JPH10198307A - Display device and gamma correcting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display device and gamma correcting method by which proper gamma correction can be performed by means of a simple circuit. SOLUTION: A level conversion circuit 22 supplies a shift signal of a digital quantity corresponding to a bright signal to an adding circuit 2C and a subtracting circuit 2E. The adding circuit 2C adds the shift signal to the RGB signal of a digital quantity that has been extracted by a RGB extracting circuit 2A and whose contrast has been adjusted by a contrast treating circuit 2B. A gamma correction data read circuit 2D reads the gamma correction data from the address of the output value of the adding circuit 2C of a ROM 2M. In other words, the address value of the ROM 2M corresponds to the data before gamma correction. In the gamma correction data read by a gamma correction data read circuit 2D, the amount equivalent to the shift signal is subtracted by the subtracting circuit 2E and is output. Then, the RGB signal that has been output from the subtracting circuit 2E and has been subjected to gamma correction is restricted to a prescribed level by a limiter 2F and is output.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device and a gamma correction method, and more particularly to a display device and a gamma correction method in which a pixel is formed by a common electrode and a pixel electrode opposed to the common electrode, and the potential of the common electrode is controlled. The present invention relates to gamma correction in a display device that performs bright correction.

[0002]

2. Description of the Related Art In a TFT liquid crystal display device, brightness adjustment and gamma (.gamma.) Correction are techniques required for compensating the electro-optical characteristic curve and viewing angle dependence of a liquid crystal panel. In the brightness adjustment in the conventional TFT liquid crystal display device, the dynamic range of the signal applied to the TFT is limited to a predetermined value (for example, 5 V) or less, and the adjustment range cannot be satisfied by the amplitude adjustment of the image signal written to the pixel electrode. This is done by controlling the potential of the common electrode in conjunction with the signal.

When the brightness adjustment is performed in this manner, as shown in FIG. 7, the gamma characteristic of the image signal also shifts in accordance with the fluctuation width of the brightness adjustment. It is necessary to move in conjunction with the potential. The circuit for this γ correction requires a reference potential linked to the bright signal.

However, the configuration of the reference potential generating circuit for generating the reference potential is very complicated. In addition, a considerable space is required to mount the reference potential generating circuit. Further, since a line for supplying this potential to the source driver is required, there is a problem that a considerable space is required for mounting this line.

On the other hand, in order to solve the space problem, a method of fixing a reference potential for γ correction independently of a bright signal has been used. However, this method cannot cope with the deviation of the γ characteristic,
There is a problem that correction cannot be performed.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and has an object to provide a display device and a gamma correction method capable of performing appropriate gamma correction with a simple circuit. The purpose is to provide.

[0007]

In order to achieve the above object, a display device according to a first aspect of the present invention is arranged in a matrix with a common electrode, and is arranged facing the common electrode. A plurality of pixel electrodes, and a plurality of active elements respectively connected to the plurality of pixel electrodes, and display means for displaying an image according to a difference in signal level between the common electrode and the pixel electrodes. A brightness adjusting means for controlling a signal to be written to the common electrode based on a bright signal supplied from the outside to adjust brightness of the display means, a digital signal corresponding to an image signal supplied from the outside, and the bright Gamma correction means for performing gamma correction based on a digital signal corresponding to the signal to generate a corrected image signal, and the gamma correction means connected to any one of the matrix lines. A selection drive unit for selecting and turning on the active element, and the corrected image signal generated by the gamma correction unit to the pixel electrode connected to the active element selected and turned on by the selection drive unit. Signal driving means for writing via the active element.

[0008] According to the above display device, gamma correction linked to the brightness adjustment can be obtained by a digital amount.
Therefore, there is no need for a complicated circuit such as a reference potential generating circuit necessary for performing gamma correction with an analog amount. For this reason, it is possible to perform appropriate gamma correction linked to the brightness adjustment with a simple circuit.

In the above display device, the gamma correction means includes: storage means in which gamma correction data for performing gamma correction is written in correspondence with the bright signal and the image signal; Reading means for reading gamma correction data written in the storage means based on the gamma correction data read from the gamma correction data read by the reading means,
May be provided.

