JPH07129113A - Display device for adjusting display brightness - Google Patents

Abstract

(57) [Abstract] [Purpose] An adjusting means is provided for maintaining and adjusting the brightness displayed on the display screen of the display device. [Composition] A display device for adjusting display brightness, wherein a display screen 1 for displaying an image and the overall brightness of the display screen 1 based on the number of pixels of the display screen 1 displayed in white of the displayed image. And a dimming circuit 6 that responds to the white pixel counter 4 and that maintains and adjusts the brightness displayed on the display screen 1 to a constant value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device such as a CRT, an EL display, a liquid crystal display device (LCD) with a backlight, which itself is a light emitting source or which is accompanied by an illumination light source.

[0002]

2. Description of the Related Art As a means for automatically adjusting display brightness, there is known a method of detecting ambient brightness and display brightness by an optical sensor and adjusting light based on such information.

The invention of Japanese Patent Laid-Open No. 63-94228 detects the brightness of the surroundings and adjusts the brightness accordingly. FIG. 6 is a conceptual diagram thereof. When the surroundings are brighter than the standard usage environment, the display brightness is adjusted to be high, and when the surroundings are dark, the display brightness is adjusted to be low.

The invention of Japanese Patent Application Laid-Open No. 3-296717 is a system in which the brightness of the display surface is detected and fed back to the brightness control circuit. FIG. 7 is a conceptual diagram thereof. This is originally LCD
However, it is suggested that the invention can be applied to automatic adjustment of backlight brightness.

[0005]

The apparent display brightness also depends on the display content. Specifically, when there are many white parts (light emitting parts, in the LCD with a backlight, the part that transmits the illumination light) in the display content, the brightness of the entire display screen increases, and conversely, when there are few white parts in the display content, The brightness of the entire screen is low. Since the above-described conventional brightness adjustment technique does not take this point into consideration, the adjusted brightness does not always match the value considered to be proper.

The present invention has been made in consideration of such circumstances, and the area of the white portion of the display pattern is detected and fed back to the brightness adjusting circuit, so that the display brightness is kept constant with respect to the change of the display content. The purpose is to keep. The present invention makes it possible to obtain optimum display brightness.

[0007]

According to the first aspect of the present invention, a display screen for displaying an image and a white screen for the displayed image are displayed. A calculation unit that calculates the brightness of the entire display screen based on the number of pixels of the display screen; and an adjustment unit that responds to the calculation unit and that maintains the brightness displayed on the display screen at a constant level. It is a display device that adjusts the characteristic display brightness.

According to the invention of claim 3, a display screen for displaying an image, a detecting means for detecting the brightness around the display screen and the display brightness of the display screen, and a response to the detecting means, A display device for adjusting display brightness, comprising an adjusting unit for adjusting display brightness and contrast of the display screen to optimum values.

[0009]

According to the present invention, there is provided means for calculating the brightness of the entire screen from the number of pixels displayed in white of the display image and adjusting the brightness of the display to be constant based on the calculated brightness. Further, in addition to the above-mentioned means, a means for detecting the ambient brightness and the brightness of the display surface by an optical sensor and setting the display brightness and the contrast to optimum values based on these information is provided.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the embodiments shown in the drawings. The present invention is not limited to this.

As a method of realizing the present invention, when the display brightness is kept constant, the apparent brightness of the screen is a white part on the screen (a light emitting part, or a transmissive part of illumination light in a backlit LCD). The area becomes higher in proportion to the area (number of white pixels). Figure 1 shows the relationship between the number of white pixels and the screen brightness.
Is shown in the graph. The horizontal axis in FIG. 1 represents the ratio of the number of white pixels to the total number of pixels (0% to 100%). In order to suppress the fluctuation of the display brightness due to such display contents, a means for correcting the brightness according to the number of white pixels is provided. An example of the characteristic of the brightness correction is shown in FIG. The brightness is corrected in inverse proportion to the number of white pixels, and the display brightness becomes constant regardless of the number of white pixels as shown in FIG. However, when the white portion in the display is extremely small and the display area is close to pure black, the brightness correction is not performed (area A in FIGS. 2 and 3). This is because if the brightness is increased too much, the white part becomes too dazzling, the black display part becomes brighter, etc. Similarly, even in the case of a display in which the number of white portions is extremely large and close to true white (area C in FIG. 2 and FIG. 3), if the brightness is lowered too much, the white display portion becomes dark and the contrast deteriorates, making it difficult to see. There is.

First Embodiment An embodiment of a backlit LCD of the present invention will be described.
FIG. 4 shows a first embodiment of the present invention. The display process in this embodiment is as follows. Reference numeral 1 is an LCD, and 2 is a backlight light source.

Based on the image data stored in the VRAM (3, the LCD driver 7 turns ON / OFF each pixel of the LCD 1.
To display an image on the LCD. The LCD driver 7 also controls the drive voltage of the LCD 1 to adjust the display contrast, but the adjustment value is manually set by the user (adjustment operation manual such as a volume is provided).

Lighting and dimming of the backlight is performed by the following process.

The dimming circuit 6 can change the brightness of the backlight light source 2 by changing the power supply voltage or the drive duty of the backlight light source 2. The brightness is set manually by the user (adjustment operation means such as a volume is provided).

