JPH08146915A - White balance adjusting device - Google Patents

Abstract

PURPOSE: To enable white balance adjustment of the videos to be projected mainly by a PDP, etc. CONSTITUTION: This white balance adjusting device of the video signals composed of respective red, blue and green digital signals is provided with gamma correction sections 1a for making the required gamma correction, high luminance side level varying means (multipliers 1b) for varying the level of the components within the required range on the high luminance side of the video signals from these gamma correction sections, low luminance side component extracting means (subtractors 1c) for taking out the components out of the video signals from the gamma correction section in such a manner that the level is higher with the components of the lower video level, low luminance side level varying means (multipliers 1d) for varying the level of the signal components extracted by this low luminance side component extracting means and adders 1e for adding the signals from the high luminance side level varying means and the signals from the low luminance side level varying means for each of the respective red, blue and green digital signals. The required white balance is adjusted by varying the high luminance side level or the low luminance side level for each of the respective signals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a white balance adjusting device, and more particularly to white balance adjusting of a projected image by a PDP (plasma display panel) or the like.

[0002]

2. Description of the Related Art A video signal displayed by a PDP or the like is composed of red (R), blue (B) and green (G) digital signals. Generally, gamma (γ) correction is applied to these video signals. I do. In this case, in many cases, the gamma correction characteristic is changed for each color signal so that the white balance is also corrected. FIG. 3A is a diagram showing the principle configuration of gamma correction which also serves as white balance correction in the related art. In the figure, ROMs 11, 12, and 13 for gamma (γ) correction are provided for each of the R, G, and B signals, and gamma correction is performed respectively. In this case, each correction ROM has its own gamma correction characteristic so that the white balance becomes appropriate. For example, as shown in FIG. 3B, the input / output conversion characteristic (= gamma correction characteristic) a is set for the G signal and the B signal, and the conversion characteristic b is set for the R signal. This conversion characteristic is premised on a PDP in which red has high luminous efficiency with respect to blue and green on the high luminance side. Therefore, the high-luminance side of the R signal is output at a lower level than the other two colors. Thus, when writing the input / output conversion characteristics in the ROM in advance, the luminous efficiency of each color in the standard PDP is taken into consideration.

[0003]

However, the above-mentioned conventional method (FIG. 2) has a fixed conversion characteristic on the premise of a PDP having a standard emission characteristic. Therefore, if there are variations in the light emission characteristics among the individual PDPs, the adjustment cannot be performed, and the white balance varies as it is. The present invention has been made in view of such a background, and an object of the present invention is to provide a white balance adjusting device capable of adjusting white balance so as to cope with variations in light emission characteristics between PDPs.

[0004]

The present invention provides a video signal composed of red, blue and green digital signals,
A gamma correction unit for performing a required gamma correction, a high-luminance-side level changing unit that changes the level of a component in a required range on the high-luminance side in the video signal from the gamma correction unit, and a video signal from the gamma correction unit Low-luminance side component extraction means for extracting the component with a lower image level such that the level becomes higher, low-luminance side level varying means for varying the level of the signal component extracted by the low-luminance side component extraction means, and the high luminance An adding means for adding the signal from the side level varying means and the signal from the low luminance side level varying means is provided for each of the red, blue and green digital signals, and the high luminance side level or low level is provided for each signal. (EN) A white balance adjusting device for adjusting a required white balance by changing a brightness side level.

[0005]

A predetermined gamma correction is performed for each of red, blue and green signals (gamma correction section). This correction itself may be the same as the conventional one. The gamma-corrected signal for each signal is sent to the multiplier (first multiplier) and the subtractor for each signal. The former multipliers can change the output level by changing the multiplication coefficient from the outside, but the changing range is mainly on the high-luminance side. On the other hand, each of the latter subtractors calculates the subtraction between the maximum level value of the video signal and the level after gamma correction for each signal. By this subtraction, a signal having a larger level is obtained as the luminance component is lower. The output of each subtractor is sent to the multiplier for each signal (referred to as the second multiplier), and the multiplication coefficient is changed from the outside in the same manner as described above. This variable range is mainly on the low luminance side. The white balance is adjusted by changing the above multiplication coefficient. Then, by adding the first multiplier and the second multiplier for each signal, a signal having a required level from the low luminance component to the high luminance component can be obtained.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A white balance adjusting device according to the present invention will be described below with reference to the drawings. 1 is a block diagram of essential parts showing an embodiment of a white balance adjusting apparatus according to the present invention, and FIG.
FIG. 3 is an input / output conversion characteristic diagram for explaining In FIG. 1, R, G, and B are red, green, and blue digital video signals (hereinafter referred to as R signal, G signal, and B signal), 1 is a gamma correction for R signal and white, which includes the following: This is a balance adjustment block (hereinafter referred to as "R adjustment block").