In the above display device, the gamma correction means includes: storage means in which gamma correction data for performing gamma correction is written at an address corresponding to the bright signal and the image signal; Adding means for adding a digital signal corresponding to the bright signal to a corresponding digital signal; and reading and reading gamma correction data written at an address corresponding to the value of the digital signal added by the adding means in the storage means Means for subtracting a digital signal corresponding to the bright signal from the gamma correction data read by the reading means to generate a corrected image signal.

Note that the addition and subtraction referred to here include addition and subtraction of 0 and negative numbers as well as positive numbers. That is, in the case of normal brightness adjustment, 0 is added and subtracted. When the brightness is deviated from the normal brightness adjustment, it is determined which of a positive number and a negative number to add or subtract depending on which side the brightness adjustment is performed. Further, the address of the storage means may be an absolute address which completely matches the value of the digital signal added by the adding means, or a relative address obtained by adding or subtracting a predetermined value.

In the above display device, the level of the corrected image signal subjected to the gamma correction may exceed the dynamic range of the active element.
For this reason, the gamma correction unit may further include an output adjustment unit that limits an output level of the generated corrected image signal to a constant level according to the bright signal.

The display device of the present invention is preferably applied to an active matrix type liquid crystal display device such as a TFT liquid crystal display device. In this case, the display means is constituted by a liquid crystal panel in which liquid crystal is sealed between a pair of substrates facing each other, the common electrode is formed on one of the opposing surfaces of the pair of substrates, and the pixel electrode and the active electrode are formed. The element is formed on the other opposing surface of the pair of substrates, and further includes a first polarity inversion unit that inverts the polarity of the corrected image signal corrected by the gamma correction unit at predetermined timings. A second polarity inverting means for inverting the polarity of the signal subjected to the brightness adjustment by the brightness adjusting means at every predetermined timing, wherein the signal driving means comprises a second polarity inverting means at every predetermined timing by the first polarity inversion means. The corrected image signal whose polarity has been inverted is supplied to the common electrode, and the signal whose polarity has been inverted at predetermined timing by the second polarity inverting means is supplied to the common electrode. Written by, it becomes a thing.

In order to achieve the above object, a gamma correction method according to a second aspect of the present invention is directed to a gamma correction method, comprising: a common electrode; and a plurality of gamma correction electrodes arranged in a matrix and opposed to the common electrode. A display panel having a pixel electrode and a plurality of active elements respectively connected to the plurality of pixel electrodes, and displaying an image in accordance with a difference in signal level between the common electrode and the pixel electrode; and A selection driving circuit that selects and turns on the plurality of active elements connected to any one of the lines, and the pixel electrode connected to the active element selected and turned on by the selection driving circuit, from the outside. A signal driving circuit for writing a corrected image signal obtained by gamma-correcting the supplied image signal through the active element, and a signal driving circuit based on a bright signal supplied from the outside. A brightness adjustment circuit for controlling brightness of the display panel by controlling a signal to be written to a common electrode, wherein the gamma correction data for performing gamma correction includes the brightness signal and the brightness signal. A writing step of writing to the storage means in accordance with the image signal; a reading step of reading the gamma correction data written to the storage means in the writing step based on the bright signal and the image signal; Generating the corrected image signal from the gamma correction data read in the reading step.

[0015] The gamma correction method of the present invention may further include an output adjusting step of limiting the level of the corrected image signal generated in the generating step to a constant level in accordance with the bright signal and outputting the same. Good.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

[First Embodiment] FIG. 1 is a block diagram showing a configuration of a TFT liquid crystal display device according to a first embodiment of the present invention. As shown, the TFT liquid crystal display device includes a digital RGB generator 1, a controller 2, a gate driver 3, a digital source driver 4, a D / A converter 5, an inverting amplifier 6, and a TFT liquid crystal panel 7. Is done.

