Local dimming for panel display devices using one-dimensional (1D) light source array

Abstract

To provide a technique capable of executing a local dimming function while reducing the volume of a panel display device.SOLUTION: A backlight device includes a plurality of light sources configured to illuminate a plurality of zones of a display panel, respectively. The zones are aligned in a first direction, and each zone includes a plurality of subzones aligned in a second direction perpendicular to the first direction. The backlight control circuit is configured to receive an input image and determine a backlight value for a target light source of the light sources, the target light source corresponding to a target zone of the plurality of zones. Determining the backlight value for the target light source includes: determining local brightness values of respective subzones of the target zone based on the input image; and determining the backlight value for the target light source based on the local brightness values of the subzones of the target zone.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present disclosure relates generally to panel display devices, and more particularly to local dimming for panel display devices using a one-dimensional (1D) light source array.

Background Art

[0002] A panel display device including a light transmissive display panel (e.g., a light transmissive liquid crystal display (LCD) panel) may incorporate a backlight device for illuminating the light transmissive display panel. For example, recent backlight devices such as direct-lit backlights, full-array backlights, etc. may be configured to illuminate a display panel with a two-dimensional (2D) array of light sources (e.g., light emitting diodes (LEDs)). By using a 2D light source array in a backlight device, a local dimming function capable of achieving high dynamic contrast and low power consumption by individually controlling each light source of the 2D light source array according to input image data can be implemented.

[0003] However, using a 2D light source array provided behind a display panel in a panel display device inevitably increases the thickness of the panel display device, so that the volume of the panel display device may undesirably increase. Therefore, it would be beneficial to provide a technique capable of performing a local dimming function while reducing the volume of the panel display device.

Summary of the Invention

[0004] This summary is provided to introduce a selection of concepts in a simplified form that are further described below. This summary is not necessarily intended to identify the key features or essential features of the present disclosure. The present disclosure may include the various aspects and embodiments described below.

[0005] The present disclosure provides a display device including a display panel, a backlight device, and a backlight control circuit. The backlight device includes a plurality of light sources configured to illuminate a plurality of zones of the display panel respectively. The plurality of zones are arranged in a first direction, and each of the plurality of zones includes a plurality of sub-zones arranged in a second direction perpendicular to the first direction. The backlight control circuit is configured to receive an input image and determine a backlight value for a target light source among the plurality of light sources. The target light source corresponds to a target zone among the plurality of zones. Determining the backlight value for the target light source includes determining a local luminance value of each sub-zone of the target zone based on the input image, and determining the backlight value for the target light source based on the local luminance values of the sub-zones of the target zone.

[0006] In another exemplary embodiment, the present disclosure provides a display driver including a driver circuit and a backlight control circuit. The driver circuit is configured to drive a display panel based on an input image. The display panel is illuminated by a backlight device including a plurality of light sources configured to illuminate a plurality of zones of the display panel respectively. The plurality of zones are arranged in a first direction, and each of the plurality of zones includes a plurality of sub-zones arranged in a second direction perpendicular to the first direction. The backlight control circuit is configured to determine a backlight value for a target light source among the plurality of light sources. The target light source corresponds to a target zone among the plurality of zones. Determining the backlight value for the target light source includes determining a local luminance value of each sub-zone of the target zone based on the input image, and determining the backlight value for the target light source based on the local luminance values of the sub-zones of the target zone.

[0007] In yet another exemplary embodiment, the present disclosure provides a method. The method includes illuminating a plurality of zones of a display panel respectively by a backlight device including a plurality of light sources. The plurality of zones are arranged in a first direction, and each of the plurality of zones includes a plurality of sub-zones arranged in a second direction perpendicular to the first direction. The method further includes receiving an input image and determining a backlight value for a target light source among the plurality of light sources. The target light source corresponds to a target zone among the plurality of zones. Determining a backlight value for the target light source includes determining local luminance values of each sub-zone of the target zone based on the input image and determining a backlight value for the target light source based on the local luminance values of the sub-zones of the target zone.

[0008] Other features and aspects are described in more detail below with reference to the accompanying drawings.

Brief Description of the Drawings

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[0029] For ease of understanding, if possible, the same reference numerals are used to indicate the same elements common to the drawings. It is expected that the elements disclosed in one embodiment can be used in other embodiments without particular description. Subscripts may be attached to the reference numerals to distinguish the same elements from each other. The drawings referred to in this specification should not be understood as being drawn to scale unless otherwise noted. Also, the drawings are often simplified, and details or components are omitted for clarity of presentation and explanation. The drawings and discussions are intended to explain the principles discussed below.

DETAILED DESCRIPTION OF THE INVENTION

[0030] The following detailed description is, in essence, merely exemplary and is not intended to limit the present disclosure and its application and usage. Further, there is no intention to be bound by any explicit or implicit theory presented in the foregoing background, summary, brief description of the drawings, or the following detailed description of the invention.

[0031] In the following detailed description of the embodiments, many specific details are presented to provide a deeper understanding of the disclosed technology. However, it will be apparent to those skilled in the art that the disclosed technology can be practiced without these specific details. In other instances, well-known configurations are not described in detail to avoid unnecessarily complicating the description.

[0032] As used herein, the term "coupled" means directly connected or connected through one or more intervening components or circuits. Further, throughout the application, ordinal numbers (e.g., first, second, third, etc.) may be used as adjectives of elements (i.e., any noun in the application). The use of ordinal numbers is not for implying or generating a particular ordering of any elements, nor for limiting any element to only a single element, unless specified and disclosed by the use of terms such as "before," "after," "single," and other similar terms. Rather, the use of ordinal numbers is for distinguishing elements. For example, the first element is different from the second element, the first element may include more than one element, and may follow (or precede) the second element in the ordering of the elements.

[0033] As discussed above, recent backlight systems, such as direct - type backlights and full - array backlights, may be configured to illuminate a display panel with a two - dimensional (2D) array of light sources (e.g., light - emitting diodes (LEDs)) in order to implement a local dimming function. The local dimming function can achieve a high dynamic contrast by individually controlling each light source of the 2D light source array according to input image data. However, since the 2D light source array provided behind the display panel inevitably increases the thickness of the panel display device, using a 2D light source array in a panel display device may undesirably increase the volume of the panel display device.

[0034] The present disclosure recognizes that a local dimming function can be implemented in an edge-lit panel display device using a one-dimensional (1D) light source array configured to illuminate a display panel from its edge. By using an edge lighting configuration to illuminate the display panel, the thickness of the panel display device can be reduced, which can facilitate the reduction of the volume of the panel display device. However, the local dimming function based on the 1D light source array can cause different problems than those based on the 2D light source array. Hereinafter, various embodiments for appropriately controlling the luminance level of the light sources of the 1D light source array to implement the local dimming function in the edge-lit panel display device will be described.

