JP2009134237A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain sufficient moving image display performance even when a backlight lighting period is increased or decreased according to the contents of video data.
SOLUTION: Circuits 8050 and 8060 for increasing / decreasing a lighting period of a backlight 8090 that illuminates a display panel 8010 according to the contents of video data 8002, setting information 8003 from an external device, and the like, and back according to the length of the lighting period Circuits 8070 and 8080 for adjusting the lighting start timing (and extinction) timing are provided.
[Selection] Figure 8

Description

  The present invention relates to a display device including a display panel that displays an image by adjusting the transmittance of light from a light source.

  When display devices are classified in particular from the viewpoint of moving image display characteristics, they are broadly classified into impulse-type display devices and hold-type display devices. An impulse type display device is a type in which the brightness of a scanned pixel is increased only during a scanned period, such as a cathode ray tube, and the brightness is decreased immediately after scanning. The hold type display device is a liquid crystal display device. In this way, the luminance based on the display data is kept until the next scanning.

  The hold-type display device has an advantage that a good display quality without flicker can be obtained when a still image is displayed, while the surrounding of a moving object appears blurry when a moving image is displayed. Video blur occurs and display quality deteriorates significantly.

  FIG. 1 is a diagram for explaining an example of moving image blurring that occurs in a hold-type display device. FIG. 1A shows an example of a video pattern for evaluating moving image blur. A rectangle of another gradation (for example, black) is displayed on a background of a certain gradation (for example, white). The gradation change of this pattern is stepped as shown in FIG. Evaluation of motion blur can be performed by scrolling such a video pattern in the horizontal direction.

  FIG. 1C shows an example of an image perceived when a person observes the pattern displayed on the hold type display device. Originally, a rectangular outline portion that should have a sharp outline appears blurred as shown in the figure. The luminance change perceived at this time becomes a gentle change with a rounded outline as shown in FIG. When the perceived luminance is normalized as shown in FIG. 1D, and the normalized perceived luminance changes from 0.1 to 0.9 (or from 0.9 to 0.1), for example. The width is called a moving image blur width, and can be used as an index of moving image blur.

  This motion blur is caused by the so-called retinal afterimage, in which the observer's vision integrates and perceives the display before and after the movement of the display image with the brightness held when the line of sight moves as the object moves. Therefore, no matter how much the response speed of the display device is improved, the moving image blur is not completely eliminated.

In order to solve such moving image blur, in the hold type display device, the display characteristics of the display device are brought close to those of the impulse type display device by controlling on / off of a shutter or a light source (backlight) provided on the display surface. A method has been proposed (see Patent Document 1). Furthermore, in relation to the technology for intermittently lighting the above-mentioned backlight, a method for improving the image quality by modulating the peak luminance by increasing / decreasing the backlight lighting period in conjunction with video display data has been proposed. (See Patent Document 2).
JP-A-9-325715 JP 2004-62134 A

  In a display device that performs display by intermittently turning on the backlight, when the lighting period is set to a certain length, the degree of occurrence of moving image blur increases and decreases depending on the time from the start of lighting of the video data to the start of lighting of the backlight. That is, there is an optimum lighting start timing that minimizes moving image blurring when the lighting time is the length. Furthermore, the optimum lighting start timing varies depending on the length of the lighting period. Therefore, when the backlight lighting period is increased or decreased according to the content of the video data, etc., if the backlight lighting start (or extinguishing) timing is fixed, the backlight is turned on at the optimal lighting start (or extinguishing) timing. There is a problem in that intermittent lighting cannot be performed, and there is a case where sufficient moving image display performance cannot be obtained.

  In a display device that turns on the backlight intermittently, a circuit that increases or decreases the lighting period of the backlight according to the content of the video data or setting information from an external device, and the lighting start of the backlight according to the length of the lighting period ( And a circuit for adjusting the timing.

  According to the present invention, in the hold-type display device, the display characteristics of the impulse-type display device can be realized by intermittently lighting the backlight, and good display quality with less moving image blur can be obtained. Furthermore, according to the present invention, in the display device, even when the backlight lighting period is increased or decreased according to the content of the video data for the purpose of improving the image quality such as improving the contrast of the video, the backlight lighting period Regardless of the length, it is possible to always minimize the degree of motion blur and maintain good display quality.

  In the backlight intermittent lighting, the effect of improving the motion blur is higher as the backlight lighting period is shorter. That is, according to the present invention, a function for increasing / decreasing the backlight lighting period is provided, for example, an operation mode in which the backlight lighting period is short and the screen is dark but the moving image blur is small, and the backlight lighting period is long and the moving image blurring is performed. It is possible to provide a highly convenient display device in which an operation mode having a large screen but a bright screen is provided so that a user of the display device can select the operation mode according to preference.

  The best mode of the present invention will be described below. First, the basic configuration and operation of the present invention will be diffracted, and then the specific contents of the invention will be described in detail with reference to the drawings of the embodiments. .

  FIG. 2 is a diagram illustrating a configuration example of a display panel and a backlight in a display device to which the present invention is applied. The display panel 200 is, for example, a liquid crystal display panel, in which display elements of M columns and N rows are arranged in a matrix form as pixels (display units), and the transmittance (modulation of light transmitted through the liquid crystal) is individually set for each pixel. ) Can be controlled (M and N are each an integer of 1 or more). The backlight 201 has a role of illuminating the display panel 200. For example, a cold cathode tube (CCFL), a hot cathode tube (HCFL), a light emitting diode (LED), or the like can be used. The backlight has a configuration in which at least one or more illumination areas are arranged in P columns and Q rows, and the luminance and lighting / extinguishing timing can be controlled for each illumination area (P and Q are each an integer of 1 or more, FIG. 1). Shows an example of P = 1). The final display brightness of each pixel of the display device is obtained by multiplying the transmittance of each pixel of the display panel 200 by the brightness of each region of the backlight 201 corresponding to the pixel. The display device presents a set of display luminances of the pixels to the observer as a display image of the display device.

  Next, using FIG. 3 and FIG. 4, the principle of reducing moving image blur in a display device to which the present invention is applied will be described. FIG. 3A is a diagram illustrating an example of a response of transmittance in the display element constituting the display panel. In FIG. 3A, the horizontal axis indicates time, and the vertical axis indicates transmittance. The transmittance before and after the change in transmittance due to rewriting of display data was normalized and displayed as 0 and 1, respectively.

  The display device rewrites display data of each surface element at a predetermined interval. This rewrite interval is defined as one frame period Tf. For example, if the display panel is driven at 60 Hz (display data is rewritten 60 times per second), one frame period Tf is about 16.7 ms. FIG. 3A shows that the transmittance is 0 until time t, and the display data starts to respond as the display data changes at time t, and the transmittance gradually changes and transmits at time t + Tf. This is an example of a response that the rate is 1.

  FIG. 3B is a diagram illustrating an example of a change in luminance when the backlight that illuminates the display element is intermittently lit. In FIG. 3B, the horizontal axis represents time, and the vertical axis represents backlight luminance. The brightness of the backlight when turned off and when turned on was normalized and displayed as 0 and 1, respectively. FIG. 3B shows an example in which the lighting standby time until data rewriting and backlight lighting is 0.6 Tf and the lighting rate is 50% (0.5 Tf). Here, the lighting rate is defined as Ton / Tf × 100 (%), where Ton is a period during which the backlight is turned on.

  In the example of FIG. 3B, switching on and off is performed every 0.5 Tf period, which is half of one frame period Tf. That is, the lighting rate is 50%. In each frame, the backlight is turned on after 0.6 Tf has elapsed from the data rewrite time in each frame (that is, the lighting standby time is 0.6 Tf). This is because the backlight is turned on after waiting for the display element to respond sufficiently.

