JPH10336688A - Image processing circuit and color television camera using the circuit - Google Patents

Abstract

(57) Abstract: Image processing that does not cause loss of a color difference signal regardless of whether a composite color image signal or an RGB color image signal is output, even when a high luminance portion of an image signal is compressed and white clipped. A circuit and a color television camera using the circuit are provided. A plurality of gamma correction circuits for performing gamma correction, a plurality of knee circuits for compressing high-luminance portions, respectively,
A plurality of white clipping circuits each for clipping a high-luminance portion, and a first subtraction circuit for calculating a difference between the gamma-corrected red, green, and blue image signals and the clipped red, green, and blue image signals A luminance signal matrix circuit that computes a luminance signal from each of the red, green, and blue differential signals; and a second subtraction circuit that computes the difference between each of the gamma-corrected red, green, and blue image signals and the luminance signal. , A luminance signal matrix circuit for calculating a luminance signal from each of the differential signals, red, green, and blue.
A color difference signal matrix circuit that calculates a color difference signal from each of the blue difference signals, and a red, green, and
And blue image signal output terminals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to R (red), G
The present invention relates to an image processing circuit for preventing loss of a color difference signal in signal processing of (green) and B (blue) image signals, in particular, to signal processing of a high luminance portion, and a color television camera using the circuit. is there.

[0002]

2. Description of the Related Art As is well known, for example, in a color television camera, an object is imaged by an imaging lens, and incident light is separated into three primary colors of R, G, and B by a color separation prism, and R, G, and B are separated. B The light is incident on each image sensor. R, G, B
Each image sensor photoelectrically converts the incident light of the three primary colors R, G, and B to generate R image signals, G image signals, and B image signals at signal levels corresponding to the respective incident light amounts. Output. Each amplifier amplifies the R, G, and B image signals to a predetermined level, respectively, and outputs predetermined levels of the R, G, and B image signals to an image signal processing circuit. The image signal processing circuit is a color television camera. And performs a required image signal processing to output a color image signal to other devices such as a video monitor and a VTR.

A block diagram of an image processing circuit of a conventional general color television camera or the like is shown in FIG. In a color television camera, as described above, R, G, and B image signals of a predetermined level obtained by performing photoelectric conversion by each of the R, G, and B image sensors and amplifying to a predetermined level by each of the amplifiers are respectively gamma-converted. The signals are input to the correction circuits 20, 21, and 22, where necessary gamma correction is performed in accordance with the gamma correction curve, and gamma-corrected R, G, and B image signals are output to the knee circuits 1, 2, and 3, respectively. . When the input gamma-corrected R, G, and B image signals include a high luminance portion, the knee circuits 1, 2, and 3 perform compression of the high luminance portion and perform the compressed R, G, and B images. The signals are output to the white clip circuits 4, 5, and 6, respectively. White clip circuit 4,
5 and 6, for example, are set so that 110% or more of the rated level of the image signal is clipped, and the image signal which becomes 110% or more of the rated level of the input compressed R, G, B image signal is set. The clipped R, G, and B image signals are output to the luminance signal matrix circuit 23 and the color difference signal matrix circuit 24, respectively. The clipped R, G, and B image signals are matrixed by one luminance signal matrix circuit 23 to be a luminance signal, and are matrixed by the other color difference signal matrix circuit 24 to be a color difference signal. Further, the luminance signal and the color difference signal are combined to form a color image signal, which is output to another device.

In the circuit configuration of the color television camera shown in FIG. 5, each output level of the compressed R, G, and B image signals output from the knee circuits 1, 2, and 3 has a white output for each signal output. When the clip level is set higher than the clip level of, for example, 110% of the rated level set in the clip circuits 4, 5, and 6, the R, G, and B image signals output from the white clip circuits 4, 5, and 6 have output signal levels. It is 110% of the rated level, which is equal. When the R, G, and B image signals having the same output signal level at 110% of the rated level are input to the color difference signal matrix circuit 24, the color difference signal output from the color difference signal matrix circuit 24 becomes 0, and the color difference signal which should exist originally. The signal is lost,
What has been a colored image becomes a white image.

In a white clip circuit, R, G, B
A block diagram of a conventional color television camera improved so as to prevent a color difference signal from being lost due to clipping of an image signal is shown and described in FIG. In a color television camera, as described above, R, G, and B image signals of a predetermined level obtained by performing photoelectric conversion by each of the R, G, and B image sensors and amplifying to a predetermined level by each of the amplifiers are respectively converted into gamma signals. The signals are input to the correction circuits 20, 21 and 22, and the required gamma correction is performed in accordance with the gamma correction curve to obtain gamma-corrected R, G and B image signals.
3 and the color difference signal matrix circuit 24. R,
Gamma correction circuit 2 for performing gamma correction on G and B image signals
0, 21, 22; knee circuits 1, 2, 3 for compressing high luminance portions; white clip circuits 4, 5, 6 for clipping image signals of a predetermined level or higher; a luminance signal matrix for outputting matrixed luminance signals The circuit 23 and each circuit for forming a luminance signal are the same as the circuits shown in FIG. 5, perform the same operation, and input and output the same image signal. However, the chrominance signal matrix circuit 24 receives the R, G, and B image signals which have been subjected to the gamma correction by the gamma correction circuits 20, 21, and 22. Since clipping is not performed in the circuit, the color difference signal output from the color difference signal matrix circuit 24 is not missing, is improved from the color television camera shown in FIG. 5, and an image of an original color is displayed. .

