JP2013186207A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device which can perform OSD display in the same brightness constantly.SOLUTION: In a display control unit 1, according to the results of comparing the product of an average lighting rate obtained by an average lighting rate operation unit 11 and gradation of a video signal for OSD display after setting by a gradation setting unit 13 with the product of a target lighting rate obtained by a target lighting rate setting unit 10 and the gradation of the video signal for OSD display before setting by the gradation setting unit 13, the gradation of the video signal for OSD display is set.

Description

  The present invention relates to a liquid crystal display device that controls lighting of a backlight for each display area in accordance with an image.

  In recent years, for the purpose of reducing afterimages of moving images and improving contrast, an area active drive type liquid crystal display device that controls lighting of a backlight for each display area in accordance with video has been disclosed (for example, Patent Document 1).

  Further, in the area active drive type liquid crystal display device, when a portion of the image is bright, the excess power is used for the backlight of the bright portion by reducing the backlight according to the other dark portion. There is a liquid crystal display device that employs a high dynamic range (HDR) system that realizes brightness and high contrast.

  On the other hand, the liquid crystal display device is equipped with an on-screen display (OSD) function for displaying another image superimposed on a screen displaying video (for example, Patent Document 2).

JP 2010-249996 A (released on November 04, 2010) Japanese Patent Laying-Open No. 2005-321424 (published on November 17, 2005)

  By the way, in the above-mentioned HDR type liquid crystal display device, high brightness is realized by lighting a backlight corresponding to a place where the gradation of a pixel to be displayed is high.

  For this reason, unlike the OSD for time display or the like, when the image is darker than the OSD, the power is concentrated on the OSD portion and the OSD feels very dazzling for the user when the image is darker than the OSD. Occurs.

  The present invention has been made in view of the above-described problems, and in an HDR liquid crystal display device, an OSD display is always performed with the same brightness regardless of the brightness of an input video signal. An object of the present invention is to provide a liquid crystal display device capable of realizing an OSD display which is very easy for a panel observer.

The liquid crystal display device of the present invention is
A liquid crystal panel for performing video display based on display data generated from an input video signal;
A display control unit that superimposes another video on the video displayed on the liquid crystal panel and displays an OSD, and outputs an input video signal including information for display control of the liquid crystal panel;
A backlight capable of irradiating light from the back surface of the liquid crystal panel and adjusting the amount of irradiation light for each area obtained by dividing the display area of the liquid crystal panel,
An area active control unit that generates display data to be supplied to the liquid crystal panel and backlight control data to be supplied to the backlight from an input video signal output from the display control unit;
A backlight control unit that controls the light irradiation of the backlight for each of the divided areas according to the backlight control data generated by the area active control unit;
The display control unit
A target luminance setting unit for setting a target luminance of a backlight of an area for performing the OSD display from the gradation of the video signal for performing the OSD display;
A luminance calculation unit that reads the luminance of the OSD display area from the backlight control unit and obtains the luminance of the backlight of the OSD display area;
A luminance comparison unit that compares the luminance obtained by the luminance calculation unit with the target luminance set by the target luminance setting unit;
And a gradation setting unit for setting the gradation of the video signal for performing the OSD display in accordance with the comparison result by the luminance comparison unit.

  According to the above configuration, the luminance of the backlight in the area where the OSD display is obtained from the gradation of the video signal input to the liquid crystal panel is set to the brightness of the area where the OSD display is obtained from the gradation of the video signal which performs OSD display. By controlling so as to be close to the target luminance of the backlight, the luminance of the backlight in the region where the OSD display is performed can always be maintained at the same luminance.

  As a result, when the video signal input to the liquid crystal panel is darker than the video signal for performing OSD display, power is concentrated on the backlight in the area for performing the OSD display so that the luminance of the backlight is increased. Even in such a case, the luminance of the backlight can be lowered so as to approach the target luminance that is the original luminance of the backlight in the region where the OSD display is performed, thereby suppressing glare in the region where the OSD display is performed. be able to.

  On the other hand, when the video signal input to the liquid crystal panel is brighter than the video signal for performing OSD display, the power of the backlight in the area for performing the OSD display is reduced, so that the luminance of the backlight is lowered. Even in such a case, the luminance of the backlight can be increased so as to approach the target luminance that is the original luminance of the backlight in the region where the OSD display is performed, so that the darkness in the region where the OSD display is performed is reduced. Can be suppressed.

  Therefore, since the OSD display can always be performed with the same brightness regardless of the brightness of the input video signal, it is possible to realize the OSD display that is very easy for the observer of the liquid crystal panel.

