JP2007049693A - Liquid crystal display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display apparatus capable of obtaining suitable screen display luminance corresponding to a video image content and sufficiently reduce power consumption. <P>SOLUTION: The liquid crystal display apparatus is provided with a liquid crystal panel for displaying a video image, and a light source for illuminating the liquid crystal panel. The emission luminance control characteristic of the light source is changed depending on the genre of the video image displayed on the liquid crystal panel. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technique for performing appropriate video display according to the content of a video to be displayed.

  Up to now, a device has been devised to optimize the image quality by performing various controls based on the video feature amount of the input video signal. For example, an average luminance level (Average Picture Level, hereinafter referred to as “APL”) in one frame of the input video signal is calculated, and the screen luminance is adjusted according to the APL, or the luminance of the pixel in one frame of the input video signal Among the levels, those that adjust the screen brightness based on the maximum brightness level and the minimum brightness level, and those that perform screen brightness adjustment and gamma correction by analyzing the histogram of the brightness level of the input video signal, etc. Exists.

  For example, in Patent Document 1, the brightness of a backlight unit used in a liquid crystal display device or the like is controlled so as to increase the brightness when displaying an image with a relatively dark gradation, and an image with a relatively light tone is displayed. A backlight unit is described in which when the display is displayed, the brightness is controlled to be dark so that the screen is easy to see and the power consumption is reduced.

  Patent Document 2 realizes high brightness and high contrast by increasing the brightness of a light source when detecting that a video signal applied to a liquid crystal panel includes a white peak signal of a predetermined value or more. However, a liquid crystal display device that has low power consumption is described.

  In Patent Document 3, the area occupancy for each luminance level of one field or one frame of the input video signal is obtained, and the contrast of the video signal and the luminance of the backlight are individually controlled independently, thereby obtaining the dynamic range of the video. A liquid crystal display device that expands and reduces power consumption is described.

  However, the conventional methods as described above only adjust the screen brightness according to the feature amount of each frame of the video signal, and the content of the video to be displayed (movie, sports, news, animation, Appropriate screen brightness, contrast, and sharpness according to the type of video, such as variety, can not be obtained sufficiently, and power consumption has not been sufficiently reduced. Therefore, a plurality of video display modes such as a dynamic mode, a standard (standard) mode, a cinema (movie) mode, and a low power consumption mode are provided in advance in the display device, so that the content type of the video to be displayed, the viewing environment, etc. Accordingly, the user needs to adjust the video signal processing and the light emission luminance of the backlight by selecting an appropriate video display mode.

  Therefore, Patent Literature 4 describes a television system that enhances interest by changing the luminance of a video to be displayed according to the type of video content. A television system described in Patent Document 4 will be described with reference to FIG.

  The television system includes a television receiver 211, a luminance control device 212, and a remote controller 213. The television receiver 211 and the luminance control device 212 are connected to an antenna 214 that can receive digital broadcast radio waves.

  Programs broadcast by this digital broadcast are classified into subdivided genres such as Western, Japanese, and sports. Is attached.

  When a certain channel is selected by the remote control operation, the luminance change control circuit 2122 uses the genre extracted by the tuner 2121 and the genre-mode correspondence table stored in the storage device 2123 (FIG. 21B). )), A control signal indicating that the luminance processing corresponding to the genre is added is output to the television receiver 211. In response to this, the control circuit 2112 of the television receiver 211 outputs an instruction signal to the display control circuit 2113 so as to instruct adjustment of the luminance of the video displayed on the display 2114 in accordance with this control signal.

  For example, when the extracted genre is “foreign movie (action)”, the luminance of the video displayed on the display 2114 is reduced according to the cinema 1 mode process in order to give a sense of presence like being in a movie theater, for example. If the extracted genre is “sports (baseball)”, the display 2114 is displayed according to the sports 1 mode process to give a sense of presence like being in a baseball field, for example. Brightness processing is performed to increase the brightness of the video. In this case, it is possible to output video that has been subjected to optimal processing for both action movies and baseball broadcasts.

  In the patent document 4, the predetermined luminance process is, for example, a process for reducing the luminance by a certain ratio, a process for increasing the sense of presence, and changing the luminance to give a powerful impression. That is, the display luminance of the video is changed by multiplying the input video signal level by a predetermined coefficient to increase or decrease the display luminance, or by giving the input video signal a predetermined curve.

  Next, a digital television broadcast receiver similar to the television system described in Patent Document 4 is described in Patent Document 5. The digital television broadcast receiver described in Patent Document 5 will be described with reference to FIG.

  A digital television broadcast receiver described in Patent Document 5 includes an antenna 221, a tuner 222, a demultiplexing circuit 223, a video signal generation unit 224, a display device 225, a speaker 226, a CPU 227, an operation unit 228, and a storage device 229 (RAM and ROM). ). In addition to a table necessary for generating program guide information and program guide data, the RAM stores a genre-specific adjustment table as shown in FIG. The genre adjustment table includes a genre code representing the genre to be adjusted, a luminance adjustment amount and a volume adjustment amount for the genre, and the contents of the genre adjustment table are set based on a setting operation by the user.

  In the example of FIG. 22B, for a movie genre that is viewed for a relatively long time, in order to reduce eye fatigue, data indicating that the brightness is reduced by 10% (−10% is used). Data) is set as the luminance adjustment amount. For the news genre, data indicating that the volume is increased by 10% (data indicating + 10%) is set as the volume adjustment amount. For music genres, data indicating that the volume is reduced by 10% (data indicating -10%) is set as the volume adjustment amount. Furthermore, for an adult genre, data indicating that the volume is reduced by 40% (data indicating -40%) is set as the volume adjustment amount.

  Thereby, output video characteristics (for example, luminance) and output audio characteristics can be set according to the user's preference for each genre, and when the viewing channel is changed, the code of the program broadcast on the changed channel is acquired, When the output video characteristics and output audio characteristics for the acquired code are set, the adjustment according to the set output video characteristics and output audio characteristics is automatically performed when the changed program is output. Done.

  As described above, in Patent Document 5, the display luminance of the video is changed by processing such as increasing and decreasing the luminance of the input video signal uniformly by 10%.

For reference, Patent Document 6 discloses that when the content type of the display video is a content (for example, a movie) that should have an awakening effect, the luminance of a light source having a dominant wavelength between 445 nm and 480 nm of the backlight is increased. A display device that is controlled to perform is described.
JP-A-6-34946 Japanese Patent Laid-Open No. 62-19835 Japanese Patent Laid-Open No. 2002-14660 JP 2001-111916 A Japanese Patent Laid-Open No. 10-322622 International Publication No. 2004/088616 Pamphlet

  As described in Patent Documents 4 and 5, it is very useful to display an image by setting an appropriate screen brightness for each content type of the image to be displayed.

  However, as disclosed in Patent Documents 4 and 5, when the input video signal (luminance signal) is subjected to a predetermined process, the subtle gradation expression is affected.

  This will be described using a simple example with reference to FIG. 23. When the gradation of the input video signal is output as it is, the gradation conversion characteristic is a straight line such as A. That is, the number of gradations that can be expressed by the input video signal is the same as the number of gradations that can be expressed by the output video signal.

  However, if the luminance processing described in Patent Documents 4 and 5 is performed, for example, when the luminance of the input video signal is converted to 50%, the gradation conversion characteristic is a straight line such as C. Become. That is, when the number of gradations that can be expressed in the input video signal is 256 gradations (8 bits), the number of gradations that can be expressed in the output video signal is half of 128 gradations (equivalent to 7 bits), and the pseudo contour is This will reduce the quality of the displayed image.

