JP2015022123A - Display device, control method of display device, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique capable of adjusting brightness of a display image while suppressing an increase in a black floating amount.SOLUTION: A display device includes: light emission means having a plurality of light sources capable of controlling a light emission luminance individually; display means for displaying an image on a screen by modulating light from the light emission means on the basis of inputted image data; image processing means which performs luminance adjustment processing for adjusting a luminance for the image data, and outputs the image data after performing the luminance adjustment processing on the display means; acquisition means which acquires a feature quantity representing a luminance of image data in an area from the image data closer to the image data before performing the luminance adjustment processing than the image data after performing the luminance adjustment processing for each of a plurality of areas on the screen corresponding to the plurality of light sources; and control means for controlling the light emission luminance of each light source on the basis of the feature quantity acquired by the acquisition means.

Description

  The present invention relates to a display device, a display device control method, and a program.

  Conventionally, in a liquid crystal display device, a technique is known in which a backlight having a plurality of light sources is used and the light emission luminance of each light source is individually controlled in accordance with a feature amount representing the luminance of image data. In such a technique, for example, the light emission luminance of the light source corresponding to the dark image region (dark portion image region) is controlled to a low value, and the light emission luminance of the light source corresponding to the bright image region (bright portion image region) is high. Controlled by value. Accordingly, it is possible to improve the visibility of the dark image area by reducing the amount of black floating in the dark image area, and to increase the contrast of the display image (image displayed on the screen). Such a technique is disclosed in Patent Document 1, for example.

  On the other hand, a technique for adjusting the visibility (brightness) of a display image according to a user operation is known. In such a technique, for example, all pixel values (pixel data) are multiplied by a gain value (a gain value common to the pixels) designated by the user. Thereby, the brightness of the display image can be adjusted to the brightness desired by the user. Such a technique is disclosed in Patent Document 2, for example.

In the liquid crystal display device, it is required to reduce the black floating amount of the display image and increase the contrast of the display image by controlling the light emission luminance of each light source according to the feature amount of the image data. Further, in the liquid crystal display device, it is required to adjust the brightness of the display image to the brightness desired by the user by performing image processing (image processing for increasing luminance) on the image data in accordance with a user operation.
However, if both are desired, the following problems will occur.
When the pixel value is increased by multiplying the pixel value by the gain value specified by the user, the feature amount changes as the pixel value increases, and the emission luminance of each light source is increased as the feature amount changes. End up. As a result, the amount of black floating in the dark area image area increases, and the visibility of the dark area image area decreases. That is, in the prior art, even though the user has adjusted the gain value with the intention of improving the visibility of the dark image area, the light emission luminance of each light source is increased by the adjustment, and the black floating amount increases. Therefore, the effect of improving the visibility of the intended dark part image area cannot be obtained.

JP 2002-99250 A JP 2008-158372 A

  An object of the present invention is to provide a technique capable of adjusting the brightness of a display image while suppressing an increase in the amount of black floating.

The first aspect of the present invention is:
A light emitting means having a plurality of light sources capable of individually controlling the light emission brightness;
Display means for displaying an image on a screen by modulating light from the light emitting means based on input image data;
Image processing means for performing brightness adjustment processing for adjusting brightness on the image data, and outputting the image data after the brightness adjustment processing to the display means;
For each of a plurality of areas on the screen corresponding to the plurality of light sources, from image data close to the image data before being subjected to the luminance adjustment processing compared to image data after being subjected to the luminance adjustment processing, Acquisition means for acquiring a feature amount representing the luminance of the image data in the region;
Control means for controlling the light emission luminance of each light source based on the feature amount obtained by the obtaining means;
It is a display device characterized by having.

The second aspect of the present invention is:
A light emitting means having a plurality of light sources capable of individually controlling the light emission brightness;
Display means for displaying an image on a screen by modulating light from the light emitting means based on input image data;
A display device control method comprising:
An image processing step of performing luminance adjustment processing for adjusting luminance on the image data, and outputting the image data after the luminance adjustment processing to the display unit;
For each of a plurality of areas on the screen corresponding to the plurality of light sources, from image data close to the image data before being subjected to the luminance adjustment processing compared to image data after being subjected to the luminance adjustment processing, An obtaining step for obtaining a feature amount representing luminance of image data in the region;
A control step of controlling the light emission luminance of each light source based on the feature amount acquired in the acquisition step;
A control method for a display device, comprising:

  According to a third aspect of the present invention, there is provided a program that causes a computer to execute each step of the display device control method described above.

  According to the present invention, it is possible to adjust the brightness of a display image while suppressing an increase in the amount of black float.

1 is a block diagram showing an example of a functional configuration of a liquid crystal display device according to Embodiment 1. FIG. 7 is a flowchart illustrating an example of a processing flow of the liquid crystal display device according to the first embodiment. FIG. 6 is a diagram illustrating an example of a display image before luminance adjustment processing of the liquid crystal display device according to the first embodiment. FIG. 6 is a diagram illustrating an example of a display image after the brightness adjustment process of the liquid crystal display device according to the first embodiment. FIG. 9 is a block diagram illustrating an example of a functional configuration of a liquid crystal display device according to a third embodiment. FIG. 9 is a block diagram illustrating an example of a functional configuration of a liquid crystal display device according to a fourth embodiment. The figure which shows an example of the display image of the conventional liquid crystal display device

<Example 1>
Hereinafter, a display device and a control method thereof according to Embodiment 1 of the present invention will be described.
In this embodiment, an example in which the display device is a transmissive liquid crystal display device will be described. However, the display device is not limited to a transmissive liquid crystal display device. The display device may be a display device having an independent light source. For example, the display device may be a reflective liquid crystal display device. Further, the display device may be a MEMS shutter system display using a MEMS (Micro Electro Mechanical System) shutter instead of the liquid crystal element.

