JP5091701B2 - Liquid crystal display - Google Patents

Description

  The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device capable of adjusting the light emission luminance of a light source that irradiates a liquid crystal panel.

  In recent years, liquid crystal display devices with high display quality have been actively developed by reducing the power consumption and increasing the display contrast by modulating the light emission luminance of the backlight as the light source according to the feature amount of the video signal. ing.

  Patent Document 1 describes a technique for detecting a histogram of an input video signal and modulating the light emission luminance of the backlight according to the detected histogram, and particularly when the histogram distribution is in a predetermined distribution state. It describes that the light emission luminance of the light is fixed, and conversely, when the histogram distribution deviates from a predetermined distribution state, control is performed so that the light emission luminance of the backlight continuously increases. Also, cited document 1 describes that the change speed may be changed between when the emission luminance of the backlight is increased and when it is decreased.

  Japanese Patent Application Laid-Open No. 2004-228561 describes that the input video signal can be viewed without a sense of incongruity when the light emission luminance of the backlight is modulated according to the average luminance level (Average Picture Level: APL) of the input video signal. A technique is described in which the followability of the change in the backlight emission luminance with respect to the change in the feature amount is set according to the genre of the video.

  In this way, in a liquid crystal display device that variably controls the light emission luminance of the backlight according to the histogram or APL of the input video signal, the backlight emission luminance is not simply modulated according to the feature amount of the input video signal. It has been proposed to provide a temporal filter to smoothly change the light emission luminance of the backlight, eliminate flickering of the display due to the change in the light emission luminance of the backlight, and improve the display quality.

  By the way, in the liquid crystal display device that changes the light emission luminance of the backlight according to the input video signal as described in Patent Document 1 or Patent Document 2, when the light emission luminance of the backlight is lowered, the luminance obtained from the display screen is It will be lower than the desired display brightness. Therefore, recently, a technique for increasing the gain of the input video signal in accordance with the amount of decrease in the light emission luminance of the backlight has been developed in order to compensate for the decrease in the display luminance due to the decrease in the light emission luminance of the backlight.

  In Patent Document 3, in order to display a screen with high gradation according to the dynamic range of the image display device even when the luminance distribution of the video signal is dark as a whole, the luminance distribution of the video signal is histogrammed. An image display device is described that performs control to lower the light emission luminance of the backlight and raise the video signal when the minimum luminance obtained from the histogram is equal to or less than a predetermined ratio (for example, 1/2) of the dynamic range that can be displayed on the display screen. ing.

Furthermore, as a technique for smoothly controlling the luminance of the backlight, Patent Document 4 discloses that an image in which half of the screen is black and the other half is white, or a screen having information such as white character telop in the image. However, in order to obtain a sufficient black floating suppression effect, the amount of light is adjusted based on the histogram distribution of the luminance of the input video signal and the darkness parameter indicating the darkness level for each luminance signal level. It is described that gradation correction is performed accordingly. In Patent Document 4, when a scene change is not detected by the scene change detection means, the light amount control amount is smoothed by a low-pass filter, and when a scene change is detected, the low-pass filter is turned off to match the scene change. It is also described that the light quantity control is performed.
JP 2004-110050 A JP 2007-143122 A JP 2006-276677 A JP 2007-272023 A

  As described in Patent Document 3 and Patent Document 4, even in the technique of gain-converting a video signal in conjunction with backlight emission luminance control, the backlight emission luminance can be changed smoothly and temporally to obtain a backlight. The display flicker due to the luminance change is eliminated, and a liquid crystal display device with higher display quality becomes possible.

  However, in the case of such a configuration, it is necessary to change the gain setting together with the light emission luminance of the backlight smoothly in the same manner (matching the output delay amount).

  Therefore, the invention described in Patent Document 1 and Patent Document 2 described only to change the light emission luminance of the backlight smoothly with time and the invention described in Patent Document 3 and Patent Document 4 are simply combined. However, the output delay amount of the backlight luminance change and the output delay amount display of the gain setting value will be shifted, and the display quality will deteriorate.

  The present invention has been made in view of the above circumstances, and provides a liquid crystal display device with high display quality by appropriately linking the change in luminance of the backlight and the gain setting of the input video signal. Is the purpose.

In order to solve the above-mentioned problems, a first technical means of the present invention is a liquid crystal panel that displays an image based on an input video signal, a light source that illuminates the liquid crystal panel, and a light source control that adjusts the light emission luminance of the light source. And a gain setting unit for setting the gain of the input video signal, and controlling the emission luminance of the light source and the gain setting in conjunction with each other. A first temporary filter that outputs a delayed output, and a delay unit that outputs a light emission luminance signal output from the first temporary filter in a delayed manner in accordance with the video output to the liquid crystal panel. setting portion includes a second temporary filter for delaying and outputting the signal for the gain setting obtained from the input video signal, the liquid crystal display device, the first temporary off Whether to output the signal to delay for the gain set by the second temporary filter in accordance with the output delay amount of the light source luminance signal output from the filter, or the output from the second temporary filter The light source luminance signal is delayed and output by the first temporary filter according to the output delay amount of the signal for gain setting.

A second technical means is the first technical means, wherein the first temporary filter the second temporary filter is obtained by said filter der Rukoto the same time constant.

A third technical means includes a scene change detection unit that detects whether or not a scene change has occurred based on the feature amount of the input video signal in the second technical means, and the scene change detection unit detects a scene change. The filter coefficients of the first temporary filter and the second temporary filter are changed depending on whether or not.

A fourth technical means includes a scene change detection unit for detecting whether or not a scene change is made based on a feature amount of the input video signal in the first or second technical means, and the scene change detection unit If it is determined that the without output delay in the first temporary filter and the second temporary filter, if it is determined not to be a scene change the first temporary filter and the second This is characterized in that output delay is performed by a temporary filter .

A fifth technical means is the first technical means, of the first of said signal for gain setting of the output delay amount of the light source luminance signal to be outputted from the second temporary filter output from the temporary filter The output delay amount is correlated.

  According to the liquid crystal display device of the present invention, it is possible to improve the display quality by appropriately interlocking the change in luminance of the backlight and the gain setting of the input video signal.

  A liquid crystal display device according to the present invention performs a liquid crystal panel that displays an image based on an input video signal, a light source that illuminates the liquid crystal panel, a light source control unit that adjusts light emission luminance of a backlight, and a gain setting of the input video signal. A gain setting unit is provided to control the backlight emission luminance and gain setting in conjunction with each other. This light source is called a backlight light source or a backlight.

  In each embodiment according to the present invention described below, in the liquid crystal display device, the amplification degree (gain setting) of the input video signal is adjusted according to the video feature amount of the input video signal. A contrast ratio (target CR; CR is a contrast ratio) is set, and video expression is performed so as to approach the target CR by controlling the light emission luminance of the backlight and controlling the gain. Such luminance modulation processing of the video signal and the backlight is referred to as “advanced luminance modulation processing” in this specification. In the present invention, the gain setting is not limited to setting and executing such a target CR, but may be executed according to the video feature quantity of the input video signal (hereinafter simply referred to as the feature quantity). Furthermore, it is preferable to set the gain according to the feature amount of the input video signal because it enables more effective luminance control in terms of the linkage with the backlight emission luminance, but it is not limited to this. Alternatively, for example, gain setting according to only OPC (Optical Picture Control; also referred to as brightness sensor) may be employed.

<Outline of advanced luminance modulation processing>
Ideally, the display brightness when displaying a video faithfully reproduces the level of the video signal to be displayed. That is, when displaying a black screen, the display brightness should ideally be zero. However, in the case of a video display device using a liquid crystal panel and a backlight, the liquid crystal panel actually has a slight light leakage, and even when a black screen is displayed, it is displayed in gray instead of black.

  One of the important performances of a video display apparatus is a contrast ratio (CR). In the video display device, CR is a ratio between the maximum luminance and the minimum luminance on the display panel. In the case of a liquid crystal display device, the maximum luminance is determined by the maximum light emission luminance of the backlight, and the minimum luminance is determined by the amount of light leakage during black display. Therefore, when the light emission luminance of the backlight is constant, the contrast ratio is constant in the same liquid crystal panel.

  FIG. 1 is a graph showing the relationship between the input gradation level (video signal level) and the luminance value on the liquid crystal panel for liquid crystal panels with CR of 3000 and 6000. The input gradation level indicates a pixel value that can be taken by the input video signal (here, the luminance value of the video signal). Although the maximum luminance is the same 450 cd, the display luminance (minimum luminance) on the liquid crystal panel with a pixel value of 0 is 0.15 cd in the case of CR3000 and 0.075 cd in the case of CR6000.

  Here, when the light emission luminance of the light source is reduced to 50% and the input video signal is amplified by a predetermined amount when the CR3000 liquid crystal panel is used, the relationship between the pixel value of the input video signal and the display luminance value of the liquid crystal panel is The relationship is as shown by the dotted line in FIG. 1, and with pixel values 0 to 128, it is possible to express the luminance close to that of a CR6000 liquid crystal panel. However, an image with a pixel value greater than 128 cannot be expressed in gradation, and so-called whitening occurs. Therefore, it is necessary to adjust the light emission luminance of the backlight and set the gain according to the feature amount of the input video signal.

  For example, when the luminance histogram of the input video signal shows a luminance distribution with a pixel value of 128 or less, the luminance luminance of the backlight is reduced to 50% as shown in FIG. Control that allows quantitative amplification may be performed. By controlling the backlight emission luminance and setting the gain in accordance with the feature amount of the input video signal in this way, it is possible to increase the contrast feeling and at the same time to save power by lowering the backlight emission luminance. It becomes possible.