The liquid crystal display device of the present invention is
A liquid crystal panel for performing video display based on display data generated from an input video signal;
A display control unit that superimposes another video on the video displayed on the liquid crystal panel and displays an OSD, and outputs an input video signal including information for display control of the liquid crystal panel;
A plurality of LEDs arranged two-dimensionally so as to correspond to the display screen of the liquid crystal panel, a backlight for irradiating the liquid crystal panel from the back,
An area active control unit that generates display data to be supplied to the liquid crystal panel and backlight control data to be supplied to the backlight from the video signal;
When each LED constituting the backlight is driven to be driven by a lighting drive control capable of changing the luminance of the LED, and the display screen of the liquid crystal panel is divided into a plurality of areas, the area active A backlight control unit for controlling the light irradiation of the backlight for each of the regions according to the backlight control data generated by the control unit,
The display control unit
A target lighting rate setting unit for setting a target lighting rate of a backlight in an area for performing the OSD display from the gradation of the video signal for performing the OSD display;
An average lighting rate calculation unit that reads the lighting rate of the OSD display area from the backlight control unit and obtains the average lighting rate of the LEDs in the OSD display area;
A gradation setting section for setting the gradation of the video signal for performing the OSD display;
The product of the average lighting rate obtained by the average lighting rate calculation unit and the gradation of the video signal for performing the OSD display after setting by the tone setting unit, and the target set by the target lighting rate setting unit A comparison unit that compares a product of the lighting rate and the gradation of the video signal for performing the OSD display before setting by the gradation setting unit;
The gradation setting unit is characterized in that the gradation of the video signal for performing the OSD display is set according to a comparison result by the comparison unit.

  Here, the gradation before setting by the gradation setting section refers to a gradation that has been input to the gradation setting section and has not yet been set. That is, the original gradation of the video signal for OSD display is shown. The gradation after setting by the gradation setting unit refers to a gradation in which the original gradation is set according to the comparison result by the comparison unit. That is, the gradation after the correction of the original gradation of the video signal for OSD display is shown.

  According to the above configuration, the backlight is composed of a plurality of LEDs arranged two-dimensionally, and each LED is driven to be lit by the lighting drive control capable of changing the luminance of the LED. The luminance of the OSD display area can be expressed using the rate.

  Here, when the LED lighting drive control is, for example, PWM (Pulse Width Modulation) control, the lighting rate can be rephrased as the LED duty ratio.

  The lighting drive control includes current control in addition to the PWM control. In the case of this current control, the duty ratio of PWM control is the amount of LED drive current.

The gradation setting unit
The product of the average lighting rate and the gradation of the video signal for performing OSD display after setting by the gradation setting unit indicates that the comparison result by the comparison unit is the OSD display before setting by the target lighting rate and gradation setting unit. If the product is larger than the product of the image signal gradation, the gradation of the image signal for OSD display is set to be lowered.
The product of the average lighting rate and the gradation of the video signal for performing OSD display after setting by the gradation setting unit indicates that the comparison result by the comparison unit is the OSD display before setting by the target lighting rate and gradation setting unit. When it is smaller than the product of the gradation of the video signal, the gradation of the video signal for performing OSD display is set to be increased.

  As described above, the product of the average lighting rate and the gradation of the video signal for performing the OSD display after setting by the gradation setting unit is the level of the video signal for performing the OSD display before the setting by the target lighting rate and the gradation setting unit. Even when the product is larger than the product of the tone, the product of the average lighting rate and the tone of the video signal for performing OSD display after setting by the tone setting unit is before the setting by the target lighting rate and the tone setting unit. Even if it is smaller than the product of the tone of the video signal that performs OSD display, it is always represented by the product of the average lighting rate and the tone of the video signal that performs OSD display after setting by the tone setting unit. The brightness to be approximated to the brightness represented by the product of the target lighting rate and the gradation of the video signal for performing OSD display before setting by the gradation setting unit.

  Therefore, since the OSD display can always be performed with the same brightness regardless of the brightness of the input video signal, it is possible to realize the OSD display that is very easy for the observer of the liquid crystal panel.

The liquid crystal display device of the present invention is
A liquid crystal panel for performing video display based on display data generated from an input video signal;
A display control unit that superimposes another video on the video displayed on the liquid crystal panel and displays an OSD, and outputs an input video signal including information for display control of the liquid crystal panel;
A plurality of LEDs arranged two-dimensionally so as to correspond to the display screen of the liquid crystal panel, a backlight for irradiating the liquid crystal panel from the back,
An area active control unit that generates display data to be supplied to the liquid crystal panel and backlight control data to be supplied to the backlight from the video signal;
When each LED constituting the backlight is driven to be driven by a lighting drive control capable of changing the luminance of the LED, and the display screen of the liquid crystal panel is divided into a plurality of areas, the area active A backlight control unit for controlling the light irradiation of the backlight for each of the regions according to the backlight control data generated by the control unit,
The display control unit
Obtained from the peak lighting rate of the LED in the OSD display area obtained by reading the lighting rate of the OSD display area from the backlight control unit and the maximum gradation value of the gradation of the video signal for performing the OSD display. The gradation of the video signal of the OSD display is corrected by the correction coefficient.