(overall structure)
FIG. 1 is a block diagram illustrating an example of a functional configuration of the liquid crystal display device according to the present embodiment. As shown in FIG. 1, the liquid crystal display device according to this embodiment includes a mode switching unit 101, an image processing unit 111, a feature amount acquisition unit 103, a target luminance determination unit 104, a backlight control value determination unit 109, and a liquid crystal panel 108. , A backlight 110, and the like.

  The backlight 110 is a light emitting unit having a plurality of light sources capable of individually controlling light emission luminance. The light source has one or more light emitting members. As the light emitting member, for example, an LED, an organic EL element, a cold cathode tube, or the like can be used. Light from the backlight 110 is applied to the back surface of the liquid crystal panel 108.

  The liquid crystal panel 108 is a display panel that displays an image on a screen by modulating light from the backlight 110 based on image data input to the liquid crystal panel 108. Specifically, the liquid crystal panel 108 includes a plurality of liquid crystal elements, and controls the transmittance of each liquid crystal element based on image data input to the liquid crystal panel 108. Then, the light from the backlight 110 passes through each liquid crystal element, whereby an image is displayed on the screen.

The mode switching unit 101 sets an operation mode instructed by the user, and sets a gain value (user instructed gain value) instructed by the user.
Then, the mode switching unit 101 outputs the set user instruction gain value to the image processing unit 111 according to the set operation mode. Specifically, the mode switching unit 101 outputs the set user instruction gain value to the second gain multiplication unit 102 or the gain mixing unit 106 described later according to the set operation mode. In the present embodiment, it is assumed that the liquid crystal display device is a device capable of setting the first mode or the second mode as the operation mode. When the first mode is set, the mode switching unit 101 outputs the user instruction gain value to the gain mixing unit 106 and outputs the gain value 1 to the second gain multiplication unit 102. When the second mode is set, the mode switching unit 101 outputs the user instruction gain value to the second gain multiplication unit 102 and outputs the gain value 1 to the gain mixing unit 106. Hereinafter, the gain value that the mode switching unit 101 outputs to the second gain multiplication unit 102 is described as Gf, and the gain value that the mode switching unit 101 outputs to the gain mixing unit 106 is described as Gb.

Note that the first mode is an operation mode in which the contrast of the display image (image displayed on the screen) is increased and the brightness of the display image is adjusted while suppressing an increase in the amount of black float. The second mode is an operation mode in which the contrast of a display image is increased without breaking the balance of gradation values (pixel values) between pixels.
In this embodiment, the user instruction gain value and the operation mode are set according to the user operation. However, the present invention is not limited to this. For example, the user instruction gain value and the operation mode may be automatically set according to the type and brightness of the input image data.
Note that the liquid crystal display device may have an operation mode other than the first mode and the second mode.

  The image processing unit 111 performs, on the image data, a brightness adjustment process for adjusting the brightness of the image data and a compensation process for compensating for a change in brightness on the screen due to a change in the light emission brightness of the light source of the backlight 110. Then, the image processing unit 111 outputs the image data after the brightness adjustment process and the compensation process are performed to the liquid crystal panel 108.

In the present embodiment, as the luminance adjustment processing, processing for adjusting the luminance of the image data with the set user instruction gain value (gradation value increase rate) is performed. Specifically, in this embodiment, the luminance of the image data is adjusted by multiplying the user-indicated gain value by the gradation value of each pixel of the image data.

  In the present embodiment, as the compensation process, a process of adjusting the brightness of the image data with the brightness compensation gain value determined by the brightness compensation gain determination unit 105 described later is performed.

  As shown in FIG. 1, the image processing unit 111 includes a first gain multiplication unit 107, a second gain multiplication unit 102, a luminance compensation gain determination unit 105, a gain mixing unit 106, and the like.

  In this embodiment, an example in which the brightness adjustment process and the compensation process are performed on the image data (input image data) input to the liquid crystal display device will be described. However, the present invention is not limited to this. Predetermined image processing may be performed on the input image data, and brightness adjustment processing and compensation processing may be performed on the image data after the predetermined image processing is performed. The predetermined image processing is, for example, blurring processing, edge enhancement processing, color conversion processing, and the like.

The second gain multiplication unit 102 multiplies the gradation value of each pixel of the input image data by the gain value Gf input from the mode switching unit 101, and the image data after the gain value Gf is multiplied by the first gain data Gf. The result is output to the gain multiplication unit 107 and the feature amount acquisition unit 103.
As described above, when the first mode is set, the mode switching unit 101 sends the gain value 1 instead of the user-indicated gain value to the second gain multiplication unit 102. Therefore, when the first mode is set, the second gain multiplication unit 102 converts the input image data (image data before the luminance adjustment processing) into the first gain multiplication unit 107 and the feature amount. The data is output to the acquisition unit 103.
When the second mode is set, the user instruction gain value is sent from the mode switching unit 101 to the second gain multiplication unit 102. Therefore, when the second mode is set, the second gain multiplication unit 102 performs a luminance adjustment process on the input image data using the user-indicated gain value. Then, the second gain multiplication unit 102 outputs the image data after the luminance adjustment processing to the first gain multiplication unit 107 and the feature amount acquisition unit 103.

For each of a plurality of regions corresponding to a plurality of light sources included in the backlight 110, the feature amount acquisition unit 103 calculates a feature amount representing the luminance of the image data in the region from the image data input to the feature amount acquisition unit 103. get. Then, the feature amount acquisition unit 103 outputs the acquired feature amount to the target luminance determination unit 104. The feature amount is, for example, a representative value (maximum value, minimum value, mode value, intermediate value, average value, etc.) of pixel values, a histogram, a representative value or histogram of luminance values, or the like.
As described above, when the first mode is set, the input image data is input to the feature amount acquisition unit 103. Therefore, when the first mode is set, the feature amount is acquired from the input image data.
When the second mode is set, the image data after the brightness adjustment process is input to the feature amount acquisition unit 103. Therefore, when the second mode is set, the feature amount is acquired from the image data after the luminance adjustment process is performed.