  FIG. 3C is a diagram illustrating an example of a change in luminance of the display device during intermittent lighting of the backlight. In FIG. 3C, the horizontal axis represents time, and the vertical axis represents panel luminance. The transmittance before and after the change in transmittance due to rewriting of display data was normalized and displayed as 0 and 1, respectively. The change in luminance of the display device is obtained by multiplying the transmittance of the panel shown in FIG. 3A by the luminance of the backlight shown in FIG.

  FIG. 3D is perceived by the observer's eyes when the evaluation pattern as shown in FIG. 1A is displayed on the display device having the response characteristics as shown in FIG. FIG. The horizontal axis indicates the position on the panel, and the vertical axis indicates the perceived luminance. The perceived luminance before and after the change in transmittance due to rewriting of display data was normalized and displayed as 0 and 1, respectively. The characteristic as shown in FIG. 3D is calculated in consideration of the gaze following integration effect which is a human visual characteristic. The line-of-sight tracking integration effect, which is a human visual characteristic, can be simulated by taking a moving average over a range of one frame period for a panel luminance change waveform as shown in FIG.

  In FIG. 3D, the solid line indicates an example in which backlight intermittent lighting driving is performed at a lighting rate of 50% and a standby time of 0.6 Tf, as shown in FIG. For comparison, an example of the case where the backlight intermittent lighting driving is not performed (lighting rate: 100%) is indicated by a broken line. It can be seen that the moving image blur width can be reduced in the case where the backlight intermittent lighting drive is performed, compared to the case where the backlight is not performed.

  As described above, the appearance of moving image blurring and the effect of the backlight intermittent lighting drive have been described with reference to FIG.

  Next, the influence of the timing of turning on the backlight (that is, the lighting standby time) on the moving image blur in the backlight intermittent lighting drive will be described with reference to FIG. In the example of FIG. 3, the lighting rate is 50% and the lighting standby time is 0.6 Tf. On the other hand, FIG. 4 shows an example in which the lighting standby time is set to 0 while the lighting rate is made common with 50%, as shown in FIGS. 4 (a) to 4 (c). Note that FIG. 4 is generally the same as FIG. 3 except that the phases are different, so that the description thereof is omitted. In FIG. 4D, the solid line shows an example of change in perceived luminance when the lighting standby time is zero. On the other hand, the broken line is an example in the case where the lighting standby time is set to 0.6 Tf as in FIG. When the lighting standby time is set to 0, it can be seen that the moving image blur is larger than when the lighting standby time is 0.6 Tf. Thus, when the backlight is intermittently lit, the lighting standby time of the backlight affects the size of the moving image blur.

  Next, the relationship between the lighting timing of the backlight and the lighting rate will be further described. Thereafter, in the display device of the present invention, the lighting standby time of the backlight is treated as the backlight phase. Here, the phase is Tl / when the time from the rewriting of display data until the backlight is turned on is Tl, and the effective data period of one frame within one frame period (details will be described later) is Tv. It is defined as Tv × 100 (%).

  As described above, even if the lighting rate of the backlight is constant, the magnitude of the moving image blur varies depending on the phase of the backlight (that is, corresponding to the lighting standby time). In other words, when the lighting rate is set to a certain value, a phase that minimizes moving image blur can be determined. Such a phase is called an optimum phase.

  FIG. 5 is a diagram illustrating an example of the relationship between the lighting rate of the backlight and the optimum phase. In FIG. 5, the horizontal axis represents the lighting rate, and the vertical axis represents the optimum phase. This is an example of a graph created by experimentally or theoretically deriving and plotting the phase that minimizes moving image blur for each lighting rate as the optimum phase. Using this graph, for example, when the lighting rate is x, it is possible to determine that the optimal phase that minimizes moving image blur is y.

  As shown in FIG. 5, the optimum phase varies depending on the lighting rate of the backlight. For example, the optimal phase value when the lighting rate is 60% is u, or the optimal phase value when the lighting rate is 30%, for example, is v. u and v are not necessarily the same value. That is, in the backlight intermittent lighting drive, in order to minimize the amount of moving image blurring and obtain the best moving image display quality, it is necessary to appropriately control the phase of the backlight according to the lighting rate of the backlight. I understand that.

  The relationship between the lighting rate of the backlight and the optimum phase in the display device to which the present invention is applied has been described above with reference to FIG. The display device of the present invention has a function of backlight intermittent lighting drive for the purpose of improving moving image blurring, and in the case of changing the lighting rate according to the content of video data for the purpose of improving the contrast and the like. However, by appropriately adjusting the phase and always lighting the backlight with the optimum phase according to the lighting rate, it is possible to always obtain a good moving image display quality with less moving image blur.

  FIG. 6 is a timing chart for explaining an operation example of the display device to which the present invention is applied. In FIG. 6, the horizontal axis shows the passage of time. FIG. 6 illustrates a temporal relationship among “screen scanning” of the display panel, “lighting operation of the backlight”, and “backlight control signal” with respect to the input signal of the display device. In the figure, the vertical synchronization signal is a signal that defines one frame period Tf of video data. Video data is configured by arranging video for each frame in time series. Between each frame, there is a period in which no valid data exists (referred to as a vertical blanking period). Of one frame period, a period excluding the vertical blanking period is defined as one frame data effective period Tv (that is, Tv ≦ Tf).

  “Screen scanning” in FIG. 6 indicates the state of the operation of the display panel when displaying video data on the display device. For each pixel belonging to N rows constituting the display panel, display data to be displayed on the pixel is sequentially written from 1 line to N lines. Generally, in order to write all the data of N lines, a period corresponding to one frame valid data period Tv is used. “Backlight lighting operation” indicates an operation state of each area of the backlight when the backlight is intermittently driven. The Q row area is sequentially turned on and off.

  One area of the backlight is associated with at least one or more lines in the display panel (ie, one area of the backlight illuminates at least one or more lines of the display device). If the cost is acceptable, it is preferable that the backlight region and the display panel line correspond to 1: 1 from the viewpoint of display quality.

  As described above, after writing the data of the line group of the display panel corresponding to each area of the backlight, after waiting for a predetermined time until the display element of the pixel of the line sufficiently responds, the backlight is turned on. . In the example of FIG. 6, a frame starts at time t0, and the display panel is sequentially scanned from one line. At time t1, scanning of the line corresponding to the backlight region 1 is completed, and at time t2, scanning of the line corresponding to the backlight region 2 is completed. Thereafter, scanning is similarly continued until the N line is reached.

  The backlight in the region 1 starts to be turned on at time t3 when the time specified by the phase has elapsed from time t1, and is turned off at time t5 when the time specified by the lighting rate has elapsed from time t3. Similarly, the backlight in the region 2 starts to be turned on at time t4 when the time specified by the phase has elapsed from time t2, and is turned off at time t6 when the time specified by the lighting rate has elapsed from time t4. Thereafter, the lighting / extinguishing operation is continued until the area Q is reached.

  The backlight control signal is a signal for controlling lighting / extinguishing of each area of the backlight. In the example of FIG. 5, a configuration using a PWM (Pulse Width Modulation) signal as the backlight control signal is shown as an example. For backlight control using a PWM signal, for example, the backlight control signal is a signal having a binary value of High and Low, and the backlight is configured so that it is turned on when the signal value is High and turned off when the signal value is Low. Can be realized by adjusting the lengths of the periods in which the period is high and the periods in which the period is low (that is, the time ratio between the two periods).