  In this, while adjusting to the appropriate display brightness according to the content type, the number of display gradations decreases, and the subtle shade expression expressed in the input video signal is lost when displaying the video, The objective of optimal video display cannot be achieved sufficiently.

  In addition, the power consumption of large-screen liquid crystal display devices is largely occupied by the power consumption of the backlight unit, which also reduces unnecessary power consumption of the backlight unit from the viewpoint of reducing environmental impact. It is hoped to do. However, even if the display luminance is adjusted by applying predetermined processing to the input video signal (luminance signal) as in Patent Documents 4 and 5, the effect of reducing power consumption cannot be expected. .

  The present invention has been made in view of the above problems, and achieves an optimal video expression according to the content type of the video to be displayed and a sufficient reduction in power consumption without degrading the display quality. It is an object of the present invention to provide a liquid crystal display device.

  A first invention of the present application is a liquid crystal display device that includes a liquid crystal panel that displays an image and a light source that illuminates the liquid crystal panel, and variably controls the light emission luminance of the light source based on a feature amount of an input video signal. Genre detection means for detecting genre information superimposed on the input video signal is provided, and the light source emits light based on the feature quantity of the input video signal according to the genre information detected by the genre detection means. It is characterized in that a luminance control characteristic for variably controlling the luminance is changed.

  According to a second aspect of the present invention, there is a characteristic change point in which the change in the luminance control characteristic changes a slope indicating a luminance control characteristic for variably controlling the light emission luminance of the light source based on a feature amount of the input video signal. It is characterized by being changed.

  According to a third aspect of the present invention, an approximate characteristic indicating an intersection when a luminance control characteristic for variably controlling the light emission luminance of the light source based on a feature amount of the input video signal is approximated by a straight line by changing the luminance control characteristic. The change point is changed.

  According to a fourth aspect of the present invention, the difference between the maximum value and the minimum value of the light emission luminance of the light source is changed by changing the luminance control characteristic.

  The fifth invention of the present application is characterized in that the input video signal is expanded and contracted and the luminance control characteristic is changed.

  A sixth invention of the present application is characterized by correcting the gradation characteristic of the input video signal and changing the luminance control characteristic.

  The seventh invention of the present application is characterized by changing the gradation control characteristic for the input video signal and changing the luminance control characteristic.

  The eighth invention of the present application is characterized in that the emission luminance of the light source is controlled based on a lookup table selected according to genre information detected by the genre detection means.

  A ninth invention of the present application is characterized in that the emission luminance of the light source is controlled based on an arithmetic expression selected according to genre information detected by the genre detection means.

  A tenth invention of the present application is characterized in that the arithmetic expression is a function for obtaining a light emission luminance of the light source based on a feature amount of the input video signal.

  An eleventh aspect of the present invention is characterized in that the feature quantity of the input video signal is an average luminance level of the input video signal.

  According to the present invention, appropriate video display can be performed for each video content type, and power consumption can be effectively reduced.

  A display device according to the present embodiment will be described with reference to FIG. The display device according to the present embodiment includes a genre information detection unit 13 that detects genre information from electronic program information demultiplexed by the decoder 12 from an input broadcast signal and the like, and a predetermined video signal demultiplexed by the decoder 12. An image adjustment unit 15 that performs the image processing of the LCD, and an LCD that outputs a liquid crystal drive signal to a gate driver and a source driver (not shown) of the liquid crystal panel (image display unit) 16 based on the image signal output from the image adjustment unit 15 The controller 17 includes a light source control unit 18 that controls increase / decrease in light emission luminance of a light source (not shown) that irradiates the liquid crystal panel 16 from the back side. Further, the control unit 14 adjusts the light emission luminance of the light source suitable for the genre of the display video based on the feature amount of the video signal decoded by the decoder 12 and the genre information detected by the genre information detection unit 13. Then, a control signal is given to the light source controller 18.

  In the block diagram shown in FIG. 1, the feature amount of the input video signal is detected before the video adjustment by the video adjustment unit 15, but this adjustment may be performed after the video adjustment. However, the video adjustment unit 15 may perform, for example, an OSD display process, a scaling process, or a letterbox display (screen area restriction by a black mask or the like) process. If detection is performed before the video adjustment by the video adjustment unit 15, the luminance of the light source corresponding to the true video signal can be adjusted without being affected by these, so it is preferable to perform the detection before the various video adjustments.

  As shown in FIG. 2, the light source that irradiates the liquid crystal panel 16 is arranged in a backlight device attached to the back surface of the liquid crystal panel 16 with white fluorescent tubes 21 having a thin tube shape arranged at equal intervals. Alternatively, as shown in FIG. 3, a plurality of color LED light sources (in FIG. 3, a red light source 31, a green light source 32, and a blue light source 33) are laid out in the backlight device. Has been. Although not shown, the liquid crystal panel 16 may be irradiated by using a so-called side edge type backlight device in which light from the light source is made uniform by using a light guide plate.

  As described above, in the display device including the fluorescent tube 21 and the LEDs 31 to 33 as the backlight light source, the emission luminance of the fluorescent tube is controlled based on the genre information, or the mixed color of the three primary colors is not significantly affected. Appropriate display brightness is realized by controlling the light emission brightness of each LED. That is, the increase / decrease of the substantially white light amount that irradiates the light modulation element such as liquid crystal is controlled (the emission luminance is increased / decreased while keeping the chromaticity substantially constant).

  Genre information, for example, is included as a genre code in a part of electronic program information (hereinafter referred to as “EPG information”) transmitted by being superimposed on a broadcast signal of terrestrial digital broadcasting, BS, or CS digital broadcasting.

  The broadcast signal is received by the tuner 11-2 and decoded by the decoder 12. A genre code is extracted from the broadcast signal as genre information by the genre information detection unit 13. The genre information is not limited to the case where the genre information is separated / acquired from the broadcast signal selected by the tuner 11-2. For example, an external device (such as a DVD player or a Blu-ray disc player) is connected to the display device, When displaying video information that is played back on a device and input to a display device, a genre information detection unit displays a flag (for example, an identification code indicating “movie”) that indicates content contents added in a media medium such as a DVD. 13 can be detected.

  The broadcast signal is not limited to digital broadcast, and content information can be acquired even with analog broadcast. For example, ADAMS-EPG is EPG information transmitted by being superimposed on an analog broadcast.

  In addition to the case where the genre information is input simultaneously with the input video signal, the genre information may be input as sub-information different from the video signal. In this case, even when the video signal and the genre information are input separately, the video information that the genre information indicates is associated and input. For example, XMLTV is an application for automatically acquiring a TV program guide published on the Web, converting it to XML, and outputting it, and using this, acquires genre information of a video to be displayed on the network. You can also.

  As shown in FIG. 4, the genre code as genre information is “news / report”, “sports”, “information / wide show”, “drama”, “music”, “variety” in the digital terrestrial broadcasting standard. , “Movie”, “Animation / Special Effects”, “Documentary / Liberal Arts”, “Drama / Performance”, “Hobbies / Education”, “Others” are categorized in advance as major categories, and more than one for each major category. The middle classification is defined. For example, the major categories of “sports” are “sports news”, “baseball”, “soccer”, “golf”, “other ball games”, “sumo / martial arts”, “olympic / international competitions”, “marathon / “Land and swimming”, “Motor sports”, “Marine winter sports”, “Horse racing / public sports”, and “Others” are defined as medium categories.

