Backlight control for display device

Abstract

SOLUTION: To provide display device comprising a backlight device and a backlight control circuit, in which: the backlight device comprises a plurality of light sources configured to illuminate a display panel; the backlight control circuit is configured to apply a filter to a target part of an input image to generate a filtered image part; the target part of the input image is displayed in a corresponding region of the display panel illuminated by a target light source of the plurality of light sources; and further the backlight control circuit is configured to control a luminance level of the target light source based on a maximum pixel luminance level of the filtered image part and a local average picture level (APL) of the filtered image part.EFFECT: Regarding a foreground object which is bright but small, unwanted reduction of a luminance level and flicker, which may occur when moving, can be effectively mitigated.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] CROSS REFERENCE TO RELATED APPLICATIONS: This application is a continuation-in-part of U.S. patent application Ser. No. 18 / 473,675, filed Sep. 25, 2023, the entire disclosure of which is incorporated herein by reference.

[0002] This application relates generally to panel displays, and more specifically to backlight control for displays. [Background technology]

[0003] Display devices that include a light-transmissive display panel, such as a light-transmissive liquid crystal display (LCD) panel, incorporate a backlight to illuminate the light-transmissive display panel. Modern backlight systems (e.g., direct-lit backlights, full-array backlights, etc.) may use an array of light sources (e.g., light-emitting diodes (LEDs), etc.) positioned behind the display panel to illuminate the display panel. The light sources may be configured to illuminate different regions of the display panel. The use of an array of light sources in a backlight facilitates local dimming to provide light and / or dark areas of the displayed image, improving image quality. 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 intended to identify key features or essential features of the present disclosure. The present disclosure may include various aspects and embodiments described below.

[0005] In an example embodiment, the present disclosure comprises a display device including a backlight device and a backlight control circuit. The backlight device comprises a plurality of light sources configured to illuminate a display panel. The backlight control circuit applies a filter to a target portion of an input image to generate a filtered image portion. The target portion of the input image is displayed on a corresponding area of ​​the display panel illuminated by a target light source of the plurality of light sources. The backlight control circuit is further configured to control a brightness level of the target light source based on a maximum pixel brightness level of the filtered image portion and a local average picture level (APL) of the filtered image portion.

[0006] In another exemplary embodiment, the present disclosure provides a display driver comprising a backlight control circuit coupled to a backlight device comprising a plurality of light sources for illuminating a display panel. The backlight control circuit is configured to apply a filter to a target portion of an input image to generate a filtered image portion. The target portion of the input image is displayed on a corresponding area of ​​the display panel illuminated by a target light source of the plurality of light sources. The backlight control circuit is further configured to control a brightness level of the target light source based on a maximum pixel brightness level of the filtered image portion and a local average picture level (APL) of the filtered image portion.

[0007] In yet another exemplary embodiment, the present disclosure provides a method. The method includes illuminating a display panel with a plurality of light sources of a backlight device. The method further includes applying a filter to a target portion of an input image to generate a filtered image portion. The target portion of the input image is displayed in a corresponding area of ​​the display panel that is illuminated by the target light source of the plurality of light sources. The method further includes controlling a luminance level of the target light source based on a maximum pixel level of the filtered image portion and a local average picture level (APL) of the filtered image portion.

[0008] Further features and aspects are described in more detail below with reference to the accompanying drawings. [Brief description of the drawings]

[0009] [Figure 1A] FIG. 1A illustrates examples of bright foreground objects of the same specified luminance level but different sizes displayed on a dark background, in accordance with one or more examples of the present disclosure.

[0010] [Figure 1B] FIG. 1B illustrates an example of a foreground object at the highest luminance level moving between adjacent zones in a dark background at the lowest luminance level, in accordance with one or more examples of the present disclosure.

[0011] [Diagram 2] FIG. 2 illustrates an example display device configuration according to one or more embodiments.

[0012] [Diagram 3] FIG. 3 is a side view illustrating an example configuration of the display device of FIG. 2 according to one or more embodiments.

[0013] [Figure 4] FIG. 4 illustrates an example arrangement of light sources according to one or more embodiments.

[0014] [Diagram 5] FIG. 5 illustrates an example display driver configuration according to one or more embodiments.

[0015] [Figure 6] FIG. 6 illustrates an example configuration of a backlight control circuit according to one or more embodiments.

[0016] [Figure 7A] FIG. 7A illustrates an example of selecting a target portion of an input image for a light source, in accordance with one or more embodiments.

[0017] [Figure 7B]FIG. 7B illustrates example filter coefficients defined for pixels in a selected target portion for a light source, according to one or more embodiments.

[0018] [Figure 8] FIG. 8 illustrates an overview of the image processing performed in the image filtering and analysis circuitry in accordance with one or more embodiments.

[0019] [Figure 9A] FIG. 9A illustrates an example of flicker mitigation in accordance with one or more embodiments.

[0020] [Figure 9B] FIG. 9B is a partial view of a display device illustrating an example arrangement of zones and corresponding light sources according to one or more embodiments.

[0021] [Figure 10] FIG. 10 illustrates an example of a relationship between the filtered image local APL and the weight assigned to the highest pixel luminance level in a target portion, in accordance with one or more embodiments.

[0022] [Figure 11] FIG. 11 illustrates an example of a relationship between a modified local APL and a base luminance level, in accordance with one or more embodiments.

[0023] [Figure 12] FIG. 12 illustrates an example of a relationship between a filtered image local APL and a boost factor in accordance with one or more embodiments.

[0024] [Figure 13A] FIG. 13A illustrates example operations for displaying a light foreground object on a dark background in accordance with one or more embodiments.

[0025] [Figure 13B]FIG. 13B illustrates example operations for displaying a grayscale image in accordance with one or more embodiments.

[0026] [Figure 14A] FIG. 14A illustrates an example image in which the "boost" feature is advantageous, in accordance with one or more embodiments.

[0027] [Figure 14B] FIG. 14B illustrates an example image with the "boost" feature disabled, in accordance with one or more embodiments.

[0028] [Figure 15] FIG. 15 illustrates an example of the configuration of a backlight control circuit according to another embodiment.

[0029] [Figure 16] FIG. 16 illustrates an example of a relationship between a global APL and a boost factor in accordance with one or more embodiments.

[0030] [Figure 17] FIG. 17 illustrates an example of the configuration of a backlight control circuit according to yet another embodiment.

[0031] [Figure 18A] FIG. 18A illustrates an example relationship between ambient light brightness levels and display brightness values ​​(DBVs) in accordance with one or more embodiments.

[0032] [Figure 18B] FIG. 18B illustrates another example of a relationship between ambient light brightness level and DBV, in accordance with one or more embodiments.

[0033] [Figure 19] FIG. 19 illustrates an example of control of the DBV depending on the environment in which the panel display device is used, according to one or more embodiments.

[0034] [Figure 20]FIG. 20 illustrates an example of the configuration of a backlight control circuit according to yet another embodiment.

[0035] [Figure 21] FIG. 21 illustrates an example of the relationship between DBV and compensation ratio, in accordance with one or more embodiments.

[0036] [Figure 22A] FIG. 22A illustrates an example relationship between compensation weights for the highest pixel luminance level and filtered image local APL when a panel display is used in a bright environment, in accordance with one or more embodiments.

[0037] [Figure 22B] FIG. 22B illustrates an example of the relationship between the compensation weights for the highest pixel luminance level and the filtered image local APL when the panel display is used in a dark environment, in accordance with one or more embodiments.

[0038] [Figure 23] FIG. 23 is a flowchart of an exemplary process for controlling a light source of a backlight device in accordance with one or more embodiments.

