JPH06230760A - Display device - Google Patents

Abstract

PURPOSE:To automatically switch a (gamma) curve for the content of an input signal and to suppress the change of a color tone simultaneously. CONSTITUTION:A control means 30a changes a table for (gamma) correction for a (gamma) correction circuit 20a according to the gradation histogram of a video signal. A (gamma) correction result is displayed by outputting from the (gamma) correction circuit 20a to a matrix display device 40 according to a changed table for (gamma) correction. Also, such constitution that another two colors are used in the tables for (gamma) correction for R, G, and B mutually is employed. The table for (gamma) correction in which the change of hue can be suppressed is used, and the change of hue is suppressed by picture-extending gradation with a high use frequency on a histogram and also, limiting overcorrection, thereby, (gamma) correction with high contrast and low gradation-collapse can be performed.

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 more particularly to a technique for changing a γ correction curve according to a video signal or an external environment to perform optimum γ correction in accordance with a video signal.

[0002]

2. Description of the Related Art Generally, γ correction is performed on the photographing side,
This is a video signal CR with the display characteristics of the CRT in mind.
This is to match the display characteristics of T. Therefore, CR
In a display element having a display characteristic different from T, for example, a matrix liquid crystal display element or the like, further γ correction is necessary before display in order to match the video signal with the characteristic of the display element.

In a matrix display device such as a liquid crystal whose dynamic range is narrower than that of a CRT, a method of changing the γ correction curve in an analog manner in accordance with a video signal is provided in order to display with a good contrast.
It is described in Japanese Patent Publication No. 920.

As a method for performing γ correction with a digital signal, a method for performing γ correction on R, G, B primary color signals using a γ correction table is disclosed in, for example, Japanese Patent Laid-Open No. 1-167.
There is a method described in Japanese Patent No. 794.

[0005]

In the first prior art in which the γ correction characteristic is changed in an analog manner, the γ correction characteristic cannot be made with high accuracy because the one-point broken line approximation or the like is used.

Further, in the second prior art in which the R, G, and B primary color signals are digitally .gamma.-corrected, there is a problem that the hue changes when the .gamma.-curve is made non-linear.

Further, when a personal computer or the like is displayed on a display device having a limited dynamic range, for example, when a signal from a personal computer capable of outputting 512 colors is displayed on a display device capable of displaying 512 colors, gamma correction is performed. There is a problem in that the gradation that is not used is generated in the part where the expansion is performed by applying, and the number of gradations that can be displayed is reduced.

[0008]

In order to solve the above first problem, a digital γ correction having a γ correction table capable of changing the γ correction characteristics according to the contents of a video signal and the environment where the display device is placed. A circuit was used.

In order to solve the second problem described above, the R, G, and B γ correction circuits for γ correction also use the information of the other two colors, and the γ correction does not change the hue of the signal. The correction table created in this manner is used.

Further, the configuration is such that the signal from the input video signal source switching device is also input to the control means, and the γ correction circuit is controlled depending on the difference of the input signal source.

[0011]

The digital γ correction table is used to realize highly accurate γ correction, while the control means detects the contents of the video signal and changes the γ correction table based on the detected signal We have realized the optimum γ correction according to the signal content.

Further, when the control means controls the γ correction circuit, the output gradation is expanded by allocating a large number of output gradations to a portion having a high frequency among the input gradations, and another gradation portion is expanded. By not crushing too much, the contrast of the screen was increased and at the same time the gradation was suppressed.

Further, the R, G, and B γ correction circuits also use information of the other two colors, and a correction table created so that the hue of the signal does not change even when γ correction is performed, γ
The change in hue due to the correction was suppressed.

Furthermore, the γ correction curve can be changed depending on the difference of the input signal source, and the optimum γ correction can be performed regardless of the input signal source.

[0015]

1 is a diagram showing the configuration of a first embodiment of the present invention. In the figure, reference numeral 20a is a gamma correction circuit for performing gamma correction. Reference numeral 10 is a video signal input unit, and 30a is a control means for controlling the gamma correction circuit 20a. Reference numeral 40 is a display element, for example, a matrix liquid crystal display element.

