JP2003189326A - White balance correction circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the accuracy of white balance correction for a video display device mainly driven by a digital video signal such as a PDP or an LCD. <P>SOLUTION: The white balance correction circuit is provided with low luminance side correction sections 1, 2, 3 respectively varying a level of only a video signal within a setting black side level as to RGB digital input video signals as a target and high luminance side correction sections 4, 5, 6 respectively varying the level of the entire range of the video signal; the sections 1, 2, 3 and the sections 4, 5, 6 respectively corresponding to the RGB signals. The setting range for the low luminance side correction section 1 or the like is selected to be a range of a black side level being at most 50% or below with respect to 100% white level of the video signal. Further, the low luminance side correction section 1 or the like and the high luminance side correction section 4 or the like respectively comprise a LUT for storing in advance a plurality of kinds of input output conversion characteristics. Control signals Slr, Slg, Slb for setting the characteristics as to the low luminance side are used to select the input output conversion characteristics, and control signals Shr, Shg, Shb for setting the characteristics as to the high luminance side are used to correct the white balance. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a white balance correction circuit, and more particularly to a video display device driven mainly by a digital video signal such as a PDP (plasma display panel) or LCD (liquid crystal display device). And is related to improvement of accuracy of white balance correction.

[0002]

2. Description of the Related Art Conventionally, the white balance of a video display device driven by a digital video signal such as a PDP or LCD is determined by the gain of each video output stage of R (red), G (green) and B (blue). It was corrected only by adjusting each.
In the correction by the gain adjustment, the white balance changes simultaneously in the entire range from low brightness to high brightness. Therefore, PDP or L
It is a necessary condition for obtaining a uniform white balance that gradation characteristics of a CD or the like are uniform from the low luminance side to the high luminance side. However, the gradation characteristics of an actual PDP or LCD differ between the low-luminance side and the high-luminance side, and therefore the white balance is appropriately corrected simultaneously by the gain adjustment in the entire range from the low-luminance side to the high-luminance side. However, there was a problem that the quality of the white balance was degraded.

[0003]

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a white balance correction circuit suitable mainly for an image display device driven by a digital image signal such as PDP or LCD. .

[0004]

In order to achieve the above-mentioned object, the present invention changes the level of a digital input video signal only for a video signal in a range set as a black side level, and adjusts the white balance on the low luminance side. A white balance comprising a low-luminance correction unit for correction and a high-luminance correction unit for varying the level of the entire range of the video signal and correcting the white balance of the entire range from low luminance to high luminance. A correction circuit is provided.

Further, the range to be set in the low-luminance side correction unit is 50 at most for a video signal of 100% white.
The black level range is less than or equal to%.

Further, the setting of the range of the variable black side level in the low luminance side correction unit is set within the range of the black side level of at most 50% or less with respect to 100% white of the video signal. It is possible to set by arbitrarily selecting from.

Further, the low-luminance side correction unit is configured to selectively set a plurality of types of input / output conversion characteristics which are provided in advance by a control signal.

Further, the low-luminance side correction section is an LUT (Look Up Ta) that stores a plurality of types of input / output conversion characteristics in advance.
ble).

Further, the high-luminance side correction unit is configured to selectively set a plurality of types of input / output conversion characteristics, which are provided in advance, by a control signal.

The high-luminance side correction unit is an LUT in which a plurality of types of input / output conversion characteristics are stored in advance.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings based on examples. FIG. 1 is a block diagram of an essential part showing an embodiment of a white balance correction circuit according to the present invention, in which the form of a digital input video signal is R (red) or G.
(Green) and B (blue) signals. FIG. 2 is a principal block diagram showing another embodiment of the white balance correction circuit according to the present invention. FIG. 3A shows the low-luminance side correction units 1, 2, 3 or the high-luminance side correction units 4, 5, 6 of FIG.
FIG. 3B is a block diagram of a main part showing an embodiment of the present invention, and FIG. 3B is a block diagram of a main part showing an embodiment of the low-luminance side correction parts 11, 12, and 13 of FIG. FIG. 4 is an example of a video signal input / output conversion characteristic diagram for explaining the white balance correction circuit of FIG. 1 or 2. In FIG. 1, 1 to 3 are low-luminance side correction units for each RGB signal, and 4 to 6 are same / high-luminance side correction units. Further, in FIG. 2, the same components as those in FIG. 1 are denoted by the same reference numerals, and 11 to 13 are low-luminance side correction units for each RGB signal.

