JP3304414B2 - Video signal correction device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal correction apparatus suitable for use in a color image apparatus which handles R, G, and B signals and capable of easily correcting white balance.

[0002]

2. Description of the Related Art In order to obtain a high degree of satisfaction in expressing a color image by a video signal, R, which constitutes the video signal,
It is indispensable to always keep the amplitude level and the DC level of the G and B signals or the Y, RY and BY signals in an appropriate state and maintain a good white balance.

[0003] Therefore, it is extremely important to accurately correct the white balance deviation of a color image or to accurately adjust a color image to a desired white balance in adjusting a color image apparatus. I have. FIG. 6 shows an example of a conventional business white balance correction device for this purpose.

In the figure, R, G,
In each signal path of the B signal, a gain adjustment circuit for adjusting the amplitude level and an offset adjustment circuit for adjusting the DC level are provided, and offset adjustment volumes 71 to 71 of these adjustment circuits are provided. By operating the 73 and the gain adjustment knobs 74 to 76, the offset amount and the amplitude level of each of the R, G, and B signals are adjusted to correct the white balance.

FIG. 7 shows a simplified white balance correction device for consumer use. The apparatus shown in the figure is configured so that, by operating the joystick, the RY-axis and BY-axis color difference axis components adjusted to an arbitrary level can be set as correction data. The correction data is further modulated by the Y signal to form a correction amount, and the formed correction amounts are added to the RY signal and the BY signal, respectively, to perform white balance correction. In particular, in this device, as shown in FIG. 8, the joystick is provided with an operation lever 81 at a position corresponding to the origin on the chromaticity plane. The amount and hue to be corrected can be determined based on the color of the formed coloring 82.

[0006]

However, the conventional white balance correction device shown in FIG. 6 directly controls each volume for offset adjustment and gain adjustment corresponding to each signal by hand. In particular, when the balance of the white portion of the image is corrected by operating the three gain adjustment volumes 74 to 76, it is intuitive to judge an appropriate correction level and hue from the three operation parameters. It is difficult to accurately correct white balance using this device, so a special measuring instrument such as a vectorscope must be used, so ordinary users can make accurate white balance correction with this device. That was almost impossible.

Further, since the conventional white balance correction device shown in FIG. 7 uses a joystick to set the correction data as described above, the correction is performed by referring to the color of the coloring. It is easy to intuitively grasp the power amount and the hue, and even a general user can easily make corrections.
In order to form a correction amount for the Y signal and the RY signal, a complicated operation called modulation by the Y signal was required. In spite of such complicated calculations, the principle of white balance correction by this device is simply simple, and therefore, the Y signal, R signal
There was a drawback that the shift components contained in each of the -Y signal and the BY signal could not be completely removed. (For this point, "2) Correction of white balance" in the section of [Example] At the end of the section).

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art. In a video signal correction apparatus for correcting the white balance of an input video signal, an offset adjustment of the input video signal is performed. A two-dimensional adjustment amount setting unit for setting the amount and the gain adjustment amount, and at least an offset adjustment amount set by the two-dimensional adjustment amount setting unit for performing a black balance adjustment of the video signal and a white balance adjustment of the video signal. A data converter for performing data conversion of the gain adjustment amount set by the two-dimensional adjustment amount setting means to perform the conversion output from the data converter and R,
This is a video signal correction device having a correction circuit that receives G and B signals and corrects the R, G, and B signals based on the converted output.

[0009]

According to the present invention, the offset adjustment amount and the gain adjustment amount of the input video signal are set by the two-dimensional adjustment amount setting means, and at least the black balance adjustment of the video signal is performed by the data converter. Data conversion is performed between the offset adjustment amount set by the dimension adjustment amount setting unit and the gain adjustment amount set by the two-dimensional adjustment amount setting unit for performing white balance adjustment of the video signal, and the data from the data converter to the correction circuit. The converted output and the R, G, B signals are input, and the R, G, B signals are corrected by the converted output.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in two parts, namely, the principle of white balance correction in the present invention, and a specific circuit configuration and a correction procedure.

