JP4951973B2 - Display device and display method - Google Patents

Description

  The present invention relates to a technical field of a display device and a display method suitable for application to, for example, a liquid crystal display device.

  In a display device, for example, a liquid crystal display device, since the pixels of the liquid crystal panel do not emit light, a backlight is disposed on the back side of the liquid crystal panel, and the back surface of the liquid crystal panel is illuminated with the backlight to display an image. Yes.

  Conventionally, in a liquid crystal display device, the entire display screen of the liquid crystal panel is illuminated with uniform brightness by a backlight, the aperture ratio of each pixel of the liquid crystal panel is controlled, and the shielding amount of light emitted from the backlight is adjusted. Thus, necessary brightness is obtained in each part of the display screen. Therefore, for example, even when the entire display screen is dark, the backlight emits light with substantially the maximum luminance that can be set, and there is a problem that the backlight emits light unnecessarily brightly and consumes a large amount of power.

  In order to solve the problem of the liquid crystal display device having such a backlight, for example, a method of controlling the light emission luminance of the entire backlight based on display luminance information of the entire display screen has been proposed.

  Also, a method of dividing the display screen into a plurality of regions corresponding to each light source constituting the backlight, and partially suppressing the light emission luminance of the light source corresponding to the display luminance required for each divided region Has been proposed (see, for example, Patent Document 1).

  The above “emission luminance” refers to the luminance when light is emitted from the light source, and the “display luminance” refers to when the light emitted from the light source passes through the display unit (display screen). Of the brightness (hereinafter the same).

  FIG. 22 conceptually shows an example of such a control method. For example, as shown in FIG. 22 (a), it is assumed that the darkest oval shape is displayed in the approximate center of one image (original image), and an image that gradually becomes brighter is displayed around it. The backlight c of the liquid crystal display device on which such an image is displayed is composed of a plurality of light sources d, d,... Arranged vertically and horizontally as shown in FIG. Then, when the image shown in FIG. 22A is displayed, the light emission luminance of the light sources d and d corresponding to the place where the display luminance is the lowest is suppressed.

  Thus, by displaying the image while partially suppressing the light emission luminance of the backlight c, it is possible to prevent unnecessary lighting of the backlight and reduce power consumption.

JP 2004-221503 A

By the way, in the conventional light source control method described above, for example, when the center position (position Pa shown in FIG. 23) in the region is the portion with the highest display luminance, as shown in FIG. By setting the light emission luminance A to the value M, it is possible to ensure the necessary display luminance corresponding to the portion with the highest display luminance.
On the other hand, if the display brightness of the adjacent area is low, when the boundary position (position Pb shown in FIG. 23) in the area is the portion with the highest display brightness, as shown in FIG. Even if the light emission luminance B of the light source in the region to be added is added, the added light emission luminance C reaches only the value L, and the necessary display luminance corresponding to the portion with the highest display luminance cannot be ensured.
Therefore, in this case, as shown in FIG. 24, the light emission luminance A of the light source is set higher than the value M, the light emission luminance A ′ is set to the value H, and the light emission luminance C is obtained by adding the light emission luminance A ′ and the light emission luminance B. It is necessary for ′ to be greater than or equal to the value M within the entire range in the region.
However, in such a control, light is emitted from each light source with an emission luminance more than necessary to all the portions other than the position Pb, and the portion indicated by hatching in FIG. 24 becomes a useless light emission portion. In such a control method, there is a problem that useless light emission portions are generated in all the regions where the highest display luminance portion is shifted from the center of each region, resulting in poor light emission efficiency.

  Accordingly, it is an object of the display device and the display method of the present invention to overcome the above-described problems and improve the light emission efficiency.

The display device of the present invention has a display screen divided into a plurality of areas, and is controlled in pixel units to set an aperture ratio. In each divided area, an enlarged area that overlaps between adjacent divided areas is formed. A display unit that is provided and the area range of each divided region is set including an enlarged region, and a plurality of light sources that illuminate the back surface of the display unit and that are separately arranged corresponding to the plurality of divided regions of the display unit The display brightness in each divided region of the display unit is detected when an image is displayed on the display screen based on the backlight configured by the input image signal, and each arranged corresponding to each divided region The light emission luminance of the light source is calculated according to the position showing the maximum display luminance in each divided region including the influence of the other light sources arranged corresponding to the adjacent divided regions on the corresponding region, and corresponds to each divided region. Arranged Set the emission luminance of each light source to the calculated emission luminance, and calculate the correction amount for each pixel of the display unit based on the amount of deviation between the set emission luminance and the optimum value of the display luminance in each unit of the display screen, And a control unit that sends a display drive signal generated based on the calculated correction amount to each pixel and controls the aperture ratio of each pixel.

The display method of the present invention includes a display unit that has a display screen divided into a plurality of regions, is controlled in pixel units, and sets an aperture ratio. The display unit illuminates the back surface of the display unit, and the display unit includes a plurality of regions. Correspondingly, in a method for displaying an image in a display device including a backlight configured by a plurality of light sources arranged separately, each divided area of the display unit overlaps with an adjacent divided area. Display in each divided region of the display unit when an enlarged region is provided and the region range of each divided region is set including the enlarged region and an image is displayed on the display screen based on the input image signal by the control unit detecting the brightness, the maximum table the light emission luminance, in each of the divided regions including the effect on the region of the other light sources arranged corresponding to the adjacent divided regions of each light source disposed so as to correspond to the divided regions Calculate according to the position indicating the brightness, set the light emission brightness of each light source arranged corresponding to each divided area to the above calculated light emission brightness, and optimize the set light emission brightness and the display brightness in each part of the display screen A correction amount for each pixel of the display unit is calculated based on the amount of deviation from the value, and a display drive signal generated based on the calculated correction amount is sent to each pixel to control the aperture ratio of each pixel. It is a thing.

  Therefore, in the display device and the display method of the present invention, the light emission luminance of each light source is controlled based on the position showing the maximum display luminance in each divided region.

