JP2000209462A - Gamma correction circuit and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To conduct gamma correction using a gamma correction coefficient conformable to video signals by allowing setting the gamma correction coefficient in response to an input video signal, transferring gamma correction coefficient data to a display device for a vertical blanking period of the video signal and displaying the data on a display device so as to set the gamma correction coefficient corresponding to one kind of video source. SOLUTION: A signal delayed by one frame and outputted from a memory 3 is given to a DSP, where resolution is converted so as to match the number of pixels of the signal with that of a fixed display panel. The signal whose resolution is converted is given to a lookup table, in which gamma correction is conducted. A data rearrangement circuit 7 rearranges output data of a gamma correction RAM 5 for display on a plasma display panel 10, the rearranged data signal is given to a horizontal driver 8 and a vertical driver 9 to drive the plasma display panel 10. In the case that a liquid crystal display panel is employed in place of the plasma display panel 10, no data rearrangement circuit 7 is required. A video state detection circuit 6 detects a state of the video signal given to the memory 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gamma correction circuit and a display device, and more particularly to a gamma correction circuit capable of freely setting a gamma correction coefficient, and a display applied to a plasma display panel or a liquid crystal panel having fixed pixels. Related to the device.

[0002]

2. Description of the Related Art In recent years, not only display devices using cathode ray tubes, but also flat type liquid crystal panels, plasma displays, electron emission displays and the like have been developed and sold.

[0003] The light emission characteristics of these display devices are detected and gamma corrected to correct the linearity of the luminance characteristics and color characteristics in the display on the screen.

Therefore, the gamma correction coefficient differs for each type of display device, and gamma correction that matches the light emission characteristics of the display device is required for each display device based on variations in manufacturing aspects.

One solution to this demand is disclosed in
No. 3,113,393 is disclosed. In other words, when gamma correction is performed with high accuracy when the display devices are different or the light emission characteristics vary, it is necessary to change the correction coefficient according to each display device. FIG. 8 shows the configuration of this automatic gamma correction device. In the figure, in order to detect the light emission characteristics of the display device, "dark"
A shading image S3 of a video signal is generated by the microcomputer 21 to generate a sawtooth wave that changes linearly from “bright” to “bright”, and the video signal S1 and the switch 22 are displayed by the video signal S1 and displayed outside the bezel 9 area which is the display range of the video signal. The video signal is processed by the video signal processing circuit 24 through the memory unit 23 in which the switching and the gamma correction coefficient are written, and is displayed on the display unit 25. The result of displaying the shading image S3 is read by the photo sensors 26a to 26c, and the A / D converter 2
The digital signal is converted into a digital signal by the microcomputer 7 and written into the memory unit 23 by the microcomputer 21 as a gamma correction coefficient in accordance with the deviation from the linearity from the read sensor intensity at each point.

Further, the shading image S3 can be set in an inconspicuous place such as up and down, left and right of the display screen, and there is a synchronization processing section 28 for synchronizing the display section 25 in accordance with a horizontal / vertical synchronization signal. And

In this manner, the photo sensors 26a-26
c, a microcomputer 21 for generating and shading image S3 and calculating and detecting a gamma correction coefficient, and an A / D converter 27
And the switch 22 perform gamma correction suitable for the display device.

[0008]

However, the above-described gamma correction method in the conventional video display device described above uses a method in which one or several types of predetermined correction coefficients are switched for one type of video source. Lord.

For this reason, it has not been possible to always select an optimum gamma correction coefficient according to the displayed video signal.

When the state of the video signal is detected and a new gamma correction coefficient is switched, a video signal in a different state is already displayed, so that a gamma correction coefficient suitable for the displayed video can be selected. Did not.

Here, as a second conventional example, an embodiment of a fixed pixel display device using a gamma correction method will be described with reference to FIG.

According to FIG. 7, the image state detecting circuit 6
The A / D converter 2 converts an input video signal into a digital signal, and the resolution conversion processing circuit 4 detects a video signal state based on the resolution-converted signal.

Therefore, the gamma correction data to be changed is
The data is always transferred to the gamma correction data storage RAM (LUT) 5 as information delayed by one frame or more with respect to the display image, and the data rearrangement circuit 7 rearranges the data to display the plasma display panel 10. ,
The rearranged signals are input to the horizontal driver 8 and the vertical driver 9 to drive the plasma display panel 10. The timing generation circuit 11 generates a timing signal for obtaining the timing of each unit. Therefore,
In this case, since gamma correction is performed with information delayed by one frame or more, gamma correction corresponding to a video signal cannot be performed.

The present invention has been made in order to solve the above-mentioned various problems. A gamma correction coefficient corresponding to one kind of video source is set, and a gamma correction coefficient suitable for a video signal is detected. And gamma correction.

[0015]

According to the present invention, in a display device for displaying a gamma-corrected video signal, a coefficient of the gamma correction can be set according to an input video signal, and during a vertical blanking period of the video signal. And transmitting the gamma correction coefficient data to a display unit.