The three primary color input video signals R, G and B from the video input section 10 are given to the γ correction circuit 20a and the control means 30a. In the γ correction circuit 20a, the γ-corrected video signal is applied to the display element 40 according to the γ-correction table designated by the control means 30a to display the image.

The structure and operation of the γ correction circuit 20a will be described below by taking as an example the portion of the three primary color video signals R, G, B which performs γ correction. The ROM 22 stores a plurality of γ correction tables created by the method described later, selects one of the plurality of γ correction tables based on a control signal from the control means 30a, and the RAM 21
transfer to a. In order to select and transfer one from a plurality of γ correction tables, the CPU 31a gives an address signal of the ROM 22 and the RAM 21a as the control signal, and R
The data read from the OM 22 may be written in the RAM 21a. Further, since the data is transferred from the ROM 22 to the RAM 21a to rewrite the γ correction table, the data of the γ correction table within the rewriting time is not guaranteed.
To prevent this effect from appearing on the screen, it is necessary to perform data transfer within the blanking period.

By performing the above operation also on the RAMs 21b and 21c, the correction tables on the RAMs 21a, 21b and 21c are changed. As a result, the RAM 21a,
21b and 21c output a video signal obtained by gamma-correcting the input video signal based on the gamma correction table transferred from the ROM 22.

The γ correction characteristics on the RAMs 21a, 21b and 21c are formed by the following method, for example. When the coordinates of the input signal in the R, G, B coordinate system are (r, g, b), the coordinates are converted into Y, U, V coordinates, and (y, u, v)
Get the coordinates. The coordinate conversion is performed by the following formula, for example.

[0020]

[Equation 1] u = (2.43r + 0.694g + 0.8b) / (5.09r + 9.1)
7g + 5.26b)

[0021]

[Equation 2] v = (2.69r + 5.28g + 1.03b) / (5.09r + 9.1
7g + 5.26b)

[0022]

## EQU00003 ## y = 0.299r + 0.587g + 0.114b A gamma correction curve y '= f (y) to obtain a gamma correction table for this luminance component y is used to perform gamma correction (y', u, v).
To the coordinates. The coordinates (r ', g', b ') obtained by inversely converting the coordinates R, G, B coordinates and the input signal (r, g,
Determine the γ correction table from b). The inverse conversion formula is expressed as follows, for example.

[0023]

[Equation 4] r = (54.2u + 10.9v-10.4) y / 12v

[0024]

[Equation 5] g = (-26.3u + 25.7v-1.02) y / 12v

[0025]

## EQU6 ## b = (-6.51u-55.3v + 32.3) y / 12v ROM22 as the γ correction table created in this way
It is possible to suppress the color change due to the non-linear γ correction.

At this time, when all the input and output of each digital video signal are 8 bits, the capacity of the RAM 21a required for the γ correction table is 8 bits for address × 3 = 24.
Since it is a bit and the output data is 8 bits, it becomes 16 Mbytes. When the RAMs 21a, 21b, and 21c for three colors are summed up, 48 Mbytes, which is three times that amount, are required.

Considering that the output video signal r'has a large correlation with the input video signal r and has a small correlation with the input video signals g, b, while R of 8 bits is input to the R RAM 21a, For example, the error of the γ correction circuit is at an allowable level even if the number of 4-bit inputs on the MSB side of G and B is reduced. The same applies to the RAMs 21b and 21c. According to this method, the capacity of the RAM 21a is the address 8 + 4 + 4.
= 16 bits and output 8 bits, it is 64 kbytes, which is a significant reduction compared to the above method. RAM2 for 3 colors
Total of 1a, 21b and 21c is 256 kbyte
Then, it can be suppressed to 1/256 of the case where all bits are input.

Next, an example of the internal structure and operation of the control means 30a shown in FIG. 1 will be described. The control means 30a changes the contents of the input video signal, in particular, the contents of the γ correction in the γ correction circuit 20a according to the gradation distribution characteristic.
It is composed of a central processing unit (hereinafter abbreviated as CPU) 31a, a gradation distribution characteristic forming circuit 32, a RAM 33, and a ROM 34.