  According to the above configuration, the backlight is composed of a plurality of LEDs arranged two-dimensionally, and each LED is driven to be lit by the lighting drive control capable of changing the luminance of the LED. The luminance of the OSD display area can be expressed using the rate.

  In addition, the gradation of the video signal of the OSD display is corrected by the correction coefficient obtained from the peak lighting rate of the LED in the OSD display area and the maximum gradation value of the gradation of the video signal for OSD display. In addition, an average lighting rate calculation unit for obtaining the average lighting rate of LEDs in the OSD display area is not necessary.

  As a result, it is only necessary to compare the brightness of the LED peak positions. That is, the display control unit reads the lighting rate at the peak position of the gray level in the OSD display area from the backlight control unit, and L (peak gray level) × B (target lighting rate) and L (peak gray level) × α. (Correction coefficient) × B ′ (lighting rate at peak position) is compared, and α is determined according to the flow.

The backlight control unit
The total amount of drive current when the backlight LEDs are all lit up is the upper limit, and the total amount of LED drive currents that are lit in each region is within the range that does not exceed the total amount of drive current when all the LEDs are lit. It is preferable to increase the luminance at a constant magnification.

  In this way, the total amount of drive current when the backlight LEDs are fully lit is set as the upper limit, and the total amount of drive current of the LEDs that are lit in each region does not exceed the total amount of drive current at the time of full lighting. When the light emission luminance of the LED is increased at a constant magnification, that is, when the high dynamic range (HDR) method is adopted, normally, when the image is darker than the OSD, the power is concentrated on the OSD portion, and the OSD is very much for the user. By performing OSD display control as described above, the OSD display can always be performed with the same brightness regardless of whether the image is darker or brighter than the OSD, so that the user does not feel dazzling.

  In addition, when power is concentrated, luminance is suppressed, so that power consumption can be reduced.

The present invention relates to a liquid crystal panel that performs video display based on display data generated from an input video signal, and another video to the video displayed on the liquid crystal panel. Are superimposed on each other for OSD display, and a display control unit that outputs an input video signal including information for display control of the liquid crystal panel, and light is irradiated from the back of the liquid crystal panel, and irradiation is performed for each liquid crystal panel area. A backlight capable of adjusting the amount of light, an area active control unit for generating display data supplied to the liquid crystal panel and backlight control data supplied to the backlight from the video signal, and the area active Controls the light irradiation of the backlight for each of the divided areas according to the backlight control data generated by the control unit. A backlight control unit, and the display control unit sets a target luminance setting unit for setting a target luminance of a backlight of an area in which the OSD display is performed based on a gradation of the video signal in which the OSD display is performed. A luminance calculation unit that reads and calculates the luminance of the OSD display area from the light control unit, a luminance comparison unit that compares the luminance obtained by the luminance calculation unit with the target luminance set by the target luminance setting unit; And a gradation setting section for setting the gradation of the video signal for performing the OSD display in accordance with the comparison result by the luminance comparison section.

  According to the above configuration, the OSD display can always be performed with the same brightness regardless of the brightness of the input video signal, so that it is possible to realize an OSD display that is very easy for the observer of the liquid crystal panel to view. There is an effect.

It is a schematic block diagram of a liquid crystal display device according to an embodiment of the present invention. 3 is a flowchart showing a flow of OSD display control in the liquid crystal display device shown in FIG. 1. (A) is a figure which shows the lighting state of the conventional backlight, (b) is a figure which shows the lighting state of the backlight of this invention. It is a figure which shows the example of a general local dimming control, (a) shows the example of area | region division of a backlight, (b) is a figure which shows the luminance value in each area | region of the backlight by local deming. It is a figure which shows the luminance value in each area | region of the backlight by the high dynamic range (HDR) which is one of the control of local deming.

  In the area active drive type liquid crystal display device according to the present invention, when a portion of the image is bright, the remaining power is used for the backlight of the bright portion by restricting the backlight to the other dark portion. This invention is based on the premise that a high dynamic range (HDR) system that realizes high brightness and high contrast is used.