  The display device according to the present embodiment discriminates a genre corresponding to the video to be displayed, and controls the light emission luminance of the light source so as to realize screen luminance, contrast, sharpness, and the like appropriate for the discriminated genre.

  For controlling the light emission luminance of the light source, a plurality of luminance control tables (look-up tables) for each genre are stored in a storage device such as a ROM, and this is switched and selected based on the genre information detected by the genre detection unit 13. Then, the driving of the light source is controlled according to the luminance control characteristic of the luminance control table. The luminance control table shows the relationship of how to set the light emission luminance of the light source according to the video feature amount of the input video signal.

  In order to optimally display the video to be displayed on the video display unit 16, the light emission luminance of the light source is controlled according to the luminance control table corresponding to the genre. In the following, the case where the genre information is a genre code superimposed on a digital terrestrial broadcast signal and the video feature amount is APL will be described as an example.

  First, digital terrestrial broadcasting on the same channel for a certain period of time (about a week) to verify how “appropriate” it is to control the brightness of the light source for “video to be displayed” The work of investigating the distribution of the frequency of APL of the video signal received by genre was performed.

  FIG. 5 shows excerpts of the results of the above survey for several genres. FIG. 5A is a histogram showing the APL frequency (time) of a video signal whose genre code is “news / report” when a broadcast signal is received for a certain period on the same channel. is there. The horizontal axis represents the APL of the input video signal as the video feature amount, the vertical axis represents the frequency of appearance of the APL of the input video signal in time (minutes), and the total average of the luminance levels of the input video signal of the genre is also displayed simultaneously. is doing.

  Similarly, in FIGS. 5B and 5C, the APL frequency of the input video signal when the genre code of the video signal to be displayed is broadly classified as “movie” or “animation / special effects” is shown as a histogram. Show.

  5D and 5E show the input video signal when the genre code of the video signal to be displayed is the middle classification “soccer” or “sumo / martial arts” further classified in the major classification “sports”. Each APL frequency is shown in a histogram.

  The APL frequency distribution of the input video signal can be used as a reference to determine how “appropriate” it is to control the luminance of the light source for “video to be displayed”. . As an example of controlling the light emission luminance of an appropriate light source based on this distribution, it can be said that a genre that is biased to a place where the APL of the video signal is generally high includes a lot of bright images. In the portion, control of reducing the luminance of the light source can be considered. Such control can be said to be “appropriate” control of the light emission luminance of the light source in that it can reduce screen glare and eye irritation, as well as reduce power consumption.

  The above control example will be described by taking the APL distribution (FIG. 5A) of the video signal whose input video signal genre is broadly classified as “news / report”.

  First, in a portion where the appearance frequency of the video signal is low and the APL of the input video signal is low (A in FIGS. 6A and 6B), the light emission luminance of the light source is set to a high and constant value. The low APL area is a dark image, so even if the light source brightness is set high, the effect of screen glare and eye irritation is small, while improving the gradation expression of the dark image area and the dark screen. This is because the peak portion in the inside is conspicuous and a beautiful image with a sense of contrast can be obtained.

  In the range of APL in which the appearance frequency of the video signal is high (between BD in the horizontal axis direction in FIG. 6A), the emission luminance of the light source is decreased as the detected APL of the video signal is higher. Then, control is performed to reduce the glare of the screen and the irritation to the eyes and display the video with appropriate luminance (between BD in the horizontal axis direction in FIG. 6B).

Here, the luminance of the light source is set to change more rapidly as the appearance frequency of APL in the video signal is higher. That is, since the appearance frequency of the video signal is higher between B and C in the horizontal axis direction of FIG. 6B than between C and D, the slope of the luminance control characteristic with respect to APL is increased (between B and C). Slope x ₁ > C-D slope x ₂ ). As described above, by increasing the increase / decrease degree of the light source luminance on the screen having the APL having a high appearance frequency, it is possible to effectively reduce the power consumption by the backlight light source.

  In a portion where the appearance frequency of the video signal is low and the APL of the input video signal is high (E in FIGS. 6A and 6B), the light emission luminance of the light source is set to a low and constant value, and the screen is dazzled and the eyes Try to reduce the impact on the stimulus as much as possible.

  As described above, based on the histogram of the appearance frequency of the video signal according to the video feature amount, the change in the light emission luminance of the light source is increased in the portion of the video feature amount where the appearance frequency of the video signal is high (light source for the video feature amount). The control characteristic is increased).

  In the following, for convenience of explanation, a point at which the inclination indicating the light emission luminance control characteristic of the light source with respect to the video feature amount changes is defined as a characteristic change point. In FIG. 6 (b), intersections B, C, and D of four straight lines are characteristic change points (the portions indicated by A and E have zero slope).

In order to simplify the light emission control of the light source, from the characteristic that the light emission luminance of the light source is high and constant at a portion where the APL of the input video signal is low (A in FIGS. 6A and 6B) (zero slope). The light emission luminance of the light source is lowered at the characteristic change point B, which is a point to change to the characteristic having an inclination, and the part where the APL of the input video signal is high (E in FIGS. 6A and 6B) due to the characteristic having the inclination. characteristics between the predetermined value and to have properties which are point with change (slope zero) characteristic change point D, may be a connecting it characteristics with a straight line (slope x ₃ in Figure 6 (b)).

  Examples of general brightness control for each genre include the above examples. Actually, however, there are various individual circumstances related to video display depending on the genre. It is difficult to make a uniform decision as in the example. Therefore, it is necessary to grasp the individual circumstances for each genre and determine an appropriate light source luminance control characteristic. Hereinafter, appropriate control of the light source will be considered by taking several genres as examples.

<News / Report>
News and reports are characterized by many scene changes because many incidents are reported from one to the next. It is content that can be seen on a daily basis as part of life.

  Therefore, it is desirable to perform a gentle video display that blends into life by making the change in the light emission luminance of the light source according to APL more gradual than the luminance control table showing the general control shown in FIG. That is, when the genre of the video to be displayed is “news / report” in the large classification, the range of APL for changing the light source luminance (between BD in the horizontal axis direction in FIG. 6B) is increased, or Alternatively, it is preferable to control the light emission luminance of the light source using a luminance control characteristic that reduces the difference between the maximum level and the minimum level of the light emission luminance of the light source.

  An example of the brightness control table in which the change in the light emission brightness is moderated is shown in FIG. When compared with the same brightness control characteristic as FIG. 6B shown in FIG. 7B as a comparison object, it can be seen that the range of APL for changing the brightness is large.

  In addition, news and reports have the property that facts should be conveyed accurately. Therefore, it is desirable to display the video as it is so that information can be transmitted reliably regardless of whether the video signal is dark or bright.

  From this point of view, as shown in FIG. 7 (d), compared to the comparison target in FIG. 7 (b), the increase / decrease width of the light emission luminance of the light source (in FIG. 6 (b), in the vertical axis direction). The width between B and D) is reduced so as to display the image as it is. In addition, news and news reports are often shot in the studio, so it can be said that there are many bright images from lighting in the studio. Therefore, as shown in FIG. 7E, a luminance control characteristic may be used in which the emission luminance of the light source is reduced as a whole and the increase / decrease width of the emission luminance of the light source is further small. Furthermore, in the news and news reports, the fact that the fact should be accurately conveyed is thoroughly enforced, and the light emission luminance of the light source according to the input video feature quantity such as APL is not controlled. As shown in FIG. It is also possible to do.