  In the above description, the case where the luminance histogram of the input video signal shows a luminance distribution with a pixel value of 128 or less has been described as an example. However, other than the above example, for example, when the white portion in the video is extremely small, The degree of importance can be lowered and black expression can be improved in the same manner. At this time, the unsharp portions of the white area may be ignored, or the gain in the white area may be determined so that the white area can be reduced by the gain setting for realizing the target CR.

  In addition, in the advanced luminance modulation process, in order to save power, a process for dynamically reducing the luminance of the backlight according to the feature amount such as APL of the video obtained from the video signal is also executed as described later. To do.

  That is, a reference light emission luminance level for setting the gain setting and the light emission luminance level of the backlight is first set in accordance with the video feature amount (histogram information such as APL and peak (maximum luminance value)) to save power. In addition to the above-described reference light emission luminance level, a process for producing a contrast feeling as described above (that is, a process for setting the light emission luminance level to an appropriate value equal to or lower than the reference light emission luminance level) is performed. This is a process for improving the CR and further reducing power consumption, setting the gain of the video signal in conjunction with the process, and maintaining the visual brightness.

<System configuration example of a liquid crystal display device that performs advanced luminance modulation processing>
FIG. 2 is a block diagram showing a system configuration example of the liquid crystal display device according to the embodiment of the present invention. The liquid crystal display device illustrated in FIG. 2 includes a scaling unit 1, a Y histogram detection unit 2, an APL detection unit 3, a BL (backlight) luminance level setting unit 8, a CPU (Central Processing Unit) / CPLD (Complex Programmable Logic Device). 11, a BL adjustment unit 12, an image quality correction unit 14, an RGBγ / WB (White Balance) adjustment unit 15, an FRC (Frame Rate Control) unit 16, and a video output unit 17.

The liquid crystal display device illustrated in FIG. 2 further includes an advanced luminance modulation unit 20 that executes the main part of the above-described advanced luminance modulation processing. The advanced luminance modulation unit 20 includes a histogram stretching unit 4, a distortion module 5, a scene change detection unit 6, a first temporary filter 7, a second temporary filter 9, a variable delay 10, and a configuration design unit 13. The advanced luminance modulation unit 20 may be configured to implement part or all of the processing by software. As described above, the advanced luminance modulation processing not only performs dynamic backlight emission luminance control according to a feature quantity such as APL, but also the backlight brightness determined by a predetermined condition of the feature quantity. This is an evolved luminance modulation process in which a light emission luminance level BL _reduced that gives a sense of contrast to the reference light emission luminance level BL _ref is selected and the gain of the video signal is also set.

First, the outline of each block in the liquid crystal display device of FIG. 2 will be described.
The video output unit 17 includes a liquid crystal panel that displays video based on the video signal, and a liquid crystal control circuit that converts the video signal into a signal for driving the liquid crystal panel and outputs the signal to the liquid crystal panel. Although the details will be described later, the video signal is converted using the gain set by the advanced luminance modulation unit 20 and then input to the video output unit 17. That is, in the advanced luminance modulation process, a video signal indicating a video to be displayed by the video output unit 17 is a processing target. The gain and its setting will be described later.

  The BL adjustment unit 12 includes a lamp composed of a fluorescent tube and a lamp driving circuit that drives the lamp, and constitutes a backlight that irradiates the liquid crystal panel from the back and side surfaces. In the advanced luminance modulation process, this lamp is a target of light emission luminance control.

The BL adjustment unit 12 is controlled by the CPU / CPLD 11. The CPU / CPLD 11 actually uses the lamp driving circuit (for example, an inverter circuit) of the BL adjustment unit 12 according to a signal (for example, a duty signal (backlight DUTY)) indicating the light emission luminance level BL _reduced output from the advanced luminance modulation unit 20. The light is converted into a signal for dimming (for example, a signal suitable for driving such as pulse width modulation) and output to the BL adjustment unit 12. The backlight dimming value is converted into a signal for actual backlight dimming. Further, as the lamp, for example, a lamp composed of an LED (Light Emitting Diode) or a combination of an LED and a fluorescent tube may be adopted, and at the same time, a lamp driving circuit corresponding to the lamp may be provided. Good.

  The parts for processing the video signal output to the video output unit 17 and controlling the BL adjustment unit 12 via the CPU / CPLD 11 are the scaling unit 1, the Y histogram detection unit 2, the APL detection unit 3, and the BL luminance level setting unit. 8, an image quality correction unit 14, an RGBγ / WB adjustment unit 15, an FRC unit 16, and an advanced luminance modulation unit 20.

  First, the scaling unit 1 changes the number of pixels of the video frame indicated by the input video signal (input video signal) or the aspect ratio of the video frame by calculation according to the resolution of the liquid crystal panel and the like.

  Here, as the input video signal, for example, a signal obtained by demodulating a video signal received as a broadcast wave, a video signal received via a communication network, a signal obtained by reading a video signal stored in an internal storage device, various recorders and various players This corresponds to a video signal received from an external device such as a tuner device or a tuner device, or a video signal obtained by performing various video processes on the video signal. Although not shown, the liquid crystal display device of FIG. 2 may be configured to be able to acquire any of such video signals.

  The image quality correction unit 14 changes the contrast, color, and the like of the video with respect to the video signal output from the scaling unit 1 according to user settings and the like.

  The RGB γ / WB adjustment unit 15 adjusts γ, WB, and the like of the video for the video signal output from the image quality correction unit 14. Furthermore, the RGBγ / WB adjustment unit 15 changes the gain of the signal by a gain setting signal from the advanced luminance modulation unit 20 (configuration design unit 13 in FIG. 2). Here, the gain for the video signal output from the image quality correction unit 14 is changed, or the gain for the video signal after γ adjustment in the RGB γ / WB adjustment unit 15 is changed. Then, the RGBγ / WB adjustment unit 15 performs conversion of the video signal based on the gain, and compensates for the luminance reduction by the gain with respect to the control for reducing the light emission luminance level by the advanced luminance modulation unit 20 as described later. Here, in order to suppress noise in the low gradation part, this conversion is preferably performed after γ adjustment and before WB adjustment.

  The gain setting signal from the advanced luminance modulation unit 20 is a signal indicating a conversion coefficient (gain setting value) for converting the pixel value (video signal level) of the video signal to be output to the liquid crystal panel. This gain setting signal is a common conversion coefficient for multiplying each video signal level (in this example, a value of 0 to 255) as shown in the following example, and gaining a peak by gaining as described later. The gain may be corrected by the RGBγ / WB adjustment unit 15 for a certain video signal level range obtained based on the video signal level range.

  The FRC unit 16 is a frame rate converter, and detects the motion vector of the video from the adjusted video signal output from the RGB γ / WB adjustment unit 15 to generate a complementary video, thereby generating a normal video from a display frequency of 60 Hz. The display frequency is converted to 120 Hz. Of course, the display frequency to be processed in the FRC unit 16 and the display frequency after processing are not limited to this. In the example of FIG. 2, the liquid crystal driving circuit of the video output unit 17 converts the video signal output from the FRC unit 16 into a signal for driving the liquid crystal panel and outputs the signal to the liquid crystal panel.

  The Y histogram detection unit 2 divides the video frame into pixel units and generates a histogram representing the frequency of occurrence of the luminance value of each pixel. The histogram generated by the Y histogram detection unit 2 has a frequency value for each of luminance values (Y) 0 to 255, for example. The APL detection unit 3 calculates the average luminance level of the video signal for each video frame. The value calculated by the APL detection unit 3 is a value indicating 0% when the entire screen is black, and a value indicating 100% when the entire screen is white.

  The histogram stretching unit 4 sets a range to be used by the advanced luminance modulation unit 20 from the histogram generated by the Y histogram detection unit 2. For example, the distortion module 5 is a module that performs an operation with a minimum value 0 to a maximum value 255, and the input video signal takes, for example, (i) a minimum value 16 to a maximum value 235 that is a normal encoding output range. It is assumed that the signal is a signal that takes a minimum value 10 to a maximum value 235 in order to express black from (ii). In the case of (i), the histogram stretching unit 4 sets the frequency value for each of the minimum value 16 to the maximum value 235 and the frequency value for each of the minimum value 0 to the maximum value 255 in order to match the calculation in the distortion module 5. In the case of (ii), the frequency value for each of the minimum value 10 to the maximum value 235 is extended so as to be applied to the frequency value for each of the minimum value 0 to the maximum value 255. .

The distortion module 5 actually uses the histogram input from the histogram stretching unit 4 and the reference emission luminance level (also referred to as a backlight target value) BL _ref set by the BL luminance level setting unit 8 described later. A light emission luminance level to be set (also referred to as a backlight value) BL _reduced , that is, a light emission luminance level used for backlight control is selected (determined) and output. The selection is performed in a range that does not exceed the reference light emission luminance level BL _ref set by the BL luminance level setting unit 8 from a plurality of predetermined light emission luminance levels. Here, the backlight value BL _reduced that can realize a display image closer to the liquid crystal panel having the target CR is selected. The distortion parameters such as the target CR may be set from a main CPU (not shown).

  The scene change detection unit 6 detects the presence or absence of a scene change from the degree of change between the histogram one frame before and the current histogram. For example, the cumulative value of the frequency change of each luminance value is calculated, and if it is larger than a specific value, it is determined that the scene has changed. The detection result of the scene change detection unit 6 is used by the first and second temporary filters 7 and 9.