In this embodiment, it is assumed that a plurality of divided areas constituting a screen area are set as a plurality of areas corresponding to a plurality of light sources. However, the area corresponding to the light source is not limited to this. For example, as an area corresponding to a light source, an area overlapping with an area corresponding to another light source may be set, or an area not in contact with an area corresponding to another light source may be set.
In this embodiment, a plurality of different divided areas are set as a plurality of areas corresponding to a plurality of light sources, but the present invention is not limited to this. For example, the same area as that corresponding to another light source may be set as the area corresponding to the light source.

A feature amount acquisition unit 103 is configured by the target luminance determination unit 104 and the backlight control value determination unit 109.
Based on the feature amount acquired in step S1, the light emission luminance of each light source included in the backlight 110 is controlled.
As described above, when the first mode is set, the feature amount is acquired from the input image data. Therefore, when the first mode is set, the light emission luminance is controlled based on the feature amount acquired from the input image data.
Further, when the second mode is set, the feature amount is acquired from the image data after the luminance adjustment process is performed. Therefore, when the second mode is set, the light emission luminance is controlled based on the feature amount acquired from the image data after the luminance adjustment processing is performed.

For each divided region, the target luminance determining unit 104 determines the target luminance of the light source corresponding to the region based on the feature amount acquired for the divided region. The target brightness is determined using, for example, a function or table that represents the correspondence between the feature quantity and the target brightness. In this embodiment, the target luminance is determined so that the target luminance is lower in the dark image region (dark portion image region) than in the bright image region (bright portion image region). Then, the target luminance determination unit 104 outputs the target luminance for each divided region (for each light source) to the luminance compensation gain determination unit 105, the gain mixing unit 106, and the backlight control value determination unit 109.
The method for determining the target brightness is not limited to the above method. For example, the target luminance of the light source may be determined using the feature amount of the divided region corresponding to the light source and the feature amount of the divided region corresponding to the light sources around the light source.

The backlight control value determination unit 109 controls the light emission luminance of each light source included in the backlight 110 to the target luminance. Specifically, the backlight control value determination unit 109 determines the backlight control value of the light source based on the target luminance of the light source for each light source. The backlight control value is determined using, for example, a function or table that represents the correspondence between the target luminance and the backlight control value. When the light emission luminance of the light source is controlled by controlling the supply time (pulse width) of the voltage (or current) supplied to the light source, a value representing the pulse width is determined as the backlight control value. When the light emission luminance of the light source is controlled by controlling the voltage (or current) value (pulse amplitude) supplied to the light source, a value representing the pulse amplitude is determined as the backlight control value. When the light emission luminance is controlled by controlling both the pulse width and the pulse amplitude, a value indicating both the pulse width and the pulse amplitude is determined as the backlight control value.
Then, the backlight control value determination unit 109 outputs the backlight control value of each light source to the backlight 110. In the backlight 110, each light source emits light with a light emission luminance corresponding to the backlight control value.

The luminance compensation gain determination unit 105 determines the luminance distribution of the light from the backlight 110 (the luminance for each pixel position) when the emission luminance of each light source is controlled to the target luminance based on the target luminance for each divided region (for each light source). ). The luminance distribution is estimated in consideration of attenuation of light from the light source, for example. Further, when light from the light source leaks to other divided regions, the luminance distribution is estimated in consideration of such light leakage.
Then, the luminance compensation gain determining unit 105 determines, for each pixel, a value obtained by dividing a predetermined reference value by the luminance estimated with respect to the position of the pixel as the luminance compensation gain value of the pixel. Accordingly, a gain value that compensates for a change in luminance on the screen due to a change in light emission luminance of the light source can be obtained as the luminance compensation gain value. Note that the luminance compensation gain value may be calculated using a function that represents the correspondence relationship between the estimated luminance and the luminance compensation gain value, or may be determined using a table that represents such a correspondence relationship.
The luminance compensation gain determination unit 105 outputs the luminance compensation gain value for each pixel to the gain mixing unit 106.
In this embodiment, the luminance compensation gain value is determined for each pixel. However, the present invention is not limited to this. For example, for each divided area, a common luminance compensation gain value may be determined for each pixel in the divided area using the target luminance of the divided area. Specifically, for each divided region, a value obtained by dividing the reference value by the target luminance of the divided region may be calculated as a luminance compensation gain value for each pixel in the divided region.

The gain mixing unit 106 calculates, for each pixel, a mixed gain value obtained by mixing the gain value Gb input from the mode switching unit 101 and the luminance compensation gain value input from the luminance compensation gain determining unit 105. Specifically, the mixed gain value is calculated by multiplying the gain value Gb by the luminance compensation gain value.
As described above, when the first mode is set, the user instruction gain value is sent from the mode switching unit 101 to the gain mixing unit 106. Therefore, when the first mode is set, a gain value for performing both the luminance adjustment process and the compensation process is calculated as the mixed gain value.
Further, when the second mode is set, the mode switching unit 101 sends a gain value 1 to the gain mixing unit 106 instead of the user-designated gain value. Therefore, when the second mode is set, a gain value (brightness compensation gain value) to which compensation processing is performed is calculated as the mixed gain value.