The digital RGB generator 1 synchronizes the horizontal synchronizing signal (H) and the vertical synchronizing signal (V) with the horizontal synchronizing signal (H) and the vertical synchronizing signal (V) from a video signal supplied from the outside. Generate a clock signal (CK). Further, the digital RGB generator 1 synchronizes with the clock signal (CK) to generate three signals of red (R), green (G), and blue (B).
The color signals (RGB signals) of the colors are sampled from the video signal at the same timing. These signals are transmitted to the control unit 2
Sent to The R, G, and B color signals are output from the digital RGB generator 1 in parallel.

The control unit 2 converts the RGB signal, clock signal (CK), horizontal synchronizing signal (H) and vertical synchronizing signal (V) supplied from the digital RGB generating unit 1 A control signal, a source control signal, a Vcom level signal, and an inverted signal (FRP) are generated. These signals are supplied to respective circuit portions of the TFT liquid crystal display device as described later. The configuration of the control unit 2 will be further described later.

The gate driver 3 selectively drives any one of the gate lines of the TFT liquid crystal panel 7 in response to a gate control signal supplied from the control unit 2. In response to the source control signal supplied from the control unit 2, the digital source driver 4 sequentially latches inverted RGB signals, which will be described later, supplied from the control unit 2. The reference potential V _DD supplied to the digital source driver 4
Is constant and does not require a reference potential generation circuit.

The D / A converter 5 performs D / A conversion (digital-to-analog conversion) of the digital amount Vcom level signal to which the brightness adjustment has been given by the control unit 2. The inverting amplifier 6 is configured to output the analog amount of V output from the D / A converter 5 in accordance with the inverted signal (FRP) supplied from the control unit 2.
The polarity of the com level signal is inverted / non-inverted, and the Vcom signal amplified to a predetermined level is output to the common electrode of the TFT liquid crystal panel 7.

As shown in FIG. 2A, a sealing material 73 is provided between a pair of transparent substrates 70 and 71.
The liquid crystal 72 is encapsulated by this. Transparent substrate 7
A backlight (not shown) is arranged on the back side of the device 1. On one transparent substrate 70, a common electrode 7 to which a common potential Vcom output from the inverting amplifier 6 is written.
4 are formed.

On the other transparent substrate 71, pixel electrodes 75 are formed in a matrix. The drain of a TFT 76 is connected to each pixel electrode 75.
The gate of the TFT 76 is connected to the gate line 30, and the source of the TFT 76 is connected to the data line 40. Further, on the transparent substrate 70, color filters (not shown) corresponding to the respective colors of RGB are arranged.

The image data for one line latched by the digital source driver 4 is written to the pixel electrode 75 on the line selected by the gate driver 3. That is, in the TFT liquid crystal panel 7, the liquid crystal 72 is controlled by controlling the voltage held in the capacitance 7C composed of the common electrode 74 and the pixel electrode 75 shown in FIG.
To control the amount of transmitted light.

In the TFT liquid crystal panel 7, the common electrode 7
4, an alignment film 77 is formed on the pixel electrode 75 and the TFT 76.
An alignment film 78 is formed thereon. Also,
A spacer 79 is inserted into the liquid crystal 72 between the transparent substrates 70 and 71 to keep the distance between the transparent substrates 70 and 71 constant. The TFT liquid crystal panel 7 has a transparent substrate 7
A polarizing plate may be provided outside one or both of 0 and 71.

Next, the configuration of the control unit 2 will be described in detail. The control unit 2 includes a controller 2 as shown in FIG.
1. Level conversion circuit 22, RGB extraction circuit 2A, contrast processing circuit 2B, addition circuit 2C, γ correction data reading circuit 2D, subtraction circuit 2E, limiter 2F, inversion circuit 2.
G, timing processing circuit 2H, and ROM (Read Only)
Memory) 2M.

The controller 21 generates an internal clock signal based on the horizontal synchronizing signal (H) and the vertical synchronizing signal (V) supplied from the digital RGB generator 1 and the clock signal (CK). The operation of each unit of the control unit 2 is as follows.
This is performed in synchronization with the internal clock signal.

The controller 21 also includes a digital RG
Based on the horizontal synchronizing signal (H) and the vertical synchronizing signal (V) supplied from the B generator 1 and the clock signal (CK), an inversion signal (FRP) that is switched between inversion and non-inversion for each frame is generated. I do. This inverted signal (FRP)
Is supplied to the inverting circuit 2G and the inverting amplifier 6.

