WO2013166680A1

WO2013166680A1 - Regional backlight control method for edge light guide and backlight device

Info

Publication number: WO2013166680A1
Application number: PCT/CN2012/075282
Authority: WO
Inventors: 刘丽丽; 田翠翠; 邢文峰
Original assignee: 青岛海信信芯科技有限公司
Priority date: 2012-05-10
Filing date: 2012-05-10
Publication date: 2013-11-14
Also published as: WO2013166994A1

Abstract

A backlight device, comprising a backlight light source group (1), a liquid crystal panel (2) for displaying a video image, a PWM control circuit for controlling a backlight source to emit light, a circuit for determining a backlight value and a backlight compensation value, a video converter, a backlight compensation circuit and a liquid crystal control circuit. The video converter converts an input video to obtain video image data required to be processed; the circuit control determining a backlight value and a backlight compensation value processes the video image data to obtain a backlight value and a backlight compensation value of each division region of the video; the PWM control circuit modulates the backlight lamp group of each division region on the backlight light source group (1) according to the backlight value, and lightens the liquid crystal panel (2); the backlight compensation circuit sends a backlight compensation signal according to the backlight compensation value; and the liquid crystal control circuit receives the backlight compensation signal, compensates the video image data, and then transmits same to the liquid crystal panel (2) for display. The backlight device determines the backlight source brightness according to a regional image content to be displayed, and modulates an LCD control signal, and the power consumption is effectively saved and the contrast is improved on the premise of maintaining the image brightness.

Description

Area backlight control method for side light guide and backlight device

Technical field

The present invention relates to the field of backlight liquid crystal panel display, and more particularly to an area backlight control method and a backlight device for side light guiding.

Background technique

Liquid crystal display (LCD) is widely used in consumer electronics due to its low power consumption, light weight, and thin thickness. Since the liquid crystal panel itself does not have the illuminating property, it is necessary to add a uniform backlight to the transmissive LCD panel to achieve the effect of displaying the dynamic scene image through the transmittance modulation of the liquid crystal cell.

Backlight dimming technology (also known as backlight area control technology) is a new technology developed in recent years to improve the dynamic range of LCD imaging contrast, using non-uniform backlight area control technology, that is, by adjusting different areas of the backlight Brightness, improved imaging contrast, enabling high dynamic range liquid crystal display.

In current applications such as televisions, computer monitors, and handheld electronic devices, backlights are mostly a uniform and constant light output, ie, 0D dynamic backlight adjustment, which is based on the overall brightness of the image, backlighting the entire backlight area. 0 dimension adjustment of brightness. In order to produce good visibility in higher ambient light, the backlight must have higher brightness, resulting in high power consumption and overheating of the liquid crystal device, and at the same time, because the transmittance of the liquid crystal cell is difficult to control to 0, when When the pixel is in a darker gray level, the backlight that is fully lit will leak light through the LCD panel, causing the dark area to be not a completely dark performance, resulting in a disadvantage of low contrast.

The current direct dynamic backlight control is 2D dynamic backlight adjustment. The 2D dynamic backlight adjustment divides the entire backlight area into a plurality of horizontal and vertical partitions, and performs independent on each partition according to the brightness of the image signal in the partition. 2-dimensional adjustment of the brightness of the partition backlight. This adjustment method can produce high contrast, but since the direct-lit backlight requires many LED lamps to be distributed behind the LCD panel, this causes the LCD panel to be too thick, and the power consumption is too high, and the liquid crystal is overheated. In order to reduce power consumption, the side-lit backlight, that is, the 1D backlight, has become a trend in the development of regional backlight control.

Summary of the invention

In view of the above problems, an object of the present invention is to provide an area backlight control method for side light guiding, which calculates input video image content characteristics according to different side light partitions, determines backlight values and backlight compensation values of different areas, and performs area backlight adjustment. Display images with high dynamics to achieve energy savings.

To achieve the above object, an area backlight control method for side light guiding according to the present invention includes the following steps:

Obtaining a backlight value of each divided region according to a pixel brightness value in each divided region;

Obtaining a backlight compensation value for each divided region according to the backlight value; performing the threshold value processing on the obtained backlight value, and transmitting the backlight value to the backlight control circuit to drive the backlight source;

The obtained backlight compensation value is compensated and processed:

If the image needs to be compensated, the light diffusion coefficient formed by the backlight compensation signal is obtained, image compensation is performed point by point, and then sent to the display panel for display;

Otherwise, the image data is displayed directly on the display panel.

