JP2006030588A - Image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-performance image display device by controlling the luminance of an LED backlight in units of pixels.
In an image display device including a liquid crystal panel 5 having a backlight 8 and a display control unit for controlling the display of the liquid crystal panel 5, the backlight 8 is composed of LEDs and one or more LEDs per LED. The display control unit includes an image processing unit 1 that performs image processing such as YC separation, color demodulation, IP conversion, and scaling on an input video signal, and an output video signal from the image processing unit 1 on a liquid crystal panel. 5, a liquid crystal controller 2 that performs signal processing and timing generation for display, a gate driver 3 and a source driver 4 that drive a driving element (FET) of the liquid crystal panel 5, an average luminance information of an input video signal, and a black level region The screen information analyzing means 6 for detecting the white level area and the control signal output from the screen information analyzing means 6 for each LED backlight. LED backlight control means 7 for outputting a current control signal for controlling the brightness of the LED.
[Selection] Figure 1

Description

  The present invention relates to a television receiver (hereinafter referred to as “TV”) or a luminance signal adjustment circuit of a monitor using a liquid crystal, PALC (plasma address liquid crystal) or the like as a display device and an LED backlight as a light source. The present invention relates to an ACC (Automatic Contrast Circuit) circuit that varies the luminance of each LED backlight according to a signal.

  In recent years, with the trend toward larger screens and higher image quality of TVs, it is indispensable to install an ACC circuit that automatically adjusts the gamma curve of a signal and creates a contrast feeling of an image. FIG. 3 shows a conventional ACC circuit, which will be described below. In FIG. 3, the video signal S input to Ie is input to the screen information analysis circuit 6 to perform screen average luminance, black level region area detection, white level region area detection, and the like. And the control signal Sc is output.

  At the same time, the video signal S is input to the ACC circuit 9 and arithmetically processed by the control signal Sc to become a sharp video and output as a video signal Of. The video signal Of is input to the image processing circuit 1 and is output to the video signal Os through image processing such as IP conversion and scaling. The video signal Os is input to the liquid crystal controller 2, performs timing generation and signal processing, and is output as a digital signal Cs. The digital signal Cs is transmitted to the liquid crystal panel 5 through the gate driver 3 and the source driver 4 and displayed using the backlight 10 as a light source.

  For example, when processing a so-called black stretch that drops a signal component below a specific brightness in a dark direction in a scene with high brightness on the entire screen, or to enhance white peak brightness to emphasize white characters on the screen. When the white expansion process is performed, the ACC circuit performs a digital operation. In digital arithmetic, a rounding error due to arithmetic occurs as a generally-known drawback (see FIG. 4). Line A is the current signal, and ◯ is the sampling point of the current signal. If it is assumed that an operation such as B is performed, an ideal process results in a waveform after the operation such as line C or Δ. However, an operation result such as the rounding result □ is obtained.

Increasing the bit width tends to reduce the calculation error, but it is in a trade-off with an increase in cost. Such a calculation error becomes more noticeable as the digital calculation becomes more complicated and the number of times is increased, and the error calls an error. Such an error is displayed as a Mach band (gradation failure) on the screen, which causes deterioration of the image quality.
In addition, various proposals have been made using LEDs having excellent performance such as a backlight light source that can be driven at a lower voltage than a fluorescent tube, consume less power, and have a long lifetime. In Patent Document 1, at least one LED serving as a light source that emits illumination light to irradiate a liquid crystal panel is arranged for each of a plurality of divided regions, and the LED control circuit receives at least illumination light in accordance with a video signal. By driving and controlling the LEDs in units of divided areas so that only the necessary screen area is irradiated with illumination light, the screen area that does not need to be illuminated is basically not irradiated with illumination light, This is a proposal to reduce power consumption required for illumination.
JP2001-142409A

  In the above-described conventional example, a Mach band (gradation failure) due to a calculation error occurs in order to digitally calculate an input video signal in realizing the ACC circuit, and there are problems such as deterioration in video quality.

