Luminance control of backlight in display of image

An image display method includes generating luminance data, applying a special filter to the luminance data, generating luminance setting data, generating gradation setting data, and controlling a backlight based on the luminance setting data and a liquid crystal panel based on the gradation setting data. The luminance data indicates a luminance value for each of light-emitting regions of the backlight based on a maximum gradation value among gradation values of image pixels of an input image that correspond to the light-emitting region. The special filter is applied such that, with respect to each light-emitting region, a difference of the luminance value thereof from the luminance values of neighboring light-emitting regions decreases, and the luminance setting data is generated therefrom. The gradation setting data sets a gradation value of each pixel of the liquid crystal panel, and is generated based on the input image and the luminance setting data.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2021-030120, filed on Feb. 26, 2021; and Japanese Patent Application No. 2021-185559, filed on Nov. 15, 2021; the entire contents of which are incorporated herein by reference.

FIELD

Embodiments relate to an image display method and a display that performs the same.

BACKGROUND

A conventionally-known image display device includes a backlight and a liquid crystal panel. The backlight includes multiple light-emitting regions arranged in a matrix configuration and light sources in the light-emitting regions. The liquid crystal panel is located above the backlight and includes multiple pixels. By using such an image display device, luminances of the light-emitting regions can be set differently depending on the image to be displayed on the liquid crystal panel. Also, gradations of the pixels of the liquid crystal panel can be set according to the set luminances of the light-emitting regions. The contrast of the image can be improved thereby. Such technology is called “local dimming”.

A backlight that is used for the local dimming may have a structure in which light can propagate (i.e., leak) between the adjacent light-emitting regions. When a backlight having such a structure is used for the local dimming, the leakage of the light becomes more significant and thus noticeable by users as a difference between setting values of luminances of the adjacent light-emitting regions increases. Such a phenomenon is called a “halo phenomenon”.

SUMMARY

Embodiments are directed to an image display method and a display in which the halo phenomenon can be suppressed.

An image display method includes generating luminance data, applying a special filter to the luminance data, generating luminance setting data, generating gradation setting data, and controlling a backlight to operate based on the luminance setting data and a liquid crystal panel to operate based on the gradation setting data to display an image corresponding to an input image. The luminance data indicates a luminance value for each of a plurality of light-emitting regions of the backlight, which is configured in a matrix form, based on a maximum gradation value among gradation values of image pixels of the input image that correspond to the light-emitting region. The special filter is applied to the luminance data, such that, with respect to each of the light-emitting regions, a difference of the luminance value thereof from the luminance values of neighboring light-emitting regions thereof decreases, and the luminance setting data is generated therefrom. The gradation setting data sets a gradation value of each of a plurality of pixels of the liquid crystal panel, which is coupled to the backlight, for the input image, and is generated based on the input image and the luminance setting data.

According to embodiments, the halo phenomenon can be suppressed.

DETAILED DESCRIPTION

Exemplary embodiments will now be described with reference to the drawings. The drawings are schematic or conceptual; and the relationships between the thickness and width of portions, the proportional coefficients of sizes among portions, etc., are not necessarily the same as actual values thereof. Furthermore, the dimensions and proportional coefficients may be illustrated differently among drawings, even for identical portions. In the specification and the drawings of the application, components similar to those described in regard to a drawing hereinabove are marked with like reference numerals, and a detailed description is omitted as appropriate.

For easier understanding of the following description, arrangements and configurations of portions of an image display device are described using an XYZ orthogonal coordinate system. X-axis, Y-axis, and Z-axis are orthogonal to each other. The direction in which the X-axis extends is referred to as an “X-direction”; the direction in which the Y-axis extends is referred to as a “Y-direction”; and the direction in which the Z-axis extends is referred to as a “Z-direction”. For easier understanding of the description, the Z-direction is called up, and the opposite direction is called down, but these directions are independent of the direction of gravity. For easier understanding of the description of the drawings, the X-axis direction in the direction of the arrow is referred to as the “+X direction”; and the opposite direction is referred to as the “−X direction”. Similarly, the Y-axis direction in the direction of the arrow is referred to as the “+Y direction”; and the opposite direction is referred to as the “−Y direction”.

First Embodiment

First, a first embodiment will be described.

FIG.1illustrates an exploded perspective view of an image display device according to the first embodiment.

An image display device100according to the first embodiment is, for example, a liquid crystal module (LCM) used in the display of a device such as a television, a personal computer, a game machine, etc. The image display device100includes a backlight110, a driver120for the backlight, a liquid crystal panel130, a driver140for the liquid crystal panel, and a controller150. Components of the image display device100will be described hereinafter. For easier understanding of the description, the electrical connections between the components are shown by connecting the components to each other with solid lines inFIG.1.

The backlight110is compatible with local dimming. The backlight110includes a planar light source111, and an optical member118located on the planar light source111.

Although not particularly limited, the optical member118is, for example, a sheet, a film, or a plate that has a light-modulating function such as a light-diffusing function, etc. According to the present embodiment, the number of the optical members118included in the backlight110is one. However, the number of optical members included in the backlight may be two or more.

FIG.2illustrates a top view of the planar light source111of the backlight110included in the image display device100according to the first embodiment.

FIG.3illustrates a cross-sectional view of the planar light source111along line III-III inFIG.2.

According to the first embodiment as shown inFIGS.2and3, the planar light source111includes a substrate112, a light-reflective sheet112s, a light guide member113, multiple light sources114, a light-transmitting member115, a first light-modulating member116, and a light-reflecting member117.

The substrate112is a wiring substrate that includes an insulating member, and multiple wiring located in the insulating member. According to the present embodiment, the shape of the substrate112in top-view is substantially rectangular as shown inFIG.2. However, the shape of the substrate is not limited to the aforementioned shape. The upper surface and the lower surface of the substrate112are flat surfaces and are substantially parallel to the X-direction and the Y-direction.

As shown inFIG.3, the light-reflective sheet112sis located on the substrate112. According to the present embodiment, the light-reflective sheet112sincludes a first adhesive layer, a light-reflecting layer on the first adhesive layer, and a second adhesive layer on the light-reflecting layer. The light-reflective sheet112sis adhered to the substrate112with the first adhesive layer.

The light guide member113is located on the light-reflective sheet112s. At least a portion of the lower surface of the light guide member113is adhered to the light-reflective sheet112swith the second adhesive layer. According to the present embodiment, the light guide member113is plate-shaped. The thickness of the light guide member113is favorably, for example, not less than 200 μm and not more than 800 μm. In the thickness direction, the light guide member113may include a single layer or may include a stacked body of multiple layers. According to the present embodiment, the shape of the light guide member113in top-view is substantially rectangular as shown inFIG.2. However, the shape of the light guide member is not limited to the aforementioned shape.

For example, a thermoplastic resin such as acrylic, polycarbonate, cyclic polyolefin, polyethylene terephthalate, polyester, or the like, an epoxy, a thermosetting resin such as silicone or the like, and glass, etc., can be used as a material used for the light guide member113.

Multiple light source placement portions113aare located in the light guide member113. The multiple light source placement portions113aare arranged in a matrix configuration in top-view. According to the present embodiment as shown inFIG.3, each light source placement portion113ais a through-hole that extends through the light guide member113in the Z-direction. Alternatively, the light source placement portion113amay be a bottomed recess located at the lower surface of the light guide member113.

The light sources114are located in the light source placement portions113a, respectively. Accordingly, as shown inFIG.2, multiple light sources114also are arranged in a matrix configuration. However, it is not always necessary for the light guide member113to be included in the planar light source111. For example, the planar light source111may not include a light guide member, and the multiple light sources114may simply be arranged in a matrix configuration on the substrate112. When no light guide member is included, the light source placement portion refers to a portion of the substrate112in which the light source114is located.