Next, the operation of the present invention will be described. First, FIG. 1 will be described. The RGB input video signals are input to the low-luminance side correction units 1, 2 and 3, respectively, and the level of the input video signals is varied only for the video signals in the range preset as the black level. , Corrects the white balance on the low brightness side and outputs. The above correction is performed by inputting control signals Slr, Slg and S for characteristic setting.
It is done by lb. The RGB image signals whose white balances on the low luminance side have been corrected by the low luminance side correction units 1, 2 and 3 are input to the high luminance side correction units 4, 5 and 6, respectively, and the same input image is input. With respect to the signal, the level of the entire range from the low brightness side to the high brightness side is varied, and the overall white balance is corrected and output. The same correction is performed by the input characteristic setting control signals Shr, Shg, and Shb. However, the above description follows the flow of signals, and in the actual white balance correction, it is desirable that the above-mentioned correction on the low luminance side and the above-mentioned correction are alternately repeated as appropriate. As described above, by having the function of correcting the white balance on the low luminance side in addition to the correction of the overall white balance, the accuracy of the overall white balance correction is improved, and the quality of the white balance can be improved.

Next, FIG. 2 will be described. The configuration of FIG. 1 limits the correction range of the low-luminance side correction units 1, 2, and 3 to one type. On the other hand, in the configuration of FIG. 2, the low-luminance side correction range can be variably set. For example, for 100% white, several types of ranges are provided within a range of 50% or less, and it is possible to select and set from these ranges. This range selection is set by the illustrated range setting control signal Sc. After the same setting, the operation is similar to that of FIG.

Next, the low-luminance side correction units 1, 2, 3 and the high-luminance side correction units 4, 5, 6 of FIG. 1 will be described with reference to FIGS. 3 (A) and 4. The low-luminance side correction units 1, 2, 3
The high-brightness side correction units 4, 5, and 6 have the same configuration itself on the block diagram, and are represented by FIG. When FIG. 3A shows the low-luminance side correction units 1, 2, and 3, the memory unit 11 stores a plurality of types of input / output conversion characteristics in advance, and a so-called LUT (Look Up Tabl).
e). FIG. 4A shows an example of the plurality of types of input / output conversion characteristics, which is 100%.
A plurality of input / output conversion characteristics are provided within the range of the black side level (low brightness side) of 50% or less with respect to white. The input / output conversion characteristics include one-to-one conversion characteristics (referred to as reference characteristics), as well as conversion characteristics for increasing the input level with respect to the reference characteristics and lowering the input level. Plural kinds of conversion characteristics to be output are provided.

FIG. 4A shows the above-mentioned conversion characteristics of which the input level is raised and output are m types, and the conversion characteristics of which the input level is lowered and output are n types. The range connecting the input axis a and the output axis a in FIG. 4A is the input / output conversion range, which is the white balance correction range on the low luminance side.
Further, the selection from the plurality of types of input / output conversion characteristics is made by inputting the control signals Slr, S for setting characteristics for each RGB.
Follow lg and Slb. Therefore, the memory unit 21 stores the same control signal and each of the plurality of types of input / output conversion characteristics in association with each other. Therefore, when the control signal Slr or the like is input, the control unit 22 reads the input / output conversion characteristic corresponding to the control signal Slr or the like from the memory unit 21, and the input video signal is leveled by the conversion unit 23 according to the conversion characteristic. Convert and output. It is possible to correct the white balance on the low luminance side by individually changing the control signals Slr, Slg, and Slb.

Next, referring to FIG. 3A, the high-luminance side correction unit 4,
In the case of 5 and 6, a plurality of types (N types) of input / output conversion characteristics illustrated in FIG. 4B are stored in the memory unit 21 in advance. The memory unit 21 in this case is also a so-called LUT.
(Look Up Table). As can be understood from the figure, the input / output conversion characteristic of FIG. 4B is for converting the level of the entire range of the video signal, and white balance correction is performed for the entire range from the low luminance side to the high luminance side. .
However, as can be understood from the characteristic diagram, the white balance correction on the high luminance side tends to be stronger than on the low luminance side. Further, the selection from the plurality of types of input / output conversion characteristics is made by inputting the control signals Shr, Shg, Shb for setting the characteristics for each RGB.
Follow Therefore, the same control signal and each of the plurality of types of input / output conversion characteristics are stored in the memory unit 21 in association with each other, and these control signals Shr, Shg, Shb are individually changed, so that the entire image is displayed. Correct the white balance. The operation other than the memory section 21 is the same as that of the low-luminance side correction, and the description thereof is omitted.