The ROM 34 holds programs used by the CPU 31a. The gradation distribution characteristic forming circuit includes a RAM 321, a latch 322, 324, an up counter 323, and a timing generating circuit 325.
According to the signal from 31a, the gradation distribution characteristic of the input video signal in one field is formed within a certain period.

The timing generation circuit 325 is the CPU 31a.
A signal for erasing the memory contents inside the RAM 321 is generated in accordance with the signal from. After that, the data of the address corresponding to the input video signal is output from the RAM 321 to the latch 322 and fetched. The up counter 323 adds 1 to the data in the latch 322, outputs the result to the latch 324, and returns the data from the latch 324 to the RAM 321 as data. The RAM 321 replaces the data at the address with the data. As a result, the data of the address corresponding to the input signal is added one by one according to the signal from the CPU 31a, and as a result, the gradation distribution characteristic is formed on the gradation distribution characteristic forming circuit 32.

Further, the CPU 31a is most suitable from the γ correction table prepared in advance in the ROM 22 in the γ correction circuit 20a based on the gradation distribution characteristic formed on the gradation distribution characteristic forming circuit 32. The signal that selects the one that is present is output. Alternatively, after a new γ correction curve is formed on the RAM 33 according to the following method for changing the γ correction curve, a γ correction table is created on the RAM 33, and the data is stored in the RAMs 21a, 21 without passing through the ROM 22.
A method of directly transferring to b and 21c is also conceivable.

An example of how to obtain the optimum γ correction characteristic will be described below with reference to FIG. First, a reference γ correction curve is obtained from the gradation and luminance characteristics of the CRT which is the reference on the signal source side and the gradation and luminance characteristics of the display element, and the gradation and luminance characteristics of the display device subjected to the gamma correction are the gradation of the CRT. Follow the brightness characteristics. The broken line portion in FIG. 2 is a graph showing an example of the reference γ correction curve, where black is 0 and white is 1, the horizontal axis represents the input gradation, and the vertical axis represents the output gradation. In this example,
The gain from the 0th to the ⅕th gradation of the input gradation is 2.4, and similarly, the gains of the respective sections are 0.8, 0.
It becomes 75,0.4,0.65. The solid line portion in the figure is an example of the gradation distribution characteristics of the input gradation, the horizontal axis represents the input gradation, and the vertical axis represents the frequency.

When the gradation distribution characteristic of the input gradation is as shown by the solid line portion in FIG. 2, the γ curve is changed in accordance with the frequency on the gradation distribution characteristic in order to suppress the collapse. Specifically, if the average frequency of each gradation division is e, the frequency in a certain gradation division is h, and the gain in the gradation division is a, the changed gain a ′ is

[0034]

## EQU00007 ## Let a '= a.h / e. In the case of the example of FIG. 2, the average frequency of each gradation division is 10
Since 0/5 = 20%, when the frequency from the input gradation 0 to the 1/5 gradation is 10%, the gain of the γ correction curve in FIG. 2 is reduced to 10/20 = 0.5 times, .2. Similarly, from the 1 / 5th to the 2 / 5th gradation, the gain is tripled to 2.4, and the gain is set to 0, 2, in the same manner as below.
It is set to 0.325.

Here, in order to prevent the screen from becoming too bright or too dark as a whole by excessively changing the gain, for example, the gain change amount is limited as follows. Turn on. The limit range of the gain is 1.2 to 5 times in the section where the input gradation is 0 to 1/5, and similarly, 0.4 to 1.5 times in the section from 1/5 to 2/5. The limiting range is 0.4 to 1.5 times, 0.2 to 0.8 times, and 0.3 to 1.3 times. By making this restriction, 1/5 to 2/5
The gains of the gray scale and the 3/5 gray scale to the 4/5 gray scale are suppressed to 1.6 and 0.8, respectively, and conversely 2/5 to 3/5.
The gain of the gradation is increased to 0.4. As a result, the γ correction curve becomes like the broken line portion in FIG. This is normalized so that the whole becomes 1, and a new γ curve as shown by the solid line portion in FIG. 3 is formed.