Further, the present invention provides a gamma correction circuit for obtaining a gamma corrected video signal, an A / D converter for converting an input video signal into a digital signal, a memory for storing the digital signal for one frame, Image state detecting means for detecting an image state of a digital signal, gamma correction data generating means for receiving an output of the memory as input, and generating gamma correction data according to an image state from the image state detecting means, and gamma correction data generating means And temporary storage means for storing the output of

Further, according to the present invention, in a display device for displaying a gamma-corrected video signal, an A / D converter for converting an input video signal into a digital signal, a memory for storing the digital signal for one frame, Image state detecting means for detecting an image state of a digital signal, gamma correction data generating means for receiving an output of the memory as input, and generating gamma correction data according to an image state from the image state detecting means, and gamma correction data generating means Temporary storage means for storing the output of the temporary storage means, data rearrangement means for rearranging the read signals of the temporary storage means, a horizontal driver rearranged by the data rearrangement means to drive the horizontal direction, and a vertical driver A vertical driver, and a display driven by the horizontal driver and the vertical driver. .

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments according to the present invention will be described.
This will be described in detail with reference to the drawings.

FIG. 1 shows a configuration diagram of a video signal processing unit according to an embodiment of the present invention. In the figure, 1 is an analog video signal, and 2 is an A / A that converts analog to digital.
A D converter, 3 is a frame memory for storing a primary digital signal, 4 is a resolution conversion processing circuit and / or a gamma correction DATA generation circuit (DSP), and 5 is a D for performing gamma correction.
An ATA generation circuit (LUT), 6 is an image state detection circuit for detecting an image state of a digital signal, 7 is a data rearrangement circuit for rearranging data for a plasma display, 8 is a horizontal driver, 9 is a vertical driver, and 10 is a plasma. It is a display panel. Further, reference numeral 11 denotes a timing generation circuit, which generates a timing signal for setting the timing of each unit.

A video signal input from an image pickup apparatus or after receiving TV demodulation is converted into a digital signal by an A / D converter 2. The digitally converted signal is input to the memory 3 and is delayed by one frame.

The signal output from the memory 3 and delayed by one frame is subjected to resolution conversion processing 4 by the DSP 4 so as to match the number of pixels of the fixed pixel display panel. The signal having undergone the resolution conversion processing is stored in a lookup table (LUT) 5
Performs gamma correction processing.

After that, in the present embodiment, in order to display the plasma display panel 10, the data is rearranged by the data rearranging circuit 7, and the rearranged signals are inputted to the horizontal driver 8 and the vertical driver 9, and the plasma is transmitted. The display panel 10 is driven. In the case of a liquid crystal panel, the data rearranging circuit 7 is unnecessary.

At the same time, the image state detection circuit 6 detects the state of the image signal input to the memory 3, and
An optimal gamma correction coefficient is selected for the video signal. This gamma correction coefficient is determined from the pattern of the image signal, and a plurality of types are stored in a memory (not shown) as a fine adjustment gamma correction coefficient according to brightness and darkness on the screen, hue, and the like,
By detecting the video state of the video signal, an optimal gamma correction coefficient is selected and output to the DSP 4.

The selected gamma correction coefficient is output to the DSP 4 during the vertical blanking period, and creates data that can be input to the LUT 5 there.

After the data is created, new gamma correction conversion data is transferred to the LUT 5. Timing necessary for these processes is performed by the timing generation circuit 11.

Hereinafter, the operation of the present embodiment will be described with reference to FIGS. 2, 3, 4, and 5.

First, the state of normal video signal processing is shown in FIG.
Shown in The video signal input from code 1 is converted to a digital signal by the A / D converter 2. The digitally converted signal is input to the memory 3 and is delayed by one frame.

The signal output from the memory 3 and delayed by one frame is subjected to resolution conversion processing 4 by the DSP 4 so as to match the number of pixels of the fixed pixel display panel. The signal having undergone the resolution conversion processing is stored in a lookup table (LUT) 5
Performs gamma correction processing.

Thereafter, in this embodiment, in order to display the plasma display panel, the data is rearranged.
The rearranged signals are input to the horizontal driver 8 and the vertical driver 9 by the data rearranging circuit 7, and the plasma display panel 10 is driven.

FIG. 4 shows this processing in chronological order.
According to FIG. 4, for each vertical synchronization signal (FIG. 4 (a)), the output of the memory 3 (FIG. 4 (c)) is delayed by one frame with respect to the input of the memory 3 (FIG. 4 (b)). Becomes The output of the resolution conversion processing 4 (FIG. 4D) is synchronized with the output of the memory 3, and the gamma correction circuit (LUT) 5 is the same frame signal as the output of the memory 3 (FIG. 4E). )).
Here, in the NTSC system, the vertical synchronizing signal refers to a vertical synchronizing pulse period interposed between the vertical blanking periods 1 to 21H and 263 to 273H middle equalizing pulses 3H, 3H before and 18H after the vertical synchronizing pulse period. During this period, the gamma correction is executed using a period not displayed on the screen.
Similarly, in other high-vision signals and non-interlaced display devices, the gamma correction is executed in the vertical flyback period in synchronization with the vertical synchronization signal.