Each light source114may be a single light-emitting element or may include a light-emitting device in which, for example, a wavelength conversion member or the like is combined with a light-emitting element. According to the present embodiment as shown inFIG.3, each light source114includes a light-emitting element114a, a wavelength conversion member114b, a second light-modulating member114h, and a third light-modulating member114i.

The light-emitting element114ais, for example, an LED (Light-Emitting Diode) and includes a semiconductor stacked body114cand a pair of electrodes114dand114ethat electrically connects the semiconductor stacked body114cand the wiring of the substrate112. Through-holes are provided in portions of the light-reflective sheet112spositioned directly under the electrodes114dand114e. Conductive members112mthat electrically connect the substrate112and the electrodes114dand114eare located in the through-holes.

The wavelength conversion member114bincludes a light-transmitting member114fthat covers an upper surface and side surfaces of the semiconductor stacked body114c, and a wavelength conversion substance114gthat is located in the light-transmitting member114fand converts the wavelength of the light emitted by the semiconductor stacked body114cinto a different wavelength. The wavelength conversion substance114gis, for example, a phosphor.

According to the present embodiment, the light-emitting element114aemits blue light. On the other hand, the wavelength conversion member114bincludes, for example, a phosphor that converts incident light into red light (hereinbelow, called a red phosphor) such as a CASN-based phosphor (e.g., CaAlSiN3:Eu), a quantum dot phosphor (e.g., AgInS2or AgInSe2), a KSF-based phosphor (e.g., K2SiF6:Mn), a KSAF-based phosphor (e.g., K2(Si, Al)F6:Mn, and more specifically K2Si0.99Al0.01F5.99:Mn), or the like, a phosphor that converts incident light into green light (hereinbelow, called a green phosphor) such as a phosphor that has a perovskite structure (e.g., CsPb (F, Cl, Br, I)3), a quantum dot phosphor (e.g., CdSe or InP), a β-sialon-based phosphor (e.g., (Si, Al)3(O, N)4:Eu), a LAG-based phosphor (e.g., Lu3(Al, Ga)5O12:Ce), etc. Thereby, the backlight110can emit white light, which is a combination of the blue light emitted by the light-emitting element114aand the red light and the green light from the wavelength conversion member114b. The wavelength conversion member114bmay be a light-transmitting member that does not include any phosphor; in such a case, for example, a similar white light can be obtained by providing a phosphor sheet that includes a red phosphor and a green phosphor on the planar light source, or by providing a phosphor sheet including a red phosphor and a phosphor sheet including a green phosphor on the light guide member.

It is favorable for the KSAF-based phosphor to include the composition of the following Formula (I).
M2[SipAlqMnrFs]  (I)

In Formula (I), M is an alkaline metal; it is favorable for M to include at least K. It is favorable for Mn to be a tetravalent Mn ion. It is favorable for p, q, r, and s to satisfy 0.9≤p+q+r≤1.1, 0<q≤0.1, 0<r≤0.2, and 5.9≤s≤6.1. It is more favorable for 0.95≤p+q+r≤1.05 or 0.97≤p+q+r≤1.03; and for 0<q≤0.03, 0.002≤q≤0.02, or 0.003≤q≤0.015; and for 0.005≤r≤0.15, 0.01≤r≤0.12, or 0.015≤r≤0.1; and for 5.92≤s≤6.05 or 5.95≤s≤6.025. The compositions of K2[Si0.946Al0.005Mn0.049F5.995], K2[Si0.942Al0.008Mn0.050F5.992], and K2[Si0.939Al0.014Mn0.047F5.986] are examples. According to such a KSAF-based phosphor, a red light that has high luminance and a narrow width at half maximum of the light emission peak wavelength can be obtained.

The second light-modulating member114his located at an upper surface of the wavelength conversion member114band can modify the amount and/or the emission direction of the light emitted from the upper surface of the wavelength conversion member114b. The third light-modulating member114iis located at the lower surface of the light-emitting element114aand the lower surface of the wavelength conversion member114bso that the lower surfaces of the electrodes114dand114eare exposed. The third light-modulating member114ican reflect the light oriented toward a lower surface of the wavelength conversion member114bto the upper surface and side surfaces of the wavelength conversion member114b. The second light-modulating member114hand the third light-modulating member114ieach can include a light-transmitting resin, a light-diffusing agent included in the light-transmitting resin, etc. The light-transmitting resin is, for example, a silicone resin, an epoxy resin, or an acrylic resin. For example, particles of TiO2, SiO2, Nb2O5, BaTiO3, Ta2O5, Zr2O3, Y2O3, Al2O3, ZnO, MgO, BaSO4, glass, etc., are examples of the light-diffusing agent. The second light-modulating member114hmay also include a metal member such as, for example, Al, Ag, etc., so that the luminance directly above the light source114does not become too high.

The light-transmitting member115is located in the light source placement portion113a. The light-transmitting member115covers the light source114. The first light-modulating member116is located on the light-transmitting member115. The first light-modulating member116can reflect a portion of the light incident from the light-transmitting member115and can transmit another portion of the light so that the luminance directly above the light source114does not become too high. The first light-modulating member116can include a member similar to the second light-modulating member114hor the third light-modulating member114i.

A partitioning trench113bis provided in the light guide member113to surround the light source placement portions113ain top-view. High noticeability of the halo phenomenon can be suppressed by the partitioning trench113breflecting a portion of the light from the light source114. The partitioning trench113bextends in a lattice shape in the X-direction and the Y-direction. The partitioning trench113bextends through the light guide member113in the Z-direction. Alternatively, the partitioning trench112bmay be a recess provided in the upper surface or the lower surface of the light guide member113. Also, the partitioning trench112bmay not be provided in the light guide member113.

The light-reflecting member117is located in the partitioning trench113b. The high noticeability of the halo phenomenon can be further suppressed by the light-reflecting member117reflecting a portion of the light from the light source. For example, a light-transmitting resin that includes a light-diffusing agent can be used as the light-reflecting member117. For example, particles of TiO2, SiO2, Nb2O5, BaTiO3, Ta2O5, Zr2O3, ZnO, Y2O3, Al2O3, MgO, BaSO4, glass, etc., are examples of the light-diffusing agent. For example, a silicone resin, an epoxy resin, an acrylic resin, etc., are examples of the light-transmitting resin. For example, a metal member such as Al, Ag, etc., may be used as the light-reflecting member117. The light-reflecting member117covers a portion of side surfaces of the partitioning trench113bin a layer shape. Alternatively, the light-reflecting member117may fill the entire interior of the partitioning trench112b. Also, no light-reflecting member may be located in the partitioning trench112b.

According to the present embodiment, present of the multiple light sources114is individually controllable by the driver120for the backlight. Here, “controllable light emission” means that switching between lit and unlit is possible, and the luminance in the lit state is adjustable. For example, the planar light source may have a structure in which the light emission is controllable for each light source, or may have a structure in which multiple light source groups are arranged in a matrix configuration, and the light emission is controllable for each light source group.

In the specification, the subdivided regions of the planar light source each of which includes a light source or a light source group that are individually controllable are called “light-emitting regions”. In other words, the light-emitting region means the minimum region of the backlight of which the luminance is controllable by local dimming. Accordingly, according to the present embodiment, similarly to the partitioning trench113b, the regions of the planar light source111partitioned into a lattice shape correspond to light-emitting regions110s.