Reference numeral 1a is an R signal gamma correction unit for performing a predetermined gamma correction on the input R signal, and 1b is a first multiplier for multiplying the video signal level from the gamma correction unit 1a by a set multiplication coefficient Kr1. 1c is a subtractor for subtracting the maximum level value of the video signal from the video signal level from the gamma correction unit 1a, 1d
Is a second multiplier that multiplies the video signal level from the subtractor 1c by the set multiplication coefficient Kr2, and 1e adds the signal from the first multiplier 1b and the signal from the second multiplier 1d. It is an adder. Further, 2 and 3 are gamma correction and white balance adjustment block (G adjustment block) for G signal and G signal correction and white balance adjustment block for G signal, which have the same configuration as the R signal gamma correction and white balance adjustment block 1, respectively. It is a white balance adjustment block (B adjustment block).

Next, the role of each block will be described using the R adjustment block 1. The gamma correction unit 1a performs a predetermined gamma correction similar to the conventional one on the input R signal. In the case of the present invention, since level adjustment is possible as will be described later, there is also a method in which all the gamma correction units for each of the RGB signals have the same characteristics, but considering the efficiency of white balance adjustment, the individual characteristics are averaged. It is a good idea to match the light emission characteristics of various PDPs in advance. The signal after gamma correction is the first
To a multiplier 1b and a subtractor 1c. The first multiplier 1b multiplies the gamma-corrected signal according to the variable multiplication coefficient Kr1. The multiplication coefficient Kr1 is a coefficient for uniformly multiplying individual data, and is set to a required coefficient by changing it by an adjusting operation from the outside. The change in the multiplier output due to the change of the multiplication coefficient Kr1 becomes larger as the signal level becomes higher, that is, at the higher luminance side. Therefore, the multiplier
By varying the multiplication coefficient Kr1 of 1b, it is possible to vary mainly the high-luminance level of the video signal.

On the other hand, the "maximum level value" used for the subtraction in the subtractor 1c is determined by the number of bits forming the digital video signal. For example, when the video signal is composed of 8 bits, the maximum level value is It is "255". By this subtraction, the smaller the video level, the higher the level output from the subtractor 1c. Here, the side having a lower video level means the low luminance side, and thus the lower luminance side component is extracted as a higher level by the above subtraction. The subtraction output of the subtractor 1c is sent to the second multiplier 1d and is multiplied by the variable multiplication coefficient Kr2. Like the multiplication coefficient Kr1, the variable multiplication coefficient Kr2 is also a coefficient that uniformly multiplies individual data, and is also set by changing it externally by an adjusting operation. The output change of the multiplier due to the change of the multiplication coefficient Kr2 becomes larger as the level of the subtracter 1c becomes larger, that is, as the brightness becomes lower.

Therefore, by varying the multiplication coefficient Kr2 of the multiplier 1d, mainly the low-luminance side level of the video signal can be varied. However, the multiplication coefficient Kr2 of the second multiplier 1d is a coefficient close to "zero", and is zero when no adjustment is required. On the other hand, the multiplication coefficient Kr1 of the first multiplier 1b is a coefficient close to "1" and is "1" when no adjustment is required. By adding the output of the first multiplier 1b and the output of the second multiplier 1d by the adder 1e, a level-variable R output can be obtained. G adjustment block 2 and B adjustment block 3
Also in the same manner as above, gamma correction and level change (white balance adjustment) are performed for the G signal and the B signal in the former and the latter, respectively. Kg1 and Kb1 in the figure correspond to Kr1 and Kg2 and Kb2.
Corresponds to the same Kr2.