Preferably, the method for determining the backlight value is specifically:

Calculate the maximum value of the RGB channel of each pixel of the input image, and use the maximum value as the brightness value of the pixel to obtain the maximum value and average value of the pixel brightness in each divided area;

According to the maximum value and the average value of the pixel brightness in each of the divided regions, the backlight value of the divided region is obtained by processing in a preset backlight value calculation manner. Preferably, the method for determining the backlight compensation value is specifically:

According to the backlight value of each divided area, the average value of the backlight brightness of the entire area is obtained by processing in a preset backlight average calculation manner;

According to the backlight value and the average value of each divided area, the preset backlight variance calculation method is used to obtain the variance of the backlight brightness of the entire area;

According to the above-mentioned average value and the condition set by the variance, the backlight compensation value calculation method is used to calculate the backlight compensation value of each divided area;

Preferably, the preset backlight value is calculated as:

BL'=Local _avg + f {Local _avg , Local _max ) where is the area backlight value, oo// _flVg is the average brightness of the area backlight value, j Local _avg , 00//„^) is the maximum value of the area pixel brightness And a function of the average value. Preferably, the preset backlight value calculation method is limited by a threshold: 2., if BU > T _m

VLocal _avg

Else where, in order to define the backlight value of the back area, oo// _flVg is the average brightness of the area backlight value, JXLoca g, Local _max ) is a function of the maximum value and the average value of the brightness of the area pixel, which is the upper limit of the threshold. Preferably, the preset backlight average calculation method is:

Where ^ is the average of the backlight brightness of the entire area, &L' (0 is the first

The backlight value of (i=l, 2, ..., N) regions; The preset backlight variance calculation method is:

Where SL^ is the backlight variance, ^ is the average value of the backlight luminance of the entire region ^L'(z) is the backlight value of the i-th (i=l, 2, ..., Ν) regions. Preferably, the preset backlight compensation value is calculated as:

Where BL (ΐ) is the backlight compensation value of the i-th (i=l, 2, ..., Ν) region, and ^L'(z) is the i-th (i=l, 2, .. .... , Ν) The unrestricted backlight value of each area is the maximum value of one backlight value, /^ is one backlight

The variance of the value, _w is the variance threshold, which is the average of the backlight values, and ^Tav s is the mean threshold.

Preferably, the input image is a video image, and the backlight value and the backlight compensation value obtained by the previous frame image of the video are used for backlight control and backlight compensation of the current frame image, and the backlight value and the backlight compensation value obtained by the current frame image are used. Backlight control and backlight compensation for the next frame of image.

Preferably, the video image is played 30 frames or 25 frames per second.

In order to achieve the above object, a backlight device according to the present invention includes a backlight source group 1, a liquid crystal panel displaying a video image, a PWM control circuit for controlling backlight illumination, a backlight value and a backlight compensation value circuit, a video converter, a backlight compensation circuit and a liquid crystal control circuit, wherein

Video converter that converts the input video to get a video map that needs to be processed Like data;

Determining the backlight value and the backlight compensation value circuit, processing the video image data to obtain the backlight value and the backlight compensation value of each divided region of the video;

a PWM control circuit that modulates a backlight group of each divided area on the backlight source group according to a backlight value to illuminate the liquid crystal panel;

The backlight compensation circuit sends a backlight compensation signal according to the backlight compensation value; the liquid crystal control circuit receives the backlight compensation signal to compensate the video image data, and then sends the image to the liquid crystal panel for display.

Preferably, the backlight source group is a backlight source group of a single side or a double side of the liquid crystal panel.

The beneficial effects of the invention are:

The invention calculates the content characteristics of the input video image according to the side light guiding partitions, determines the backlight brightness and the backlight compensation brightness in different partition regions, thereby performing regional backlight adjustment to display images with high dynamics, thereby achieving the purpose of energy saving. The device fabrication of the present invention reduces the SOC (system-on-chip) chip area, reduces the display volume, saves power consumption, and improves the contrast of the display.