The controller 21 further includes a digital R
A gate control signal and a source control signal are generated based on the horizontal synchronizing signal (H) and the vertical synchronizing signal (V) and the clock signal (CK) supplied from the GB generator 1. The gate control signal is supplied to the gate driver 3. On the other hand, the source control signal is supplied to the digital source driver 4.

The level conversion circuit 22 generates a shift signal to be supplied to the addition circuit 2C and the subtraction circuit 2E based on an externally supplied bright signal. In addition, a limiter level signal to be supplied to the limiter 2F is generated. The shift signal generated here is set to a value of 0 during normal brightness adjustment, and is set to a predetermined positive or negative value depending on which side and how much brightness is adjusted. As the limiter level signal, a predetermined value for controlling the output signal of the limiter 2F so as not to exceed the potential of the pixel electrode 74 and to be included in the dynamic range of a signal that can be applied to the TFT is selected. Further, the level conversion circuit 22
A Vcom level signal that has been subjected to brightness adjustment is generated based on a brightness signal supplied from the outside. This Vcom level signal is input to the D / A converter 5.

The RGB extraction circuit 2A latches the RGB signals supplied in parallel from the digital RGB generator 1,
The R, G, and B color signals are output in series in a predetermined order. The contrast processing circuit 2B adjusts the contrast of each of the R, G, and B color signals based on a contrast signal set by a contrast adjustment switch (not shown) or the like.

The addition circuit 2C is a contrast processing circuit 2
The shift signal supplied from the level conversion circuit 22 is added to each of the R, G, and B color signals whose contrast has been adjusted by B. The γ correction data reading circuit 2D reads γ (gamma) correction data stored at the address of the ROM 2M indicated by the output signal of the addition circuit 2C,
Output to the subtraction circuit 2E.

The subtraction circuit 2E includes a γ correction data reading circuit 2
D from the gamma correction data supplied from D
2 is subtracted from the supplied shift signal. Limiter 2F
, Based on the limiter level signal supplied from the level conversion circuit 22, suppresses the maximum level of the signal input from the subtraction circuit 2E to a predetermined value or less and outputs the signal. This is a TFT
This is because the dynamic range of the signal applied to the pixel 76 cannot exceed a predetermined value (for example, 5 V) and the level of the signal written to the pixel electrode 75 must not exceed the level of the Vcom signal.

The inversion circuit 2G inverts / non-inverts the output signal of the limiter 2F in response to the inversion signal (FRP) output from the controller 21 in order to invert the polarity of the signal written to the pixel electrode 75 for each frame. Invert and output. The timing processing circuit 2H delays each of the R, G, and B color signals output from the inversion circuit 2G by a predetermined timing in order to match the timing with the gate control signal and the source control signal, and
Output as a signal.

The ROM 2M includes a gamma correction data read circuit 2D
Γ correction data for γ correction is written in advance. The γ correction data written in the ROM 2M will be described with reference to FIG. The input dynamic range of the RGB signal (the relative amount with respect to the brightness adjustment value) during the normal brightness adjustment is shown in FIG.
In the range of the graph. The γ correction data in this case is in the range of '.

In accordance with the level of the RGB signal (the relative amount with respect to the brightness adjustment value), as shown in FIG.
OM2M address 0000 ... 0-0011 ...
1 is assigned. Then, γ correction data ′ corresponding to the level of the RGB signal is written to each address.

On the other hand, when the level conversion circuit 22 performs a predetermined brightness adjustment, the range of the RGB signal is shifted higher or lower than the range of the graph of FIG. Sometimes. Γ in this case
The correction data is in the range of 'and' respectively.

As shown in FIG. 4B, an address 010 is stored in the ROM 2M in correspondence with the upper RGB signal.
.. 0 to 0111... 1 are assigned, and γ correction data ′ is written in each address. Also,
Addresses 1100,... Corresponding to the lower-side RGB signals
1 to 0111... 1 are assigned, and γ correction data ′ is written in each address.

