CN114203117B - Local dimming method and display device - Google Patents

Abstract

The present invention provides an area dimming method, comprising: dividing a digital image into a plurality of blocks, and calculating backlight parameters of each block; performing backlight simulation on the backlight parameters to calculate the light source brightness of each pixel; Multiple value ranges to quantify the backlight parameters into multiple reference backlight parameters; perform backlight simulation on the reference backlight parameters to calculate the reference light source brightness for each pixel; for each pixel, if the corresponding reference light source brightness is the darkest backlight parameter, the gain of the pixel is set to be less than or equal to the first value, otherwise the gain of the pixel is calculated according to the ratio between the brightness of the corresponding light source and the brightness of the reference light source; and for each pixel, the gray scale of the pixel is adjusted according to the corresponding gain value, and drive the display panel according to the adjusted grayscale value.

Description

Area dimming method and display device

【Technical field】

The present application relates to an area dimming method and a display device capable of dynamically determining pixel gain.

【Background technique】

With the development of image display technology, consumers have higher and higher requirements for image quality, so the regional dimming technology has been developed, that is, the screen is divided into multiple areas, and each area uses a corresponding backlight according to its own screen content. Brightness increases the contrast of the picture. In some technologies, the area where the brightness of the backlight decreases will amplify the grayscale value of the pixel (including red, blue and green) according to a gain to compensate, but if there is noise in the pixel, the noise will be amplified and caused by Color cast. For example, when a black background is to be displayed, the grayscale values of red, blue, and green in the pixel should be equal or close to each other. If green has positive noise, the noise will be amplified so that the pixel has a green color cast. Also, in some cases the calculated gain overcompensates the grayscale values.

[Content of the invention]

An embodiment of the present invention provides a regional dimming method, which is suitable for a display device. The display device includes a display panel and a backlight module, and the backlight module includes a plurality of light-emitting units. The regional dimming method includes: dividing a digital image into a plurality of blocks, and calculating a backlight parameter of each block, wherein the digital image includes a plurality of pixels, these backlight parameters correspond to the light-emitting units respectively, and each backlight parameter is used to adjust The brightness of the corresponding light-emitting unit; the backlight source simulation is performed on the backlight parameters to calculate the light source brightness of each pixel; these backlight parameters are quantified into a plurality of reference backlight parameters according to a plurality of numerical ranges, and these reference backlight parameters include a darkest Backlight parameters; perform backlight simulation on these reference backlight parameters to calculate the reference light source brightness of each pixel; for each pixel, if the corresponding reference light source brightness is the darkest backlight parameter, set the gain of the pixel to be less than or equal to the first A value, otherwise the gain of the pixel is calculated according to the ratio between the brightness of the corresponding light source and the brightness of the reference light source; and for each pixel, the grayscale value of the pixel is adjusted according to the corresponding gain, and the drive is driven according to the adjusted grayscale value Display panel.

In some embodiments, each light-emitting unit includes at least one light-emitting diode, and the backlight parameters include a duty cycle of the corresponding light-emitting diode. The regional dimming method further includes: driving the backlight module according to the backlight parameters.

In some embodiments, the aforementioned first value is 1.

In some embodiments, the number of the above-mentioned numerical ranges is 2, and the step of quantifying these backlight parameters into reference backlight parameters according to the numerical range includes: for each backlight parameter, if the backlight parameter is greater than a threshold, set the backlight parameter to two The value is converted into a brightest backlight parameter, otherwise the backlight parameter is binarized into the darkest backlight parameter.

In some embodiments, the above step of calculating the gain of the pixel according to the ratio between the corresponding light source luminance and the reference light source luminance is performed according to the following mathematical formula 1.

[Mathematical formula 1]

G=(R) ^(-1/γ)

Where G is the gain, γ is a real number, and R is the ratio between the brightness of the light source and the brightness of the reference light source.

From another perspective, an embodiment of the present invention provides a display device including a backlight module, a display panel and a circuit. The backlight module includes a plurality of light emitting units. The circuit is used to perform the following steps: dividing a digital image into a plurality of blocks, and calculating the backlight parameters of each block, wherein the digital image includes a plurality of pixels, and these backlight parameters are respectively corresponding to the light-emitting units, and each backlight The parameters are used to adjust the brightness of the corresponding light-emitting unit; perform backlight simulation on these backlight parameters to calculate the brightness of the light source of each pixel; quantify these backlight parameters into multiple reference backlight parameters according to multiple value ranges, these reference backlight parameters The parameters include a darkest backlight parameter; perform backlight simulation on these reference backlight parameters to calculate the reference light source brightness of each pixel; for each pixel, if the corresponding reference light source brightness is the darkest backlight parameter, set the pixel's brightness. The gain is less than or equal to the first value, otherwise the gain of the pixel is calculated according to the ratio between the brightness of the corresponding light source and the brightness of the reference light source; and for each pixel, the grayscale value of the pixel is adjusted according to the corresponding gain, and according to the adjusted grayscale value to drive the display panel.