Principle of White Balance Correction in the Present Invention First, the correction of the white balance of a black portion (hereinafter, referred to as black balance) will be described, and then, the correction of the white balance of a high luminance portion (hereinafter, referred to as white balance). Will be described.

1. Correction of Black Balance In general, the relationship among the luminance signal, the color difference signal, the R, G, and B signals is expressed by the following [Equation 1].

[0013]

(Equation 1)

Here, the values of the respective signals in a state where the black balance is maintained are respectively represented by R, G, B, Y, RY, and BY.
In addition, the values of the respective signals when the black balance is shifted due to the DC offsets a, b, and c occurring in the R, G, and B signals are respectively represented by R ′, G ′, and B ′. ,
Y ', (RY)', (BY) '

[0015]

(Equation 2)

Can be expressed as Now, Y, RY, BY
The deviation amount of the black balance of each signal is represented by ΔY, Δ (R
−Y) and Δ (B−Y), from the equation (2), ΔY = Y′−Y = 0.3a + 0.59b + 0.11c (1) Δ (RY) = (RY) ) '-(RY) = 0.7a-0.59b-0.11c (2) Δ (BY) = (BY)'-(BY) =-0.3a-0 .59b + 0.89c (3)

Therefore, the offset amounts a, b, and c of the R, G, and B signals are equal to the deviation amounts ΔY, Δ (RY), Δ (B−
Looking at how it is represented by Y), (1)
From equation (3), a = ΔY + Δ (RY) (4) b = ΔY− [0.3Δ (RY) + 0.11Δ (BY)] / 0.59 (5) c = ΔY + Δ (BY) (6)

[0018] Here, as the adjustment amount for the black balance correction, adjusted by setting the luminance adjustment amount Y _B, and the R-Y axis component R _B and B-Y axis component B _B on chromaticity plane Think of a way. Now, ΔY, Δ on the right side of equations (4) to (6)
(R−Y) and Δ (B−Y) are represented by Y _B , R _B , and B _B , respectively.
The following equations (7) to (9), which are obtained by replacing the equations (7) to (9), are executed, and these operation outputs α, β,
If a circuit for subtracting from the B signal is provided, Y _B , R _B , B _B
At the time when the values of a, b, and c are obtained as calculation outputs α, β, and γ, a signal whose black balance has been accurately corrected is output to the output side of the subtraction circuit. Will be obtained.

[0019] _{α = Y B + R B ...} (7) β = Y B - [0.3R _B + 0.11B _B] /0.59 ... (8) γ = Y B + B B ... (9) to the above principle Based on this, the black balance is corrected according to the present invention.

2. Correction of White Balance In general, a shift in white balance is caused by a change in the color temperature, resulting in a change in the levels of the R, G, and B signals. Therefore, the values of the respective signals in a state where the white balance is maintained at the reference color temperature are respectively represented by R, G, B, Y, RY, and B.
−Y, and the values of the respective signals when the respective levels of the R, G, and B signals are a times, b times, and c times as the color temperature changes, respectively, are R ′, G ′, B ', Y', (RY) ',
(BY) '

[0021]

(Equation 3)

## EQU1 ## Therefore, the above-described variable a,
The deviation amounts of the white balance of the Y, RY, and BY signals caused by b and c are represented by ΔY, Δ (RY), Δ (B−
Y), these can be obtained from the equations of [Equation 1] and [Equation 3], ΔY = Y′−Y = 0.3 (a−1) R + 0.59 (b−1) G + 0.11 ( c-1) B (10) Δ (RY) = (RY) '-(RY) = 0.7 (a-1) R-0.59 (b-1) G-0 .11 (c-1) B (11) Δ (BY) = (BY) ′ − (BY) = − 0.3 (a−1) R−0.59 (b−1) ) G + 0.89 (c-1) B (12)