Each light-emitting region110sis rectangular. According to the present embodiment, one light source114is located in one light-emitting region110s. Then, the luminances of the multiple light-emitting regions110sare individually controlled by the driver120for the backlight individually controlling the light emission of the multiple light sources114. As described above, when the light emission is controlled for each of multiple light source groups, one light source group, i.e., multiple light sources, is located in one light-emitting region; and the multiple light sources are simultaneously lit or unlit.

The multiple light-emitting regions110sare arranged in a matrix configuration in top-view. Hereinbelow, in the structure of a matrix configuration such as that of the multiple light-emitting regions110s, the element group of the matrix of the light-emitting region110s, etc., arranged in the X-direction is called a “row”; and the element group of the matrix of the light-emitting region110s, etc., arranged in the Y-direction is called a “column”. For example, as shown inFIG.2, the row that is positioned furthest in the +Y direction (the row positioned uppermost when viewed according to a direction of reference numerals) is referred to as the “first row”; and the row that is positioned furthest in the −Y direction (the row positioned lowermost when viewed according to the direction of reference numerals) is referred to as the “final row”. Similarly, as shown inFIG.2, the column that is positioned furthest in the −X direction (the column positioned leftmost when viewed according to the direction of reference numerals) is referred to as the “first column”; and the column that is positioned furthest in the +X direction (the column positioned rightmost when viewed according to the direction of reference numerals) is referred to as the “final column”. The multiple light-emitting regions110sare arranged in N1 rows and M1 columns. Here, N1 and M1 each are any integer; an example is shown inFIG.2in which N1 is 8 and M1 is 16.

Although the partitioning trench113band the light-reflecting member117are included in the planar light source111as shown inFIG.3, the adjacent light-emitting regions110sare not perfectly shielded. Therefore, light can propagate between the adjacent light-emitting regions110s. Accordingly, the light that is emitted by the light source114in one light-emitting region110swhen the light source is lit may propagate to the adjacent light-emitting regions110sat the periphery of the one light-emitting region110s.

As shown inFIG.1, the driver120for the backlight is connected to the substrate112and the controller150. The driver120for the backlight includes a drive circuit that drives the multiple light sources114. The driver120for the backlight adjusts the luminances of the light-emitting regions110saccording to backlight control data SG1received from the controller150.

FIG.4illustrates a top view of the liquid crystal panel130of the image display device100according to the first embodiment.

The liquid crystal panel130is located on the backlight110. According to the present embodiment, the liquid crystal panel130is substantially rectangular in top-view. The liquid crystal panel130includes multiple pixels130parranged in a matrix configuration. InFIG.4, one region that is surrounded with a double dot-dash line corresponds to one pixel130p.

The liquid crystal panel130according to the present embodiment can display a color image. To achieve this objective, one pixel130pincludes three subpixels130spsuch that, for example, the white light emitted from the backlight110is transmitted to a subpixel that is configured to transmit blue light, a subpixel that is configured to transmit green light, and a subpixel that is configured to transmit red light. The light transmittances of the subpixels130spare individually controllable by the driver140for the liquid crystal panel. The gradations of the subpixels130spare individually controlled thereby.

The multiple pixels130pare arranged in N2 rows and M2 columns. Here, N2 and M2 each are any integer such that N2>N1 and M2>M1. The multiple pixels130pare located in the light-emitting regions110sin top-view. Although an example is shown inFIG.4demonstrates that four pixels130pcorrespond to one light-emitting region110s, the number of the pixels130pthat correspond to one light-emitting region110smay be less than four or more than four.

As shown inFIG.1, the driver140for the liquid crystal panel is connected to the liquid crystal panel130and the controller150. The driver140for the liquid crystal panel includes a drive circuit of the liquid crystal panel130. The driver140for the liquid crystal panel adjusts gradations of the pixels130paccording to liquid crystal panel control data SG2received from the controller150.

FIG.5is a block diagram showing components of the image display device according to the first embodiment.

According to the first embodiment, the controller150includes an input interface151, memory152, a processor153such as a CPU (central processing unit) or the like, and an output interface154. These components are connected to each other by a bus.

For example, the input interface151is connected to an external device900such as a tuner, a personal computer, a game machine, etc. The input interface151includes, for example, a connection terminal to the external device900such as a HDMI® (High-Definition Multimedia Interface) terminal, etc. The external device900inputs an input image IM to the controller150via the input interface151.

The memory152includes, for example, ROM (Read-Only Memory), RAM (Random-Access Memory), etc. The memory152stores various programs, various parameters, and various data for displaying an image in the liquid crystal panel.

By reading the programs stored in the memory152, the processor153processes the input image IM, determines setting values of luminances of the light-emitting regions110sof the backlight110and setting values of the gradations of the pixels130pof the liquid crystal panel130, and controls the backlight110and the liquid crystal panel130based on these setting values. Thereby, an image that corresponds to the input image IM is displayed on the liquid crystal panel130. The processor153includes a luminance data generator153a, a luminance setting data generator153b, a gradation setting data generator153c, and a control unit153d.

The output interface154is connected to the driver120for the backlight. Also, the output interface154includes, for example, a connection terminal of the driver140for the liquid crystal panel such as a HDMI® terminal, etc., and is connected to the driver140for the liquid crystal panel. The driver120for the backlight receives the backlight control data SG1via the output interface154. The driver140for the liquid crystal receives the liquid crystal panel control data SG2via the output interface154.

An image display method that uses the image display device100according to the present embodiment will be described hereinafter. Functions of the processor153as the luminance data generator153a, the luminance setting data generator153b, the gradation setting data generator153c, and the control unit153dalso will be described.

FIG.6is a flowchart showing an image display method according to the first embodiment.

The image display method according to the first embodiment includes an acquisition process S1of the input image IM, a generation process S2of luminance data D1, a generation process S3of luminance setting data D2, a generation process S4of gradation setting data D3, and a display process S5of the image on the liquid crystal panel130. The processes will now be elaborated. A method of displaying an image corresponding to one input image IM on the liquid crystal panel130will be described. When the input images IM are sequentially input to the controller150and images that correspond to the input images IM are sequentially displayed on the liquid crystal panel130, the following process S1to S5are repeatedly performed.

First, the acquisition process S1of the input image IM will be described.

As shown inFIG.5, the input interface151of the controller150receives the input image IM from the external device900. The received input image IM is stored in the memory152.

FIG.7is a schematic diagram showing an input image input to the controller150of the image display device100according to the first embodiment.

FIG.8is a schematic diagram showing a relationship among the pixels of the liquid crystal panel130, the light-emitting regions of the backlight110, and the pixels of the input image in the first embodiment.

The input image IM is data in which gradations are set for multiple pixels (may be referred to as “image pixels”) IMp arranged in a matrix configuration. According to the first embodiment, the input image IM is a color image. To achieve this objective, a blue gradation Gb, a green gradation Gg, and a red gradation Gr are set for one pixel IMp. For example, the gradations Gb, Gg, and Gr are represented by numerals from 0 to 255.

For easier understanding of the following description, for example, the arrangement directions of the elements are represented using a xy orthogonal coordinate system for data in which elements such as the pixels IMp or the like are arranged in a matrix configuration as in the input image IM. The x-axis direction in the direction of the arrow is referred to as the “+x direction”; and the opposite direction is referred to as the “−x direction”. Similarly, the y-axis direction in the direction of the arrow is referred to as the “+y direction”; and the opposite direction is referred to as the “−y direction”. Also, hereinbelow, the element groups of the matrix that are arranged in the x-direction are called a “row”; and the element groups of the matrix that are arranged in the y-direction are called a “column”. For example, as shown inFIG.7, the row that is positioned furthest in the +y direction (the row positioned uppermost when viewed according to a direction of reference numerals) is referred to as the “first row”; and the row that is positioned furthest in the −y direction (the row positioned lowermost when viewed according to the direction of reference numerals) is referred to as the “final row”. Similarly, as shown inFIG.7, the column that is positioned furthest in the −x direction (the column positioned leftmost when viewed according to the direction of reference numerals) is referred to as the “first column”; and the column that is positioned furthest in the +x direction (the column positioned rightmost when viewed according to the direction of reference numerals) is referred to as the “final column”.