The first gain multiplication unit 107 multiplies the image data input from the second gain multiplication unit 102 by the mixed gain value input from the gain mixing unit 106, and the image data obtained by multiplying the mixed gain value by liquid crystal Output to panel 108. The image data after being multiplied by the mixed gain value is image data that has been subjected to both luminance adjustment processing and compensation processing.
As described above, when the first mode is set, the gain mixing unit 106 sends a mixed gain value for performing both luminance adjustment processing and compensation processing, and the second gain multiplication unit 102 inputs the input image data. Will be sent. Therefore, when the first mode is set, the first gain multiplication unit 107 performs both luminance adjustment processing and compensation processing on the input image data.
Further, when the second mode is set, the mixed gain value to which compensation processing is performed is sent from the gain mixing unit 106, and the image data after the luminance adjustment processing is performed from the second gain multiplication unit 102 Sent. Therefore, when the second mode is set, the first gain multiplication unit 107 performs compensation processing on the image data that has been subjected to the luminance adjustment processing.

  In the gain mixing unit 106, a user-instructed gain is set for each tone value that the image data can take so that the tone value does not exceed the upper limit value (the tone upper limit value) even if the tone value is multiplied by the tone value. An upper limit value (user instruction gain upper limit value) is determined. The gain mixing unit 106 uses the acquired user instruction gain value for pixels whose user instruction gain value does not exceed the user instruction gain upper limit value. In addition, for a pixel whose user instruction gain value exceeds the user instruction gain upper limit value, the user instruction gain upper limit value is used as the user instruction gain value. For pixels whose user instruction gain value exceeds the user instruction gain upper limit value, a value smaller than the user instruction gain upper limit value may be used as the user instruction gain value.

A method for determining the user-designated gain upper limit value corresponding to the gradation value is shown below.
The gradation value is usually expressed by digital data having a finite bit length. For this reason, the gradation value has an upper limit value (gradation upper limit value). A value obtained by dividing the gradation upper limit value by a certain gradation value is an upper limit value (gain upper limit value) of a gain value that can be multiplied by the gradation value. The gain upper limit value is determined for each gradation value. Then, if the gradation value is multiplied by a gain value that exceeds the gain upper limit value, the gradation value is saturated and gradation collapse occurs. For example, when the light emission luminance of each light source is individually controlled and compensation processing is performed, the gradation value is more likely to be saturated because the amount of increase in the gradation value by the compensation processing increases as the light emission luminance decreases. Therefore, when a large user instruction gain is set, the gradation value is saturated in order from the pixel in the divided region corresponding to the light source with the low emission luminance, even though the gradation value is the same pixel in the input image data. Display luminance (brightness on the screen) is shifted between the two. Since the user is not conscious of the luminance distribution of the light from the backlight 110, such a shift in display luminance gives the user a sense of incongruity. For example, such a display luminance shift is recognized by the user as a deterioration in image quality.

In the second mode, the mixed gain value is calculated by multiplying the user-indicated gain value by the luminance compensation gain value. The first gain multiplication unit 107 multiplies the input image data by the mixed gain value. Therefore, in order not to saturate the gradation value, the mixed gain value needs to be equal to or less than the gain upper limit value.
Therefore, in this embodiment, for each pixel of the input image data, a gain upper limit value and a provisional luminance compensation gain value (provisional compensation gain value) are calculated from the gradation value of that pixel. The calculation method of the gain upper limit value is as described above. The provisional compensation gain value is determined using, for example, a function or table that represents the correspondence between the gradation value and the provisional compensation gain value. When the feature value is a representative value of the gradation value, the provisional compensation gain value is the correspondence information used by the target luminance determination unit 104 and the correspondence information used by the luminance compensation gain determination unit 105. And may be determined using The correspondence information used in the target luminance determination unit 104 is information representing the correspondence between the feature amount and the target luminance, and the correspondence information used in the luminance compensation gain determination unit 105 is the estimated luminance and the luminance compensation gain value. It is the information showing the correspondence relationship.
The user-designated gain value needs to be equal to or less than a value obtained by dividing the gain upper limit value by the luminance compensation gain value.
Therefore, in this embodiment, for each pixel of the input image data, a value obtained by dividing the gain upper limit value of the pixel by the provisional compensation gain value of the pixel is calculated as the user-designated gain upper limit value of the pixel.

(Processing flow)
An example of the processing flow of the liquid crystal display device according to the present embodiment will be described with reference to the flowchart shown in FIG.
First, in S01, the mode switching unit 101 acquires a mode setting value M and a brightness adjustment value L specified by the user.
Next, in S02, the mode switching unit 101 determines a multiplication value Gu (user instruction gain value) to be multiplied by the pixel data according to the brightness adjustment value L acquired in S01. The user instruction gain value Gu is determined using, for example, a function or table that represents the correspondence between the adjustment value L and the user instruction gain value Gu.
In step S03, the mode switching unit 101 determines whether the mode setting value M acquired in step S01 is a value indicating the first mode or a value indicating the second mode. If the mode setting value M is a value representing the first mode, the process proceeds to S04. If the mode setting value M is a value representing the second mode, the process proceeds to S05.
In S04, the mode switching unit 101 outputs 1 as the gain value Gf to the second gain multiplication unit 102, and outputs the user instruction gain value Gu calculated in S02 as the gain value Gb to the gain mixing unit 106.
In S05, the mode switching unit 101 outputs the user instruction gain value Gu determined in S02 as the gain value Gf to the second gain multiplication unit 102, and outputs 1 as the gain value Gb to the gain mixing unit 106.

Next, in S06, the second gain multiplication unit 102 multiplies the tone value of each pixel of the input image data by the gain value Gf acquired from the mode switching unit 101, and the image data after the gain value Gf is multiplied. Is output.
In S07, the feature amount acquisition unit 103 acquires the feature amount for each divided region from the image data after being multiplied by the gain value Gf, and outputs the feature amount for each divided region. Then, the target luminance determining unit 104 determines the target luminance for each divided region (for each light source) based on the feature amount for each divided region. Thereafter, the backlight control value determination unit 109 controls the light emission luminance of each light source to the target luminance.