[0035] FIG. 1 illustrates a configuration example of an edge-lit panel display device 1000 according to one or more embodiments. In the illustrated embodiment, the panel display device 1000 includes a display panel 100 and a 1D backlight device 200. The display panel 100 may be a light transmissive display panel such as, for example, a liquid crystal display (LCD) panel. The 1D backlight device 200 includes a 1D array of light sources 210 and a light diffusion plate 250 having a main surface attached to the back surface of the display panel 100. The light sources 210 are arranged in a predetermined direction (the vertical direction in FIG. 1) and are coupled to the side surface 250a of the light diffusion plate 250. Each of the light sources 210 may include one or more light emitting diodes (LEDs) or other types of light emitting elements. The light beams emitted from the light sources 210 enter the side surface of the light diffusion plate 250 and are diffused across the main surface of the light diffusion plate 250 to illuminate the display panel 100.

[0036] The luminance level of each light source 210 of the 1D backlight device 200 may be determined based on a "zone" defined by dividing the display panel 100. In one or more embodiments, the "zone" of the display panel 100 is defined for each light source 210 such that the "zone" is illuminated by the respective light source 210. To implement the local dimming function, the luminance level of each light source 210 may be controlled based on the average picture level (APL) of the image displayed in the corresponding zone.

[0037] FIG. 2 illustrates an arrangement example of zone 110 of display panel 100 according to one or more embodiments. Note that the directions may be shown using an XY orthogonal coordinate system. Here, the X-axis is oriented in the horizontal direction of display panel 100, and the Y-axis is oriented in the vertical direction of display panel 100. Zone 110 is defined such that each light source 210 illuminates the corresponding zone 110. In the illustrated embodiment, the zones 110 are arranged vertically (or arranged in the first direction), and the horizontal width of each zone 110 is the same as the horizontal width of display panel 110. Zone 110 has a substantially rectangular shape extending in the horizontal direction (or a second direction perpendicular to the first direction). Each light source 210 is configured to emit light in the horizontal direction (or the second direction) to illuminate the entire corresponding zone 110. Due to the light diffusion characteristics of light source 210, each light source 210 mainly illuminates the corresponding zone 110, but it should be noted that each light source 210 may secondarily illuminate at least a part of the zone 110 adjacent to the corresponding zone 110.

[0038] Since the horizontal width of each zone 110 is the same as the horizontal width of display panel 110, the vertical dimension (or vertical height) of each zone 110 is different from the horizontal dimension (or horizontal width) of each zone 110. In the embodiment illustrated in FIG. 2, each zone 110 is defined to be longer in the horizontal direction than in the vertical direction. In an implementation where the luminance level of each light source 210 is controlled based on the average picture level (APL) of the image displayed in the corresponding zone 110, due to the difference in the vertical and horizontal dimensions of each zone 110, an undesired change depending on the vertical and horizontal dimensions of the picture elements may occur in the luminance of the picture elements included in the displayed image.

[0039] Figure 3A illustrates an example of the relationship between an input image and the luminance values of each light source 210 according to one or more examples of the present disclosure. Note that in Figure 3A (and the following drawings), subscripts from 1 to 8 are attached to the reference numeral "110" to distinguish the zones 110 from each other. In the illustrated example, the input image is within a background having the lowest specified luminance level (shown in white) and includes an image element 510 having the highest specified luminance level (shown in black). The image element 510 is a diagonal line that crosses the zones 110 1 ~110 8 . Here, the vertical dimension of the image element 510 is larger than the horizontal dimension.

[0040] In one implementation, in order to implement the local dimming function, the backlight value of each light source 210 may be determined based on the APL of the corresponding zone 110. As used herein, the backlight value refers to a value indicating the luminance level at which the target light source 210 should be controlled. In the example illustrated in Figure 3A, since the APLs of the zones 110 1 ~110 8 are the same, all the backlight values of the light sources 210 are commonly determined to be the same value, for example, "10".

[0041] Figure 3B illustrates another example of the relationship between an input image including an image element 520 and the luminance values of each light source 210 according to one or more examples of the present disclosure. In the illustrated example, the input image is within a background having the lowest specified luminance level (shown in white) and includes an image element 520 having the highest specified luminance level (shown in black). The image element 520 is a shape obtained by rotating the image element 510 illustrated in Figure 3A by 90°. Accordingly, the vertical dimension of the image element 520 is the same as the horizontal dimension of the image element 510, and the horizontal dimension of the image element 520 is the same as the vertical dimension of the image element 510. The entire image element 520 is located in the zone 110 1 .

[0042] In one implementation, the backlight value of each light source 210 can be determined based on the APL of the corresponding zone 110, similar to the case of FIG. 3A. In this case, while the backlight value of the light source 210 corresponding to zone 110 2 ~110 8 is determined to be 0, the APL of zone 110 for the case of FIG. 3B 1 is 8 times the APL of zone 110 for the case of FIG. 3A 1 ~110 8 , so the backlight value of the light source 210 corresponding to zone 110 1 is determined to be a non-zero value "80". Therefore, the actual luminance of the image element 520 will be different from that of the image element 510. The results shown in FIGS. 3A and 3B suggest that when the luminance value of each light source 210 is determined based on the APL of the corresponding zone 110, the luminance of the image element may undesirably change depending on the vertical and horizontal dimensions of the image element.

[0043] The present disclosure recognizes that the undesired change in the image element depending on the vertical and horizontal dimensions of the image element is due to the large aspect ratio of zone 110. As used herein, the aspect ratio refers to the ratio of the larger of the horizontal width and the vertical height of zone 110 to the smaller of the horizontal width and the vertical height. For example, in the zone arrangement illustrated in FIG. 2, the horizontal width of zone 110 is much larger than the vertical height of zone 110, and thus the aspect ratio of zone 110 is much larger than 1. The large aspect ratio of zone 110 can cause image elements directed in different directions to have different backlight values of the light source 210, resulting in an undesired difference in the luminance levels of the image elements. This can also undesirably degrade the image quality. Various embodiments for improving the image quality in a panel display device based on a 1D backlight device are provided below.