The display device of the present invention has a display screen divided into a plurality of areas, and is controlled in pixel units to set an aperture ratio. In each divided area, an enlarged area that overlaps between adjacent divided areas is formed. A display unit that is provided and the area range of each divided region is set including an enlarged region, and a plurality of light sources that illuminate the back surface of the display unit and that are separately arranged corresponding to the plurality of divided regions of the display unit The display brightness in each divided region of the display unit is detected when an image is displayed on the display screen based on the backlight configured by the input image signal, and each arranged corresponding to each divided region The light emission luminance of the light source is calculated according to the position showing the maximum display luminance in each divided region including the influence of the other light sources arranged corresponding to the adjacent divided regions on the corresponding region, and corresponds to each divided region. Arranged Set the emission luminance of each light source to the calculated emission luminance, and calculate the correction amount for each pixel of the display unit based on the amount of deviation between the set emission luminance and the optimum value of the display luminance in each unit of the display screen, And a control unit that sends a display drive signal generated based on the calculated correction amount to each pixel and controls an aperture ratio of each pixel.

  Therefore, it is possible to improve the light emission efficiency while ensuring the necessary light emission luminance regardless of the position of the maximum display luminance in each divided region.

The display method of the present invention includes a display unit that has a display screen divided into a plurality of regions, is controlled in pixel units, and sets an aperture ratio. The display unit illuminates the back surface of the display unit, and the display unit includes a plurality of regions. A method of displaying an image on a display device comprising a backlight composed of a plurality of light sources arranged separately corresponding to each other, wherein each divided area of the display unit overlies each other between adjacent divided areas. Set the area range of each divided area including the enlarged area by providing an enlarged area to wrap, and each divided area of the display unit when the control unit displays an image on the display screen based on the input image signal The display luminance at each of the divided regions including the influence of the other light sources arranged corresponding to the adjacent divided regions is maximized. Table Calculate according to the position indicating the brightness, set the light emission brightness of each light source arranged corresponding to each divided area to the above calculated light emission brightness, and optimize the set light emission brightness and the display brightness in each part of the display screen A correction amount for each pixel of the display unit is calculated based on the amount of deviation from the value, and a display drive signal generated based on the calculated correction amount is sent to each pixel to control the aperture ratio of each pixel. It is characterized by that.

  Therefore, it is possible to improve the light emission efficiency while ensuring the necessary light emission luminance regardless of the position of the maximum display luminance in each divided region.

  The best mode of the present invention will be described below with reference to FIGS.

  In the best mode shown below, the display device of the present invention is applied to a liquid crystal display device, and the display method of the present invention is applied to a display method of an image displayed on the liquid crystal display device.

  Note that the scope of application of the present invention is not limited to the liquid crystal display device and a method for displaying an image displayed on the liquid crystal display device, and a backlight is disposed on the back side of the display unit to control the pixel aperture ratio of the display unit. Thus, the present invention can be applied to all display devices that display images and display methods of images displayed on the display devices.

  As shown in FIG. 1, the display device (liquid crystal display device) 1 includes a display unit 2 for displaying an image, a backlight 3 disposed on the back side of the display unit 2, the backlight 3 and the display unit 2. And a control unit 4 that performs various controls.

  The display unit 2 includes a liquid crystal panel 5 and a source driver 6 and a gate driver 7 for sending drive signals to the liquid crystal panel 5. The liquid crystal panel 5 is configured such that the display screen is divided equally into a plurality of regions, for example, 24 regions a to x (see FIG. 2).

  As shown in FIG. 3, each divided area of the display unit 2 is provided with an area that overlaps each adjacent divided area, and the area range of each divided area is set to include the overlapping area. . For example, the area a includes an original area a1 (upwardly hatched portion) formed by equally dividing the display screen and an enlarged area a2 (upwardly hatched portion) overlapping the areas b, g, and h. The region h is configured by the original region h1 (upwardly hatched portion) and an enlarged region h2 (upwardly hatched portion) overlapping the regions a, b, c, g, i, m, n, and o. Has been. In FIG. 3, the area delimited by the dotted line indicates the original area, and the area excluding the original area among the areas delimited by the solid line indicates the enlarged area.

  The backlight 3 includes a plurality of light sources, for example, 24 light sources 8A, 8B,..., 8X, and the light sources 8A, 8B,. (See FIG. 2). Each of the light sources 8A, 8B,..., 8X has, for example, a configuration in which a plurality of light emitting elements such as light emitting diodes are arranged in the horizontal direction.

  As the plurality of light emitting diodes constituting the light sources 8A, 8B,..., 8X, for example, a red light emitting diode, a green light emitting diode, and a blue light emitting diode are used, and these light emitting diodes are sequentially arranged in a predetermined state. By arranging, it is made white by mixing each color. The light emitted from each of the light sources 8A, 8B,..., 8X is diffused by a scattering plate or a scattering sheet (not shown) and applied to the back surface of the liquid crystal panel 5.

  In addition, each area | region ax of a display screen is not set as an area | region where the light radiate | emitted only from light source 8A, 8B, ..., 8X located in back is arrived. Therefore, the light emitted from each of the light sources 8A, 8B,..., 8X reaches an area other than the area located immediately before by a scattering plate or the like described later.

  Further, in the above, for the sake of simplicity, as an example of the backlight 3, the light sources 8A, 8B,..., 8X are shown as being divided and arranged in the vertical direction and the horizontal direction. The backlight may be one in which the light source is divided and arranged only in the vertical direction or only in the horizontal direction.

  The control unit 4 includes a light source control circuit 9 that controls the backlight 3 and a liquid crystal panel control circuit 10 that controls the display unit 2 (see FIG. 1). A memory 11 is connected to the liquid crystal panel control circuit 10.

  The memory 11 stores data on the distribution state of the light emitted from the light sources 8A, 8B,. The memory 11 also stores data for correcting display unevenness of the liquid crystal panel 5.

  In the display device 1 configured as described above, when an image signal is input to the liquid crystal panel control circuit 14, a display drive signal for performing display drive in the liquid crystal panel 5 based on the input image signal is displayed on the liquid crystal panel. It is generated by the control circuit 14.

  The generated display drive signal is sent to the source driver 6 and the gate driver 7 of the liquid crystal panel 5 and input to each pixel of the liquid crystal panel 5 via the source driver 6 and the gate driver 7. The display drive signal is input in one field period in synchronization with the field period of the input image signal. When a display drive signal is input to each pixel of the liquid crystal panel 5, a correction process described later is performed.