  As described above, the control region corresponding to the APL between BD in the horizontal axis direction shown in FIG. 7B is controlled according to the APL between FG in the horizontal axis direction shown in FIG. By enlarging the area (enlarging the main part of the control range in the video feature amount), it is possible to moderate the change in the light emission luminance of the light source according to the APL.

  Further, by narrowing the difference (the difference between the maximum emission luminance and the minimum emission luminance) between the value that makes the emission luminance of the light source high and constant at low APL and the value that makes the emission luminance of the light source low and constant at high APL, the light source The light emission luminance can be moderately changed.

  As described above, the genre information detection unit 13 extracts a genre code from the broadcast signal received by the tuner 11-2 in a broad classification, and determines that the genre of the video to be displayed on the video display unit 16 is “news / report”. In this case, it is appropriate to control the light emission luminance of the light source by the light source control unit 18 using the luminance control table of any one of FIGS. 7B to 7F.

"movies"
Referring to FIG. 5B, in the large classification “movie” in the genre code, the total average luminance level of the input video signal is 25%, which is lower than other genres. The appearance frequency of the video signal for each APL is distributed more in the portion where the APL is low.

  Judging from this result alone, considering the above general control example, since many dark images are included, even if the brightness of the light source is increased, the effect of glare is not felt. The control should increase the brightness of the light source as much as possible.

  However, since movies are viewed concentratedly for a long time, there is a particular situation in which it is desirable to display a natural and immersive video with as little stimulus as possible to the viewer's eyes. In addition, movie images are generally dark overall, but there is also a property that a bright scene suddenly appears due to a scene change.

  Therefore, when “movie” is displayed, as shown in FIG. 8B, the light source is set so that there is no extremely bright display (or display time) even in a bright scene or a dark scene. It is preferable to control the luminance at a luminance lower than the average luminance.

  By doing so, it is possible to not feel dazzling, provide a sense of presence as if watching in a movie theater, and relieve eye irritation caused by a bright scene that appears suddenly. In FIG. 8B, the brightness of the light source is increased in order to give a sense of contrast and make the subtitles easier to read, particularly in dark scenes.

  From the viewpoint of power consumption, for example, in order to sufficiently reduce the light emission luminance of the light source when the APL included in a general video signal is 40%, the light emission luminance of the light source from where the APL is 30%. Even if the setting is made to gradually reduce the value, in the case of a movie, since the place where the frequency of APL is the highest is around APL 20%, the effect of reducing power consumption is low.

  If the light emission luminance of the light source is controlled by using the luminance control characteristic of FIG. 8B, the light emission luminance of the light source is changed to be reduced at APL 20%, so that the power consumption is effectively reduced. Can be made. Considering the feature that a movie is a content that is viewed for a long time, the effect of reducing power consumption can be said to be much greater.

  In addition, when there are many dark images such as movies, the luminance of the displayed video is changed by reducing the luminance of the light source rather than reducing the luminance of the displayed video by reducing the video signal level. Therefore, there is a great merit that the brightness of the screen to be displayed can be reduced while preventing deterioration in image quality such as gradation loss in dark images.

  Specifically, the gradation expression is usually expressed by a predetermined bit (for example, 8 bits = 256 gradations). For example, when converting the luminance of the input video signal to half luminance, if this is performed by adding processing to the video signal level as in Patent Documents 4 and 5, the input is 7 bits = 128 gradations. When displaying a “movie” video that contains many low-level video signals, the number of tones that can be expressed in the dark area is reduced and the tone is lost. appear. On the other hand, even if the luminance of the image to be displayed is halved by suppressing the light emission luminance of the light source, it is suitable for “movie” while maintaining the grayscale display by gradation expression with 8 bits = 256 gradations. Since the display brightness is set, it is possible to display an image suitable for the content “movie” without degrading the quality of the displayed image.

《Anime / Special Effects》
Referring to FIG. 5 (c), in the large classification “animation / special effects” in the genre code, the average luminance of the input video signal is 51%, and the appearance frequency of the video signal for each APL is gently distributed in a slightly high part. ing. In the APL distribution in FIG. 5, it can be said that the distribution of the input video signal is similar to “news / report”.

  Therefore, from the result of FIG. 5 (c) alone, the brightness control table similar to that of the major category “news / reports” may be used. There are various circumstances.

According to the “Guidelines on Video Techniques for Animation” compiled by the Japan Commercial Broadcasting Corporation, it was reported that viewers, especially many children, caused seizures while watching animated programs. According to this report, the cause of this seizure is
1. 1. Flashing images and lights, especially “bright red” 2. Inversion of screen with strong contrast and sudden scene change The use of regular pattern patterns is considered. In response to this, in the above commentary,
1. In principle, the flashing of images and lights should not be used more than 3 times per second, and the following points should be noted.
(1) Treat “bright red” flashing with caution.
(2) When flashing more than 3 times per second is required after satisfying the condition of (1) in the previous section, limit the number of times to 5 times and suppress the screen brightness change to 20% or less. In addition, do not use continuously for more than 2 seconds.
2. As a general rule, inversion of a screen with strong contrast or a rapid scene change in which the luminance change of the screen exceeds 20% is not used more than 3 times per second.
3. Avoid regular pattern patterns (stripes, swirls, concentric circles, etc.) occupying most of the screen.
It stipulates.

  Therefore, when displaying an animation program, it is preferable to reduce the luminance of the light source to suppress the luminance change of the screen and to reduce the human influence due to the abrupt luminance change (point 2 above). Further, by performing such control, the human influence caused by excessive blinking of light can be reduced (point (1) (2) above). Furthermore, it is possible to reduce heat generation and power consumption of the display device during animation program display.

  As described above, when an animation is displayed, the luminance of the light source is controlled to be lower than the average luminance as shown in FIG. In FIG. 9D, the brightness / control tables for news / reports shown in FIG. Even if the total average of the luminance levels of the input video signal is approximate and the distribution is similar to news / reports, the change width of the light emission luminance (the difference between the maximum light emission luminance value and the minimum light emission luminance value of the light source) ) Is narrower and the brightness control characteristics are different.

  In particular, the viewers of animation programs have many children, and it is very important from the point of view of child-friendly video display to relieve eye irritation in this age, which has a great influence on visual acuity.

  In addition, the animation is vivid, painted with a uniform color, and is a simple image, so that unevenness, noise, and turbidity are raised. In addition, the boundary between colors tends to blur. And because of the vividness of the color, it can be said that flicker is conspicuous. From this point of view, it can be said that when displaying an animation program, it is preferable to reduce the light emission luminance of the light source and suppress them.

  As described above, the genre information detection unit 13 extracts the genre code from the broadcast signal received by the tuner 11-2 in the large classification, so that the genre of the video to be displayed on the video display unit 16 is the large classification “animation / special effects”. Is determined, the luminance of the light source may be controlled by the light source control unit 18 using the luminance control characteristics as shown in FIG.

《Sports (Soccer, Sumo, Martial Arts)》
In the above, the situation for each major classification of genre codes has been examined. Here, the middle classification “soccer” and “sumo / martial arts” in the major classification “sports” are considered.

  First, as shown in FIG. 10, when the input video signals of the middle category “soccer” and the major category “news / report” are compared, the average luminance is 51% and 48%, and there is not much difference.

  However, in the case of soccer, it can be said that there are many images of the lawn and there are few large scene changes. From the comparison of the APL distribution shown in FIGS. 10 (a) and 10 (b), the distribution of the APL of the video signal of the middle classification “soccer” is different from the large classification “news / report” and the range of the predetermined APL It can also be read from the fact that the distribution is biased to.