The first temporary filter 7 is a main feature of the present invention. To explain the outline, the first temporary filter 7 has a visual discomfort caused when the light emission luminance level BL _reduced (backlight DUTY) actually set selected by the distortion module 5 changes abruptly. This is provided to prevent this, and after the amount of change in the light emission luminance level BL _reduced is made slow in time, it is output to the subsequent stage as the light emission luminance level BL _{reduced that} is actually set. At the time of a scene change, since a slow change in the light emission luminance level BL _reduced is returned and the _{user feels} uncomfortable, the value of the first temporary filter 7 is changed by a scene change detection signal from the scene change detection unit 6 so that the change is relatively fast. To be able to.

The BL luminance level setting unit 8 refers to the APL value of the video signal output from the scaling unit 1, and refers to the OPC value or user setting value output from the main CPU (not shown), and the emission luminance level of the backlight. Determine the maximum value of. For example, when the APL is high, the maximum value of the light emission luminance level of the backlight is set to a low value so that an image without feeling dazzling can be obtained. The maximum value of the light emission luminance level of the backlight is the reference light emission luminance level (backlight target value) BL _ref for advanced luminance modulation executed by the advanced luminance modulation unit 20.

Since the selection by the distortion module 5 is performed within a range that does not exceed the reference emission luminance level BL _ref set by the BL luminance level setting unit 8, the BL luminance level setting unit 8 uses the reference emission luminance level. It is described that the maximum value of the light emission luminance level of the backlight is set as BL _ref .

The second temporary filter 9 is a main feature of the present invention together with the first temporary filter 7. _{Briefly, the} emission luminance level BL _reduced (backlight) output from the first temporary filter 7 when the APL changes rapidly and the change does not affect the selection in the distortion module 5. In DUTY), the temporal change is moderated. However, since the gain setting is calculated based on the reference light emission luminance level BL _ref output from the BL luminance level setting unit 8, the gain changes and the display luminance on the liquid crystal panel changes abruptly. In order to eliminate or alleviate such a rapid change in display luminance, the second temporary filter 9 is provided. By making the second temporary filter 9 a filter having a function equivalent to that of the first temporary filter 7, it is possible to eliminate a sudden change. Further, at the time of a scene change, the value of the second temporary filter 9 is also changed based on the detection result from the scene change detection unit 6 so as to follow the change of the value of the first temporary filter 7 so that there is no sense of incongruity. It is preferable to do.

  The variable delay 10 is a delay unit for timing the video output from the video output unit 17 and the backlight dimming in the BL adjustment unit 12. In backlight dimming, backlight luminance control is performed after a relatively small amount of processing if the dimming value is determined. On the other hand, the video signal gain is determined by advanced luminance modulation, the frame rate is controlled by the FRC unit 16 and converted to the panel control signal by the liquid crystal control circuit after the luminance level of the video signal is changed. Since many processes are performed, a time delay occurs. Then, the timing of the backlight dimming control and the video gain control that should be performed at the same time is shifted, and the balance between the backlight and the video is lost. Therefore, the backlight dimming is intentionally delayed by the variable delay 10 (the backlight DUTY output from the advanced luminance modulation unit 20 is delayed), and the timings of the backlight dimming control and the video gain control are matched.

The configuration design unit 13 determines the gain of the video signal based on the reference emission luminance level BL _ref determined by the BL luminance level setting unit 8 and the emission luminance level BL _reduced selected by the distortion module 5. In the example of FIG. 2, the levels BL _reduced and BL _ref are levels that have passed through the temporary filters 7 and 9, respectively. If the reference light emission luminance level (backlight target value) BL _ref and the selected light emission luminance level (backlight value) BL _reduced are the same, there is no need to change the luminance level of the video signal, and the gain setting value is 1. It is. Further, when the selected light emission luminance level is lower than the reference light emission luminance level, the gain is set in a direction to increase the luminance level of the video signal according to the value.

<Detailed description of main blocks for executing advanced luminance modulation processing>
The BL luminance level setting unit 8, the distortion module 5, the configuration design unit 13, and the RGBγ / WB adjustment unit 15 will be described in this order as main blocks for executing the advanced luminance modulation processing in the liquid crystal display device of FIG. Specific examples of processing are also given. Note that the second temporary filter 9, the first temporary filter 7, and the scene change detection unit 6, which are the main features of the present invention, will be described later separately as filter incorporation examples.

<< BL brightness level setting section 8 >>
The BL luminance level setting unit 8 receives the APL of the video signal detected by the APL detection unit 3 and controls based on detection information from a brightness sensor (not shown) that measures the ambient brightness (ambient illuminance). A signal and a control signal based on a user setting for setting the brightness of the liquid crystal panel are input. Then, the BL luminance level setting unit 8 outputs the reference light emission luminance level BL _ref based on these control signals and APL. More specifically, a method of dynamically adjusting the backlight luminance according to the APL of the input video signal that changes in screen units (frame units) is applied, and the light emission luminance level obtained thereby is used for reference light emission. Output as luminance level BL _ref .

A luminance control table (lookup table) held in the BL luminance level setting unit 8 is used to generate the reference emission luminance level BL _ref . The luminance control table defines the relationship of the light emission luminance level of the backlight according to the video feature amount (APL in this case) of the input video signal, that is, the luminance control characteristic. A plurality of selectable brightness control tables are prepared and held in a table storage memory such as a ROM (Read Only Memory) provided in the BL brightness level setting unit 8.

  For example, a photodiode is applied to a brightness sensor that measures the brightness around the liquid crystal display device. The brightness sensor generates a DC voltage signal corresponding to the detected ambient light and outputs it to a main CPU (not shown). The main CPU outputs a control signal for selecting the brightness control table to the BL brightness level setting unit 8 according to the DC voltage signal corresponding to the ambient light.

  Further, the main CPU outputs a luminance adjustment coefficient for adjusting the luminance control value of the luminance control table as a control signal based on a user setting for setting the brightness of the liquid crystal panel. The brightness adjustment coefficient is used for setting the brightness of the entire screen in accordance with a user operation. For example, screen brightness adjustment items are set on a menu screen held by the liquid crystal display device. The user can set an arbitrary screen brightness by operating the setting item. The main CPU recognizes the brightness setting and outputs a brightness adjustment coefficient to the BL brightness level setting unit 8 according to the set brightness.

The BL luminance level setting unit 8 selects a luminance control table by designating a table No. according to a control signal output from the main CPU according to the detection information of the brightness sensor. Alternatively, the luminance control table to be selected may be generated by calculation. Then, the brightness conversion value of the selected brightness control table is multiplied by the brightness adjustment coefficient obtained as a control signal based on the user setting, and the slope of the brightness control characteristic of the brightness control table is changed, and finally, for reference A brightness control table used to generate the light emission brightness level BL _ref is determined. Then, the BL luminance level setting unit 8 uses the luminance control characteristic of the determined luminance control table to generate and output a reference emission luminance level BL _ref according to the APL output from the APL detection unit 3.

As described above, the luminance control table defines the relationship between the APL that is the feature amount of the input video signal and the light emission luminance level of the backlight. For example, when the APL is large, the light emission luminance level of the backlight is small. By setting so as to be, the luminance of the backlight is suppressed so as not to feel dazzling in the case of a high-luminance image. In accordance with the luminance control characteristics of the luminance control table, the light emission luminance level BL _ref dynamically changes according to the change in the APL of the video signal. In the present embodiment, the brightness control characteristics in the brightness control table are not particularly limited, and the characteristics that dynamically change the light emission brightness level of the backlight according to the feature amount of the input video signal are defined. It can be applied as appropriate. In addition, although the example which employ | adopted APL as a feature-value of an input video signal was shown, you may employ | adopt the peak luminance value obtained from the Y histogram detection part 2, or a peak luminance value and APL. Further, the BL brightness level setting unit 8 may be configured to realize part or all of the setting processing by software.

The reference emission luminance level BL _ref output from the BL luminance level setting unit 8 in this way and delayed by the action of the second temporary filter 9 is input to the configuration design unit 13 and used for the calculation of the video gain. At the same time, it is input to the distortion module 5 and used to determine the emission luminance level BL _reduced according to the histogram.

<< Distortion Module 5 >>
The basic idea of the advanced luminance modulation processing executed by the advanced luminance modulation unit 20 is that the image luminance range that can be displayed when the backlight emission luminance level is 100% in the liquid crystal panel to be used, and the target (also called ideal). By setting the display luminance range that can be displayed on a liquid crystal panel having a CR (target CR) and controlling the light emission luminance level of the backlight in the liquid crystal panel to be used, the liquid crystal panel having the target CR as a performance It is intended to be close to the displayable video luminance range.

  Here, since the light emission luminance level of the backlight is lowered, when the video signal includes a high luminance portion, whiteout occurs in a high luminance portion that cannot be expressed by the reduced backlight emission luminance. Further, when the video signal does not include low luminance, it is not necessary to lower the light emission luminance level of the backlight.

Therefore, the distortion module 5 quantifies the evaluation value (Distortion) as a criterion for determining the backlight luminance, how many low luminance portions and high luminance portions cannot be expressed at a certain emission luminance level. Here, the distortion module 5 performs this quantification within a predetermined backlight luminance control range, and selects and outputs the emission luminance level having the smallest evaluation value as the emission luminance level BL _reduced (backlight DUTY). And The luminance control range of the backlight is one of distortion parameters and indicates a range allowed as the light emission luminance level of the backlight. For example, 10% to 100%, 20% to 100%, and the like may be determined in advance by default setting or user setting.