From the expressions (10) to (12), the variable a,
b and c are defined as deviation amounts ΔY, Δ (RY), Δ (BY),
And as a function of R, G, B, a = 1 + [Δ (RY) + ΔY] / R (13) b = 1 + [0.59ΔY−0.3Δ (RY) −0.11Δ (BY)] / 0. 59G (14) c = 1 + [ΔY + Δ (BY)] / B (15)

If the gains of the R, G, and B signals are set to 1 / a, 1 / b, and 1 / c, the level of each signal returns to the original correct value, and the white balance is adjusted. Is corrected, but as a specific method for correcting the white balance by setting the gain in this manner, a correction method similar to the above-described black balance correction is employed.

That is, as adjustment amounts for white balance correction, adjustment amounts Y _x corresponding to ΔY, Δ (RY) and Δ
(B-Y) and the corresponding and the use of the R-Y axis component _of R _x and B-Y axis component B _x in the chromaticity plane, these adjustment amounts Y _x, R _x, and B _x ( 13) to (15), which are the reciprocals of the expressions obtained by substituting into the expressions (16) to (15).
The three gain control signals W _R and W given by equation (18)
_G, so as to form a W _B. If circuits for controlling the gains of the R, G, and B signals with these gain control signals are provided, the gain control signals W _R , W _G , and W _X are adjusted by adjusting Y _x , R _x , and B _{x. As} the value of _B , 1 / a, 1 / b, and 1 / c can be obtained, respectively, whereby the output of the gain control circuit can accurately output R, G, B signal can be obtained.

[0026] W _R == 1 / _{[1+ (R x + Y x)} / R ] _{... (16) W G = 1} / _{[1+ (0.59Y x -0.3R x -0.11B x} ) / 0. 59G] _{... (17) W B = 1} / _{[1+ (Y x + B x)} / B ] ... (18)

When the adjustment is actually performed by such a method, the color shifts (Δ (RY) and Δ (BY)) are detected from the screen where the white balance is shifted, and R is detected. _x , B
_Although it is possible to adjust _x , there is a problem that it is extremely difficult to judge a luminance shift (ΔY). However, in general, even if luminance is adjusted by changing The adjustment will be performed using the characteristic that the balance is not affected.

That is, generally, the picture changes (R,
G, B signal is p times) respectively Y _P values of signal when a, (R-Y) _P, if (B-Y) _P, equation (1)
From the formula,

[0029]

(Equation 4)

Thus, Y _p , (RY) _p , (B−
Y) The values of _p are the original signals Y, RY, BY, respectively.
Is uniformly multiplied by p, no change appears in the white balance, and it can be seen that changing the picture does not affect the white balance.

Therefore, when correcting the white balance based on the above equations (16) to (18), this characteristic is used, and first, the color shift is corrected on the assumption that there is no luminance shift on the screen. Then, a method of adjusting the luminance to an appropriate level by adjusting the picture is adopted.

[0032] Each gain control signal W _R of the case of correcting the white balance by this method, W _G, when obtaining the W _B, (16) - (18), by placing a Y _X = 0, _{W R = 1 / (1 +} R x / R) ... (19) W G = 1 / _{[1- (0.3R x + 0.11B x)} /0.59G ] _{... (20) W B = 1} / (1 + B x / B) (21) is obtained.

Here, the equations (19) to (21) indicate that the signal value in a state where the white balance is maintained at the reference color temperature is R,
It is derived for the purpose of correcting the white balance of the color portions such as G and B, but actually (1
The expressions 9) to (21) can be applied not only to such a color portion but also to a case where the white balance is corrected while observing any other color portion.

That is, in general, when white balance is corrected, it can be considered that the color temperature is fixed to a constant value, and the values of a, b, and c are functions of the color temperature. Therefore, when the white balance is corrected, the values of the gain control signals (1 / a, 1 / b, 1) determined by the values of a, b, and c are independent of the content of the video signal. And 1 / c) are constant regardless of the content of the video signal. Therefore, when the white balance is corrected using the gain control signals obtained from the equations (19) to (21) by adjusting R _X and B _X , the white balance is adjusted regardless of which color portion on the screen is observed. It is possible to correct. However, in actual adjustment, it is easy to make adjustments while observing the achromatic portion in consideration of the difficulty of judging the colors for adjustment.