  Control for each of the light sources 8A, 8B,..., 8X is executed by the light source control circuit 9 (see FIG. 1). When the image signal is input to the liquid crystal panel control circuit 14, the light source control circuit 9 receives individual lighting control signals for the light sources 8A, 8B,. The light emission luminances of the light sources 8A, 8B,..., 8X are individually set in one field cycle.

  FIG. 4 shows an example of the light emission luminance of each light source 8A, 8B,..., 8X. In FIG. 4, the horizontal axis indicates the position in the vertical or horizontal direction of the display screen, the vertical axis indicates the light emission luminance, and each light source 8A, 8B,..., 8X emits light at a substantially maximum uniform luminance. It is an example. FIG. 4 shows, as an example, the state of light emission luminance for only six light sources.

  In FIG. 4, the solid line data indicates the light emission luminance of each of the light sources 8A, 8B,..., 8X. This data does not consider the influence of light reflection at both ends in the vertical or horizontal direction of the display screen. In FIG. 4, the data indicated by the alternate long and short dash line indicates the total light emission luminance calculated by adding the light emission luminances of the light sources 8A, 8B,. The total light emission luminance is substantially uniform at any position in the vertical or horizontal direction except for both ends of the display screen in the vertical or horizontal direction.

  As described above, when each of the light sources 8A, 8B,..., 8X emits light with substantially uniform luminance, the total light emission luminance decreases at both ends in the vertical direction or horizontal direction of the display screen. However, at both ends in the vertical or horizontal direction of the display screen, the light emission luminance of the light sources 8A, 8B,..., 8X located at both ends is increased due to the influence of light reflection (see FIG. 5). Therefore, in the display device 1, a decrease in the total light emission luminance at both ends in the vertical direction of the display screen is alleviated.

  Further, in the display device 1, the maximum light emission luminance of the light sources 8 and 8 positioned at both ends in the vertical direction or the horizontal direction is set to other values in order to avoid a decrease in total light emission luminance at both ends in the vertical direction of the display screen as much as possible. It is also possible to set higher than the maximum light emission luminance of the light sources 8, 8,.

  Furthermore, in order to completely eliminate the decrease in the total light emission luminance at both ends in the vertical or horizontal direction of the display screen, for example, a portion surrounded by a dotted line shown in FIG. Is possible.

  The display device 1 is not provided with a partition or the like for preventing the light emitted from each of the light sources 8A, 8B,..., 8X from reaching an area other than the area located immediately before. Therefore, the light emitted from each of the light sources 8A, 8B,..., 8X reaches another region other than the region located immediately before, and contributes to the display luminance in the other region.

  6 shows the positions of the display screen when the emitted light is incident on the liquid crystal panel 5 when the light sources 8A, 8B,..., 8X having the light emission luminance shown in FIG. The luminance contribution rates of the light sources 8A, 8B,..., 8X are shown. The horizontal axis represents the position of the display screen, for example, in the horizontal direction, and the vertical axis represents the luminance contribution ratio to the display luminance of the light emitted from each of the light sources 8A, 8B,. FIG. 6 shows luminance contribution ratios for the regions a to f as an example.

  As shown in FIG. 6, the luminance contribution ratios of the light emitted from the light sources 8A, 8B,..., 8X are respectively in the regions a to x located immediately before the light sources 8A, 8B,. It is the highest and gradually decreases as the distance from the regions a to x increases. For the light sources 8A and 8F arranged at both ends, the luminance contribution ratios in the regions a and f located immediately before are about 40%, and for the light sources 8B, 8C, 8D and 8E arranged at intermediate positions, respectively. The luminance contribution ratios in the regions b to e positioned immediately before are about 30%. In addition, the light sources 8A, 8B,..., 8F also contribute to display luminance in each region other than the regions a to f positioned immediately before each of the light sources 8A, 8B,.

  Thus, in the display device 1, since the light emitted from each of the light sources 8A, 8B,..., 8X reaches a region other than the region located immediately before, the light sources 8A, 8B,. ... Each light emitted from 8X is not irradiated to each of the regions a to x located immediately before, but is irradiated to other regions.

  In the display device 1, it is measured in advance how much the light emission luminance of each light source 8 </ b> A, 8 </ b> B,..., 8 </ b> X contributes to the display luminance of the regions a to x, and this measured value will be described later. This data is stored in the memory 11 as data when calculating with simultaneous equations. Therefore, the memory 11 stores the data of the luminance contribution ratio shown in FIG.

  Next, an example of control processing related to screen display will be described with reference to the flowchart of FIG. This control is executed by the liquid crystal panel control circuit 14 and the light source control circuit 9 of the control unit 4 and is performed each time an image signal of one field is input to the liquid crystal panel control circuit 14.

  When an image signal of one field is input to the liquid crystal panel control circuit 14 (step S1), the distribution of display luminance of one image (original image) generated by the input image signal is detected by the liquid crystal panel control circuit 14. (Step S2). At this time, the height of the highest display luminance and the position showing the highest display luminance in each of the areas a to x are detected.

  Based on the detected maximum display brightness and the position indicating the maximum display brightness, the light emission brightness of each of the light sources 8A, 8B,..., 8X constituting the backlight 3 is set (step S3). When setting the light emission luminance, the luminance contribution ratio of the light emission luminances of the light sources 8A, 8B,..., 8X with respect to the display luminances of the regions a to x is considered. Specifically, the light emission luminance of each of the light sources 8A, 8B,..., 8X is set by simultaneous equations using the luminance contribution ratio data (see FIG. 6) stored in advance in the memory 11. A specific example of simultaneous equations will be described later.

  Next, after setting the light emission luminance of each of the light sources 8A, 8B,..., 8X as described above, the display luminance of each part of the display screen of the liquid crystal panel 5 is set to an optimum value at the time of image display. A correction value for each pixel is calculated (step S4).

  The correction value is calculated based on the amount of deviation between the set light emission brightness of each of the light sources 8A, 8B,. The optimum value is the display brightness required in each part of the display screen when the original image is displayed based on the input image signal. Therefore, the correction value is used to obtain display brightness required in each part of the display screen when light is emitted from the light sources 8A, 8B,..., 8X with the light emission brightness set as described above. Is a value for calculating the aperture ratio required for each pixel.