DRAWINGS

1 is a simplified diagram of a structure of a backlight device according to an embodiment of the present invention; FIG. 2 is a flowchart of processing of a backlight device according to an embodiment of the present invention; FIG. 3 is a flowchart of timing control in a case of different frames according to an embodiment of the present invention; 4 is a schematic view of the backlight value processing of the present invention.

detailed description

The invention will be further described below in conjunction with the drawings.

The LED backlight area control technology can separately control each partition separately, and its lighting intensity can be determined by many typical values, such as the maximum brightness value of the image data in the partition, the average brightness value of the image data in the partition, and the like. . The backlight value method is determined by using the maximum brightness value of the image data, and the distortion rate of the image is low, but the figure The noise of the image is easy to cause the problem of flicker of the backlight, especially in the case where the quantization error of the low gray level is relatively large; while the average method loses part of the image detail, and the image is too dark in a very dark image, and the visual distortion is serious. The invention combines the maximum value and the average value two typical value methods, and utilizes the advantages of the two methods to determine the backlight value and the backlight compensation value, performs area control on the backlight, compensates the image at the same time, and adjusts the image caused by the dimmed backlight. Darken to achieve energy savings and contrast enhancement.

To this end, an embodiment of the present invention provides an area backlight control method for side light guiding, which includes the following steps:

The backlight value of the divided area is obtained according to the maximum value and the average value of the pixel brightness in each of the divided areas, and the backlight value of the divided area is processed according to the backlight value of each divided area. Obtaining an average value of the backlight brightness of the entire area; processing according to the backlight value and the average value of each divided area in a preset backlight variance calculation manner to obtain a variance of the backlight brightness of the entire area;

And performing the threshold value limiting process on the obtained backlight value to be sent to the backlight control circuit to drive the backlight source;

The obtained backlight compensation value is compensated and processed:

Otherwise, the image data is displayed directly on the display panel.

The maximum value and average of the input image segmentation region are used in the embodiment of the present invention. The value is used to determine the backlight factor, and the algorithm has a small complexity and is well adapted to various input images. First, calculate the maximum value of each pixel RGB channel, use the maximum value to represent the luminance value of this pixel, and then calculate the maximum value and average value of the luminance value of each divided region, and then use the algorithm formula (1) to determine the backlight value. .

BL' = Local + /(Local Local _maii )

At the same time, according to the degree of insensitivity of the human eye to the high-intensity image, the backlight value is defined, and the entire backlight value is determined as equation (2).

Where BL is the backlight brightness output to the backlight control circuit, L _{OC avg} is the average brightness of each segment of the yoga image, f (Local _avg , Local 丽, is a function of the maximum and average values of the regional pixel brightness, f (L _OCa l _avg , L _OC al dish function corrects the backlight of the whole area. When the hour indicates that the brightness of the whole area is small, the correction value increases little. When it is large, the brightness of the whole area is high, and the correction value increases. Fast, to improve the backlight brightness of the entire area. When BL is higher than the upper limit of the threshold Tm, set BL to Tm. The backlight value is determined as shown in Figure 4, where max represents the curve of the backlight value with the maximum value of the entire region (Figure The upper middle line), and BL is the last formed backlight value curve (the lower line in the figure).

When the N backlight brightness of the entire image is determined, the average value and variance of the N backlight luminances are calculated according to the undefined BL calculation formula (1), and the average value of the N backlight luminances is calculated as (3)

(3)

The variance calculation formula is (4)

(4)

In order to implement no additional computational complexity in hardware implementation, modify the formula

(4), using the mean instead of the variance, then the formula (4) is modified to the formula (5)

(5)

When the mean and variance are obtained, the backlight compensation is calculated according to the set conditions. The judgment formula is (6)