Hereinafter, the operation of the TFT liquid crystal display device of this embodiment will be described. This display includes:
A digital video signal and a digital bright signal are supplied from outside. The video signal is supplied to the digital RGB generator 1 and the bright signal is supplied to the level converter 22 of the controller 2.

The digital RGB generator 1 generates a clock signal (CK), a horizontal synchronizing signal (H),
A vertical synchronizing signal (V) and an RGB signal are generated. The generated clock signal (CK), horizontal synchronization signal (H), and vertical synchronization signal (V) are supplied to the controller 21. The RGB signals are supplied to the RGB extraction circuit 2A.

In the controller 21, the digital R
Based on the clock signal (CK), horizontal synchronization signal (H), and vertical synchronization signal (V) supplied from the GB generator 1,
An internal clock signal is generated. This internal clock signal is supplied to each section of the circuit of the control section 2 to operate each section of the circuit.

In the controller 21, the clock signal (C) supplied from the digital RGB
K), an inverted signal (FRP), a gate control signal, and a source control signal are generated based on the horizontal synchronization signal (H) and the vertical synchronization signal (V). The inversion signal (FRP) is supplied to the inversion circuit 2G and the inversion amplifier 6. The gate control signal is supplied to the gate driver 3. The source control signal is supplied to the digital source driver 4.

From the bright signal supplied to the level conversion circuit 22, a Vcom level signal, a shift signal, and a limiter level signal are generated. The Vcom level signal is a signal for controlling the potential of the common electrode 74 to perform brightness adjustment, and is supplied to the D / A converter 5. The shift signal is supplied to an addition circuit 2C and a subtraction circuit 2E, and the limiter level signal is supplied to a limiter 2F.

The R, G, and B color signals supplied in parallel to the RGB extraction circuit 2A are supplied from the RGB extraction circuit 2A to the contrast processing circuit 2B in a predetermined order in series. The contrast processing circuit 2B adjusts the contrast of the RGB signals based on the contrast signal supplied from the outside. The image signal whose contrast has been adjusted by the contrast processing circuit 2B is supplied to the addition circuit 2C.

Then, the addition circuit 2C outputs a signal from the limiter 2
Up to F, γ correction processing is performed. Hereinafter, FIG. 5 (A)
And the address map of FIG. 5B.

From the contrast processing circuit 2B to the adding circuit 2
The dynamic range of the image signal supplied to C is shown in FIG.
The image signal takes one of the values W in this range. This image signal W is stored at the address 00000000 of the ROM 2M in the range shown in FIG.
To 00111111.

Next, in the adder circuit 2C, as shown in FIGS. 5A and 5B, a shift signal a corresponding to the bright signal supplied from the level conversion circuit 22 is added to the image signal W. I do. Then, as shown in FIGS. 5A and 5B, the γ correction data read circuit 2D includes a ROM
The γ correction data X is read from the address of the added value W + a of 2M.

Here, when the value W + a obtained by adding the image signal W and the shift signal a is higher than the input dynamic range at the time of normal bright correction, the data X is read from the address range of 010000000 to 01111111 of the ROM 2M. If it is below (at this time, the shift signal a
Is a negative number).
The γ correction data X is read from the range of 111111111.

The gamma correction data X read by the gamma correction data reading circuit 2D is actually added with the shift signal a for the brightness adjustment. Therefore, FIG.
As shown in (A) and (B), the subtraction circuit 2E
The shift signal a is subtracted from the γ correction data X, and the subtracted value Y is output as a corrected image signal.

The value of the shift signal a is set to 0 during normal brightness adjustment, and is set to a predetermined positive or negative value depending on whether the brightness adjustment is performed on the white side or the black side.

As described above, the corrected image signal Y subjected to the γ correction is generated in conjunction with the bright signal, but this value may exceed the dynamic range of the signal that can be applied to the TFT 76. . Therefore, as shown in FIGS. 5A and 5B, the corrected image signal Y is supplied to the limiter 2.
F, the corrected image signal Z limited to a predetermined level or less.
Get.

This corrected image signal Z is supplied to the inverting circuit 2G. The inversion circuit 2G inverts / non-inverts the corrected image signal Z based on the inversion signal (FRP) to give a polarity to the signal. Then, the corrected image signal given this polarity is supplied to the digital source driver 4 sequentially as an inverted RGB signal after performing predetermined timing adjustment in the timing processing circuit 2H.