  At the time of calculating the correction value, data for correcting display unevenness of the liquid crystal panel 5 is read from the memory 11, and the correction value is calculated in consideration of this data.

  A light emission drive signal based on the light emission luminance of each light source 8A, 8B,..., 8X set in step S3 is sent from the light source control circuit 9 to each light source 8A, 8B,. , 8B,..., 8X are caused to emit light with the set light emission luminance. At the same time, the display drive signal corrected based on the correction value calculated in step S4 is sent from the liquid crystal panel control circuit 14 to each pixel of the liquid crystal panel 5, and an image of each field is displayed on the display screen (step S5). When a display drive signal is sent from the liquid crystal panel control circuit 14 to each pixel of the liquid crystal panel 5, each pixel is controlled to have an aperture ratio based on the display drive signal, and each light source 8A, 8B,. The transmission state with respect to each pixel of the light emitted from 8X is controlled.

  Therefore, an image is displayed in each part of the display screen in a state where display luminance corresponding to the input image signal is obtained.

  Below, the concrete method of the control performed in above-mentioned step S1-step S5 (refer FIG. 7) is demonstrated.

  For each of the regions a to x, the maximum display luminance Ln_max (n = 1 to 24) determined by the input image signal is obtained. The maximum display brightness Ln_max is a value that provides the maximum display brightness in each part of the regions a to x. At the same time, a position indicating the maximum display luminance Ln_max is detected for each of the regions a to x.

  Here, the display brightness of all white (when the white peak is set for both the liquid crystal panel and the backlight (usually when the aperture ratio of the liquid crystal panel is 100% and the output of the backlight is 100%)) is L_peak, and each area a to x of the display screen The ratio αn (n = 1 to 24) of the maximum display brightness Ln_max with respect to the display brightness L_peak of all white is obtained.

αn = (Ln_max / L_peak) (1)
The ratio αn is a recovery limit indicating how much the light emission luminance of the light sources 8A, 8B,..., 8X corresponding to the regions a to x can be suppressed. That is, the display brightness of the liquid crystal panel 5 is determined by “aperture ratio of the liquid crystal panel (including the polarizing plate) × backlight emission brightness”, but the recovery limit is that if the backlight emission brightness is further reduced, Even if the aperture ratio is set to 100%, the maximum display luminance Ln_max cannot be obtained.

  In the above description, the value of the recovery limit αn is obtained based on the maximum display luminance Ln_max of each of the areas a to x. However, depending on the image content, αn ′ = based on the average display luminance Ln_ave of each of the areas a to x. It is also possible to perform luminance control by obtaining the value of the recovery limit αn ′ by (Ln_ave / L_peak). In the case of performing control by obtaining the value of the recovery limit αn ′, it is difficult to reproduce a complete original image, but it is possible to reproduce the original image in a range that does not affect the appearance.

  As described above, the display brightness of each of the regions a to x includes the light sources 8A, 8B,..., 8X other than the light sources 8A, 8B,. .. Since the light emission luminance of 8X also contributes, the light emission luminance of the light sources 8A, 8B,..., 8X located immediately behind each region ax is controlled separately according to the recovery limit αn of the regions ax. Alone cannot perform control in consideration of the light emission luminance of the light sources 8A, 8B,..., 8X that are not located immediately after the regions a to x.

  Therefore, considering the light emission luminance of the light sources 8A, 8B,..., 8X not located immediately after the regions a to x, the light emission rate βn (n = 1 to 24) for each of the light sources 8A, 8B,. ) The light emission rate βn is a value indicating the ratio of the actual light emission luminance of each light source 8A, 8B,..., 8X to the maximum light emission luminance (when white peak is set) of each light source 8A, 8B,. Yes, it is obtained in the range of 0 ≦ βn ≦ 1. For example, β1 is the light emission rate of the light source 8A, and β3 is the light emission rate of the light source 8C.

The light emission rate βn is calculated using the luminance contribution ratios K _{X and Y} (see FIG. 6) of the light sources 8A, 8B,. The luminance contribution rate data of the light sources 8A, 8B,..., 8X shown in FIG. 6 is stored in advance in the memory 11 as described above, and the light source stored in the memory 11 when the light emission rate βn is calculated. 8A, 8B,..., 8X luminance contribution rate data is read out.

In the luminance contribution ratios K _{X and Y} , both X and Y are represented by natural numbers of 1 to 24, X indicates the regions a to x, and Y indicates the light sources 8A, 8B,. For example, K _{1 and 1} indicate the luminance contribution ratio of the light source 8A to the area a, and K _{3 and 7} indicate the luminance contribution ratio of the light source 8G to the area c. As shown in FIG. 6, the luminance contribution ratio is not constant in each region for each of the light sources 8A, 8B,..., 8X, but the luminance contribution ratios K _{X and Y in} the memory 11 are, for example, , Data at the center of each of the areas a to x is stored.

The light emission rate βn is obtained by solving the following multiple simultaneous equations (inequality).
_{K 1,1 · β1 + K 1,2 ·} β2 + K 1,3 · β3 + ··· + K 1,24 · β24 ≧ α1
K ₂ , ₁ · β 1 + K ₂ , ₂ · β 2 + K _2,3 · β 3+... + K ₂ , ₂₄ · β ₂₄ ≧ α 2
K _3,1 · β1 + K _3,2 , β2 + K _3,3 · β3 + ... + K _3,24 · β24 ≧ α3
・
・
・
K ₂₃ , 1 · β 1 + K ₂₃ , 2 · β 2 + K ₂₃ , 3 · β 3+... + K ₂₃ , ₂₄ · β ₂₄ ≧ α ₂₃
K ₂₄ , ₁ · β 1 + K ₂₄ , ₂ · β 2 + K ₂₄ , ₃ · β 3+... + K ₂₄ , ₂₄ · β ₂₄ ≧ α ₂₄
... (2)
The multiple simultaneous equations described above can be used regardless of the configuration of the backlight because the number of n only changes depending on the number of divisions of the backlight.