  In addition, as described above, the present invention can always perform OSD display at the same brightness regardless of the brightness of the input video signal, and thus realizes an OSD display that is very easy for a liquid crystal panel observer to see. In order to achieve this object, the luminance calculation unit obtains the luminance (target luminance) in the OSD display area from the input video signal, and further obtains the actual luminance in the OSD display area. The actual brightness is controlled to be close to the target brightness by using the brightness comparison unit.

  In the following first and second embodiments, an example using the lighting rate (target lighting rate and average lighting rate) of the LEDs constituting the backlight will be described as a specific example showing the luminance of the backlight. The details of the LED lighting rate will be described later.

[Embodiment 1]
Hereinafter, embodiments of the present invention will be described in detail.

<Outline of liquid crystal display device>
In this embodiment, a liquid crystal display device that controls the luminance of a backlight based on an input video signal, particularly a liquid crystal that divides a screen into a plurality of areas and controls the luminance of the backlight by an input signal in the area to drive it. An example in which the present invention is applied to a display device will be described.

  FIG. 1 is a schematic block diagram of the liquid crystal display device according to the present embodiment.

  As shown in FIG. 1, the liquid crystal display device includes a display control unit 1, an area active control unit 2, a panel control unit 3, an LCD panel (display panel) 4, an LED control unit (backlight control unit) 5, an LED backlight. A light 6 is provided.

  The LCD panel 4 is a liquid crystal panel in which (m × n) pixels are two-dimensionally arranged.

  Further, the display screen of the LCD panel 4 is divided into a plurality of, for example, (i × j) areas.

  The panel control unit 3 is a drive circuit for the LCD panel 4. The panel control unit 3 controls the light transmittance of the display element with respect to the LCD panel 4 based on display data (hereinafter referred to as LCD data) used for driving the LCD panel 4 output from the area active control unit 2. LCD control signal (voltage signal) to be output. The voltage output from the panel control unit 3 is written to a pixel electrode (not shown) in the display element, and the light transmittance of the display element changes according to the voltage written to the pixel electrode.

  The LED backlight 6 is provided on the back side of the LCD panel 4 and irradiates the back light of the LCD panel 4 with backlight light. Here, the LED backlight 6 uses two-dimensionally arranged LEDs as the light source, and each LED is a set of a predetermined number of LED units so as to correspond to a plurality of divided screens. Is forming.

  The LED control unit 5 is a drive circuit that drives each LED constituting the LCD panel 4 to be lit by PWM (Pulse Width Modulation) control. The LED control unit 5 determines the brightness of each LED with respect to the LED backlight 6 based on backlight control data (hereinafter referred to as LED data) used for driving the LED backlight 6 output from the area active control unit 2. LED control signal (voltage signal or current signal) for controlling

  In the present invention, the LED controller 5 does not limit the LED lighting drive control to PWM control, but may be current control, or may be LED driving control capable of changing the luminance of the LED. Any control may be used. In the current control, the duty ratio of PWM control is the amount of LED drive current.

  Here, as described above, the screen of the liquid crystal display device is divided into a plurality of, for example, (i × j) areas, and one LED unit is associated with one area.

  The area active control unit 2 calculates the luminance of the LED corresponding to the area based on the image in the area for each of (i × j) areas. The area active control unit 2 calculates the luminance of all LEDs included in the LED backlight 6 and outputs LED data (backlight control data) representing the calculated LED luminance to the LED control unit 5.

  The area active control unit 2 obtains the light transmittance of all the display elements included in the LCD panel 4 based on the input video signal generated by the display control unit 1, and the LCD data representing the obtained light transmittance. (Display data) is output to the panel control unit 3.

  An input video signal input to the area active control unit 2 is generated by the display control unit 1.

  The display control unit 1 generates information necessary for the LCD panel 4 and the LED backlight 6 from video data input from the outside, and outputs the generated information to the area active control unit 2 as an input video signal.

  When the OSD display is performed, the display control unit 1 adjusts the luminance of the LED corresponding to the OSD display area for displaying the OSD data based on the grayscale data included in the OSD data. Are included in the input video signal output to the area active control unit 2 and output.

<Local deming>
In the video display device having the above configuration, since the LED backlight 6 is used for illuminating the LCD panel 4, the LED backlight 6 is divided into a plurality of areas, and the video signal of the display area corresponding to each area is displayed. Thus, so-called local dimming is possible, in which the light emission of the LED is controlled for each region. According to this local ming, for example, it is possible to control such that a dark part in the screen of the image displayed on the LCD panel 4 suppresses light emission of the LED, and a bright part in the screen strongly emits the LED. Thereby, the power consumption of the backlight can be reduced and the contrast of the display screen can be improved.