When there are a plurality of light emission luminance levels with the smallest evaluation value, a lower light emission luminance level is selected as the light emission luminance level BL _reduced . This is because, if the image representation quality on the liquid crystal panel is equivalent, lowering the light emission luminance level of the backlight saves power.

  FIG. 3 is a diagram for explaining an example of the light emission luminance level selection process executed by the distortion module in the liquid crystal display device of FIG. h1 represents a Y histogram of the video signal. Here, the horizontal axis represents the input gradation of the video signal (also referred to as a pixel value or video signal level that can be taken as the video signal), and the vertical axis represents the frequency of each video signal level.

  For such a video histogram h1, A is a video luminance range that can be displayed when the light emission luminance level of the backlight is 100% in the liquid crystal panel to be used. Also, let B be the video luminance range that can be displayed on the liquid crystal panel of the target CR. Also, let C be a video luminance range that can be displayed at a specific light emission luminance level among the light emission luminance levels that can be selected by the distortion module 5. In the histogram h1, the portions that overlap the video luminance range B on both sides of the video luminance range C are the portions to be subjected to the above-mentioned numericalization, and are evaluation value calculation portions. Of the evaluation value calculation portion, the low luminance portion is D1 and the high luminance portion is D2.

The evaluation value (Distortion) is calculated by the following equation (1) based on the frequency and weighting with respect to the selectable light emission luminance level.
Distortion = Σ {(frequency of image luminance range D1 + D2) × (distance weight)} (1)

  As the weight, a distance weight that increases as the distance from the image luminance range C that can be displayed at the light emission luminance level that is an evaluation value calculation target increases. Here, the distance weight of the low luminance portion D1 is E1, and the distance weight of the high luminance portion D2 is E2. Therefore, even if the frequency value is the same, the evaluation value becomes larger as it is far from the range that can be expressed. This is because the farther from the range that can be expressed, the greater the influence that cannot be expressed as video. The values calculated by the frequency and the weight are F1 (low luminance part) and F2 (high luminance part). The evaluation value is the sum of the areas (cumulative total) of F1 and F2.

In the distortion module 5, the light emission luminance level corresponding to the video luminance range C having the lowest evaluation value among the evaluation values calculated for each light emission luminance level is selected as the light emission luminance level BL _reduced to be output. At this time, the distortion module 5 selects the light emission luminance level BL _reduced corresponding to the video luminance range C having the lowest evaluation value within a range not _exceeding the light emission luminance level BL _ref set by the BL luminance level setting unit 8.

  Ideally, the evaluation value is calculated for all selectable light emission luminance levels in the distortion module 5. However, since there is a limitation on the processing time or the like, the luminance control range of selectable light emission luminance levels may be equally divided, and for example, the light emission luminance level may be calculated for every about 10%.

That is, the video luminance range that can be displayed at the specific light emission luminance level of the above equation (1) is set as C, and the selectable light emission luminance levels are sequentially applied, and the evaluation value is calculated for each light emission luminance level. Then, the light emission luminance level having the lowest evaluation value among the calculated evaluation values is set as the selected light emission luminance level BL _reduced, and this value is output to the first temporary filter 7 in the example of FIG. In addition to being used for light dimming control, it is output to the configuration design unit 13 and used for setting (calculating) video gain.

  The selection process in the distortion module 5 will be described with specific numerical values with reference to FIGS. FIG. 4 is a diagram for explaining a specific example of the advanced luminance modulation processing in the liquid crystal display device of FIG. 2, and is a diagram illustrating an example of the relationship between the panel CR and the target CR in the video histogram. Here, the maximum luminance of the liquid crystal panel is 450 cd when the CR (panel CR) of the liquid crystal panel to be used is 2000, the target CR is 3500, the luminance control range of the backlight is 20 to 100%, and the backlight luminance is 100%. To do. Moreover, each alphabet symbol in FIG. 4 is based on FIG.

  In this example, the video luminance range A that can be displayed on the liquid crystal panel to be used is 450 cd to 0.225 cd. In addition, the target video luminance range B that can be displayed on the liquid crystal panel is 450 cd to 0.128 cd. Then, the frequency for each video signal level 0 to 255 is assigned so as to match the video luminance range B. In this case, the difference between the video luminance range A and the video luminance range B is about 5 digits.

If there is an image in the difference between the image luminance range B and the image luminance range A in the histogram h1, the luminance expression closer to the target CR can be expressed by lowering the light emission luminance level of the backlight. However, if an image is distributed on the high luminance side, a portion that cannot be expressed by reducing the light emission luminance level of the backlight occurs. Therefore, as described above, the evaluation value is calculated to obtain the optimum light emission luminance level BL _reduced .

  FIG. 5 is a diagram showing a video luminance range C when the light emission luminance level is 100%, which is one of the selection targets, and FIG. 6 is a video luminance range when the light emission luminance level is about 70%, which is one of the selection targets. FIG. 7 is a diagram showing a video luminance range C at a light emission luminance level of about 50%, which is one of the selection targets. Each alphabet symbol in FIGS. 5-7 is based on FIG.

  As shown in FIG. 5, when the light emission luminance level is 100%, the evaluation value F1 for the low luminance portion has a certain value, and the evaluation value F2 for the high luminance portion has no value. . Further, as shown in FIG. 6, when the emission luminance level is lowered to about 70%, both the low luminance portion evaluation value F1 and the high luminance portion evaluation value F2 have low values. Further, as shown in FIG. 7, when the emission luminance level is lowered to about 50%, the evaluation value F1 for the low luminance portion has no value, and the evaluation value F2 for the high luminance portion has a large value. Comparing the areas (cumulative values) of the evaluation value calculation results at the respective light emission luminance levels exemplified in FIGS. 5 to 7, the light emission luminance level is the lowest when it is 70%. Therefore, the distortion module 5 selects and outputs a light emission luminance level of 70%.

<< Configuration Design Section 13 >>
A basic model showing the relationship between the pixel value input to the liquid crystal panel and the display brightness on the liquid crystal panel is expressed by the following equation (2). Here, Y is the display luminance on the liquid crystal panel, BL is the light emission luminance level of the backlight (backlight DUTY), and CV (Code Value) is the pixel value input to the liquid crystal panel. In this example, it is assumed that the gradation of the video signal is quantized from 0 to 255.
Y = BL (CV / 255) ^γ (2)

The configuration design unit 13 adjusts the video gain so that the luminance on the screen is increased when the luminance of the backlight is _reduced by the luminance level BL _reduced selected by the distortion module 5. When the pixel value to which the gain is applied is CV _reduced , the screen brightness (display brightness on the liquid crystal panel) when the light emission brightness level is reduced is BL _reduced (CV _reduced / 255) ^γ . On the other hand, the brightness of the screen when the backlight is controlled at the reference emission luminance level BL _ref is BL _ref (CV _ref / 255) ^γ . The pixel values may be determined so that these values are equalized and the decrease in the light emission luminance of the backlight caused by the light emission luminance level BL _reduced is compensated. That is, the configuration design unit 13 may perform a gain setting that satisfies the following expression (3).
Y = BL _reduced (CV _reduced / 255) ^γ = BL _ref (CV _ref / 255) ^γ (3)

Therefore, the gain (G) is expressed by the following equation (4). For example, when the reference light emission luminance level BL _ref is 100%, the following equation (5) is obtained. Note that it is preferable to store the relationship between BL _ref and BL _reduced as a lookup table in the ROM of the configuration design unit 13 or the like so that the arithmetic processing of the following expression (4) is executed at high speed.

G = CV _reduced / CV _ref = (BL _ref / BL _reduced ) ^{1 / γ} (4)
G = (1 / BL _reduced ) ^{1 / γ} (5)

<< RGBγ / WB adjuster 15 >>
FIG. 8 is a diagram illustrating an example of the video signal gain set by the RGB γ / WB adjustment unit based on the gain setting signal output from the advanced luminance modulation unit in the liquid crystal display device of FIG. It is a figure for demonstrating the example of an adjustment process in the RGBgamma / WB adjustment part in a liquid crystal display device.

  With reference to FIG. 8, the relationship between the input gain setting value (conversion coefficient) and the gain curve obtained therefrom will be described. As shown in FIG. 8A, when the gain setting of the video signal output from the advanced luminance modulation unit 20 is 1.0, the gain is simply multiplied by the value for all luminances, that is, remains linear. No problem. However, when the gain is 1.0 or more, as shown in FIG. 8B, the high luminance portion has a uniform value of 255, and so-called whitening occurs. The basic idea of the advanced luminance modulation processing is to tighten black at the expense of white-out of a small number of white luminance portions. Even if the RGBγ / WB adjustment unit 15 executes processing with gain as shown in FIG. 8B. Although it is good, it is better to avoid the high brightness portion from becoming overly constant at a value of 255 (topped).

  Therefore, it is preferable to reduce the gradation deterioration of the high luminance part by performing signal expansion according to the gain setting for low and medium luminance and making the gain curve non-linear for high luminance. This method has a trade-off relationship between brightness and whiteout. If the non-linear region is narrowed, the region in which normal brightness can be expressed increases, but the high luminance gradation is lowered. Conversely, if the non-linear region is widened, the region where normal brightness can be expressed decreases, but the high luminance gradation is maintained to some extent. In an actual product, the non-linear luminance may be made non-linear only in a portion that is affected by white-out, for example, a portion of 90% or more or a portion of 95% or more of the output by gain setting. FIG. 8C shows a gain curve corrected so that a portion of 90% or more becomes non-linear when the gain setting is 1.2. Further, FIG. 8D shows a gain curve corrected so that a portion of 90% or more becomes non-linear when the gain setting is 1.6.

