Liquid-crystal display device and drive control circuit

In a case where each of pixels of a liquid-crystal display panel is divided into two subpixels, the drive levels of the subpixels with respect to the gradation of an input video signal can be selected from among a plurality of drive levels while an increase in the circuit scale is suppressed.Thus, in the present invention, a first subpixel driving level converter for, on the basis of the gradation value of each pixel of the input video signal, obtaining a first gradation value for driving a first subpixel is provided, and the first subpixel is driven and controlled on the basis of the first gradation value. Then, the first gradation value obtained by the first subpixel driving level converter is converted into a luminance value, and a difference with the luminance value such that the gradation values of the whole pixels are converted is obtained. The obtained difference is converted into a gradation value, and a second gradation value for driving a second subpixel is obtained. The second subpixel is driven and controlled on the basis of the second gradation value.

This application is a 371 of PCT/JP2008/056125, filed Mar. 28, 2008.

TECHNICAL FIELD

The present invention relates to a drive control circuit for controlling the driving of a liquid-crystal display panel in which each of pixels is divided into two subpixels. Also, the present invention relates to a liquid-crystal display device in which each of pixels of a liquid-crystal display panel is divided into two subpixels.

BACKGROUND ART

It is known that, as field of view angle characteristics of a liquid-crystal display device, when the screen is viewed obliquely, a reverse phenomenon occurs such that, as a result of the fact that after the luminance temporarily increases with an increase in the gradation, the luminance is decreased, the luminance increases in an area of a lower gradation than in an area of a higher gradation.

In order to improve such field of view angle characteristics, hitherto, a technology in which each of pixels of a liquid-crystal display panel is divided into two subpixels has been proposed (see, for example, Japanese Unexamined Patent Application Publication No. 2005-316211 published by Japan Patent Office). In this technology, as shown as an example inFIG. 1, a display electrode for one pixel P (a pixel for each of R, G, and B, which are the three primary colors) of a liquid-crystal display panel50is divided into electrodes of two subpixels A and B that are driven by a data driver60independently of each other.

Then, by setting the driving level (gradation at which the subpixels A and B are driven) of the subpixels A and B to mutually different gradations on the basis of the gradation of the input video signal, the luminance characteristics in a case where the whole pixels P are viewed obliquely are made to approach the luminance characteristics in a case where the whole pixels P are from the front.

In Japanese Unexamined Patent Application Publication No. 2005-316211, which is the above-described document, as such a method of setting drive levels of subpixels, it is described that a gradation conversion table in which the gradation of an input video signal is associated with the output gradation of each subpixel is provided.

Incidentally, in a liquid-crystal display device in which each pixel of a liquid-crystal display panel is divided into two subpixels in the manner described above, in order that the balance of the luminances of R, G, and B when viewed obliquely is improved, there is a case in which it is desirable that the drive level of the subpixel be changed in accordance with whether the pixel is R, G, or B.

FIG. 2shows an example of such a case. InFIG. 2(a), gradation-luminance characteristics in a case where the drive levels of the subpixels A and B with respect to the input gradation is set as inFIG. 2(b) and the screen is viewed from the front are depicted as GL11. Also, gradation-luminance characteristics in a case where the drive levels of the subpixels A and B are set as inFIG. 2(b) and the screen is viewed obliquely (angle θ) are depicted as GL12.

Here, for example, the gradation values of R, G, and B are assumed to be 128, 96, and 64, respectively. InFIG. 2(a), also, such gradation values of R, G, and B are depicted. In that case, between the gradation-luminance characteristics GL11and GL12, the ratio of the luminance of R, G, and B when viewed from the front is about 1:2:5, and the ratio of the luminance of R, G, and B when viewed obliquely is about 5:7:10. As a result, when viewed obliquely, since the ratio of the luminance of R becomes small, the red color becomes dark.

InFIG. 2(a), the drive levels of the subpixels A and B with respect to the input gradation are set so as to differ from those ofFIG. 2(b) (here, so the gradation values become equal as inFIG. 2(c)), so that gradation-luminance characteristics when the screen is viewed from the angle θ described above are also depicted as GL13. In the gradation-luminance characteristics GL13, the luminance when the gradation value is 128 is higher than that of the gradation-luminance characteristics GL12.