  For example, FIG. 4 shows an example of general local dimming control. Here, the LED backlight is divided into eight areas, and the luminance of the LEDs is controlled according to the maximum gradation value of the video signal corresponding to each area. Assume that the maximum gradation value of the video signal in each region is in the state shown in FIG. A to H are region Nos. The number below is the maximum gradation value in each area.

For example, the luminance of the LED in each region by local dimming is as shown in FIG. That is, the brightness of the LED is controlled for each area according to the video signal of each area. Here, since the video is relatively dark in the region where the maximum gradation value of the video signal is low, the brightness of the LED is lowered to reduce the black float and improve the contrast, and the power consumption of the LED is reduced. Yes. In this case, the maximum luminance in each region is limited to the luminance (for example, 450 cd / m ² ) when all LEDs of the backlight are turned on with a duty of 100% (lighting rate: 100%).

  On the other hand, in the video display apparatus according to the present embodiment, a control method called a power limit, a so-called high dynamic range (HDR) method, is adopted as one method of local deming described above. The HDR method is intended to increase the brightness of the backlight and improve the contrast in an area where further brightness is required in the display screen of the LCD panel 4. Here, the upper limit is the total amount of drive current when the backlight LEDs are fully lit, and the total amount of drive current of the LEDs that are lit in each region is within the range that does not exceed the total amount of drive current when all the LEDs are lit. Is increased at a constant magnification.

That is, as shown in FIG. 5, the luminance is increased by multiplying the light emission luminance of the LED determined for each region in FIG. 4B by a fixed magnification (a times). The condition at this time is Σ (the driving current value of each region) <the total driving current value when all the LEDs are turned on. In this case, in one area, it is allowed to exceed the luminance at the time of full lighting (for example, 450 cd / m ² ), and more driving current is input to the LED in a range where there is a margin of power to make it brighter. It is. By performing such control, it is possible to actually express a peak luminance of 2 to 3 times.

  By the way, when the HDR method is adopted and OSD display is performed, the following problems occur.

  That is, the area active control unit 2 described above calculates LCD data and LED data for each divided area of the input video. At this time, the area active control unit 2 cannot distinguish between the OSD such as the time display displayed on the video by the display control unit 1 and the original video data input to the display control unit 1. As a result, when the input video is darker than the OSD, power is concentrated on the LED of the LED backlight 6 corresponding to the OSD display area, and the OSD becomes very dazzling.

  Specifically, as shown in the lower left of FIG. 3A, when the image is brighter than the OSD display area on the LCD panel 4, power is not concentrated on the LED 61 corresponding to the OSD display area 41, so that it is not too bright. . At this time, as shown in the lower right diagram of FIG. 3A, the lighting rates of the LEDs 61 constituting the LED backlight 6 are substantially equalized over the entire display screen.

  On the other hand, as shown in the upper left of FIG. 3A, when the image is darker than the OSD display area on the LCD panel 4, power is concentrated on the LED 61 corresponding to the OSD display area 41, and the OSD display area becomes brighter. Pass. At this time, as shown in the upper right diagram of FIG. 3A, the lighting rate of the LED 61 constituting the LED backlight 6 is high in the OSD display area 41.

  Therefore, when there is a possibility that the OSD becomes dazzling, the glare can be suppressed by lowering the gradation of the OSD.

  Specifically, as shown in the lower left of FIG. 3B, when the image is brighter than the OSD display area on the LCD panel 4, power is not concentrated on the LED 61 corresponding to the OSD display area 41, so that it is not too bright. . At this time, as shown in the lower right diagram of FIG. 3B, the lighting rates of the LEDs 61 constituting the LED backlight 6 are substantially equalized over the entire display screen.

  On the other hand, in the present invention, as shown in the upper left of FIG. 3B, when the image is darker than the OSD display area on the LCD panel 4, even if the power is concentrated on the LED 61 corresponding to the OSD display area 41, the OSD By controlling so that the gradation in the display area is lowered, the OSD display area is prevented from becoming too bright. At this time, as shown in the upper right diagram in FIG. 3A, the lighting rate of the LEDs 61 constituting the LED backlight 6 is controlled so as not to increase in the OSD display area 41.

  Such gradation control in the OSD display area is realized as follows.

<Configuration for OSD gradation control>
First, a configuration for OSD gradation control will be described.

  The OSD display control is performed using the display control unit 1 and the LED control unit 5.

  Therefore, in order to perform OSD display control, the display control unit 1 includes a target lighting rate setting unit 10, an average lighting rate calculation unit 11, a comparison unit 12, and a gradation setting unit 13, as shown in FIG. .