[0006]

The improved color television camera according to the prior art can prevent the color difference signal from being lost when outputting a composite color image signal, but can prevent the RGB color image signal from being lost. When the image signal is output after compression and white clipping of the high luminance portion of the image signal, the color difference signal is lost. The present invention provides an image processing circuit which does not cause a color difference signal loss even when a high-luminance portion of an image signal is compressed and white clipped, and either a composite color image signal or an RGB color image signal is output. And a color television camera using the circuit.

[0007]

In order to achieve the above object, an image processing circuit according to the present invention comprises a circuit for processing an image signal comprising a red image signal, a green image signal and a blue image signal. The circuit includes means for splitting each of the red, green, and blue image signals into a first image signal and a second image signal, and at least high brightness of the split second red, green, and blue image signals. A clipping circuit for clipping each of the portions, and the clipping circuit converts at least the clipped red, green, and blue image signals of the high-brightness portion from the split first red, green, and blue image signals. Means for generating a correction signal, and means for generating third red, green, and blue image signals from the red, green, and blue image signals of the branched first image signal and the correction signal, respectively. Things.

Further, the color television camera of the present invention has three colors of red, green, and blue obtained by color-separating the incident light from the imaging lens.
The primary colors are photoelectrically converted to red image signal, green image signal,
A color television camera having a red, green, and blue image sensor for outputting a blue image signal, comprising: a plurality of gamma correction circuits for performing required gamma correction on red, green, and blue image signals; A plurality of knee circuits for respectively compressing the high-luminance portions of the red, green, and blue image signals input from the correction circuit, and compressed red, green, and
A plurality of white clip circuits for clipping the high-luminance portion of each blue image signal, and gamma-corrected red, green, and blue image signals input from the plurality of gamma correction circuits and input from the plurality of white clip circuits A first subtraction circuit for calculating a difference between the clipped red, green, and blue image signals, and red, green, and
A luminance signal matrix circuit that calculates a luminance signal from each of the blue difference signals; and a gamma-corrected red, green, and blue image signal input from the plurality of gamma correction circuits and a luminance signal input from the luminance signal matrix circuit. A second subtraction circuit for calculating a difference between the second subtraction circuit, a luminance signal matrix circuit for calculating a luminance signal from each of the red, green, and blue difference signals input from the second subtraction circuit; and a second subtraction circuit. A color difference signal matrix circuit that calculates a color difference signal from each of the input red, green, and blue difference signals, and a red, green, and blue signal that outputs the red, green, and blue difference signals output from the second subtraction circuit. And an image signal output terminal.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing an embodiment of an image processing circuit and a color television camera using the circuit according to the present invention, basic solution means according to the present invention will be described. As a solution, even if the same R, G, B image signal is input to the luminance matrix circuit and the chrominance matrix circuit, the output signal has the same result as the input of different R, G, B image signals. The R, G, and B image signals to be input to the matrix circuit have the following formula (1). However, in the color television camera shown in FIG.
The R, G, and B image signals output from the gamma correction circuit are R1, G1, and B1, respectively, and the R, G, and B image signals output from the white clip circuit are R2, G2, and B, respectively.
2. The R, G, and B image signals output from the second subtraction circuit are R3, G3, and B3, respectively. This R3, G3,
If the R, G, and B image signals of B3 are output as they are, an image signal with no loss of color in a high luminance portion can be output. R3 = a1R1 + b1R2 + c1G1 + d1G2 + e1B1 + f1B2 G3 = a2R1 + b2R2 + c2G1 + d2G2 + e2B1 + f2B2 (1) B3 = a3R1 + b3R2 + c3G1 + d3G2 + e3B3 + 3G2 + e3B1 When the B3 image signal is input to the luminance matrix circuit and the chrominance matrix circuit, the coefficient a of the equation is set so that the output of the matrix circuit is represented by the following equation (2).
1 to a3, b1 to b3, c1 to c3, d1 to d3, e1
To e3 and f1 to f3. Y = 0.3R3 + 0.59G3 + 0.11B3 = 0.3R2 + 0.59G2 + 0.11B2 R3-Y = 0.7R3-0.59G3-0.11B3 = 0.7R1-0.59G1-0.11B1 ・ ・ ・ (2) B3-Y = -0.3R3-0.59G3 + 0.89B3 = -0.3R1-0.59G1 + 0.89B1