Furthermore, when a large area is painted with the same color, for example, when white characters are displayed on a blue background in news or the like, the above method alone can expand the frequently used gradation. There is a possibility that the gradation unevenness due to noise or the like in the portion that should be originally displayed with the same gradation is enlarged, and the screen becomes dirty. Therefore, in order to prevent the above-mentioned problem, when the frequency within a certain narrow range, for example, the total input gradation number is 64 gradations, for example, 3 gradation sections exceeds 20%, the gain change amount of the gradation is By narrowing the limited range to 1/2 or less of the conventional range, it is possible to suppress an increase in gradation unevenness.

As described above, according to the present embodiment, it is possible to perform the display in which the gradation collapse is suppressed by switching according to the contents of the input video signal. Further, according to this embodiment, it is possible to suppress the change in hue even if the γ curve is changed.

FIG. 4 is a diagram showing a second embodiment of the present invention. 20b is a γ correction circuit, and 30b is a control means.
The major difference between this embodiment and the first embodiment is the γ correction circuit 20.
The point is that the γ correction table of b is composed of ROM instead of RAM.

The operation of the γ correction circuit 20b will be described below.
A description will be given by taking as an example a portion in which R γ correction is performed. ROM2
4a stores a plurality of γ correction tables in advance,
One of the plurality of γ correction tables is selected based on a control signal from the control means. In order to select one from a plurality of γ correction tables, the control signals are video signals R, G, B.
It may be given to the address of the ROM 24a together with.

The above operation is also performed on the ROMs 24b and 24c, and the correction tables on the RAMs 24a, 24b and 24c are changed. As a result, the ROMs 24a, 24
b and 24c output the video signal obtained by gamma-correcting the input video signal based on the gamma correction table selected by the control means.

The configuration and operation of the other parts are the same as those in the first embodiment, and the description thereof will be omitted.

In this embodiment, since a portion for storing a plurality of γ correction tables and a portion for actually performing γ correction are the same, it is necessary to use a high-speed and large-capacity ROM.
Since it is not necessary to transfer the data to the correction table, the time required for switching the γ correction table is unnecessary. This has the advantage that the γ correction table can be easily switched depending on the display location on the screen. However, in this case, it is necessary to divide the display screen into several blocks and obtain the gradation distribution characteristics for each.

As described above, according to the present embodiment, it is possible to construct the display device having the γ correction circuit capable of switching the γ correction operation at high speed according to the contents of the video signal.

FIG. 5 is a diagram showing a third embodiment of the present invention. Reference numeral 20c is a γ correction circuit, and 30c is a control means.
This embodiment is greatly different from the first embodiment in that the γ correction circuit 20c has two systems of RAM for each primary color signal as a γ correction table, and the γ correction data transfer from the control means 30c and the image are performed. The point is that the γ correction operation for signals can be performed in parallel.

The structure and operation of the γ correction circuit 20c shown in FIG. 5 will be described below by taking the portion 25R for R γ correction as an example. 251a and 252b are RAMs, and 26 is a changeover switch. Reference numerals 251a and 252a denote RAMs that perform γ correction according to a γ correction table that is predetermined by an external control unit. Reference numeral 26 is a switch for inputting the video signal from the video input unit 10 to one of the RAMs 251a and 252a according to the signal from the control means 30c, and for inputting the γ correction data and the write control signal from the control means to the other.

Now, the video signal is input to the RAM 251a based on the switching instruction signal from the control means 30c, and RA
It is assumed that a signal such as γ correction data from the control unit 30c can be input to the M252a. A signal from the control means 30c puts the output circuit of the RAM 252a into a high impedance state, and only the output of the RAM 251a is output as the output of the γ correction circuit 20c. The new γ correction data is written in the RAM 252a through the switch 26. After the writing is completed, the switching instruction signal from the control means 30c is inverted, and signals such as γ correction data from the control means 30c can be input to the RAM 251a, and at the same time, its output terminal becomes high impedance. At this time, the video signal is input to the RAM 252a, γ-corrected by the new γ-correction table, and output.

The above-described operation is a part 2 for performing G and B γ correction.
By performing the same for 5G and 25B, the γ correction operation of the γ correction circuit 20c can be changed.

Next, the control means 30c will be described. The control means 30c includes a CPU 31c and a gradation distribution characteristic forming circuit 32.
It is composed of the RAM 33 and performs the same operation as the control means 30a in the first embodiment. A major difference from the first embodiment is that the CPU 31a in the first embodiment rewrites the γ correction table during the blanking period, whereas the CPU 31c in the present embodiment is not restricted by blanking.