Next, in S08, the luminance compensation gain determination unit 105 determines the luminance distribution of light from the backlight 110 (for each pixel position) when the emission luminance of each light source is controlled to the target luminance based on the target luminance for each divided region. Is estimated.
In S09, the luminance compensation gain determination unit 105 divides the predetermined reference value S by the luminance R estimated with respect to the position of the pixel for each pixel, thereby obtaining the luminance compensation gain value Gs for each pixel. calculate. The luminance compensation gain determination unit 105 outputs the luminance compensation gain value Gs for each pixel to the gain mixing unit 106.
Next, in S10, the gain mixing unit 106 mixes the luminance compensation gain value Gs acquired from the luminance compensation gain determining unit 105 and the gain value Gb acquired from the mode switching unit 101 for each pixel, thereby obtaining a pixel. The mixing gain value Gp for each is calculated. The gain mixing unit 106 outputs the mixed gain value Gp for each pixel to the first gain multiplication unit 107.
In step S11, the first gain multiplication unit 107 multiplies the image data obtained from the second gain multiplication unit 102 by the mixed gain value Gp for each pixel obtained from the gain mixing unit 106, and multiplies the mixed gain value. Thereafter, the image data is output to the liquid crystal panel 108. Thereafter, the transmittance of the liquid crystal panel 108 is controlled in accordance with the image data after being multiplied by the mixing gain value.

  Note that the timing for controlling the light emission luminance is preferably controlled so as to match the timing for controlling the transmittance of the liquid crystal panel 108.

(effect)
An example of the display image of the display device according to the present embodiment is shown on the left side of FIG. 3, and the display luminance distribution in the arrow portion shown in the display image is shown on the right side of FIG. FIG. 3 shows an example in which an object of interest brighter than a black background exists in a black background with a gradation value of 0. Since the target object is brighter than the black background, the light source corresponding to the divided area including the target object emits light with a higher emission luminance than the divided area including only the black background. As a result, the black floating amount is larger in the area around the target object in the black background area than in other areas. In FIG. 3, a circular area around the attention area is an area with a large black floating amount (black floating area). Such large black float deteriorates the visibility of the object of interest.

  Here, when a user operation is performed to increase the display brightness in order to improve the visibility of the object of interest, in the conventional display device that controls the light emission brightness of the backlight according to the image data, the light emission brightness is determined by the user operation. Will be raised. As a result, as shown in FIG. 7, the amount of floating black in the area around the object of interest increases, and the visibility further deteriorates. However, according to such a conventional method, the contrast of the display image can be increased without breaking the balance of the gradation values (pixel values) between the pixels. Therefore, in this embodiment, such processing is performed in the second mode.

On the other hand, according to the second mode of the present embodiment, the feature amount is acquired from the image data before being multiplied by the user instruction gain value. Therefore, even if the user instruction gain value fluctuates, the feature amount acquired by the feature amount acquisition unit 103 does not fluctuate, and the light emission luminance of each light source does not fluctuate. As a result, it is possible to adjust the brightness of the display image while suppressing an increase in the amount of black float. Specifically, as shown in FIG. 4, by increasing the user instruction gain value, it is possible to increase only the display brightness of the region of interest without changing the display brightness of the black background. Can be increased.
Further, in this embodiment, since the upper limit value of the user instruction gain value is set for each gradation value, the display luminance of pixels having the same gradation value in the input image data is prevented from varying due to saturation of the gradation value. Can do. In other words, pixels having the same gradation value in the input image data can be displayed with the same luminance.

In this embodiment, the example in which the display device has the first mode and the second mode has been described, but the present invention is not limited to this. For example, the display device may have only the first mode and always operate in the first mode.
In this embodiment, the example in which not only the brightness adjustment process but also the compensation process is performed has been described. However, the compensation process may not be performed. When the compensation process is not performed, the image processing unit 111 may perform the brightness adjustment process on the input image data and output the image data after the brightness adjustment process to the liquid crystal panel.
In the present embodiment, the example in which the feature amount is acquired from the image data before the luminance adjustment process is performed has been described, but the present invention is not limited to this. If the feature value is obtained from image data that is closer to the image data before the brightness adjustment process compared to the image data after the brightness adjustment process, the brightness of the displayed image is suppressed while suppressing an increase in the amount of black float Can be adjusted. However, as the image data for acquiring the feature amount is closer to the image data before the luminance adjustment process is performed, the increase in the amount of black float can be further suppressed.

  In this embodiment, the example in which the upper limit value of the user instruction gain value is set for each gradation value has been described. However, the present invention is not limited to this. For example, for a pixel whose user instruction gain exceeds the user instruction gain upper limit value, the gradation value may be forcibly saturated. Further, for a pixel whose user instruction gain exceeds the user instruction gain upper limit value, a predetermined gradation value may be output from the first gain multiplier 107. By performing such control, it is possible to suppress variation in display luminance of pixels having the same gradation value in the input image data due to saturation of the gradation value. Further, it is possible to clearly indicate that the user instruction gain value has reached the upper limit value, and the convenience for the user can be improved.

  In this embodiment, the example in which the provisional compensation gain value is calculated to calculate the user instruction gain upper limit value has been described. That is, the example in which the user instruction gain upper limit value is calculated assuming that the light source emits light with the light emission luminance corresponding to the gradation value for each gradation value has been described. However, the calculation method of the user instruction gain upper limit value is not limited to this. For example, the user instruction gain upper limit value may be calculated using the actually determined target luminance. Specifically, the user-designated gain upper limit value may be determined using the minimum target luminance value (minimum target luminance) for each divided area determined by the target luminance determining unit 104. By performing such control, the user instruction gain upper limit value can be increased as the minimum target luminance is smaller, and a brightness adjustment range as large as possible can be ensured.

<Example 2>
Hereinafter, a display device and a control method thereof according to Embodiment 2 of the present invention will be described.
Since the overall configuration of the display device according to the present embodiment is the same as that of the first embodiment, description thereof is omitted, and only functional units that operate differently from the first embodiment will be described below.