Accordingly, if the drive levels of the subpixels shown inFIG. 2(b) are selected with respect to the pixels of G and B, and the drive level of the subpixel shown inFIG. 2(c) is selected with respect to only the pixel of R, the ratio of the luminance of R when viewed obliquely is increased (the ratio of the luminances of R, G, and B is approached when viewed from the front). As a consequence, it is possible to improve the balance of the luminances of R, G, and B when viewed obliquely.

FIG. 2shows two sets of gradation values inFIG. 2(b) andFIG. 2(c). If the drive levels of the subpixels for each of the pixels of R, G, and B are selected correspondingly from among three or more types of drive levels shown as an example inFIG. 3, it is possible to even further improve the balance of the luminances of R, G, and B when viewed obliquely.

However, as described in Patent Document 1 described above, in the method in which a gradation conversion table in which input gradations are associated with output gradations so as to allow setting of the drive levels of the subpixels, in order to be able to select a driving level from among a plurality of drive levels, it is necessary to provide a separate gradation conversion table for each driving level. As a result, as shown as an example inFIG. 4, as the number of selectable drive levels is increased, the number of gradation conversion tables for the subpixels A and B increases like TA11and TB11, TA12and TB12, . . . TAm and TBm.

Then, in recent years, since the resolution of the gradation has been increasingly improved so as to improve display performance, the amount of data of one individual gradation conversion table is increased. Provision of many such gradation conversion tables with a large amount of data causes the circuit scale of a RAM for storing gradation conversion tables, or the like to increase.

Further, here, the problem in the case that the driving level is selected from among a plurality of drive levels in accordance with whether the pixel is R, G, or B has been described. Still the same problem also occurs even in a case where, for example, the drive level of a subpixel is selected from among a plurality of drive levels on the basis of the type of the input video signal.

In view of the above-described points, it is an object of the present invention to be capable of selecting the drive level of a subpixel with respect to the gradation of an input video signal from among a plurality of drive levels while suppressing an increase in the circuit scale in a liquid-crystal display device in which each pixel of a liquid-crystal display panel is divided into two subpixels.

DISCLOSURE OF INVENTION

In order to achieve the above-described object, the present invention provides a drive control circuit including:

a first subpixel driving level converter for obtaining, on the basis of a gradation value of each of pixels of an input video signal, a first gradation value for driving a first subpixel among the first and second subpixels arranged in each pixel of a liquid-crystal display panel;

a first luminance value converter for converting a gradation value for driving the first subpixel, the gradation value being converted by the first subpixel driving level converter, into a luminance value;

a second luminance value converter for converting the gradation value of each pixel of the input video signal into a luminance value;

a subtraction unit for calculating a difference between the luminance value converted by the second luminance value converter and the luminance value converted by the first luminance value converter; and

a second subpixel driving level converter for converting the luminance value of the difference subtracted by the subtraction unit into a gradation value and obtaining a second gradation value for driving the second subpixel, and a liquid-crystal display device including the drive control circuit.

In such present invention, in such a manner as to correspond to the gradation of the input video signal, information on the gradation of the first subpixel among the first and second subpixels such that each pixel is divided is obtained by the first subpixel driving level converter. On the basis of the gradation value of the first subpixel obtained by the first subpixel driving level converter, the first subpixel is driven and controlled.

Furthermore, the gradation value of the first subpixel obtained by the first subpixel driving level converter is converted into a luminance value of the first subpixel by the first luminance value converter. In addition, the luminance that is the target as the whole pixels corresponding to the gradation of the input video signal is obtained by the second luminance value converter. Then, the subtraction unit subtracts the luminance of the first subpixel from the luminance that is the target as the whole pixels, thereby obtaining the luminance of the second subpixel. On the basis of the gradation value of the second subpixel obtained by the second subpixel driving level converter, the second subpixel is driven and controlled.

In this case, if the conversion characteristics obtained by the first subpixel driving level converter are changed only, the luminance to be generated by the first luminance value converter will be changed. For this reason, since the difference supplied from the subtraction unit to the second subpixel driving level converter is changed, it is possible to change the drive levels of the two subpixels with respect to the gradation of the input video signal. That is, it is possible to increase the number of selectable drive levels of the subpixels by only increasing variations of the conversion characteristics by the first subpixel driving level converter while the first and second luminance value converters and the second subpixel driving level converter, which perform conversion of characteristics between the gradation and the luminance, are fixed without change.