Next, the operation during the vertical blanking period is shown in FIG. The video state detection circuit 6 detects the state of the video signal input to the memory 3 and selects an optimal gamma correction coefficient for the video signal. The selected gamma correction coefficient is transferred to the DSP 4 within the vertical flyback period,
The data is converted into a data format that can be transferred to the LUT 5 at P4. After the conversion, the data is transferred to the LUT 5 as new gamma correction data.

FIG. 5 shows this processing in chronological order. According to FIG. 5, the vertical synchronizing signal is a vertical synchronizing pulse period (NTSC system), and based on the vertical synchronizing signal (FIG. 5A), the input signal period N of the video state detection circuit 6 is determined.
Indicates that the video signal rises after the vertical synchronization signal (FIG. 5).
(B)), stop before the vertical synchronization retrace period, and then output the gamma correction coefficient output P (FIG. 5C), the output Q of the gamma correction data generation circuit 4 (FIG. 5D), and The output of the LUT 5 as the correction data storage RAM (FIG. 5E) is obtained.

FIGS. 6A and 6B show the resolution conversion circuit 4.
And the connection of signals during the display of the video signal on the gamma correction data storage RAM (LUT) 5 and during the vertical blanking period, and are not limited in any case.

FIG. 6A shows a connection at the time of displaying a video signal. In this case, the gamma correction data storage RAM
5 operates as a look-up table. FIG. 6B shows the connection during the vertical blanking period.
In this case, the gamma correction data storage RAM 5 performs a data write operation.

In the above embodiment, the display device is described as a plasma display panel. However, a gamma correction by a gamma correction coefficient for correcting the linearity of a projected image on the panel surface is also performed in a cathode ray tube, a liquid crystal panel, or the like. This is also effective in improving the resolution as a result.

[0036]

As described above, according to the present invention,
It is possible to provide a fixed pixel display device capable of performing more precise gamma correction in synchronization with a display image than the conventional gamma correction.

In particular, also in the case of a predetermined display device such as a plasma display panel, a gamma correction coefficient adapted to the display device and a gamma correction coefficient corrected by a video signal one frame before are taken into consideration. With a comprehensive gamma correction coefficient based on the video signal, it is possible to display a realistic video signal on the entire screen.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram of a gamma correction circuit and a display device according to the present invention.

FIG. 2 is a state block diagram of a gamma correction circuit and a display device according to the present invention.

FIG. 3 is a state block diagram of a gamma correction circuit and a display device according to the present invention.

FIG. 4 is a timing chart illustrating the operation of the gamma correction circuit according to the present invention.

FIG. 5 is a timing chart illustrating the operation of the gamma correction circuit according to the present invention.

FIG. 6 is a block diagram showing a transitional configuration of a gamma correction circuit according to the present invention.

FIG. 7 is a configuration block diagram of a conventional gamma correction circuit and a display device.

FIG. 8 is a transitional block diagram of a gamma correction circuit according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Analog video signal 2 A / D converter 3 Frame memory 4 Resolution conversion processing circuit and / or gamma correction DATA
Generating circuit (DSP) 5 DATA generating circuit (LUT; RAM) 6 Video state detecting circuit 7 Data rearranging circuit 8 Horizontal driver 9 Vertical driver 10 Plasma display panel 11 Timing generating circuit

Claims (6)

[Claims] 1. A display device for displaying a gamma-corrected video signal, wherein the gamma correction coefficient can be set according to an input video signal, and the gamma correction coefficient data is set during a vertical blanking period of the video signal. A display device, which transfers the data and displays it on a display. 2. The display device according to claim 1, wherein the transferred gamma correction coefficient data has a gamma correction coefficient suitable for a display image being currently displayed. 3. The display device according to claim 1, wherein a resolution conversion processing circuit required for the display device is switched as a gamma correction data generation circuit during the vertical blanking period. 4. When the gamma correction coefficient data is transferred during the vertical blanking period, a signal line used for video transfer during a video display period is shared with the gamma correction coefficient data transfer line. The display device according to claim 1 or 2, wherein 5. A gamma correction circuit for obtaining a gamma-corrected video signal, an A / D converter for converting an input video signal into a digital signal, a memory for storing the digital signal in one frame, and an image of the digital signal. Image state detecting means for detecting a state, gamma correction data generating means for receiving an output of the memory as input, generating gamma correction data according to the image state from the image state detecting means, and storing an output of the gamma correction data generating means A gamma correction circuit, comprising: 6. A display device for displaying a gamma-corrected video signal, an A / D converter for converting an input video signal into a digital signal, a memory for storing one frame of the digital signal, and a video of the digital signal. Image state detecting means for detecting a state, gamma correction data generating means for receiving an output of the memory as input, generating gamma correction data according to the image state from the image state detecting means, and storing an output of the gamma correction data generating means A temporary storage unit, a data rearrangement unit that rearranges the read signals of the temporary storage unit, a horizontal driver that is rearranged by the data rearrangement unit and drives in the horizontal direction, and a vertical driver that drives in the vertical direction. A display device comprising a display driven by the horizontal driver and the vertical driver.