  At this time, it is preferable that Q backlight control signals based on PWM signals are individually prepared, and each region can be individually controlled in association with each of the Q row backlight regions. The method for realizing the backlight control signal is not particularly limited to the PWM signal. For example, use a method for digitally instructing the backlight on values such as phase and lighting rate, or a method for measuring and controlling the backlight control timing, and sending and instructing the backlight to turn on and off as commands. You can also. Further, a method of performing analog control using a current value, a voltage value, or the like may be used.

  As described above, the operation example in the case where the backlight intermittent lighting driving is performed in the display device to which the present invention is applied has been described with reference to FIG. Next, how the display device to which the present invention is applied changes its operation in accordance with the lighting rate of the backlight will be described with reference to FIG.

  FIG. 7 is a timing chart showing an operation example of the display device to which the present invention is applied. In FIG. 7, the lighting rate of the backlight is 30%. FIG. 6 is different in that the lighting rate of the backlight was 60%. For comparison, the backlight lighting operation (corresponding to FIG. 6) when the lighting rate is 60% is also shown. Since FIG. 7 is generally the same as FIG. 6 except that the lighting rate is different, each description is omitted because it is duplicated.

  As for the scanning of the display panel, even in the example of the lighting rate of 30%, as in the example of the lighting rate of 60%, the frame starts at time t0 and the display panel is sequentially scanned from one line. At time t1, scanning of the line corresponding to the backlight region 1 is completed, and at time t2, scanning of the line corresponding to the backlight region 2 is completed. Thereafter, scanning is similarly continued until the N line is reached.

  On the other hand, the backlight in the region 1 starts to be turned on at time t7 when the time specified by the phase has elapsed from time t1 and is turned off at time t9 when the time specified by the lighting rate has elapsed from time t7. Similarly, the backlight in the region 2 starts to be turned on at time t8 when the time specified by the phase has elapsed from time t2, and is turned off at time t10 when the time specified by the lighting rate has elapsed from time t8. Thereafter, the lighting / extinguishing operation is continued until the area Q is reached.

  Here, the time t7 and the time t8, which are the lighting start times of the area 1 and the area 2 of the backlight, are calculated from the relationship of the optimum phase corresponding to the lighting rate, as shown in FIG. Therefore, the time t7 shown in FIG. 7 does not necessarily coincide with the time t3 shown in FIG. Further, the time t8 shown in FIG. 7 does not necessarily coincide with the time t4 shown in FIG. The same applies to other regions.

  Further, regarding the turn-off times of the areas 1 and 2 of the backlight, t9 and t10 in FIG. 7 do not necessarily match t5 and t6 in FIG. The same applies to other regions.

  In this way, in the conventional display device, the time of turning on or off the backlight was fixed, whereas in the display device of the present invention, by adjusting the phase of the backlight according to the lighting rate, It is possible to always minimize moving image blur and to obtain a good moving image display quality.

  In the above, the relationship between the lighting rate and phase in the backlight intermittent lighting drive and the blurring of the moving image is described, and then the moving image blurring is performed by appropriately controlling the phase according to the lighting rate, which is a feature of the display device of the present invention. A description has been given of a method of driving a backlight that can minimize the above.

  Next, an embodiment of the display device of the present invention that can realize the driving method of the backlight will be described.

  FIG. 8 is a configuration diagram of a display device for explaining the first embodiment of the present invention. This display device is a display device for information equipment such as a television receiver, a PC (personal computer), a mobile phone, and the like, and is typified by a liquid crystal display device having a function of receiving and displaying various video data as input. Is.

  The display device includes a display panel 8010, a panel control unit 8020, a video feature extraction unit 8030, a video-linked luminance adjustment unit 8040, an intermittent lighting luminance adjustment unit 8050, a lighting rate calculation unit 8060, a phase calculation unit 8070, and a backlight control signal generation unit. 8080 and a backlight 8090 are provided. The display device receives a synchronization signal 8001 and video data 8002 as inputs from an external device (not shown). The synchronization signal 8001 is, for example, a vertical synchronization signal that defines one frame period (a period for displaying one screen) of the video data 8002, a horizontal synchronization signal that defines a horizontal scanning period (a period for displaying one line), and video. It consists of a data valid period signal that defines the valid period of data, a reference clock signal synchronized with video data, and the like.

  The display panel 8010 has a function of displaying an image corresponding to input data. For example, the display panel 8010 arranges liquid crystal display elements whose transmittance can be individually controlled in a matrix of M columns × N rows as pixels, and controls the transmitted light from the backlight 8090 for each pixel to display an image. A liquid crystal display panel for display can be applied.

  The panel control unit 8020 receives the synchronization signal 8001 and the video data 8002 as inputs, generates various panel control signals 8021 for controlling the display panel 8010 from these signals, and allows the display panel 8010 to perform appropriate display. It has a function to control. The video feature extraction unit 8030 has a function of receiving the synchronization signal 8001 and the video data 8002 as inputs and extracting various feature amounts 8031 of the video data 8002.

  The various feature amounts 8031 include, for example, the maximum luminance (gradation), minimum luminance (gradation), average luminance (gradation), frequency distribution (histogram) of luminance (gradation), and luminance (gradation) of each frame. Spatial distribution, color, presence / absence of movement, magnitude of movement, etc.

  FIG. 9 is a diagram illustrating a configuration example of the video feature extraction unit 8030 in FIG. 8 for explaining the first embodiment of the present invention. The configuration of the video feature extraction unit in FIG. 10 for explaining the configuration of the second embodiment described later, FIG. 12 for explaining the configuration of the third embodiment, and FIG. 13 for explaining the configuration of the fourth embodiment is the same. Repetitive description will not be given in each embodiment described later. In FIG. 9, the video feature extraction unit 8030 includes, for example, a maximum gradation measurement unit 13010, an average gradation calculation unit 13020, a minimum gradation measurement unit 13030, a frequency distribution generation unit 13040, a tone measurement unit 13050, A motion measuring unit 13060 and a frame memory 13070 are provided.

  Maximum gradation measuring section 13010 measures the maximum gradation value included in each frame of video data 8002 and outputs the maximum gradation value 13011. The average gradation calculation unit 13020 calculates an average value of gradations included in each frame of the video data 8002 and outputs the average value as an average gradation value 13021. The minimum gradation measurement unit 13030 measures the minimum gradation value included in each frame of the video data 8002 and outputs the minimum gradation value 13031.

  The frequency distribution generation unit 13040 measures the number of pixels included in each frame for each gradation of the video data 8002 and outputs it as a frequency distribution (histogram) 13041. The color tone measuring unit 13050 measures the color tone of each frame and outputs it as color tone information 13051. The color tone information is an index representing the characteristics of an image, for example, an image having a reddish color or an image having a dark green color. For example, the tone information can be calculated by a method of generating a histogram for each RGB color and calculating the balance of each RGB color based on the histogram. The frame memory 13070 holds and delays the video data 8002 for a specific time, for example, one frame. For example, 13071 is video data one frame before.

  The motion measuring unit 13060 compares the video data 8003 and the video data 13071 one frame before, and outputs the presence / absence of motion and the magnitude of motion as motion information 13061. The video feature extraction unit 8030 may include only a part of these, or may have a function of extracting other features of video data. The various feature amounts 8031 include the maximum gradation value 13011, the average gradation value 13021, the minimum gradation value 13031, the frequency distribution 13041, the tone information 13051, the motion information 13061, and the like.