Therefore, if this drive control circuit is installed into a liquid-crystal display device in which each pixel of a liquid-crystal display panel is divided into two subpixels, it becomes possible to select the drive level of a subpixel with respect to the gradation of an input video signal from among a plurality of drive levels while an increase in the circuit scale is suppressed.

BEST MODE FOR CARRYING OUT THE INVENTION

An exemplary embodiment of the present invention will be described below specifically with reference to the attached drawings.FIG. 5is a block diagram showing the outline of a circuit configuration of a liquid-crystal display device to which an exemplary embodiment is applied. The liquid-crystal display device is provided with a video signal processing circuit20, a timing controller30, a CPU40for controlling the video signal processing circuit20and the timing controller30, a liquid-crystal display panel50, a data driver (data-line driving circuit)60for driving the liquid-crystal display panel50, and a gate driver (scanning-line driving circuit)70.

A video signal input to the liquid-crystal display device from the outside is sent to the video signal processing circuit20. In the video signal processing circuit20, processing, such as extraction of a synchronization signal, IP conversion (conversion from a signal of an interlace method into a signal of a progressive method), scaling (image size conversion in accordance with the resolution of a liquid-crystal panel), or the like, is performed on the input video signal. Then, the video signal that has undergone the processing of the video signal processing circuit20and the synchronization signal extracted by the video signal processing circuit20are sent to the timing controller30.

The timing controller30, as is well known, supplies a video signal (gradation signal), a polarity inversion control signal, and a timing control signal to the data driver60, and also supplies a timing control signal to the gate driver70, thereby controlling the driving of the liquid-crystal display panel50.

The liquid-crystal display panel50is such that, like the liquid-crystal panel shown as an example using the same reference numeral inFIG. 1, a display electrode for one pixel P (pixel) for each of R, G, and B, which are the three primary colors), is divided into electrodes of two subpixels A and B. The data driver60drives the two subpixels A and B independently of each other like the data driver indicated using the same reference numeral inFIG. 1.

The timing controller30has a function of generating a gradation signal to be supplied to the data driver60.FIG. 6is a block diagram showing the configuration of a circuit for generating this gradation signal, within the internal configuration of the timing controller30. A RAM1, a RAM2, a RAM3, a subpixel drive level calculation unit4, and a subtraction circuit5are provided.

The RAM1functions as a converter for converting the gradation values of the whole pixels into luminance values. The RAM1is stored with a look-up table (LUT) in which the gradation values and the luminance values are associated with each other so that the gradation-luminance characteristics GL shown inFIG. 7are represented as target gradation-luminance characteristics (also referred to as “target characteristics”) when the whole pixels P (FIG. 1) are viewed from the front of the screen.

The RAM2functions as a converter for converting the luminance value of one of the subpixels A into a gradation value. The RAM2is stored with a look-up table in which the gradation values and the luminance values are associated with each other so that the gradation-luminance characteristics GLA shown inFIG. 7are shown as the gradation-luminance characteristics of the subpixel A for realizing the target characteristics GL shown inFIG. 7.

The RAM3functions as a converter for converting the gradation value of the other subpixel B into a luminance value. The RAM3is stored with a look-up table in which the gradation values and the luminance values are associated with each other so that the gradation-luminance characteristics GLB shown inFIG. 7are shown as the gradation-luminance characteristics of the subpixel B for realizing the target characteristics GL shown inFIG. 7.

Regarding the gradation-luminance characteristics GLA and the gradation-luminance characteristics GLB, the ratio of the luminance value corresponding to the same gradation value (for example, the ratio of the luminance value f(x)A to the f(x)B corresponding to the gradation value x in the figure) is equal to the ratio of the area of the subpixel A to that of the subpixel B. Furthermore, regarding the gradation-luminance characteristics GLA and the gradation-luminance characteristics GLB, the value (for example, f(x)A+f(x)B in the figure) such that the luminance values corresponding to the same gradation value are added is equal to the luminance value (f(x) in the figure) of the target characteristics GL corresponding to the gradation value.

The subpixel drive level calculation unit4, under the control of the CPU40(FIG. 5), calculates the gradation value of the subpixel B (FIG. 1) corresponding to the gradation value of the video signal to be input to the timing controller30. For the configuration of the subpixel drive level calculation unit4, any one of the configuration examples described below may be adopted.

<Configuration Example Based on Calculation of Subpixel Drive Level Calculation Unit4>

First, a description will be given of an example in which the subpixel drive level calculation unit4is formed by a calculation circuit for multiplication or the like.