According to this embodiment, since the data from the control means is transferred to the RAM to change the γ correction table, a large capacity ROM for holding a large number of γ correction tables is provided. It is not necessary, and a display device using a large number of γ correction tables as compared with the first and second embodiments can be realized at low cost.

FIG. 6 shows a block diagram of the fourth embodiment of the present invention. The major difference of this embodiment from the third embodiment is that
The point is that the sensor circuit 50 including the light amount sensor 51 and the A / D converter 52 is added, and the CPU 31d is provided with an interface terminal with the sensor circuit 50.

In FIG. 6, reference numeral 51 is a light quantity sensor for measuring the brightness of external light and outputting it as a voltage, and 52 is an A / D converter for converting an analog signal output from the light quantity sensor 51 into a digital signal. . The light quantity of the external light is converted into a voltage by the light quantity sensor 51 and sent to the A / D converter 52. The A / D converter 52 converts the signal from the light amount sensor 51 into digital data and outputs it to the control means 30d.

The control means 30d controls the γ correction circuit according to the output signal of the sensor circuit 50 and the input video signal. A specific configuration example of the control means 30d will be described below. Three
1d uses the signal from the γ correction circuit and the signal from the sensor, and according to the program in the ROM 34, the γ correction circuit 20
It is a CPU that controls c. As a specific example of the operation of the CPU 31d, the data from the sensor circuit 50 is CP
Judgment is made by the sensor signal correction table inside U31d, and when the light quantity is large, it becomes difficult to discriminate the gradation of the dark portion.
The screen is brightened by moving the correction curve to the white side of the output, and when the amount of light is small, it becomes easier for the human eye to distinguish the gradation difference in the dark part. Therefore, instead of moving it to the black side to darken the screen, the white side To reduce the loss of gradation. When the above control and the automatic adjustment of the γ correction curve of the first embodiment are used together, the number of output gradations with respect to the number of input gradations on the white side of the output gradations is reduced in order to make the screen brighter when the light amount is large, The gradation is slightly expanded by increasing the number of output gradations with respect to the number of input gradations on the black side. When the amount of light is small, a part of the output gradation is expanded to darken the screen a little, but the gradation is suppressed.

By the above operation, when the surroundings are bright, the screen is brightened to improve the visibility, and when the surroundings are dark, it is possible to suppress the gradation deterioration instead of lowering the brightness of the screen. The other parts are the same as those in the third embodiment, and the description thereof is omitted.

Although the light quantity sensor is taken as an example of the sensor circuit 50 in the above description, the light quantity sensor is not limited to the light quantity sensor, and the external environment that causes a change in display characteristics of a display element such as a temperature sensor and a humidity sensor and a human secretary type is also present. It is also possible to install a sensor that captures the change in the γ correction characteristic to obtain the most visible γ correction characteristic.

In this embodiment, the control means is a CPU and a RAM,
Although the ROM is used, a device that performs the same operation may be assembled with a gate or the like. On the contrary, if there is a margin in the operating speed of the CPU, a part assembled by a gate, for example, the gradation distribution characteristic forming circuit 32
Can be incorporated into the operation of the CPU. Further, instead of the γ correction circuit 20c of this embodiment, the γ correction circuits 20a and 20b of the first and second embodiments can be used by switching the γ correction table with a signal from the control means. is there. If a sufficient number of γ correction tables are not prepared in the γ correction circuit in the above case, the control means may select the closest γ correction table.

FIG. 7 shows a block diagram of the fifth embodiment of the present invention. The major difference between this embodiment and the third embodiment is V
It has two signal input parts, that is, an input part 70 for inputting a video image signal from a TR or the like and an input part 71 for inputting a computer image signal from a personal computer (hereinafter abbreviated as PC). The point is to display, and at this time, the switching instruction circuit 6 is also provided to the CPU 31e.
This is the point where the switching signal from 0 is input.