[0044] In one or more embodiments, to address unwanted variations in the luminance of image elements that depend on the vertical and horizontal dimensions of the image elements, the backlight value of each light source 210 may be determined based on sub-zones 210 defined by dividing each zone 110 such that the "sub-zone" 120 has a substantially rectangular shape. In one or more embodiments, as illustrated in FIGS. 4A and 4B, the aspect ratio of the sub-zone 120 is closer to 1 than the aspect ratio of the zone 110. In one implementation, the sub-zone 120 has a substantially square shape. By using sub-zones 120 having an aspect ratio equal to or close to 1, unwanted variations in the luminance of image elements that depend on the vertical and horizontal dimensions of the image elements may be effectively mitigated. In the illustrated embodiment, each zone 110 includes 12 horizontally aligned sub-zones 120. In other embodiments, each zone 110 may include fewer than 12 or more than 12 horizontally aligned sub-zones 120.

[0045] In one or more embodiments, the backlight value of a target light source 210 may be determined as follows. First, the APL of the sub-zones 120 of the zone 110 corresponding to the target light source 210 may be calculated, and then the maximum APL of that zone 110, i.e., the maximum value of the APLs of the sub-zones 120 of that zone 110, may be determined. The backlight value of the target light source 210 may be determined based on the maximum APL of the zone 110 corresponding to that light source 210. In one implementation, the backlight value of the target light source 210 may be determined to be proportional to the maximum APL of the corresponding zone 110.

[0046] FIG. 4A illustrates, for an input image including an image element 510 according to one or more examples of the present disclosure, an example of the maximum APL of each zone 110 and the backlight values determined for each light source 210. In the illustrated example, the image element 510 is located in the leftmost column of the subzone 120. The APL of the leftmost subzone 120 of each zone 110 is calculated as, for example, “10”, and the APL of the other subzones 120 is calculated as “0”. Accordingly, the maximum APL of all the zones 110 is determined to be “10”, and the backlight values of all the light sources 210 are determined to be “10”. The image element 510 is displayed by the light source 210 using a backlight value of “10”.

[0047] FIG. 4B illustrates, for an input image including an image element 520 according to one or more examples of the present disclosure, an example of the maximum APL of each zone 110 and the backlight values determined for each light source 210. In the illustrated example, the image element 520 is located in the leftmost eight subzones 120 of the zone 110 1 . The APL of the leftmost eight subzones 120 of the zone 110 1 is calculated as, for example, “10”, and the APL of the other subzones 120 is calculated as “0”. Further, the maximum APL of the zone 110 1 is determined to be “10”, and the maximum APLs of the other zones 110 2 - 110 8 are determined to be “0”. The backlight value of the light source 210 corresponding to the zone 110 1 is determined to be “10”, and the backlight values of the other light sources 210 are determined to be “0”. Accordingly, the image element 520 is displayed by the light source 210 corresponding to the zone 110 1 using a backlight value of “10”. The results illustrated in FIGS. 4A and 4B show that the determination method based on the subzone 120 effectively mitigates undesired variations in the luminance of the image element depending on the vertical and horizontal dimensions of the image element.

[0048] The above-described determination method based on the sub-zone 120 effectively mitigates the undesired change in the luminance of the image element that depends on the vertical and horizontal dimensions of the image element, but there is still room for further improvement in image quality. More specifically, according to the above-described determination method based on the sub-zone 120, when the image element crosses the boundary of the sub-zone 120, the luminance of the image element may undesirably decrease. FIGS. 5A, 5B, and 5C illustrate examples of changes in the luminance of the image element 530 according to one or more examples of the present disclosure.

[0049] Referring to FIG. 5A, the image element 530 is initially located in the third column from the left of the sub-zone 120 of the display panel 100. In this case, the maximum APL of all the zones 110 is calculated as "10", and the backlight value of all the light sources 210 is determined as "10". As illustrated in FIG. 5B, when the image element 530 crosses the boundary between the third and fourth columns of the sub-zone 120, the maximum APL of one or more zones 110 decreases, and accordingly, the backlight value of one or more light sources 210 also decreases. In the example illustrated in FIG. 5B, the APL of the third sub-zone 120 from the left of the zone 110 is calculated as "8", and the APL of the fourth sub-zone 120 from the left of the zone 110 is calculated as "9". Accordingly, the backlight values of the light sources 210 corresponding to the zones 110 and 110 are determined as "8" and "9", respectively. As illustrated in FIG. 5C, after the image element 530 crosses the boundary between the third and fourth columns of the sub-zone 120 and the entire image element 530 is inside the fourth column of the sub-zone 120, the maximum APL of all the zones 110 is calculated as "10", and the backlight value of all the light sources 210 is determined as "10" as in the case of FIG. 5A. As illustrated in FIGS. 5A, 5B, and 5C, the movement of the image element 530 crossing the boundary between the third and fourth columns of the sub-zone 120 may undesirably cause a decrease in the luminance of the image element 530. From this perspective, various embodiments for more appropriately determining the backlight value of each light source of the 1D light source array to implement the local dimming function in the edge illumination panel display device will be described below. 4 of the third sub-zone 120 from the left is calculated as "8", and the APL of the fourth sub-zone 120 from the left of the zone 110 5 is calculated as "9". Accordingly, the APL of the zone 110 4 and 110 5 is calculated as "8" and "9", respectively. As illustrated in FIG. 5C, after the image element 530 crosses the boundary between the third and fourth columns of the sub-zone 120 and the entire image element 530 is inside the fourth column of the sub-zone 120, the maximum APL of all the zones 110 is calculated as "10", and the backlight value of all the light sources 210 is determined as "10" as in the case of FIG. 5A. As illustrated in FIGS. 5A, 5B, and 5C, the movement of the image element 530 crossing the boundary between the third and fourth columns of the sub-zone 120 may undesirably cause a decrease in the luminance of the image element 530. From this perspective, various embodiments for more appropriately determining the backlight value of each light source of the 1D light source array to implement the local dimming function in the edge illumination panel display device will be described below.

[0050] FIG. 6 illustrates a configuration example of a display driver 300 of a panel display device 1000 according to one or more embodiments. The display driver 300 is configured to drive or update pixels of a display panel 100 based on input image data received from an external image source. The input image data corresponds to an input image and includes pixel data of each pixel of the display panel 100. The pixel data of a certain pixel may include gradations of each primary color (for example, red, green, and blue). The display driver 300 is further configured to control light sources of the 1D backlight device 200.

[0051] In the illustrated embodiment, the display driver 300 includes an image processing circuit 310, a driver circuit 320, and a backlight control circuit 330. The image processing circuit 310 is configured to perform image processing on the input image data to generate processed image data. The image processing executed by the image processing circuit 310 may include color adjustment, demura correction, debanding correction, image enlargement / reduction, gamma conversion, or other image processing. The driver circuit 320 is configured to drive or update the display panel 100 based on the processed image data.

