Patent Grant
10049610
Field of the Invention
The present invention relates to a display apparatus and a method for controlling the same.
Description of the Related Art
In some display apparatuses such as liquid crystal displays using a backlight, the backlight is constituted by a plurality of light sources whose brightness is capable of being separately controlled. Such display apparatuses may improve display contrast by controlling the brightness of respective light sources according to input images and correcting the input images according to the brightness of the respective light sources (see, for example, Japanese Patent Application Laid-open No. 2008-51905). This technology is called local dimming. However, image correction may cause degradation in original input images due to influence by, for example, quantization error or the like.
Liquid crystal displays have also been used for interpretation with X-ray or mammography. In such medical image observation, it is required to faithfully display original input images for accurate diagnosis. However, if display images are degraded due to image processing, the faithful display of the images is not allowed.
In view of this problem, there has been proposed technology in which local dimming is applied only to light sources corresponding to background regions not to be observed and is not applied to light sources corresponding to object regions to be observed in input images (see, for example, Japanese Patent Application Laid-open No. 2013-148870). Thus, since black floating caused by light leaking from a liquid crystal display is prevented in dark background regions, an observer such as an interpretation operator may be free from the feelings of interference. In addition, since degradation due to image processing is prevented in object regions and input images are faithfully displayed, diagnosis with precision is made possible.
There may be cases that images other than medical images are displayed and used on liquid crystal displays on which the medical images are observed. For example, when an image of an operating system (OS) output from a personal computer or the like is displayed, it may include a text display region in which bright-color texts are displayed in a dark-color background. In the technology of Japanese Patent Application Laid-open No. 2013-148870, there is a likelihood that the background of a text display region is falsely recognized as the background of medical images and local dimming is applied to the text display region. As a result, the brightness of light sources corresponding to the text display region reduces, and light leaks from light sources having high brightness around the text display region to cause halo in the text display region. In addition, for images other than medical images, there is a likelihood that image producers intend to give expression full of gradation even in dark regions. However, when the brightness of light sources corresponding to the dark regions reduces, gradation expected by the image producers is not successfully displayed in the dark regions. As described above, there is a likelihood that observers have the feelings of interference at displaying images other than medical images in the related art.
Accordingly, the present invention performs appropriate brightness control according to types of images to prevent observers from having the feelings of interference in a display apparatus capable of separately controlling the brightness of the light sources of a backlight according to the images.
According to a first aspect of the present invention, there is provided a display apparatus including:
a display panel;
a light emitting unit having a plurality of light sources and separately adjusting brightness of the respective light sources;
an acquiring unit configured to acquire a feature value of an input image for divided regions respectively corresponding to the plurality of light sources; and
a control unit configured to make, in a case where the input image is a first image including a predetermined object image, brightness of light sources corresponding to divided regions determined to be dark regions based on the feature values of the respective divided regions lower than brightness of light sources corresponding to other divided regions, wherein
in a case where the input image is a second image not including the predetermined object image, the control unit does not implement control operation of making the brightness of the light sources corresponding to the divided regions determined to be the dark regions lower than the brightness of the light sources corresponding to the other divided regions.
According to a second aspect of the present invention, there is provided a method for controlling a display apparatus having a display panel and a light emitting unit having a plurality of light sources and separately adjusting brightness of the respective light sources, the method comprising:
acquiring feature values of an input image for divided regions respectively corresponding to the plurality of light sources; and
implementing a control operation of making, in a case where the input image is a first image including a predetermined object image, brightness of light sources corresponding to divided regions determined to be dark regions based on the feature values of the respective divided regions lower than brightness of light sources corresponding to other divided regions, wherein
in a case where the input image is a second image not including the predetermined object image, the control operation of making the brightness of the light sources corresponding to the divided regions determined to be the dark regions lower than the brightness of the light sources corresponding to the other divided regions is not implemented.
According to a third aspect of the present invention, there is provided a display apparatus including:
a display panel;
a light emitting unit having a plurality of light sources and separately adjusting brightness of the respective light sources;
an acquiring unit configured to acquire feature values of an input image for divided regions respectively corresponding to the plurality of light sources; and
a control unit configured to make, within a region displaying a first image including a predetermined object image in the input image, brightness of light sources corresponding to divided regions determined to be dark regions based on the feature values of the respective divided regions lower than brightness of light sources corresponding to other divided regions, wherein
within a region displaying a second image not including the predetermined object image in the input image, the control unit does not implement control operation of making the brightness of the light sources corresponding to the divided regions determined to be the dark regions lower than the brightness of the light sources corresponding to the other divided regions.