[0039] For ease of understanding, the same reference numbers are used, where possible, to designate identical elements common to the figures. It is anticipated that elements disclosed in one embodiment may be beneficially used in other embodiments without specific mention. Reference numbers may be subscripted to distinguish identical elements from one another. The drawings referred to herein should not be understood to be drawn to scale unless specifically noted. Also, for clarity of presentation and explanation, the drawings are often simplified and details or components are omitted. The drawings and discussion serve to explain the principles discussed below. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] The following detailed description is merely exemplary in nature and is not intended to be limiting as to the disclosure and its application and uses, nor is there any intention to be bound by any expressed or implied theory presented in the preceding background, brief description and drawings, or in the following detailed description.

[0041] 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 implemented without using these specific details. In other instances, well-known configurations are not described in detail to avoid unnecessarily complicating the description.

[0042] The term "coupled" as used herein means directly connected or connected via one or more intervening components or circuits. Additionally, ordinal numbers (e.g., first, second, third, etc.) may be used throughout the application as adjectives of elements (i.e., any nouns in the application). The use of ordinal numbers is not intended to imply or create a particular ordering of any elements, nor is it intended to limit any element to only a single element, unless expressly disclosed, for example, by the use of "before," "after," "single," and other similar terms. Rather, the use of ordinal numbers is intended to distinguish elements. For example, a first element is distinct from a second element, and a first element may include more than one element and may follow (or precede) a second element in the ordering of elements.

[0043] The present disclosure provides an apparatus and method for backlight control for a panel display device including multiple light sources (e.g., LEDs) for illuminating a display panel (e.g., an LCD panel or other light-transmissive display panel). In various implementations, a backlight array including multiple light sources may be provided behind the display panel, and the multiple light sources may be configured to respectively illuminate corresponding regions of the display panel. The brightness level of each light source may be individually controlled to achieve local dimming to provide brighter and / or darker portions of a displayed image to improve image contrast. In one implementation, the brightness of each light source may be determined based at least in part on pixel data of a set of pixels located near each light source, where the pixel data of the pixels may include shades of each color (e.g., red, green, and blue) of the pixels.

[0044] In some implementations, the luminance level of each light source may be determined based on an average picture level (APL) of a corresponding zone of the display panel illuminated by each light source. The APL may be calculated based on pixel data of pixels located in that zone of the display panel. In a typical implementation, the luminance level of each light source increases with increasing APL. However, as discussed below, a problem may arise with controlling the luminance of light sources based on the APL, in that bright but small foreground objects may be displayed at a luminance level lower than the specified luminance level.

[0045] 1A is an example of bright foreground objects (illustrated in white) of the same specified brightness level but different sizes displayed against a dark background (illustrated in black). Illustrated in FIG. 1A are four foreground objects 102, 104, 106, 108 at high specified brightness levels (e.g., the highest brightness level). Foreground object 102 is the largest and foreground object 108 is the smallest. The APL of the zone in which the largest foreground object 102 appears is relatively high, so this zone is illuminated at a high brightness level and therefore foreground object 102 can be displayed at that high specified brightness level. In contrast, the APL of the zone in which the smallest foreground object 108 appears is relatively low, so this zone is illuminated at only a low brightness level and therefore foreground object 108 can be displayed at a brightness level lower than the specified brightness level.

[0046] In other implementations, the luminance level of each light source may be determined based on the maximum pixel luminance level of the corresponding zone illuminated by each light source on the display panel, where the maximum pixel luminance level of a zone is the maximum value of the luminance levels of the pixels located in that zone. However, controlling the pixel levels of each light source based on the maximum pixel luminance level may cause flickering when a bright but small foreground object moves between zones illuminated by adjacent light sources.

[0047] FIG. 1B illustrates an example of a foreground object 112 (shown as a black circle in FIG. 1B) with the highest luminance level moving from within zone 116 to within zone 114 of the display panel 110 in a background with the lowest luminance level (shown as a white square in FIG. 1B). The top display panel and graph in FIG. 1B is at time t1, the middle display panel and graph is at time t2 following time t1, and the bottom display panel and graph is at time t3 following time t2. In FIG. 1B, three consecutive zones 114, 116, and 118 are illuminated by three consecutive light sources 124, 126, and 128 respectively located behind the zones 114, 116, and 118. It should be noted that each light source may be configured to partially illuminate the zone behind which it is located as well as the neighboring zones. Light sources 124, 126 and 128 may be configured to illuminate zones 114, 116 and 118, respectively, based on the highest pixel brightness level in zones 114, 116 and 118.

[0048] 1B, movement of the foreground object 112 may cause flickering, or an undesirable change in the brightness level of the displayed image. In this example, only light source 126 emits light when the foreground object 112 is entirely in zone 116 (e.g., at time t1), and only light source 124 emits light when the foreground object 112 is entirely in zone 114 (e.g., at time t4). While the foreground object 112 crosses the boundary between zones 114 and 116 (e.g., at time t2), both light sources 124 and 126 emit light, and thus the brightness of the displayed image may increase. The increase in brightness may be perceived by a user as flickering.

[0049] The present disclosure provides various techniques for facilitating displaying bright, but small, foreground objects at a desired luminance level while mitigating or eliminating flicker that may occur as the bright, but small, foreground objects move in a displayed image. The following is a description of embodiments of the present disclosure.

[0050] 2 illustrates an example configuration of a display device 1000 in accordance with one or more embodiments. In the illustrated embodiment, the display device 1000 includes a display panel 200 and is configured to display a desired image on the display panel 200. Although FIG. 2 illustrates the display panel 200 as having a rectangular shape with right-angled corners, the display panel 200 may have a different shape (e.g., a rectangular shape with rounded corners). The display panel 200 may be a light-transmissive display panel, such as an LCD panel.

[0051] The display device 1000 further includes a display driver 300, a backlight device 400, and a backlight driver 500. The display driver 300 is configured to drive the display panel 200 to display a desired image on the display panel 200. The backlight device 400 is configured to illuminate the display panel 200. The backlight device 400 includes an array of light sources 410. It should be noted that the light sources 410 are illustrated in dashed lines in FIG. 2 because the light sources 410 are provided behind the display panel 200. Although 64 light sources 410 are illustrated in FIG. 2, those skilled in the art will understand that the backlight device 400 may include more or less than 64 light sources 410. In an actual implementation, the backlight device 400 may include hundreds to thousands of light sources 410. In one implementation, each light source 410 may include an LED or other type of light source. In the illustrated embodiment, the light sources 410 are arranged in an array or matrix. In other embodiments, the light sources 410 may be arranged in an irregular or regular pattern. The backlight device 400 is coupled to a backlight driver 500. The backlight driver 500 is configured, under the control of the display driver 300, to drive the light sources 410 of the backlight device 400 such that each light source 410 emits light at a brightness level specified by the display driver 300.

[0052] As shown in Fig. 3, the light sources 410 are disposed behind the display panel 200 and configured to illuminate corresponding areas of the display panel 200. It should be noted that an area of ​​the display panel 200 illuminated by one light source 410 may overlap another area of ​​the display panel 200 illuminated by another light source 410. Thus, a pixel of the display panel 200 may receive light from two or more light sources 410. Although Fig. 3 illustrates four light sources 410, one skilled in the art will understand that the backlight device 400 may include more than four light sources 410.

[0053] FIG. 4 illustrates an example arrangement of light sources 410, according to one or more embodiments. In the illustrated embodiment, the display panel 200 is partitioned into rectangular zones 210 arranged in a matrix, with each light source 410 positioned behind a corresponding zone 210. In one implementation, the zones 210 are square. In other implementations, the zones 210 may be defined in different shapes such that the zones 210 completely cover the display panel 200. Each light source 410 is positioned such that the projection of each light source 410 onto the display panel 200 is located at the center (e.g., the geometric center) of a corresponding one of the zones 210. As used herein, a "corresponding zone" 210 of a light source 410 refers to the zone 210 that includes the projection of that light source 410. Each light source 410 primarily illuminates the corresponding zone 210, but may secondarily illuminate at least a portion of the surrounding (e.g., adjacent) zone 210 of the corresponding zone 210.