BL\i)+BL _{max N}

BL _com (/): 2 1 else where S4. _m (0 is the backlight compensation value of the i-th (i=l, 2, ..., N) region, '(0 is the undefined backlight value of the first region, and BL is N backlights) The maximum value is the variance of N backlight values, r _w is the variance threshold, BL _avg is the average of N backlight values, r _avg mean value, and the backlight compensation value is the current partition when the above compensation condition is satisfied. The average value of the sum of the backlight value and the maximum value of the N backlight values of the current frame. The compensation value is determined based on when the whole image is very dark overall, but when there is a certain area, the variance is large, and as long as the darkness is dark Regional The backlight is turned down, and the contrast of the entire image is improved. According to the visual characteristics of the human eye, no compensation is required, and the image seen on the LCD screen is also bright, so no compensation is made to prevent excessive compensation. When the limitation of „ and ^ is not met, the backlight compensation value is 1, that is, the image is not compensated, and when the backlight compensation value is too low, in order to prevent over-compensation, the minimum threshold is set to compensate. The final backlight compensation value For equation (7), where 3⁄44. _m is the lowest threshold of the backlight compensation value.

It should be noted that, when the project is implemented, the embodiment of the present invention divides the backlight value and the backlight compensation value into M (M=2 ⁿ , n=0, 1 , 2, ... 8 ) levels to reduce The complexity of the backlight control circuit, especially when M=0, means 0D backlight, that is, all the backlight values have only one, and when M=256, the control precision of the backlight value can be accurate to each gray level of the brightness value. Level, when the backlight value changes by one gray level, the backlight control circuit will make a change. It can be set according to the required accuracy when it is implemented.

As shown in FIG. 1 , in combination with the above method, a backlight device according to an embodiment of the present invention includes a backlight source group placed on one side or both sides of a liquid crystal display panel, a liquid crystal panel displaying video images, and control. a backlight control PWM control circuit, a backlight value and a backlight compensation value circuit, a video converter, a backlight compensation circuit, and a liquid crystal control circuit, wherein

a video converter that converts the input video to obtain video image data to be processed;

PWM control circuit, modulating each segmentation on the backlight source group according to the backlight value a backlight group in the area, illuminating the liquid crystal panel;

As shown in Figure 2, the specific processing flow is:

According to the pixel value input point by point, the backlight value of the segment area is determined, and the widened value is limited and output to the PWM control circuit to perform LED driving control, illuminate the backlight LED unit, and illuminate the LCD screen. At the same time, according to the backlight value, the backlight compensation value is output to the backlight compensation signal circuit, and the backlight compensation signal circuit determines whether the image is compensated. If the image does not need compensation, a backlight compensation signal is issued, and the signal is defined as a value of 1, therefore, when the backlight is compensated If the signal is 1, the image data is directly output to the LCD screen for image display; if not, the backlight compensation signal value is input to the light diffusion model to obtain the light diffusion coefficient formed by the backlight compensation signal, and then the image is imaged point by point. After compensation, output to the LCD screen for display.

Embodiments of the present invention are applied to video image playback. According to the characteristics of the video, if 30 frames (PAL system) or 25 frames (NTSC system) are played every second, the correlation between the two frames is very strong. In order to process each pixel of each frame in real time, no additional extra is added. The memory increases the chip area. As shown in FIG. 3, when the device of the present invention plays an image, the backlight of the previous frame is used to control the current frame, and the backlight value and the backlight compensation value calculated by the pixels of the current frame are used for backlight control of the next frame. And backlight compensation, does not need to RAM or ROM storage of the entire block area, thus forming flow control in turn, to achieve small-area high-speed operation of the chip.

The scheme determines the brightness of the backlight according to the content of the image to be displayed, and modulates the LCD control signal, thereby effectively saving power consumption and improving contrast while maintaining image brightness. In the place where the light is judged, the liquid crystal unit in the cell is opened, and the corresponding LED area is also added with the backlight value. The voltage is such that its brightness reaches a certain backlight brightness; in the darkest part, the liquid crystal cell in the cell is completely turned off, and the voltage of the corresponding LED cell is also minimized (or turned off), thereby reducing light leakage. Since the side light is used, the LCD display device can be made thin, reducing the size and weight.

The above is only the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any change or replacement that can be easily conceived by those skilled in the art within the technical scope of the present invention is It should be covered by the scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of protection defined by the claims.