  In addition to measuring the various feature quantities on the entire screen, the screen may be divided into small areas and various feature quantities may be extracted for each of the small areas. By adopting such a configuration, it is possible to further obtain two-dimensional characteristics of the video data (for example, a luminance distribution degree such that the upper part of the screen is brighter and gradually becomes darker toward the lower part of the screen). By utilizing these two-dimensional features, the brightness of the corresponding backlight area is controlled in more detail (in the above example, the backlight area at the top of the screen is increased in brightness and the backlight at the bottom of the screen is The brightness of the light area can be reduced), which is useful information for high image quality and low power consumption. The synchronization signal 8001 is used to identify each frame break or to measure a position on an image in calculating each feature value.

  The video-linked luminance adjustment unit 8040 calculates a lighting rate 8041 for video-linked luminance adjustment for adjusting the luminance of the backlight 8090 according to the video from the feature value 8031 extracted by the video feature extraction unit 8030. For example, the average luminance of the video can be used as the feature amount 8031 for adjusting the luminance of the backlight. For example, by performing control such as lowering the backlight luminance in a frame with a high average luminance (ie, bright), and increasing the luminance of the backlight 8090 in a frame with a low average luminance (ie, dark), It is possible to increase the contrast of the displayed video and obtain a good image quality. Of course, in calculating the lighting rate 8041, features other than the average luminance may be used, or a plurality of features may be used in combination.

  The intermittent lighting luminance adjusting unit 8050 calculates a luminance serving as a reference when the backlight 8090 is intermittently driven, and outputs a lighting rate 8051 for backlight intermittent lighting. The external setting luminance signal 8003 is input from an external device (not shown) and is luminance information of the display device set by the external device. For example, in order to improve the convenience for the user, it can be assumed that the brightness level of the display device can be selected according to the user's preference. When the display device is configured as described above, the brightness level selected by the user corresponds to the externally set luminance signal 8003. The above function can be realized by configuring the display device so that the externally set luminance signal 8003 is reflected in the luminance adjustment of the backlight 8090. Specifically, the externally set luminance signal 8003 is factored into the calculation of the combined lighting rate 8061 in the lighting rate calculation unit 8060.

  Alternatively, for example, the display device is provided with an optical sensor that measures the brightness of the surrounding environment where the display device is installed, and the brightness level of the display device is set based on the ambient brightness information obtained by the optical sensor. It can be assumed that it is configured to automatically control so that the image is easy to see. When the display device is configured as described above, ambient brightness information obtained by the optical sensor corresponds to the externally set luminance signal 8003. The above function can be realized by configuring the display device so that the externally set luminance signal 8003 is reflected in the luminance adjustment of the backlight 8090. Specifically, the externally set luminance signal 8003 is factored into the combined lighting rate 8061 calculation by the lighting rate calculation unit 8060.

  The lighting rate calculation unit 8060 comprehensively calculates the luminance required for the backlight 8090 from the lighting rate 8041 for adjusting the video-linked luminance, the lighting rate 8051 for driving the backlight intermittent lighting, and the externally set luminance signal 8003. And a combined lighting rate 8061 to turn on the backlight 8090 to obtain the luminance is calculated. Specifically, for example, after calculating the lighting rate for external setting from the externally set luminance signal 8003, the lighting rate 8041 for adjusting the video-linked luminance, the lighting rate 8051 for driving the backlight intermittent lighting, and the external A result obtained by multiplying all of the setting lighting rates can be a combined lighting rate 8061.

  The phase calculation unit 8070 calculates and outputs the optimum phase 8071 of the backlight 8090 from the combined lighting rate 8061. For the calculation of the optimum phase 8071, characteristic information as illustrated in FIG. 5 is used.

  Specifically, the phase calculation unit 8070 prepares, for example, the lighting rate-optimum phase characteristic illustrated in FIG. 5 as a lookup table, and the combined lighting rate 8061 calculated by the lighting rate calculation unit 8060 is prepared. The optimum phase 8071 can be obtained by referring to the lookup table. Alternatively, the phase calculation unit 8070 may be configured to approximate the characteristics of the lighting rate-optimum phase as a function of the lighting rate, and obtain the optimum phase 8071 for the combined lighting rate 8061 by calculating the function formula. .

  The backlight control signal generation unit 8080 generates and outputs a backlight control signal 8081 for each region of the backlight 8090 from the synchronization signal 8001, the combined lighting rate 8061, the optimum phase 8071, and the write line information 8022. . The write line information 8022 is, for example, a counter value for measuring how many lines on the display panel 8010 have been written.

  The backlight control signal generation unit 8080 measures the writing line time of the display panel 8010 based on the writing line information 8022, and the time defined by the optimum phase 8071 from the time when the writing of the line belonging to a certain backlight area is completed. The control signal 8081 for turning on the backlight area is generated and output after waiting for only the same time. Then, after turning on the backlight area for a time defined by the combined lighting rate 8061, a control signal 8081 is generated and output to turn off the backlight area. By performing the series of processes including display data writing, standby, lighting, and extinguishing individually for each backlight region, intermittent lighting driving of the backlight 8090 can be realized.

  The backlight 8090 has a function of illuminating the display panel. As described above, for example, a cold cathode tube (CCFL), a hot cathode tube (HCFL), a light emitting diode (LED), or the like can be used.

  The first embodiment of the display device to which the present invention is applied has been described with reference to FIG. By configuring the display device in this manner, the backlight intermittent lighting drive as shown in FIG. 4 can be realized, and a good image quality with reduced moving image blur can be obtained. Next, the configuration of the display device according to the second embodiment of the present invention will be described with reference to FIGS. 9 and 10.

  FIG. 10 is a configuration diagram of a display device according to the second embodiment of the present invention. The display device according to the second embodiment is obtained by adding an internally set brightness adjusting unit 9100 to the configuration of the first embodiment shown in FIG. The other points are almost the same as the configuration shown in FIG. In FIG. 9, an internally set brightness adjustment unit 9100 outputs internally set brightness adjustment information 9101 for performing brightness adjustment designated in advance within the display device. For example, a multicolor light source other than a white light source can be used for the backlight 9090. For example, when the light source of the backlight 9090 is an LED, LEDs of three primary colors of red, green, and blue can be used instead of using a white LED. By using such a multicolor light source, there is an advantage that the range of colors that can be displayed can be improved compared to the case of using a white light source. However, in order to color white with the three primary color LEDs, it is necessary to mix the light of the three color LEDs. At this time, the white hue (color temperature) obtained by mixing the three colors of light varies depending on the intensity of each color.

  That is, in order to obtain a desired color temperature, it is necessary to individually adjust the emission intensity of red, green, and blue LEDs for each color. For example, it is necessary to control the emission intensity of red, green, and blue to be 3: 2: 1. The internal setting luminance adjustment unit 9100 realizes a mechanism such as this color temperature adjustment.

  In order to realize the internally set luminance as described above by the control signal by the PWM method, it is necessary to make the lighting rate different for each color. In this case, the internally set luminance information 9101 is a lighting rate for each color. In the configuration example shown in FIG. 8, the simplest method of adding such control is to first prepare the combined lighting rate 8061 for each color and make it possible to calculate it independently, and then with an internally set brightness adjustment unit. When the calculated lighting rate for each color for internally set brightness adjustment is input to the lighting rate calculation unit 8060 and the combined lighting rate 8061 is calculated for each color, the lighting rate 8041 for video-linked brightness adjustment, The backlight 8090 is intermittently driven for each color by multiplying the lighting rate 8051 for intermittent lighting of the backlight, the lighting rate for external setting, and the lighting rate for each color for adjusting the internal setting brightness. That is.