[0054] FIG. 5 illustrates an example configuration of a display driver 300 according to one or more embodiments. In the illustrated embodiment, the display driver 300 includes an image memory 310, an image processing circuit 320, a driving circuit 330, and a backlight control circuit 340. The image memory 310 is configured to receive an input image to be displayed on the display panel 200 from an external image source (not shown) and store the received input image. The input image is transmitted in the form of pixel data of pixels of the input image and stored in the image memory 310. In one implementation, the pixel data of each pixel includes a gradation of each primary color (e.g., red (R), green (G), and blue (B)). In one implementation, each pixel of the display panel 200 may include R, G, and B sub-pixels configured to display red, green, and blue colors, respectively, and the pixel data of each pixel may include R, G, and B gradations that specify the luminance levels of the R, G, and B sub-pixels, respectively. In other embodiments, the image memory 310 may be omitted and pixel data of the input image may be provided directly to the image processing circuitry 320 and the backlight control circuitry 340 .

[0055] The image processing circuit 320 is configured to perform image processing on the pixel data of the input image received from the image memory 310 to generate processed pixel data. The image processing performed by the image processing circuit 320 may include color adjustment, demurration correction, deburn correction, image scaling, gamma conversion, or other image processing.

[0056] The drive circuitry 330 is configured to receive the processed pixel data from the image processing circuitry 320 and drive each pixel in the display panel 200 based at least in part on the processed pixel data. In one implementation, each pixel in the display panel 200 may include R, G, and B sub-pixels, and the processed pixel data may include grayscales for the R, G, and B sub-pixels of each pixel. The drive circuitry 330 may be configured to drive or update the R, G, and B sub-pixels of each pixel based at least in part on the processed pixel data to control the luminance levels of the R, G, and B sub-pixels as specified by the processed pixel data.

[0057] The backlight control circuit 340 is configured to generate and provide backlight control commands based at least in part on the input image to the backlight driver 500 to control the brightness level of each light source 410 (shown in FIGS. 2-4 ) of the backlight device 400. The backlight control commands may include a designated brightness level for each light source 410. The backlight driver 500 is configured to drive each light source 410 to cause each light source 410 to emit light at the designated brightness level.

[0058] 6 illustrates an example of a backlight control circuit 340 in accordance with one or more embodiments. In the illustrated embodiment, the backlight control circuit 340 includes an image filtering and analysis circuit 350, a modified local APL calculation circuit 360, a base brightness level determination circuit 370, and a brightness boost circuit 380.

[0059] The image filtering and analysis circuit 350 is configured to receive an input image and perform filtering and analysis on the input image. Below is a detailed description of the functionality of the image filtering and analysis circuit 350.

[0060] The image filtering and analysis circuitry 350 is configured to select a target portion of the input image for each light source 410, such that the selected target portion of the input image for each light source 410 is displayed in a corresponding area of ​​the display panel 200 illuminated by the respective light source 410. FIG. 7A illustrates an example of selecting the target portion of the input image for light sources 410a and 410c, according to one or more embodiments. In FIG. 7A, zone 210a is the corresponding zone of light source 410a, and zone 210c is the corresponding zone of light source 410c. Zone 210b is the zone adjacent to the corresponding zone 210a of light source 410a, and zone 210d is the zone adjacent to the corresponding zone 210c of light source 410c. Light source 410b is one of the eight light sources 410 adjacent to light source 410a, and light source 410d is one of the eight light sources 410 adjacent to light source 410c.

[0061] In one implementation, a target portion of an input image for a light source 410a is selected such that the target portion is displayed in a corresponding region 420a of the display panel 200, where the corresponding region 420a is defined to be illuminated by the light source 410a. In the illustrated embodiment, the corresponding region 420a has a boundary that passes through the projections of eight light sources 410b adjacent to the light source 410a onto the display panel 200. The projections of four of the eight light sources 410b are on the four corners of the corresponding region 420a, and the projections of the remaining four adjacent light sources 410b are on the four sides of the corresponding region 420a. In the illustrated implementation, the corresponding region 420a is a square.

[0062] Similarly, a target portion of the input image for the light source 410c is selected such that the target portion is displayed in a corresponding region 420c of the display panel 200, where the corresponding region 420c is defined to be illuminated by the light source 410c. In the illustrated embodiment, the corresponding region 420c has a boundary that passes through the projections of eight light sources 410d adjacent to the light source 410c onto the display panel 200. The projections of four of the eight light sources 410d are on the four corners of the corresponding region 420c, and the projections of the remaining four adjacent light sources 410d are on the four sides of the corresponding region 420c. In the illustrated implementation, the corresponding region 420c is a square.

[0063] Target portions of the input image for the other light sources 410 may be selected in a manner similar to the target portions for light sources 410a and 410c. The target portions of each light source 410 may be selected differently, so long as the area of ​​the display panel 200 in which the selected target portion for each light source 410 is displayed encompasses at least the corresponding zone 210 of each light source 410.

[0064] It should be noted that target portions of the input image for adjacent light sources 410 may overlap one another. In the example illustrated in Figure 7A, the height and width of each target portion are both twice the height and width of the zone 210, and the target portion for light source 410a partially overlaps the target portion for its adjacent light source 410b.

[0065] Returning to Figure 6, the image filtering and analysis circuitry 350 is further configured to apply a filter to the target portion of the input image for each light source 410 to generate a filtered image portion. In one or more embodiments, the filter comprises 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 pixel data for each pixel of the target portion. In one implementation, pixel data for each pixel of the filtered image portion may be generated by multiplying pixel data for a corresponding pixel of the target portion by the filter coefficient defined for the corresponding pixel of the target portion.

[0066] FIG 7B illustrates example filter coefficients defined for pixels of a target portion for light source 410a (illustrated in FIG 7A) according to one or more embodiments. Illustrated in FIG 7B is a portion of an input image including a target portion for light source 410a. Reference numeral 430a indicates the corresponding location of light source 410a in the input image, and reference numeral 430b indicates the corresponding location of adjacent light source 410b in the input image. Reference numeral 440a indicates the outer edge of the target portion for light source 410a.

[0067] The filter coefficients defined for the pixels of the target portion for the light source 410a depend on the respective distances between the pixels of the target portion of the input image and the corresponding positions 430a of the light source 410a in the input image. In one implementation, the filter coefficients defined for the pixels of the target portion for the light source 410a increase as the respective distances between the pixels of the target portion of the input image and the corresponding positions 430a of the light source 410a in the input image decrease. In the illustrated embodiment, the filter coefficients for the pixels located at the corresponding positions 430a of the light source 410a are the maximum filter coefficients, Wi (e.g., 1.0), and the filter coefficients for the pixels located at the outer edge 440a of the target portion are 0. The filter coefficients defined for the other pixels of the target portion for the light source 410a 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 target portions for the other light sources 410 may be defined similarly to the filter coefficients defined for the pixels of the target portion for the light source 410a, as illustrated in FIG. 7B.

[0068] Returning to FIG. 6, the image filtering and analysis circuitry 350 further analyzes the filtered image portion for each light source 410 and determines the maximum pixel luminance level PL MAX and determining the APL of the filtered image portion. MAX is the maximum value of the luminance levels of the pixels in the filtered image portion. The APL of the filtered image portion, sometimes called the filtered image local APL, is the average of the pixel luminance levels in the filtered image portion. The maximum pixel luminance level PL determined for each light source 410 MAX and the filtered image local APL are supplied to a modified local APL calculation circuit 360 .