As a specific example of the equations (19) to (21), a simple form is desirable. For example, in the case of an all white signal, since R = G = B = 1, 19)-
(21) _{equation, W R = 1 / (1} + R x) ... (22) W G = 1 / _{[1- (0.3R x + 0.11B x)} /0.59 ] ... (23) W _B = 1 / (1 + B _x ) (24)

Lastly, a supplementary explanation will be given of the drawback when white balance is corrected using the conventional white balance correction device shown in FIG. First, Y, R-
Y, BY, and the signal value Y ′ when the white balance is shifted,
When examining the relationship between (RY) 'and (BY)', from the expression of [Equation 1],

[0037]

(Equation 5)

Therefore, when the matrix operation is performed by substituting the expression of [Equation 5] into the expression of [Equation 3],

[0039]

(Equation 6)

Is obtained. However, _{where, A 11 = 0.3a + 0.59b +} 0.11c A 12 = 0.3a-0.59 × 0.51b A 13 = 0.11c-0.59 × 0.19b A 21 = 0.7a- _{0.59b-0.11c A 22 = 0.7a +} 0.59 × 0.51b A 23 = 0.59 × 0.19b-0.11c A 31 = 0.89c-0.3a-0.59b A 32 = 0.59 × 0.51b−0.3a A ₃₃ = 0.59 × 0.19b−0.89c

Accordingly, the white balance deviation amounts ΔY, Δ
(RY) and Δ (BY) are given by the following equation (6): ΔY = Y′−Y = (A ₁₁ −1) Y + A ₁₂ (RY) + A ₁₃ (BY) (25) Δ (RY) = (RY) ′ − (RY) = A ₂₁ Y + (A ₂₂ −1) (RY) + A ₂₃ (BY) (26) Δ ( (B−Y) = (B−Y) ′ − (B−Y) = A ₃₁ Y + A ₃₂ (R−Y) + (A ₃₃ −1) (B−Y) (27)

Considering the correction of the white balance by the apparatus shown in FIG. 7, no correction is made for the luminance signal in this apparatus.
It goes without saying that Y cannot be corrected, but in the correction of the shift of the color difference signal in the device, the addition of the modulation output of the luminance signal to the color difference signal as a correction amount means that the above equation (26) is used. And the deviation Δ expressed by equation (27)
It only means to correct (remove) the A ₃₁ Y and A ₂₁ Y terms contained in (RY) and Δ (BY), and these are included in these deviations. RY and B
The term proportional to the level of -Y cannot be corrected.

That is, when trying to adjust the balance of a chromatic portion where RY and BY have a value other than 0, for example, a portion of skin color or the like, the white balance correction device shown in FIG. The drawback is that you can't do it.

Specific Circuit Configuration and Correction Procedure FIG. 1 shows an example of a block diagram when white balance is corrected using the video signal correction device of the present invention, and FIG. 2 shows the configuration of the data converter in FIG. .

In FIG. 1, reference numeral 1 denotes a video signal correction device according to the present invention, and a video signal input from a video camera to an input terminal 2 is first converted into R, G,
It is converted to a B signal. The decoded R, G, and B signals are then converted into digital data by A / D converters 4 to 6, and are subtracted by DC levels 7 to 9 and gain multipliers 10 to 12 , And through the multipliers 13 to 15 for picture correction, the signals are returned to the R, G, B signals again by the D / A converters 16 to 18, and further converted to the original video signals by the encoder 19. Later, output terminal 2
0 is supplied to the monitor to display a color image.
Then, the output of the first data converter 26 in the offset adjustment circuit 21 is applied to the subtracters 7 to 9 for DC level correction to correct the black balance, and the gain is supplied to the multipliers 10 to 12 for gain correction. The output of the second data converter 32 in the adjustment circuit 27 is applied to correct the white balance, and the picture correction output of the digital correction data generator 31 is applied to the multipliers 13 to 15 for picture correction. Picture correction is performed.