The control means 30e receives the switching signal from the switching instruction circuit 60 and the video signal from the switching switch 80 as input, and according to the two signals, the γ correction circuit 20
Change the γ correction curve at c. Control means 30e below
An example of the operation and configuration of will be described. 31e receives the switching signal and the video signal from the switching instruction circuit 60 as input, and based on the histogram of the input signal formed on the RAM 32 and the switching signal, the γ correction circuit 20c outputs γ.
This is a CPU that changes the content of correction.

The case where the changeover switch 80 is on the video side is similar to that of the third embodiment, so a detailed description is omitted, and the case where the changeover switch 80 is on the personal computer side will be described.

Normally, the number of gradations that a personal computer can display is limited. Therefore, consider a case in which the number of output gradations of the signal source is smaller than the number of displayable gradations of the display device and the number of gradations is known in advance. For example, when the input grayscale is four grayscales as shown by the broken line in FIG. 8 and the grayscale to be output is as shown by the one-dot chain line in FIG. It is better to use the γ curve of. At this time, in order to reduce the influence of noise as much as possible, the part where the gradation of the γ curve changes is in the middle of the input gradations. For example, the boundary x2 of the part where the input gray levels in FIG. 8 are x1 and x3 is represented by x2 = (x1 + x3) / 2. The CPU 31e forms the stepwise γ curve from the histogram of the input signal, and sets the optimum γ curve on the RAM 33. After that, the contents of the γ correction on the γ correction circuit 20c are changed in the same manner as when the changeover switch is on the video side.

Further, when the number of displayable gray scales of the display device is very close to the number of output gray scales of the signal source, for example, when a personal computer capable of 512 color output is displayed on the display device capable of 512 color display, a changeover switch. If the same γ correction as that on the video side is performed, the gradation is destroyed, and when the distinguished gradation is displayed on the signal source side, the same gradation is displayed. To solve the above problems,
When the number of displayable gray scales of the display device is very close to the number of output gray scales of the signal source, a linear one in which the γ characteristic linearly changes from black to white is used. In addition, this method uses FRC (Frame Rat
display device using a multi-gradation method such as e Control), eg 5
40 by using FRC on the liquid crystal display panel that can display 12 colors
This is also effective when connecting a personal computer capable of outputting 512 colors to a display device displaying 96 colors.

The configuration and operation of the other blocks are the same as those in the third embodiment, and therefore their repetitive description will be omitted.

As described above, according to the present embodiment, it is possible to perform γ correction on a plurality of signal sources in accordance with the signal source and the input signal, and it is possible to perform the optimum γ correction corresponding to each signal source. I can.

In the present embodiment, the TV is used for convenience of explanation.
Although the case where two signal sources of a personal computer and a personal computer are used for input, three or more signal sources may be switched, or two signal sources that generate the same type, for example, a video image signal may be brought. good.

FIG. 9 shows a block diagram of a sixth embodiment of the present invention. The major difference of this embodiment from the second embodiment is that a video signal obtained by combining a video image and a personal computer image is input from a computer or the like, and at the same time, a control signal from the personal computer or the like, which is a signal source, is input to the control means. There is an interface terminal for this.

In FIG. 9, reference numeral 100 is a video signal source such as a VTR, and 71 is a so-called multimedia personal computer capable of obtaining a video signal obtained by synthesizing a video signal such as a VTR and computer information. Reference numeral 72 denotes an interface terminal for inputting to the CPU 31f a control signal from the multimedia personal computer 71, for example, a key signal or the like for distinguishing a TV video portion of a combined image from a personal computer video portion. 30f is a control means.

The control means 30f controls the γ correction circuit 20b according to an external control signal such as a key signal and the input video signal. A specific example of the operation and configuration of the control means 30f will be shown below. Reference numeral 31f is a CPU, which changes the correction content of the γ correction circuit according to an external control signal such as a key signal and an input video signal. The method by which the control means 30f changes the contents of the γ correction circuit 20b is in accordance with the fourth embodiment.

The composite image of the TV and the personal computer combined by the personal computer 71 is signal-corrected by the γ correction circuit 20b according to a correction table determined in advance by the control means 30f, and sent to the matrix display panel 40 for display. It

Since the other parts are similar to those of the second embodiment, the repetitive description will be omitted.