The following is obtained by substituting R3, G3, and B3 in the expression (1) into the expressions Y, R3-Y, and B3-Y in the expression (2). 0.3a1 + 0.59a2 + 0.11a3 = 0 0.7a1-0.59a2-0.11a3 = 0.7 ・ ・ ・ (3) -0.3a1-0.59a2 + 0.89a3 = -0.3 0.3b1 + 0.59b2 + 0.11b3 = 0.3 0.7b1 -0.59b2-0.11b3 = 0 ・ ・ ・ (4) -0.3b1-0.59b2 + 0.89b3 = 0 0.3c1 + 0.59c2 + 0.11c3 = 0 0.7c1-0.59c2-0.11c3 = -0.59 ・ ・ ・ ( 5) -0.3c1-0.59c2 + 0.89c3 = -0.59 0.3d1 + 0.59d2 + 0.11d3 = 0.59 0.7d1-0.59d2-0.11d3 = 0 ・ ・ ・ (6) -0.3d1-0.59d2 + 0.89d3 = 0 0.3e1 + 0.59e2 + 0.11e3 = 0 0.7e1-0.59e2-0.11e3 = -0.11 ・ ・ ・ (7) -0.3e1-0.59e2 + 0.89e3 = 0.89 0.3f1 + 0.59f2 + 0.11f3 = 0.11 0.7 f1−0.59f2−0.11f3 = 0 (8) −0.3f1−0.59f2 + 0.89f3 = 0 By solving these equations (3) to (8), the values of the respective coefficients are as follows. a1 = 0.7 a2 = -0.3 a3 = -0.3 b1 = 0.3 b2 = 0.3 b3 = 0.3 c1 = -0.59 c2 = 0.41 c3 = 0.89 d1 = 0.59 d2 = 0.59 d3 = 0.59 e1 = -0.11 e2 = -0.11 e3 = 0.89 f1 = 0.11 f2 = 0.11 f3 = 0.11

By substituting the coefficients into equation (1) and rearranging, R3, G3, and B3 are given by the following equation (9). R3 = 0.7R1 + 0.3R2-0.59G1 + 0.59G2-0.11B1-0.11B2 R3 = 0.7R1 + (0.3R1-0.3R1) + 0.3R2-0.59 (G1-G2) -0.11 (B1-B2) R3 = R1 -{0.3 (R1-R2) +0.59 (G1-G2) +0.11 (B1-B2)} G3 = -0.3R1 + 0.3R2 + 0.41G1 + 0.59G2-0.11B1 + 0.11B2 G3 = -0.3 (R1- R2) + 0.41G1 + (0.59G1-0.59G1) + 0.59G2-0.11 (B1-B2) ・ ・ ・ (9) G3 = G1- {0.3 (R1-R2) +0.59 (G1-G2) +0.11 (B1 -B2)} B3 = -0.3R1 + 0.3R2-0.59G1 + 0.59G2 + 0.89B1 + 0.11B2 B3 = -0.3 (R1-R2) -0.59 (G1-G2) + 0.89B1 + (0.11B1-0.11B1) + 0.11B2 B3 = B1- {0.3 (R1-R2) +0.59 (G1-G2) +0.11 (B1-B2)}

As will be described in the following embodiments, when the image signals R3, G3, B3 derived as described above are input to the luminance signal matrix circuit, the output is the image signal R3.
When the image signals R3, G3, and B3 are input to the color difference signal matrix circuit, the superimposed correction signal components are canceled and lost, and the output is the same as the image signal R3, G2, and B2. Signals R1, G1, B
It will be the same as inputting 1. The color television camera of the present invention specifically realizes the above-described basic solution.

[First Embodiment] A first embodiment of an image processing circuit according to the present invention and a color television camera using the circuit will be described with reference to FIG. I do. In FIG.
Reference numerals 1 and 22 denote gamma correction circuits for performing gamma correction on R, G, and B image signals, and 1, 2, and 3 denote gamma-corrected R, G, and G signals.
B knee circuit for compressing a high-luminance portion of each image signal;
Reference numerals 4, 5, and 6 denote white clip circuits for clipping a high-luminance portion of each of the R, G, and B image signals subjected to the compression processing;
7, 8, and 9 are first subtraction circuits for performing subtraction processing of R, G, and B image signals; 11, 12, and 13 are second subtraction circuits that perform subtraction processing for R, G, and B image signals; Reference numeral 10 denotes a luminance matrix circuit that performs matrix processing on the R, G, and B image signals from the first subtraction circuits 7, 8, and 9 and outputs a luminance signal;
3, R, G, and R from the second subtraction circuits 11, 12, and 13
B: a luminance matrix circuit that performs matrix processing on each image signal and outputs a luminance signal;
3 shows a color difference matrix circuit that performs matrix processing on R, G, and B image signals from 2 and 13 and outputs a color difference signal.

Next, the operation will be described. In the color television camera, as described above, the R image signal, the G image signal, and the B image signal of a predetermined level obtained by performing photoelectric conversion by each of the R, G, and B image sensors and amplifying to a predetermined level by each amplifier. Are input to gamma correction circuits 20, 21, and 22, respectively, and are subjected to required gamma correction in accordance with a gamma correction curve, and are gamma-corrected R image signal (R1) and G image signal (G1). , B image signals (referred to as B1) and output to the knee circuits 1, 2, 3 and the first subtraction circuits 7, 8, 9 and the second subtraction circuits 11, 12, 13, respectively. When the input gamma-corrected R, G, and B image signals have a high luminance portion, the knee circuits 1, 2, and 3 perform compression of the high luminance portion and perform the compression of the compressed R, G, and B image signals.
G and B image signals are respectively converted to white clip circuits 4,
Output to 5 and 6.