  Next, the light emission rate βn (0 ≦ βn ≦ 1) is corrected. This correction is performed when there is a position indicating the maximum display luminance Ln_max in an enlarged region overlapping with an adjacent region in each of the regions a to x. , For the corresponding area. For example, as shown in FIG. 8, when the position P indicating the maximum display luminance in the area a exists at the end of the area a on the area b side, the position P also exists in the enlarged area of the area b. Become. The light source 8A positioned corresponding to the region a emits light at a light emission rate β1 that provides the maximum display luminance when the position P is assumed to be positioned at the center of the region a, and the light emission luminance M is obtained. At this time, when the maximum display luminance in the region b is lower than the maximum display luminance in the region a, the light source 8B positioned corresponding to the region b adjacent to the region a also emits light with the same light emission rate β1 as that of the light source 8A. The light emission rate β is corrected and set as described above. The light emission rate β1 of the light source 8A is a value obtained in consideration of the luminance contribution rate of the light emission luminance of each of the light sources 8B,.

  When there is a position showing the maximum display brightness in the enlarged area in this way, the maximum display brightness in both areas is compared, and the light sources 8 and 8 positioned corresponding to the adjacent areas are set to the higher one. Correction to match the light emission rate β is performed to set the light emission rate β.

  FIG. 9 shows the light emission luminance of the light sources 8A and 8B set by correcting the light emission rate β as described above. The graph shown by the two-dot difference line in FIG. 9 shows the total light emission luminance of the light emission luminances of the light sources 8A and 8B, and is required even when the position of the maximum display luminance exists in the portion near the outer periphery of each region. The light emission luminance M can be obtained, and the maximum display luminance in the portion near the outer periphery can be ensured.

  In addition, when the maximum display luminance exists at a position other than the portion near the outer periphery in the original region, the emission luminance corresponding to the center of the original region and the emission luminance corresponding to the boundary of the enlarged region with respect to the light emission rate β of the region. Correct by adding the ratio of to. For example, as shown in FIG. 10, when the position P indicating the maximum display luminance in the region a exists in a portion other than the enlarged region b2 in the original region a1, the emission luminance corresponding to the center Am of the original region a1 A ratio with the light emission luminance corresponding to the boundary As of the enlarged region b2 is calculated, and the light emission rate β1 is corrected by adding this ratio.

  FIG. 11 shows the light emission luminance of the light source 8A set by correcting the light emission rate β as described above. The added portion is a portion indicated by hatching in FIG. 11. The added portion is not the ratio of the emission luminance corresponding to the center Am and the emission luminance corresponding to the boundary Ap of the adjacent original region (see FIG. 10), but the center Am. Since it is based on the ratio of the light emission luminance corresponding to the light emission luminance corresponding to the boundary As, it can be small. Therefore, the increase in light emission luminance can be minimized, and the light emission efficiency can be improved.

  When the light emission rate βn (0 ≦ βn ≦ 1) corrected as described above is obtained, the light emission luminances of the light sources 8A, 8B,..., 8X are set so as to satisfy the light emission rate βn.

  In addition, although the example which calculates | requires (beta) n for every light source 8A, 8B, ..., 8X was shown above, for example, for every primary color of red, green, blue, or every luminescent color of the backlight 3, (beta) n It is also possible to perform brightness control by calculating.

  In the above example, the recovery limit αn is calculated, and then the light emission rate βn (0 ≦ βn ≦ 1) is corrected. You may make it calculate using (Formula (2)).

  After calculating the light emission rate βn as described above and setting the light emission luminance of each light source 8A, 8B,..., 8X, the display luminance of each part of the display screen of the liquid crystal panel 5 is displayed as an image as shown below. A correction value for each pixel to obtain an optimum value at the time of calculation is calculated. As described above, this correction value is displayed in each part of the display screen when light is emitted from the light sources 8A, 8B,..., 8X with the light emission luminance set as described above. This is a value for calculating the aperture ratio required for each pixel in order to obtain luminance.

  The correction value is calculated based on data on display luminance characteristics of the liquid crystal panel 5 shown in FIG. In FIG. 12, the horizontal axis indicates the set gradation (voltage) S_data of the liquid crystal panel 5 when the output of the backlight 3 is 100% (when fully lit), and the vertical axis indicates the liquid crystal panel 5 with respect to the set gradation S_data. Display luminance L_data is shown. Data of the display luminance characteristic f shown in FIG. 12 is obtained in advance and stored in the memory 11.

  For each pixel, γ is the ratio between the display brightness L_peak of all white and the set display brightness L_set. The set display luminance L_set is the display luminance when the pixel has an aperture ratio of 100% when light is emitted from the light sources 8A, 8B,..., 8X in which the light emission luminance is set based on the light emission rate βn. Say.

γ = L_peak / L_set (3)
As described above, the set gradation S_data of the image (original image) displayed when the image signal is input is determined based on the display luminance L_data by the data shown in FIG.

L_data = f (S_data) (4)
The corrected set gradation S_data ′ with respect to the set display brightness L_set is calculated by the following expression based on the ratio γ between the display brightness L_peak of all white and the set display brightness L_set and the set gradation S_data. The correction setting gradation S_data ′ is a correction value for calculating the aperture ratio required for each pixel.

S_data ′ = f (γ × L_data) ⁻¹ (5)
By setting the aperture ratio of each pixel so that the corrected set gradation S_data ′ is obtained, the original image is reproduced with a predetermined display luminance.

  In the display device 1, processing for correcting display unevenness of the liquid crystal panel 5 is performed as follows when calculating the correction amount for each pixel described above.

  When the liquid crystal panel 5 has an all white display luminance L_peak, display unevenness occurs in the liquid crystal panel 5. This display unevenness is caused by component parts involved in the display brightness of the liquid crystal panel 5, for example, molding accuracy of pixels (liquid crystal) and each light source.

  Hereinafter, a method of preventing display unevenness will be described (see FIGS. 13 and 14).

  As shown in FIG. 13, in the display brightness of each part of the display screen, the minimum value of the display brightness L_peak of all white is defined as the uniform display brightness L_flat. At this time, if there is a part where the display brightness is specifically low in each part of the display screen, the uniform display brightness L_flat may be set ignoring the low display brightness.

  Next, the ratio H (= L_flat / L_peak) of the uniform display luminance L_flat with respect to the display luminance L_peak of all white is calculated for each pixel, and this ratio H is stored in the memory 11 as the unevenness correction coefficient.