  An object of the present invention is to provide a high-performance ACC by solving the above-described problems and controlling the luminance of an LED backlight in units of pixels.

  The present invention relates to a signal processing means for inputting a video signal and performing various video signal processing, an analysis means for analyzing video information of the video signal, and a control means for outputting a luminance control signal of an LED backlight according to the analysis result. And generating means for performing timing generation and signal conversion for displaying an image on the liquid crystal panel, driving means for driving the liquid crystal panel by a signal of the generating means, a liquid crystal panel, and an LED backlight. It is.

  That is, the present invention provides an image display device comprising a liquid crystal panel having a backlight and a display control unit for controlling the display of the liquid crystal panel. The backlight is composed of LEDs, and one or more LEDs are included in one LED. The display control unit includes an image processing unit that performs image processing such as YC separation, color demodulation, IP conversion, and scaling on an input video signal, and an output video signal from the image processing unit as a liquid crystal panel. A liquid crystal controller that performs signal processing and timing generation for display, a gate driver and a source driver that drive a driving element (FET) of the liquid crystal panel, average luminance information of the input video signal, black level region detection, and white level region Screen information analyzing means for performing detection, and control signals output from the screen information analyzing means for each LED backlight. An image display device having a LED backlight control means for outputting a current control signal for controlling the degree.

  The present invention also provides an image processing circuit that inputs an input video signal, performs YC separation, color demodulation, IP conversion, scaling, etc., and outputs the video signal, and displays the video signal output from the image processing circuit on a liquid crystal panel A liquid crystal controller that performs signal processing and timing generation, a gate driver and a source driver that drive a liquid crystal panel drive element (FET), a liquid crystal panel that displays a screen, average luminance information of an input signal, and a black level region A screen information analysis circuit for performing detection and white level region detection; and an LED backlight control means for outputting a current control signal for controlling the luminance of each LED backlight by a control signal output from the screen information analysis circuit. An image display device.

  And this invention is an image display apparatus in which the said LED backlight control means is comprised by the microcomputer.

  Furthermore, the present invention is the image display device in which the LED backlight control means outputs a current control signal that completely blocks the luminance of the LED backlight.

  According to the present invention, it is possible to operate a high-quality ACC circuit without causing gradation defects such as a Mach band even when ACC control typified by black stretching or white stretching is performed.

The best mode for carrying out the present invention will be described.
Embodiments of an image display apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a circuit configuration diagram of the image display apparatus according to the first embodiment. FIG. 2 is a circuit configuration diagram illustrating a specific circuit of the LED backlight control circuit according to the first embodiment.

  Examples will be described in detail. FIG. 1 shows a circuit configuration diagram of the image display apparatus of this embodiment. The same circuits as those in FIG. 2 are given the same reference numerals. The image display apparatus according to the present embodiment includes a liquid crystal panel having a backlight and a display control unit that controls display of the liquid crystal panel. The backlight includes LEDs, and one LED includes one or more pixels. The display control unit displays an image processing means for performing image processing such as YC separation, color demodulation, IP conversion, and scaling on the input video signal and an output video signal from the image processing means on the liquid crystal panel. A liquid crystal controller that performs signal processing and timing generation, a gate driver and a source driver that drive a driving element (FET) of a liquid crystal panel, and average luminance information, black level region detection, and white level region detection of an input video signal Screen information analysis means and current control signals for controlling the brightness of individual LED backlights by the control signal output from the screen information analysis means That having a and LED backlight control means for outputting.