In the digital source driver 4, according to the source control signal supplied from the controller 21, the inverted RGB output from the timing processing circuit 2H is output.
The signals are sequentially latched. Then, the signal which is latched to the pixel electrode 75 connected to the gate line 30 selected by the gate driver 3 is transferred to the TFT 76 by the source control signal (write signal) output when the signal for one line is latched. Write through.

The Vcom level signal output from the level conversion circuit 22 is converted by the D / A converter 5 into an analog signal, and the inversion amplifier 6 applies the polarity according to the inversion signal (FRP). , To a predetermined level. The Vcom signal output from the inverting amplifier 6 is subjected to bright adjustment by the potential and written to the common electrode 74 of the TFT liquid crystal panel 7. Thus, gamma correction linked to the brightness adjustment is realized.

As described above, T of this embodiment is different from that of FIG.
In the FT liquid crystal display device, a value corresponding to the brightness adjustment is added to a digital amount of RGB signal by an addition circuit 2C, and a ROM
The γ correction data is read from the address of the value obtained by adding 2M. Then, the value added by the addition circuit 2C is subtracted from the read gamma correction data by the subtraction circuit 2E.
Therefore, in the TFT liquid crystal display device of this embodiment,
Gamma correction linked to the brightness adjustment can be realized with a very simple circuit.

As a result, the TFT liquid crystal display device of this embodiment does not require a complicated reference potential generation circuit. Further, a line for supplying the reference potential to the source driver is not required. Therefore, the size of the source driver and the display panel can be reduced. In addition, the manufacturing / adjustment process can be simplified. As a result, the cost of the entire apparatus can be reduced.

[Second Embodiment] In the first embodiment, the case where the present invention is applied to a TFT liquid crystal display device using a digital RGB input source driver has been described. However, the present invention can also be applied to a TFT liquid crystal display device using a low-voltage analog source driver of analog RGB input.

FIG. 6 is a block diagram showing a configuration of a TFT liquid crystal display device according to the second embodiment of the present invention.
In this figure, the same components as those of the TFT liquid crystal display device of FIG. 1 are denoted by the same reference numerals.

The TFT liquid crystal display device includes an A / D converter 81 for A / D converting (analog-digital conversion) an analog RGB signal, and an A / D converter 81 for converting an analog bright signal to an analog signal.
An A / D converter 82 for performing D / A conversion and a D / A converter for performing D / A conversion on a digital amount of an inverted RGB signal supplied from the control unit 2.
A converter 83 is provided. Further, an analog source driver 84 is provided instead of the digital source driver 4 according to the first embodiment, and an inverting amplifier 85 is provided instead of the inverting amplifier 6 according to the first embodiment.

Hereinafter, the operation of the TFT liquid crystal display device of this embodiment will be described. The analog RGB signal and the bright signal of the analog amount supplied from outside are
The signals are converted into digital quantities by A / D converters 81 and 82, respectively. The RGB signal and the bright signal that have been converted into digital quantities are input to the control unit 2.

The operation of the control unit 2 is the same as that of the first embodiment except that the Vcom level signal is not output from the level conversion circuit 22. That is, the control unit 2
A predetermined process such as γ correction or polarity inversion is applied to the RGB signals, and each control signal is generated and output.

The gate control signal output from the control unit 2 is supplied to the gate driver 3, and the gate driver 3 selectively drives any one of the gate lines as in the first embodiment. Further, the source control signal is supplied to the analog source driver 84.

The inverted RGB signal output from the control unit 2 is converted into an analog amount by the D / A converter 83,
It is supplied to the analog source driver 84 as an inverted analog RGB signal. The analog source driver 84 sequentially latches the inverted analog RGB signals according to the source control signal. When the inversion analog signal for one line is latched by the analog source driver 84, each signal is written to the pixel electrode 75 of the line selected by the gate driver 3.