Here, the first data converter 26 corresponds to FIG.
As shown in FIG. 2A, the operations of equations (7) to (9) are performed, and as shown in FIG. 2B, the second data converter 32 executes the operations of (22) to (24). ) Formula is calculated. Further, the specific structure of the joysticks A and B may be, for example, as shown in FIG. 8, and by referring to the color displayed around the operation lever, the amount and the hue to be corrected can be easily determined. You can judge.

A specific procedure for correcting the white balance by the video signal correction device shown in FIG. 1. Correction of black balance 1-1. Offset adjustment While observing the black area on the screen,
By operating the 1 brightness adjustment volume 22,
R, corrected black floating (offset) by adjusting the Y _B to be applied evenly G, to B signals, to remove the luminance deviation [Delta] Y.

1-2. Adjust the volume 23 and 24 suitably by operating the joystick A color shift adjustment offset adjustment circuit 21 of the black, so as to cancel the color components with the black portion of the screen, sets the correction amount R _B, B _B I do.

2. White Balance Correction While watching the achromatic portion to be corrected on the screen, operate the joystick B of the gain adjustment circuit 27 to adjust the volumes 28 and 29 appropriately to cancel the color components attached to the achromatic portion. The correction amounts R _X and B _X are set. 3. Picture adjustment The picture adjustment volume 30 is operated to adjust the achromatic portion to have a desired luminance.

In the offset adjustment circuit and the gain adjustment circuit shown in this figure, the correction data R _B , B _B ,
Although the joystick is used as a means for setting R _X and B _X , any other means can be used as long as the means can set and display a two-dimensional amount.

The offset adjustment circuit 21 and the gain adjustment circuit 27 shown in the figure are provided with dedicated joysticks A and B, respectively. As shown in FIG. 3, the set amounts R _B and B at the time of offset adjustment are provided. _B and memories 41 and 42 for storing set amounts R _X and B _X at the time of gain adjustment, respectively.
And the changeover switches 43 and 44 are provided, the changeover switches 43 and 44 are switched in accordance with the adjustment so that 1
One joystick can be used for both offset adjustment and gain adjustment.

[0052] Similarly, the brightness adjusting volume and picture adjustment volume, by providing the brightness adjustment amount Y _B and memory for each stored picture adjustment amount p, and the switch, a picture volume when the gain adjustment one volume When the offset is adjusted, it can also be used as a luminance volume.

Further, as shown in FIG. 4, one joystick is used not only for offset adjustment and gain adjustment, but also for one converter, the first data converter 26 and the second data converter 26 shown in FIG. It may be configured to realize both functions of the data converter 32.

The operation of the circuit shown in FIG.
51 to 57 are all connected to the H terminal during offset adjustment.
It is operated to connect, and at the time of gain adjustment,
All are operated to be connected to the G terminal side.
61 to 63 output the reciprocal of the input signal (for example, input
When the force signal is e, 1 / e is output).
Has formed. This allows the data to be adjusted during offset adjustment.
Adjustment amount from the digital correction data generator to the data converter
R_B, B_BAnd Y supplied from the H terminal of the switch 51.
_BAre input to the output sides of the adders 64-66.
At the time of offset adjustment expressed by the above equations (7) to (9)
Operation outputs α, β, and γ appear, and these are the switches 52 to 5.
4 and the memory 67. Also, gain adjustment
Sometimes the amount of adjustment from the digital correction data generator
R_x, B_xAnd a constant supplied from the G terminal of the switch 51.
The number "1" is input to the data converter, and the reciprocals 61 to 6
3 on the output side are represented by the above equations (22) to (24).
Output W during gain adjustment _R, W_G, W_BGot
This is via switches 55-57 and memory 68
Output 46.