  The target lighting rate setting unit 10 sets the LED lighting rate (target lighting rate) of the LED backlight 6 in the region where the OSD display is performed from the gradation of the video signal that performs the OSD display, and the comparison unit 12. Output to.

  The average lighting rate calculation unit 11 obtains the average lighting rate of the LED in the OSD display area from the lighting rate of the LED corresponding to the OSD display area read from the LED control unit 5.

  The comparison unit 12 calculates the average lighting rate obtained by the average lighting rate calculation unit 11 and the gradation (L × α: α of the video signal for performing the OSD display after setting by the gradation setting unit 13 described later). Correction coefficient), the target lighting rate set by the target lighting rate setting unit 10, and the gradation (L) of the video signal for performing the OSD display before setting by the gradation setting unit 13 described later. Compare the product.

  Here, the gradation before setting by the gradation setting unit 13 refers to a gradation that has been input to the gradation setting unit 13 and has not yet been subjected to gradation setting. That is, the original gradation of the video signal for OSD display is shown. The gradation after setting by the gradation setting unit 13 is a gradation in which the original gradation is set according to the comparison result by the comparison unit 12. That is, the gradation after the correction of the original gradation of the video signal for OSD display is shown.

  The gradation setting unit 13 sets the gradation of the video signal for performing the OSD display according to the comparison result by the lighting rate comparison unit 12. The set gradation is output to the comparison unit 12 as the gradation of the video signal for performing OSD display after setting by the gradation setting unit 13.

  The gradation of the video signal for performing OSD display set by the gradation setting unit 13 in this way is included in the input video signal output from the display control unit 1.

  Here, since the LEDs constituting the LED backlight 6 are PWM controlled as described above, the lighting rate can be rephrased as a duty ratio.

  In other words, in the present embodiment, the average lighting rate calculation unit 11 of the display control unit 1 outputs the duty of each LED arranged corresponding to the OSD display area of the LED backlight 6 output from the LED control unit 5. From the ratio, an average duty ratio is obtained, and this is set as an average lighting rate and output to the comparison unit 12.

  The brightness of the OSD display area is determined by the gradation of the OSD display area and the lighting rate of the backlight of the OSD display area. That is, when the original gradation of OSD is L, the backlight lighting rate at that time is determined from the target brightness. Let this lighting rate be the target lighting rate B.

  When the input video is darker than the OSD, power concentrates on the LED of the LED backlight 6 in the OSD display area, and the average lighting rate B ′ in the OSD display area becomes larger than the above B, which makes it feel dazzling.

  Therefore, in the present embodiment, a correction coefficient α (0 <α ≦ 1) for adjusting the OSD gradation is set, the OSD gradation is set to L × α, and this α is controlled to control the OSD gradation. The gradation is adjusted to reduce glare.

<Flow of OSD display control processing>
Next, the flow of OSD display control processing will be described below.

  FIG. 2 is a flowchart showing the flow of OSD display control processing.

  First, the display control unit 1 determines whether there is OSD data (step S11).

  If it is determined that there is OSD data, the display control unit 1 obtains the OSD display gradation L based on the OSD data, and achieves the target brightness in the OSD display area. The lighting rate B is obtained. The brightness in the OSD display area is represented by the product of the OSD display gradation L and the target lighting rate B, that is, L × B. Note that the initial value of α is 1.

  Next, the display controller 1 obtains the average lighting rate B ′ of the LEDs in the OSD display area (step S12). Here, the average lighting rate B ′ of the backlight that achieves actual brightness in the OSD display area is obtained. The actual brightness in the OSD display area is represented by L × α × B ′ (where α is a correction coefficient and a value in a range of 0 <α ≦ 1).

  In the display control unit 1, L × α × B ′ (the initial value of α is 1) indicating the actual brightness in the OSD display area and L × B indicating the target brightness in the OSD display area. It is determined whether it is larger (step S13).

  If it is determined in step S13 that L × α × B ′> L × B, the OSD display area is brighter (feels dazzling) than the original brightness, so the process proceeds to step S14 and the correction coefficient α And the OSD gradation (L × α) is lowered. Here, the correction coefficient α is reduced by about 1% in the case of 256 gradations. However, the degree of decrease due to the correction coefficient α is not limited to this.

  Subsequently, it is determined whether or not the reduced correction coefficient α is smaller than a minimum value αmin (for example, 0.1) (step S15). If α is smaller than the minimum value αmin, α is reset to αmin (step S16). If α is not smaller than the minimum value αmin, the process proceeds to step S20.