[0069] FIG. 8 illustrates an overview of the image processing performed in the image filtering and analysis circuit 350, according to one or more embodiments. The image filtering and analysis circuit 350 is configured to first select a target portion of the input image for each light source 410. As described above, the target portion of the input image for each light source 410 is selected such that the target portion is displayed in a corresponding area of ​​the display panel 200 illuminated by each light source 410, as described in relation to FIG. 7A. The image filtering and analysis circuit 350 is further configured to apply a filter to the selected target portion for each light source 410 to generate a filtered image portion. The image filtering and analysis circuit 350 further selects a maximum pixel luminance level PL for the generated filtered image portion for each light source 410. MAX and a filtered image local APL.

[0070] In one or more embodiments, the backlight control circuitry 340 determines the filtered image local APL and the maximum pixel luminance level PL of the filtered image portion generated for each light source 410. MAX The designated brightness level for each light source 410 is provided to the backlight driver 500, which controls the brightness level of each light source 410 in response to the designated brightness level. By determining the designated brightness level for each light source 410 based on the filtered image APL, a local dimming function is effectively provided, while the maximum pixel brightness level PL MAX By determining the designated brightness level based also on the maximum pixel brightness level PL, the undesired reduction in brightness levels of bright but small foreground objects can be effectively mitigated. MAX By determining the maximum pixel luminance level PL MAXis reduced when a bright but small foreground object is located at an intermediate position between adjacent light sources.

[0071] In embodiments where the target portions of the input image selected for adjacent light sources 410 overlap one another, some pixels are common to the target portions selected for the adjacent light sources 410, and two or more filter coefficients defined for the two or more light sources 410 are assigned to each of the common pixels. In such embodiments, the sum of the filter coefficients assigned to each of the common pixels may be constant. This may effectively mitigate flicker that may occur when a bright but small foreground object moves between zones illuminated by adjacent light sources. In embodiments where the filter coefficients are values ​​ranging from 0.0 to 1.0, the sum of the filter coefficients assigned to each of the common pixels may be 1.0.

[0072] 9A illustrates an example of flicker mitigation in accordance with one or more embodiments as a foreground object 450 with a maximum brightness level moves from within zone 210-3 to within zone 210-2 of display panel 200. The top display panel and graph in FIG. 11 The second display panel and graph from the top are at time t 11 Time t following 12 The second display panel and graph from the bottom are at time t 12 Time t following 13 The bottom display panel and graph are at time t 13 Time t following 14 This is in.

[0073] The left column of Figure 9A illustrates zones 210-1, 210-2, and 210-3 of display panel 200, and a bright but small foreground object 450 moving from within zone 210-3 into zone 210-2 along a trajectory 460 that passes through the centers of zones 210-1, 210-2, and 210-3. The center column of Figure 9A illustrates filter coefficients that are assigned to pixels located along trajectory 460, and the right column illustrates the luminance levels of light sources 410-1, 410-2, and 410-3, which are positioned behind zones 210-1, 210-2, and 210-3 as illustrated in Figure 9B. In one implementation, the projections of light sources 410-1, 410-2, and 410-3 onto the display panel are centered in zones 210-1, 210-2, and 210-3, respectively.

[0074] Referring again to the center column of FIG. 9A , trend line 440-2 shows filter coefficients assigned to pixels used to generate the filtered image portion for light source 410-2, and trend line 440-3 shows filter coefficients assigned to pixels used to generate the filtered image portion for light source 410-3. The filter coefficients assigned to pixels located along trajectory 460 to generate the filtered image portion for light source 410-2 increase toward the center of zone 210-2 and have a maximum value of 1.0. Similarly, the filter coefficients assigned to pixels located along trajectory 460 to generate the filtered image portion for light source 410-3 increase toward the center of zone 210-3 and have a maximum value of 1.0. In the illustrated embodiment, the sum of the filter coefficients assigned to each pixel to generate the filtered image portion for light sources 410-2 and 410-3 remains constant across the pixels located along trajectory 460. In the illustrated embodiment, the sum of the filter coefficients assigned to each pixel is held constant at 1.0.

[0075] For example, as shown in the top graph in the middle row, a pixel at location 470-1 in zone 210-3 is assigned a filter coefficient of 0.2 to generate a filtered image portion for light source 410-2, while being assigned a filter coefficient of 0.8 to generate a filtered image portion for light source 410-3. Further, as shown in the second graph from the top, a pixel at location 470-2 at the boundary between zones 210-2 and 210-3 is assigned a filter coefficient of 0.5 to generate a filtered image portion for both light sources 410-2 and 410-3. Further, as shown in the second graph from the bottom, a pixel at location 470-3 in zone 210-2 is assigned a filter coefficient of 0.66 to generate a filtered image portion for light source 410-2, while being assigned a filter coefficient of 0.34 to generate a filtered image portion for light source 410-3. Finally, as shown in the bottom graph, a pixel located at the center 470-4 of zone 210-2 is assigned a filter coefficient of 1.0 to generate the filtered image portion for light source 410-2, while being assigned a filter coefficient of 0.0 to generate the filtered image portion for light source 410-3.

[0076] The illustrated assignment of filter coefficients to each pixel effectively reduces the variation in image brightness, thereby mitigating or eliminating the occurrence of flicker. 11 When the foreground object 450 is located at the position 470-1 in FIG. 1, the maximum pixel luminance level PL MAX is approximately 20%, while the maximum pixel luminance level PL MAXThus, as shown in the top diagram in the right column of Figure 9A, light source 410-2 emits light at a brightness level of approximately 20%, and light source 410-3 emits light at a brightness level of approximately 80%.

[0077] time t 12 When the foreground object 450 is located at the position 470-2 in FIG. 1, the maximum pixel luminance level PL MAX are both approximately 50%. Thus, as shown in the second diagram from the top in the right column of Fig. 9A, both light sources 410-2 and 410-3 emit light at approximately 50% brightness level.

[0078] time t 13 When the foreground object 450 is located at the position 470-3 in FIG. 1, the highest pixel luminance level PL MAX is approximately 66%, while the maximum pixel luminance level PL MAX Therefore, as shown in the second-lowest diagram in the right column of Figure 9A, light source 410-2 emits light at a brightness level of approximately 66%, and light source 410-3 emits light at a brightness level of approximately 34%.

[0079] time t 14 When the foreground object 450 is located at the position 470-4 in FIG. 1, the highest pixel luminance level PL MAXis approximately 100%, while the maximum pixel luminance level PL MAX is approximately 0%. Thus, as shown in the bottom diagram in the right column of Figure 9A, light source 410-2 emits light at approximately 100% brightness level, and light source 410-3 emits light at approximately 0% brightness level. In this way, the sum of the brightness levels of light sources 410-2, 410-3 is kept approximately constant at approximately 100%.

[0080] Returning to FIG. 6, the modified local APL calculation circuit 360, the base luminance level determination circuit 370, and the luminance boost circuit 380 collectively determine the maximum pixel luminance level PL of the filtered image portion generated for each light source 410. MAX and forming a circuit configured to determine a designated luminance level for each light source 410 based on the filtered image local APL. The operation of the modified local APL calculation circuit 360, the base luminance level determination circuit 370, and the luminance boost circuit 380 are described in detail below.

[0081] The modified local APL calculation circuit 360 calculates the maximum pixel luminance level PL of the filtered image portion generated for each light source 410. MAX and the filtered image local APL. In one implementation, the modified local APL for each light source 410 is determined based on the maximum pixel luminance level PL MAX and the weighted average of the filtered image local APL. MAX And the weight assigned to the filtered image local APL is determined based on the filtered image local APL.

