JP3110340B2 - Backlight control method and liquid crystal display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight control system and a liquid crystal display, and more particularly, to a liquid crystal display (LC).
The present invention relates to a backlight control method for controlling the luminance of a backlight used in D) and a liquid crystal display device.

[0002]

2. Description of the Related Art In a conventional backlight of a liquid crystal display device, an attempt is made to achieve a uniform illumination surface by using a cathode tube and a light diffusion plate (or a light guide plate). There is a method to put in. In the case of a backlight requiring a large screen or high brightness, a method of placing a cathode tube directly below a light diffusion plate is generally used.

In addition, various backlight control methods and liquid crystal display devices for controlling the luminance of the backlight have been proposed (Japanese Patent Application Laid-Open Nos. 5-127626 and 3).
198,026).

FIG. 3 is a block diagram showing an example of a conventional backlight control system described in Japanese Patent Application Laid-Open No. 5-127626. In this conventional method, a backlight circuit including a backlight 8, a brightness control unit 12, and a backlight drive unit 13, a display control unit 14, and an LCD drive unit 1
5 and an LCD display unit 16 comprising:
It comprises a synchronizing unit 17 that extracts an LCD driving cycle from the CD drive unit 15 and sends out a synchronizing signal to the luminance control unit 12.

[0005] The LCD display section 16 performs character display. At this time, the LCD drive section 15 alternately drives the individual display elements of the LCD display section 16 at regular intervals to perform dynamic display. On the other hand, the synchronization unit 17
Extracts the LCD drive cycle from the LCD drive unit 15,
The synchronization signal is sent to the brightness control unit 12. Brightness control unit 12
Controls the backlight drive unit 13 so that the backlight 8 is intermittently turned on, and adjusts the brightness of the backlight 8 by changing the duty of turning on and off in the intermittent lighting.

When adjusting the brightness of the backlight 8, the display drive cycle of the LCD drive section 15 and the intermittent lighting cycle of the backlight 8 are synchronized by a synchronization signal from the synchronization section 17. Thus, the duty of the pulse for luminance control can be changed synchronously within the display timing of each segment, and the luminance of each segment can be uniformly adjusted.

FIG. 4 is a block diagram showing another example of the conventional backlight control system. This conventional backlight control system and liquid crystal display device are the control system described in Japanese Patent Application Laid-Open No. 3-198,026, and store a central processing unit (CPU) 20 for controlling the operation of the system, an operation program of the CPU 20, and the like. Read only memory (ROM) 2
1. Random access memory (RAM) 22 for reading and writing data, display signal generation unit 23 for generating a display signal, display memory 24 for storing data for display,
Backlight control register 25, switch 26, power supply 2
And controls the backlight 8 that illuminates the LCD panel 28 from behind.

[0008] The backlights 8 are arranged in parallel in the horizontal direction.
4 (two shaded areas and one shaded area in FIG. 4), the central area of which is directly connected to the terminal of the power supply 27 and the two shaded areas at both ends. Is connected to the terminal of the power supply 27 via the switch 26. As a result, the central region and the regions at both ends of the backlight 8 are individually flashed and adjusted in luminance, so that only a portion necessary for display can be turned on.

In this conventional method, the CPU 20 determines the display mode of display data and the presence or absence of display data on the screen of the LCD panel 28 corresponding to each divided area of the backlight 8.
The backlight 8 is controlled by setting it in the backlight control register 25 and blinking or changing the brightness for each divided area of the backlight 8. That is, by turning off or lowering the brightness of the divided areas of the backlight 8 that are not used for display and the divided areas of the backlight 8 that correspond to portions where no display data exists on the screen, according to the set display mode. The backlight 8 is controlled. As a result, the backlight 8 corresponding to an area where illumination is unnecessary, that is, a part where there is no display is provided.
The power consumption can be reduced by turning off or turning off the low brightness of the divided areas.

[0010]

However, in the conventional backlight control system and the liquid crystal display device, the system for realizing the uniformity of the illuminating surface by using a cathode tube and a light diffusion plate (or a light guide plate) has been proposed. In the case of a backlight that requires a large screen or high brightness, the method of placing the cathode tube directly under the light diffusion plate is generally used. In some cases, the distance from the cathode-ray tube position to the light diffusion plate cannot be made physically the same, so the light propagation distance differs and the luminance differs. There will be a difference.

Among the conventional backlight control system and liquid crystal display device, the backlight control system and the liquid crystal display device having the configuration shown in FIG. 3 are effective for a small display such as a segment display. In a display device that performs graphic display, the number of pixels is large, the synchronization signal has a considerably high frequency, it is not realistic, and a flat light emitting plate corresponding to each pixel or block is required to secure the luminance uniformity effect. However, since it is difficult to realize a high-luminance and large-sized screen, it is difficult to apply it to a high-luminance and large-screen backlight.

Further, among the conventional backlight control system and liquid crystal display device, in the backlight control system and the liquid crystal display device having the configuration shown in FIG. 4, it is necessary to divide the backlight 8 into regions, and these luminances are reduced. It is difficult to make it constant, and a flat light emitting plate corresponding to each pixel or block is required to secure the luminance uniformity effect, as in the conventional method of FIG. Since it is difficult to realize a large-sized one, it is difficult to apply it to a high-luminance backlight for a large screen.