For example, as shown inFIG. 8, the subpixel drive level calculation unit4is formed by a calculation circuit10that sets the gradation value of the video signal to be input to the timing controller30to x0and performs power calculation of
x1=x01/n,
and a calculation result x1thereof is used as the gradation value of the subpixel B. In the case of this configuration example, the CPU40supplies a control signal that specifies the value of this n (may not be an integer) to the calculation circuit10.

FIG. 9shows as an example the drive levels of the subpixel B with respect to the gradation of an input video signal in a case where the value of this n is changed in two or more ways. By changing the value of n in two or more ways, it is possible to change the drive level of the subpixel B in two or more ways similarly to that shown as an example inFIG. 3.

FIG. 10shows a specific configuration example of the subpixel drive level calculation unit4using calculation circuits.

In this example, when the gradation value of the video signal to be input to the timing controller30is set as x0and a calculation result x1thereof is set as the gradation value of the subpixel B, the calculation of
x1=x04.25
is performed to obtain the drive level of the subpixel B with respect to the gradation of the input video signal.

The configuration ofFIG. 10will be described. The gradation value x0of the input video signal is supplied to a ½ square circuit111, which is a circuit for calculating a square root, whereby x00.5is obtained. In addition, the output x00.5of the ½ square circuit111is supplied to another ½ square circuit112, whereby an output x00.25is obtained. The output x00.25of the ½ square circuit112is supplied to a multiplication circuit113. Furthermore, the gradation value x0of the input video signal is supplied to a multiplication circuit114so as to obtain a squared output x02. In addition, the squared output x02of the multiplication circuit114is supplied to another multiplication circuit115, whereby a squared output x04is obtained, and the output x04is supplied to a multiplication circuit113.

In the multiplication circuit113, the supplied signal x00.25and signal x04are multiplied to obtain a multiplication output x04.25.

FIG. 11shows still another configuration example of the subpixel drive level calculation unit4using calculation circuits.

In this example, when the gradation value of the video signal to be input to the timing controller30is set as x0and a calculation result x1thereof is set as the gradation value of the subpixel B, the calculation of
x1=x05.625
is performed to obtain the drive level of the subpixel B with respect to the gradation of the input video signal.

The configuration ofFIG. 11will be described. The gradation value x0of the input video signal is supplied in sequence to ½ square circuits121,122, and123, which are circuits for calculating a square root, whereby an output x00.125is obtained. Then, the output x00.5of the ½ square circuit121and the output00.125of the ½ square circuit123are supplied to a multiplication circuit124, whereby a multiplication output x00.625is obtained. The multiplication output x00.625of the multiplication circuit124is supplied to a multiplication circuit125.

Furthermore, by using three multiplication circuits126,127, and128, a multiplication output x05is obtained from the gradation value x0of the input video signal. This multiplication output x05is supplied to the multiplication circuit125.

In the multiplication circuit123, the supplied signal x00.625and signal x05are multiplied together, thereby obtaining a multiplication output x05.625.

FIG. 12shows a generalized circuit for obtaining an arbitrary multiplier number using such multiplication circuits and square root circuits. This example shows a configuration in which the gradation value of an video signal to be input to the timing controller30is set as x0and a calculation result g(x0) is set as the gradation value of the subpixel B, so that the calculation result g(x0) can be set to an arbitrary multiplier number.

In the configuration ofFIG. 12, ½ square circuits131to133, which are circuits for calculating a square root, multiplication circuits134to140, and selectors141to146are provided. The selectors141to146are selection means for selecting one of each signal of the multiplier numbers supplied correspondingly from circuits of previous stages and a signal “1”. By externally controlling the selected states of the selectors141to146, the multiplier number of the output signal g(x0) is determined.

The configuration ofFIG. 12will be described. The gradation value x0of an input video signal is supplied in sequence to the ½ square circuits131,132, and133, which are circuits for calculating a square root, and in the respective ½ square circuits131,132, and133, multiplication outputs x00.5, x00.25, and x00.125are obtained.

The output x00.125of the ½ square circuit133is supplied to the multiplication circuit134via the selector141. The output x00.25of the ½ square circuit132is supplied to the multiplication circuit134via the selector142. In the multiplication circuit134, the outputs of the selectors141and142are multiplied, and the multiplication output is supplied to a multiplication circuit135.