On the other hand, the actual brightness setting value is corrected depending on the display content. It is the white pixel counter 4 and the correction value generation logic 5 that give this correction value to the dimming circuit 6. The white pixel counter 4 counts the total number of pixels displayed in white in the entire screen from the image data from the VRAM 3, and the correction value generation logic 5 generates a correction value based on the number of white display pixels (see FIG. 2).
Has a characteristic table of the number of white pixels vs. brightness correction value,
The brightness correction signal is output to the dimming circuit 6. The white pixel counter 4 obtains a synchronizing signal from the LCD driver 7 so that the count value can be reset and updated for each frame of screen display.

Second Embodiment FIG. 5 is a block diagram of a second embodiment of the present invention. This is an embodiment in which the display brightness / contrast can be completely automatically controlled by combining the present invention with the brightness / contrast control based on the ambient light or the display brightness, which is a conventional technique. The display process in this embodiment is as follows.

The LCD driver 7 turns ON / OFF each pixel of the LCD 1 based on the image data stored in the VRAM (3).
To display an image on the LCD. The LCD driver 7 also controls the drive voltage of the LCD 1 to adjust the display contrast. The adjustment value is set based on the display brightness detected by the first optical sensor 9. The portion of the LCD facing the sensor is not used for display, and is switched to white display and black display alternately at regular intervals. The brightness information of white display and black display detected by the optical sensor 9 is separated by the multiplexer 10 and transmitted to the contrast control logic 11.
The contrast control logic 11 outputs a contrast control signal to the LCD driver 7 based on the brightness information. The control is performed according to the following policy.

(1) When the brightness of white display is lower than a predetermined threshold value, the drive voltage is lowered to increase the transmittance of the LCD. (2) When the brightness of black display is higher than the predetermined threshold value, the drive voltage is raised to LCD. (3) In other cases, the drive voltage is not changed.

Since the contrast is controlled by the contrast control logic 11, no user manual adjustment means is provided. Lighting and dimming of the backlight is the following process.

The dimming circuit 6 can change the brightness of the backlight light source 2 by changing the power supply voltage or the drive duty of the backlight light source 2, and the brightness of the white display of the LCD (the first light sensor 9). The brightness of the backlight is controlled so that the value detected in step S1 and separated by the multiplexer 10) is kept constant.

Further, the brightness of the surroundings is detected by the second photosensor 8, and the brightness of the backlight is corrected in proportion to the brightness of the surroundings. When the surroundings are bright, the display is bright and when the surroundings are dark, Darken the display.

On the other hand, the actual brightness setting value is corrected depending on the display content. It is the white pixel counter 4 and the correction value generation logic 5 that give this correction value to the dimming circuit 6. The white pixel counter 4 counts the total number of pixels displayed in white in the entire screen from the image data from the VRAM 3, and the correction value generation logic 5 generates a correction value based on the number of white display pixels (see FIG. 2).
Has a characteristic table of the number of white pixels vs. brightness correction value,
The brightness correction signal is output to the dimming circuit 6. The white pixel counter 4 obtains a synchronizing signal from the LCD driver 7 so that the count value can be reset and updated for each frame of screen display.

Since the display brightness is automatically adjusted by the above means, no manual adjustment means by the user is provided.

[0025]

According to the present invention, the area of the white portion of the display pattern is detected and fed back to the brightness adjusting circuit, so that the display brightness can be kept constant with respect to changes in the display content. The present invention makes it possible to obtain optimum display brightness.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between the number of white pixels and screen brightness in a display device according to an embodiment of the present invention.

FIG. 2 is a graph showing a characteristic of correcting brightness according to the number of white pixels in a display device according to an exemplary embodiment of the present invention.

FIG. 3 is a graph showing the brightness of a screen in which the brightness is corrected by the number of white pixels in the display device according to the embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a display device according to a first exemplary embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of a display device according to a second exemplary embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of a conventional display device.

FIG. 7 is a block diagram showing a configuration of a conventional display device.

[Explanation of symbols]

 1 Liquid Crystal Display Device 2 Backlight Light Source 3 VRAM 4 White Pixel Counter 5 Correction Value Generation Logic 6 Light Control Circuit 7 Liquid Crystal Display Device Driver 8 Second Optical Sensor 9 First Optical Sensor 10 Multiplexer 11 Contrast Control Logic

Claims (5)

[Claims] 1. A display screen for displaying an image, calculating means for calculating the brightness of the entire display screen based on the number of pixels of the display screen, which is displayed in white of the displayed image, and the calculation. A display device for adjusting display brightness, which comprises an adjusting device for adjusting the brightness displayed on the display screen in response to the device. 2. The display device for adjusting display brightness according to claim 1, wherein the display screen is a liquid crystal display device. 3. A display screen for displaying an image, a detection means for detecting the brightness around the display screen and a display brightness of the display screen, and a display brightness and a contrast of the display screen in response to the detection means. A display device for adjusting display brightness, comprising: an adjusting unit for adjusting the display value to an optimum value. 4. When the display screen is composed of a liquid crystal display device and the display brightness of a portion displayed in white on the display screen is lower than a predetermined threshold value, the drive voltage of the liquid crystal display device is lowered and the liquid crystal display device is lowered. The display device for adjusting display brightness according to claim 3, further comprising means for reducing the transmittance of the display device. 5. The display screen is composed of a liquid crystal display device, and when the display brightness of a portion displayed in black on the display screen is higher than a predetermined threshold value, the drive voltage of the liquid crystal display device is increased. The display device for adjusting display brightness according to claim 3, further comprising means for increasing the transmittance of the display device.