  However, there is a problem with the configuration as described above. This problem is that the intermittent lighting rate of the backlight 8090 may be different for each color because the combined lighting rate is calculated for each color and individually controlled. That the intermittent lighting rate of the backlight 8090 is different for each color results in that the width of the moving image blur is different for each color. For example, when a video pattern such as that shown in FIG. 1 is displayed, a false color that is not supposed to be on the video data is perceived in the outline of the moving display object when the video pattern as shown in FIG. 1 is displayed. , Causing image quality degradation.

  In order to avoid the above-described problem, as shown in FIG. 10, the lighting rate for internally set brightness adjustment for the purpose of color adjustment of a multicolor light source is made independent of the lighting rate calculation unit 8060. It is preferable to configure so that the calculation of the combined lighting rate 8061 is not affected.

  Next, an example of a method for realizing the internally set brightness adjustment will be described. FIG. 11 is a timing chart showing an example of the backlight control signal 9081 for performing the internally set luminance adjustment shown in the configuration example shown in FIG. FIG. 11 also shows an example in which the backlight control signal is implemented by the PWM method.

  The control signal A is an example in which the internally set brightness adjustment is 100%. All the lights are turned on for the period specified by the combined lighting rate. The control signal B is an example in which the internally set brightness adjustment is 30%. The period defined by the combined lighting rate is further divided into a plurality of parts, and lighting and extinguishing are repeated in units of the divided small periods (the small periods are called internal cycles). Further, the lighting period is controlled to be 30% in the internal cycle.

  If the backlight control signal 9081 is configured in this way, the problem like the false color does not occur. This is because human vision cannot perceive blinking performed in such a minute time as in the internal cycle, but perceives it to emit light continuously for a period defined by the combined lighting rate. . At this time, the size of the moving image blur is the same as when the internally set brightness adjustment is set to 100%. That is, the internally set brightness adjustment does not affect the magnitude of the moving image blur, and no false color occurs. On the other hand, even though the blinking of the internal period cannot be perceived, the total amount of light incident on the retina is reduced, so that the perceived brightness is reduced and the demand for brightness adjustment can be satisfied.

  The control signal C is an example in which the internally set brightness adjustment is 60%. Similar to the control signal B, it can be realized by controlling the ratio of the lighting time in the internal period to be 60%. The control signal D is an example different from the control signal B when the internally set brightness adjustment is 30%. Rather than repeating lighting and extinction on the basis of a specific cycle, control is performed so that the proportion of the lighting period occupying within the period defined by the composite lighting rate is 30% while performing lighting and extinction randomly. It will be realized.

  By controlling in this way, it is possible to prevent the backlight areas from being simultaneously turned on and off at the same time, to distribute the time when the current flows, and to prevent a large current from flowing instantaneously through the circuit, as well as electromagnetic noise. It can be expected that the effect of spreading the frequency spectrum is obtained. The configuration of the second embodiment of the display device to which the present invention is applied has been described with reference to FIGS. 10 and 11. Next, the configuration of the display device according to the third embodiment of the present invention will be described with reference to FIG.

  FIG. 12 is a configuration diagram of the display apparatus according to the third embodiment of the present invention. In the third embodiment, the data conversion unit 11110 is added to the configuration example shown in FIG. 10, and the externally set luminance signal 11003 is input to the data conversion unit 11110 in addition to the lighting rate calculation unit 11060. Different. The other points are almost the same as the configuration shown in FIG.

  The data conversion unit 11110 has a function of performing various data conversion on the video data 11002 based on the video data feature amount 11030 extracted by the video feature extraction unit 11030 and the externally set luminance signal 11003 and outputting the data. Reference numeral 11112 indicates video data subjected to the data conversion, and reference numeral 11111 indicates a synchronization signal synchronized with the video data subjected to the data conversion.

  As an example of the data conversion, there is a data conversion method for the purpose of reducing power consumption. The operation of the data conversion method is as follows, for example. In the display device, when a certain luminance B1 is displayed, assuming that the backlight has the luminance B11 in the reference state and the display panel has the transmittance Tr1, the relationship B1 = B11 × Tr1 is established.

  On the other hand, in the data conversion method, the lighting rate of the backlight 11090 is made lower than that in the reference state to lower the backlight luminance B12 (B11> B12), while the transmittance Tr2 of the display panel is made higher than usual. The display data is converted as (Tr1 <Tr2). The luminance observed in this case is B2 = B12 × Tr2. Here, if the backlight luminance B12 and the transmittance Tr2 are appropriately adjusted, luminance equivalent to the reference state can be realized (that is, B1 = B2).

  In the processing, the video-linked brightness adjustment unit 11040 adjusts the backlight brightness B12 using the feature amount 11031 of the video data. In addition, the data conversion unit 11110 converts the video data 11002 so that an appropriate transmittance Tr2 is obtained using the feature amount 11031 of the video data.

  In the above-described method, the luminance of the backlight 11090 can be lowered as compared with the reference state as described above, so that the power consumption of the backlight can be greatly reduced, and the effect of saving power of the display device is high. Alternatively, as described with reference to FIG. 8, for example, an optical sensor that measures the ambient brightness of the display device is provided, and ambient brightness information obtained by the optical sensor is used as the externally set luminance signal 8003. When the brightness level of the backlight 11090 is automatically controlled so as to be easily seen by the user, not only the brightness of the backlight 11090 is adjusted according to the ambient brightness information obtained by the light sensor, but also the viewing is easier to see. A method of converting the video data 11002 so as to be displayed can be applied. The configuration of the third embodiment of the display device to which the present invention is applied has been described with reference to FIG. Next, the configuration of the display device according to the fourth embodiment of the present invention will be described with reference to FIG.

  In general, the process of extracting feature amounts from video data and the process of converting video data as described with reference to FIG. 12 are complicated, and it takes considerable cost to realize this. For this reason, adding the feature extraction processing or the like to a display device configured with minimum necessary components such as a display panel and a backlight, for example, causes a significant cost increase of the display device. Therefore, a configuration method of a display device that suppresses cost increase while applying the backlight intermittent lighting drive of the present invention will be described below.

  FIG. 13 is a configuration diagram of a display device according to Embodiment 4 of the present invention. The fourth embodiment is divided into a signal processing device 12200 and a display device 12000 based on the configuration example shown in FIG. 12, and some of the functions of the display device in FIG. 12 are moved to the signal processing device 12200 side. Is. The display device 12000 receives, from the signal processing device 12200, the combined lighting rate 12121, the video data 12112 changed by the data converter, and the synchronization signal 12111 synchronized with the video data.

  The signal processing device 12200 has a function (not shown) for performing various signal processing on the video data 12002. The various signal processing is various video signal processing such as color tone adjustment processing, enlargement / reduction processing, interlace / progressive conversion processing, OSD (on-screen display) processing, etc. Information terminals are generally already installed. In many cases, the signal processing device 12200 that performs these processes already has the video feature extraction function described above.

  In other words, by adopting a configuration in which the above-described video feature extraction and data conversion processing are performed in the signal processing device, the cost of the display system is relatively lower than a configuration in which similar functions are completely added to the display device. It becomes possible to do. That is, the signal processing device 12200 is configured to include a video feature extraction unit 12030, a video-linked luminance adjustment unit 12040, a lighting rate calculation unit 12120, and a data conversion unit 12110.