For easier understanding of the following description, an example is described in which one pixel IMp of the input image IM corresponds to one pixel130pof the liquid crystal panel130as shown inFIG.8. In other words, according to the present embodiment, the multiple pixels IMp are arranged in N2 rows and M2 columns. Then, multiple pixels IMp are included in an area IMs of the input image IM that corresponds to one light-emitting region110sof the backlight110. However, the correspondence between the pixels of the input image and the pixels of the liquid crystal panel may not be one-to-one. In such a case, the processor153of the controller150performs the following processing after performing preprocessing of the input image so that the pixels of the input image and the pixels of the liquid crystal panel correspond one-to-one.

The generation process S2of the luminance data D1will now be described.

FIG.9is a schematic diagram showing a process of generating luminance data in the image display method according to the first embodiment.

The luminance data generator153agenerates the luminance data D1including a luminance L converted from a maximum gradation Gmax of the gradations Gb, Gg, and Gr of the multiple pixels IMp with respect to each area IMs of the input image IM corresponding to one light-emitting region110s.

Specifically, first, the luminance data generator153adetermines an area IMs that corresponds to the light-emitting region110spositioned at the ith row and the jth column. Then, the luminance data generator153auses the maximum value of the red gradation Gr, the green gradation Gg, or the blue gradation Gb of all pixels IMp included in the area IMs as the maximum gradation Gmax of the area IMs. Then, the luminance data generator153aconverts the maximum gradation Gmax into the luminance L. Then, the luminance data generator153auses the luminance L as a value of an element e1(i, j) at the ith row and the jth column of the luminance data D1. Here, i is any integer from 1 to N1, and j is any integer from 1 to M1.

The luminance data generator153aperforms this processing for all of the areas IMs.

The luminance data D1thus obtained is data of a matrix configuration that includes N1 rows and M1 columns. The value of the element e1(i, j) of the luminance data D1at the ith row and the jth column is the luminance L converted from the maximum gradation Gmax of the area IMs at the ith row and the jth column.

The luminance data generator153astores the luminance data D1in the memory152.

FIG.10is a graph showing a luminance distribution when a light source in one light-emitting region is lit in the backlight of the image display device according to the first embodiment. InFIG.10, the horizontal axis is the position in the X-direction, and the vertical axis is the luminance.

InFIG.10, the light-emitting region110sin which the light source114is lit is shown as ON, and the light-emitting regions110sin which the light sources114are unlit are shown as OFF.

In the planar light source111according to the present embodiment, the adjacent light-emitting regions110sare not perfectly shielded. Therefore, when the light source114in one light-emitting region110sof the backlight110is lit, the light emitted from the light source114may propagate to neighboring light-emitting regions110sat the periphery of the one light-emitting region110s. For that reason, when the light source114in the one light-emitting region110sis lit and the light sources114in the neighboring light-emitting regions110sat the periphery of the one light-emitting region110sare unlit, the luminances of the neighboring light-emitting regions110sat the periphery are not perfectly zero. The leak of the light of the light source114in the brighter light-emitting regions110sto the darker neighboring light-emitting regions110sis highly noticeable as the luminance difference between the adjacent light-emitting regions110sincreases.

In a conventional image display device, the controller converts the luminance data D1into backlight control data as-is, and controls the driver for the backlight based on the converted backlight control data. Because the luminance data D1is determined solely according to the input image IM as is, the luminance difference between the adjacent light-emitting regions110smay be large enough to cause high noticeability of a halo phenomenon depending on the input image IM. In contrast, the image display method according to the first embodiment can suppress the high noticeability of the halo phenomenon by performing the generation process S3of the luminance setting data D2that is described below.

The generation process S3of the luminance setting data D2will now be described.

FIGS.11to14are schematic diagrams showing a process of generating the luminance setting data in the image display method according to the first embodiment.

As shown inFIG.14, the luminance setting data generator153bgenerates the luminance setting data D2including the setting values of the luminances of the light-emitting regions110sby applying a spatial filter F to the luminance data D1to reduce the luminance difference of the adjacent areas IMs.

The spatial filter F is prestored in the memory152. According to the present embodiment, the spatial filter F includes multiple weighting factors Fw arranged in a matrix configuration. In an example shown in the present embodiment, the spatial filter F is a matrix of three rows and three columns. However, the number of rows and the number of columns of the spatial filter F are not limited to the aforementioned numbers. Hereinbelow, the weighting factor Fw at the ith row and the jth column also is called the weighting factor Fw(i, j). Here, i and j each are any integer from 1 to 3.

The value of the weighting factor Fw(2, 2) at the center of the spatial filter F is preferably greater than the values of the other weighting factors Fw. A Gaussian filter is shown as an example of the spatial filter F inFIGS.12to14in which the value of the weighting factor Fw(2, 2) at the center is greater than the values of the other weighting factors Fw. According to the present embodiment, the sum total of the weighting factors Fw is 1. However, the values of the weighting factors of the spatial filter are not particularly limited as long as the luminance difference between the adjacent areas can be reduced.

A specific example of the process of generating the luminance setting data D2will now be described.

First, as shown inFIG.11, the luminance setting data generator153badds elements e1at the periphery of the luminance data D1so that the values of the added elements e1are equal to the values of the adjacent elements. Thereby, the luminance data D1is enlarged, and the number of rows of the luminance setting data D2finally obtained can match the number of rows of the light-emitting regions110swhen applying the spatial filter F as described below as shown inFIG.14. Similarly, the number of columns of the luminance setting data D2finally obtained also can match the number of columns of the light-emitting regions110s. Alternatively, the values of the elements added at the periphery of the luminance data may be 0 (zero). In other words, zero padding of the luminance data may be performed.

Hereinbelow, the data including the added elements e1at the periphery of the luminance data D1is called “enlarged luminance data D1z”. Even if the added elements at the outer perimeter of the enlarged luminance data D1zhave a value of 0, these elements also are called the “element e1”.

Then, as shown inFIG.12, the luminance setting data generator153bextracts a region Af that is furthest in the −x direction and furthest in the +y direction in the enlarged luminance data D1zand has the same size as the spatial filter F. Hereinbelow, the element e1at the ith row and the jth column in this region Af also is called the element e1(i, j).

Next, the luminance setting data generator153bcalculates the product of e1(i, j)×Fw(i, j) by multiplying the element e1(i, j) at the ith row and the jth column in this region Af by the weighting factor Fw(i, j) at the ith row and the jth column of the spatial filter F. The element e1(i, j) is either an added element of which the value is the same value as the adjacent element, or an element of which the value is the luminance L calculated in the process S2. The luminance setting data generator153bperforms the calculation of the product of e1(i, j)×Wf(i, j) for all elements e1(i, j) included in this region Af.

Then, the luminance setting data generator153bcalculates a sum Sf(1, 1) by summing all of the products of e1(i, j)×Fw(i, j) calculated for one region Af. In this manner, for two matrixes such as the region Af and the spatial filter F, the products of the elements at the same positions (coordinates) are calculated, and the sum of the calculated products is called the “multiply-add operation”.

Next, the luminance setting data generator153buses the sum Sf(1, 1) as the value of an element e2(1, 1) at the first row and the first column of the luminance setting data D2.