On the other hand, the bright signal supplied to the inverting amplifier 85 is the inverted signal (FRP) output from the control unit 2.
, The polarity is inverted for each frame and written to the common electrode 74 of the TFT liquid crystal panel 7. As described above, also in the TFT liquid crystal display device of the present embodiment, it is possible to display an image on which the γ correction has been performed in conjunction with the bright correction, similarly to the TFT liquid crystal display device of the first embodiment.

[Modification of Embodiment] In the above embodiment, addresses 0000...
... Write data for normal brightness correction to 1
Addresses 0100... To 0111.
1100... 0 to 1111. However, the present invention is not limited to this. For example, the RGB signal (the relative value between the RGB signal and the bright signal) obtained by adding the shift signal is used as the RO signal.
The gamma correction data may be written so as to be the address of M2M. The gamma correction data may be written at an address (relative address) obtained by adding a predetermined value (including a negative number) to this relative value.

In the above embodiment, the adder circuit 2C
The data amount for the brightness adjustment is added to the RGB image signal, and the γ-correction data reading circuit 2D reads the γ-correction data written in the ROM 2M by a table lookup method. Then, the subtraction circuit 2E subtracts the data amount for the brightness adjustment from the read γ correction data. However, the present invention is not limited to this. For example, instead of the above method, based on a predetermined processing program, R
A method using a processor that calculates γ correction data according to the data amount of the GB image signal and the brightness adjustment may be adopted.

In the above embodiment, the digital amount of RG
The gamma correction for the B signal has been performed by hardware. However, all or a part of the gamma correction processing of the present invention may be performed by a general-purpose processor and software for operating the processor.

In the above-described embodiment, a TFT liquid crystal display device that performs full color display using three color signals of R, G, and B has been described. However, the present invention is also applicable to a TFT liquid crystal display device that displays a monochrome image. Further, the present invention can be applied to a display device such as a multi-panel liquid crystal projector that displays a full-color image by combining monochrome images of a plurality of colors.

In the above embodiment, the case where the present invention is applied to a TFT liquid crystal display device has been described. However, the present invention is not limited to this. For example, the present invention can be applied to other active matrix type liquid crystal display devices using active elements such as diodes and MIM (Metal Insulator Metal).

Further, the present invention can be applied to all display devices that perform bright correction by controlling the potential of a common electrode, such as an organic EL display device. Since the organic EL element has no polarity, when the present invention is applied to an organic EL display device, an inverting amplifier and an inverting circuit in a control unit are not required. Further, when performing full-color display with an organic EL display device, since the electro-optical characteristics of the organic EL element are different for each color, the RO in which the γ correction data is written is used.
M may be prepared for each color.

[0071]

As described above, according to the present invention,
Appropriate gamma correction can be performed with a simple circuit.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a TFT liquid crystal display device according to a first embodiment of the present invention.

2A and 2B are diagrams showing a configuration of the TFT liquid crystal panel of FIG. 1, wherein FIG. 2A is a cross-sectional view and FIG. 2B is a schematic diagram.

FIG. 3 is a block diagram illustrating a configuration of a control unit in the TFT liquid crystal display device of FIG.

4A and 4B are diagrams illustrating an example of gamma correction data written in the ROM of FIG. 2, wherein FIG. 4A is a graph and FIG. 4B is an address map.

FIG. 5 is an explanatory diagram of a gamma correction method according to the first embodiment of the present invention.

FIG. 6 is a block diagram illustrating a configuration of a TFT liquid crystal display device according to a second embodiment of the present invention.

FIG. 7 is a diagram showing the relationship between brightness adjustment and fluctuation of gamma potential in a conventional TFT liquid crystal display device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Digital RGB generation part, 2 ... Control part, 3 ... Gate driver, 4 ... Digital source driver, 5 ... D /
A converter, 6: inverting amplifier, 7: TFT liquid crystal panel,
21: controller, 22: level conversion circuit, 2A
-RGB extraction circuit, 2B ... contrast processing circuit, 2C
... Addition circuit, 2D ... γ-correction data reading circuit, 2E ...
Subtraction circuit, 2F ... limiter, 2G ... inversion circuit, 2H
・ Timing processing circuit, 2M ・ ・ ・ ROM (Read Only Memo)
ry), 70, 71 ... transparent substrate, 72 ... liquid crystal, 74 ...
Common electrode, 75: Pixel electrode, 76: Thin film transistor (TFT), 30: Gate line, 40: Source line, 81, 82: A / D converter, 83: D / A converter, 84: Analog source driver, 85: Inverting amplifier