  The lighting rate calculation unit 12120 calculates a luminance required for the backlight 12090 of the display device 12000 from the lighting rate 12041 for adjusting the video-linked luminance and the externally set luminance signal 12003, and obtains the backlight to obtain the luminance. A combined lighting rate 12121 for lighting 12090 is calculated. At this time, the backlight intermittent lighting drive is a function that the display device 12000 is in charge of, so the signal processing device 12200 does not need to be aware of it. Therefore, it is not necessary to incorporate the lighting rate 12051 for driving the backlight intermittent lighting into the calculation of the combined lighting rate 12121. On the other hand, the lighting rate calculation unit 12060 provided on the display device 12000 side calculates the final combined lighting rate from the combined lighting rate 12121 input from the signal processing device 12200 and the lighting rate 12051 for backlight intermittent lighting driving. 12061 is calculated.

  Here, the signal format of the combined lighting rate 12121 input to the display device 12000 uses a digital format that digitally expresses a numerical value, a PWM format as described above, an analog method using a voltage value or a current value, or the like. be able to.

  The other points are almost the same as the configuration shown in FIG. With the configuration as shown in FIG. 12, the display device 12000 can be provided at low cost. In the above, one structural example of the display device to which the present invention is applied has been described with reference to FIG.

  As described above, according to the display device of the present invention, the function of intermittent backlight driving for the purpose of improving the blurring of moving images is provided, and further, for the purpose of improving the contrast, etc. Even when the lighting rate is fluctuated, it is possible to always obtain a good moving image display quality with little moving image blurring by adjusting the phase appropriately and always lighting the backlight with the optimum phase according to the lighting rate.

  Next, a fifth embodiment of the present invention will be described. Up to the above-described embodiments, the method for realizing the intermittent lighting control in the display device including the backlight divided into a plurality of regions has been mainly described. In the present embodiment, a method for realizing a display device in which the intermittent lighting control is combined with local dimming control will be described.

  Here, the local dimming control is a backlight divided into a plurality of regions, and in the display device of the present invention provided with a backlight capable of controlling the luminance for each region, each region of the backlight. Is a technique for individually controlling the brightness of the video according to the characteristics of the input video data.

  As the feature, for example, the maximum gradation of one screen of the input video data can be used. For example, when the input video data does not include high gradation, it is not necessary to shine the backlight to the maximum, and the backlight brightness can be reduced (dimmed) to the extent that a necessary and sufficient amount of light can be obtained. If the brightness of the backlight is reduced, the power consumption can be reduced accordingly. That is, power consumption can be reduced when the maximum gradation value included in the input video data of the entire screen is smaller than the maximum gradation value that can be displayed on the display device. At this time, the degree of reduction in power consumption depends on the maximum gradation of the input video data of the entire screen. The effect of reducing power consumption increases as the maximum gradation of the entire screen is lower.

  Hereinafter, in the present specification, such a method of controlling the luminance of the backlight based on the characteristics of the input video data of the entire screen is referred to as overall dimming.

  Furthermore, the concept of the whole dimming can be expanded, the backlight is divided into a plurality of areas, and the control can be performed for each of the backlight areas, not the entire screen. In other words, the brightness of each area of the backlight is not determined based on the maximum gradation value of the entire screen of the input video data, but the maximum gradation value included in the input video data in each area, that is, by area. It is configured to be determined by the maximum gradation value.

  When the maximum gradation value for each area is smaller than the maximum gradation value that can be displayed on the display device, it is not necessary to shine the area of the backlight to the maximum, and the backlight can be obtained to the extent that a sufficient amount of light can be obtained. It is possible to reduce the brightness of the region (dimming locally). If the luminance of the backlight area is reduced, power consumption can be reduced accordingly.

  In general, the maximum gradation for each region of input video data (except for a special case where a uniform gradation is displayed on the entire screen) is often different for each region. For example, the distribution of gradation of general input video data such as natural images is not uniform over the entire screen. Locally, there are areas that include high gradations (ie, the maximum gradation for each area is large), and other areas that are composed only of low gradations (that is, the maximum gradation for each area is small). .

  When displaying such input video data, controlling the brightness of each area of the backlight individually (local dimming) according to the characteristics of each area (for example, maximum gradation value) further reduces power consumption. It is effective for. For example, the relationship between the maximum gradation for each area and the maximum gradation for one entire screen always holds that the maximum gradation for each area ≦ the maximum gradation for one entire screen. For this reason, in determining the luminance of a region with a backlight, the value obtained by the local dimming method is smaller than the value obtained by the overall dimming method. That is, the power consumption of local dimming is smaller than the power consumption of total dimming. In other words, by applying local dimming, the effect of reducing the power consumption of the display device can be enhanced as compared with the case of applying total dimming.

  The local light control is also effective for reducing the luminance and improving the contrast when displaying a black image in a liquid crystal display device, for example. This is due to the following reason. Normally, in a liquid crystal display device, even if it is intended to display a black screen, the light transmitted through the liquid crystal cannot be completely blocked, the light leaks, and the luminance cannot be reduced to 0 (this phenomenon is caused by black floating). It is sometimes said that you do.) However, if the amount of light from the backlight is reduced, the light leakage is naturally reduced, and the luminance during black screen display is also reduced. That is, it is possible to display a black image with no black floating, and to display bright and dark gradations clearly, and the contrast is improved.

  In the above, the concept of the local light control of the backlight in the display apparatus of this invention and its effect were demonstrated. In the above description, the maximum gradation value has been described as an example of the feature of the input video data. However, the feature of the video used for local dimming is not limited to this. Next, an example of the local light control method will be described in more detail with reference to FIGS.

  FIG. 20 is a diagram for explaining the gradation reproduction local dimming method as an example of the local dimming method of the backlight in the display device of the present invention. FIG. 20A is a diagram showing an example of the gradation frequency distribution in a certain area of input video data. The horizontal axis represents gradation, and the vertical axis represents the frequency for each gradation (number of pixels having the gradation). At this time, the backlight for illuminating the area is assumed to be lit at 100% brightness. In the example of FIG. 20A, the maximum value of the gradation of the input video data in the area is Dmax%, and the relationship of Dmax <100 is established. In other words, gradations from Dmax% to 100% are unused gradations (unused gradations). For example, when such video data is input, the gradation of the input video data is multiplied by 100 / Dmax by data conversion.

  FIG. 20B is a gradation frequency distribution of the video data subjected to the data conversion. If this data is used for display as it is, the video will become unnecessarily bright, but the brightness of the original video data can be adjusted by adjusting the brightness of the backlight that illuminates the area (backlight dimming). Can be reproduced. Specifically, the luminance of the backlight that illuminates the area is multiplied by Dmax / 100. FIG. 20C shows a gradation frequency distribution of a display result of video data subjected to the data conversion and the backlight dimming. By the above process, the original input video data shown in FIG. 20A is reproduced. As described above, in the gradation reproduction local dimming method, it is possible to reduce the luminance of the corresponding area of the backlight without changing the image displayed on the display device from the original input video data. Light power consumption can be reduced. However, in the gradation reproduction local dimming method, the power consumption can be reduced when the maximum gradation Dmax of the input video data is smaller than 100%, while the power consumption is reduced when the maximum gradation Dmax is equal to 100%. There is a problem that the effect cannot be obtained.

  As described above, the gradation reproduction local dimming method has been described as an example of the local dimming of the backlight in the display device of the present invention with reference to FIG. Next, another example of the local light control method of the backlight in the display device of the present invention will be described with reference to FIG.

  FIG. 21 is a diagram for explaining a power consumption priority local dimming method, which is an example different from the tone reproduction local dimming method of the backlight local dimming method in the display device of the present invention. Here, the power consumption priority local dimming method is a method that can achieve the power consumption reduction effect even when the maximum gradation Dmax is equal to 100%, unlike the above-described gradation reproduction local dimming method. .