The video signal correction apparatus described above uses a joystick to set two independent axis components on a chromaticity plane as an adjustment amount, and performs two-dimensional correction. By simplifying this, the adjustment amount may be set only on one phase axis on the chromaticity plane by using one volume. An example of this case will be described. FIG. 5 shows an explanatory diagram in a case where the adjustment amounts _Rx and _Bx are set on the axis of the phase θ on the chromaticity plane. When the adjustment amount R _x is set, the adjustment amount B _x corresponding to this is set to R
_x / tan θ.

As a specific example, when using the red-cyan axis, θ = 103.5 °, and when using the yellow-blue axis, θ = 103.5 °.
It may be set to 167.6 °. Further, as a modification, the value of θ is automatically changed depending on whether the adjustment amount _Rx is positive or negative. For example, when _Rx ≧ 0, θ = 10
If it is designed to be 3.5 ° and θ = 167.6 ° when R _x <0, it is possible to perform correction in two phase axis directions.

[0057]

According to the present invention, in a video signal correction apparatus for correcting a white balance of an input video signal, two-dimensional adjustment amount setting means for setting an offset adjustment amount and a gain adjustment amount of the input video signal, The offset adjustment amount set by the two-dimensional adjustment amount setting means for performing the black balance adjustment of the video signal and the gain adjustment amount set by the two-dimensional adjustment amount setting means for performing the white balance adjustment of the video signal are data. Since it has a data converter for conversion and a conversion output from the data converter and R, G, and B signals, and a correction circuit for correcting the R, G, and B signals by the converted output, the correction target Are the R, G, and B signals, and the amount of the offset adjustment and the amount of the gain adjustment to be performed for each of the R, G, and B signals are determined for each color. A video signal correction device that can be accurately derived by data conversion based on the axial component, and thus can correct the white balance deviation with sufficiently high accuracy compared to a conventional device that corrects a color difference signal. Can be obtained.

In the present invention, since the two-dimensional adjustment amount setting means has a chromaticity display surface, in addition to the above-described effects, the correction amount set by the operator for correcting the white balance is: It can be set as each color difference axis component on the chromaticity plane that is easy to grasp visually, so that the white balance can be corrected easily without using a special measuring instrument. A video signal correction device capable of correcting the deviation of the image signal can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of one embodiment when white balance is corrected using a video signal correction device of the present invention.

FIG. 2 is a diagram showing a configuration of a data converter in FIG.

FIG. 3 is a diagram showing an embodiment in which one joystick is used for both offset adjustment and gain adjustment.

FIG. 4 is a diagram showing an embodiment in which one data conversion path is used for both offset adjustment and gain adjustment.

FIG. 5 is a diagram for explaining another embodiment of the present invention.

FIG. 6 is a diagram showing a conventional business white balance adjustment device.

FIG. 7 is a diagram showing a conventional consumer white balance adjustment device.

FIG. 8 is a diagram for explaining a joystick used in a conventional consumer white balance adjustment device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Video signal correction device, 7-9 ... Subtractor, 10
~ 15 ... Multiplier, 21 ... Offset adjustment circuit,
25: gain adjustment circuit, 26: first data converter, 32: second data converter

Claims (2)

(57) [Claims] 1. A video signal correction device for correcting a white balance of an input video signal, comprising: two-dimensional adjustment amount setting means for setting an offset adjustment amount and a gain adjustment amount of the input video signal; The offset adjustment amount set by the two-dimensional adjustment amount setting means for performing the balance adjustment, and the gain adjustment amount set by the two-dimensional adjustment amount setting means for performing the white balance adjustment of the video signal. It has a data converter for performing data conversion, and a correction circuit that receives a conversion output from the data converter and R, G, and B signals and corrects R, G, and B signals with the conversion output. Video signal correction device. 2. The video signal correction device according to claim 1, wherein said two-dimensional adjustment amount setting means has a chromaticity display surface.