  Further, as described above, in order to avoid the peak when the gain setting exceeds 1.0, it is necessary to make the gain curve partly non-linear. However, the RGBγ / WB adjustment unit 15 cannot calculate such a gain curve simply by proportional calculation based on the gain setting. Therefore, it is conceivable to have a gain curve for each gain setting, but it is difficult due to the memory capacity. Therefore, the linear portion is simply proportionally calculated from the gain setting value, and as illustrated in FIGS. 8C and 8D, the non-linear portion may be calculated by interpolation or the like for the portion of 90% or more. Since the gain setting changes every frame, the gain curve is calculated each time.

  Next, with reference to FIG. 9 and FIG. 10, each adjustment process in the RGBγ / WB adjustment unit 15 will be described. The RGB γ / WB adjustment unit 15 performs processing for obtaining a gain using the above-described gain curve, video γ adjustment processing, WB adjustment processing, CT (color temperature), and the like for the video signal output from the image quality correction unit 14. Also make adjustments. The CT adjustment process may be executed with reference to one adjustment curve together with the WB adjustment process.

  Each process executed by the RGBγ / WB adjustment unit 15 is executed independently for each of R, G, and B of the video signal. At that time, for the γ adjustment process and the gain obtaining process, R, G, and B are calculated by the same curve, and for the WB adjustment process / CT adjustment process, the R, G, and B are calculated by separate characteristic curves. Is made. The order of each process executed by the RGB γ / WB adjustment unit 15 is such that a γ adjustment process is first performed, then a gain obtaining process is performed, and finally a WB adjustment process / CT adjustment process is performed. preferable.

  FIG. 9 shows tone characteristics at the time of output when tone conversion processing is performed in the order of gain processing and γ adjustment processing. FIG. 9A shows tone characteristics by gain processing, and FIG. 9B shows γ adjustment processing. (C) shows the gradation characteristics at the time of output (appearance on the screen). FIG. 10 shows tone characteristics at the time of output when tone conversion processing is performed in the order of γ adjustment processing and gain processing. (A), (B), and (C) are the same as those in FIG. It is the same. Also, the dotted lines in FIGS. 9 and 10 indicate the gradation characteristics by the γ adjustment processing in (B).

  Here, comparing the gradation characteristics (C) at the time of output in FIGS. 9 and 10, it can be seen that FIG. 9 is significantly different from the gradation characteristics of the γ adjustment processing. The gradation characteristic at the time of output needs to reflect an appropriate gradation characteristic adjusted by the γ adjustment process. However, in the processing order as shown in FIG. 9, it is greatly shifted and a desired image quality cannot be obtained. . Therefore, by performing the gain processing after performing the γ adjustment processing as shown in FIG. 10, it is possible to alleviate the deviation of the gradation characteristics at the time of output. Further, if the WB adjustment process / CT adjustment process is performed before the gain process or the like, the WB adjustment process / CT adjustment process will be shifted in the subsequent gain process despite the WB adjustment process / CT adjustment process. By performing this at the end of the gradation conversion, it becomes possible to adjust appropriately.

  By configuring the BL luminance level setting unit 8, the distortion module 5, the configuration design unit 13, and the RGBγ / WB adjustment unit 15, which are main units that execute the advanced luminance modulation processing, as described above, The backlight emission luminance and the gain setting value of the input video signal according to the feature amount can be obtained, thereby enabling video display with high display quality.

  Next, a specific example of the advanced luminance modulation process described above will be described below.

(Specific example 1)
The set values used for the advanced luminance modulation processing of specific example 1 are as follows. Further, only the processing tendency will be schematically described without considering the first and second temporary filters 7 and 9.

(1) Panel CR (contrast ratio of liquid crystal panel to be used): 3000
(2) Target CR (target contrast ratio of liquid crystal panel): 6000
(3) Reference emission brightness level BL _ref to be input: 70%
(4) Backlight brightness control range: 20% to 100%
(5) Input video: all white (video frame whose frequency is distributed only to 255 in the histogram)

  The above (1), (2), and (4) are normally fixed values, and the setting may be changed according to an image quality mode that is selectably provided in the liquid crystal display device, or according to a genre or the like. The above (3) changes in units of frames depending on the video APL value, OPC, user setting, and the like. The above (5) is an input video, and in this specific example, the frequency of white (255) is extremely high.

In this specific example, 70% is set as the reference light emission luminance level BL _ref based on the APL of the video. For example, it is set by a control that lowers the light emission luminance level of the backlight to 70% in order to reduce glare and brightness of the image.

Then, the reference light emission luminance level BL _ref is inputted to the distortion module 5 as 70%. At the same time, the histogram value of the video is also input through the histogram stretching unit 4. Note that the histogram stretching unit 4 adjusts the input video signal to 0 to 255 when the input video signal is a value such as 10 to 235 instead of 0 to 255, and the input video in this specific example is all white (255). Therefore, it is not necessary to consider.

Since the input video (input image) is all white, the video does not exceed 255 even if the luminance of the backlight is lowered and the video is expanded. Therefore, as a result of calculating the evaluation value, the distortion module 5 selects 70% which is the same as the reference emission luminance level BL _ref as the emission luminance level BL _reduced . If the input video is not all white, the distortion module 5 may select a value lower than 70%. Then, 70% is output to the duty signal (backlight duty index) that is finally output to the CPU / CPLD 11.

Next, BL _reduced and BL _ref are input to the configuration design unit 13 for setting the video gain, and (BL _ref / BL _reduced ) ^{1 / γ} shown in the above equation (4) is calculated. In this specific example, it is 70% / 70%, and the gain is 1. That is, this specific example is an example in which the video gain-up control is not performed.

(Specific example 2)
The set values used for the advanced luminance modulation processing of specific example 2 are as follows. That is, only the input video is different from the specific example 1.

(1) Panel CR (contrast ratio of liquid crystal panel to be used): 3000
(2) Target CR (target contrast ratio of liquid crystal panel): 6000
(3) Reference emission brightness level BL _ref to be input: 70%
(4) Backlight brightness control range: 20% to 100%
(5) Input video: Video frame in which only a few white (255) are distributed in black (0)

In this specific example, the distortion module 5 determines that the frequency of white is very low from the histogram of the input image, and gives priority to black expression at the expense of whiteout to some extent. More specifically, among the light emission luminance levels lower than the reference light emission luminance level BL _{ref, the} light emission luminance level (50% in this specific example) at which the evaluation value is calculated and the evaluation value is minimized is set as the light emission luminance level. Select and determine as BL _reduced . Finally, the light emission luminance of the backlight is 50%.

Next, BL _reduced and BL _ref are input to the configuration design unit 13 for setting the video gain, and calculation is performed using the above equation (4). In this specific example, 70% / 50%, and when γ = 2.2, the gain is 1.16.

In this specific example, since the frequency of black is high, priority is given to black at the expense of white, which is less frequent, and a value lower than the reference emission luminance level BL _ref is selected as the emission luminance level BL _reduced . The effect of such selection will be described by taking as an example a case where the brightness of the liquid crystal panel is 450 cd and 0.15 cd when the light emission luminance levels are controlled at 100% and 0%, respectively.

When the light emission luminance level BL _reduced (70%) having the same value as the reference light emission luminance level BL _ref is selected, the white (255) of several maximum values has a brightness of 315 cd (450 × 70%). , Black (0) has a brightness of 0.1 cd (0.15 × 70%).

On the other hand, when the advanced luminance modulation process is performed and the emission luminance level BL _reduced (50%) having a value lower than the reference emission luminance level BL _ref is selected, several maximum values of white (255) are obtained. It has a brightness of 225 cd (450 × 50%), and black (0) has a brightness of 0.075 cd (0.15 × 50%). Therefore, several white points are expressed darker than the original, but black representations can be expressed with near ideal brightness. This is the effect of the advanced luminance modulation process. Of course, if there are no white points, black expression can be enhanced without causing inconvenience such as whiteout.

(Specific example 3)
The set values used for the advanced luminance modulation processing of specific example 3 are as follows. That is, only the specific example 2 and the target CR are different.

(1) Panel CR (contrast ratio of liquid crystal panel to be used): 3000
(2) Target CR (target contrast ratio of liquid crystal panel): 3000
(3) Reference emission brightness level BL _ref to be input: 70%
(4) Backlight brightness control range: 20% to 100%
(5) Input video: Video frame in which only a few white (255) are distributed in black (0)

The same reference emission luminance level BL _ref (70%) as in Example 2 and the same histogram (white with several maximum values in black) are input to the distortion module 5, but the panel CR and target CR are Since they are the same, the distortion module 5 selects a light emission luminance level BL _reduced that does not cause whitening for each luminance value to be configured. More specifically, an evaluation value is calculated, and a light emission luminance level that minimizes the evaluation value is selected. In this specific example, white maximum of several points is prevented from being crushed, so 70% is selected as the light emission luminance level BL _reduced . This is because the reference light emission luminance level is set to 70%, and the light emission luminance level BL _reduced is selected within a range not exceeding the value. Therefore, the gain of the video signal in this specific example is 1.

(Specific example 4)
The set values used for the advanced luminance modulation processing of the specific example 4 are as follows. That is, only the input video is different from the specific example 3.