According to a fourth aspect of the present invention, there is provided a method for controlling a display apparatus having a display panel and a light emitting unit having a plurality of light sources and separately adjusting brightness of the respective light sources, the method comprising:
acquiring feature values of an input image for divided regions respectively corresponding to the plurality of light sources; and
implementing a control operation of making, within a region displaying a first image including a predetermined object image in the input image, brightness of light sources corresponding to divided regions determined to be dark regions based on the feature values of the respective divided regions lower than brightness of light sources corresponding to other divided regions, wherein
within a region displaying a second image not including the predetermined object image of the input image, the control operation of making the brightness of the light sources corresponding to the divided regions determined to be the dark regions lower than the brightness of the light sources corresponding to the other divided regions is not implemented.
According to an embodiment of the present invention, it is possible to perform appropriate brightness control according to types of images to prevent observers from having the feelings of interference in a display apparatus capable of separately controlling the brightness of the light sources of a backlight according to the images.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Hereinafter, a description will be given of an embodiment of the present invention with reference to the drawings.
The display apparatus of a first embodiment divides an input image into a plurality of regions, detects the feature values of the respective divided regions of the image, and determines whether the input image is an image (first image) including a predetermined object image from the detected feature values. An object is, for example, an image of an object taken by radiation or ultrasonic waves, and an image including the object is, for example, a medical image for interpretation (interpretation image) such as an X-ray image. When determining that the input image is the medical image, the display apparatus determines whether the respective divided regions are object regions in which a predetermined object image (object to be interpreted) exists or background regions indicating the background of the predetermined object image. The display apparatus determines the brightness of a plurality of light sources constituting a backlight according to determination results. Thus, the display apparatus reduces the floating of dark parts in the background regions that are not to be observed in the medical image and reduces the feelings of interference when an observer (interpretation operator or the like) interprets the medical image displayed on the display apparatus.
The liquid crystal panel section 1 includes a liquid crystal driver, a control substrate that controls the liquid crystal driver according to an input image signal, and a liquid crystal panel. Note that although the first embodiment describes an example using the liquid crystal panel as the display panel of the present invention, the display panel is not limited to the liquid crystal panel.
The backlight module section 2 includes light sources, a control circuit that controls the light sources, and an optical unit that diffuses light from the light sources. The backlight module section 2 has the plurality of light sources and is capable of separately adjusting the light emission brightness of the respective light sources. The backlight module section 2 is divided into a plurality of blocks corresponding to the respective light sources whose brightness is capable of being separately controlled, and the brightness of the respective blocks is determined by the backlight brightness value determination section 7. The control circuit of the backlight module section 2 controls the light emission of the respective light sources such that the respective light sources light up with the brightness determined by the backlight brightness value determination section 7. A block-based division number is m (width)×n (length) (where m and n are integers). In the first embodiment, it is assumed that the backlight module section 2 is divided into 10 (width)×7 (length) blocks. In addition, it is assumed that a region (divided region) of the liquid crystal panel section 1 corresponding to each of the blocks has 20 (width)×20 (length)=400 pixels. The number of the divided blocks of the backlight module section 2 may include but not limited to the above number.