In this embodiment, the mode switching unit 101 sets a gain limit value K (threshold value) instructed by the user, and sets a user instruction gain value instructed by the user.
When the set user instruction gain value is equal to or less than the gain limit value K (threshold value or less), the mode switching unit 101 outputs the user instruction gain value to the second gain multiplication unit 102, and the gain mixing unit 106. A gain value of 1 is output. As a result, the feature amount is acquired from the image data after the luminance is adjusted with the user instruction gain value.
On the other hand, when the set user instruction gain value is larger than the gain limit value K, the mode switching unit 101 outputs the gain limit value K to the second gain multiplication unit 102 and the user mixing gain 106 to the gain mixing unit 106. A value obtained by dividing the value by the gain limit value K is output. As a result, the feature amount is acquired from the image data after the luminance is adjusted with a gain value (increase rate) equal to the gain limit value K.

If the above processing is performed, the feature amount is acquired from the image data closer to the input image data as the gain limit value K is closer to 1, so that the black level is less likely to change as the gain limit value K is closer to 1. can do. However, the closer the gain limit value K is to 1, the more easily the image data is saturated. When 1 is set as the gain limit value K, the same operation as in the first mode in the first embodiment can be performed, and the black level variation amount can be set to zero.
In addition, as the gain limit value K is larger, image data closer to the image data after the luminance adjustment processing is performed is acquired. Therefore, as the gain limit value K is larger, the black level is more likely to fluctuate. However, the larger the gain limit value K, the more difficult it is to saturate the image data. When the gain limit value K is set to a value equal to or greater than the user-designated gain value, the same operation as in the second mode in the first embodiment can be performed.
In this embodiment, since the user can adjust the gain limit value K, the balance between the stability of the black level and the degree of saturation of the image data can be arbitrarily adjusted, and the convenience for the user can be improved.
In this embodiment, the example in which the gain limit value K (threshold value) is set by the user has been described. However, the gain limit value K may be a fixed value set in advance.

<Example 3>
Hereinafter, a display device and a control method thereof according to Embodiment 3 of the present invention will be described.
(overall structure)
FIG. 5 is a block diagram illustrating an example of a functional configuration of the liquid crystal display device according to the present embodiment.
In addition, the same code | symbol as Example 1 is attached | subjected to the same function part as Example 1, and the description is abbreviate | omitted.
The functional units different from those in the first embodiment will be described below.

The dark image determination unit 212 determines whether or not the input image data (image data before being subjected to luminance adjustment processing) is dark image data (dark image data), and the determination result (dark image determination result) Is output to the mode switching unit 201. For example, the dark image determination unit 212 calculates an average gradation value (average pixel value) of the input image data, and compares the average gradation value with a predetermined threshold value. The dark image determination unit 212 determines that the input image data is dark image data when the average gradation value is equal to or less than a predetermined threshold value.
The method for determining whether or not the input image data is dark image data is not limited to the above method. For example, the input image data may be determined to be dark image data when the number of pixels having a gradation value equal to or smaller than a predetermined gradation value among the pixels of the input image data is equal to or greater than a predetermined number.

The image processing unit 211 has a configuration in which the mode switching unit 101 of the image processing unit 111 is replaced with a mode switching unit 201.
The mode switching unit 201 acquires a user instruction gain value instructed by the user and also acquires a dark image determination result. When it is determined that the input image data is dark image data, the user instruction gain value is output to the gain mixing unit 106 and the gain value 1 is output to the second gain multiplication unit 102. If it is determined that the input image data is not dark image data, the user-instructed gain value is output to the second gain multiplier 102 and the gain value 1 is output to the gain mixer 106.
As a result, when it is determined that the input image data is dark image data, the feature amount is acquired from the input image data (image data before the luminance adjustment process is performed). When it is determined that the input image data is not dark image data, the feature amount is acquired from the image data after the luminance adjustment processing is performed.

The lower the brightness of the input image data, the greater the amount of black float relative to the brightness of the input image data. Therefore, the degree of deterioration in the visibility of the display image due to black float increases and the image quality due to black float increases. Increases the sense of obstruction. On the other hand, the higher the brightness of the input image data, the smaller the amount of black float relative to the brightness of the input image data. The above disturbance is reduced.
As described above, in this embodiment, when it is determined that the input image data is dark image data, the feature amount is acquired from the input image data (image data before the luminance adjustment process). . Thereby, when the degree of deterioration of the visibility of the display image due to black floating is large, it is possible to adjust the brightness of the display image while suppressing an increase in the amount of black floating.
In this embodiment, when it is determined that the input image data is not dark image data, the feature amount is acquired from the image data after the brightness adjustment processing is performed. As a result, when the degree of deterioration in the visibility of the display image due to floating in the black is small, it is possible to increase the contrast of the display image without losing the balance of gradation values between pixels.

  In the present embodiment, an example in which a threshold value for determining whether or not the input image data is dark image data has been set in advance. However, such a threshold value is a value that can be adjusted by the user. May be. Thereby, the user can adjust the stability of the black level. For example, if the maximum value that can be taken by the image data is set as the threshold value, it is determined that the input image data is always dark part image data. Therefore, the display device is always in the first mode described in the first embodiment. It can be operated.

  Further, the idea of the present embodiment may be combined with the second embodiment. For example, the brightness of the input image data may be determined, and the gain limit value K may be changed according to the determined brightness so that the gain limit value K increases as the determined brightness decreases. The changed gain limit value K is determined using, for example, a function or table that represents the correspondence between the luminance of the input image data and the gain limit value K. Thereby, the gain limit value K in the second embodiment can be automatically set according to the luminance of the input image data.