The output x00.5of the ½ square circuit131is supplied to the multiplication circuit135via the selector143. In the multiplication circuit135, the output of the multiplication circuit134is multiplied by the output of the selector143, and a multiplication output thereof is supplied to a multiplication circuit136.

Furthermore, the gradation value x0of the input video signal is supplied to a multiplication circuit137, whereby a squared output x02is obtained. The output x02is supplied to a multiplication circuit138, whereby a further squared output x04is obtained. The output x04of the multiplication circuit138is supplied to a multiplication circuit139via the selector144, and the output x02of the multiplication circuit137is supplied to the multiplication circuit139via the selector145. In the multiplication circuit139, the outputs of the selectors144and145are multiplied, and a multiplication output thereof is supplied to a multiplication circuit140.

Furthermore, the gradation value x0of the input video signal is supplied to a multiplication circuit140via the selector146, and in the multiplication circuit140, the output of the multiplication circuit139is multiplied by the output of the selector146. In addition, the output of the multiplication circuit140is supplied to the multiplication circuit136, and in the multiplication circuit136, the output of the multiplication circuit135is multiplied by the output of the multiplication circuit140.

As a result of being configured as described above, for the multiplication output g(x0) of the multiplication circuit136, any desired power multiplier number can be selected on the basis of the selected state in the selectors141to146. For example, the configuration can be arranged as the subpixel drive level calculation unit shown inFIG. 10, and can also be configured as the subpixel drive level calculation unit shown inFIG. 11. It is possible to freely determine the configuration so that a necessary drive level of a subpixel is obtained.

FIG. 13shows a characteristic example of an input gradation x0and a gradation at which the subpixel B is driven, which is an output gradation, in a case where a power multiplier number is changed in the configuration ofFIG. 12. An example is shown in which the characteristics are a straight line when the power multiplier number is set at x01and in the state, the power multiplier number is changed to x01.5, x02, x02.5, x03, x04, x05, x06, and x07.875.

As can be seen fromFIG. 13, it is possible to freely change the characteristics by changing the processing state in one subpixel drive level calculation unit.

<Configuration Example of Subpixel Drive Level Calculation Unit4Using LUT>

As shown inFIG. 14, an address generation circuit11, a plurality of sets, each set being formed of two RAMs, of RAMs12(RAMs12(1) and12(1′),12(2) and12(2′), . . .12(m) and12(m′)), a data selection circuit13, and a linear interpolation circuit14constitute the subpixel drive level calculation unit4.

The RAMs12of each set are each stored with a look-up table in which discrete gradation values of an input video signal (gradation values more coarse than the resolution of the actual gradation in the liquid-crystal display device) are associated with the gradation values of the subpixel B, and the driving level with respect to the input video signal is made different for each set (the drive levels are made equal in the two RAMs of the same set).

Although these look-up tables are the same as the gradation conversion table described with reference toFIG. 4in that input gradations and output gradations are associated with each other, since only discrete gradation values are stored, it is possible to suppress an increase in the circuit scale even if a plurality of look-up tables are provided.

The address generation circuit11is a circuit for generating, as reference addresses, two gradation values x0−a and x0+b, with the gradation value x0of the input video signal being held therebetween in the look-up table in the RAM12.

The reference address x0−a generated by the address generation circuit11is supplied to the one side (the RAMs12(1),12(2), . . .12(m)) of the RAMs12of each set. The reference address x0+b generated by the address generation circuit11is supplied to the other side (the RAMs12(1′),12(2′), . . .12(m′)) of the RAMs12of each set.

The gradation values read from the look-up tables in the RAMs12of each set on the basis of the reference addresses x0−a and x0+b are sent to the data selection circuit13.

The data selection circuit13is a circuit for selecting gradation values from one set of RAMs from among a plurality of sets of RAMs (two gradation values corresponding to the reference addresses x0−a and x0+b, respectively). In the case of this configuration example, the CPU40(FIG. 5) supplies, to the data selection circuit13, a control signal that specifies the set of the RAMs12to be selected.

The linear interpolation circuit14is a calculation circuit for performing linear interpolation on two gradation values selected by the data selection circuit13on the basis of the ratio of the value a to the value b, which are used for the address generation circuit11to generate the reference addresses, and the interpolation result of the linear interpolation circuit14is set as the gradation value x1of the subpixel B.

Also, in this configuration example, by switching the selections in the data selection circuit13, it is possible to change the drive level of the subpixel B with respect to the gradation value x0of the input video signal in two or more ways similarly to that shown as an example inFIG. 9.