[0052] The backlight control circuit 330 is configured to generate a backlight value for each light source 210 of the 1D backlight device 200 and control the light source 210 individually. The backlight value here may be a value indicating the luminance level at which the target light source 210 should be controlled. To implement the local dimming function, the backlight control circuit 330 is configured to receive the input image data and determine a backlight value for each light source 210 based on the input image data.

[0053] In the illustrated embodiment, the backlight control circuit 330 includes an image analysis circuit 340, a 1D random access memory (RAM) 350, and a backlight value generation circuit 360. The image analysis circuit 340 is configured to analyze input image data and generate a basic backlight value for each light source 210 based on the input image data. The image analysis circuit 340 is further configured to transfer the basic backlight value to the 1D RAM 350. The 1D RAM 350 is configured to store the basic backlight value received from the image analysis circuit 340. The backlight value generation circuit 360 is configured to generate a backlight value for each light source 210 by modifying the basic backlight value based on a display brightness value (DBV). Here, the DBV is a value that specifies the desired display brightness level of the panel display device 1000. The display brightness level referred to here is the brightness level of the display image as a whole displayed on the display panel 100. The DBV may be generated by an external controller based on a user operation. For example, when an instruction to adjust the display brightness level of the panel display device 1000 is manually input to the input device, the DBV may be generated based on the instruction. In one implementation, the backlight value generation circuit 360 may be configured to generate a backlight value for each light source 210 by multiplying the basic backlight value by a multiplication factor determined based on the DBV.

[0054] Depending on the implementation, in order to mitigate display unevenness that may occur due to variations in the characteristics of the light sources 210, the backlight value generation circuit 360 may be further configured to store the demura data and correct the base backlight value for each light source 210 based on the demura data. The demura data may include a demura compensation coefficient for each light source 210. In such an implementation, the backlight value generation circuit 360 may be configured to apply the demura compensation coefficient to the base backlight value for each light source 210 during the determination of the backlight value used to control each light source 210. The backlight value generated in this way is supplied to the 1D backlight device 200 and used to control each light source 210.

[0055] FIG. 7 is a flowchart illustrating an example of a process 700 for determining a backlight luminance value for each light source 210 by the backlight control circuit 330 according to one or more embodiments. It will be understood that any of the following steps may be performed in any suitable order.

[0056] In step 702 of process 700, the image analysis circuit 340 of the backlight control circuit 330 determines the local luminance value of each subzone 120 based on the input image. The "local luminance value" of the target subzone 120 as referred to herein may be a value representing the luminance of that subzone 120. Depending on the implementation, the local luminance value for the target subzone 120 may represent the luminance of that subzone 120 as well as the luminance of the surrounding area of that subzone 120.

[0057] FIG. 8 is a flowchart illustrating an example of a process 800 for determining the local luminance value of each subzone 120 according to one or more embodiments. In one implementation, process 800 is performed by the image analysis circuit 340. It will be understood that any of the following steps may be performed in any suitable order.

[0058] In step 802, the image analysis circuit 340 selects a target portion of the input image for each subzone 120. FIG. 9A illustrates an example of the selection of the target portion of the input image for each subzone 120 according to one or more embodiments. In FIG. 9A, reference numeral "120a" indicates the target subzone 120, and reference numeral "120b" indicates eight subzones 120 adjacent to the target subzone 120a. Reference numeral "130" indicates the center (e.g., geometric center) of the subzone 120. Reference numeral "130a" indicates the center (e.g., geometric center) of the target subzone 120a, and reference numeral "130b" indicates the center (e.g., geometric center) of the subzone 120b adjacent to the target subzone 120a.

[0059] In one or more embodiments, the target portion of the input image for the target subzone 120a is selected such that the target portion is displayed in the corresponding region 140a of the display panel 100. Here, the target region 140a is a substantially square region having a boundary passing through the centers of eight subzones 120b adjacent to the target subzone 120a. The centers of four of the eight adjacent subzones 120b are at the four corners of the corresponding region 140a, and the centers of the other four subzones 120b are on the four sides of the corresponding region 140a. The target portions of the input images for the other subzones 120 may be selected in the same manner as the target portion for the subzone 120a. The target portion for each subzone 120 may be selected in other ways as long as the region of the display panel 100 in which the target portion selected for each subzone 120 is displayed includes at least that subzone 120. It should be noted that the target portions of the input images for adjacent subzones 120 may overlap. In the example illustrated in FIG. 9A, the height and width of each target portion are both twice the height and width of the subzone 120, and the target portion for the subzone 120a partially overlaps the target portion for its adjacent subzone 120b.

[0060] Returning to FIG. 8, in step 804, the image analysis circuit 340 filters the target portion of the input image for each subzone 120 to generate a filtered image portion for each subzone 120. In one or more embodiments, the filtering is based on a filter including filter coefficients defined for each pixel of the target portion of the input image, and the filtered image portion is generated by applying the filter coefficients to the pixel data of each pixel of the target portion. In one implementation, the pixel data of each pixel of the filtered image portion can be generated by multiplying the pixel data of the corresponding pixel of the target portion by the filter coefficients defined for the corresponding pixel of the target portion.

[0061] FIG. 9B illustrates an example of filter coefficients defined for the pixels of the target portion for subzone 120a according to one or more embodiments. Here, the reference numeral "150a" indicates the target portion for subzone 120a. Shown in FIG. 9B is a portion of the input image including the target portion 150 for subzone 120a. The reference numeral 130a indicates the center of subzone 120a, and the reference numeral 130b indicates the corresponding center position of the adjacent subzone 120b in the input image. It should be noted that the outer edge of the target portion 150a for subzone 120a coincides with the boundary of the target portion 140a for subzone 120a shown in FIG. 9A.

[0062] The filter coefficients defined for the pixels of the target portion for subzone 120a depend on the respective distances between the pixels of the target portion of the input image and the center of subzone 120a in the input image. In one implementation, the filter coefficients defined for the pixels of the target portion for subzone 120a increase as the respective distances between the pixel of the target portion of the input image and the center of subzone 120a in the input image decrease. In the illustrated embodiment, the filter coefficient for the pixel located at the center of subzone 120a is the maximum filter coefficient Wi (e.g., 1.0), and the filter coefficient for the pixel located at the outer edge of target portion 150a is zero. The filter coefficients defined for the other pixels of the target portion for subzone 120a are values between 0 and Wi. The filter coefficients defined in this way are applied to the pixel data of each pixel of the target portion to generate a filtered image portion. The filter coefficients for the pixels of the other target portions for the other subzones 120 may be defined in the same manner as the filter coefficients defined for the pixels of the target portion for subzone 120a as illustrated in FIG. 9B.