<Example 4>
Hereinafter, a display device and a control method thereof according to Embodiment 4 of the present invention will be described.
In the present embodiment, the display device is a display device that can synthesize graphic image data with image data and display an image on which the graphic image is superimposed. The graphic image data is graphic image data such as an OSD image generated inside or outside the display device.

(overall structure)
FIG. 6 is a block diagram illustrating an example of a functional configuration of the liquid crystal display device according to the present embodiment.
In addition, the same code | symbol as Example 1 is attached | subjected to the same function part as Example 1, and the description is abbreviate | omitted.
The functional units different from those in the first embodiment will be described below.

  The image processing unit 311 has a configuration in which the gain mixing unit 106 of the image processing unit 111 is replaced with a gain mixing unit 306. The image processing unit 311 exchanges data with the graphic superimposing unit 312.

  The graphic image is not related to the input image data and may be used by the user to operate the display device. Therefore, it is preferable that the graphic image is displayed with a stable brightness independently of the image based on the input image data.

As one of the methods for performing such display, a method is conceivable in which the luminance adjustment process is performed on the input image data and then the graphic image data is synthesized with the image data after the luminance adjustment process. By using such a method, by controlling the emission luminance of each light source based on the feature amount acquired from the image data (synthesized image data) after the graphic image data is synthesized, the synthesized image data is displayed. Graphic images can be displayed stably. However, in this case, since the feature amount is acquired from the image data after being multiplied by the user instruction gain value, the feature amount changes due to the change of the user instruction gain value. That is, the light emission luminance of the light source varies due to the variation of the user instruction gain value.

  Therefore, in this embodiment, when displaying an image on which a graphics image is superimposed, the image processing unit 311 performs the following processing. That is, the luminance adjustment process is performed so that the luminance of the graphic image does not change. Specifically, the luminance adjustment processing is performed so that the pixel of the graphics image is not multiplied by the user adjustment gain value. Then, the feature amount is acquired from the image data (synthesized image data) representing the image on which the graphics image is superimposed, and the light emission luminance of each light source is controlled based on the acquired feature amount.

The graphic superimposing unit 312 generates combined image data by combining the graphic image data with the image data output from the second gain multiplying unit 102 (image data after being multiplied by the gain value Gf). Then, the graphic superimposing unit 312 outputs the composite image data to the feature amount acquisition unit 103, the gain mixing unit 306, and the first gain multiplication unit 107. In addition, the graphic superimposing unit 312 outputs region information representing the region of the graphic image to the gain mixing unit 306. The area information is, for example, start point coordinates and end point coordinates of the area of the graphic image. The start point coordinates are, for example, the coordinates of the upper left corner of the region. The end point coordinates are, for example, the coordinates of the lower right corner of the region.
The area information is not limited to the above information. As long as the information represents the area of the graphic image, the area information may be any information. For example, the area information may be the position and size of the area of the graphic image.

  The gain mixing unit 306 performs the following processing when the user instruction gain value is acquired from the mode switching unit 101, that is, when the first mode is set. That is, for the pixels other than the graphic image pixels, the gain mixing unit 306 calculates a mixed gain value obtained by mixing the luminance compensation gain value and the user-indicated gain value, as in the first embodiment, and calculates the calculated mixed gain value. Output. Then, the gain mixing unit 306 outputs the luminance compensation gain value as the mixed gain value for the pixels of the graphic image.

According to such a configuration, when the first mode is set, the feature amount is acquired from the combined image data obtained by combining the graphics image data with the input image data, and based on the acquired feature amount. The light emission luminance of each light source is controlled. As a result, it is possible to prevent fluctuations in the light emission luminance due to fluctuations in the user-designated gain value, and it is possible to cause the light source to emit light with a light emission luminance considering a graphic image. Then, for pixels other than the graphic image pixel, the gradation value is multiplied by the user-indicated gain value and the luminance compensation gain value, and for the graphic image pixel, the gradation value is not multiplied by the user-indicated gain value. Only the compensation gain value is multiplied. Accordingly, the brightness of the display image can be adjusted while suppressing an increase in the amount of black floating, and the graphic image can be displayed with stable luminance.
As described above, according to the present embodiment, it is possible to provide a brightness adjustment function (function for adjusting the brightness of the screen) that achieves both the stability of the graphic display brightness and the stability of the black level.

  In this embodiment, the example in which the display device performs the process of superimposing the graphic image has been described. However, the process may be performed by an external device. Then, image data representing an image on which a graphic image is superimposed may be input as input image data. In that case, using the metadata added to the image data, it is determined whether the graphic image is superimposed, the area where the graphic image is superimposed is determined, and the area of the graphic image is determined. The brightness adjustment process may be performed on the other area.

  In the present embodiment, the above-described configuration is adopted in order to achieve both the stability of graphic display luminance and the stability of black level. However, the present invention is not limited to this. For example, the first mode may be forcibly disabled when displaying a graphic image. Then, an operation mode other than the first mode (for example, the second mode) may be forcibly enabled when displaying a graphic image. Thereby, when the first mode is set, it is possible to prevent the display luminance of the graphic image from being changed by multiplying the pixel of the graphic image by the user adjustment gain.

<Other examples>
The present invention can also be implemented by a system (or a device such as a CPU or MPU) of a system or apparatus that implements the functions of the above-described embodiments by reading and executing a program recorded in a storage device. The present invention can also be implemented by a method comprising steps executed by a computer of a system or apparatus that implements the functions of the above-described embodiments by reading and executing a program recorded in a storage device, for example. . For this purpose, the program is stored in the computer from, for example, various types of recording media that can serve as the storage device (ie, computer-readable recording media that holds data non-temporarily). Provided to. Therefore, the computer (including devices such as CPU and MPU), the method, the program (including program code and program product), and the computer-readable recording medium that holds the program non-temporarily are all present. It is included in the category of the invention.