  In addition, “soccer” is content that the viewer wants to view with a sense of unity with the video.

  Therefore, when the genre of the video to be displayed is the middle classification “soccer”, the luminance of the light source can be changed greatly within a specific APL range to produce a sense of realism and to effectively reduce power consumption. Brightness control characteristics. Specifically, as shown in FIG. 10C, the main control width of the light emission luminance of the light source according to APL (the characteristic change point corresponding to the lowest APL and the characteristic change point corresponding to the highest APL in FIG. 10C). And a luminance control table for abruptly changing the light emission luminance of the light source may be used by increasing the inclination of the luminance control characteristics in the vicinity of the peak frequency of appearance of the video signal for APL. The distance (main control width) between the two approximate characteristic change points corresponding to APL is smaller than the brightness control characteristic (FIG. 10 (d)) of news / report that performs smooth video display.

  In addition, as shown in FIG. 11, when the middle classification “soccer” and the middle classification “sumo / martial arts” are compared, the average luminance of the input video signal of the “sumo / martial arts” is as low as 35%. The frequency of occurrence is distributed in a slightly low APL range. That is, it can be said that “soccer” and “sumo / martial arts” are different in the average of APL and the portion where the frequency of appearance of video signals at APL peaks.

  Under such a premise, when the display brightness of “sumo / martial arts” is controlled using, for example, the brightness control table of soccer (FIG. 11C), the frequency of appearance of video signals for APL peaks. Since the portion is shifted, the light emission luminance of the light source becomes the maximum value in most scenes, and the effect of reducing power consumption is completely eliminated.

  Therefore, when the genre of the video to be displayed is the middle classification “sumo / martial arts”, the light emission luminance of the light source is changed within a low APL range to “soccer”. At this time, the two approximate characteristic change points corresponding to APL are located in the lower APL portion than “soccer”.

  In this way, even if the same genre is used in the large classification, the circumstances to be controlled in the genre in the middle classification may be different. If the brightness control table for each genre is provided for each middle classification, the genre is more finely defined. It is possible to display “appropriate” video for each.

  Another example of controlling the light source brightness based on the genre in the middle category is to lower the light emission brightness of the light source when the domestic category is “domestic animation” or “overseas animation” in the middle category “Anime / SFX”. By using the brightness control table of FIG. 9C only when the content type is “animation”, it is possible to control the light emission brightness of the light source with a more targeted focus. In addition, it is desirable that the medium classification “classical music” and “rock music” in the large classification “music” control the light emission luminance of the light source using different luminance control characteristics.

  As described above, in order to appropriately set the light emission brightness of the light source based on the genre information of the video to be displayed, "appropriate" display brightness is achieved for each genre while maintaining the gradation expressive power of the display device. It becomes possible to do. In addition, by switching the light emission luminance characteristics of the light source according to the feature amount of the input video for each genre, the power consumption of the light source can be effectively reduced.

  Here, in order to further reduce the power consumption sufficiently, the luminance control characteristics as shown in FIG. 12 are preferable. In other words, the light emission luminance of the light source in the portion where the image feature amount is extremely large and the portion where the image feature amount is small is reduced. The reason is that the brightness control characteristic when the genre is “news / report” (FIG. 12 (a)) is taken as an example, the portion where the APL as the video feature amount is extremely large, for example, the white where the APL is 90% or more. As can be seen from the APL frequency in FIG. 6 (a), the near video does not exist so much as a normal video, and even if such a video exists, it is an instant or almost a scene change. Therefore, even if the light emission luminance of the light source is reduced in this portion, the viewer hardly feels the influence of the luminance reduction. In addition, since a portion with very small APL, for example, a nearly black image such as APL 10% or less does not exist as a normal image, it is preferable to set the light emission luminance of the light source to be small in this portion as well.

  If there are not many images with very large or small image features, it may not be necessary to reduce the luminance at that part, but with the recent increase in size of display devices The power consumption of the backlight brightness is enormous, and the power consumption of the video features is extremely large or small can no longer be ignored. It has become important.

  FIG. 12B shows luminance control characteristics for reducing the light emission luminance of the light source at a portion where the video feature amount is extremely large and a portion where the video feature amount is extremely small when the genre is “movie”. Compared with the brightness control characteristics of “News / Report” in FIG. 12A, the characteristic change point where the APL as the video feature amount is the smallest is that “Movie” is more than “News / Report”. It is located at a smaller position in the APL direction. As shown in the distribution diagrams of the video signals in FIGS. 5A and 5B, the video signal of “movie” is often darker than “news / report”, and the APL as the video feature amount is extremely small. This is because the portion considered as “news / report” is set narrower than in the case of “news / report” so as not to adversely affect the delicate video display in the dark portion. As described above, the characteristic change point located on the side with the largest video feature amount and the characteristic change point located on the smallest side change depending on each genre.

  In the general description of the brightness control characteristics of the “movie” described above, “In FIG. 8B, in order to provide a sense of contrast and make the subtitles easier to read, particularly in dark scenes, “The brightness is increased.” However, it is up to the design which of the characteristics is given priority especially in a dark scene. You may set so that the light emission luminance of only the part which is really near black (for example, APL 5% or less) may be made small.

  In FIG. 12, the light emission luminance of the light source of the portion having a very large video feature amount and the light portion of the small portion is reduced, but it is needless to say that only one of the portions may be provided.

  In the description of the luminance control characteristics so far, there are places where the light emission luminance value of the light source with respect to the video feature amount is constant. However, it is not a necessary condition that the light emission luminance value of the light source is constant in the luminance control characteristic. For example, as shown in FIG. There may be. In the example of FIG. 13A, in a portion where the APL as the video feature amount is low (region B in FIG. 13A), the light source is modulated to a high emission luminance in order to prevent black crushing in a dark scene. In a portion where the APL is high (region C in FIG. 13A), the light source is modulated to a low emission luminance in order to avoid excessive brightness and glare in a bright scene. In a portion where the APL is extremely low (region A in FIG. 13A), the light emission luminance of the light source is reduced as the APL is reduced, thereby reducing power consumption. In a portion where the APL is extremely high (region D in FIG. 13A), the light emission luminance of the light source decreases as the APL increases, thereby reducing power consumption. Since this characteristic can be said for general video, the luminance control characteristic in FIG. 13 has been described as a standard characteristic regardless of the genre. However, because of the standard characteristics, there is no place where the light emission luminance value of the light source is constant, and there may be a place where the light emission luminance value of the light source is constant as shown in FIG. Of course.

  By the way, if the genre of the video to be displayed is changed due to the program switching or the channel switching operation by the viewer, the luminance control characteristic is changed by switching the luminance control table used for the light emission luminance control of the light source. However, in order to prevent unnatural video display due to abrupt changes in the brightness control characteristics, from the currently selected brightness control characteristics, the target brightness control characteristics are approached. It is preferable that the plurality of luminance control tables are gradually changed over time. For example, when switching from the brightness control table corresponding to the “movie” genre to the brightness control table corresponding to the “news / report” genre, the light emission brightness of the light source is low despite the screen having the same APL. If the brightness control characteristic is suddenly switched to a brightness control characteristic with a high light emission brightness of the light source, the viewer may feel uncomfortable, such as being dazzled or having strong eye irritation.

  Therefore, in order to prevent this, several tables with brightness control characteristics that are intermediate between the brightness control characteristics of “movie” and “news / report” are prepared, and this is gradually switched every few seconds. Thus, it is preferable to suppress the sudden change in display luminance.