The present invention has been made in view of the above points,
It is an object of the present invention to provide a backlight control method and a liquid crystal display device that can improve the uniformity of luminance.

Another object of the present invention is to provide a backlight control system and a liquid crystal display device which can be applied to a backlight for a large screen with high luminance.

[0015]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a die for controlling the brightness of the light emission side surface of a light diffusion plate of a backlight comprising a plurality of light sources and a light diffusion plate.
A backlight control method for a liquid crystal display panel, wherein a luminance calculated in advance based on data of a correlation between a scanning position of a scanning line on a liquid crystal display surface and luminance unevenness of an irradiation surface on a light emission side surface of a light diffusion plate. Storage means for storing a brightness control value for ensuring uniformity of the display, detection means for detecting a scanning position on a liquid crystal panel of a dynamic display illuminated by a backlight, and a scanning position detected by the detection means. And a control means for controlling the brightness of the plurality of light sources independently for one scanning time or for a plurality of scanning times according to the brightness control value read from the storage means.

According to the present invention, the luminance control value calculated and stored in the storage means is read out according to the scanning position to control the luminance of the backlight. You can control the brightness of the light.

Further, in order to achieve the above object, the liquid crystal display device of the present invention provides a dynamic display of a backlight.
In a liquid crystal display device that irradiates the liquid crystal panel and displays desired display data on the liquid crystal panel, a plurality of light sources whose luminance of emitted light is independently controlled by a control signal from the outside, and a plurality of light sources Dyna by diffusing the light
The difference between the light diffusing plate that illuminates the back of the liquid crystal panel for mic display as a backlight, the distance from multiple light sources to the light diffusing plate, and the incident angle between the scanning position of the scanning line on the liquid crystal panel for dynamic display . results, obtains a luminance difference on the liquid crystal panel side surface of the dynamic display of the light diffusion plate, a storage means for storing the luminance control values for ensuring the uniformity of brightness in each scanning line on the basis of the brightness difference, Dyna
Detecting means for detecting the scanning position of the scanning signal on the liquid crystal panel of the mic display, and the luminances of the plurality of light sources, respectively, according to the luminance control value read from the storage means according to the scanning position detected by the detecting means. And a control means for controlling independently.

According to the present invention, in a backlight liquid crystal display device requiring a large screen or high luminance in which a plurality of light sources are placed immediately below a light diffusing plate, the distance from the plurality of light sources to the light diffusing plate and the Light diffuser liquid crystal panel caused by the difference between the scan line and the incident angle related to the scan position
The brightness of the plurality of light sources can be controlled so as to correct the brightness difference on the side surface .

[0019]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing one embodiment of a backlight control system and a liquid crystal display device according to the present invention. As shown in FIG. 1, this embodiment has a CPU 1 that controls reading of a brightness control value and setting of the control value.
A ROM 2 storing a brightness control value and a control program calculated in advance, a scanning position detecting unit 3 for detecting a scanning position of the LCD, and a scanning signal generating unit 4 for generating a scanning signal for controlling the LCD display. A brightness control value register 5 for sequentially setting a brightness control value selected according to the scanning line;
A brightness control generation unit 6 for reading a control value from the brightness control value register 5 and generating a control signal therefrom; a backlight brightness adjustment unit 7 for generating a signal for directly controlling the backlight brightness from the brightness control signal; It is composed of

The backlight 8 is, as shown in FIG.
A light diffusion plate 10 disposed directly below (back side) an LCD panel 9 of the liquid crystal display device;
It comprises a plurality of cathode tubes 11 illuminating the back surface of the panel 9.
In this embodiment, a backlight illuminating surface caused by a difference between a distance from the cathode tube 11 to the light diffusion plate 10 and an incident angle from the cathode tube 11 to a scanning position on the LCD panel 9 .
That is, the surface of the light diffusion plate 10 on the LCD panel 9 side (hereinafter, referred to as the “light diffusion plate 10”).
The luminance difference on the illumination surface is simply eliminated by sequentially changing the luminance of the cathode tube 11, and the luminance of the illumination surface is made uniform.

Here, the brightness control value for brightness correction is determined by the distance between the cathode tube 11 and the light diffusion plate 10 and the difference in the angle of incidence from the cathode tube 11 to the scanning position on the LCD panel 9 on the illumination surface. The luminance difference is calculated for each individual cathode tube 11 and for each scanning line in advance or measured by a known method, and a luminance control value for correcting the luminance based on the calculated difference is calculated for each cathode tube 11 and for each scanning line. The obtained value is stored in the ROM 2.

Next, the operation of this embodiment will be described. The LCD sequentially updates display data by a conventionally known configuration (not shown) and displays a desired image on the LCD panel 9. A scanning signal for controlling the LCD panel 9 is generated by the scanning signal generator 4. Is done.