  FIG. 21A is a diagram showing an example of the gradation frequency distribution in a certain area of input video data. The horizontal axis represents gradation, and the vertical axis represents the frequency for each gradation (number of pixels having the gradation). At this time, the backlight for illuminating the area is assumed to be lit at 100% brightness. In the example of FIG. 21A, the maximum value of the gradation of the input video data in the area is 100%. As described above, the gradation reproduction local dimming method cannot obtain the power consumption reduction effect for such input video data. Therefore, in the power consumption priority local dimming method, the loss of some gradation information (color collapse) is allowed and the power consumption is reduced. For example, the degree to which the gradation information is allowed to be lost is determined as the allowable threshold Th. The pixels in the region are arranged in descending order from the highest gradation value, and the Th% th pixel from the top in the frequency is searched. For example, if the number of pixels in the region is 200 and Th = 5, the Th% th pixel is the 10th pixel from the top (= 200 × Th / 100 = 200 × 5 ÷ 100). Next, the gradation of the pixel is set as a threshold gradation Dth. Then, the gradation of the input video data is multiplied by 100 / Dth by data conversion. For gradations that exceed 100% due to the data conversion, for example, an overflow treatment is performed with a gradation value of 100%.

  FIG. 21B is a gradation frequency distribution of the video data subjected to the data conversion. When this data is used for display, the image becomes unnecessarily bright. However, the brightness of the original image data can be adjusted by adjusting the brightness of the backlight that illuminates the area (backlight dimming). Can be almost reproduced. Specifically, the brightness of the backlight that illuminates the area is multiplied by Dth / 100. FIG. 21C shows a gradation frequency distribution of the display result of the video data subjected to the data conversion and the backlight dimming. By the above process, the original input video data shown in FIG. 21A is almost reproduced. However, in the input video data, the gradation of pixels having a gradation larger than the threshold gradation Dth is uniformly Dth%. That is, in the power consumption priority local dimming method, the gradation information of the upper Th% pixels is lost, but on the other hand, the input video that cannot reduce the power consumption in the gradation reproduction local dimming method. Also for data, power consumption can be reduced. The allowable threshold Th is appropriately determined in consideration of the trade-off between image quality degradation due to loss of gradation information and power consumption reduction effect. The power consumption priority local dimming method is suitable for applications in which low power consumption is very important, such as mobile phones. The example of the local dimming method in the display device of the present invention has been described above.

  Next, a method for realizing the local light control will be described with an example. In the following description, an example in which the gradation reproduction local dimming method is mainly employed as the local dimming method will be mainly described, but the power consumption priority local dimming method can also be adopted. The method may be adopted.

  FIG. 14 is a diagram for explaining the concept of local light control of the backlight in the display device of the present invention. In the figure, reference numeral 14000 indicates a display panel, and reference numeral 14001 indicates a backlight. As for the backlight 14001, in the example of FIG. 2, P = 1 and Q = 4, and an example in which the area is divided only in the vertical direction is shown, but in the example shown in FIG. 14, P = 5, Q = 4, and the difference is that the region is also divided in the horizontal direction. However, the above-mentioned number of divisions is an example, and in applying the present invention, the number of divisions is not limited to these examples, and other values may be taken. The display panel 14000 and the backlight 140001 are substantially the same as those described with reference to FIG.

  Reference numeral 14010 indicates an example of input video data input to the display panel. Here, for example, an image that gradually darkens from the bottom of the screen to the top, such as a landscape image of the sky at sunset, is taken as an example.

  In the display device of the present invention, for such a video, the maximum gradation in the area is measured for each area of the input video data in which each area of the backlight is in charge of illumination. In this display device, the maximum gradation for each region and the overall maximum gradation are measured from the input video data.

  The maximum gradation for each area 14020 is an example of the result of measuring the maximum gradation for each area of the input video data in the video data 14010. The ratio is shown when the maximum gradation that can be displayed by the display device is 100%. Hereinafter, in this specification, the gradation value is expressed as a ratio to the maximum gradation that can be displayed by the display device.

  For example, as shown in FIG. 14, the maximum gradation for each area of the area A1 is 0%, and the maximum gradation for each area of the areas A2, A3, and A4 is 20%, 40%, and 60% (values corresponding to ).

  Since the maximum gradation for each area is measured in association with each area of the backlight, the number thereof is measured by P × Q, which is the same as the number of divisions of the backlight.

  The overall maximum gradation (not shown) is the maximum value among the plurality of region-specific maximum gradations 14020. In the example of FIG. 14, 60% of the areas A4 and B4 correspond to the entire maximum gradation.

  When overall dimming is applied to the input video data as described above, for example, the luminance of the backlight in each region is adjusted to 60% based on the overall maximum gradation value (60%).

  On the other hand, when local dimming is applied to similar input video data, for example, the area A1 has a backlight brightness of 0%, and similarly the backlight brightness of the areas A2, A3, and A4 is 20%, 40%. % And 60%. As described above, in the local dimming, it is possible to finely control the light amount of the backlight, and as a result, it is possible to reduce the power consumption of the backlight and consequently the display device.

  Here, the case where the said local light control is applied to the display apparatus provided with the intermittent lighting function of the backlight as demonstrated in Examples 1-4 is considered.

  The simplest method for incorporating local dimming into a display device having an intermittent lighting function is to configure the lighting time of the intermittent lighting to be changed for each region.

  However, in the above configuration, there is a problem that the image quality at the time of moving image display deteriorates. The cause of this problem is that the amount of moving image blur varies from region to region.

  The mechanism of this problem is described below. As described above, in intermittent lighting, the amount of moving image blur becomes smaller as the lighting time is shorter. That is, for example, in a region with a lighting rate of 20% and a region with a lighting rate of 40%, the motion blur is smaller in the region with a lighting rate of 20%. However, as shown in the example shown in FIG. 14, this phenomenon is not preferable when the region A2 having a lighting rate of 20% and the region A3 having a lighting rate of 40% are adjacent to each other. This is because, for example, when a moving object having a size across the area A2 and the area A3 is displayed due to a difference in the size of the moving image blur for each area, a step is perceived in the outline of the object at the boundary between the area A2 and the area A3. This is because a malfunction (deterioration in image quality) occurs. Hereinafter, in the present specification, an example of the defect is referred to as a region step.

  The fifth embodiment of the present invention provides a display device that does not generate the region step even when intermittent lighting and local dimming are combined.

  As described above, the cause of the region step is that the amount of moving image blur differs from region to region. Therefore, in order to solve this problem, the amount of moving image blurring for each region may be the same. That is, even when intermittent lighting and local dimming are combined, the display device may be configured so that the lighting time is the same value in all regions.

  Hereinafter, an example of the operation of the display device of the present invention configured so that the lighting time is set to the same value in all regions in a display device provided with intermittent lighting and local dimming will be described.

  FIG. 15 is an example of a timing chart showing the operation of the display device to which the fifth embodiment of the present invention is applied. The time relationship between the screen scanning of the display panel and the lighting operation of the backlight with respect to the input signal of the display device is illustrated. Since it is almost the same as the example shown in FIG. 6, description of common parts is omitted, and only differences are described.

  In the display device of Example 5, the lighting rate (that is, the lighting time) is common in each area of the backlight, while the amount of light per unit time of the backlight within the lighting time is individually determined for each area. The point of control is different from the other embodiments described so far.

  As described above, the display device of the present invention has an intermittent lighting function, and after writing the data of the line group of the display panel corresponding to each area of the backlight, until the display element of the pixel of the line sufficiently responds. After waiting for a predetermined time, the backlight is turned on.