As shown inFIG. 6, the gradation value x0of the video signal that is input to the timing controller30from the video signal processing circuit20(FIG. 5) is supplied as a reference address to the RAM1. The luminance value f(x0) (the luminance value corresponding to the gradation value x0in the target characteristics GL ofFIG. 7) read from the look-up table in the RAM1on the basis of the reference address x0is sent to the subtraction circuit5.

Furthermore, this gradation value x0of the input video signal is also supplied to the subpixel drive level calculation unit4. The gradation value x1of the subpixel B, which is calculated by the subpixel drive level calculation unit4in such a manner as to correspond to the gradation value x0, is output from the timing controller30and is sent to the data driver60(FIG. 5), and is also supplied as a reference address to the RAM3.

The luminance value f(x1) (the luminance value corresponding to the gradation value x1in the gradation-luminance characteristics GLB ofFIG. 7) read on the basis of the reference address x1from the look-up table inside the RAM3is sent to the subtraction circuit5.

The subtraction circuit5subtracts the luminance value f(x1) from the luminance value f(x0), and supplies a subtraction result f(x2)=f(x0)−f(x1) as a reference address to the RAM2. The gradation value x2(the gradation value corresponding to the luminance value f(x2) in the gradation-luminance characteristics GLA ofFIG. 7) read from the look-up table inside the RAM2on the basis of the reference address f(x2) is output from the timing controller30and is sent to the data driver60.

On the basis of the gradation values x1and x2sent from the timing controller30, the data driver60(FIG. 5) drives the subpixels B and A (FIG. 1) among the pixels P of the liquid-crystal panel50, respectively.

In the liquid-crystal display device, if the calculation result of the gradation value x1of the subpixel B by the subpixel drive level calculation unit4in the timing controller30is changed only under the control of the CPU40, since the luminance value f(x1) sent from the RAM3to the subtraction circuit5is changed, the reference address f(x2) supplied from the subtraction circuit5to the RAM2is changed. Therefore, it is possible to change the drive levels of the subpixels A and B with respect to the gradation of the video signal to be input to the timing controller30.

FIG. 15shows a state of changes in the drive levels of the subpixels A and B using the circuit ofFIG. 6by using, as an example, a case in which the drive level of the subpixel B is changed as shown inFIG. 9by the subpixel drive level calculation unit4.

As described above, in the liquid-crystal display device, it is possible to increase the number of selectable drive levels of the subpixels A and B by only increasing variations of the calculation result by the subpixel driving the level calculation unit4while the number of RAMs in which gradation-luminance characteristics of the whole pixels P, the subpixel A, and the subpixel B are stored as look-up tables, is fixed to three, that is, the RAMs1to3.

As a result, in the liquid-crystal display device, it is possible to select (for example, the driving level is selected from among a plurality of drive levels in accordance with whether the pixel is R, G, or B as shown inFIG. 2, or the drive level of the subpixel is selected from among a plurality of drive levels in accordance with the type of the input video signal) the drive level of a subpixel with respect to the gradation of the input video signal from among a plurality of drive levels while an increase in the circuit scale is suppressed.

Furthermore, in a method of providing only a gradation conversion table in which the gradation of an input video signal and output gradations for each subpixel are associated with each other as described in the document (Japanese Unexamined Patent Application Publication No. 2005-316211) given in the Background Art, there are cases in which target gradation-luminance characteristics cannot be realized with high accuracy. However, in the liquid-crystal display device, it is possible to realize target gradation-luminance characteristics with high accuracy by increasing variations of the calculation result by the subpixel drive level calculation unit4inside the timing controller.

Further, in the above examples, as shown inFIG. 6, the RAM1, the RAM2, and the RAM3are provided, and these RAMs are each stored with a look-up table in which gradation values and luminance values are associated with each other so that the target characteristics GL, the gradation-luminance characteristics GLA, and the gradation-luminance characteristics GLB shown inFIG. 7are shown. However, not being limited to such RAMs, appropriate means (for example, a calculation circuit for generating, as a result of one of the gradation value and the luminance value being supplied, the value of the other on the basis of calculation, or the like) for generating information on the correspondence between gradations and luminances for realizing target characteristics GL, gradation-luminance characteristics GLA, and gradation-luminance characteristics GLB may be provided.

Explanation of Reference Numerals