[0082] In some embodiments, the modified local APL calculation circuit 360 calculates the filtered image local APL and the maximum pixel luminance level PL MAXIn such an embodiment, the modified local APL calculation circuit 360 may include a maximum value-APL ratio lookup table (LUT) 365 that stores information indicating a relationship between the weight assigned to the filtered image local APL and the maximum pixel luminance level PL. MAX and determining weights to be assigned to the modified local APL and the highest pixel luminance level PL after filtering using the determined weights. MAX Alternatively, the calculation may be configured to calculate the weighted average of the above.

[0083] FIG. 10 illustrates a filtered image local APL and maximum pixel luminance level PL in accordance with one or more embodiments. MAX 4 illustrates an example of the relationship between the weights assigned to the filtered image local APL and the maximum pixel luminance level PL MAX It should be noted that the sum of the weights assigned to the highest pixel luminance level PL MAX The weights assigned to the filtered image local APL decrease monotonically in a broad sense. In the following, the filtered image local APL and the maximum pixel luminance level PL MAX , and the weights assigned to the

[0084] In the illustrated embodiment, when the filtered image local APL is zero, the maximum pixel luminance level PL MAX The weight assigned to is p, where p is a number between 0.0 (or 0%) and 1.0 (or 100%). If the filtered image local APL is between 0 and a predefined threshold X TH1 When the pixel luminance level is in the range between MAX The weights assigned to the highest pixel luminance level, PL MAX , which illustrates that the weights assigned to the filtered image local APL decrease linearly with increasing filtered image local APL, while the weights assigned to the highest pixel luminance level PL MAXThe weight assigned to may decrease non-linearly with increasing filtered image local APL. MAX The weights assigned to the filtered image local APL are the thresholds X TH1 When it is greater than or equal to 0.0, the weight assigned to the filtered image local APL is 1.0.

[0085] In the illustrated embodiment, the filtered image local APL is set to 0 and the threshold X TH1 If X1 is a value between MAX The weight assigned to the filtered image local APL is 0.75 (or 75%), and the weight assigned to the filtered image local APL is 0.25 (or 25%). In this case, the modified local APL is the maximum pixel luminance level PL MAX The sum of 75% of the filtered image local APL and 25% of the filtered image local APL. TH1 If X2 is greater than the maximum pixel luminance level PL MAX The weight assigned to the filtered image local APL is 0 (or 0%), and the weight assigned to the filtered image local APL is 1.0 (or 100%). In this case, the modified local APL is equal to the filtered image local APL. As described above, the modified local APL is calculated by multiplying the maximum pixel luminance level PL MAX and the filtered image local APL.

[0086] 6, the base luminance level determination circuit 370 is configured to determine a base luminance level for each light source 410 based on the modified local APL determined for each light source 410. In some embodiments, the base luminance level determination circuit 370 may include a base luminance LUT 375 that stores information indicating a relationship between the base luminance level and the modified local APL for each light source 410. In such an embodiment, the base luminance level determination circuit 370 may be configured to determine a base luminance level for each light source 410 based on the modified local APL determined for each light source 410 with reference to the base luminance LUT 375.

[0087] 11 illustrates an example of a relationship between the base luminance level and the modified local APL for each light source 410, according to one or more embodiments. The base luminance level for each light source 410 increases monotonically as the modified local APL determined for each light source 410 increases. In the illustrated embodiment, the base luminance level increases non-linearly as the modified local APL increases. In other embodiments, the base luminance level may increase linearly as the modified local APL increases. In embodiments in which the base luminance level determination circuit 370 includes a base luminance LUT 375, the base luminance LUT 375 may store values ​​of the base luminance level for corresponding values ​​of the modified local APL.

[0088] Returning to FIG. 6 , the luminance boost circuit 380 is configured to determine a designated luminance level for each light source 410 based on a base luminance level for each light source 410 and a filtered image local APL of the filtered image portion generated for each light source 410. In one or more embodiments, determining the designated luminance level for each light source 410 includes determining a boost factor based on the filtered image local APL for each light source 410 and applying the boost factor to the base luminance level for each light source 410. The boost factor determines whether or not to "boost" in determining the designated luminance level, where "boost" refers to determining the designated luminance level to be higher than the base luminance level. In the illustrated embodiment, the boost factor is determined by the filtered image local APL being greater than or equal to a threshold X TH2 It is determined that the "boost" occurs when the specified luminance level is greater than the base luminance level. TH2 If equal to or greater than 1, the boost factor is determined such that no "boosting" is performed. In this case, the specified luminance level is the same as the base luminance level. In one implementation, the specified luminance level of each light source 410 may be determined by multiplying the base luminance level by the boost factor.

[0089] The luminance boost circuit 380 may include a boost LUT 385 that stores information indicating a relationship between the boost factor and the filtered image local APL. In such an embodiment, the luminance boost circuit 380 may be configured to reference the boost LUT 385 to determine the boost factor.

[0090] 12 illustrates an example of a relationship between the boost factor and the filtered image local APL, according to one or more embodiments. The relationship illustrated in FIG. 12 may be used in an embodiment in which the designated luminance level of each light source 410 is determined by multiplying a base luminance level for each light source 410 by a boost factor. In the illustrated embodiment, the filtered image local APL is set to a threshold value X TH2≧(i.e., no “boosting” is performed), the boost factor is 1.0 (or 100%) and the filtered image local APL is greater than or equal to the threshold X TH2 (i.e., "boosting" is performed) when the boost factor is greater than 1.0 (or greater than 100%). More specifically, when the filtered image local APL is smaller than the threshold X TH3 When the local APL of the filtered image is less than or equal to the threshold X, the boost factor is a maximum value q greater than 1.0 (or 100q%). In one implementation, the maximum value q may be 3.0 (or 300%). In another implementation, the maximum value q may be a different value greater than 1.0. TH3 and threshold X TH2 When in the range between q and 1.0, the boost factor decreases from q to 1.0 as the filtered image local APL increases. Although Figure 12 illustrates the boost factor decreasing linearly from q to 1.0, the boost factor may decrease non-linearly.

[0091] The boost factor is determined to allow the specified luminance level of the light source 410 to exceed the full white luminance level for a portion of the acceptable range of the filtered image local APL generated for the light source 410, the full white luminance level being the luminance level of the light source 410 for which the pixel luminance levels of all pixels in the selected target portion for the light source 410 are at maximum luminance. In the illustrated embodiment, at least the filtered local APL exceeds the threshold X TH3 The maximum value of the boost factor, q, is determined such that the specified luminance level of light source 410 is allowed to exceed the full white luminance level when: q=0, q=1, q=2, q=3, q=4, q=5, q=6, q=7, q=8, q=9, q=10, q=11, q=12, q=13, q=14, q=15, q=16, q=17, q=18, q=19, q=20, q=21, q=22, q=23, q=24, q=25, q=26, q=27, q=28, q=29, q=30, q=31, q=32, q=33, q=34, q=35, q=36, q=37, q=38, q=39, q=40, q=41, q=42, q=43, q=44, q=45, q=46, q=47, q=48, q=50, q=51, q=52, q=53, q=54, q=55, q=60, q=71, q=82, q=92, q=103, q=114, q=125, q=135, q=146, q=157, q=160, q=171, q=182, q=215, q=225, q=23, q=24, q=25, q=39, q=45, q=51, q=260, q=271

[0092] The designated brightness level of each light source 410, determined based on the base brightness level and the boost factor, is provided to a backlight driver 500 (shown in FIG. 5 ). The backlight driver 500 drives each light source 410 to cause each light source 410 to emit light at the designated brightness level determined for each light source 410.