[0063] Returning to FIG. 8, at step 806, image analysis circuit 340 analyzes the filtered image portions generated for each subzone 120 and determines the local luminance value of each subzone 120 based on the APL of the filtered image portion. The APL of the filtered image portion, which may also be referred to as the filtered image local APL, is the average of the pixel luminance levels of the filtered image portion. In one implementation, the local luminance value for a subzone 120 is determined to be the same as the APL of the filtered image portion generated for that subzone 120. Alternatively, the local luminance value for a subzone 120 may be determined by performing an arithmetic operation (e.g., multiplication, division, addition, subtraction, etc.) on the APL of the filtered image portion generated for that subzone 120.

[0064] FIG. 10 illustrates an overview of image processing executed in the image analysis circuit 340 according to one or more embodiments. The image analysis circuit 340 is first configured to select a target portion of the input image for each subzone 120. As discussed above, the target portion of the input image for each subzone 120 is selected such that the target portion is displayed in the corresponding region 140a of the display panel 100, as described in connection with FIG. 9A. The image analysis circuit 340 is further configured to apply a filter to the target portion selected for each subzone 120 to generate a filtered image portion. The filter may have filter coefficients defined as illustrated in FIG. 9B. The filter analysis circuit 340 is further configured to determine the local luminance value of each subzone 120 based on the APL of the filtered image portion generated for each subzone 120.

[0065] In other embodiments, the local luminance value for each subzone 120 may be determined to be the APL of the subzone 120 calculated based on the input image data. Using the APL of the subzone 120 as the local luminance value of each subzone 120 may cause an undesired change in the luminance of the display image when an image element (or object) having a high specified luminance level (e.g., the highest specified luminance level) moves vertically across the boundary of the adjacent zone 110, which may be observed as flickering of the display image. As described above, by using the filtered image portion to determine the local luminance value of each subzone 120, such an undesired change that may occur when an image element having a high luminance level moves vertically may be effectively alleviated.

[0066] Returning to FIG. 7, after determining the local luminance value of each subzone 120 in step 702, the image analysis circuit 340, in step 704, averages the local luminance values determined for each combination of two or more adjacent subzones 120 of the subzones 120 in each zone 110 to determine the averaged local luminance value of each zone 110. FIGS. 11A, 11B, and 11C illustrate examples of averaging of local luminance values according to one or more embodiments. In the examples illustrated in FIGS. 11A, 11B, and 11C, the local luminance values are averaged for each combination of two adjacent subzones 120 of each zone 110 to determine the averaged local luminance value for that zone 110. In this case, the number of averaged local luminance values for each zone 110 is one less than the number of subzones 120 within each zone 110. For example, in an implementation where the number of subzones 120 within each zone 110 is 12, the number of averaged local luminance values calculated for each zone 110 is 11.

[0067] In the example illustrated in FIG. 11A, for zone 110 1 the local luminance values of the fifth subzone 120 from the left are calculated as 0.0, 6.7, 13.3, 6.7, and 0.0, respectively, and four averaged local luminance values are determined for the fifth subzone 120 from the left. For zone 110 1 the averaged local luminance value for the leftmost and the second subzone 120 from the left is calculated as 3.4. This is approximately equal to (0.0 + 6.7) / 2. For zone 110 1 the averaged local luminance value for the second and the third subzone 120 from the left is calculated as 10.0. This is approximately equal to (6.7 + 13.3) / 2. For zone 110 1 the averaged local luminance values for the other combinations of two adjacent subzones 120 are calculated in the same manner. Further, the averaged local luminance values for the other zones 110 are for zone 110 1It is calculated in the same manner as the averaged local luminance value for. In an alternative implementation, the averaging of the local luminance values may be performed for each combination of three or more adjacent sub-zones 120 within each zone 110 to determine the averaged local luminance value for each zone 110.

[0068] Returning to FIG. 7, at step 706, the image analysis circuit 340 determines the maximum value of the averaged local luminance value for each zone 110. The columns "MAX" in FIGS. 11A, 11B, and 11C illustrate examples of the maximum values of the averaged local luminance values determined for each zone 110, respectively.

[0069] At step 708, the image analysis circuit 340 further determines the base backlight value of the light source 210 based on the maximum value of the averaged local luminance value determined for the zone 110 corresponding to the light source 210. In one implementation, the image analysis circuit 340 determines the base backlight value for each light source 210 such that the base backlight value for the target light source 210 increases as the maximum value of the averaged local luminance value determined for the zone 110 corresponding to the light source 210 increases. The base backlight value determined for each light source 210 is transferred and stored in the 1D RAM 350 (illustrated in FIG. 6).

[0070] In step 710, the backlight value generation circuit 360 receives the base backlight value for each light source 210 from the 1D RAM 350, and determines the backlight value for each light source 210 based on the base backlight value for each light source 210 and the display brightness value (DBV). In one implementation, the backlight value generation circuit 360 generates the backlight value for each light source 210 by modifying the base backlight value based on the DBV. As described above, the DBV is a value that specifies the desired display brightness level of the panel display device 1000. In one implementation, the backlight value generation circuit 360 may be configured to generate the backlight value for each light source 210 by multiplying the base backlight value by a multiplication count determined based on the DBV. The backlight value generated in this way is supplied to the 1D backlight device 200 and used to control each light source 210.

[0071] The right portions of FIGS. 11A, 11B, and 11C illustrate an example of the result of determining the backlight value for the light source 210 by the above-described process 700 in an implementation in which an input image including the image element 530 is displayed according to one or more embodiments. In the implementation illustrated in FIGS. 11A, 11B, and 11C, similar to the case illustrated in FIGS. 5A, 5B, and 5C, the image element 530 is initially located in the column of the third subzone 120 from the left of the display panel 100, and then, after crossing the boundary between the third and fourth columns of the subzone 120, it is moved inside the fourth column from the left of the subzone 120. As illustrated in FIGS. 11A, 11B, and 11C, as a result of the process 700 of determining the backlight value for each light source 210, the maximum APL of all the zones 110 is maintained at "10" during the movement of the image element 530, thereby alleviating the undesired phenomenon of the brightness of the image element 530.