(1) Panel CR (contrast ratio of liquid crystal panel to be used): 3000
(2) Target CR (target contrast ratio of liquid crystal panel): 3000
(3) Reference emission brightness level BL _ref to be input: 70%
(4) Backlight brightness control range: 20% to 100%
(5) Input video: all black (video frame with frequency distributed only to 0 in the histogram)

In this specific example, since the panel CR and the target CR are the same as in specific example 3, the distortion module 5 selects the light emission luminance level BL _reduced that does not cause collapse for each luminance value to be configured. More specifically, among the light emission luminance levels lower than the reference light emission luminance level BL _ref , the evaluation value is calculated, and the light emission luminance level that minimizes the evaluation value is selected and determined as the light emission luminance level BL _reduced .

  However, since the image of this specific example is all black, a plurality of light emission luminance levels that minimize the evaluation value are selected. In other words, since the image in this specific example is all black, it is possible to reduce the light emission luminance of the backlight without causing collapse of each luminance value.

In this specific example, the luminance control range of the backlight is in the range of 20 to 100%, so the lowest emission luminance level of 20% is selected. Therefore, the final light emission luminance level BL _reduced is 20%, and the gain of the video signal is 1.75. Here, the reason why the lowest value is selected is that it is most advantageous in terms of power saving. As described above, in the distortion module 5, if the evaluation values are the same, it is preferable in terms of power saving to select a lower light emission luminance level.

  The specific example of the advanced luminance modulation processing has been described above. Next, the scene change detection unit 6, the first temporary filter 7, and the second temporary filter 9 described in the advanced luminance modulation unit 20 of FIG. A specific description will be given in consideration of the arrangement of the temporary filter.

  First, a specific operation of the scene change detection unit 6 will be described. 11A and 11B are diagrams for explaining the Y histogram of the video signal and its transition. FIG. 11A shows an example of the Y histogram of the previous frame, and FIG. 11B shows the current histogram following FIG. FIG. 11C is a diagram showing an example of the Y histogram of a frame, and FIG. 11C is a diagram showing a frequency change portion by combining the histograms of the frames shown in FIGS. 110A and 11B. FIG. 12 is a block diagram showing a configuration example of the scene change detection unit 6 in the liquid crystal display device of FIG.

  Usually, a video scene is a segmented video based on a series of scene settings, for example, according to the intention of a video producer (screenwriter, director, etc.), and the brightness of the video signal is accompanied by a scene change (change in video content). The distribution is expected to change greatly. The scene change detection unit 6 uses this to detect a scene change. Specifically, the scene change detection unit 6 detects the presence / absence of a scene change from the histogram of the previous frame of the video signal and the degree of change in the current histogram. Although the scene change detection by the scene change detection unit 6 is described as being executed by a histogram change, for example, the APL detected by the APL detection unit 3 and the peak luminance value obtained at the time of histogram detection, etc. You may perform based on another feature-value (by the change of a feature-value).

  As illustrated in FIG. 12, the scene change detection unit 6 includes a histogram buffer 61 and a histogram change detection unit 62. The histogram buffer 61 stores histogram data of the previous frame. The histogram change detection unit 62 compares the histogram data of the current frame and the previous frame based on the output from the histogram stretching unit 4 and calculates the cumulative value of the frequency change. And the determination result is output.

  In the arrangement example of the first temporary filter 7 and the second temporary filter 9 as shown in FIG. 2 (temporary filter arrangement example 1), the scene change detection unit 6 converts the scene change detection result into the first temporary filter 7 and It is incorporated so as to output to the second temporary filter 9.

  In the case as shown in FIG. 11, the histogram buffer 61 stores the histogram data of FIG. The histogram change detection unit 62 compares the data in the histogram buffer 61 with the histogram data of the current frame (FIG. 11B), and detects the frequency change. The hatched portion in FIG. 11C is the frequency change portion. The histogram change detection unit 62 calculates the accumulated value of the frequency change portion, in other words, the area, and determines that a scene change has occurred if it is larger than a predetermined value. Then, the histogram change detection unit 62 outputs the determination result.

Next, the operation of the first temporary filter 7 will be specifically described.
FIG. 13 is a diagram showing a configuration example of the first temporary filter 7 in the liquid crystal display device of FIG. The first temporary filter 7, for example, cyclic a low-pass filter, as shown in FIG. 13, the value of the current frame n is inputted weighting factor 1-a (backlight DUTY) a multiplier for multiplying the X _n , A multiplier that multiplies the output value (backlight DUTY) Y _n-1 for the previous frame n-1 by the weighting coefficient a, and an adder that adds the outputs from these multipliers. Here, n is a natural number and a is a coefficient (filter coefficient) less than 1. When such a configuration of the first temporary filter 7 is expressed by an equation, the following equation (6) is obtained.
_{Y n = aY n-1 +} (1-a) X n ··· (6)

In the advanced luminance modulation processing executed by the advanced luminance modulation unit 20, the light emission luminance level of the backlight is dynamically changed. However, when the light emission luminance level of the backlight varies greatly in units of one frame, there may be a sense of incongruity. Therefore, a low-pass filter having a time constant of about 1 second is used as the first temporary filter 7 and the light emission luminance level BL _reduced (backlight DUTY) determined by the distortion module 5 is passed through the first temporary filter 7. As a result, the backlight luminance variation is smoothed over time, and the uncomfortable feeling is eliminated. In the temporary filter arrangement example 1, the first temporary filter 7 is incorporated so that the output of the distortion module 5 is temporally filtered and output to the configuration design unit 13 and the variable delay 10 in the subsequent stage.

In addition, when the scene changes, the video itself changes greatly, so that it is considered that there is little sense of incongruity even if the light emission luminance level of the backlight is suddenly changed. Therefore, for example, when the scene is changed, the change in backlight luminance is accelerated by reducing the coefficient a of the first temporary filter 7. Specifically, the coefficient a in the equation (6) is made sufficiently small only for the frame in which the scene change is detected, and the value of the coefficient a is restored from the next frame. By doing in this way, the value close to the input becomes the output of the first temporary filter 7, and the change in the light emission luminance level BL _reduced of the backlight is accelerated. Thus, it is preferable that the first temporary filter 7 changes the coefficient a depending on whether or not a scene change is detected by the scene change detection unit 6.

Next, the operation of the second temporary filter 9 will be specifically described.
The second temporary filter 9 illustrated in FIG. 2 will be described. In order to explain the effect more precisely, a liquid crystal display having a configuration excluding the second temporary filter 9 from FIG. 2 as shown in FIG. This will be described using the apparatus.

FIG. 14 is a diagram illustrating a partial configuration example of a conventional liquid crystal display device, and FIG. 15 is a diagram illustrating an example of changes in APL and histogram of a video signal. Further, FIG. 16 shows the reference emission luminance level BL _ref , emission luminance level BL _reduced , gain setting value, and value on the liquid crystal panel when the video signal change as shown in FIG. 15 occurs in the liquid crystal display device of FIG. It is a schematic diagram for demonstrating the change of the display brightness | luminance.

  In the liquid crystal display device having the configuration excluding the second temporary filter 9 as shown in FIG. 14, the APL changes rapidly from small to large as shown in FIG. 15, for example, and the determination result in the distortion module 5 is not affected. The case will be discussed with reference to FIG.

Assume that the APL changes rapidly from small to large as shown in FIG. 15, and the target reference luminance level BL _ref is changed from 100% to 50% as shown in FIG. Since it is assumed that the evaluation of the distortion module 5 does not change, 50% is output as it is as the light emission luminance level BL _reduced , and the temporal change is mitigated by the first temporary filter 7 as shown in FIG. The emitted luminance level BL _reduced (backlight DUTY) is output. However, since the gain is calculated based on not only the light emission luminance level BL _reduced but also the reference light emission luminance level BL _ref in the configuration design unit 13, the gain as shown by the solid line in the ellipse P in FIG. The set value changes rapidly. Therefore, the display brightness on the final liquid crystal panel changes suddenly as shown by the solid line in FIG. 16D, although it is desired to gradually change the display brightness as shown by the dotted line Q in FIG. Resulting in.

  In order to gradually change the display luminance as indicated by the dotted line Q, the gain setting value changes constantly as indicated by the dotted line in the ellipse P in FIG. Need to be output as follows.

The above problem can be solved by providing the second temporary filter 9. FIG. 17 shows a reference emission luminance level BL _ref , emission luminance level BL _reduced , and gain setting value when a change in the video signal as shown in FIG. 15 occurs in the liquid crystal display device of FIG. 2 (temporary filter arrangement example 1). FIG. 5 is a schematic diagram for explaining a change in display luminance on the liquid crystal panel.

  In the temporary filter arrangement example 1, the second temporary filter 9 temporally filters the output from the BL luminance level setting unit 8 based on the scene change detection result received from the scene change detection unit 6, and the configuration design unit 13 is arranged to output to 13. The second temporary filter 9 may be constituted by a filter such as the first temporary filter 7 of FIG.

By incorporating the second temporary filter 9 as described above, the reference emission luminance level BL _ref and the emission luminance level BL _reduced which are signals entering the configuration design unit 13 have the same time delay amount. It is possible to eliminate a sudden change in display luminance as described in 16 (D). In other words, the second temporary filter 9 is a filter having the same function and characteristics as the first temporary filter 7 (the time constant, the coefficient a, and the coefficient a are also changed), that is, at the time of a scene change. By following the change in the value of the first temporary filter 7, the gain setting value is kept constant as shown in the ellipse R in FIG. Can be set to As a result, as shown by the solid line S in FIG. 17D, a sudden change in display luminance can be eliminated. In other words, by providing the first temporary filter and the second temporary filter, the output delay amount of the light emission luminance level BL _reduced output from the distortion module 5 and the gain setting value output from the configuration design unit 13 Is correlated with the output delay amount.