Then, as shown inFIG.13, the luminance setting data generator153bshifts the region Af one column in the +x direction in the enlarged luminance data D1z.

Next, the luminance setting data generator153bperforms the multiply-add operations of the element e1(i, j) and the weighting factor Fw(i, j) of the spatial filter F of this region Af. A sum Sf(1, 2) is calculated thereby.

Then, the luminance setting data generator153buses the sum Sf(1, 2) as the value of the element e2(1, 2) at the first row and the second column of the luminance setting data D2.

Next, the luminance setting data generator153bshifts the region Af one column at a time in the +x direction, and performs the multiply-add operation for each shift. In this manner, the luminance setting data generator153bsequentially shifts the region Af in the +x direction; and when the region Af is furthest in the +x direction, the luminance setting data generator153bshifts the region Af one row in the −y direction so that the region Af is furthest in the −x direction. Then, the luminance setting data generator153bperforms the multiply-add operation. Then, the luminance setting data generator153bagain shifts the region Af one column at a time in the +x direction and performs the multiply-add operation for each shift. Thus, the luminance setting data generator153bsequentially shifts the region Af in the x-direction and/or the y-direction and performs the multiply-add operation for each shift.

Finally, as shown inFIG.14, the region Af is furthest in the +x direction and furthest in the −y direction in the enlarged luminance data D1z. Then, the luminance setting data generator153bperforms the multiply-add operation of the element e1(i, j) included in this region Af and the weighting factor Fw(i, j) of the spatial filter F. The sum Sf(N1, M1) is calculated thereby. Then, the luminance setting data generator153buses the sum Sf(N1, M1) as the value of the element e2(N1, M1) at the final row and the final column of the luminance setting data D2.

The luminance setting data D2thus obtained is data of a matrix configuration of N1 rows and M1 columns. The value of each element e2(n, m) of the luminance setting data D2at the nth row and the mth column corresponds to the setting value of the luminance of the light-emitting region110spositioned at the nth row and the mth column. Here, n is any integer from 1 to N1, and m is any integer from 1 to M1.

The luminance setting data generator153bstores the luminance setting data D2in the memory152.

As described above, the luminance setting data generator153bperforms the multiply-add operation of the multiple weighting factors Fw(i, j) of the spatial filter F and the multiple luminances L included in the region Af of the luminance data D1to which the spatial filter F is applied while shifting the position of the region Af in the luminance data D1. As a result, the difference (the luminance difference) between the values of the adjacent elements e2of the luminance setting data D2can be less than the difference (the luminance difference) between the values of the adjacent elements e1of the luminance data D1that is calculated based on only the input image IM.

Although an example of the process of generating the luminance setting data D2is described above, the process of generating the luminance setting data is not limited to that described above. In the above example, although the region Af is shifted in the −y direction after shifting the region Af all the way in the +x direction in the enlarged luminance data D1z, the shift technique of the regions to which the spatial filter is applied to the enlarged luminance data is not limited to the shift technique described above.

The generation process S4of the gradation setting data D3will now be described.

FIG.15is a schematic diagram showing a process of generating gradation setting data in the image display method according to the first embodiment.

The gradation setting data generator153cgenerates the gradation setting data D3including setting values of the gradations of the pixels130pof the liquid crystal panel130based on the input image IM and the luminance setting data D2.

A specific example of the method for generating the gradation setting data D3will now be described.

According to the present embodiment, the memory152pre-stores luminance distribution data D4indicating luminance distribution in the XY plane when the light source114in one light-emitting region110sis lit. Although the setting values of the luminances of the light-emitting regions110sof the backlight110are determined in the process S3, actual luminance may be different depending on the position in the XY plane even in one light-emitting region110sas shown in the luminance distribution data D4ofFIG.15. Also, when the light source114in one light-emitting region110sis lit, the light propagates to its neighboring light-emitting regions110sat the periphery of the one light-emitting region110sas described above.

To address such an issue, first, the gradation setting data generator153cestimates a luminance value V(i, j) directly under the pixel130ppositioned at the ith row and the jth column of the liquid crystal panel130from the luminance setting data D2and the luminance distribution data D4. Here, i is any integer from 1 to N2, and j is any integer from 1 to M2.

Specifically, the gradation setting data generator153cestimates a luminance value V1(i, j) of the luminance setting data D2directly under the pixel130pwhen only the light source114in the light-emitting region110spositioned directly under the pixel130pis lit from the value of the element e2(the setting value of the luminance) corresponding to the light-emitting region110sand the luminance distribution data D4. Furthermore, the gradation setting data generator153cestimates a luminance value V2(i, j) of the luminance setting data D2directly under the pixel130pwhen only the light sources114in the neighboring light-emitting regions110sat the periphery are lit from the values of the elements e2corresponding to the neighboring light-emitting regions110sand the luminance distribution data D4. Then, the value of the sum of the luminance values V1(i, j) and V2(i, j) is estimated to be the luminance value V(i, j) directly under the pixel130p. Thereby, the gradation setting data generator153ccan estimate the luminance value V(i, j) directly under the pixel130pby including both the luminance distribution in the one light-emitting region110sand the light leakage from the neighboring light-emitting regions110s.

Then, the gradation setting data generator153cinputs the estimated luminance value V(i, j) and the blue gradation Gb of the pixel IMp of the input image IM corresponding to the pixel130p(i, j) into a conversion formula Ef. The conversion formula Ef is, for example, a conversion formula that converts the luminance into a gradation such as a gamma correction conversion formula, etc. The gradation setting data generator153cuses an output value Efb of the conversion formula Ef generated by inputting the blue gradation Gb into the conversion formula Ef as the setting value of the blue gradation of the pixel130p. Similar processing is performed also for the green gradation Gg; and an output value Efg of the conversion formula Ef obtained thereby is used as the setting value of the green gradation of the pixel130p. The gradation setting data generator153cperforms similar processing also for the red gradation Gr; and an output value Efr of the conversion formula Ef obtained thereby is used as the setting value of the red gradation of the pixel130p. The gradation setting data generator153cuses the output values Efb, Efg, and Efr of the conversion formula Ef as the value of an element e3(i, j) at the ith row and the jth column of the gradation setting data D3.

The gradation setting data generator153cperforms this processing for each pixel130pof the liquid crystal panel130. The gradation setting data D3is generated thereby.

The gradation setting data D3thus obtained is data of a matrix configuration of N2 rows and M2 columns. The three values of Efb, Efg, and Egr of the element e3(i, j) at the ith row and the jth column of the gradation setting data D3correspond respectively to the setting value of the blue gradation, the setting value of the green gradation, and the setting value of the red gradation of the pixel130ppositioned at the ith row and the jth column of the liquid crystal panel130.

The gradation setting data generator153cstores the gradation setting data D3in the memory152.

Although an example of the process of generating the gradation setting data D3is described above, the process of generating the gradation setting data is not limited to that described above. For example, the luminance values may be input into the conversion formula after estimating the luminance values directly under all of the pixels of the liquid crystal panel.

The display process S5of the image will now be described.

The control unit153dcauses the liquid crystal panel130to display the image by controlling the backlight110based on the luminance setting data D2and by controlling the liquid crystal panel130based on the gradation setting data D3.

Specifically, as shown inFIG.5, the control unit153dtransmits the backlight control data SG1generated based on the luminance setting data D2to the driver120for the backlight via the output interface154. The backlight control data SG1is, for example, data of a PWM (Pulse Width Modulation) format but is not particularly limited as long as the driver120for the backlight can operate based on the data. The driver120for the backlight controls the light emission of the light sources114based on the backlight control data SG1.