  FIG. 14 shows the unevenness correction coefficient H calculated for the display luminance state of FIG.

  By calculating the unevenness correction coefficient H as described above and calculating the correction setting gradation S_data ′ including the unevenness correction coefficient H by the following calculation formula, display unevenness of the liquid crystal panel 5 can be prevented.

S_data ′ = f (H × γ × L_data) ⁻¹ (6)
As described above, the display device 1 controls the light emission luminance of each light source 8A, 8B,..., 8X and the aperture ratio of each pixel of the liquid crystal panel 5 in accordance with the input image signal. Therefore, the image quality displayed on the liquid crystal panel 5 can be improved while reducing power consumption.

  Moreover, although the light emission brightness | luminance of each light source 8A, 8B, ..., 8X which comprises the backlight 3 is controlled separately, the light each radiate | emitted from each light source 8A, 8B, ..., 8X is divided. Since it is not configured, a simple configuration similar to that of a conventional liquid crystal display device that does not perform light amount control can be achieved.

  Further, the display device 1 also performs a process of correcting display unevenness of the liquid crystal panel 5 when controlling the light emission luminance of the light sources 8A, 8B,..., 8X and the aperture ratio of each pixel of the liquid crystal panel 5. Therefore, the image quality can be further improved.

  In addition, in the display device 1, data for correcting display unevenness of the liquid crystal panel 5, data on the distribution state of light emitted from the light sources 8A, 8B, ..., 8X, the light sources 8A, 8B, Since different types of data such as luminance contribution ratio data indicating how much the emission luminance of 8X contributes to the display luminance of the regions a to x are stored in one memory 11, Control operations can be performed without increasing the cost without requiring a plurality of memories for storing each of these data separately.

  Next, a control example for expanding the dynamic range with respect to the light emission luminance control amount of the light sources 8A, 8B,..., 8X and the correction amount for each pixel will be described (see FIGS. 15 and 16).

  In the above, the data shown in FIG. 12 is used as the display luminance characteristic data stored in the memory 11, but the dynamic range can be expanded by using other data as the display luminance characteristic data stored in the memory 11. Is possible.

  The data shown in FIG. 12 is data having a display luminance characteristic f expressing black (black level) in a state where the backlight 3 is lit. For example, as shown in FIG. It is also possible to use data having a display luminance characteristic f ′ that represents a black level in a state where the light is turned off. By using such data, the dynamic range can be expanded regarding the control amount of the light emission luminance of the light sources 8A, 8B,..., 8X and the correction amount for each pixel.

  With reference to the flowchart of FIG. 16, an example of control processing related to screen display when the dynamic range is expanded with respect to the control amount of the light emission luminance of the light sources 8A, 8B,. . This control is executed by the liquid crystal panel control circuit 14 and the light source control circuit 9 of the control unit 4 and is performed each time an image signal of one field is input to the liquid crystal panel control circuit 14.

  First, steps S11 to S13 are sequentially performed. The processing of step S11 to step S13 is the same as the processing of step S1 to step 3 shown in FIG.

  Next, a correction value is calculated for each pixel in order to set the display brightness of each part of the display screen of the liquid crystal panel 5 to an optimum value for image display (step S14). This correction value is calculated by reading data having the display luminance characteristic f ′ shown in FIG. The calculation of the correction value is performed using the data having the display luminance characteristic f ′ shown in FIG. 15, so that the control range of the light emission luminance of the light sources 8A, 8B,. Is enlarged (step S15).

  Next, the display drive signal corrected based on the correction values calculated in step S14 and step S15 is sent from the liquid crystal panel control circuit 14 to each pixel of the liquid crystal panel 5, and an image of each field is displayed on the display screen (step). S16). When a display drive signal is sent from the liquid crystal panel control circuit 14 to each pixel of the liquid crystal panel 5, each pixel is controlled to have an aperture ratio based on the display drive signal, and each light source 8A, 8B,. The transmission state with respect to each pixel of the light emitted from 8X is controlled. The process of step S16 is the same as the process of step 5 in FIG.

  As described above, the image quality can be improved by expanding the dynamic range related to the control amount of the light emission luminance of the light sources 8A, 8B,..., 8X and the correction amount for each pixel. Note that the dynamic range expansion processing can be performed for each primary color of red, green, and blue or for each emission color of the backlight 3, for example.

Next, an example of control when an enlarged area is formed for each of the areas a to x on the display screen and this enlarged area is divided into two areas will be described (see FIGS. 17 to 21).
In the control example when the enlarged region is divided, the light emission rate βn (0 ≦ βn ≦ 1) is calculated using the multiple simultaneous equations (formula (2)) after correcting the recovery limit αn. Therefore, in the following description of the control example when the enlarged region is divided, only the method for correcting the recovery limit αn will be described in detail.

  As shown in FIG. 17, each of the areas a to x includes an original area 12 (a portion with a diagonal line rising to the right) formed by dividing the display screen into equal parts, and a first enlargement located outside the original area 12. The region 13 (upward left slanted line portion) and the second enlarged region 14 (the satin portion) located outside the first enlarged region 13 are configured. In FIG. 17, the area delimited by the dotted line indicates the original area 12, the area excluding the original area 12 among the areas delimited by the two-dot chain line indicates the first enlarged area 13, and the original area among the areas delimited by the solid line A region excluding the region 12 and the first enlarged region 13 indicates a second enlarged region 14.

  The recovery limit αn is corrected according to the position indicating the maximum display luminance Ln_max in each of the areas a to x.

  For example, it is assumed that the maximum display brightness of the original area 12 of the divided areas a to x is as shown in FIG. In FIG. 18, the point mark indicates the position of the maximum display brightness in the original area 12 of each of the areas a to x, and the numerical value indicates the height of the maximum display brightness. The maximum display brightness is higher as the numerical value is smaller.

  FIG. 19 is a chart collectively showing the state of the maximum display luminance and the like shown in FIG. In FIG. 19, “region” from the left side indicates each region a to x, “original region” indicates the height of the maximum display brightness in the original region 12 of each region a to x, and “first enlarged region” is The maximum display luminance is shown when each of the areas a to x is enlarged to the first enlarged area 13, and the “second enlarged area” is when each of the areas a to x is enlarged to the second enlarged area 14. Indicates the maximum display brightness of.