Next, as a concrete example, a case of adjusting the white balance toward red to an appropriate white balance will be described with reference to FIG. The input / output level value in each figure is 8 as an example.
The video signal has a bit structure. FIG. 2A is an input / output conversion characteristic diagram for gamma correction. In this example, RGB is used.
Same characteristics (a). Since the white balance is closer to red from the above example, first, the level of the red component on the high luminance side is lowered. Therefore, the multiplication coefficient Kr1 of the R adjustment block 1 is set to, for example, "0.95". Further, the multiplication coefficient Kr2 is set to zero. This is because the red component is further emphasized when Kr2 is set to a coefficient other than zero. By this setting, the R output becomes as indicated by the symbol B in FIG. 9B, and the R signal level on the high luminance side with respect to B and G decreases.

However, since the low-luminance side cannot be further reduced, the levels of the other two signals (G, B) are increased accordingly. Therefore, the multiplication coefficients Kg2 and Kb2 of the G adjustment block 2 and the B adjustment block 3 are set to required coefficients (for example, "0.
05 ”). As a result, a signal component of the level indicated by the symbol C in FIG. 7C is obtained from each second multiplier. Since this signal component is added to the signal from the first multiplier by the adder, the B signal and the G signal are emphasized relative to the R signal, as indicated by symbol D in FIG. It will be. From the above, it is possible to adjust to an appropriate white balance from the low brightness side to the high brightness side. The adjusted input / output conversion characteristics (outputs of the respective adders) are as shown in FIG. 7E, in which symbol B is the R signal, and symbol D is the B signal and the G signal. Note that the actual white balance adjustment (multiplication coefficient setting) method is to adjust the RGB output level to a predetermined value with a measuring instrument or the like, or adjust it while viewing the image on the screen.

[0013]

As described above, according to the present invention, P
It is possible to adjust the image white balance in the DP or the like to an appropriate state according to the variation in the light emission characteristics of the PDP or the like. As a result, the conventional method is a fixed method based on the standard PDP, and the adjustment function is not provided, so that the white balance has a variation. However, according to the present invention, the variation is eliminated and each device is adjusted. A uniform white balance can be obtained between them. Therefore, it can be said that the present invention can contribute to improving the performance of a display device equipped with a PDP or the like.

[Brief description of drawings]

FIG. 1 is a principal block diagram showing an embodiment of a white balance adjusting apparatus according to the present invention.

FIG. 2 is a gamma correction characteristic diagram for explaining FIG. 1 (A to E).

FIG. 3A is a main part block diagram showing an example of a conventional gamma correction device that also serves as white balance, and FIG. 3B is a gamma correction characteristic diagram for explaining the same.

[Explanation of symbols]

1 R (red) signal gamma correction and white balance adjustment block 1a R signal gamma correction unit 1b First multiplier 1c Subtractor 1d Second multiplier 1e Adder 2 G (green) signal gamma correction And white balance adjustment block 3 Gamma correction and white balance adjustment block for B (blue) signal

Claims (5)

[Claims] 1. A gamma correction unit for performing a required gamma correction in a video signal composed of red, blue and green digital signals, and a required range on the high luminance side of the video signal from the gamma correction unit. High-luminance side level varying means for varying the level of the component, low-luminance side component extracting means for extracting from the video signal from the gamma correction unit so that the component having a lower video level becomes higher in level, and the low-luminance side component The low-luminance side level varying means for varying the level of the signal component extracted by the extracting means, and the adding means for adding the signal from the high-luminance side level varying means and the signal from the low-luminance side level varying means to the red It is provided for each digital signal of blue, green, and green, and the required white balance is adjusted by changing the high-luminance side level or low-luminance side level for each signal. A white balance adjusting device characterized by being adjusted. 2. The high-luminance side level changing means is provided with a multiplier to which the video signal from the gamma correction section is input.
2. The white balance adjusting device according to claim 1, wherein an output level of the multiplier is varied by varying a multiplication coefficient of the multiplier. 3. The low-luminance-side component extracting means is constituted by a subtractor that subtracts the maximum level value of the video signal from the level of the video signal from the gamma correction unit. The described white balance adjustment device. 4. The low-luminance-side level varying means is provided with a multiplier to which the video signal from the low-luminance-side component extracting means is input, and the multiplication coefficient of the multiplier is varied to output the same multiplier output level. 2. The white balance adjusting device according to claim 1, wherein the white balance adjusting device is variable. 5. The white adder according to claim 1, wherein the adding means is an adder for adding a signal from the high brightness side level changing means and a signal from the low brightness side level changing means. Balance adjustment device.