Also, the control unit153dtransmits the gradation setting data D3, which is the liquid crystal panel control data SG2to the driver140for the liquid crystal panel via the output interface154. Alternatively, the liquid crystal panel control data SG2may be data converted from the gradation setting data D3into a format that enables the driving of the driver140for the liquid crystal panel. The driver140for the liquid crystal panel controls the pixels130p, and more specifically, light transmittances for the light of the subpixels130spbased on the liquid crystal panel control data SG2.

The timing of converting the luminance setting data D2into the backlight control data SG1is not particularly limited as long as the timing is in or after the process S3. When converting the gradation setting data D3into the liquid crystal panel control data SG2, the timing of the conversion is not particularly limited as long as the timing is in or after the process S4.

Effects of the first embodiment will now be described.

The image display method according to the first embodiment includes the process S2of generating the luminance data D1, the process S3of generating the luminance setting data D2, the process S4of generating the gradation setting data D3, and the process S5of displaying the image in the liquid crystal panel130.

The backlight110includes the multiple light-emitting regions110sarranged in a matrix configuration. The liquid crystal panel130includes the multiple pixels130p. The input image IM is input to the controller150of the image display device100. In the process S2, the luminance data D1including the luminance L converted from the maximum gradation Gmax of an area IMs of the input image IM for each of the areas IMs corresponding to the light-emitting regions110sof the backlight110is generated.

In the process S3, the luminance setting data D2including the setting values of the luminances of the light-emitting regions110sof the backlight110is generated by applying the spatial filter F to the luminance data D1to reduce the luminance difference of the adjacent areas IMs.

In the process S4, the gradation setting data D3including the setting values of the gradations of the pixels130pof the liquid crystal panel130is generated based on the luminance setting data D2and the input image IM.

In the process S5, the image is displayed on the liquid crystal panel130by controlling the backlight110based on the luminance setting data D2and by controlling the liquid crystal panel130based on the gradation setting data D3.

In such a manner, in the image display method according to the first embodiment, the luminance setting data D2is generated by applying the spatial filter F to the luminance data D1to reduce the luminance difference of the adjacent areas IMs. As a result, according to the first embodiment, compared to the case where the backlight110is controlled based on the luminance data D1as is, the difference between the setting values of the luminances of the adjacent light-emitting regions110sof the backlight can be reduced. As a result, the halo phenomenon can be suppressed.

According to the first embodiment, the spatial filter F includes the multiple weighting factors Fw. In the process S3of generating the luminance setting data D2, the multiply-add operation of the multiple luminances L included in the region Af of the luminance data D1to which the spatial filter F is applied and the multiple weighting factors Fw of the spatial filter F is performed while shifting the position of the region Af in the luminance data D1. As a result, the luminance difference between the adjacent light-emitting regions110sof the backlight110can be reduced by including the maximum gradation Gmax of areas IMs of the input image IM and the maximum gradation Gmax of its neighboring areas IMs. The luminance difference between the adjacent light-emitting regions110sof the backlight110can be reduced by a simple method that uses the spatial filter F.

Among the multiple weighting factors Fw, the value of the weighting factor Fw(2, 2) at the center of the spatial filter F is greater than the values of the other weighting factors Fw. A large difference between the value of the element e2of the luminance setting data D2and the luminance L converted from the maximum gradation Gmax of areas IMs of the input image IM can be suppressed thereby.

The image display device100according to the first embodiment includes: the backlight110including the planar light source111that includes the multiple light-emitting regions110sarranged in a matrix configuration and includes the light sources114located in the multiple light-emitting regions110s; the liquid crystal panel130that is positioned on the backlight110and includes the multiple pixels130p; and the controller150controlling the backlight110and the liquid crystal panel130. The controller150includes the luminance data generator153a, the luminance setting data generator153b, the gradation setting data generator153c, and the control unit153d.

The luminance data generator153agenerates the luminance data D1in which the maximum gradation Gmax of an area IMs of the input image IM is converted into the luminance L for each area IMs corresponding to the light-emitting regions110sof the backlight110.

The luminance setting data generator153bgenerates the luminance setting data D2including the setting values of the luminances of the light-emitting regions110sof the backlight110by applying the spatial filter F to the luminance data D1to reduce the luminance difference of the adjacent areas IMs.

The gradation setting data generator153cgenerates the gradation setting data D3including the setting values of the gradations of the pixels130pof the liquid crystal panel130based on the luminance setting data D2and the input image IM.

The control unit153dcauses the liquid crystal panel130to display the image by controlling the backlight110based on the luminance setting data D2and by controlling the liquid crystal panel130based on the gradation setting data D3.

In such a manner, in the image display device100according to the first embodiment, the luminance setting data D2is generated by applying the spatial filter F to the luminance data D1to reduce the luminance difference of the adjacent areas IMs. As a result, the luminance difference of the adjacent areas IMs can be reduced compared to the case where the backlight110is controlled based on the luminance data D1as is. As a result, the halo phenomenon can be suppressed.

FIGS.16A and16Bare schematic diagrams showing other examples of the spatial filter.

As shown inFIG.16A, a spatial filter F2may be an averaging filter in which the values of all of weighting factors Fw2are the same. Also, as shown inFIG.16B, a spatial filter F3may be a median filter in which a weighting factor Fw3(2, 2) at the center is greater than the other weighting factors Fw3, and the values of the other weighting factors Fw3are the same. Also, the spatial filter may not be a known filter such as a Gaussian filter, an averaging filter, a median filter, etc.

Second Embodiment

A second embodiment will now be described.

FIG.17is a block diagram showing components of an image display device according to the second embodiment.

FIG.18is a flowchart showing an image display method according to the second embodiment.

The second embodiment differs from the first embodiment in that a controller250of the image display device200further includes a post-filtering data generator253e, and in that a generation process S22of luminance data D21, a generation process S23aof post-filtering data D22a, and a generation process S23bof luminance setting data D22bin the image display method are different.

As a general rule in the following description, only the differences from the first embodiment are described. Other than the items described below, the second embodiment is similar to the first embodiment.

FIG.19Ais a schematic diagram showing the kth input image.

FIG.19Bis a schematic diagram showing the (k+1)th input image.

According to the second embodiment, the kth input image IM is an image in which the pixel IMp at the third row and the third column, the pixel IMp at the third row and the fourth column, the pixel IMp at the fourth row and the third column, and the pixel IMp at the fourth row and the fourth column are bright, and the other pixels IMp are dark. The (k+1)th input image IM is an image in which the pixel IMp at the third row and the fifth column, the pixel IMp at the third row and the sixth column, the pixel IMp at the fourth row and the fifth column, and the pixel IMp at the fourth row and the sixth column are bright, and the other pixels IMp are dark. In other words, a rectangular bright region800moves two columns in the +x direction when the kth input image IM is switched to the (k+1)th input image IM.

First, a processing method of the kth input image IM will now be described.

FIG.20is a schematic diagram showing a process of generating the kth luminance data in the image display method according to the second embodiment.

In the generation process S22of the luminance data D21, first, the luminance data generator153adivides each area IMs of the kth input image IM into multiple filter application areas (may be referred to as “sub-divided areas”) Fa, in which multiple areas Ims correspond to one light-emitting region110s. Multiple pixels Imp are included in each filter application area Fa. InFIG.20, one region surrounded with a thick solid line is one area Ims; one region surrounded with a broken line is one filter application area Fa; and one region surrounded with a fine solid line is one pixel Imp.

InFIG.20, each area Ims is divided into nine filter application areas Fa in three rows and three columns. Each filter application area Fa includes four pixels Imp. However, the number of filter application areas included in each area and the number of pixels included in each filter application area are not limited to those described above.