  In FIG. 14, several tables are prepared. 5 is a flowchart showing an operation for preventing a sudden change in luminance of the light source by changing This operation will be described below.

  No. of the currently referenced table L (“L” is a variable representing the current table). Is M (“M” is the table number selected before changing the genre code) (S141), when it is detected that the genre code separated and acquired from the broadcast signal has been changed (S142). 'Y'), and accordingly, the usage table No. corresponding to the changed genre code. (S143) (Here, it is assumed that the usage table number is determined to be “N”). As the current table L, the brightness control characteristics of the current table L (= M) among a plurality of tables in which the brightness control characteristics of the determined use table N and the current table L (= M) are intermediate. The table n closest to is selected and updated to the current table L (S144). Then, it is determined whether or not the current table L (= n) is the same as the usage table N (S145). If they are not the same, after waiting for a fixed time (for example, 1 second) (S146), among the plurality of tables that are intermediate between tables M and N, the table brightness control characteristics are the second highest in table M. The closest table n + 1 is selected (S147), and it is updated to the current table L (S144). Then, S145 → S146 → S147 → S144 is repeated until the current table L = N in S145. When the current table L = N, the change to the use table corresponding to the changed genre code is completed. To do.

  15 does not prepare a plurality of tables that are intermediate between the current table and the used table, 5 is a flowchart showing an operation of shifting to the brightness control characteristic of the table after the change by calculation when the value is changed. This operation will be described below.

  The currently referenced table No. Is S (S151), when it is detected that the genre code separated / acquired from the broadcast signal has been changed (“Y” in S152), the usage table corresponding to the changed genre code accordingly. No. Is determined (S153) (here, it is assumed that the table No. is determined as T). Then, a difference in light emission luminance with respect to the video feature amount of the input video signal between the current table S and the determined use table T is extracted, and it is determined whether or not the difference is smaller than a predetermined threshold value m ( S155). When it is determined that the difference is greater than or equal to the threshold value m, the light emission luminance characteristic based on the table S with respect to the video feature amount of the input video signal is brought closer to the light emission luminance characteristic based on the table T by a predetermined value so that the difference becomes small. As described above, after correcting S to S ′ (S157), after waiting for a certain time (for example, 1 second) (S158), the process returns to S154 again and is used with the corrected current table S (S updated after S ′) A difference from the table T is extracted, and the difference is compared with a threshold value m. The operations of S155 → S157 → S158 → S154 are repeated until the difference becomes smaller than the threshold value m. When the difference becomes smaller than the threshold value m, the current table S is changed to the use table T.

  FIG. 6 is a flowchart showing an operation of gradually changing to the brightness control characteristic of the table after the change by changing the brightness a predetermined number of times when the value is changed. Hereinafter, an operation for changing the luminance control characteristics over 256 frames will be described with reference to FIG.

  The currently referenced table No. Is P (S161), when it is detected that the genre code separated / acquired from the broadcast signal has been changed (“Y” in S162), the usage table corresponding to the changed genre code accordingly. No. (Here, it is assumed that the table No. is determined to be Q). At the same time, the number of changes c is set to 1 (S163). Then, the modified luminance is calculated by weighting the current table P and the determined usage table Q, and the luminance is corrected (S164).

Corrected luminance P ′ = (Qc + P (256−c)) / 256 (Formula 1)
Then, it is confirmed whether c = 256 (256 times as the set number of times has been corrected) (S165). If the set number has not been reached, the count value c is updated once (S167), and again. The current luminance is corrected to P ′ by the above equation 1. When the operation of S164 → S165 → S167 is repeated a predetermined number of times and the set number of times is 256 times, the current table P is finally changed to the use table Q. In the above example, the luminance table is gradually corrected over 256 frames. However, the luminance table is not limited to 256 frames, and the degree of gradual change (transition time) can be adjusted by setting a predetermined number of times. .

  As described above, when the genre code is changed, it is possible to prevent a sudden change in the light emission luminance of the light source.

  Currently, in the standard of digital broadcasting, only genre codes of “major category” and “medium category” are stipulated, but depending on future standard changes and version upgrades, minor category standards will also be stipulated. In this case, finer and more appropriate video display can be performed by controlling the light emission luminance of the light source according to the circumstances of each small classification.

  Further, it is not necessary to prepare the luminance control tables described above for the number of major classifications or middle classifications. For example, for individual circumstances relating to light emission control of the light source, the middle classification “era” in the major classification “movie” and the major classification “drama”. Since it can be said that “play” is similar to the situation, the brightness control table may be used in common.

  Conversely, the luminance control table may have more than the number of classifications of the large classification or the medium classification. For example, in FIGS. 7C to 7F, four candidates for the brightness control table used for the major classification “news / report” are illustrated, but these are used for other circumstances (for example, brightness of the viewing environment). More detailed control may be performed by switching them according to the above.

  And although it is good if the light emission luminance of the light source can be controlled according to the genre information as described above, the genre information may not be obtained. Further, there may be a case where genre information is not obtained, as in the case where the genre code is broadly classified as “other”. In such a case, the brightness control table corresponding to the genre is obtained by referring to the viewing history of the user and estimating that the genre that the user often viewed in the past is the genre of the video to be displayed. It may be used to control the light emission luminance of the light source. Alternatively, a “standard” luminance control table (for example, the characteristics shown in FIG. 13) may be prepared and used. The brightness control table may not be used (the brightness value of the light source is made constant).

  Further, in the above, the case where the video feature amount of the input video signal is APL is taken as an example, and the light emission luminance of the light source is controlled according to APL. However, the present invention is not limited to this, and the peak luminance in one frame of the input video signal The state (presence / absence or some) may be obtained and used to control the light source luminance.

  In this case, if it is better to express the peak brightness for each genre, the light source brightness is increased to control the light emission so that the peak is conspicuous to express a beautiful image, or the genre that does not need to express the peak brightness. Then, the light emission luminance can be reduced as much as possible, and the power consumption in the light source can be reduced.

  Similarly, the maximum or minimum luminance level or luminance distribution state (histogram) in a predetermined region (period) in one frame is used as the video feature amount of the input video signal, or the video feature amount obtained by combining these is used. Based on this, the light emission luminance of the light source may be variably controlled.

  Further, it is not necessary to obtain the average value of the luminance level of the video signal of all the frames to obtain the APL. For example, the average value of the luminance level of the video signal near the center excluding the edge of the display image is obtained. It may be used as a quantity. For example, based on the genre information separated / obtained from the broadcast reception signal, the gate control is performed so as to exclude a preset screen area (which is highly likely to be superimposed with characters / symbols, etc.). Measure the video feature amount of only a partial area. FIG. 17 shows the concept of the APL measurement exclusion range when the genre is medium classification and “baseball” is assumed.

  In addition, the light emission luminance of the light source according to the feature amount of the input video signal can be changed gradually with a time constant so that a rapid luminance change does not occur, and the eye irritation or discomfort It is preferable from the viewpoint.

  Moreover, although the example which controls the light emission brightness | luminance of a light source by selecting a brightness | luminance control table according to genre information was shown above, it is good also as a structure which changes a brightness | luminance control characteristic by calculation according to genre information. In this case, a plurality of function formulas having a coefficient that changes according to the feature amount of the input video signal may be prepared, and a predetermined function formula may be selected according to the genre of the video to be displayed.

  In addition to automatically switching the light emission luminance characteristics of the light source according to the genre information, if the user selects the luminance control characteristics with a remote controller or the like, the user's desired luminance control characteristics can be used. This improves usability. A configuration that switches between enabling and disabling the function of changing the luminance control characteristics of the light source according to the genre may be provided.