In this way, the time constant of the second temporary filter 9 and the time constant of the first temporary filter 7 are made the same, and both frames to be filtered are combined, that is, the light emission luminance level BL used for the backlight luminance modulation. It is preferable to match the output time constants of _reduced and gain settings. In addition, it is preferable that the coefficient of the second temporary filter 9 and the coefficient a of the first temporary filter 7 are the same, and the weights of both current frames are matched. In addition, it is preferable that the second temporary filter 9 also changes the coefficient depending on whether or not a scene change is detected by the scene change detection unit 6 together with the change of the coefficient a in the first temporary filter 7.

  Further, even if the time constant and the coefficient a are not the same as those of the first temporary filter 7, a change having the same tendency as that of the coefficient a is added to the coefficient of the second temporary filter 9 based on the scene change detection result. Even if it is not possible to eliminate the sudden change in display luminance as described in (D), it is possible to mitigate it.

Further, the change of the coefficient a in the first and second temporary filters 7 and 9 has been described. However, the present invention is not limited to this example, and each temporary filter 7 and 9 is determined to be a scene change by the scene change detection unit 6. Only when the light emission luminance level BL _reduced (backlight DUTY) and the gain setting value are not delayed, and when it is determined that the scene change is not occurring, the light emission luminance level BL _reduced and the gain setting value output delay are _reduced. You may make it perform.

As described as the temporary filter arrangement example 1, in the present invention, (I) a light source luminance signal (light emission luminance level BL _reduced) output from a light source control unit configured by the BL luminance level setting unit 8 and the distortion module 5 and the like. That is, according to the output delay amount of the backlight DUTY), the gain setting value output from the gain setting unit configured by the configuration design unit 13 or the like is delayed and output, or (II) from the gain setting unit The light source luminance signal output from the light source control unit is delayed and output according to the output delay amount of the output gain setting value. In both configurations (I) and (II), one output delay amount is linked (temporally followed) to the other output delay amount, and the light source luminance signal output from the light source control unit The output delay amount correlates with the output delay amount of the gain setting value output from the gain setting unit. The delay here is as described above, and the delay for timing the video output at the video output unit 17 and the backlight dimming at the BL adjustment unit 12 executed by the variable delay 10 is as follows. Is another.

  As described above, according to the liquid crystal display device of the present invention, it is possible to improve the display quality by appropriately interlocking the change in luminance of the backlight and the gain setting of the input video signal.

The configurations (I) and (II) of the present invention are the first temporary filter 7 (on the light source control unit side) as described above as the temporary filter arrangement example 1 and as described later as the temporary filter arrangement examples 2 to 4. Filter) and the second temporary filter 9 (the filter on the gain setting unit side) can be realized, but the present invention is not limited to this. In the temporary filter arrangement example 1, the change of the time constant, the coefficient a, and the coefficient a are matched by the two temporary filters 7 and 9, so that the output delay amount of the backlight emission luminance level BL _{reduced and} the output delay amount of the gain setting value. These are only preferable examples.

The scene change detection unit 6 is not essential, and the backlight emission luminance level BL _{reduced can be reduced} only by arranging the first temporary filter 7 and the second temporary filter 9 as in the temporary filter arrangement example 1. It is possible to make the output delay amount and the output delay amount of the gain setting value the same. Further, the scene change detection unit 6 has been described as outputting the scene change detection result to the first temporary filter 7 and the second temporary filter 9. However, the scene change detection unit 6 may output the scene change detection result to the first temporary filter 7 or the second temporary filter 9, and the filter on the side receiving the detection signal may transmit the result to the other filter. However, if only one is relaxed, a configuration in which a scene change detection signal is output to one may be employed. Further, the present invention is not limited to detecting a scene change and reflecting the determination result in the temporary filter, and the temporary filter may be controlled based on other determination materials.

The above description has been based on the temporary filter arrangement example 1 shown in FIG. Hereinafter, another example of temporary filter arrangement will be described.
FIG. 18 is a partial block diagram showing another arrangement example (temporary filter arrangement example 2) of the temporary filter in the liquid crystal display device of FIG. The temporary filter arrangement example 2 described with reference to FIG. 18 differs from the temporary filter arrangement example 1 in that the arrangement of the second temporary filter 9 is different. The same applies to an application example in which the scene change detection unit 6 is not provided.

In the liquid crystal display device partially shown in FIG. 18, the same second temporary filter (reference numeral 9a) is provided at another position instead of the second temporary filter 9 in FIG. That is, in the temporary filter arrangement example 2, the second temporary filter 9a temporally filters the output from the BL luminance level setting unit 8 based on the scene change detection result received from the scene change detection unit 6, and configures the configuration. It is incorporated so as to output to the design unit 13 and the distortion module 5. That is, in the distortion module 5, the light emission corresponding to the video luminance range having the lowest evaluation value within the range not _exceeding the light emission luminance level BL _ref set by the BL luminance level setting unit 8 and relaxed by the second temporary filter 9. The brightness level BL _reduced is selected. In such a temporary filter arrangement example 2, for example, the reference emission luminance level BL _ref selected by the BL luminance level setting unit 8 is collectively set (input) to the distortion module 5 and the configuration design unit 13 by software processing. Used when used.

  In the temporary filter arrangement example 2, the scene change detection unit 6 outputs the scene change detection result obtained based on the output from the histogram stretching unit 4 to the first temporary filter 7 and the second temporary filter 9a. As described above, the first temporary filter 7 is incorporated so that the output of the distortion module 5 is temporally filtered and output to the configuration design unit 13 and the variable delay 10 in the subsequent stage.

In the temporary filter arrangement example 2, the application example related to the time constant in the temporary filter arrangement example 1 is not necessarily optimal. That is, in the temporary filter arrangement example 2, the first temporary filter 7 and the second temporary filter 9 may adopt the same time constant, but more preferably, the output delay amount of the second temporary filter 9a is set to be the same. By reducing the output delay amount of the first temporary filter 7 to about a fraction of the output delay amount, the output delay amount of the emission luminance level BL _reduced filtered in two places in total and the output delay amount of BL _ref filtered in one place May be combined as appropriate.

FIG. 19 shows the reference light emission luminance level BL _ref , light emission luminance level BL _reduced , gain setting value, and display on the liquid crystal panel when the video signal change as shown in FIG. 15 occurs in the liquid crystal display device of FIG. It is a schematic diagram for demonstrating the change of a brightness | luminance.

By incorporating such a second temporary filter 9a into the first temporary filter 7, the deviation between the output delay amount of the backlight emission luminance level BL _{reduced and} the output delay amount of the gain setting value can be reduced. As a result, the rapid change in display luminance as described with reference to FIG. That is, the second temporary filter 9a is a filter having functions and characteristics equivalent to those of the first temporary filter 7 (here, the coefficient a and its change are the same), that is, the first temporary filter 9a is changed at the time of a scene change. By following the change in the value of the filter 7, the gain setting value is not constant as shown in the ellipse U in FIG. It is possible to set so that the change is small (change is reduced) compared to. As a result, it is impossible to completely eliminate the sudden change as shown by the dotted line V in FIG. 19D, but as shown by the solid line in FIG. 19D, the sudden change in display luminance is a slight change. Can be relaxed. In other words, also in the temporary filter arrangement example 2, by providing the first temporary filter and the second temporary filter, the output delay amount of the light emission luminance level BL _reduced output from the distortion module 5, and the configuration design unit 13 is correlated with the output delay amount of the gain setting value output from 13.

  As described above, even in the liquid crystal display device shown in the temporary filter arrangement example 2, the display quality can be improved by appropriately interlocking the change in luminance of the backlight and the gain setting of the input video signal. Further, even if the coefficient a is not the same as that of the first temporary filter 7, a change in the same tendency as the coefficient a is applied to the coefficient of the second temporary filter 9 based on the scene change detection result, so that FIG. Although the rapid change in display luminance as described in (1) is not alleviated until indicated by the solid line in FIG. 19D, it can be moderated to a slight change.

In addition, the temporary filter arrangement example 2 in which a filter such as the second temporary filter 9a is provided at the input of the distortion module 5 can only be evaluated by the distortion module 5 by relaxing the change in the reference emission luminance level BL _ref. However, this is particularly useful when the distortion module 5 and the configuration design unit 13 are configured by software. That is, in the temporary filter arrangement example 2, the same reference light emission luminance level BL _ref (input DUTY) can be set collectively by software in the distortion module 5 and the configuration design unit 13, and the second temporary can be set only by the setting. Filtering can be applied to both by the filter 9a. Therefore, the configuration of the temporary filter arrangement example 2 can be designed more easily than the configuration of the temporary filter arrangement example 1 and the like.

Although the temporary filter arrangement example 2 has been described above, a temporary filter arrangement example 3 will be described below as still another temporary filter arrangement example.
FIG. 20 is a partial block diagram showing another arrangement example of the temporary filter in the liquid crystal display device of FIG. A temporary filter arrangement example 3 described with reference to FIG. 20 is the same as the temporary filter arrangement example 1 except that a third temporary filter 9b is provided, and the other parts are related to changes in time constants, coefficients, and coefficients. Application examples and application examples that do not include the scene change detection unit 6 are also applicable. However, the time constant, coefficient, and coefficient change referred to here are those of the first temporary filter 7 and the second temporary filter 9, and the time constant, coefficient, and coefficient of the third temporary filter 9b are changed. Basically irrelevant.