The luminance data generator153agenerates the luminance data D21including a luminance L2converted from a maximum gradation Gmax2of the gradations Gb, Gg, and Gr of all pixels Imp included in each filter application area Fa of the kth input image IM.

When the multiple filter application areas Fa are arranged in N3 rows and M3 columns in the input image IM, the kth luminance data D21has a matrix configuration of N3 rows and M3 columns. Here, N3 is any integer that is greater than N1, i.e., the number of rows of the light-emitting regions110sor the areas Ims, and less than N2, i.e., the number of rows of the pixels Imp of the input image IM; and M3 is any integer that is greater than M1, i.e., the number of columns of the light-emitting regions110sor the areas Ims, and less than M2, i.e., the number of columns of the pixels Imp of the input image IM.

Hereinbelow, an element e21at the ith row and the jth column of the luminance data D21also is called the element e21(i, j). The elements e21correspond to the filter application areas Fa. Accordingly, i is any integer that is not less than 1 and not more than N3; and j is any integer that is not less than 1 and not more than M3.

As described above, the kth input image IM is an image including bright pixels Imp at the third row and the third column, the third row and the fourth column, the fourth row and the third column, and the fourth row and the fourth column, and the other dark pixels Imp. In the following description, the value of the element e21(2, 2) at the second row and the second column is assumed to be a value that is greater than 0 (e.g., described below as100in the embodiment); and the values of the other elements e21(i, j) are assumed to be 0.

The luminance data generator153astores the luminance data D21in the memory152.

The generation process S23aof the kth post-filtering data D22awill now be described.

FIGS.21to23are schematic diagrams showing a process of generating the kth post-filtering data in the image display method according to the second embodiment.

As shown inFIG.23, the post-filtering data generator253egenerates the post-filtering data D22aby applying a spatial filter F4to the kth luminance data D21to reduce the luminance difference of the adjacent elements e21, i.e., the adjacent filter application areas Fa.

The spatial filter F4is prestored in the memory152. According to the second embodiment, the spatial filter F4includes multiple weighting factors Fw4arranged in a matrix configuration. In the example shown in the second embodiment, the spatial filter F4is a matrix of three rows and three columns. However, the number of rows and the number of columns of the spatial filter F4are not limited to the aforementioned numbers. Hereinbelow, the weighting factor Fw4at the ith row and the jth column also is called the weighting factor Fw4(i, j). Here, i and j each are any integer from 1 to 3.

According to the second embodiment, the value of the weighting factor Fw4(2, 2) at the center of the spatial filter F4is greater than the values of the other weighting factors Fw4. However, the values of the weighting factors of the spatial filter are not particularly limited as long as the luminance difference between adjacent filter application areas can be reduced.

A specific example of the process of generating the post-filtering data D22awill now be described.

First, as shown inFIG.21, the post-filtering data generator253eadds the elements e21at the periphery of the kth luminance data D21so that the values thereof are equal to the values of the adjacent elements. The luminance data D21is enlarged thereby. Alternatively, the values of the elements added at the periphery of the luminance data may be 0 (zero). In other words, zero padding of the luminance data may be performed. Hereinbelow, the data including the added elements e21at the periphery of the luminance data D21is called enlarged luminance data D21z.

Then, as shown inFIG.22, the post-filtering data generator253eextracts a region Af2that has the same size as the spatial filter F4and is furthest at the −x side and furthest at the +y side in the enlarged luminance data D21z.

Next, the post-filtering data generator253ecalculates the product of e21(i, j)×Fw4(i, j) by multiplying the element e21(i, j) at the ith column and the jth column in this region Af2by the weighting factor Fw4(i, j) at the ith column and the jth column of the spatial filter F4. The post-filtering data generator253eperforms the calculation of the product of e21(i, j)×Fw4(i, j) for all elements e21(i, j) included in this region Af2.

Then, the post-filtering data generator253ecalculates a sum Sf4by summing all of the products of e21(i, j)×Fw4(i, j) calculated for one region Af2.

Next, the post-filtering data generator253euses the sum Sf4as the value of an element e22a(1, 1) at the first row and the first column of the kth post-filtering data D22a. In other words, the post-filtering data generator253eperforms a multiply-add operation of the element e21(i, j) of the region Af2and the weighting factor Fw4(i, j) of the spatial filter F4.

Then, the post-filtering data generator253eshifts the region Af2in the enlarged luminance data D21zone column at a time in the +x direction, and performs the multiply-add operation of the element e21(i, j) of the region Af2and the weighting factor Fw4(i, j) of the spatial filter F4for each shift. After the multiply-add operation is performed for the region Af2positioned furthest at the +x side, the post-filtering data generator253eshifts the region Af2to be located furthest at the −x side and shifted one row in the −y direction, and performs the multiply-add operation. Then, the post-filtering data generator253eshifts the region Af2in the enlarged luminance data D21zone column at a time in the +x direction and performs the multiply-add operation of the element e21(i, j) of the region Af2and the weighting factor Fw4(i, j) of the spatial filter F4for each shift.

By repeating the processing described above, finally, as shown inFIG.23, the region Af2is furthest at the +x side and furthest at the −y side in the enlarged luminance data D21z. Then, the post-filtering data generator253eperforms the multiply-add operation of the element e21(i, j) included in this region Af2and the weighting factor Fw4(i, j) of the spatial filter F. The sum Sf4is calculated thereby. Then, the post-filtering data generator253euses the sum Sf4as the value of the element e22a(N3, M3) at the final row and the final column of the post-filtering data D22a.

The post-filtering data D22athus obtained is data of a matrix configuration of N3 rows and M3 columns. Similarly to the elements e21of the luminance data D21, the elements e22aof the post-filtering data D22acorrespond to the filter application areas Fa.

In the kth post-filtering data D22a, the values of the element e22a(2, 2) at the second row and the second column and the elements e22aadjacent to the element e22a(2, 2) are greater than 0; and the values of the other elements e22aare 0.

The post-filtering data generator253estores the post-filtering data D22ain the memory152.

The generation process S23bof the kth luminance setting data D22bwill now be described.

FIG.24is a schematic diagram showing a process of generating the kth luminance setting data in the image display method according to the second embodiment.

The luminance setting data generator153bgenerates the kth luminance setting data D22bbased on the kth post-filtering data D22a.

Specifically, the luminance setting data generator153bdetermines a maximum value Emax of the values of the multiple filter application areas Fa, i.e., the multiple elements e22a, included in the area IMs at the nth row and the mth column of the kth post-filtering data D22a. Here, n is any integer from 1 to N1; and m is any integer from 1 to M1.

The luminance setting data generator153buses the maximum value Emax as the value of an element e22b(n, m) at the nth row and the mth column of the kth luminance setting data D22b. The luminance setting data generator153bperforms this processing for all of the areas IMs.

The luminance setting data D22bthus obtained is data of a matrix configuration of N1 rows and M1 columns. The value of the element e22b(n, m) at the nth row and the mth column corresponds to the setting value of the luminance of the light-emitting region110spositioned at the nth row and the mth column.

In the kth post-filtering data D22a, the element e22a(2, 2) at the second row and the second column and its neighboring elements e22athat are adjacent to the element e22a(2, 2) are included in the area IMs at the first row and the first column. As a result, in the luminance setting data D22b, the value of the element e22b(1, 1) at the first row and the first column, i.e., the setting value of the luminance of the light-emitting region110spositioned at the first row and the first column, is greater than 0. The setting values of the luminances of the other light-emitting regions110sare 0.

The luminance setting data generator153bstores the luminance setting data D22bin the memory152.

A processing method of the (k+1)th input image IM will now be described.

FIG.25is a schematic diagram showing a process of generating the (k+1)th luminance data in the image display method according to the second embodiment.