  On the other hand, when it is determined in step S13 that L × α × B ′> L × B is not satisfied, the OSD display area is the same as or darker than the original brightness, and the process proceeds to step S17. The correction coefficient α is increased to increase the OSD gradation (L × α).

  Subsequently, it is determined whether or not the increased correction coefficient α is larger than the maximum value 1 (step S18). If α is larger than 1, α is reset to 1 (step S19). If α is not larger than 1, the process proceeds to step S20.

  In step S20, the OSD gradation is newly set as L × α using the newly set correction coefficient α.

  Subsequently, the area active control unit 2 recalculates the backlight lighting rate of the OSD display area based on the OSD gradation L × α (step S21).

  Then, after the backlight lighting rate is recalculated in step S21, the process proceeds to step S12 again, and the average lighting rate B ′ in the OSD display area displayed based on the new backlight lighting rate is obtained. , Steps S13 to S21 are repeated.

  As described above, when the OSD gradation changes, the backlight lighting rate of the OSD display area also changes, and the brightness of the OSD is always constant. As a result, it is possible to prevent the OSD from becoming bright and to prevent the OSD from becoming too dark.

  Therefore, according to the liquid crystal display device having the above-described configuration, the OSD display can always be performed with the same brightness regardless of the brightness of the input video signal. There is an effect that it can be realized.

  Further, in the case of a liquid crystal display device adopting the HDR method as in the present embodiment, as described above, when the input video is darker than the OSD display area, unnecessary power is concentrated on the LEDs in the OSD display area. Therefore, power consumption can be reduced.

  In this embodiment, the example in which the brightness in the OSD display area is controlled by comparing the target lighting rate with the average lighting rate has been described. However, the present invention is not limited to this.

  For example, when the brightness of the OSD display area is controlled, if there is at least one LED having a lighting rate (peak lighting rate) exceeding the target lighting rate among a plurality of LEDs in the OSD display area, the OSD display area is dazzling. Therefore, it is conceivable to change the gradation so as to lower the lighting rate of the plurality of LEDs in the OSD display area.

  In the following second embodiment, an example of performing OSD gradation control using the peak lighting rate will be described.

[Embodiment 2]
In this embodiment, a liquid crystal display device that controls the luminance of a backlight based on an input video signal, particularly a liquid crystal that divides a screen into a plurality of areas and controls the luminance of the backlight by an input signal in the area to drive it. An example in which the present invention is applied to a display device will be described.

  Note that the configuration of the video display device according to the present embodiment is almost the same as the configuration of the video display device according to the first embodiment (FIG. 1), and thus detailed description thereof is omitted.

  In the present embodiment, the HDR method is adopted as in the first embodiment. In this HDR system, the LED is lit at the peak lighting rate at the highest OSD gradation.

  Therefore, the correction coefficient α is obtained from the highest OSD gradation and the LED peak lighting rate at that time, and all the gradations of the OSD are corrected with the correction coefficient α. The same effect as when the average lighting rate is used can be obtained.

  Specifically, the correction coefficient α is obtained from the highest gradation of the video signal for OSD display in the display control unit 1 and the lighting rate of the LED corresponding to the OSD display area read from the LED control unit 5. It is determined by the peak lighting rate of the LED.

  According to the above configuration, the same effect as in the first embodiment is obtained, but further obtained from the peak lighting rate of the LED in the OSD display area and the maximum gradation value of the gradation of the video signal for performing OSD display. Since the gradation of the video signal of the OSD display is corrected by the correction coefficient, an average lighting rate calculation unit for obtaining the average lighting rate of the LED in the OSD display area becomes unnecessary. As a result, the circuit configuration for performing OSD display control can be simplified.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  INDUSTRIAL APPLICABILITY The present invention can be used for a liquid crystal display device that controls lighting of a backlight for each display area according to an image.

DESCRIPTION OF SYMBOLS 1 Display control part 2 Area active control part 3 Panel control part 4 LCD panel (liquid crystal panel)
5 LED controller (backlight controller)
6 LED backlight (backlight)
10 Target lighting rate setting part (target brightness setting part)
11 Average lighting rate calculation section (average brightness setting section)
12 Lighting rate comparison part (luminance comparison part)
13 Gradation setting part (gradation setting part)
41 OSD display area 61 LED

Claims (5)