  In the liquid crystal display device of the temporary filter arrangement example 3 partially shown in FIG. 20, the third temporary filter 9b in the temporary filter arrangement example 1 is based on the scene change detection result received from the scene change detection unit 6. The output from the brightness level setting unit 8 is temporally filtered and output to the second temporary filter 9 and the distortion module 5. Further, the second temporary filter 9 temporally filters the output from the third temporary filter 9 b based on the scene change detection result received from the scene change detection unit 6 and outputs the result to the configuration design unit 13. Built in. Further, the scene change detection unit 6 outputs the scene change detection result obtained based on the output from the histogram stretching unit 4 to the first temporary filter 7 and the second temporary filter 9 so as to output the first temporary filter. The filter 7 is incorporated so that the output of the distortion module 5 is temporally filtered and output to the configuration design unit 13 and the variable delay 10 at the subsequent stage.

By incorporating the second temporary filter 9 as described above, the reference light emission luminance level BL _ref and the light emission luminance level BL _reduced which are signals entering the configuration design unit 13 are _input with the same delay. As shown in FIG. 16, it is possible to eliminate a sudden change in display luminance as described with reference to FIG. 16D (to avoid a malfunction caused by the first temporary filter 7 at the time of gain setting). Furthermore, in the temporary filter arrangement example 3, in the temporary filter arrangement example 1, the change in the reference light emission luminance level BL _ref can be relaxed and the evaluation by the distortion module 5 can be performed. In other words, also in the temporary filter arrangement example 3, by providing the first temporary filter, the second temporary filter, and the third temporary filter, the output delay amount of the emission luminance level BL _reduced output from the distortion module 5 can be _reduced. Therefore, the output delay amount of the gain setting value output from the configuration design unit 13 is correlated.

As illustrated here, in the present invention, the number of filters is not limited to two, and the output delay amount of the backlight emission luminance level BL _{reduced and} the output delay amount of the gain setting value are related (preferably the same). It can be configured as follows.

Although the temporary filter arrangement example 3 has been described above, a temporary filter arrangement example 4 will be described below as still another temporary filter arrangement example.
FIG. 21 is a partial block diagram showing another example of incorporating a temporary filter in the liquid crystal display device of FIG. The temporary filter arrangement example 4 described with reference to FIG. 21 is different from the temporary filter arrangement example 1 in the first temporary filter 7 (reference numeral 7a) and the second temporary filter 9 (reference numeral 9c). The arrangement is different, and the other parts are the same, including application examples relating to time constants, coefficients, and coefficient changes, and application examples that do not include the scene change detection unit 6.

  The liquid crystal display device of the temporary filter arrangement example 4 partially shown in FIG. 21 removes the first and second temporary filters 7 and 9 in the filter incorporation example 1, and the first temporary filter 7a is replaced with the distortion module 5. These outputs are time-filtered and output to the variable delay 10 at the subsequent stage. Further, the second temporary filter 9c temporally filters the gain setting value that is output from the configuration design unit 13 based on the scene change detection result received from the scene change detection unit 6, and performs RGBγ / WB adjustment. It is incorporated so as to output to the unit 15. Here, the scene change detection unit 6 is incorporated so as to output the scene change detection result obtained based on the output from the histogram stretching unit 4 to the first temporary filter 7a and the second temporary filter 9c. .

By adopting such a method of incorporating the first and second temporary filters 7a and 9c, the reference emission luminance level BL _ref and the emission luminance level BL _reduced which are signals entering the configuration design unit 13 are originally timed. Therefore, the gain setting value as described with reference to FIG. 16C does not change abruptly. The final display brightness on the liquid crystal panel is such that the first temporary filter 7a eliminates the uncomfortable feeling of backlight brightness fluctuation due to the presence or absence of scene change detection, but the second temporary filter 9c has a gain setting. Since filtering is performed later, a sudden change in display luminance as shown by the solid line in FIG. 16D is eliminated, and the display luminance is gradually increased as shown by the dotted line Q in FIG. 16D and the solid line S in FIG. Can be changed. In other words, also in the temporary filter arrangement example 4, by providing the first temporary filter and the second temporary filter, the output delay amount of the light emission luminance level BL _reduced output from the distortion module 5, and the configuration design unit 13 is correlated with the output delay amount of the gain setting value output from 13.

It is a graph which shows the relationship between an input gradation level (video signal level) and the luminance value on a liquid crystal panel about liquid crystal panels with CR of 3000 and 6000. It is a block diagram which shows the system configuration example of the liquid crystal display device which concerns on one Embodiment of this invention. It is a figure for demonstrating an example of the light emission luminance level selection process performed with the distortion module in the liquid crystal display device of FIG. FIG. 3 is a diagram for explaining a specific example of advanced luminance modulation processing in the liquid crystal display device of FIG. 2. It is a figure which shows the video-luminance range C in the case of the light emission luminance level 100% which is one of the selection objects. It is a figure which shows the image luminance range C when the light emission luminance level which is one of the selection objects is about 70%. It is a figure which shows the image luminance range C when the light emission luminance level which is one of the selection objects is about 50%. FIG. 3 is a diagram illustrating an example of a video signal gain set by an RGB γ / WB adjustment unit based on a gain setting signal output from an advanced luminance modulation unit in the liquid crystal display device of FIG. 2. It is a figure for demonstrating the example of an adjustment process in the RGBgamma / WB adjustment part in the liquid crystal display device of FIG. It is a figure for demonstrating the example of an adjustment process in the RGBgamma / WB adjustment part in the liquid crystal display device of FIG. It is a figure for demonstrating the Y histogram of a video signal, and its transition. It is a block diagram which shows the structural example of the scene change detection part in the liquid crystal display device of FIG. FIG. 3 is a diagram illustrating a configuration example of a first temporary filter in the liquid crystal display device of FIG. 2. It is a figure which shows the example of a partial structure of the conventional liquid crystal display device. It is a figure which shows the example of APL of a video signal, and the change of a histogram. When the change of the video signal as shown in FIG. 14 is generated in the liquid crystal display device of FIG. 13, the reference light emission luminance level BL _ref, light emission luminance level BL _Reduced, gain setting value, and the change in display luminance on liquid crystal panel It is a schematic diagram for demonstrating. When the change in the video signal as shown in FIG. 14 occurs in the liquid crystal display device of FIG. 2, the reference emission luminance level BL _ref , emission luminance level BL _reduced , gain setting value, and change in display luminance on the liquid crystal panel are shown. It is a schematic diagram for demonstrating. FIG. 3 is a partial block diagram illustrating another example of incorporating a temporary filter in the liquid crystal display device of FIG. 2. In the liquid crystal display device of FIG. 17, when the change of the video signal as shown in FIG. 14 occurs, the reference light emission luminance level BL _ref , the light emission luminance level BL _reduced , the gain setting value, and the change of the display luminance on the liquid crystal panel are shown. It is a schematic diagram for demonstrating. FIG. 3 is a partial block diagram illustrating another example of incorporating a temporary filter in the liquid crystal display device of FIG. 2. FIG. 3 is a partial block diagram illustrating another example of incorporating a temporary filter in the liquid crystal display device of FIG. 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Scaling part, 2 ... Y histogram detection part, 3 ... APL detection part, 4 ... Histogram stretching part, 5 ... Distortion module, 6 ... Scene change detection part, 7, 7a ... 1st temporary filter, 8 ... BL Brightness level setting unit, 9, 9a, 9c ... second temporary filter, 9b ... third temporary filter, 10 ... variable delay, 11 ... CPU / CPLD, 12 ... BL adjustment unit, 13 ... configuration design unit, 14 Image quality correction unit, 15 RGBRGB / WB adjustment unit, 16 FRC unit, 17 Video output unit, 20 Advanced luminance modulation unit, 61 Histogram buffer, 62 Histogram change detection unit.

Claims (5)

A liquid crystal panel that displays an image based on an input video signal; a light source that illuminates the liquid crystal panel; a light source control unit that adjusts the light emission luminance of the light source; and a gain setting unit that sets a gain of the input video signal; In a liquid crystal display device that controls the luminance of the light source and the gain setting in conjunction with each other,
The light source control unit delays and outputs a first temporary filter that outputs a light emission luminance signal and delays the light emission luminance signal output from the first temporary filter in accordance with the video output to the liquid crystal panel. And a delay unit that
The gain setting unit includes a second temporary filter that delays and outputs a signal for gain setting obtained from the input video signal ,
The liquid crystal display device, the first or the second of at temporary filter delays the signal for the gain setting and outputs according to the output delay amount of the light source luminance signal outputted from the temporary filter, or, the liquid crystal display apparatus characterized by delaying and outputting the light source luminance signal in the first temporary filter in accordance with the output delay amount of a signal for the gain setting that is output from the second temporary filter.   The liquid crystal display device according to claim 1, wherein the first temporary filter and the second temporary filter are filters having the same time constant.   A scene change detection unit configured to detect whether or not a scene change has occurred based on a feature quantity of the input video signal, and the first temporary filter and the first change filter according to whether or not a scene change is detected by the scene change detection unit; The liquid crystal display device according to claim 2, wherein a filter coefficient of the temporary filter of 2 is changed.   A scene change detection unit that detects whether or not a scene change has occurred based on a feature amount of the input video signal, and when the scene change detection unit determines that the scene change has occurred, the first temporary filter and the second The output delay in the first temporary filter and the second temporary filter is performed when it is determined that the scene change is not performed without performing the output delay in the second temporary filter. 2. A liquid crystal display device according to 2. Claims an output delay amount of said first signal for the gain setting of the output delay amount of the light source luminance signal to be outputted from the second temporary filter output from the temporary filter is characterized by correlation 2. A liquid crystal display device according to 1.

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