The feature value detection section 3 divides the input image into regions (divided regions) corresponding to the respective blocks of the backlight module section 2 and detects the feature values of the respective divided regions. The feature value detection section 3 sends the detected feature values to the medical image detection section 4 and the attribute determination section 5 on the following stage. In the first embodiment, the feature value detection section 3 detects, as the feature values of the respective divided regions, maximum values, average values, and bright area values of the gradation values (RGB values) of pixels constituting the divided regions. Here, the bright area values are values obtained by counting the number of pixels having a gradation value of a preset threshold (sixth threshold) or more among the pixels constituting the divided regions without RGB discrimination. In the first embodiment, the input image has gradation values of 0 to 4095, and pixels having a gradation value of 60 or more are counted as bright pixels. That is, the sixth threshold is set at 60. A specific description will be given using
Based on the two feature values (the maximum values and the average values) detected by the feature value detection section 3, the medical image detection section 4 determines whether the input image is a first image including the predetermined object image or a second image not including the predetermined object image. The first image is a medical image taken by an X-ray. The second image is an image of an operating system (OS) output from, for example, a personal computer (PC). The medical image detection section 4 determines whether the respective divided regions are flat regions or dark flat regions. The flat regions are regions including only pixels in which a type of gradation values are a first threshold or less (for example, 2 or less) and that have intermediate gradation. The dark flat regions are regions including only pixels in which a type of gradation values is a fourth threshold or less (for example, 2 or less) and that have dark gradation. The pixels having the dark gradation are pixels in which a size of gradation values is a third threshold or less (for example, 64 or less). The medical image detection section 4 counts the determination results of the respective divided regions. The medical image detection section 4 compares the number of the divided regions determined to be the flat regions with a second threshold (CNth) and compares the number of the divided regions determined to be the dark flat regions with a fifth threshold (BCNth). The medical image detection section 4 determines that the input image is the second image (the image of the OS) when at least any of the condition under which the number of the divided regions determined to be the flat regions is the second threshold or more and the condition under which the number of the divided regions determined to be the dark flat regions is the fifth threshold or more is satisfied. Since the input image is not a multi-gradation image when any of these conditions is satisfied, the medical image detection section 4 determines that the input image is not the first image (the medical image). Hereinafter, the determination method will be described in detail.
In general, a medical image (the first image) including an image of an object taken by an X-ray or the like is constituted by multi-gradation (three or more gradation levels), and thus the number of types of gradation values is not reduced to 1 or 2. On the other hand, in an image of an OS shown in
The dark flat region determination section 31 determines whether the respective divided regions are the dark flat regions from the maximum values and the average values of the gradation values of the respective divided regions sent from the feature value detection section 3. When the maximum values of the gradation values of the pixels in the divided regions indicate dark gradation and the differences between the maximum values and the average values are small, it is assumed that the image of the divided regions is not a multi-gradation image and the gradation values of the pixels in the divided regions are nearly uniform. Therefore, the dark flat region determination section 31 determines that the divided regions satisfying the following formulae 1 and 2 at the same time are the dark flat regions.
|Maximum value−Average value|≤dL1 (Formula 1)
Pa1≤Average value≤Pa2 (Formula 2)
Here, dL1 (fourth threshold) and Pa1 and Pa2 (third thresholds) indicate preset values. In the first embodiment, it is assumed that dL1 is set at 2, Pa1 is set at 0, and Pa2 is set at 64. The dark gradation is stipulated by Pa1 and Pa2. In the first embodiment, it is stipulated that the dark gradation is up to 64. In addition, dL1 indicates the thresholds of the sizes of the differences between the maximum values and the average values used to determine the dark flat regions. When the divided regions are constituted by the pixels of one gradation value, the sizes of the differences between the maximum values and the average values are 0. However, when noise is caused in the image, the maximum values and the average values are not equal to each other. The fourth threshold dL1 is set at 2 such that the divided regions having nearly uniform gradation values may be determined to be the dark flat regions even if small noise is caused. For example, in the case of the input image of
|Maximum value−Average value|=|0−0|≤dL1
Pa1≤0≤Pa2
Therefore, since both formulae 1 and 2 are satisfied, the dark flat region determination section 31 determines that the divided region is the dark flat region. On the other hand, the divided region at the coordinates (1,1) has a maximum value of 1536 and an average value of 1536 and establishes the following relationships.
|Maximum value−Average value|=|1536−1536|≤dL1
Pa1≤1536≤Pa2
Therefore, since formula 2 is not satisfied while formula 1 is satisfied, the dark flat region determination section 31 does not determine that the divided region is the dark flat region.
In the way described above, the dark flat region determination section 31 determines whether the respective divided regions are the dark flat regions. Then, the dark flat region determination section 31 sets the dark flat region flags of the divided regions determined to be the dark flat regions at 1 and sends the flags to the dark flat region count section 33 on the following stage. While, the dark flat region determination section 31 sets the dark flat region flags of the divided regions not determined to be the dark flat regions at 0 and sends the flags to the dark flat region count section 33 on the following stage.