[0072] FIG. 12 illustrates a configuration example of a display driver 1300 of a panel display device 1000 according to another embodiment. The display driver 1300 is configured in the same manner as the display driver 300 illustrated in FIG. 6, except that it includes a backlight control circuit 1330 instead of the backlight control circuit 330. The backlight control circuit 1330 includes an image analysis circuit 1340, a 2D RAM 1350, a 1D module 1360, and a backlight value generation circuit 1370. The image analysis circuit 1340 is configured to analyze input image data to generate local luminance values for each subzone 120. The process 800 described in connection with FIG. 8 may be used to generate the local luminance values for each subzone 120. The image analysis circuit 1340 is further configured to transfer the local luminance values generated for each subzone 120 to the 2D RAM 1350. The 2D RAM 1350 is configured to store the local luminance values generated for each subzone 120 and transfer the stored local luminance values to the 1D module 1360 sequentially. The 1D module 1360 is configured to generate a basic backlight value for each light source 210 based on the local luminance values stored in the 2D RAM 1350. The basic backlight value for each light source 210 may be generated by performing steps 704, 706, and 708 of the process 700 described in connection with FIG. 7. The backlight value generation circuit 1370 may be configured to generate a backlight value for each light source 210 by modifying the basic backlight value based on the DBV. In an embodiment where the backlight value generation circuit 1370 stores dithering data, the backlight value generation circuit 1370 may be further configured to modify the basic backlight value for each light source 210 based on the dithering data in order to alleviate display unevenness.

[0073] FIG. 13 illustrates a configuration example of a 1D module 1360 according to one or more embodiments. In the illustrated embodiment, the 1D module 1360 includes a flip-flop FF0 1361, a flip-flop FF1 1362, an averaging circuit 1363, a flip-flop FF2 1364, a maximum value circuit 1365, and a flip-flop FF3 1366. The flip-flop FF0 1361 has a data input configured to sequentially receive local luminance values from the 2D RAM 1350. The flip-flop FF1 1362 has a data input coupled to the data output of the flip-flop FF0 1361 and is configured to output the local luminance value received from the flip-flop FF0 1361 with a delay of one operation cycle (e.g., one clock cycle). The data outputs of the flip-flop FF0 1361 and the flip-flop FF1 1362 are coupled to the input of the averaging circuit 1363. The averaging circuit 1363 is configured to calculate the average of the local luminance values received from the flip-flop FF0 1361 and the flip-flop FF1 1362. The flip-flop FF2 1364 is configured to latch the output of the averaging circuit 1363 and transfer the same output to the maximum value circuit 1365. The maximum value circuit 1365 is configured to output the larger of the outputs of the flip-flop FF2 1364 and the flip-flop FF3 1366. The flip-flop 1366 is configured to latch the output of the maximum value circuit 1365.

[0074] The 1D module 1360 configured as described above sequentially receives and processes the local luminance values of each sub-zone 120 of each zone 110 and determines the base backlight value of the light source 210 corresponding to that zone 110. When the process for determining the local luminance values of the sub-zones 120 of each zone 110 is completed, the output of the flip-flop FF3 is the maximum value of the averaged local luminance values calculated for that zone 110 and is used as the base backlight value for the light source 210 corresponding to that zone 110, as will be described in detail below.

[0075] FIG. 14 is a timing diagram illustrating an operation example of the 1D module 1360 when processing the local luminance values of each sub-zone 120 for each zone 110 according to one or more embodiments. In FIG. 14, B[i] represents the local luminance value of the i-th sub-zone 120 from the left of the target zone 110, and "#i" represents the i-th operation cycle (e.g., the i-th clock cycle) in the processing for the target zone 110. Initially, the value "m" stored in the flip-flop FF3 1366 is 0.

[0076] In operation cycle #1, the 2D RAM 1350 outputs the local luminance value B[1] of the leftmost sub-zone 120. In operation cycle #2, the flip-flop FF0 1361 latches the local luminance value B[1] from the 2D RAM 1350, while the 2D RAM 1350 outputs the local luminance value B[2] of the second sub-zone 120 from the left. In operation cycle #3, the flip-flop FF1 1362 latches the local luminance value B[1] from the flip-flop FF0 1361, the flip-flop FF0 1361 latches the local luminance value B[2] from the 2D RAM 1350, while the 2D RAM 1350 outputs the local luminance value B[3] of the third sub-zone 120 from the left.

[0077] In operation cycle #4, the averaging circuit 1363 calculates the average Bave[1] of the local luminance values B[1] and B[2]. During that time, the flip-flop FF1 1362 latches the local luminance value B[2] from the flip-flop FF0 1361, the flip-flop FF0 1361 latches the local luminance value B[3] from the 2D RAM 1350, while the 2D RAM 1350 outputs the local luminance value B[4] of the fourth sub-zone 120 from the left.

[0078] In operation cycle #5, the maximum value circuit 1365 outputs the larger of the output of the averaging circuit 1363 (i.e., the average Bave[1] of the local luminance values B[1] and B[2]) and the value "m" stored in the flip-flop FF3 1366, and the value "m" stored in the flip-flop FF3 1366 is updated with the output of the maximum value circuit 1365. On the other hand, the averaging circuit 1363 calculates the average Bave[2] of the local luminance values B[2] and B[3]. Further, the flip-flop FF1 1362 latches the local luminance value B[3] from the flip-flop FF0 1361, and the flip-flop FF0 1361 latches the local luminance value B[4] from the 2D RAM 1350, while the 2D RAM 1350 outputs the local luminance value B[5] of the fifth sub-zone 120 from the left.

[0079] In subsequent operation cycles, a process similar to that executed in operation cycle #5 is repeated. This process is repeated until the maximum value of the averaged local luminance values is obtained at the output of the flip-flop FF3 1366.

[0080] The 1D module 1360 of the embodiment illustrated in FIG. 13 is configured to generate the averaged local luminance value of each zone 110 by averaging the local luminance values determined for each combination of two adjacent sub-zones 120 of that zone 110. In other embodiments, the 1D module 1360 may generate the averaged local luminance value of each zone 110 by averaging the local luminance values determined for each combination of three or more adjacent sub-zones 120 of that zone 110. In such an embodiment, the 1D module 1360 may include one or more additional flip-flops coupled in series to the output of the flip-flop FF1 1362, and the output of the additional flip-flop may be coupled to the averaging circuit 1363.

[0081] The display driver 1300 illustrated in FIG. 12 is configured to implement a local dimming function for the 1D backlight device 200 (illustrated in FIGS. 1 and 2). However, in other embodiments, the display driver may be configured to implement the local dimming function for both the 1D backlight device and the 2D backlight device. Here, the 2D backlight device refers to a backlight device including a 2D light source array in which light sources are arranged in a matrix. The display driver configuration corresponding to both the 1D backlight device and the 2D backlight device enables the display driver to be used in more display device products, effectively improving the availability of the display driver. Hereinafter, a configuration example of a display device including a 2D backlight device and a configuration example of a display driver configured to be compatible with both the 1D backlight device and the 2D backlight device will be described.