  For example, for the area i, the maximum display brightness in the original area 12 is “1”, and the maximum display brightness when the area is expanded to the first enlargement area 13 is also “1”. When the display area is enlarged to the second enlargement area 14, the maximum display brightness “22” of the area j is included, but the maximum display brightness “1” is higher than the maximum display brightness “22”. Even when the image is enlarged, the maximum display luminance is “1”. For the area r, the maximum display brightness in the original area 12 is “24”, and the maximum display brightness when the display area is expanded to the first enlargement area 13 is also “24”. When the second display area 14 is expanded, the maximum display brightness “20” of the area l is included, and the maximum display brightness “20” is higher than the maximum display brightness “24”. In this case, the maximum display brightness is “20”.

  In FIG. 19, “equivalent area” indicates which area a to x is viewed as the same as, and “position” indicates the position of the maximum display luminance in the original area 12 of each area a to x below. The area A to D shown in FIG.

  The areas A to D are determined as shown in FIG. 20. In each of the areas a to x, the outermost area of the original area 12 is the area A, and the area inside the area A is the area B. The rectangular area inside area B is area C or area D. Area A is an area corresponding to the first enlarged region 13 in the adjacent region, area B is an area corresponding to the second enlarged region 14 in the adjacent region, and areas C and D are the first in the adjacent region. This is an area that does not correspond to the one enlarged region 13 or the second enlarged region 14.

  In the area where the “position” is determined as the area A, the recovery limit α is set to the same setting as the recovery limit α in the corresponding “equivalent area”. In an area where “position” is determined as area B, processing for setting the recovery limit α in that area to P times is performed. In the area where the “position” is determined as the area C, a process for setting the recovery limit α in the area to Q (Q <P) times is performed. In the area where the “position” is determined as the area D, no particular processing is performed, and the recovery limit α is not changed.

  The value of P in the area determined as the area B is 1.3, for example, and the value of Q in the area determined as the area C is, for example, 1.03. P and Q are the additions shown in FIG. 11, and P and Q are the emission luminance corresponding to the center of the original region 12 and the emission luminance corresponding to the boundary between the first enlarged region 13 or the second enlarged region 14. It can be set to an arbitrary value according to the ratio.

  Hereinafter, a procedure of processing relating to which of the areas A to D is determined for each of the areas a to x will be described (see FIG. 21). In the following procedure, it will be described together with which area each of the regions a to x is determined based on the specific examples shown in FIGS. 19 and 20.

  (S1) The process is started, and it is detected whether or not the first display area 13 has a maximum display brightness in another adjacent area higher than the maximum display brightness in the original area 12. If the presence is detected, the process proceeds to (S2), and if the presence is not detected, the process proceeds to (S3). Specifically, the regions b, j, k, p, u, and x shift to (S2), and the other regions a, c, d, e, f, g, h, i, l, m, n, o, q, r, s, t, v, w shift to (S3). The areas b, j, k, p, u, and x that are detected to be present are determined as a, d, e, v, t, and w in which “equivalent areas” respectively correspond to other areas.

  (S2) The area corresponding to the other area is determined as area A in (S1) with respect to the area detected to exist in (S1). Specifically, the regions b, j, k, p, u, x detected to exist in (S1) and the regions a, d, e, t, v, corresponding to other regions in (S1). w is determined as area A. When the corresponding area is determined as area A, the process is terminated.

  (S3) It is detected whether or not the second display area 14 has a maximum display brightness in another adjacent area higher than the maximum display brightness in the original area 12. If the presence is detected, the process proceeds to (S4), and if the presence is not detected, the process proceeds to (S9). Specifically, the regions c, e, g, n, r, s, and w move to (S4), and the regions a, d, f, h, i, l, m, o, q, t, and v are changed. The process proceeds to (S9).

  (S4) Whether or not the area A has already been determined is detected. If it is detected that it has been determined, the process proceeds to (S4 ′), and if it is not detected that it has been determined, the process proceeds to (S6). Specifically, the areas e and w determined as the area A in (S2) shift to (S4 ′), and the areas c, g, n, r, and s shift to (S6).

  (S4 ′) It is detected whether or not an area corresponding to another area is already determined as area A with respect to the area detected to exist in (S4). If it is detected that it is determined, the process proceeds to (S5), and if it is not detected that it is determined, the process proceeds to (S5 '). Specifically, the area e that has already been determined to be the area A in (S2) has shifted to (S5), and the area q that corresponds to the other area has been determined to be the area A. The area w that does not exist shifts to (S5 ′).

  (S5) Since the area A has already been determined, no particular process is performed and the process is terminated. Specifically, the area e remains the area A.

  (S5 ′) An area corresponding to another area is determined as area B. Specifically, a region q corresponding to another region w is determined as area B.

  (S6) It is detected whether or not an area corresponding to another area is already determined as area A with respect to the area detected to exist in (S3). If it is detected that it is determined, the process proceeds to (S8), and if it is not detected that it is determined, the process proceeds to (S7). Specifically, the regions c and n shift to (S8), and the regions g, r, and s shift to (S7).

  (S7) A region that is not detected to be determined in (S6) is determined as area D, and a region corresponding to another region is determined as area B in (S6). Specifically, the areas g, r, and s are determined as the area D, the areas h, l, and n are determined as the area B, and the process ends.

  (S8) The area c detected to be determined in (S6) is determined as the area D. The area n is also an area that has been determined to have been determined in (S6), but since it has already been determined to be area B in (S7), area n remains area B and the process ends.

  (S9) Whether the area A or the area B has already been determined is detected. If it is detected that it is determined, the process proceeds to (S10), and if it is not detected that it is determined, the process proceeds to (S11). Specifically, the areas a, d, t, v determined in area A in (S2), the areas h, l determined in area B in (S7), and the area B in (S5 ′). The region q shifts to (S10), and the regions f, i, m, and o shift to (S11).

  (S10) Since the area A or the area B has already been determined, the process is not performed and the process ends. Specifically, the areas a, d, t, and v remain in the area A, and the areas h, l, and q remain in the area B.