The white clipping circuits 4, 5, and 6 are set so as to clip, for example, 110% or more of the rated level of the image signal.
An image signal that is 110% or more of the rated level of the B image signal is clipped, and the clipped R image signal (referred to as R2), G image signal (referred to as G2), and B image signal (referred to as B2) are each a first signal. To the subtraction circuits 7, 8, and 9. The first subtraction circuits 7, 8, and 9 respectively output the clipped image signal R2 and the image signal G from the input gamma-corrected image signal R1, image signal G1, and image signal B1.
2. R1-R2, G1-G2 for subtracting the image signal B2,
B1-B2 are calculated, and the calculation result is output to the luminance matrix circuit 10. The luminance matrix circuit 10 performs matrix processing on the input R1-R2, G1-G2, and B1-B2 calculation results, and outputs the luminance signal to the second subtraction circuit 1
Output to 1, 12, and 13. Second subtraction circuit 11, 1
Reference numerals 2 and 13 denote input gamma-corrected image signals R
1. A luminance signal subjected to matrix processing separately input is subtracted from the image signal G1 and the image signal B1, and the image signal R3, the image signal G3, and the image signal B3 are subtracted from the luminance matrix circuit 23, the color difference matrix circuit 24, and R, G, and B. Output to the color image signal output terminal.

In the luminance matrix circuit 23 and the color difference matrix circuit 24, the following matrix expressions (10) and (1)
According to 1) and (12), the luminance signal Y and the color difference signal R3-Y,
B3-Y are output. Y = 0.3R3 + 0.59G3 + 0.11B3 = 0.3R2 + 0.59G2 + 0.11B2 ・ ・ ・ (10) R3-Y = 0.7R3-0.59G3-0.11B3 = 0.7R1-0.59G1-0.11B1 ・ ・ ・ ( 11) B3-Y = -0.3R3-0.59G3 + 0.89B3 = -0.3R1-0.59G1 + 0.89B1 (12) The luminance signal Y is represented by the image signals R2, G2, and B from the equation (10).
2, the color difference signals R3-Y and B3-Y are (11), (1)
From equation (2), it can be understood that R1, G1, and B1 are generated. As a result, the luminance signal Y is generated by the components of the image signals R2, G2, and B2 that have undergone knee processing and clip processing, is the same as the luminance signal generated by the conventional circuit, and has the color difference signals R3-Y, B3- Y is generated by components of the image signals R1, G1, and B1 that have not been subjected to knee processing and clipping processing, and can obtain an image of an original color without any omission as in a color difference signal generated by a conventional circuit. it can.

[Embodiment 2] A second embodiment of an image processing circuit according to the present invention and a color television camera (only the parts necessary for the description) using the circuit will be described with reference to FIG. I do. In this color television camera, since the color difference signal is generated from the image signal immediately after the knee processing, the color difference signal which has been missing in the conventional white clip processing can be generated. In FIG.
Reference numerals 20, 21, and 22 denote gamma correction circuits that perform gamma correction on R, G, and B image signals, and 1, 2, and 3 perform compression processing on high-luminance portions of gamma-corrected R, G, and B image signals. Knee circuits, 4, 5, and 6 denote white clip circuits for clipping a high-luminance portion of the compressed R, G, and B image signals, and 7, 8, and 9 deduct R, G, and B image signals. The first subtraction circuits for processing, 11, 12, and 13 are R, G, B
A second subtraction circuit 10 that performs a subtraction process on each image signal includes:
A luminance matrix circuit that performs matrix processing on each of the R, G, and B image signals from the first subtraction circuits 7, 8, and 9 and outputs a luminance signal is provided with R, G, and B signals from the second subtraction circuits 11, 12, and 13. A luminance matrix circuit that performs a matrix process on each of the G and B image signals and outputs a luminance signal;
1 shows a color difference matrix circuit that performs matrix processing on R, G, and B image signals from 1, 12, and 13 and outputs color difference signals.

Next, the operation will be described. In the color television camera, as described above, the R image signal, the G image signal, and the B image signal of a predetermined level obtained by performing photoelectric conversion by each of the R, G, and B image sensors and amplifying to a predetermined level by each amplifier. Are input to the gamma correction circuits 20, 21, and 22, respectively, are subjected to required gamma correction according to the gamma correction curve, and are gamma-corrected R image signal, G image signal,
B image signals are output to knee circuits 1, 2, and 3, respectively. When the input gamma-corrected R, G, and B image signals have a high luminance portion, the knee circuits 1, 2, and 3
A high-luminance portion is compressed, and the compressed R image signal (R1), G image signal (G1), and B image signal (B1) are respectively subjected to a white clipping circuit 4,
5, 6 and first subtraction circuits 7, 8, 9 and second subtraction circuit 1
1, 12, and 13.

