limited (JVC Kenwood Corporation)
• Inventors: Kakimura, Yoshiaki
• Primary Examiner(s): Coles, Sr., Edward L.
• Assistant Examiner(s): VU, KIM Y
• Application Number:
  US08/073,282
• Time in Patent Office: 309 Days
• Field of Search: 358/518, 358/519, 358/520, 358/30, 358/32, 358/34, 358/172, 358/21 R, 358/54, 358/214, 358/527
• US Class Current: 358/519
• CPC Class Codes: H04N 1/60 Colour correction or control H04N1/54 takes precedence
• CPC Class Codes: H04N 1/6016 Conversion to subtractive 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 corrector for correcting chromaticity of a color image to be reproduced is provided in a color printer or a CRT display device for reproducing a color image from respective signals corresponding to predetermined primary colors of a plurality of primary colors constituting the color image. This color corrector comprises: a corrective operation circuit for executing an operation between a color correction coefficient matrix and signals corresponding to the primary colors to correct relative levels of the signals corresponding to the primary colors; a gray component extraction circuit for making level comparison between the signals corresponding to the primary colors to thereby extract a gray component; a correction signal output circuit for executing an operation between the extracted gray component and correction coefficients determined by the matrix to output gray balance correction signals every primary colors; and an adding circuit for adding signals of which levels are corrected in correspondence with respective primary colors outputted from the corrective operation circuit to outputs from the correction signal output circuit.

Claims

1. A color corrector provided in an apparatus for reproducing a color image from respective signals corresponding to predetermined primary colors of a plurality of primary colors constituting said color image, and adapted for correcting chromaticity of a color image reproduced,

said color corrector at least comprising:

corrective operation means adapted to execute a predetermined operation between a color correction coefficient matrix and signals corresponding to said primary colors to thereby correct relative levels of signals corresponding to said primary colors;

gray component extraction means adapted to make a level comparison between signals corresponding to said primary colors to thereby extract a gray component;

correction signal output means adapted to execute an operation between the extracted gray component and correction coefficients corresponding to said respective primary colors determined by said color correction coefficient matrix to thereby output gray balance corrected signals for every said primary colors; and

means for adding the level corrected signals corresponding to said respective primary colors outputted from said corrective operation means and outputs from said correction signal output means.

2. A color corrector as set force in claim 1, wherein said color corrector is provided in a color printer for reproducing a color image by the subtractive mixture of colors,

said color corrector comprising:

a color masking circuit adapted to implement a signal processing based on a color masking matrix to three primary signals of a color image to carry out conversion to recording density signals of three colors complementary to said three primary color signals;

a maximum level primary color signal selection circuit for selecting a signal of which level is maximum from said three primary color signals;

a plurality of multiplying circuits correspondingly provided every rows of said color masking matrix of said color masking circuit, and for implementing a predetermined signal processing to each of output signals from said maximum level primary color signal selection circuit on the basis of color correction coefficients in a direction of respective rows of said color masking matrix; and

adding circuits for adding outputs from said multiplying circuits correspondingly provided every said respective rows of said color masking matrix to recording density signals of said three primary complementary colors serving as outputs from said color masking circuit.

3. A color corrector as set force in claim 2, wherein said corrector for said color printer further comprises:

three input terminals provided in correspondence with respective colors of said three primary colors, three primary color video signals of said color image being applied to said three input terminals, respectively;

an inverse γ

-correction/logarithmic conversion circuit for implementing inverse γ

-correction and logarithmic conversion to three primary color video signals inputted through said input terminals; and

three wide-band amplifying circuits every respective primary colors for amplifying respective output signals relating to three primary color video signals outputted from said conversion circuit to output them to the sides of said color masking circuit and said selection circuit.

4. A color corrector as set forth in claim 3, wherein said color corrector for said color printer further comprises;

three clamping circuits respectively provided every primary colors between said wide-band amplifying circuits for said primary color video signals and said maximum level primary color signal selection circuit, and serving to allow pedestal levels of output signals from said respective amplifying circuits to match with each other.

5. A color corrector as set force in claim 1, wherein said color corrector is provided in a Cathode Ray Tube (CRT) for reproducing a color image by the additive mixture of colors,

said color corrector comprising:

a matrix operation circuit for implementing matrix operation based on color correction coefficients to three primary color signals of a color image to output three signals color-corrected every respective primary colors;

a minimum level primary color signal selection circuit for determining a minimum level of each of said three primary color signals to thereby extract a gray component included in said respective signals;

a multiplying circuit for multiplying the gray component extracted by said minimum level primary color selection circuit by correction coefficients determined on the basis of said color correction coefficients to determine and output correction signals of the gray component for said respective color signals; and

an adding circuit for adding said correction signals of the gray components for said respective color signals outputted from said multiplying circuit to color-corrected signals outputted from said matrix operation circuit.

6. A color corrector as set force in claim 5, wherein said color corrector for said CRT display device comprises:

three input terminals provided in correspondence with respective colors of said three primary colors, three primary video signals of said color image being applied to said three input terminals, respectively; and

three clamping circuits for allowing respective d.c. levels of three primary color video signals inputted from said three input terminals to match with each other to output them to said minimum level primary color signal selection circuit.