DESCRIPTION OF SYMBOLS 103 ... Feature-value acquisition part 104 ... Target brightness | luminance determination part 108 ... Liquid crystal panel 109 ... Backlight control value determination part 110 ... Backlight 111, 211, 311 ... Image processing part

Claims (19)

A light emitting means having a plurality of light sources capable of individually controlling the light emission brightness;
Display means for displaying an image on a screen by modulating light from the light emitting means based on input image data;
Image processing means for performing brightness adjustment processing for adjusting brightness on the image data, and outputting the image data after the brightness adjustment processing to the display means;
For each of a plurality of areas on the screen corresponding to the plurality of light sources, from image data close to the image data before being subjected to the luminance adjustment processing compared to image data after being subjected to the luminance adjustment processing, Acquisition means for acquiring a feature amount representing the luminance of the image data in the region;
Control means for controlling the light emission luminance of each light source based on the feature amount obtained by the obtaining means;
A display device comprising: The display device according to claim 1, wherein the acquisition unit acquires a feature amount from image data before the luminance adjustment process is performed. The display device has a first mode and a second mode,
The acquisition means includes
When the first mode is set, the feature amount is acquired from the image data before the luminance adjustment processing is performed,
2. The display device according to claim 1, wherein, when the second mode is set, a feature amount is acquired from image data after the luminance adjustment processing is performed. The brightness adjustment process is a process of adjusting the brightness of the image data at a set rate of increase,
The acquisition means includes
When the set rate of increase is less than or equal to the threshold value, the feature amount is acquired from the image data whose luminance is adjusted at the rate of increase,
2. The display device according to claim 1, wherein when the set increase rate is larger than the threshold value, a feature amount is acquired from image data whose luminance is adjusted at an increase rate equal to the threshold value. The display device according to claim 4, wherein the threshold value is a value set by a user. A judgment means for judging the brightness of the image data before the brightness adjustment processing is performed;
The said acquisition means changes the said threshold value according to the brightness | luminance judged by the said judgment means so that the said threshold value may become large, so that the brightness | luminance judged by the said judgment means is low. Display device. A determination means for determining whether or not the image data before the brightness adjustment processing is dark image data;
The acquisition means includes
When it is determined that the image data before the luminance adjustment processing is dark image data, a feature amount is acquired from the image data before the luminance adjustment processing is performed,
The feature amount is obtained from the image data after the luminance adjustment processing when it is determined that the image data before the luminance adjustment processing is not dark image data. The display device according to 1. When displaying an image with a graphic image superimposed,
The image processing means performs the luminance adjustment processing so that the luminance of the graphic image does not change,
The display device according to claim 1, wherein the acquisition unit acquires a feature amount from image data representing an image on which a graphic image is superimposed. The image processing means performs the brightness adjustment process and a compensation process for compensating for a change in brightness on the screen due to a change in light emission brightness of the light source, and performs the brightness adjustment process and the compensation process. The image data after being output is output to the display means.
The display device according to claim 1, wherein the display device is a display device. A light emitting means having a plurality of light sources capable of individually controlling the light emission brightness;
Display means for displaying an image on a screen by modulating light from the light emitting means based on input image data;
A display device control method comprising:
An image processing step of performing luminance adjustment processing for adjusting luminance on the image data, and outputting the image data after the luminance adjustment processing to the display unit;
For each of a plurality of areas on the screen corresponding to the plurality of light sources, from image data close to the image data before being subjected to the luminance adjustment processing compared to image data after being subjected to the luminance adjustment processing, An obtaining step for obtaining a feature amount representing luminance of image data in the region;
A control step of controlling the light emission luminance of each light source based on the feature amount acquired in the acquisition step;
A control method for a display device, comprising: The method for controlling a display device according to claim 10, wherein in the obtaining step, a feature amount is obtained from image data before the luminance adjustment processing is performed. The display device has a first mode and a second mode,
In the acquisition step,
When the first mode is set, the feature amount is acquired from the image data before the luminance adjustment processing is performed,
The method for controlling a display device according to claim 10, wherein, when the second mode is set, a feature amount is acquired from image data after the luminance adjustment processing is performed. The brightness adjustment process is a process of adjusting the brightness of the image data at a set rate of increase,
In the acquisition step,
When the set rate of increase is less than or equal to the threshold value, the feature amount is acquired from the image data whose luminance is adjusted at the rate of increase,
The control of the display device according to claim 10, wherein, when the set rate of increase is larger than the threshold value, the feature amount is acquired from image data whose luminance is adjusted at a rate of increase equal to the threshold value. Method. 14. The display device control method according to claim 13, wherein the threshold value is a value set by a user. A determination step of determining the luminance of the image data before the luminance adjustment processing is performed;
14. The acquisition step according to claim 13, wherein the threshold value is changed according to the luminance determined in the determination step so that the threshold value increases as the luminance determined in the determination step decreases. Display device control method. A determination step of determining whether or not the image data before the brightness adjustment processing is dark image data;
In the acquisition step,
When it is determined that the image data before the luminance adjustment processing is dark image data, a feature amount is acquired from the image data before the luminance adjustment processing is performed,
The feature amount is obtained from the image data after the luminance adjustment processing when it is determined that the image data before the luminance adjustment processing is not dark image data. 11. A method for controlling a display device according to 10. When displaying an image with a graphic image superimposed,
In the image processing step, the luminance adjustment processing is performed so that the luminance of the graphic image does not change,
17. The display device control method according to claim 10, wherein in the obtaining step, a feature amount is obtained from image data representing an image on which a graphic image is superimposed. In the image processing step, the brightness adjustment process and a compensation process for compensating for a change in brightness on the screen due to a change in emission brightness of the light source are performed on the image data, and the brightness adjustment process and the compensation process are performed. The image data after being output is output to the display means.
The method for controlling a display device according to any one of claims 10 to 17,   A program for causing a computer to execute each step of the control method for a display device according to any one of claims 10 to 18.

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