FIG.26is a schematic diagram showing a process of generating the (k+1)th post-filtering data in the image display method according to the second embodiment.

FIG.27is a schematic diagram showing a process of generating the (k+1)th luminance setting data in the image display method according to the second embodiment.

As shown inFIG.25, the luminance data generator153aperforms a process similar to the process of generating the kth luminance data D21, to generate the (k+1)th luminance data D21based on the (k+1)th input image IM. As described above, the (k+1)th input image IM is an image including bright pixels IMp at the third row and the fifth column, the third row and the sixth column, the fourth row and the fifth column, and the fourth row and the sixth column, and the other darker pixels IMp. In the (k+1)th luminance data D21hereinbelow, the value of the element e21(2, 3) at the second row and the third column is assumed to be greater than 0; and the values of the other filter application areas Fa are assumed to be 0.

As shown inFIG.26, the post-filtering data generator253eperforms a process similar to the process of generating the (k+1)th post-filtering data D22a, to generate the post-filtering data D22aby applying the spatial filter F4to the (k+1)th luminance data D21. Thereby, in the (k+1)th post-filtering data D22a, the values of the element e22a(2, 3) at the second row and the third column and the neighboring elements e22aadjacent to the element e22a(2, 3) are greater than 0; and the values of the other elements e22aare 0.

As shown inFIG.27, the luminance setting data generator153bperforms a process similar to the process of generating the kth luminance setting data D22b, to generate the (k+1)th luminance setting data D22bbased on the post-filtering data D22a. In the (k+1)th post-filtering data D22a, the element e22a(2, 3) and a portion of the neighboring elements e22aadjacent to the element e22a(2, 3) are included in the area IMs at the first row and the first column; and the other portion of the neighboring elements e22aadjacent to the element e22a(2, 3) is included in the area IMs at the first row and the second column. Therefore, the setting value of the luminance of the light-emitting region110spositioned at the first row and the first column and the setting value of the luminance of the light-emitting region110spositioned at the first row and the second column are greater than 0; and the setting values of the luminances of the other light-emitting regions110sare 0.

In such a manner, by applying the spatial filter F4to the luminance data D21including multiple filter application areas Fa in each area IMs, when the vicinity of the boundary between the adjacent areas IMs of the input image IM is bright as in the (k+1)th input image IM, both of the two light-emitting regions110sthat correspond to the adjacent areas IMs can be lit, and the luminances of the light-emitting regions110scan be adjusted. The effects obtained from this light-emission of the light-emitting regions110swill now be elaborated.

FIG.28is a schematic diagram showing luminance distributions of two areas of multiple consecutive input images, and two light-emitting regions that correspond to the two areas.

Hereinbelow, the two areas IMs that are arranged in the +x direction in each input image IM are called a first area IMs1and a second area IMs2in this order. The light-emitting region110sthat corresponds to the first area IMs1is called a first light-emitting region110s1; and the light-emitting region110sthat corresponds to the second area IMs2is called a second light-emitting region110s2.

Similarly to the kth input image IM ofFIG.19A, the first input image IM is an image including a brighter rectangular region800that includes the pixels IMp at the third row and the third column, the third row and the fourth column, the fourth row and the third column, and the fourth row and the fourth column, and the other daker pixels IMp. When the rectangular region800moves two columns in the +x direction between the input images from the first input image IM to the fourth input image IM in this order, the setting values of the luminances of the corresponding two light-emitting regions110sare as follows.

In the first input image IM, similarly to the processing method of the kth input image IM described above, the setting value of the luminance of the first light-emitting region110s1is greater than 0, and the setting value of the luminance of the second light-emitting region110s2is 0. Accordingly, the light source114of the first light-emitting region110s1is lit, and the light source114of the second light-emitting region110s2is unlit. At this time, according to the structure of the planar light source111, the luminance distribution in the first light-emitting region110s1may become nonuniform, and the luminance of the outer perimeter portion of the first light-emitting region110s1may become less than the luminance of the central portion. However, in the first input image IM, the rectangular region800is positioned directly above the central portion of the first light-emitting region110s1. For that reason, the rectangular region800that is displayed on the liquid crystal panel130is less likely to be affected by the luminance distribution in the first light-emitting region110s1.

In the second input image IM, similarly to the processing method of the (k+1)th input image IM described above, both of the setting value of the luminance of the first light-emitting region110s1and the setting value of the luminance of the second light-emitting region110s2are greater than 0. Accordingly, the light sources114of the first and second light-emitting regions110s1and110s2are lit. In the second input image IM, the rectangular region800is positioned directly above the +x direction end portion of the first light-emitting region110s1. Therefore, the output of the light source114of the second light-emitting region110s2is less than the output of the light source114of the first light-emitting region110s1. Although the luminance of the outer perimeter portion of the first light-emitting region110s1may become less than the luminance of the central portion as described above, according to the second embodiment, the reduction of the luminance of the rectangular region800displayed on the liquid crystal panel130can be suppressed by also lighting the light source114of the second light-emitting region110s2.

In the third input image IM, similarly to the second input image IM, both of the setting value of the luminance of the first light-emitting region110s1and the setting value of the luminance of the second light-emitting region110s2are greater than 0. However, in the third input image IM, the rectangular region800is positioned directly above the +x direction end portion of the second light-emitting region110s2. Therefore, the output of the light source114of the first light-emitting region110s1is less than the output of the light source114of the second light-emitting region110s2. Although the luminance of the outer perimeter portion of the second light-emitting region110s2may become less than the luminance of the central portion, according to the second embodiment, the reduction of the luminance of the rectangular region800displayed on the liquid crystal panel130can be suppressed by also lighting the light source114of the first light-emitting region110s1.

In the fourth input image IM, the setting value of the luminance of the first light-emitting region110s1is 0, and the setting value of the luminance of the second light-emitting region110s2is greater than 0. In the fourth input image IM, the rectangular region800is positioned directly above the central portion of the second light-emitting region110s2. Therefore, the rectangular region800that is displayed on the liquid crystal panel130is not easily affected by the luminance distribution in the second light-emitting region110s2.

In such a manner, when a video image including a bright moving rectangular region800is displayed on the liquid crystal panel130by using the multiple consecutive input images IM, unintentional change of the luminance of the image due to the movement can be suppressed.

Effects of the second embodiment will now be described.

According to the second embodiment, the image display method includes the process S22of generating the luminance data D21, the process S23aof generating the post-filtering data, and the process S23bof generating the luminance setting data.

In the process S22of generating the luminance data D21, the maximum gradation of each of the multiple filter application areas Fa of the input image IM is converted into a luminance, and the multiple filter application areas Fa are generated by dividing each of the areas IMs that correspond to the light-emitting regions110sinto a plurality.

In the process S23aof generating the post-filtering data, the post-filtering data D22ais generated by applying the spatial filter F4to the luminance data D21to reduce the luminance difference of the adjacent filter application areas Fa.

In the process S23bof generating the luminance setting data, the setting values of the luminances of the light-emitting regions110sof the backlight110are determined based on the post-filtering data D22a.

According to the second embodiment as well, similarly to the first embodiment, the halo phenomenon can be suppressed. By applying the spatial filter F4to the luminance data D21in which each of the areas IMs corresponding to the light-emitting regions110sis subdivided into multiple filter application areas Fa, the image of the liquid crystal panel130displayed directly above the outer perimeter portion of one light-emitting region110scan be prevented from being dark. In particular, a change of the brightness of the image due to the movement can be suppressed when displaying a video image in which an image of an icon of a mouse or the like moves in the liquid crystal panel130.

For example, the invention can utilized in the display of a device such as a television, a personal computer, a game machine, etc.