Claims

Claim

A region backlight control method for side light guiding, comprising the steps of:

Obtaining a backlight value of each divided area according to a pixel brightness value in each divided area; obtaining a backlight compensation value of each divided area according to the backlight value;

The obtained backlight value is subjected to threshold value processing and then sent to the backlight control circuit to drive and illuminate the backlight source;

The obtained backlight compensation value is compensated and processed:

If the image needs to be compensated, the light diffusion coefficient formed by the backlight compensation signal is obtained, and image compensation is performed point by point and then sent to the display panel for display;

Otherwise, the image data is displayed directly on the display panel.

2. The area backlight control method for side light guiding according to claim 1, wherein the specific method for determining the backlight value is:

Calculate the maximum value of the RGB channel of each pixel of the input image, and use the maximum value as the brightness value of the pixel to obtain the maximum value and the average value of the pixel brightness values in each divided area;

According to the maximum value and the average value of the pixel brightness values in each of the divided regions, the backlight value is calculated according to the preset backlight value calculation manner to obtain the backlight value of the divided region;

The default backlight value calculation manner is:

BL'—Local _avg + f Local _avg , Local _max ) where β ' is the area backlight value, oc _vg is the average brightness of the area backlight value, and f(Local _avg , Local _max ) is the maximum and average value of the area pixel brightness The function.

The area backlight control method for the side light guide according to claim 2, wherein the preset backlight value calculation mode is limited by a threshold:

In order to define the backlight value of the back area, 0∞/^ is the average brightness of the area backlight value, and J Locai _avg , Locals is a function of the maximum value and the average value of the area pixel brightness, which is the upper limit of the threshold.

The area backlight control method for the side light guide according to claim 1, wherein the method for determining the backlight compensation value is specifically:

According to the backlight value of each divided area, the average value of the backlight brightness of the entire area is obtained by calculating the preset backlight average value;

According to the backlight value and the average value of each divided area, the variance of the backlight brightness of the entire area is obtained by the preset backlight variance calculation method; the preset backlight compensation value calculation method is adopted according to the above-mentioned average value and the condition set by the variance. The backlight compensation value of each divided area is obtained.

The method for controlling the area backlight of the side light guide according to claim 4, wherein the calculation method of the preset backlight average value is:

Where SZ^g is the average value of the backlight brightness of the entire area, which is the ith (i=l,

2, ......, Ν) the backlight value of each area; The preset backlight variance calculation method is:

Among them, BL^ is the back first variance, which is the average value of the backlight brightness of the whole area, and Β∑(ί is the backlight value of the i-th (i=l, 2, ..., Ν) area.

The area backlight control method for the side light guide according to claim 4, wherein the preset backlight compensation value calculation method is:

Where SZ^) is the backlight compensation value of the i (i=l, 2, ..., N) regions,

⁷ is the undefined backlight value of the i-th (i=l, 2, ..., N) region, BL max V is the maximum value of N backlight values, and BL is N backlight values. Variance, 7 is the variance threshold, is the average of N backlight values, and Γ is the mean threshold.

7. The area backlight control method for side light guiding according to claim 1, wherein the input image is a video image, and a backlight value and a backlight compensation value obtained from a previous frame image of the video are used for the current frame. The backlight control and backlight compensation of the image, while the backlight value and backlight compensation value obtained by the current frame image are used for backlight control and backlight compensation of the latter frame image.

8. The area backlight control method for side light guiding according to claim 7, wherein the video image is played at 30 frames or 25 frames per second.

9. A backlight device, comprising: a backlight source group, a liquid crystal panel for displaying a video image, a PWM control circuit for controlling backlight illumination, a backlight value and a backlight compensation value circuit, a video converter, a backlight compensation circuit, and a liquid crystal a control circuit, wherein: a video converter converts the input video to obtain video image data to be processed; determines a backlight value and a backlight compensation value circuit, and processes the video image data to obtain a backlight value and a backlight compensation value of each divided region of the video ;

The PWM control circuit modulates the backlight group of each divided area on the backlight source group according to the backlight value to illuminate the liquid crystal panel; the backlight compensation circuit outputs a backlight compensation signal according to the backlight compensation value; and the liquid crystal control circuit receives the backlight compensation signal to the video image The data is compensated and sent to the LCD panel for display.

The backlight device according to claim 9, wherein the backlight source group is a backlight source group of a single side or a double side of the liquid crystal panel.