In the above-mentioned regional dimming method, it is possible to avoid the amplification of noise in the dark area and to avoid excessive compensation of pixels.

In order to make the above-mentioned features and advantages of the present invention more obvious and easy to understand, the following embodiments are given and described in detail with the accompanying drawings as follows.

【Description of drawings】

FIG. 1 is a schematic diagram illustrating a display device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating dividing a digital image into a plurality of blocks according to an embodiment of the present invention.

FIG. 3 is a schematic diagram illustrating a flow chart of regional dimming according to an embodiment of the present invention.

FIG. 4 is a schematic diagram illustrating generating a reference light source luminance according to an embodiment of the present invention.

【Symbol Description】

100: Display device

110: Circuits

120: Backlight module

121: Optical film

122: Diffuser

123: Reflector

124: LEDs

130: Display panel

210: Digital Imaging

220:Block

230: Lighting unit

301, 303, 304, 306, 308: Steps

302: Backlight parameters

303_SB: light source brightness

305: Reference backlight parameters

306_RSB: Reference light source brightness

309: output image

【Detailed ways】

Regarding the "first", "second" and the like used herein, it does not mean a particular order or order, but only for distinguishing components or operations described in the same technical terms.

FIG. 1 is a schematic diagram illustrating a display device according to an embodiment. Referring to FIG. 1 , the display device 100 may be a television, a computer screen or other suitable screen or an electronic device having a screen. The display device 100 includes a circuit 110 , a backlight module 120 and a display panel 130 . The circuit 110 can be a microprocessor, a microcontroller, a digital image processing chip, an application specific integrated circuit, etc. In some embodiments, the circuit 110 is a time controller. The backlight module 120 includes an optical film 121 , a diffuser 122 , a reflector 123 and a light emitting diode 124 , wherein the optical film 121 is, for example, a light guide, a polarizer or any optical film. The display panel 130 is a liquid crystal display panel, and the liquid crystal display panel may be a fringe field switching (FFS) panel, an in-plane switching (IPS) panel, a twisted nematic (TN) panel, Vertical alignment (VA) panels, etc., the present invention is not limited thereto.

The circuit 110 is used for receiving a digital image, and controlling the light-emitting diode 124 according to the content of the digital image to complete the method of regional dimming. In particular, when very dark picture content is to be displayed, the gain of the pixel will be controlled below a value so as not to amplify the noise. The following examples will be used to describe the area dimming method in detail.

FIG. 2 is a schematic diagram illustrating dividing a digital image into a plurality of blocks according to an embodiment. Referring to FIG. 2 , a digital image 210 is obtained first. The digital image 210 includes a plurality of pixels, and each pixel includes a plurality of grayscale values (eg, red, green, and blue). The digital image 210 is divided into a plurality of blocks 220 , each block 220 corresponds to a light-emitting unit 230 , and the light-emitting unit 230 includes one or more light-emitting diodes 124 . It should be noted that FIG. 2 is for illustration only, and the present invention does not limit the number and configuration of the blocks 220 , nor does it limit the number of the light emitting diodes 124 in each light emitting unit 230 . In some embodiments, the light-emitting diodes 124 may also be sub-millimeter light-emitting diodes (mini LEDs) or micro-diodes (micro LEDs).

FIG. 3 is a schematic flow chart illustrating area dimming according to an embodiment. Referring to FIGS. 2 and 3, in step 301, for each block in the digital image 210, a backlight parameter 302 is calculated according to the pixels in the block, and the backlight parameter 302 is used to adjust the brightness of the corresponding light-emitting unit . For example, the backlight parameters 302 include the duty cycle of the LED 124, a duty cycle of 100% corresponds to maximum brightness, and a duty cycle of 0% corresponds to minimum brightness. Generally speaking, when the pixels in the block are brighter, the calculated duty cycle is relatively large, and conversely, when the pixels in the block are darker, the calculated duty cycle is relatively small. For example, the maximum value of the red, green and blue grayscale values in each pixel in the block can be calculated first as the pixel brightness. Next, calculate the average and the highest tenth of the pixel brightness in the block (that is, the first 10% of the pixel brightness), then multiply these two values by their respective weights and add them up, and calculate the duty cycle according to the sum. (eg by a linear or non-linear increasing function). However, the above method is only an example, and in other embodiments, any algorithm can be used to calculate the duty cycle. In this embodiment the duty cycle is recorded with 12 bits, so the value of the duty cycle is in the range of 0-4095.