A liquid crystal panel for performing video display based on display data generated from an input video signal;
A display control unit that superimposes another video on the video displayed on the liquid crystal panel and displays an OSD, and outputs an input video signal including information for display control of the liquid crystal panel;
A backlight capable of irradiating light from the back surface of the liquid crystal panel and adjusting the amount of irradiation light for each area obtained by dividing the display area of the liquid crystal panel,
An area active control unit that generates display data to be supplied to the liquid crystal panel and backlight control data to be supplied to the backlight from an input video signal output from the display control unit;
A backlight control unit that controls the light irradiation of the backlight for each of the divided areas according to the backlight control data generated by the area active control unit;
The display control unit
A target luminance setting unit for setting a target luminance of a backlight of an area for performing the OSD display from the gradation of the video signal for performing the OSD display;
A luminance calculation unit that reads the luminance of the OSD display area from the backlight control unit and obtains the luminance of the backlight of the OSD display area;
A luminance comparison unit that compares the luminance obtained by the luminance calculation unit with the target luminance set by the target luminance setting unit;
A liquid crystal display device comprising: a gradation setting unit configured to set a gradation of a video signal for performing the OSD display according to a comparison result by the luminance comparison unit. A liquid crystal panel for performing video display based on display data generated from an input video signal;
A display control unit that superimposes another video on the video displayed on the liquid crystal panel and displays an OSD, and outputs an input video signal including information for display control of the liquid crystal panel;
A plurality of LEDs arranged two-dimensionally so as to correspond to the display screen of the liquid crystal panel, a backlight for irradiating the liquid crystal panel from the back,
An area active control unit that generates display data to be supplied to the liquid crystal panel and backlight control data to be supplied to the backlight from the video signal;
When each LED constituting the backlight is driven to be driven by a lighting drive control capable of changing the luminance of the LED, and the display screen of the liquid crystal panel is divided into a plurality of areas, the area active A backlight control unit for controlling the light irradiation of the backlight for each of the regions according to the backlight control data generated by the control unit,
The display control unit
A target lighting rate setting unit for setting a target lighting rate of a backlight in an area for performing the OSD display from the gradation of the video signal for performing the OSD display;
An average lighting rate calculation unit that reads the lighting rate of the OSD display area from the backlight control unit and obtains the average lighting rate of the LEDs in the OSD display area;
A gradation setting section for setting the gradation of the video signal for performing the OSD display;
The product of the average lighting rate obtained by the average lighting rate calculation unit and the gradation of the video signal for performing the OSD display after setting by the tone setting unit, and the target set by the target lighting rate setting unit A comparison unit that compares a product of the lighting rate and the gradation of the video signal for performing the OSD display before setting by the gradation setting unit;
The liquid crystal display device, wherein the gradation setting unit sets a gradation of a video signal for performing the OSD display in accordance with a comparison result by the comparison unit. The gradation setting unit
The product of the average lighting rate and the gradation of the video signal for performing OSD display after setting by the gradation setting unit indicates that the comparison result by the comparison unit is the OSD display before setting by the target lighting rate and gradation setting unit. If the product is larger than the product of the image signal gradation, the gradation of the image signal for OSD display is set to be lowered.
The product of the average lighting rate and the gradation of the video signal for performing OSD display after setting by the gradation setting unit indicates that the comparison result by the comparison unit is the OSD display before setting by the target lighting rate and gradation setting unit. 3. The liquid crystal display device according to claim 2, wherein when the image signal is smaller than a product of the gradation of the video signal, the gradation of the video signal for performing OSD display is set to be increased. A liquid crystal panel for performing video display based on display data generated from an input video signal;
A display control unit that superimposes another video on the video displayed on the liquid crystal panel and displays an OSD, and outputs an input video signal including information for display control of the liquid crystal panel;
A plurality of LEDs arranged two-dimensionally so as to correspond to the display screen of the liquid crystal panel, a backlight for irradiating the liquid crystal panel from the back,
An area active control unit that generates display data to be supplied to the liquid crystal panel and backlight control data to be supplied to the backlight from the video signal;
When each LED constituting the backlight is driven to be driven by a lighting drive control capable of changing the luminance of the LED, and the display screen of the liquid crystal panel is divided into a plurality of areas, the area active A backlight control unit for controlling the light irradiation of the backlight for each of the regions according to the backlight control data generated by the control unit,
The display control unit
Obtained from the peak lighting rate of the LED in the OSD display area obtained by reading the lighting rate of the OSD display area from the backlight control unit and the maximum gradation value of the gradation of the video signal for performing the OSD display. A liquid crystal display device, wherein the gradation of the OSD display area is corrected by the correction coefficient. The backlight control unit
The total amount of drive current when the backlight LEDs are all lit up is the upper limit, and the total amount of LED drive currents that are lit in each region is within the range that does not exceed the total amount of drive current when all the LEDs are lit. The liquid crystal display device according to claim 2, wherein the luminance is increased at a constant magnification.

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