Next, the low-luminance side correction units 11, 12, and 13 in FIG. 2 will be described with reference to FIGS. 3 (B) and 4. Figure 3
As described above, the low-luminance side correction unit (B) is capable of variably setting the low-luminance side range for white balance correction. Therefore, a plurality of types of input / output conversion characteristics of the same kind as the storage data of the memory unit 21 of FIG. 3A are stored in the memory unit 31 in advance by changing the range of the black side level. An example in which this range is changed is shown in FIG.
4A. In FIG. 4C, 100% is white and 50% or less is the black side level as the adjustment range.
The adjustment range is a black level of approximately 25% or less with respect to white. The fact that a plurality of input / output conversion characteristics are provided in this range is the same as in the case of FIG. 4A.
The black level adjustment range connects the input shaft b and the output shaft b in (C). Further, FIG. 4C shows m types of conversion characteristics for increasing the input level for output, and n types of conversion characteristics for decreasing the input level for output.

FIG. 4C is an example. In addition to this, a plurality of types of adjustment ranges having different ratios are set, and these adjustment ranges are associated with the range setting control signal Sc and the memory section is set.
Pre-store in 31. In addition to the above, the memory unit 31 stores a plurality of types of input / output conversion characteristics associated with the characteristic setting control signal Slr and the like as in the case of FIG. 4A. The subsequent operation is basically shown in FIG.
Similar to the case of (A), when the control signals Sc, Slr, etc. are input, the control unit 32 reads out the input / output conversion characteristics in the range corresponding to the control signals Sc, Slr, etc. from the memory unit 31, The input video signal is level-converted by the conversion unit 33 according to the conversion characteristic and output. As described above, the accuracy of white balance correction on the low luminance side can be improved as compared with FIG.

[0019]

As described above, according to the present invention, the white balance correction is performed from both the low luminance side of the video signal and the entire video signal. Therefore, digital balance such as PDP or LCD is used. It is suitable for a video display device driven by a video signal, and white balance accuracy and quality can be improved.

[Brief description of drawings]

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

FIG. 2 is a principal block diagram showing another embodiment of the white balance correction circuit according to the present invention.

3A is a block diagram of essential parts showing one embodiment of the low-luminance side correction units 1, 2 and 3 or the high-luminance side correction units 4, 5 and 6 of FIG. 1, and FIG. FIG. 3 is a block diagram of essential parts showing an embodiment of low-luminance side correction units 11, 12, and 13.

4 is an example of a video signal input / output conversion characteristic diagram for explaining the white balance correction circuit of FIG. 1 or FIG.

[Explanation of symbols]

1, 2, 3, 11, 12, 13 Low-brightness correction unit 4, 5, 6 High-brightness correction unit 21, 31 Memory unit 22, 32 Control unit 23, 33 Conversion unit Slr, Slg, Slb, Shr, Shg , Shb Characteristic setting control signal Sc Range setting control signal

Claims (7)

[Claims] 1. A low-luminance side correction unit that corrects the white balance on the low-luminance side by varying the level of the digital input video signal only for the video signal in the range set as the black-side level; A white balance correction circuit comprising: a high-luminance side correction unit that varies the level of the entire range and corrects the white balance of the entire range from low brightness to high brightness. 2. The set range in the low-luminance side correction unit is a range of a black side level of at most 50% or less with respect to 100% white of a video signal.
The white balance correction circuit described. 3. The setting of the range of the variable black-side level in the low-luminance side correction unit is within a plurality of ranges set in a range of the black-side level of 50% or less with respect to 100% white of a video signal. 2. The white balance correction circuit according to claim 1, wherein the white balance correction circuit can be arbitrarily selected and set. 4. The low-luminance side correction unit is configured to selectively set a plurality of types of input / output conversion characteristics, which are provided in advance, by a control signal.
The white balance correction circuit according to any one. 5. The LUT (Look Up Table) in which the low-luminance side correction unit stores a plurality of types of input / output conversion characteristics in advance.
5. The white balance correction circuit according to claim 4, comprising: 6. The white balance correction circuit according to claim 1, wherein the high-luminance side correction unit is configured to selectively set a plurality of types of input / output conversion characteristics provided in advance by a control signal. 7. The white balance correction circuit according to claim 6, wherein the high-luminance side correction unit is composed of an LUT in which a plurality of types of input / output conversion characteristics are stored in advance.