The white clipping circuits 4, 5, and 6 are set so as to clip, for example, 110% or more of the rated level of the image signal, and receive the input compressed image signal R1, image signal G1, and image signal B1. Rated level of 11
The image signals of 0% or more are respectively clipped, and the clipped R image signal (referred to as R2), G image signal (referred to as G2), and B image signal (referred to as B2) are first subtraction circuits 7 and 8, respectively. , 9 are output. The first subtraction circuits 7, 8,
Reference numeral 9 denotes R1 for subtracting the separately input clipped image signal R2, image signal G2, and image signal B2 from the input compressed image signal R1, image signal G1, and image signal B1.
-R2, G1-G2, and B1-B2 are calculated, and the calculation results are output to the luminance matrix circuit 10. The luminance matrix circuit 10 receives the input R1-R2, G1-G2,
Matrix processing is performed on the calculation result of B1-B2, and the luminance signal is output to the second subtraction circuits 11, 12, and 13. The second subtraction circuits 11, 12, and 13 subtract the separately input matrix-processed luminance signal from the input compressed image signal R1, image signal G1, and image signal B1, respectively, and output the image signal R3 and the image signal G3. , And outputs the image signal B3 to the luminance matrix circuit 23, the color difference matrix circuit 24, and the R, G, and B color image signal output terminals.

The luminance matrix circuit 23 and the chrominance matrix circuit 24 use the above-described matrix equations (10) and (1).
1) and (12) (described in the first embodiment), a luminance signal Y and color difference signals R3-Y and B3-Y are output. From the equation (10), the luminance signal Y is represented by the image signals R2, G2, B2
The color difference signals R3-Y and B3-Y are (11), (1)
From equation (2), it can be understood that R1, G1, and B1 are generated. As a result, the luminance signal Y is generated by the components of the image signals R2, G2, and B2 that have undergone knee processing and clip processing, is the same as the luminance signal generated by the conventional circuit, and has the color difference signals R3-Y, B3- Y is generated by the components of the image signals R1, G1, and B1 that have not been clipped, so that there is no loss as in a color difference signal generated by a conventional circuit, and an image of almost the original color can be obtained.

[Third Embodiment] A third embodiment of an image processing circuit according to the present invention and a color television camera using the circuit will be described with reference to FIG. I do. In this color television camera, since the color difference signal is generated by performing knee processing independent of the luminance signal, it is possible to reproduce the color of the high luminance signal that was previously missing, and to improve the color reproducibility. Can be. In FIG. 3, reference numerals 20, 21, and 22 denote gamma correction circuits for performing gamma correction on R, G, and B image signals.
Reference numeral 3 denotes a first knee circuit for compressing a high-luminance portion of each of the gamma-corrected R, G, and B image signals at a first compression ratio;
Reference numerals 4, 15, and 16 denote second knee circuits for compressing the high-luminance portions of the gamma-corrected R, G, and B image signals at a second compression ratio. A white clip circuit for clipping a high-luminance portion of each of the compressed R, G, and B image signals from the circuits 1, 2, and 3;
Reference numeral 9 denotes a first subtraction circuit that performs a subtraction process on each of the R, G, and B image signals. Reference numerals 11, 12, and 13 denote a second subtraction circuit that performs a subtraction process on each of the R, G, and B image signals. A luminance matrix circuit 23 that performs matrix processing on each of the R, G, and B image signals from the subtraction circuits 7, 8, and 9 and outputs a luminance signal;
A luminance matrix circuit 24 that performs a matrix process on each of the R, G, and B image signals from the second subtraction circuits 11, 12, and 13 and outputs a luminance signal is a second subtraction circuit 11, 12, and 13.
1 shows a color difference matrix circuit that performs matrix processing on each of R, G, and B image signals and outputs a color difference signal.

Next, the operation will be described. In the color television camera, as described above, the R image signal, the G image signal, and the B image signal of a predetermined level obtained by performing photoelectric conversion by each of the R, G, and B image sensors and amplifying to a predetermined level by each amplifier. Are input to the gamma correction circuits 20, 21, and 22, respectively, are subjected to required gamma correction according to the gamma correction curve, and are gamma-corrected R image signal, G image signal,
B image signals, and the first knee circuits 1, 2, 3
And the second knee circuits 14, 15, and 16. When the input gamma-corrected R, G, B image signal has a high luminance portion, the second knee circuits 14, 15, 16 compress the high luminance portion at the second compression ratio, and perform compression. R image signal (R1) and G image signal (G1
), And the B image signal (referred to as B1) with the first subtraction circuits 7, 8, 9 and the second subtraction circuits 11, 12, 13 respectively.
And output to When the input gamma-corrected R, G, and B image signals have a high luminance portion, the first knee circuits 1, 2, and 3 compress the high luminance portion at a first compression ratio and perform compression. Are output to the white clip circuits 4, 5, and 6, respectively.

The white clip circuits 4, 5, and 6 are set so as to clip, for example, 110% or more of the rated level of the image signal.
An image signal that is 110% or more of the rated level of the B image signal is clipped, and the clipped R image signal (referred to as R2), G image signal (referred to as G2), and B image signal (referred to as B2) are each a first signal. To the subtraction circuits 7, 8, and 9. The first subtraction circuits 7, 8, and 9 respectively provide the input compressed image signal R1, image signal G1, and image signal R2, image signal G2,
R1-R2, G1-G2, B1 for subtracting the image signal B2
−B2, and outputs the operation result to the luminance matrix circuit 10. The luminance matrix circuit 10 performs matrix processing on the input R1-R2, G1-G2, and B1-B2 calculation results, and converts the luminance signals into second subtraction circuits 11, 1
Output to 2 and 13. Second subtraction circuits 11, 12, 13
Are the input compressed image signal R1 and image signal G
1. A luminance signal which has been separately subjected to matrix processing is subtracted from the image signal B1, and the image signal R3, the image signal G3, and the image signal B3 are output to the luminance matrix circuit 23, the color difference matrix circuit 24, and the R, G, B color image signal output. Output to terminal.