As described above, by using this embodiment, it becomes possible to control the γ correction by both the external computer and the video signal. Thereby, for example, fine adjustment of the image quality is performed from the personal computer side, or a signal for distinguishing between the TV video portion and the personal computer video portion of the combined image is sent from the personal computer, and accordingly, as in the second embodiment. By switching γ, it becomes possible to change the γ correction of the part where the TV is combined on one screen and the original image part of the personal computer, and a better image can be displayed.

It is also possible to use the γ correction circuits of the first and third embodiments as the γ correction circuit 20 of this embodiment.
If the γ correction circuit cannot be changed quickly enough in the above-mentioned case, two sets of γ correction circuits are prepared and the two are switched. When the γ correction circuit of the third embodiment is used, both the control signal and the data may be sent from the control means to the γ correction circuit as in the third embodiment.

[0071]

According to the present invention, since the contents of γ correction are changed according to the contents of the input signal, it is possible to obtain a good display according to the contents of the signal in a matrix display panel having a limited dynamic range.

Further, according to the present invention, it is possible to realize the γ correction in which the change in color due to the γ correction is suppressed.

Further, according to the present invention, by changing the content of γ correction depending on whether the signal source is a TV signal or a signal from a personal computer or the like, a good display can be obtained regardless of the type of signal source.

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is a graph showing a basic γ correction curve and a histogram of input gradation.

FIG. 3 is a graph showing a corrected γ correction curve.

FIG. 4 is a block diagram of a second embodiment of the present invention.

FIG. 5 is a block diagram of a third embodiment of the present invention.

FIG. 6 is a block diagram of a fourth embodiment of the present invention.

FIG. 7 is a block diagram of a fifth embodiment of the present invention.

FIG. 8 is a graph showing an example of a γ correction curve for a signal source such as a personal computer.

FIG. 9 is a block diagram of a sixth embodiment of the present invention.

[Explanation of symbols]

20a to c ... γ correction circuit, 21a to c, 251a, 2
52a, 321, 33 ... RAM, 23, 24a to c,
34 ... ROM, 26 ... Changeover switch, 30a-f
... Control means, 31a to f ... CPU, 32 ... Histogram forming circuit, 40 ... Display device, 50 ... Sensor circuit,
51 ... Light intensity sensor, 52 ... A / D converter, 6
0 ... Changeover circuit, 72 ... Personal computer, 80 ... Changeover switch, 100 ... VTR.

Claims (5)

[Claims] 1. A display device having a display element and a γ correction circuit, wherein a video signal is input, and the correction content of the γ correction circuit is changed based on the signal content of the video signal and the display characteristics of the display element. Control means for outputting the control signal of
And a γ-correction circuit that applies γ-correction determined according to the control signal to an input video signal. 2. A display device having a display element and a γ correction circuit, wherein a sensor circuit for sensing an external environment of the display device and giving it to a control circuit as data, and an output signal and a video signal of the sensor circuit are input. Based on the signal content of the video signal, the external environment sensed by the sensor circuit, and the display characteristics of the display element, the control means for outputting a control signal for changing the correction content of the γ correction circuit and the control signal are determined according to the control signal. A display device comprising: a γ correction circuit that performs γ correction on an input video signal. 3. A display device having a display element and a γ correction circuit, wherein at least two types of video signals are input, and one of the input video signals is selected and a changeover switch to be applied to the γ correction circuit is selected. A switching instruction circuit for instructing a changeover switch of a video signal, and for changing correction contents of a γ correction circuit described later based on the selected video signal, an instruction signal from the changeover instruction circuit, and display characteristics of the display element. And a γ correction circuit that performs γ correction determined on the video signal output from the changeover switch according to the control signal from the control unit and outputs the result. A display device characterized by the above. 4. A γ correction circuit for inputting red, blue and green (hereinafter abbreviated as R, G, B) primary color video signals, performing γ correction on the video signals and outputting a result, R, G , B, each γ-correction circuit is provided with a γ-correction table that also uses the other two colors. 5. The γ-correction circuit according to claim 4, wherein the γ-correction circuit that outputs the first primary color signal has a second input,
A display device characterized in that the third primary color signal input gradation number is smaller than the first primary color signal input gradation number.