This scanning signal is taken in by the scanning position detecting section 3, where the scanning position (position on the LCD screen) to be updated is detected. The CPU 1 captures the scanning position detected by the scanning position detecting unit 3, reads a corresponding luminance control value from the ROM 2 according to the detected scanning position, and sets the luminance control value in the luminance control value register 5.

The brightness control generator 6 receives the scanning signal generated by the scanning signal generator 4 and reads the brightness control value from the brightness control value register 5 at a timing based on the scanning signal. The backlight brightness adjustment unit 7 generates a signal for adjusting the brightness of the cathode tube of the backlight 8 based on the brightness control value input from the brightness control generation unit 6, and outputs the signal to the cathode tube constituting the backlight 8. To supply. The cathode tube is 1
In the case where there are a plurality of tubes as indicated by 1, each cathode tube 11
To control the brightness of the light emitted from them for one scanning time or a plurality of scanning times independently of each other.

Thus, on the illumination surface of the backlight 8, the brightness of the backlight is variably controlled according to the position of the scanning line on the LCD screen. Here, as described above, the brightness control value calculates or measures the brightness difference on the illumination surface caused by the difference between the distance from the cathode tube 11 to the light diffusion plate 10 and the angle of incidence, and corrects the brightness based on this. since the value is a value determined for each scan line, serves to increase the brightness when the position lower normal brightness (e.g., such as the middle of the cathode tube 11 adjacent) the scanning line passes, the light diffusion plate 10 LC
The brightness corresponding to each scanning line on the surface of the D panel 9 is substantially uniform.
LCDs for displaying images with uniform brightness
The brightness of each scanning line on the screen can be made substantially uniform.

It should be noted that the position where the luminance is low is usually kept as it is,
It is also possible to make the luminance on the LCD screen uniform by lowering the luminance at a position where the luminance is high. Further, the present invention is not limited to the above-described embodiment. For example, other light sources such as electroluminescence (EL) can be used instead of the cathode tube 11. Furthermore, in principle, the number of light sources can be one.

[0027]

As described above, according to the present invention,
The brightness control value calculated and stored in the storage means in advance,
By controlling the brightness of the backlight is read according to the scanning position, which is adapted to control the brightness of the backlight in accordance with the scanning position, at the time of image display of uniform brightness L
The brightness of each scanning line on the CD display screen can be made substantially uniform.

Further, according to the present invention, in a backlight liquid crystal display device requiring a large screen or high luminance in which a plurality of light sources are placed immediately below a light diffusion plate, the distance from the plurality of light sources to the light diffusion plate is reduced. And, since the brightness of a plurality of light sources is controlled so as to correct the difference in incidence brightness to the light diffusion plate caused by the difference between the angle of incidence of the scanning line on the scanning position and the scanning position in the liquid crystal panel, the cathode tube is used as the light source. It is possible to correct uneven brightness of the directly installed backlight used.

[Brief description of the drawings]

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

FIG. 2 is an explanatory view of the arrangement of the backlight in FIG. 1;

FIG. 3 is a block diagram of an example of the related art.

FIG. 4 is a block diagram of another example of the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Central processing unit (CPU) 2 Read-only memory (ROM) 3 Scan position detection part 4 Scan signal generation part 5 Brightness control value register 6 Brightness control generation part 7 Backlight luminance adjustment part 8 Backlight 9 LCD panel 10 Light Diffusion plate 11 Cathode tube

Claims (2)

(57) [Claims] 1. A backlight comprising a plurality of light sources and a light diffusing plate for controlling the brightness of the light emitting side surface of the light diffusing plate.
A backlight control method for a dynamic display liquid crystal panel , which is calculated in advance based on data of a correlation between a scanning position of a scanning line on a liquid crystal display surface and luminance unevenness of an irradiation surface on a light emission side surface of the light diffusion plate. Storage means for storing a brightness control value for ensuring brightness uniformity; and a dynamic table illuminated by the backlight.
Detecting means for detecting a scanning position in the liquid crystal panel shown in the following , independently of the luminance of the plurality of light sources according to the luminance control value read from the storage means according to the scanning position detected by the detecting means, Control means for controlling for one scanning time or a plurality of scanning times.
Backlight control method for dynamic display liquid crystal panel . 2. A liquid crystal display device which irradiates a backlight to a liquid crystal panel of dynamic display and displays desired display data on the liquid crystal panel, wherein the brightness of emitted light is controlled independently of each other by a control signal from the outside. A plurality of light sources, and the dynamic table by diffusing light from the plurality of light sources.
It indicates a light diffusion plate for illuminating as the backlight behind the liquid crystal panel, the distance from the plurality of light sources to the light diffusion plate and the da
A luminance difference on a liquid crystal panel side surface of the dynamic display of the light diffusion plate, which is caused by a difference between an incident angle and a scanning position of a scanning line in the liquid crystal panel of the dynamic display, is determined. Storage means for storing, for each scanning line, a brightness control value for ensuring the uniformity of the scanning, detecting means for detecting a scanning position of a scanning signal on the liquid crystal panel for dynamic display, and scanning detected by the detecting means. A liquid crystal display device comprising: control means for controlling the brightness of each of the plurality of light sources independently of each other in accordance with the brightness control value read from the storage means in accordance with a position.