  (S11) Regions f, i, m, and o that are not detected to be determined in (S9) are determined as area C, and the process ends.

  When the areas a to x are determined as described above, the recovery limit α in the area determined as the area A is set to be the same as the recovery limit α in the corresponding equivalent area and is determined as the area B. The recovery limit α in the area is set to P times, the recovery limit α in the area determined for the area C is set to Q times, and the recovery limit α in the area determined for the area D is set unchanged.

  Based on the recovery limit α set as described above, the light emission rate βn (0 ≦ βn ≦ 1) is calculated using the multiple simultaneous equations (formula (2)).

  In the above example, the number of divisions of the display screen area is set to 24. However, the number of divisions of the area is not limited to 24 and is arbitrary.

  Moreover, although the example which set the expansion area to one or two was shown above, the number of expansion areas can also be set arbitrarily.

  The specific shapes and structures of the respective parts shown in the above-described best mode are merely examples of the implementation of the present invention, and the technical scope of the present invention is limited by these. It should not be interpreted in a general way.

FIG. 2 to FIG. 21 show the best mode of the present invention, which is a conceptual diagram showing the configuration of a liquid crystal display device. It is a conceptual diagram which shows a display screen and each light source. It is a conceptual diagram which shows the division | segmentation state of the area | region of a display screen. It is a graph which shows the light emission luminance of the light source with respect to each position of a display screen. It is a graph which shows the light emission brightness | luminance of the light source with respect to each position of a display screen when the influence of reflection is considered. It is a graph which shows the luminance contribution rate of the light source with respect to each position of a display screen. It is a flowchart figure which shows the procedure of control. It is a conceptual diagram which shows the example in which the position of the maximum display brightness exists in an expansion area. FIG. 9 is a graph showing the light emission luminance of the light source set by correcting the light emission rate based on the state of FIG. 8. It is a conceptual diagram which shows the example in which the position of the maximum display brightness exists in an original area. It is the graph which showed the light emission luminance of the light source which correct | amended the light emission rate based on the state of FIG. 10, and was set. It is a graph which shows a display luminance characteristic. It is for demonstrating the process which correct | amends display nonuniformity with FIG. 14, This figure is a graph which shows the display brightness | luminance of all white, and a uniform display brightness | luminance. It is a graph which shows a uniform display brightness | luminance and a nonuniformity correction coefficient. It is a graph which shows the display luminance characteristic which expands a dynamic range. It is a flowchart figure which shows the procedure of control when expanding a dynamic range. It is a conceptual diagram which shows the division | segmentation state of the area | region of a display screen when two enlarged areas are set. As an example, it is a conceptual diagram showing the position of the maximum display luminance in each region. FIG. 19 is a chart collectively showing a state of maximum display luminance and the like in FIG. 18. It is a conceptual diagram which shows the area in an original area. It is a flowchart figure which shows the procedure of the process regarding which area is determined for each area | region. It is a figure which shows the example of the light emission state of the example of an image, and the conventional backlight. It is a graph which shows an example of the light emission luminance in the conventional display apparatus. It is a graph which shows the problem in the conventional display apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display device, 2 ... Display part, 3 ... Back light, 4 ... Control part, 8A-8X ... Light source, 13 ... 1st expansion area, 14 ... 2nd expansion area

Claims (6)

Each divided area has a display screen divided into a plurality of areas, is controlled in pixel units and has an aperture ratio, and each divided area is provided with an enlarged area that overlaps with the adjacent divided areas. The display area is set including the enlarged area,
A backlight configured to illuminate the back surface of the display unit and includes a plurality of light sources arranged separately corresponding to the plurality of divided regions of the display unit;
When an image is displayed on the display screen based on the input image signal, the display brightness in each divided area of the display unit is detected, and the light emission brightness of each light source arranged corresponding to each divided area is adjacent. The light emission of each light source arranged corresponding to each divided area is calculated according to the position showing the maximum display luminance in each divided area including the influence of the other light sources arranged corresponding to the divided areas on the corresponding area. The brightness is set to the calculated light emission brightness, the correction amount for each pixel of the display unit is calculated based on the amount of deviation between the set light emission brightness and the optimum value of the display brightness in each part of the display screen, and the calculated correction amount And a control unit that controls the aperture ratio of each pixel by sending a display drive signal generated based on the above to each pixel. Divide the enlarged area in each divided area into multiple areas ,
2. The display device according to claim 1 , wherein when a position indicating the maximum display brightness exists in each of the plurality of divided areas, the light emission brightness corresponding to each of the areas is calculated . The above calculation of the light emission luminance of each light source including the influence of other light sources on the region is performed by simultaneous equations using the luminance contribution ratio in which the light emission luminances of all light sources contribute to the region. The display device according to claim 1. The controller controls the dynamic range of display luminance in each divided area of the display unit when an image signal is input from the state where the light emission luminance of each light source arranged corresponding to each divided area is substantially zero. The display device according to claim 1, wherein the display brightness in each divided area of the display unit is detected by assigning the display state up to the state of the display unit. A display unit having a display screen divided into a plurality of areas and controlled in pixel units to set an aperture ratio, and the back surface of the display unit is illuminated and arranged separately for each of the plurality of areas of the display unit An image display method in a display device including a backlight configured by a plurality of light sources,
In each divided area of the display unit, an enlarged area that overlaps with the adjacent divided areas is provided, and the area range of each divided area is set including the enlarged area,
By controller
When the image is displayed on the display screen based on the input image signal, the display brightness in each divided area of the display unit is detected,
The light emission luminance of each light source arranged corresponding to each divided region is set to a position showing the maximum display luminance in each divided region including the influence of the other light sources arranged corresponding to the adjacent divided regions on the relevant region. Calculate accordingly,
Set the emission luminance of each light source arranged corresponding to each divided area to the calculated emission luminance,
Calculate the correction amount for each pixel of the display unit based on the amount of deviation between the set emission luminance and the optimum value of the display luminance in each part of the display screen,
A display method, wherein a display drive signal generated based on the calculated correction amount is sent to each pixel to control an aperture ratio of each pixel. The display method according to claim 5, wherein the control unit performs a process of correcting display unevenness of the display unit when calculating a correction amount for each pixel of the display unit.

Images