In some embodiments, the backlight parameter 302 may also be a voltage value, which is used to control the magnitude of the current flowing through the LED, thereby adjusting the brightness of the LED. In some embodiments, the backlight parameter 302 may also be the number of light-emitting diodes in a light-emitting unit that are turned on, thereby controlling the brightness of a light-emitting unit.

The next process is divided into two paths. In the first path (step 303 ), a backlight source simulation is performed on the backlight parameters 302 to calculate the light source brightness 303_SB of each pixel. The backlight source simulation is also called light shape imitation, and the simulation is determined based on a model of the display device 100 , and the model can be obtained through experiments or arbitrary methods.

In step 304, the backlight parameters 302 are quantized into a plurality of reference backlight parameters 305 according to a plurality of numerical ranges. In some embodiments, the number of value ranges is 2, and the above-mentioned quantization is binarization, for example, the two value ranges are [0, 384) and [384, 4095]. That is, if the backlight parameter is greater than or equal to a threshold (eg 384), the backlight parameter is binarized to 4095 (also called the brightest backlight parameter), otherwise the backlight parameter is binarized to 0 (also called the brightest backlight parameter). called the darkest backlight parameter). For example, please refer to FIG. 4 , which is a schematic diagram illustrating generating the luminance of the reference light source according to an embodiment. The backlight parameters 302 of each block can be calculated according to the digital image 210 , and the reference backlight parameters 305 can be obtained after the backlight parameters 302 are quantized (binarized in FIG. 4 ). It can be seen from Figure 4 that the darker areas in the digital image will correspond to 0, and the rest will correspond to 4095.

Referring to FIG. 3 and FIG. 4 , in step 306 , backlight simulation is performed on the reference backlight parameters 305 to calculate the reference light source luminance 306_RSB of each pixel. Although the light source will be diffused during backlight simulation, in this embodiment, there are still many values in the reference light source luminance 306_RSB that are 0 (ie, the darkest backlight parameter).

In step 308, the gain is calculated for each pixel, especially when the pixel's reference light source brightness 306_RSB is the darkest backlight parameter, the gain is set to be less than or equal to a first value (eg, 1), because this The pixel corresponds to the black background in the digital image 210. If the gain is greater than 1, it will amplify the noise and cause color shift. In some embodiments, the above-mentioned first value may also be 0.9, 1.1, 1.2, 1.3 or other suitable values. In some embodiments, the gain is set to 1 when the pixel's reference light source brightness 306_RSB is the darkest backlight parameter. On the other hand, if the pixel's reference light source luminance 306_RSB is not the darkest backlight parameter, the gain can be calculated according to the ratio between the corresponding light source luminance 303_SB and the reference light source luminance 306_RSB, as shown in Equation 1 below.

[Mathematical formula 1]

G=(R) ^(-1/γ)

where G is the gain. γ is a real number, such as 2.2. R is the ratio between the brightness of the light source and the brightness of the reference light source, and can also be expressed as R=a/b, where a is the brightness of the light source and b is the brightness of the reference light source. When the brightness of the reference light source is the brightest backlight parameter (ie, 4095), the ratio R represents the percentage of the maximum brightness. At this time, the grayscale value needs to be increased, but the change of the grayscale value must pass through the gamma curve before it can be reflected. The real brightness changes, so the above ratio R must be substituted into the inverse function of the gamma curve. In addition, the value -1 in Equation 1 indicates that the adjustment of the grayscale value is inversely proportional to the adjustment of the brightness of the backlight.

In this embodiment, the above two numerical ranges are [0,384) and [384,4095], but in other embodiments, more numerical ranges can be set, such as [0,384), [384,2048) and [2048 , 4095], the reference backlight parameters corresponding to these three numerical ranges are 0, 2048 and 4095 respectively. The present invention does not limit the number of the above numerical ranges.

After the gain is calculated, the grayscale value (including red, green and blue) of the pixel can be adjusted according to the corresponding gain to obtain the output image 309 . Finally, the display panel 130 is driven according to the adjusted grayscale value (ie, the output image 309 ), and the backlight module 120 is driven according to the backlight parameters 302 . For example, the circuit 110 turns on the light emitting diodes in the corresponding light emitting units according to the backlight parameter 302 (eg, duty cycle). The circuit will also transmit the adjusted grayscale value to a source driver, and the source driver will generate a corresponding voltage on the corresponding data line accordingly. However, those skilled in the art can understand how to calculate the grayscale value according to The display panel is driven, and its details are not described in detail here.

In the above-mentioned regional dimming method, the gain of the pixel is dynamically determined by an algorithm in the dark area of the screen, thereby avoiding the amplification of noise in the dark area and the excessive compensation of the pixel.

Although the present invention has been disclosed as above with examples, it is not intended to limit the present invention. Any person of ordinary skill in the art can make some changes and modifications without departing from the spirit and scope of the present invention. The protection scope of the present invention should be determined by the appended claims.