  In FIG. 1, an input video signal S is displayed on a liquid crystal panel 5 through an image processing circuit 1, a liquid crystal controller 2, a gate driver 3, and a source driver 4. At the same time, the input signal S is input to the screen information analysis circuit 6. The screen information analysis circuit 6 first obtains the average luminance of the entire screen and the area of the black region below an arbitrary threshold A. When the average luminance is equal to or greater than an arbitrary threshold B and the area of the black region with respect to the entire screen is equal to or less than the arbitrary threshold C, the displayed screen is determined to be a bright screen as a whole. Considering the characteristics, there is an effect of increasing the apparent gradation characteristic by dispersing the luminance distribution of each gradation by lowering the luminance of the signal below the mutation point with a certain luminance as the mutation point. The screen information analysis circuit 6 calculates the luminance change amount of each pixel and outputs a control signal Sc. The LED backlight control circuit 7 obtains a current value for each pixel of the LED backlight 8 based on the control signal Sc, and outputs a current control signal Si. The LED backlight 8 causes each LED to emit light with a designated brightness by the current control signal Si. The LED current control signal Si is an analog signal, and the luminance of the LED changes linearly according to the flowing current. Therefore, it is possible to perform a black extension operation in which no gradation failure such as a Mach band occurs.

  At the same time, the screen information analysis circuit 6 obtains the area of the white region where the input video signal S is equal to or greater than the threshold D of the arbitrary luminance. When the area of the white area with respect to the entire screen is equal to or less than an arbitrary threshold value E, it is determined that the white area in the displayed screen is a character or a fine white peak. In such a case, taking the brightness of the human eye into account as a mutation point and increasing the luminance of the signal above the mutation point, the human eye is a sharp image with a clear luminance peak. There is an effect to recognize. The screen information analysis circuit 6 calculates the luminance change amount of each pixel and outputs a control signal Sc. Thereafter, as described above, the brightness of each LED is changed, and a white expansion operation in which no gradation failure such as a Mach band occurs can be performed.

  As in this embodiment, by controlling the luminance level of each LED based on the analysis result of the video information of the input video signal S, the luminance of the visual video is changed, and the ACC circuit has few gradation defects Can be operated.

  FIG. 2 shows a specific circuit example of the LED backlight control circuit 7 of FIG. A CPU (Central Processing Unit) 11 performs complex calculation processing and table reference on the control signal Sc obtained from the screen information analysis circuit 6, thereby enabling higher-performance LED luminance control.

  As described above, according to the present embodiment, the brightness level of each LED can be changed by the input signal, the optimum ACC circuit can be operated, and the system corresponding to high image quality. Can be provided.

The circuit block diagram in the image display apparatus of an Example. The circuit block diagram explaining the specific circuit of the LED backlight control circuit in an Example. The circuit block diagram of a prior art. The signal waveform diagram for demonstrating a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image processing circuit 2 Liquid crystal controller 3 Gate driver 4 Source driver 5 Liquid crystal panel 6 Screen information analysis circuit 7 Backlight control circuit 8 LED backlight 9 ACC circuit 10 Backlight 11 CPU

Claims (4)

In an image display device comprising a liquid crystal panel having a backlight and a display control unit for controlling display of the liquid crystal panel,
The backlight is composed of LEDs and one or more pixels correspond to each LED, and the display control unit performs image processing such as YC separation, color demodulation, IP conversion, and scaling on the input video signal. An image processing unit, a liquid crystal controller for performing signal processing and timing generation for displaying an output video signal from the image processing unit on a liquid crystal panel, a gate driver and a source driver for driving a driving element (FET) of the liquid crystal panel; Screen information analysis means for detecting average luminance information, black level area detection and white level area detection of the input video signal, and current control for controlling the brightness of each LED backlight by a control signal output from the screen information analysis means An image display device comprising LED backlight control means for outputting a signal.   An image processing circuit for inputting an input video signal, performing YC separation, color demodulation, IP conversion, scaling, etc., and outputting the video signal; and signal processing for displaying the video signal output from the image processing circuit on a liquid crystal panel; Liquid crystal controller that generates timing, gate and source drivers that drive the drive elements of the liquid crystal panel, liquid crystal panel that displays the screen, and screen that performs average luminance information of input signals, black level area detection, and white level area detection An image display device comprising: an information analysis circuit; and an LED backlight control means for outputting a current control signal for controlling the luminance of each LED backlight by a control signal output from the screen information analysis circuit.   The image display device according to claim 1, wherein the LED backlight control unit is configured by a microcomputer.   The image display device according to claim 1, wherein the LED backlight control unit outputs a current control signal that completely blocks the luminance of the LED backlight.

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