[0093] 13A illustrates example operations for displaying bright foreground objects, indicated by reference numbers 602, 604, 606, and 608, respectively, on a dark background, in accordance with one or more embodiments. Dashed lines 612 and 614 illustrate an example relationship between a base luminance level and a modified local APL, and solid lines 622, 624, 626, and 628 illustrate an example relationship between a specified luminance level and a modified local APL. The bright foreground objects 602, 604, 606, and 608 are of different sizes. Foreground object 602 is the smallest, and foreground object 604 is the second smallest.

[0094] In the illustrated embodiment, the maximum pixel luminance level PL MAX Since the filtered local APL is large, the bright foreground objects 602, 604 have a large modified local APL. Furthermore, since the filtered local APL is low, a "boost" is performed to display the bright foreground objects 602, 604. The "boost" facilitates displaying the small sized bright foreground objects 602, 604 at a high luminance level as desired. In the embodiment illustrated in FIG. 13A, the boost factor is 120% (or 1.2) for the bright foreground object 602 and 105% (or 1.05) for the bright foreground object 604. On the other hand, when the large sized bright foreground objects 606, 608 are displayed, the "boost" function is disabled since the filtered local APL is high. Therefore, the specified luminance levels for the bright foreground objects 606 and 608 are the same as the base luminance levels of the bright foreground objects 606 and 608, respectively.

[0095] 13B illustrates example operations for displaying grayscale images, designated 632, 634, 636, and 638, respectively, in accordance with one or more embodiments. Dashed lines 642 and 644 illustrate an example relationship between a base luminance level and a modified local APL, and solid lines 652, 654, 656, and 658 illustrate an example relationship between a specified luminance level and a modified local APL. Grayscale images 632, 634, 636, and 638 have different luminance levels. Grayscale image 632 is the darkest, and grayscale image 634 is the second darkest.

[0096] In the illustrated embodiment, the maximum pixel luminance level PL MAX Since both the filtered local APL and the filtered local APL are low, the modified local APL is low for grayscale images 632, 634. A "boost" is performed for grayscale images 632, 634, but the specified luminance level is low because the modified local APL is low. Thus, grayscale images 632, 634 are displayed at a low luminance level, as desired. On the other hand, when grayscale images 636, 638 are displayed, the "boost" function is disabled because the filtered local APL is high. Thus, the specified luminance levels for grayscale images 636, 638 are the same as the base luminance levels of grayscale images 636, 638, respectively.

[0097] 14A illustrates an example image in which a "boost" feature may be useful, in accordance with one or more embodiments. The "boost" feature is useful when displaying images in which bright but small foreground objects are displayed, such as the fireworks image shown. The "boost" feature allows the bright but small foreground objects to be displayed with a desired high brightness.

[0098] 14B illustrates an example image in which the "boost" function is disabled, according to one or more embodiments. The "boost" function does not operate when images with small changes in luminance levels, such as landscape images, are displayed. When the "boost" function is disabled, local dimming is performed based on the filtered image local APL to improve image contrast.

[0099] 15 illustrates an example of a configuration of a backlight control circuit 1340 according to another embodiment. The backlight control circuit 1340 is configured similarly to the backlight control circuit 340 illustrated in FIG. 6, except that the backlight control circuit 1340 includes a luminance boost circuit 1380 instead of the luminance boost circuit 380 and additionally includes a global APL calculation circuit 1390. The global APL calculation circuit 1390 is configured to calculate a global APL, which is the APL (or an average of pixel luminance levels) of the entire input image. The global APL calculation circuit 1390 is further configured to provide the global APL to the luminance boost circuit 1380.

[0100] The luminance boost circuit 1380 is configured to determine the designated luminance level for each light source 410 in a manner similar to the luminance boost circuit 380 illustrated in FIG. 6, except that the luminance boost circuit 1380 uses a global APL instead of a filtered image local APL. In one or more embodiments, the luminance boost circuit 1380 is configured to determine a boost factor based on the global APL and apply the boost factor to a base luminance level for each light source 410. In one implementation, the designated luminance level for each light source 410 may be determined by multiplying the base luminance level by the boost factor. The luminance boost circuit 1380 may include a boost LUT 1385 that stores information indicating a relationship between the boost factor and the global APL. In such an embodiment, the luminance boost circuit 1380 may be configured to determine the boost factor with reference to the boost LUT 1385. Determining the boost factor using the global APL instead of the filtered image local APL is useful for appropriately determining the boost factor when a bright foreground image having a size larger than the target portion of the input image for each light source 410 is displayed on the display panel 200.

[0101] 16 illustrates an example of a relationship between a boost factor and a global APL, according to one or more embodiments. The relationship illustrated in FIG. 16 may be used in an embodiment in which the designated luminance level of each light source 410 is determined by multiplying the base luminance level of each light source 410 by a boost factor. In the illustrated embodiment, the global APL is set to a threshold value X TH4 When it is equal to or greater than the threshold value X (i.e., when no “boost” is being performed), the boost factor is 1.0 (or 100%) and the global APL is equal to or greater than the threshold value X TH4 (i.e., "boosting" is performed), and greater than 1.0 (or greater than 100%). More specifically, the boost factor is the factor when the global APL is greater than or equal to the threshold X TH5 The maximum value q (or 100q%) is when the global APL is less than or equal to the threshold value X, where q is a value greater than 1. In one implementation, the maximum value q may be 3.0 (or 300%). In other implementations, the maximum value q may be other values ​​greater than 1.0.TH5 and threshold X TH4 When in the range between q and 1.0, the boost factor decreases from q to 1.0 as the global APL increases. Although Figure 16 illustrates the boost factor decreasing linearly from q to 1.0, the boost factor may decrease non-linearly.

[0102] FIG. 17 illustrates an example of the configuration of a backlight control circuit 2340 according to yet another embodiment. The backlight control circuit 2340 is configured similarly to the backlight control circuit 340 illustrated in FIG. 6, except that the backlight control circuit 2340 further includes a brightness adjustment circuit 2310 configured to adjust the designated brightness level of each light source 410 based on a display brightness value (DBV). The DBV here is a value that specifies the desired display brightness level of the display device 1000, and the display brightness level here is the overall brightness level of the display image displayed on the display panel 200. In the illustrated embodiment, the backlight control circuit 2340 further includes a DBV determination circuit 2320 configured to determine the DBV based on the ambient light brightness level LUX measured by the ambient light sensor 2330. In other embodiments, the DBV may be generated by a controller outside the display driver 300. The DBV may be generated based on a user operation in addition to the ambient light brightness level LUX. For example, when a command to adjust the display brightness level of the display device 1000 is manually input to an input device, the DBV may be generated based on this command.

[0103] 18A illustrates an example relationship between ambient light luminance level LUX and DBV, according to one or more embodiments. In the illustrated embodiment, DBV increases monotonically with increasing ambient light luminance level LUX. Although FIG. 18A illustrates DBV increasing linearly with increasing ambient light luminance level LUX, DBV may increase non-linearly with increasing ambient light luminance level LUX.

[0104] FIG. 18B illustrates another example of a relationship between the ambient light luminance level LUX and DBV, according to one or more embodiments. In one or more embodiments, the DBV increases stepwise with increasing ambient light luminance level. In the illustrated embodiment, the DBV has a hysteretic dependence on the ambient light luminance level LUX. More specifically, the DBV increases with increasing ambient light level LUX. 1U While the DBV increases from VL1 to VL2 at the ambient light level L 1U Lower L 1D Similarly, for j ≥ 2 and ≤ 5, the DBV decreases with increasing ambient light level L jU In VL j From VL j+1 while DBV increases with the ambient light level L jU Lower L jD In VL j+1 From VL j decreases to.