In the luminance matrix circuit 23 and the color difference matrix circuit 24, the above-described matrix equations (10) and (1)
1) and (12) (described in the first embodiment), a luminance signal Y and color difference signals R3-Y and B3-Y are output. From the equation (10), the luminance signal Y is represented by the image signals R2, G2, B2
The color difference signals R3-Y and B3-Y are (11), (1)
From equation (2), it can be understood that R1, G1, and B1 are generated. As a result, the luminance signal Y is generated by the components of the image signals R2, G2, and B2 that have undergone knee processing and clip processing, is the same as the luminance signal generated by the conventional circuit, and has the color difference signals R3-Y, B3- Y is generated by the components of the image signals R1, G1, and B1 that have not been clipped, and can obtain an image of the original color without any omission as in a color difference signal generated by a conventional circuit.

[Embodiment 4] A fourth embodiment of an image processing circuit according to the present invention and a color television camera (only the parts necessary for the description) using the circuit will be described with reference to FIG. I do. In this color television camera, the color difference signal is generated by performing knee processing and white clip processing with the required settings independently of the luminance signal. And color reproducibility can be improved. In FIG. 4, reference numerals 20, 21, and 22 denote gamma correction circuits that perform gamma correction on R, G, and B image signals, and 1, 2, and 3 denote high-luminance portions of gamma-corrected R, G, and B image signals. A first knee circuit for performing a compression process at a first compression ratio, 14, 15, 16
Is a second knee circuit for compressing the high-luminance portion of each of the gamma-corrected R, G, and B image signals at a second compression ratio.
Reference numerals 5 and 6 denote a first white clip circuit for clipping the high-luminance portions of the R, G, and B image signals from the first knee circuits 1, 2, and 3 at a first clip level. , 17, 18, and 19 are connected to the second knee circuits 14, 1
A second white clip circuit for clipping the high-luminance portion of each of the R, G, B image signals subjected to the compression processing from 5, 16 at the second clip level, 7, 8, 9 are R, G,
B: a first subtraction circuit for performing a subtraction process of each image signal, 11,
Reference numerals 12 and 13 denote second subtraction circuits for subtracting the R, G, and B image signals, and reference numeral 10 denotes a matrix processing of the R, G, and B image signals from the first subtraction circuits 7, 8, and 9. A luminance matrix circuit 23 for outputting a luminance signal; a luminance matrix circuit 23 for processing the R, G, and B image signals from the second subtraction circuits 11, 12, and 13 and outputting a luminance signal;
4, R, G, and R from the second subtraction circuits 11, 12, and 13
B illustrates a color difference matrix circuit that performs matrix processing on each image signal and outputs a color difference signal.

Next, the operation will be described. In the color television camera, as described above, the R image signal, the G image signal, and the B image signal of a predetermined level obtained by performing photoelectric conversion by each of the R, G, and B image sensors and amplifying to a predetermined level by each amplifier. Are input to the gamma correction circuits 20, 21, and 22, respectively, are subjected to required gamma correction according to the gamma correction curve, and are gamma-corrected R image signal, G image signal,
B image signals, and the first knee circuits 1, 2, 3
And the second knee circuits 14, 15, and 16. When the input gamma-corrected R, G, B image signal has a high luminance portion, the second knee circuits 14, 15, 16 compress the high luminance portion at the second compression ratio, and perform compression. Are output to the second white clip circuits 17, 18, and 19, respectively. The white clip circuits 17, 18, and 19 are set so as to clip a second clip level, for example, 110% or more of the rated level of the image signal, and output the input compressed R, G, and B image signals. An image signal that is 110% or more of the rated level is clipped, and the clipped R image signal (R1
), G image signal (G1), B image signal (B
1) with the first subtraction circuits 7, 8, 9 and the second
To the subtraction circuits 11, 12, and 13.

When the input gamma-corrected R, G, B image signal has a high luminance portion, the first knee circuits 1, 2, 3 compress the high luminance portion at the first compression ratio. Do,
The compressed R, G, and B image signals are output to the first white clip circuits 4, 5, and 6, respectively. The first white clip circuits 4, 5, and 6 are set so as to clip a first clip level, for example, 130% or more of the rated level of the image signal. An image signal that is 130% or more of the rated level of the image signal is clipped, and the clipped R image signal (R2
), G image signal (G2), B image signal (B
2) to the first subtraction circuits 7, 8, and 9, respectively. The first subtraction circuits 7, 8, and 9 output the clipped image signal R1, the image signal G1, and the clipped image signal R2 and the image signal G separately input from the image signal B1.
2. R1-R2, G1-G2 for subtracting the image signal B2,
B1-B2 are calculated, and the calculation result is output to the luminance matrix circuit 10. The luminance matrix circuit 10 performs matrix processing on the input R1-R2, G1-G2, and B1-B2 calculation results, and outputs the luminance signal to the second subtraction circuit 1
Output to 1, 12, and 13. Second subtraction circuit 11, 1
Reference numerals 2 and 13 denote subtraction of a separately input matrix-processed luminance signal from the input clipped image signal R1, image signal G1, and image signal B1, and convert the image signal R3, image signal G3, and image signal B3 into a luminance matrix circuit. 23, a color difference matrix circuit 24, and R, G, B color image signal output terminals.