[0082] FIG. 15 illustrates a configuration example of a panel display device 2000 corresponding to a local dimming function based on a 2D light source array according to one or more embodiments. The panel display device 2000 includes a display panel 2100 and a two-dimensional (2D) backlight device 2200 configured to illuminate the display panel 2100. The display panel 2100 may be a light transmissive display panel such as, for example, a liquid crystal display (LCD) panel. The 2D backlight device 2200 includes a 2D array of light sources 2210. Each light source 2210 may include one or more LEDs or other types of light sources. Note that since the light sources 2210 are provided behind the display panel 2100 as shown in FIG. 16 illustrating the side view structure of the panel display device 2000, the light sources 2210 are illustrated by dashed lines in FIG. 15. Although 64 light sources 2210 are illustrated in FIG. 15, those skilled in the art will understand that the 2D backlight device 2200 may include fewer than 64 or more than 64 light sources 2210.

[0083] FIG. 17 illustrates an example arrangement of light sources 2210 of a 2D backlight device 2200 according to one or more embodiments. In the illustrated embodiment, the display panel 2100 is divided into zones 2110 arranged in a matrix, and the light sources 2210 are each located behind a corresponding zone 2110. The zone 2110 may have a substantially rectangular shape. In one or more embodiments, the zone 2110 has a substantially square shape so as to reduce the aspect ratio of the zone 2110. Each light source 2210 is arranged such that the projection of each light source 2210 onto the display panel 2100 is located at the center (e.g., the geometric center) of the corresponding zone of the zones 2110. As used herein, the “corresponding zone” 2110 of a light source 2210 refers to the zone 2110 that includes the projection of that light source 2210 onto the display panel 2100. It should be noted that due to the light diffusion characteristics of the light sources 2210, each light source 2210 mainly illuminates the corresponding zone 2110, but may also secondarily illuminate at least a part of the surrounding (e.g., adjacent) zones 2110 of the corresponding zone 2110.

[0084] FIG. 18 illustrates an example configuration of a display driver 2300 configured to correspond to both a 1D backlight device 200 (illustrated in FIGS. 1 and 2) and a 2D backlight device 2200 (illustrated in FIGS. 15 and 16) according to one or more embodiments. The display driver 2300 is configured in the same manner as the display driver 1300 illustrated in FIG. 12, except that the display driver 2300 includes a backlight control circuit 2330 instead of the backlight control circuit 1330.

[0085] The backlight control circuit 2330 includes an image analysis circuit 2340, a 2D RAM 2350, a 1D module 2360, and a backlight value generation circuit 2370. The image analysis circuit 2340 is configured to generate local luminance values for each sub-zone 120 of the display panel 100 based on input image data when the display driver 2300 is used in a panel display device 1000 including a 1D backlight device 200. The image analysis circuit 2340 is further configured to generate local luminance values for each sub-zone 2110 of the display panel 2100 based on input image data when the display driver 2300 is used in a panel display device 2000 including a 2D backlight device 2200. In one or more embodiments, the local luminance values for each zone 2110 of the display panel 2100 are generated by a process similar to the process 800 for generating the local luminance values of the sub-zones 120 of the display panel 100 illustrated in FIG. 8. In one implementation, the image analysis circuit 2340 is configured to select a target portion of the input image for each zone 2110 in a manner similar to that executed in step 802 of process 800, and generate a filtered image portion for each zone 2110 in a manner similar to that executed in step 804 of process 800. The image analysis circuit 2340 is further configured to determine the local luminance value for each zone 2110 based on the APL of the filtered image portion in a manner similar to that executed in step 806 of process 800. The image analysis circuit 2340 is further configured to transfer the local luminance values generated for each sub-zone 120 or each zone 2110 to the 2D RAM 2350. The 2D RAM 2350 is configured to store the local luminance values generated for each sub-zone 120 or each zone 2110, and sequentially transfer the stored local luminance values to the 1D module 2360.

[0086] The 1D module 2360 is configured to process local luminance values received from the 2D RAM 2350 according to a 1D / 2D selection signal. The 1D / 2D selection signal indicates whether the display driver 2300 is in the 1D mode or the 2D mode. The 1D mode is an operation mode used in the panel display device 1000 in which the display driver 2300 includes the 1D backlight device 200. The 2D mode is an operation mode used in the panel display device 2000 in which the display driver 2300 includes the 2D backlight device 2200. The 1D module 2360 is configured to generate a basic backlight value for the light source 210 in the same manner as performed by the 1D module 1360 described in relation to FIG. 12 when the display driver 2300 is in the 1D mode. The 1D module 2360 is further configured to output, as is, the local luminance value determined for each zone 2110 as the basic backlight value for each light source 2210 when the display driver 2300 is in the 2D mode. More specifically, in the 2D mode, the local luminance value determined for the target zone 2110 is used, as is, as the basic backlight value for the light source 2210 corresponding to that zone 2110.

[0087] FIG. 19 illustrates a configuration example of the 1D module 2360 according to one or more embodiments. The 1D module 2360 is configured in the same manner as the 1D module 1360 illustrated in FIG. 13, except that it further includes a selector 2380 configured to select between the output of the 2D RAM 2350 and the output of the flip-flop FF3 1356 according to the 1D / 2D selection signal. When the display driver 2300 is in the 1D mode as indicated by the 1D / 2D selection signal, the selector 2380 selects the output of the flip-flop FF3 1356. In this case, the base backlight value of each light source 210 is determined to be the same as the maximum value of the averaged local luminance values calculated for the zone 110 corresponding to that light source 210. When the display driver 2300 is in the 2D mode as indicated by the 1D / 2D selection signal, the selector 2380 selects the output of the 2D RAM 2350. In this case, the base backlight value for each light source 210 is determined to be the same as the local luminance value of the zone 2110 corresponding to that light source 210.

[0088] Returning to FIG. 18, the backlight value generation circuit 2370 is configured to generate the backlight value for each light source 210 of the 1D backlight device 200 or each light source 2210 of the 2D backlight device 2200 by modifying the base backlight value based on the DBV. In an embodiment where the backlight value generation circuit 2370 stores the demura data, the backlight value generation circuit 2370 may be further configured to modify the base backlight value of each light source 210 or 2210 based on the demura data in order to alleviate display unevenness.

[0089] Since the configuration of the display driver 2300 illustrated in FIG. 18 corresponds to both the 1D backlight device 200 and the 2D backlight device 2200, the usability of the display driver 2300 is effectively improved.