The flat region determination section 32 determines whether the respective divided regions are the intermediate gradation flat regions from the maximum values and the average values of the gradation values of the respective divided regions sent from the feature value detection section 3. The flat region determination section 32 determines that the divided regions satisfying the following formulae 3 and 4 at the same time are the flat regions.
|Maximum value−Average value|dL2 (Formula 3)
Pa3≤Average value≤Pa4 (Formula 4)
(here, Pa1<Pa2<Pa3<Pa4)
dL2 (first threshold), Pa3, and Pa4 indicate preset thresholds. In the first embodiment, it is assumed that dL2 is set at 2, Pa3 is set at 65, and Pa4 is set at 1600. The intermediate gradation is stipulated by Pa3 and Pa4. In the first embodiment, it is stipulated that the gradation of 65 or more is the intermediate gradation. In addition, dL2 indicates the thresholds of the sizes of the differences between the maximum values and the average values used to determine the flat regions. In the first embodiment, it is assumed that the first threshold dL2 is set at 2 as in the case of the dark flat regions. Like the dark flat region determination section 31, the flat region determination section 32 determines whether the respective divided regions are the intermediate gradation flat regions. Then, the flat region determination section 32 sets the flat region flags of the divided regions determined to be the flat regions at 1 and sends the flags to the flat region count section 34 on the following stage. While, the flat region determination section 32 sets the flat region flags of the divided regions not determined to be the flat regions at 0 and sends the flags to the flat region count section 34 on the following stage. Note that although the thresholds Pa3 and Pa4 are set at 65 and 1600, respectively, in the embodiment, they may be set at any value. For example, the thresholds may be changed according to modality settings adjusted by an interpretation operator. In the above example, the intermediate gradation flat regions are determined by setting Pa4 at 1600. However, the flat regions of the intermediate-gradation to high gradation may be determined by setting Pa4, for example, at 4095.
The dark flat region count section 33 receives the dark flat region flags of the respective divided regions from the dark flat region determination section 31. When the dark flat region flags are set at 1, the dark flat region count section 33 increments a dark flat region count value by 1. When the dark flat region flags are set at 0, the dark flat region count section 33 does not change the dark flat region count value. In the case of the image of
The flat region count section 34 receives the flat region flags of the respective divided regions from the flat region determination section 32. When the flat region flags are set at 1, the flat region count section 34 increments a flat region count value by 1. When the flat region flags are set at 0, the flat region count section 34 does not change the flat region count value. In the case of the image of
The medical image determination section 35 determines whether the input image is the medical image based on the dark flat region count value and the flat region count value. The medical image determination section 35 determines that the input image is not a multi-gradation image, i.e., it is not the medical image (but is the second image) when at least any of conditions shown in the following formulae 5 and 6 is satisfied. On the other hand, the medical image determination section 35 determines that the input image is the multi-gradation image and is the medical image (it is the first image) when both the conditions shown in the following formulae 5 and 6 are not satisfied.
Dark flat region count value≥BCNth (Formula 5)
Flat region count value≥CNth (Formula 6)
For example, when it is assumed in the first embodiment that BCNth is set at 60 and CNth is set at 30, the dark flat region count value becomes 46 and the flat region count value becomes 10 in the case of the image of
The attribute determination section 5 performs attribute determination as to whether the respective divided regions are object regions in which an image of an object (object to be interpreted) exists or background regions including the background of the predetermined object image. Hereinafter, the attribute determination will be described in detail.