The luminance matrix circuit 23 and the chrominance matrix circuit 24 use the above-described matrix equations (10) and (1).
1) and (12) (described in the first embodiment), a luminance signal Y and color difference signals R3-Y and B3-Y are output. From the equation (10), the luminance signal Y is represented by the image signals R2, G2, B2
The color difference signals R3-Y and B3-Y are (11), (1)
From equation (2), it can be understood that R1, G1, and B1 are generated. As a result, the luminance signal Y is generated by the components of the image signals R2, G2, and B2 that have undergone knee processing and clip processing, is the same as the luminance signal generated by the conventional circuit, and has the color difference signals R3-Y, B3- Y is generated by the components of the image signals R1, G1, and B1 that have undergone knee processing and white clip processing by independent required settings, and have almost no loss of color and substantially the original color unlike a color difference signal generated by a conventional circuit. Image can be obtained. The above description is based on N
Although the matrix operation of the luminance signal of the TSC system has been described as an example, the present invention can also be used for the matrix operation of another luminance signal, for example, the matrix operation of the luminance signal of the Hi-Vision system.

[0029]

According to the present invention, the compression and white clipping of the high-luminance portion of the image signal, the color image signal of the composite system or the color image signal of the RGB system can be output regardless of the color difference signal. An image processing circuit which does not cause dropout and a color television camera using the circuit can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram of a color television camera (first embodiment) using an image processing circuit of the present invention.

FIG. 2 is a block diagram of a color television camera (Embodiment 2) using the image processing circuit of the present invention.

FIG. 3 is a block diagram of a color television camera (Embodiment 3) using the image processing circuit of the present invention.

FIG. 4 is a block diagram of a color television camera (Embodiment 4) using the image processing circuit of the present invention.

FIG. 5 is a block diagram of an image processing circuit of a conventional color television camera or the like.

FIG. 6 is a block diagram of an image processing circuit of a conventional improved color television camera or the like.

[Explanation of symbols]

 1, 2, 3, 14, 15, 16 knee circuit 4, 5, 6, 17, 18, 19 white clip circuit 7, 8, 9, 11, 12, 13 subtraction circuit 10, 23 luminance signal matrix circuit 20, 21 , 22 Gamma correction circuit 24 Color difference signal matrix circuit.

Claims (6)