  Moreover, although the brightness control characteristics in each brightness control table are described as if they were linear characteristics, it is needless to say that they may be non-linear characteristics. When the brightness control characteristic is nonlinear, the brightness control characteristic should be compared with the linear brightness control characteristic described above by approximating the nonlinear brightness control characteristic to the linear brightness control characteristic and assuming an approximate change characteristic point. Can do.

  This will be specifically described. For example, it is assumed that the luminance control characteristic whose genre is broad classification and “news / report” is the nonlinear characteristic shown in FIG. If this nonlinear characteristic is approximated by a straight line, it can be simply approximated by three straight lines as shown by dotted lines in FIG. The three straight lines are (1) a straight line that makes the light emission luminance of the light source high and constant at a low APL, (2) a straight line that makes the light emission luminance of the light source low and a constant value, and (3) the APL between them. It is defined by a straight line approximating a non-linear curve that changes the light emission luminance of the light source according to APL with a single slope. The straight line (3) is defined by the inclination at the inflection point J of the nonlinear curve, for example.

  In this way, by linearly approximating the nonlinear luminance control characteristic, a characteristic change point can be assumed as an intersection of the straight lines (H, I in the example of FIG. 18), and this assumed characteristic change point is changed to the approximate characteristic change. Define a point. If the approximate characteristic change point is considered in the same way as the characteristic change point in the linear luminance control characteristic, the expansion of the main control width related to APL can be observed even in the case of the non-linear luminance control characteristic as in the linear luminance control characteristic. I can take it.

  Note that the number of approximate straight lines is not limited to three, and may be approximated by four or more straight lines. For example, when approximated by four straight lines, there are three approximate characteristic change points.

<Second Embodiment>
Subsequently, a second embodiment of the present invention will be described. The block diagram of the display device according to this embodiment is the same as that of FIG. 1 used in the first embodiment. However, in this embodiment, the setting of the light source luminance is simplified and the feature amount of the input video signal is used. Regardless, the brightness level is constant. Specifically, as shown in FIGS. 19B to 19D, a predetermined light source luminance is set for each genre of video to be displayed, and the light source luminance level is stored in a storage device such as a ROM. ing.

  Sports are set to have a high light source luminance to improve the dynamic presence (FIG. 19B). News and reports are preferably set to a slightly higher light source luminance because it is preferable to faithfully convey the fact (FIG. 19 (c)). Since the movie is content that is immersed and viewed for a long time in a dark viewing environment, the luminance of the movie is set to be low (FIG. 19D).

  Here, when changing the luminance value of the light source, it is important to change this while maintaining the chromaticity of the light source. In particular, when the light source is an LED composed of blue, red, green, etc., the light emission luminance of the light source should be controlled while keeping the white balance (white balance) obtained by mixing these colors constant.

  In addition to the genre information of the video to be displayed as described above, the configuration for controlling the light emission luminance of the light source using the illuminance information obtained by detecting the brightness of the viewing environment, as in the first embodiment. Then, more effective light source control becomes possible.

  Further, the light source luminance control operation for each genre may be configured to be arbitrarily selected by the user.

<Third Embodiment>
Next, a third embodiment of the present invention will be described. In the first and second embodiments, the description has been given of the display device that only controls the light emission luminance of the light source to decrease as the APL of the input video signal increases. However, in this embodiment, the light source control is performed. In addition, it will be described that video signal processing may be added.

  FIG. 20 shows an example of a brightness control table for each genre (major category) according to this embodiment. Unlike the first embodiment, the luminance control characteristic of the present embodiment is a luminance control characteristic that increases the light emission luminance of the light source as the APL as the video feature amount of the input video signal increases. This is because images with a low APL can be said to be dark images as a whole, so the light source brightness is lowered in dark images, and the black level is sufficiently suppressed by expanding the video signal level and expanding the dynamic range. The purpose is to improve the sense of contrast. Similarly, for a video with a high APL, the video signal level is compressed and the light emission luminance of the light source is increased to suppress the occurrence of white crushing.

  As described above, the present invention is applied to the method of improving the contrast feeling of the display image by performing the light emission luminance control corresponding to the feature amount of the input image signal and simultaneously performing the expansion / contraction processing of the image signal. In this case as well, by performing optimal light source control for each content type, it is possible to reduce power consumption while maintaining contrast.

  In the above-described embodiment, in addition to appropriate control of the light emission luminance of the light source, an optimal video expression can be performed for each content type by combining changes in gradation conversion characteristics such as gamma correction and contrast correction. Is possible. For example, since a movie has a low APL, the gradation conversion is performed using the characteristics shown by the curve D in FIG. In sports, since the image has a high APL, the gradation conversion is performed using the characteristics shown by the curve E, thereby improving the expressiveness of the high gradation portion. In the case of news / reporting, video may be displayed with the characteristics of the straight line A in FIG. 23 without gradation conversion.

  At this time, if the gradation conversion processing is performed on the video signal, the number of gradations that can be expressed is reduced for the above-described reason. Therefore, the reference gradation for driving the liquid crystal display panel corresponding to the input video signal. What is necessary is just to comprise so that a voltage may be varied. Specifically, a plurality of predetermined reference gradation voltage data are stored, and these are switched and selected according to the genre of the video to be displayed, so that the optimum gamma correction and contrast correction are performed for each content type. Etc. can be performed.

  In this embodiment as well, whether the luminance control characteristic is a linear characteristic as shown in FIGS. 23A to 23C or a nonlinear characteristic as shown in FIGS. 23D to 23F. It doesn't matter.

<Fourth Embodiment>
This embodiment uses a display device in the case where the backlight source is an LED as shown in FIG. The block diagram is the same as that shown in FIG.

  The LED light source typically includes three primary color light sources, an R (red) light source, a G (green) light source, and a B (blue) light source. Therefore, by independently controlling the light source of each color, it is possible to have a chromatic effect on the video display surface.

  According to the "Guidelines for video techniques such as animation" shown in the first embodiment, in order to prevent seizures, avoid flashing video and light, especially "bright red". It must be necessary. The present embodiment is characterized in that flashing of “brilliant red” is reduced by utilizing the fact that the light source is an LED light source.

  Specifically, when the genre code is extracted by the genre detection unit 13 and it is determined that the genre of the video displayed on the liquid crystal panel 16 is broadly classified as “animation / special effects”, the control unit 14 selects the blue light source. A control signal is given to the light source control unit 18 so as to increase the emission luminance of the light source.

  This is because it is effective to relieve the stimulus caused by the blinking of red by increasing the influence of blue.

  As a result, the human influence caused by the flashing of the red light source can be reduced, and a viewer-friendly video display can be performed.

  When the genre information is extracted by the genre information detection unit 13 and the genre to be displayed on the liquid crystal panel 16 is determined to be broadly classified as “animation / special effects”, the control unit 14 determines the emission luminance of the red light source. A control signal may be given to the light source control unit 18 so as to be lowered.

  Even with such light source luminance control, the human influence caused by the flashing of the red light source can be mitigated, and the increase in heat generation and power consumption of the light source, which are important problems of the liquid crystal display device, can be suppressed. Can do.

  Of course, control may be performed to increase the emission luminance of the blue light source and lower the emission luminance of the red light source.

  In the present embodiment, it is preferable to provide the distance sensor 21 and control the light emission intensity of the light source according to the distance from the viewer.