[0105] Returning to FIG. 17, the backlight control circuit 2340 may be configured to generate a designated brightness level for each light source 410 by modifying a base brightness level for each light source 410 by the brightness boost circuit 380 and the brightness adjustment circuit 2310. In one or more embodiments, the brightness boost circuit 380 may be configured to determine a boost factor based on a filtered image local APL for each light source 410, and the brightness adjustment circuit 2310 may be configured to determine a brightness adjustment factor based on the DBV. The boost factor may be determined with reference to the boost LUT 385 as described in connection with FIG. 6 and FIG. 12. The brightness adjustment factor may be determined such that the brightness adjustment factor increases as the DBV increases. The backlight control circuit 2340 may be configured to generate a designated brightness level for each light source 410 by applying the boost factor and the brightness adjustment factor to a base brightness level for each light source 410. In one implementation, the backlight control circuit 2340 may be configured to generate a designated brightness level for each light source 410 by multiplying a base brightness level for each light source 410 by a boost factor and further multiplying the result by a brightness adjustment factor. By determining the designated brightness level using the boost factor, a "boost" function can be realized as described above in relation to Figures 6 and 12. By determining the designated brightness level using the brightness adjustment factor, the display brightness level of the panel display device can be adjusted to improve the visibility of an image displayed on the display panel 200. In particular, in an implementation in which the DBV is determined based on the ambient light brightness level LUX, the display brightness level of the panel display device can be appropriately adjusted by using the brightness adjustment factor determined based on the DBV, taking into account the ambient light brightness level LUX.

[0106] 19 illustrates an example of control of DBV according to an environment in which a panel display device is used, according to one or more embodiments. In a bright environment (e.g., a sunny environment), the DBV is determined to be a "high" value in response to a high ambient light luminance level LUX. In a medium luminance environment (e.g., a cloudy environment), the DBV is determined to be a "medium" value lower than the "high" value in response to a medium ambient light luminance level LUX. In a dark environment (e.g., a nighttime environment), the DBV is determined to be a "low" value lower than the "medium" value in response to a low ambient light luminance level LUX.

[0107] The designated brightness level of each light source 410 is adjusted depending on the DBV to adjust the display brightness level of the panel display depending on the ambient light brightness level LUX. In a bright environment, the designated brightness level of each light source 410 is increased in response to an increase in the DBV to display an image at an increased display brightness level. In a dark environment, the designated brightness level of each light source 410 is decreased in response to a decrease in the DBV to display an image at a decreased display brightness level.

[0108] Furthermore, when a small, bright foreground object is displayed on a dark background image, the designated brightness level of one or more light sources 410 that illuminate the area of ​​the display panel 200 where the small, bright foreground object is displayed is increased. However, this may result in a halo effect (or halation) when the display device is used in a dark environment, because the light emitted from the one or more light sources 410 may leak into the area around the small, bright foreground object, and human vision is sensitive to leaking light in a dark environment.

[0109] When a "boost" function is implemented to facilitate displaying small, bright foreground objects at a desired high brightness level as described in connection with Fig. 14A, the halo effect may be undesirably intensified. The boost function increases the brightness level of one or more light sources that illuminate the area in which the small, bright foreground object is displayed, which may increase light leakage into the area surrounding the small, bright foreground object and intensify the halo effect. In the following, embodiments are described for mitigating the halo effect that may occur when a small, bright foreground object is displayed on a dark background image in a dark environment.

[0110] 20 illustrates an example of the configuration of a backlight control circuit 3340 according to yet another embodiment. The backlight control circuit 3340 has a similar configuration to the backlight control circuit 2340 illustrated in FIG. 17, except that the backlight control circuit 3340 includes a compensation ratio determination circuit 3350 and a modified local APL calculation circuit 3360 instead of the modified local APL calculation circuit 360.

[0111] The compensation ratio determination circuit 3350 is configured to determine a compensation ratio based on the DBV received from the DBV generation circuit 2320. As discussed in more detail below, the compensation ratio is used to suppress the luminance level of one or more light sources that illuminate areas of the display panel 200 where small, bright foreground objects are displayed when the display device is used in a dark environment. In one implementation, the compensation ratio determination circuit 3350 may include a compensation ratio LUT 3355 that includes information indicating a relationship between the DBV and the compensation ratio, and may be configured to determine the compensation ratio based on the DBV by referring to the compensation ratio LUT 3355. The compensation ratio is provided to the modified local APL calculation circuit 3360.

[0112] 21 illustrates an example of a relationship between DBV and compensation ratio in accordance with one or more embodiments. In the illustrated embodiment, the DBV is a threshold DBV TH When the compensation ratio increases with increasing DBV, the compensation ratio increases when the DBV is smaller than the threshold DBV THWhen the DBV is equal to or greater than the threshold DBV, the compensation ratio is fixed at 1.0. TH Although the compensation ratio is illustrated as increasing linearly with increasing DBV when DBV is less than the threshold DBV, the compensation ratio may increase non-linearly. Of course, the disclosed embodiments are not limited to the above embodiments. TH It is anticipated that DBV may be clamped to a value other than 1.0 when

[0113] Returning to FIG. 20, the modified local APL calculation circuit 3360 receives the compensation ratio from the compensation ratio determination circuit 3350 and calculates the maximum pixel luminance level PL of the filtered image portion generated for each light source 410. MAX and the filtered image local APL, while determining the modified local APL by taking into account the highest pixel luminance level PL MAX In some embodiments, the modified local APL calculation circuit 3360 is configured to use the compensation ratio to modify the weight assigned to the maximum pixel luminance level PL based on the filtered image local APL using the maximum-APL ratio LUT 365 as described in connection with FIG. MAX and determines the weighting to be assigned to the maximum pixel luminance level PL MAX The weights thus determined for the maximum pixel luminance level PL may be modified based on the compensation ratio. MAX The weights for the maximum pixel luminance level PL MAX In one implementation, the modified local APL calculation circuit 3360 originally calculates the maximum pixel luminance level PL MAX The maximum pixel luminance level PL is calculated by multiplying the weight assigned to MAX The modified local APL calculation circuit 3360 may be further configured to calculate a compensated weight for the pixel luminance level PL MAXThe modified local APL calculation circuit 3360 may be further configured to determine the compensated weight for the filtered image local APL by subtracting the compensated weight for the maximum pixel luminance level PL MAX Based on the compensation weights determined for the filtered image local APL and the filtered image local APL, the modified local APL is calculated as the maximum pixel luminance level PL MAX and the filtered image local APL.

[0114] FIG. 22A illustrates a maximum pixel luminance level PL when a panel display is used in a bright environment, according to one or more embodiments. MAX 1 illustrates an example of a relationship between the compensated weights and the filtered image local APL for . In an embodiment in which the DBV is determined based on the ambient light luminance level LUX, when the display device is used in a bright environment, the DBV is set to a threshold DBV TH In this case, the compensation ratio may be determined to be 1.0 (see FIG. 21), and the maximum pixel luminance level PL MAX The compensated weights determined for the maximum pixel luminance level PL MAX may be determined to be the same as the weight assigned to

[0115] FIG. 22B illustrates the maximum pixel luminance level PL when the panel display is used in a dark environment, according to one or more embodiments. MAX 1 illustrates an example of a relationship between the compensated weights and the filtered image local APL for . In an embodiment in which the DBV is determined based on the ambient light luminance level LUX, when the display device is used in a dark environment, the DBV is set to a threshold DBV TH In this case, the maximum pixel luminance level PL MAX The weights assigned to the maximum pixel luminance level PL MAX The compensated weights determined for the maximum pixel luminance level PL MAXThis suppresses the halo effect that can occur when small, bright foreground objects are displayed against a dark background image because the weight assigned to the highest pixel luminance level PL MAX is the parameter that determines the brightness level of one or more light sources 410 that illuminate the area of ​​the display panel 200 where small, bright foreground objects are displayed.