[Claims] 1. A circuit for processing an image signal comprising a red image signal, a green image signal, and a blue image signal, wherein the image processing circuit converts the red, green, and blue image signals into a first image signal and a second image signal. A clipping circuit for clipping a high-brightness portion of each of the branched second red, green, and blue image signals; and a clipping circuit for at least the high-brightness portion. The clipped red, green, and blue image signals and the split first
Means for generating a correction signal from each of the red, green, and blue image signals; and a third red, green, and green signal from the red, green, and blue image signals of the branched first image signal and the correction signal. Means for generating each blue image signal. 2. The image processing circuit according to claim 1, further comprising: means for generating a luminance signal by a matrix operation from the third red, green, and blue image signals, and generating the correction signal. Means for subtracting the clipped red, green, and blue image signals of the at least high brightness portion from the first red, green, and blue image signals, respectively, and subtracting the subtracted red, green, and blue image signals; Means for generating the luminance signal, and the subtraction means by means of a ratio of each of the red, green, and blue image signals of the matrix operation in the means of generating the luminance signal and a ratio of each of the red, green, and blue image signals of the same matrix operation. Means for generating the correction signal from each of the red, green, and blue image signals subtracted by the following. 3. A red image signal obtained by photoelectrically converting three primary colors of red, green, and blue obtained by color-separating incident light from an imaging lens.
A color television camera having red, green, and blue image sensors that output green image signals and blue image signals, and a plurality of gamma correction circuits that perform required gamma correction on the red, green, and blue image signals, A plurality of knee circuits for respectively compressing high-luminance portions of the red, green, and blue image signals input from the plurality of gamma correction circuits; and a compressed red, green, and blue image signal input from the plurality of knee circuits, respectively. A plurality of white clip circuits respectively clipping the high-luminance portion, and gamma-corrected red, green, and blue image signals input from the plurality of gamma correction circuits and clipped input from the plurality of white clip circuits. A first subtraction circuit for calculating a difference between each of the red, green, and blue image signals; and a luminance signal mat for calculating a luminance signal from each of the red, green, and blue difference signals input from the first subtraction circuit. And a second subtraction circuit that calculates a difference between the gamma-corrected red, green, and blue image signals input from the plurality of gamma correction circuits and the luminance signal input from the luminance signal matrix circuit. A luminance signal matrix circuit for calculating a luminance signal from each of the red, green, and blue differential signals input from the second subtraction circuit; and a chrominance difference from the red, green, and blue differential signals input from the second subtraction circuit. A color difference signal matrix circuit that calculates a signal; and a red, green, and blue image signal output terminal that outputs a red, green, and blue difference signal output from the second subtraction circuit. Color television camera. 4. A red image signal obtained by photoelectrically converting three primary colors of red, green, and blue obtained by color-separating incident light from an imaging lens,
A color television camera having red, green, and blue image sensors that output green image signals and blue image signals, and a plurality of gamma correction circuits that perform required gamma correction on the red, green, and blue image signals, A plurality of knee circuits for respectively compressing high-luminance portions of the red, green, and blue image signals input from the plurality of gamma correction circuits; and a compressed red, green, and blue image signal input from the plurality of knee circuits, respectively. A plurality of white clip circuits respectively clipping the high-luminance portion of the compressed red, green, and blue image signals input from the plurality of knee circuits and the clipped red and green input from the plurality of white clip circuits A first subtraction circuit for calculating a difference from each of the blue image signals; a luminance signal matrix circuit for calculating a luminance signal from each of the red, green, and blue differential signals input from the first subtraction circuit; A second subtraction circuit for calculating a difference between the compressed red, green, and blue image signals input from the plurality of knee circuits and the luminance signal input from the luminance signal matrix circuit; A luminance signal matrix circuit for calculating a luminance signal from each of the input red, green, and blue difference signals; and a color difference signal matrix for calculating a color difference signal from each of the red, green, and blue difference signals input from the second subtraction circuit. A color television camera comprising: a circuit; and a red, green, and blue image signal output terminal that outputs a red, green, and blue difference signal output from the second subtraction circuit. 5. A red image signal obtained by photoelectrically converting three primary colors of red, green, and blue obtained by color-separating incident light from an imaging lens.
A color television camera having red, green, and blue image sensors that output green image signals and blue image signals, and a plurality of gamma correction circuits that perform required gamma correction on the red, green, and blue image signals, The high luminance portions of the red, green, and blue image signals input from the plurality of gamma correction circuits
And a plurality of second knee circuits for compressing the high-luminance portions of the red, green, and blue image signals input from the plurality of gamma correction circuits at a second compression ratio. And a compressed red input from the plurality of first knee circuits.
A plurality of white clipping circuits for respectively clipping a high-luminance portion of each of the green and blue image signals; and a compressed red input from the plurality of second knee circuits.
A first subtraction circuit for calculating a difference between each of the green and blue image signals and the clipped red, green and blue image signals input from the plurality of white clip circuits; and a first subtraction circuit input from the first subtraction circuit. A luminance signal matrix circuit for calculating a luminance signal from each of the red, green, and blue differential signals; and a compressed red signal input from the plurality of second knee circuits.
A second subtraction circuit that calculates a difference between each of the green and blue image signals and the luminance signal input from the luminance signal matrix circuit; and a luminance subtraction circuit that calculates the luminance from each of the red, green, and blue differential signals input from the second subtraction circuit. A luminance signal matrix circuit for calculating a signal; a color difference signal matrix circuit for calculating a color difference signal from each of the red, green and blue difference signals input from the second subtraction circuit; and a signal output from the second subtraction circuit. A color television camera comprising: a red, green, and blue image signal output terminal that outputs a red, green, and blue differential signal. 6. A red image signal obtained by photoelectrically converting three primary colors of red, green, and blue obtained by color-separating incident light from an imaging lens,
A color television camera having red, green, and blue image sensors that output green image signals and blue image signals, and a plurality of gamma correction circuits that perform required gamma correction on the red, green, and blue image signals, The high luminance portions of the red, green, and blue image signals input from the plurality of gamma correction circuits
And a plurality of second knee circuits for compressing the high-luminance portions of the red, green, and blue image signals input from the plurality of gamma correction circuits at a second compression ratio. A plurality of first white clip circuits each of which clips a high luminance portion of each of the red, green, and blue image signals input from the plurality of first knee circuits at a first clip level; A plurality of second white clip circuits for clipping the high luminance portions of the red, green, and blue image signals input from the second knee circuit at a second clip level, respectively; and the plurality of second white clip circuits Red entered from
A first subtraction circuit for calculating a difference between each of the green and blue image signals and each of the red, green and blue image signals input from the plurality of first white clipping circuits; and a first subtraction circuit input from the first subtraction circuit. A luminance signal matrix circuit for calculating a luminance signal from each of the red, green, and blue differential signals; and a red, green, and blue image signal input from the plurality of second white clip circuits and input from the luminance signal matrix circuit. A second subtraction circuit for calculating a difference from the luminance signal; a luminance signal matrix circuit for calculating a luminance signal from each of the red, green, and blue differential signals input from the second subtraction circuit; A color difference signal matrix circuit that calculates a color difference signal from each of the red, green, and blue difference signals input from the circuit; and red, green, and blue that output each of the red, green, and blue difference signals output from the second subtraction circuit. Blue image signal output terminal Color television camera, characterized in that it comprises a.