Claims (10)

1. A regional dimming method, applicable to a display device, the display device comprising a display panel and a backlight module, the backlight module comprising a plurality of light-emitting units, the regional dimming method comprising: Divide the digital image into a plurality of blocks, and calculate the backlight parameters of each of the plurality of blocks, wherein the digital image includes a plurality of pixels, and a plurality of the backlight parameters respectively correspond to the plurality of light-emitting units , each of the plurality of backlight parameters is used to adjust the brightness of the corresponding light-emitting unit; performing a backlight simulation on a plurality of the backlight parameters to calculate a light source brightness for each of the plurality of pixels; quantifying a plurality of the backlight parameters into a plurality of reference backlight parameters according to a plurality of numerical ranges, the plurality of reference backlight parameters including a darkest backlight parameter; performing the backlight simulation on the plurality of reference backlight parameters to calculate a reference light source luminance for each of the plurality of pixels; For each of the plurality of pixels, if the brightness of the corresponding reference light source is the darkest backlight parameter, the gain of the pixel is set to be less than or equal to the first value, otherwise, according to the brightness of the corresponding light source and the the ratio between the intensities of the reference light sources to calculate the gain of the pixel; and For each of the plurality of pixels, the grayscale value of the pixel is adjusted according to the corresponding gain, and the display panel is driven according to the adjusted grayscale value. 2 . The local dimming method according to claim 1 , wherein each of the plurality of light emitting units comprises at least one light emitting diode, the plurality of backlight parameters comprises a corresponding duty cycle of the light emitting diode, the Area dimming methods also include: The backlight module is driven according to a plurality of the backlight parameters. 3 . The area dimming method of claim 1 , wherein the first value is 1. 4 . 4. The area dimming method according to claim 1, wherein the number of the plurality of numerical ranges is 2, and a plurality of the backlight parameters are quantized into the plurality of reference backlight parameters according to the plurality of numerical ranges The steps include: For each of the plurality of backlight parameters, if the backlight parameter is greater than a threshold, the backlight parameter is binarized into the brightest backlight parameter; otherwise, the backlight parameter is binarized into the brightest backlight parameter. Dark backlight parameters. 5. The area dimming method according to claim 1, wherein the step of calculating the gain of the pixel according to the ratio between the corresponding luminance of the light source and the luminance of the reference light source is based on the following mathematical formula 1: implement: [Mathematical formula 1] G=(R) ^(-1/γ) Wherein G is the gain, γ is a real number, and R is the ratio between the brightness of the light source and the brightness of the reference light source. 6. A display device comprising: a backlight module, including a plurality of light-emitting units; display panel; and A circuit that performs several of the following steps: Divide the digital image into a plurality of blocks, and calculate the backlight parameters of each of the plurality of blocks, wherein the digital image includes a plurality of pixels, and a plurality of the backlight parameters respectively correspond to the plurality of light-emitting units , each of the plurality of backlight parameters is used to adjust the brightness of the corresponding light-emitting unit; performing a backlight simulation on a plurality of the backlight parameters to calculate a light source brightness for each of the plurality of pixels; quantifying a plurality of the backlight parameters into a plurality of reference backlight parameters according to a plurality of numerical ranges, the plurality of reference backlight parameters including a darkest backlight parameter; performing the backlight simulation on the plurality of reference backlight parameters to calculate a reference light source luminance for each of the plurality of pixels; For each of the plurality of pixels, if the brightness of the corresponding reference light source is the darkest backlight parameter, the gain of the pixel is set to be less than or equal to the first value, otherwise, according to the brightness of the corresponding light source and the the ratio between the intensities of the reference light sources to calculate the gain of the pixel; and For each of the plurality of pixels, the grayscale value of the pixel is adjusted according to the corresponding gain, and the display panel is driven according to the adjusted grayscale value. 7. The display device according to claim 6, wherein each of the plurality of light emitting units comprises at least one light emitting diode, the plurality of the backlight parameters comprise a duty cycle of the corresponding light emitting diode, and the circuit is based on A plurality of the backlight parameters are used to drive the backlight module. 8. The display device of claim 6, wherein the first numerical value is one. 9. The display device of claim 6, wherein the number of the plurality of numerical ranges is 2, and the circuit is further configured to: For each of the plurality of backlight parameters, if the backlight parameter is greater than a threshold, the backlight parameter is binarized into the brightest backlight parameter; otherwise, the backlight parameter is binarized into the brightest backlight parameter. Dark backlight parameters. 10. The display device according to claim 6, wherein the step of calculating the gain of the pixel according to the ratio between the corresponding luminance of the light source and the luminance of the reference light source is performed according to the following mathematical formula 1: [Mathematical formula 1] G=(R) ^(-1/γ) where G is the gain, γ is a real number, and R is the ratio between the brightness of the light source and the brightness of the reference light source.

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