[0116] Figure 23 is a flow chart of an exemplary process 1700 for controlling a light source of a backlight device, according to one or more embodiments. Process 1700 may be performed by the display device 1000 illustrated in Figures 2 and 3, and in particular by the display driver 300 illustrated in Figure 5. However, it will be appreciated that process 1700 may be performed using a display device having additional and / or fewer components than those illustrated in Figures 2 and 3, any of the following steps may be performed in any suitable order, and process 1700 may be performed in any suitable environment.

[0117] In one or more embodiments, the process 1700 includes, at step 1702, updating a display panel (e.g., the display panel 200 shown in FIGS. 2, 3, and 5) based on the input image. The process 1700 further includes, at step 1704, illuminating the display panel with a plurality of light sources (e.g., the light sources 410 shown in FIGS. 2 and 3) of a backlight device (e.g., the backlight device 400 shown in FIGS. 2, 3, and 5). The process 1700 further includes, at step 1706, applying a filter to a target portion of the input image to generate a filtered image portion. The target portion of the input image is displayed in a corresponding region of the display panel illuminated by a target light source of the plurality of light sources (e.g., the regions 420a and 420c shown in FIG. 7A). The process 1700 further includes, at step 1708, controlling a brightness level of the target light source based on a maximum pixel brightness level of the filtered image portion and a local average picture level (APL) of the filtered image portion.

[0118] All references cited in this specification, including published applications, patent applications, and patents, are hereby incorporated by reference to the same extent as if each reference was individually and specifically indicated to be incorporated by reference and was set forth in its entirety herein.

[0119] The use of "a", "an", "the", "at least one" and similar reference words in the context of describing the present invention (particularly in the context of the claims below) should be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The use of a list of one or more items (e.g., "at least one of A and B") following 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 indicated herein or clearly contradicted by context. The terms "comprise", "have", "include" and "include" are to be construed as open-ended terms (i.e., meaning "including, but not limited to"), unless otherwise indicated. The recitation of ranges of values ​​herein is intended merely to serve as a shorthand method for individually referring to each individual value falling within the range, and each individual value is incorporated herein as if set forth individually herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or clearly contradicted by context. Any examples provided herein, or the use of exemplary language (e.g., "such as"), are intended merely to better illustrate the invention and do 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.

[0120] Exemplary embodiments are described herein. Variations of those exemplary embodiments will become apparent to those skilled in the art upon reading the foregoing description. The inventors expect that those skilled in the art will adopt such variations as appropriate, and the inventors do not intend to practice the invention otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.

Claims

1. a backlight device comprising a plurality of light sources configured to illuminate a display panel; applying a filter to a target portion of an input image to generate a filtered image portion, the target portion of the input image being displayed in a corresponding area of ​​a display panel illuminated by a target light source from the plurality of light sources; a backlight control circuit configured to control a luminance level of the target light source based on a maximum pixel luminance level of the filtered image portion and a local average picture level (APL) of the filtered image portion; Equipped Display device.

2. the filter comprises a filter coefficient assigned to each pixel of the target portion of the input image; applying the filter to the target portion of the input image comprises applying the filter coefficients to pixel luminance levels of the pixels in the target portion of the input image; The filter coefficients are defined in dependence on respective distances between the pixels of the target portion of the input image and corresponding positions of the target light source in the input image. The display device according to claim 1 .

3. controlling the brightness level of the target light source calculating a modified local APL as a weighted average of the maximum pixel luminance level of the filtered image portion and the local APL of the filtered image portion; determining the brightness level of the target light source based on the modified local APL; Includes The display device according to claim 1 .

4. Calculating the modified local APL, determining a weight to be assigned to the highest pixel luminance level; calculating the weighted average using the determined weights; Includes The display device according to claim 3 .

5. Determining a weight assigned to the highest pixel luminance level is based on the local APL of the filtered image portion. The display device according to claim 4.

6. Determining the weight assigned to the highest pixel luminance level is further based on a display luminance level (DBV) of the display device. The display device according to claim 4.

7. further comprising an ambient light sensor for measuring an ambient light brightness level; The DBV is determined based on the ambient light luminance level. The display device according to claim 6.

8. determining the brightness level of the target light source based on the modified local APL; determining a base luminance level based on the modified local APL; determining a boost factor based on the local APL of the filtered image portion; determining the luminance level of the target light source based on the base luminance level and the boost factor such that the luminance level of the target light source is higher than the base luminance level when the local APL of the filtered image portion is lower than a threshold value. The display device according to claim 3 .

9. Calculating the modified local APL, determining a weight to be assigned to the highest pixel luminance level based on the local APL of the filtered image portion; calculating the weighted average using the determined weights; Includes The display device according to claim 8.

10. determining the luminance level of the target light source includes multiplying the base luminance level by the boost factor; Determining the boost factor includes determining the boost factor such that the boost factor is greater than 1 when the local APL of the filtered image portion is less than the threshold. The display device according to claim 8.

11. The boost factor is determined to allow the luminance level of the target light source to exceed an all-white luminance level, the luminance level of the target light source being based on pixel luminance levels of all pixels of the target portion of the input image having a maximum pixel luminance level. The display device according to claim 8.

12. determining the brightness level of the target light source based on the modified local APL; determining a base luminance level based on the modified local APL; determining a boost factor based on an overall global APL of the input image; determining the luminance level of the target light source based on the base luminance level and the boost factor such that the luminance level of the target light source is higher than the base luminance level when the global APL of the input image is lower than a threshold value; The display device according to claim 3 .

13. determining the luminance level of the target light source includes multiplying the base luminance level by the boost factor; Determining the boost factor includes determining the boost factor such that the boost factor is greater than 1 when the global APL of the input image is less than the threshold. The display device according to claim 12.

14. a backlight control circuit coupled to a backlight device having a plurality of light sources for illuminating a display panel; The backlight control circuit, applying a filter to a target portion of an input image to generate a filtered image portion, the target portion of the input image being displayed in a corresponding area of ​​a display panel illuminated by a target light source from the plurality of light sources; configured to control a luminance level of the target light source based on a maximum pixel luminance level of the filtered image portion and a local average picture level (APL) of the filtered image portion. Display driver.

15. the filter comprises a filter coefficient assigned to each pixel of the target portion of the input image; applying the filter to the target portion of the input image comprises applying the filter coefficients to pixel luminance levels of the pixels in the target portion of the input image; The filter coefficients are defined in dependence on respective distances between the pixels of the target portion of the input image and corresponding positions of the target light source in the input image. A display driver as claimed in claim 14.

16. controlling the brightness level of the target light source calculating a modified local APL as a weighted average of the maximum pixel luminance level and the local APL of the filtered image portion; determining the brightness level of the target light source based on the modified local APL; 16. A display driver as claimed in claim 15.

17. Calculating the modified local APL, determining a weight to be assigned to the highest pixel luminance level; calculating the weighted average using the determined weights; 17. A display driver as claimed in claim 16.

18. Determining a weight assigned to the highest pixel luminance level is based on the local APL of the filtered image portion.

18. A display driver as claimed in claim 17.

19. Determining the weight assigned to the highest pixel luminance level is further based on the DBV of the display device.

18. A display driver as claimed in claim 17.

20. Illuminating a display panel with a plurality of light sources of a backlight device; applying a filter to a target portion of an input image to generate a filtered image portion, the target portion of the input image being displayed in a corresponding area of ​​a display panel illuminated by a target light source from the plurality of light sources; controlling a luminance level of the target light source based on a maximum pixel luminance level of the filtered image portion and a local average picture level (APL) of the filtered image portion; Includes method.

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