Claims (7)

[Claims] 1. A semiconductor device comprising: a common electrode; a plurality of pixel electrodes arranged in a matrix and opposed to the common electrode; and a plurality of active elements respectively connected to the plurality of pixel electrodes. A display unit that displays an image in accordance with a difference in signal level between the common electrode and the pixel electrode; and a signal that is written to the common electrode based on a bright signal supplied from the outside, thereby controlling the display. Brightness adjustment means for performing brightness adjustment of the means, and gamma correction means for performing gamma correction based on a digital signal corresponding to an externally supplied image signal and a digital signal corresponding to the brightness signal to generate a corrected image signal Selecting drive means for selecting and turning on the plurality of active elements connected to any one of the lines of the matrix; Signal driving means for writing, via the active element, the corrected image signal generated by the gamma correction means to the pixel electrode connected to the active element that has been selected and turned on. Display device. 2. The gamma correction unit includes: a storage unit in which gamma correction data for performing gamma correction is written in correspondence with the bright signal and the image signal; and a gamma correction data based on the bright signal and the image signal. 2. A reading means for reading gamma correction data written in the storage means, and means for generating the corrected image signal from the gamma correction data read by the reading means. Display device. 3. The gamma correction unit includes: a storage unit in which gamma correction data for performing gamma correction is written at an address corresponding to the bright signal and the image signal; and a digital signal corresponding to the image signal. Adding means for adding a digital signal corresponding to the bright signal; reading means for reading gamma correction data written at an address corresponding to the value of the digital signal added by the adding means in the storage means; The display device according to claim 1, further comprising: subtraction means for subtracting a digital signal corresponding to the bright signal from the gamma correction data read by the means to generate a corrected image signal. 4. The apparatus according to claim 1, wherein said gamma correction means further comprises an output adjustment means for limiting an output level of the generated corrected image signal to a constant level according to the bright signal. 4. The display device according to any one of 3. 5. The display means comprises a liquid crystal panel in which liquid crystal is sealed between a pair of substrates facing each other, the common electrode is formed on one of the opposite surfaces of the pair of substrates, The active element is formed on the other facing surface of the pair of substrates, and further includes a first polarity inversion for inverting the polarity of the corrected image signal corrected by the gamma correction unit at predetermined timings. Means, and second polarity inverting means for inverting the polarity of the signal subjected to the brightness adjustment by the brightness adjusting means at predetermined time intervals, wherein the signal driving means has a predetermined timing by the first polarity inversion means. The corrected image signal whose polarity has been inverted every time is supplied to the common electrode. Signal is written, a display device according to any one of claims 1 to 4, characterized in that. 6. A semiconductor device comprising: a common electrode; a plurality of pixel electrodes arranged in a matrix and opposed to the common electrode; and a plurality of active elements respectively connected to the plurality of pixel electrodes. A display panel for displaying an image in accordance with a difference in signal level between the common electrode and the pixel electrode; and a selection for selecting and turning on the plurality of active elements connected to any one of the lines of the matrix. A driving circuit, and a signal for writing, via the active element, a corrected image signal obtained by gamma-correcting an externally supplied image signal to the pixel electrode connected to the active element selected and turned on by the selection driving circuit. A drive circuit for controlling a signal to be written to the common electrode based on a bright signal supplied from the outside to perform a brightness adjustment of the display panel; A gamma correction method for a display device, comprising: a writing adjustment circuit for writing gamma correction data for performing gamma correction to storage means in accordance with the bright signal and the image signal; Reading the gamma correction data written in the storage means in the reading step based on the bright signal and the image signal; and generating the corrected image signal from the gamma correction data read in the reading step A gamma correction method, comprising: 7. The method according to claim 6, further comprising an output adjusting step of limiting the level of the corrected image signal generated in the generating step to a predetermined level according to the bright signal and outputting the limited level. The gamma correction method described.