[0090] The use of "a", "an", "the", "at least one" and similar reference terms in the context of describing the present invention (especially in the context of the following claims) should be construed to cover both singular and plural forms unless otherwise indicated herein or clearly contradicted by the context. The use of a list of one or more items (e.g., "at least one of A and B") after the term "at least one" should be construed to mean one item selected from the listed items (A or B) or any combination of two or more of the listed items (A and B), unless otherwise described herein or clearly contradicted by the context. The terms "comprising", "having", "including" and "containing" should be construed as open-ended terms (i.e., meaning "including but not limited to") unless otherwise specified. The recitation of a range of values herein is intended to serve merely as a shorthand for referring individually to each separate value falling within the range, and each separate value is incorporated herein as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or clearly contradicted by the context. The use of any examples, or exemplary language (e.g., "such as") provided herein is merely intended to better illustrate the invention and does not limit the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

[0091] Exemplary embodiments are described herein. Variations of those exemplary embodiments will be apparent to those skilled in the art upon reading the foregoing description. The inventors expect those skilled in the art to appropriately employ such variations, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, the invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Further, any combination of the above-described elements in all possible variations thereof is included in the invention unless otherwise specifically indicated herein or otherwise clearly contradicted by context.

Claims

1. a backlight device comprising a plurality of light sources configured to respectively illuminate a plurality of zones of a display panel, the plurality of zones being aligned in a first direction, each of the plurality of zones comprising a plurality of sub-zones aligned in a second direction perpendicular to the first direction; a backlight control circuit configured to receive an input image and determine a backlight value for a target light source of the plurality of light sources that corresponds to a target zone of the plurality of zones; Equipped with determining the backlight value for the target light source; determining a local luminance value for each subzone of the zone of interest based on the input image; determining a backlight value for the target light source based on the local luminance values ​​of the subzones of the target zone; Includes Display device.

2. the plurality of zones have a substantially rectangular shape extending in the second direction; The subzones have a substantially square shape. The display device according to claim 1 .

3. Determining the local luminance value for each of the subzones comprises: selecting a target portion of the input image for each of the subzones of the target zone; filtering the portion of interest to generate a filtered image portion for each of the subzones; determining the local luminance value for each of the subzones based on the filtered image portion; Includes The display device according to claim 1 .

4. Determining the local luminance value for each of the subzones comprises: calculating an average picture level (APL) for each of said filtered image portions; determining the local luminance value for each of the subzones based on the APL; Includes The display device according to claim 3 .

5. filtering the object portion comprises applying filter coefficients to pixel luminance levels of pixels of the object portion of the input image; The filter coefficients to be applied to the pixel luminance levels of the pixels of each of the target portions selected for each of the subzones are defined in dependence on the respective distances between the pixels of each of the target portions and the centers of each of the subzones. The display device according to claim 3 .

6. Determining the backlight value for the target light source further comprises: averaging the local luminance values ​​determined for each combination of two or more adjacent subzones of the subzone to determine an average local luminance value; determining the backlight value for the target light source based on the averaged local luminance value; Includes The display device according to claim 1 .

7. Determining a backlight value for the target light source is based on a maximum of the averaged local luminance values. The display device according to claim 6.

8. a light guide plate having a major surface attached to a rear surface of the display panel; The plurality of light sources are attached to the side of the light guide plate. The display device according to claim 1 .

9. a driver circuit configured to drive a display panel based on an input image, the display panel being illuminated by a backlight device comprising a plurality of light sources arranged in a first direction, the light sources being configured to respectively illuminate a plurality of zones of the display panel, each of the plurality of zones comprising a plurality of sub-zones arranged in a second direction perpendicular to the first direction; a backlight control circuit configured to determine a backlight value for a target light source of the plurality of light sources corresponding to a target zone of the plurality of zones; Equipped with determining the backlight value for the target light source; determining a local luminance value for each subzone of the zone of interest based on the input image; determining a backlight value for the target light source based on the local luminance values ​​of the subzones of the target zone; Includes Display driver.

10. the plurality of zones have a substantially rectangular shape extending in the second direction; The subzones have a substantially square shape.

10. A display driver as claimed in claim 9.

11. Determining the local luminance value for each of the subzones comprises: selecting a target portion of the input image for each of the subzones of the target zone; filtering the portion of interest to generate a filtered image portion for each of the subzones; determining the local luminance value for each of the subzones based on the filtered image portion; Includes 10. A display driver as claimed in claim 9.

12. filtering the object portion comprises applying filter coefficients to pixel luminance levels of pixels of the object portion of the input image; The filter coefficients to be applied to the pixel luminance levels of the pixels of each of the target portions selected for each of the subzones are defined in dependence on the respective distances between the pixels of each of the target portions and the centers of each of the subzones. A display driver as claimed in claim 11.

13. Determining the backlight value for the target light source further comprises: averaging the local luminance values ​​determined for each combination of two or more adjacent subzones of the subzone to determine an average local luminance value; determining the backlight value for the target light source based on the averaged local luminance value; Includes A display driver as claimed in claim 11.

14. Determining a backlight value for the target light source is based on a maximum of the averaged local luminance values. A display driver as claimed in claim 13.

15. The backlight control circuit comprises a memory for storing local luminance values ​​for each of the sub-zones of the zone of interest.

10. A display driver as claimed in claim 9.

16. the driver circuit is configured to drive a second display panel based on a second input image; the second display panel comprises a plurality of second zones arranged in a matrix; the plurality of second zones are configured to be illuminated respectively by a plurality of second light sources; The backlight control circuit further comprises: determining second local luminance values ​​for each of the plurality of second zones based on the second input image; storing the second local luminance value in the memory; and configured to determine second backlight values ​​for the plurality of second light sources based on the second local luminance values.

16. A display driver as claimed in claim 15.

17. a backlight device including a plurality of light sources for illuminating a plurality of zones of a display panel, the plurality of zones being aligned in a first direction, each of the plurality of zones including a plurality of sub-zones aligned in a second direction perpendicular to the first direction; Receiving an input image; determining a backlight value for a target light source among the plurality of light sources that corresponds to a target zone among the plurality of zones; Including, determining the backlight value for the target light source; determining a local luminance value for each subzone of the zone of interest based on the input image; determining a backlight value for the target light source based on the local luminance values ​​of the subzones of the target zone; Includes method.

18. the plurality of zones have a substantially rectangular shape extending in the second direction; The subzones have a substantially square shape.

20. The method of claim 17.

19. Determining the local luminance value for each of the subzones comprises: selecting a target portion of the input image for each of the subzones of the target zone; filtering the portion of interest to generate a filtered image portion for each of the subzones; determining the local luminance value for each of the subzones based on the filtered image portion; Includes 20. The method of claim 17.

20. Determining the backlight value for the target light source further comprises: averaging the local luminance values ​​determined for each combination of two or more adjacent subzones of the subzone to determine an average local luminance value; determining the backlight value for the target light source based on the averaged local luminance value; Includes 20. The method of claim 19.

Images