The attribute determination section 5 compares the bright area values of the respective divided regions acquired by the feature value detection section 3 with a preset threshold (seventh threshold) to determine the attributes of the respective divided regions. The attribute determination section 5 determines that the divided regions whose bright area value is larger than the seventh threshold are the object regions and determines that the divided regions whose bright area value is the seventh threshold or less are the background regions. The attribute determination section 5 sends results thus determined to the control section 6 on the following stage. Hereinafter, a specific operation example of the attribute determination section 5 will be described using the images of
Since the medical image flag of the image of
When it is determined by the medical image detection section 4 that the input image is the medical image (the first image), i.e., when the medical image flag sent from the medical image detection section 4 is set at 1, the control section 6 outputs the results of the attribute determination section 5 to the backlight brightness value determination section 7 on the following stage as they are. In addition, when the medical image flag is set at 0, i.e., when it is determined that the input image is not the medical image (it is the second image), the control section 6 performs processing to invalidate local dimming. In order to invalidate the local dimming, the control section 6 handles the attributes of all the divided regions as the object regions regardless of the determination results of the attribute determination section 5. That is, the control section 6 sets the attribute determination results of all the divided regions at 1 and outputs the same to the backlight brightness value determination section 7 on the following stage. The local dimming is invalidated by the processing since the backlight brightness value determination section 7 determines to apply the local dimming according to whether the attribute determination results indicate the background regions or the object regions as will be described later. Specifically, the backlight brightness value determination section 7 applies the local dimming to the light sources corresponding to the divided regions indicating the background regions and does not apply the local dimming to the light sources corresponding to the divided regions indicating the object regions. The second image other than the medical image, for example, an image of an OS or an image other than the medical image is an image that requires gradation expression in dark parts or an image that requires reduction in halo. When the input image is the second image, the local dimming is not applied (the brightness of the light sources is made uniform) regardless of the attribute determination results. Therefore, the brightness of the light sources of the backlight does not reduce in the dark parts that require gradation expression or the text region of a dark background. Accordingly, the gradation expression is allowed in the dark parts, and interference due to halo is restrained. Note that the above embodiment describes the example in which the attribute determination results of the respective divided regions are corrected to control the application of the local dimming when the input image is not the medical image. As another method, it may be possible for the control section 6 to directly instruct the backlight brightness value determination section 7 on the following stage to light the light sources corresponding to all the divided regions with constant brightness (brightness of a case in which the local dimming is not applied) when it is determined that the input image is not the medical image.
The backlight brightness value determination section 7 receives the attribute determination results of the respective divided regions from the control section 6 and determines the brightness of the light sources corresponding to the respective divided regions. The backlight brightness value determination section 7 sets the brightness of the light sources corresponding to the divided regions determined to be the object regions at the same brightness as that of the case in which the local dimming is not applied. In addition, the backlight brightness value determination section 7 sets the brightness of the light sources corresponding to the divided regions determined to be the background regions at brightness lower than that of the case in which the local dimming is not applied. For example, when reducing brightness in black of the background regions to 1/10, the backlight brightness value determination section 7 reduces the brightness of the light sources corresponding to the background regions to 1/10 the brightness. Accordingly, the backlight darkens in the dark background of the medical image of
With the above configuration, the display apparatus of the first embodiment determines whether the input image is the medical image and determines the brightness of the respective light sources of the backlight based on the determination results and the feature values of the image. Thus, in a case in which the input image is the medical image, the light sources of the backlight of the dark background regions are darkened by the local dimming to reduce black floating and the feelings of interference due to the black floating when an interpretation operator or the like performs interpretation. In a case in which the input image is not the medical image, the brightness of the light sources of the backlight does not reduce even in the dark regions. Therefore, halo is restrained, and the gradation of the dark regions may be expressed.
The above first embodiment describes the example in which determination is made as to whether the respective divided regions are the dark flat regions or the intermediate gradation flat regions based on the maximum values and the average values of the gradation values of the respective divided regions to determine whether the input image is the medical image. As another method, it may be possible for the feature value detection section 3 to acquire the histograms of the gradation values of the respective divided regions and determine whether the respective divided regions are the dark flat regions or the intermediate gradation flat regions from the distribution of the frequencies of the histograms. According to the method, the determination may be made with higher precision. Here, the distribution of the frequencies of the histograms will be described using
The above first embodiment describes the example in which determination is made as to whether the whole input image is the first image (the medical image) including the predetermined object image or is the second image (the image of the OS or the image other than the medical image) not including the image of the object. However, there is a likelihood that the display regions of the first and second images are mixed together in the input image. For example, there is a likelihood that the display region of the medical image is arranged on the left half side of a screen and the text display region is arranged on the right half side of the screen. In such a case, it may be possible to apply the local dimming, which reduces the brightness of the backlight in the dark background regions, to the display region of the medical image, and may not reduce the brightness of the backlight even in the dark background regions in the text display region.
The above first embodiment describes the example in which the medical image detection section 4 determines whether the input image is the medical image (the first image) or the image (the second image) other than the medical image based on the feature values of the input image. However, any method for determining the input image may be employed. For example, it may be possible to determine whether the input image is the medical image based on metadata included in image data.
Embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2014-240503, filed on Nov. 27, 2014, and Japanese Patent Application No. 2015-217743, filed on Nov. 5, 2015, which are hereby incorporated by reference herein in their entirety.
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