  As described above, in the present embodiment, the liquid crystal display device including the LED light source has been described as an example. However, any video display device that can independently control RGB and can have a chromatic effect on the video display surface. Applicable.

  Of course, the category code may use middle classification.

  In addition, when an LED light source is used as in the present embodiment, it is easy to control the light source luminance in accordance with the feature amount of the input video signal for each screen division area.

  As described above, in the embodiment of the present invention, a liquid crystal display device including a liquid crystal panel that displays an image and a light source that irradiates the liquid crystal panel, depending on the genre of the image displayed on the liquid crystal panel A configuration is adopted in which the light emission luminance characteristic of the light source is changed with respect to the feature amount of the input video signal.

  This makes it possible to always display an appropriate display image by automatically displaying the image with display brightness suitable for each content and genre without degrading the display quality of the image, and is unnecessary. Power consumption can be sufficiently suppressed.

  Specifically, by changing the light emission luminance characteristic of the light source with respect to the feature amount of the input video signal, a characteristic change point that is a point at which the inclination indicating the light emission luminance characteristic of the light source with respect to the video feature amount is changed, or The approximate characteristic change point, which is the characteristic change point when the light emission luminance characteristic according to the image feature amount is approximated by three lines, is changed, or the difference between the maximum value and the minimum value of the light emission luminance of the light source is changed. By making it change, it can be set as the appropriate luminance control characteristic for every genre.

  The light emission luminance characteristic of the light source with respect to the input video signal may be changed after the input video signal is expanded and contracted.

  The light emission luminance characteristic of the light source for the input video signal may be changed after changing the gradation conversion characteristic of the input video signal.

  The light emission luminance of the light source may be changed based on a look-up table selected according to the genre of video displayed on the liquid crystal panel.

  The light emission luminance of the light source may be changed based on an arithmetic expression selected according to the genre of the video displayed on the liquid crystal panel.

  The arithmetic expression may be a function for obtaining the light emission luminance of the light source according to the feature amount of the input video signal.

  The feature amount of the input video signal may be an average luminance level of the input video signal.

  A liquid crystal panel for displaying an image; and a light source for irradiating the liquid crystal panel with white light, and maintaining the white chromaticity substantially constant according to a genre of the image displayed on the liquid crystal panel. Even with the configuration in which the increase / decrease of the light emission luminance of the light source is adjusted, it is possible to perform a preferable video display according to the genre and suppress unnecessary power consumption.

  The genre of the video displayed on the liquid crystal panel may be determined based on a genre code multiplexed in the input video signal, or may be determined based on past viewing history information.

  The present invention can be used for an image display device that displays an image using a light modulation element such as a liquid crystal display device and a backlight light source.

2 is a block diagram illustrating a configuration of a display device according to Embodiment 1. FIG. It is an external view which shows the example of the backlight apparatus used for the display apparatus of this invention. It is an external view which shows the other example of the backlight apparatus used for the display apparatus of this invention. It is a figure showing the genre code defined by the standard of digital broadcasting. It is the figure which showed distribution of the frequency of APL of the video signal received by terrestrial digital broadcasting for every genre. It is a figure which shows the brightness | luminance control table determined taking the case where a genre is a major classification and is "news / report". It is a figure which shows the frequency of a brightness | luminance control table and APL which are preferably used when a genre is a large classification and is "news / report". It is a figure which shows the frequency of a brightness | luminance control table and APL which are preferable to be used when a genre is a large classification and is a "movie." Brightness control table and APL frequency that is preferable to be used when the genre is a large classification and “animation / special effects”, and the luminance control table and APL when the genre as a comparison target is a large classification and “news / report” It is a figure which shows the frequency of. The figure which shows the brightness | luminance control table and APL frequency which are preferably used when a genre is "soccer", and the brightness | luminance control table and APL frequency when a genre as a comparison object is a major classification and is "news / report". It is. Luminance control table and APL frequency preferred to be used when the genre is middle-class “sumo / martial arts”, and the luminance control table and APL frequency when the genre as a comparison target is “soccer” with middle-class FIG. It is a figure which shows the brightness | luminance control characteristic which makes the light emission brightness | luminance of a light source low in the part with very high and low APL. It is an example of the brightness | luminance control characteristic of the light source with respect to an image | video feature-value when a brightness | luminance does not have a fixed part. It is a figure which shows the operation | movement which prevents the rapid luminance change of a light source by changing a luminance control characteristic table gradually. It is a figure which shows the operation | movement which prevents the rapid luminance change of a light source by making the luminance between different luminance control characteristic tables little by little. It is a figure which shows the operation | movement which prevents the rapid brightness | luminance change of a light source by changing gradually the brightness | luminance between different brightness | luminance control characteristic tables over predetermined times. It is a figure which shows the example of the non-operation area | region at the time of calculating | requiring APL. It is a figure which shows the example of a non-linear brightness | luminance control table in case a genre is a major classification and is "news / report". It is a figure which shows the luminance control table in case light source luminance control is simple. It is a figure which shows the example of the brightness | luminance control table used when an image | video signal is expanded and contracted simultaneously with the control of the light emission brightness | luminance of a light source, and video display is performed. It is a figure for demonstrating the technique of patent document 4. FIG. It is a figure for demonstrating the technique of patent document 5. FIG. It is a figure for demonstrating a gradation characteristic.

Explanation of symbols

11 genre information input unit 12 decoder 13 genre information detection unit 14 control unit 15 video adjustment unit 16 video display unit 17 LCD controller 18 light source control unit

Claims (11)

A liquid crystal panel for displaying an image, and a light source for illuminating the liquid crystal panel,
A liquid crystal display device that variably controls the light emission luminance of the light source based on a feature amount of an input video signal,
Providing genre detection means for detecting genre information superimposed on the input video signal;
A liquid crystal display device that changes luminance control characteristics for variably controlling the light emission luminance of the light source based on the feature amount of the input video signal in accordance with genre information detected by the genre detection means.   The characteristic change point, which is a point at which a slope indicating a luminance control characteristic for variably controlling the light emission luminance of the light source is changed based on a feature amount of the input video signal, is changed by changing the luminance control characteristic. The liquid crystal display device according to claim 1.   By changing the luminance control characteristic, an approximate characteristic change point indicating an intersection point when the luminance control characteristic for variably controlling the light emission luminance of the light source based on a feature amount of the input video signal is approximated by a straight line is changed. The liquid crystal display device according to claim 1.   4. The liquid crystal display device according to claim 1, wherein a difference between a maximum value and a minimum value of light emission luminance of the light source is changed by changing the luminance control characteristic. 5.   5. The liquid crystal display device according to claim 1, wherein the input video signal is expanded and contracted and the luminance control characteristic is changed.   5. The liquid crystal display device according to claim 1, wherein a gradation characteristic of the input video signal is corrected and the luminance control characteristic is changed.   5. The liquid crystal display device according to claim 1, wherein a gradation conversion characteristic for the input video signal is changed and the luminance control characteristic is changed.   8. The liquid crystal according to claim 1, wherein the light emission luminance of the light source is controlled based on a lookup table selected according to genre information detected by the genre detection means. Display device.   8. The liquid crystal display according to claim 1, wherein the light emission luminance of the light source is controlled based on an arithmetic expression selected according to genre information detected by the genre detection means. apparatus.   The liquid crystal display device according to claim 9, wherein the arithmetic expression is a function for obtaining a light emission luminance of the light source based on a feature amount of the input video signal. The liquid crystal display device according to claim 1, wherein the feature amount of the input video signal is an average luminance level of the input video signal.

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