  Region A1, region A2, region A3, and region A4 shown in FIG. 15 correspond to the backlight region shown in FIG. 14, and represent the state of each lighting operation. In the example of FIG. 6, a frame starts at time t0, and the display panel is sequentially scanned from one line. The scanning of the line corresponding to the backlight area A1 is completed at time t1, and the scanning of the line corresponding to the backlight area A2 is completed at time t2. Thereafter, scanning is similarly continued until the N line is reached.

  The backlight in the area A1 starts to turn on at time t11 when the time specified by the phase has elapsed from time t1, and turns off at time t13 when the lighting time specified by the lighting rate has elapsed from time t11. Similarly, the backlight in the area A2 starts to be turned on at time t12 when the time specified by the phase has elapsed from time t2, and is turned off at time t14 when the lighting time specified by the lighting rate has elapsed from time t12. Thereafter, the lighting / extinguishing operation is continued until the area A4 is reached.

  As described above, in order to prevent the occurrence of gradation steps, the lighting rate needs to be the same value in all regions. However, by itself, the luminance of all the regions becomes equal, so that luminance control for each region (that is, local dimming) cannot be realized. Therefore, it is utilized that the luminance of the backlight is the product of the lighting time and the amount of light per unit time. Even if the lighting time is the same, the luminance increases as the amount of light per unit time is increased, and conversely, the luminance decreases as the amount of light per unit time is decreased. That is, if the amount of light per unit time is controlled for each region, the luminance control for each region can be performed while keeping the lighting time the same. That is, it is possible to obtain both effects of improving moving image performance by intermittent lighting and reducing power consumption by local dimming while preventing occurrence of gradation steps.

  Here, as described above, the lighting rate is common to the entire backlight. Therefore, in determining the lighting rate, it is necessary to determine in consideration of the characteristics of the entire screen of the input video data. Specifically, it is preferable to use the maximum gradation value of the entire screen of the input video data. Control is performed so that the lighting rate decreases as the maximum gradation of the entire screen is smaller. For example, in the input display data 14010 shown in FIG. 14, the maximum gradation of one screen is 60%, so that the lighting rates of the areas A1 to A4 are all 60% and the same. That is, the lighting time is also the same.

  On the other hand, the amount of light per unit time within the lighting time is different for each region. Here, the amount of light per unit time determined for each area needs to be determined in consideration of the characteristics of the video data included in the corresponding area of the input video data in addition to the characteristics of the entire screen. Specifically, it is preferable to use the maximum gradation value for each area of the input video data. Control is performed such that the smaller the maximum gradation value for each region, the smaller the amount of light per unit time.

  Further, the amount of light per unit time in each area is calculated from the backlight luminance target value for each area measured from the input video data and the lighting rate. For example, the amount of light per unit time can be calculated by the equation: target luminance value ÷ lighting rate. Here, the target luminance value is obtained from, for example, the maximum gradation value for each region. Also, the lighting rate is obtained from the maximum gradation value of the entire screen as described above, for example.

  For example, in the input display data 14010 shown in FIG. 14, the region-specific maximum gradation value is 0% in the region A1, and the region-specific maximum gradations in the regions A2, A3, and A4 are 20% and 40%, respectively. %, 60%. The maximum gradation of the entire screen is 60%.

  Therefore, for example, when displaying the input display data 14010 shown in FIG. 14, the amount of light per unit time of the backlight in the area A1 is set to 0%. This is because the maximum gradation for each area of the area A1 is 0% and the maximum gradation for the entire screen is 60%, so 0% ÷ 60% = 0%. Similarly, the light amounts of the areas A2, A3, and A4 are 33% (= 20% ÷ 60%), 66% (= 40% ÷ 60%), and 100% (= 60% ÷ 60%), respectively.

  At this time, since the lighting rate of the area A1 is 60% and the light amount per unit time is 0%, the final backlight luminance is 60% × 0% = 0%. Similarly, the backlight luminance of the region A2 is 60% × 33% = 30%, the backlight luminance of the region A3 is 60% × 66% = 40%, and the backlight luminance of the region A3 is 60% × 100% = 60%.

  In this way, by controlling both the lighting rate and the amount of light per unit time, the backlight luminance value for each region shown in the example of FIG. 14 can be realized.

  The operation of the display device of the present invention has been described above. As described above, the display device according to the present invention shares the lighting rate (that is, the lighting time) in each region of the backlight, and separately determines the light amount per unit time of the backlight within the lighting time for each region. Thus, even when intermittent lighting and local dimming are combined, the region level difference is not generated.

  Next, an example of a method for configuring a display device to which the fifth embodiment of the present invention is applied will be described.

  FIG. 16 is a diagram showing the configuration of a display device to which the fifth embodiment of the present invention is applied. Since it is almost the same as the third embodiment shown in FIG. 12, the description of the common parts is omitted, and only the differences are described.

  Compared to the example shown in FIG. 12, the video feature extraction unit 16030 is provided with an overall video feature extraction unit 16130 and a regional video feature extraction unit 16140, and an overall video-linked luminance adjustment unit 16040 and regional video-linked luminance adjustment. The main difference is that the unit 16150 and the area-specific light amount calculation unit 16160 are provided.

  The entire video feature extraction unit 16130 extracts and outputs the entire video feature quantity 16131 of the screen from the video of one screen (one frame) of the input video data 16002. For example, as the entire video feature amount 16131, as described above, the maximum value of the gradations included in one entire screen can be used. The overall video interlocking luminance adjustment unit 16040 calculates a lighting rate 16041 for overall video interlocking luminance adjustment for adjusting the luminance of the backlight 16090 from the overall video feature quantity 16131 extracted by the overall video feature extraction unit 16130.

  The lighting rate calculation unit 16060 comprehensively calculates the luminance required for the backlight 16090 from the lighting rate 16041 for overall video-linked luminance adjustment, the lighting rate 16051 for driving backlight intermittent lighting, and the externally set luminance signal 16003. In order to obtain the brightness, a combined lighting rate 16061 that is a reference for lighting the backlight 16090 is calculated. The phase calculation unit 16070 calculates and outputs the optimum phase 16071 of the backlight 16090 from the combined lighting rate 16061. For the calculation of the optimum phase 16071, characteristic information as illustrated in FIG. 5 is used.

  The area-specific video feature extraction unit 16410 divides the video for one screen (one frame) of the input video data 16002 into a plurality of areas, and extracts the feature amount of the video included in the area for each area. Furthermore, it outputs as the image feature amount 16141 classified by area. Here, the region is preferably associated with a backlight region divided into a plurality of regions. As the region-specific image feature quantity 16141, for example, the maximum value of the gradation included in the region of the image data can be used.

  A region-specific video-linked luminance adjustment unit 16150 is turned on for adjusting the luminance of the region-based video-linked luminance for adjusting the luminance of the backlight 16090 for each region from the region-specific video feature amount 16141 extracted by the region-specific video feature extraction unit 16410. The rate 16151 is calculated. For example, as the entire video feature amount 16131, as described above, the maximum value of the gradations included in one entire screen can be used.

  The area-specific light amount calculation unit 16160 calculates the unit time for each area for each area of the backlight 16090 from the combined lighting rate 16061, the lighting rate 16151 for adjusting the image-linked luminance for each region, and the internally set luminance adjustment information 16101. The amount of light 16161 per unit is calculated. In calculating the light quantity 16161 per unit time for each area, for example, the calculation is performed based on the method described above with reference to FIGS.

  The backlight control signal generation unit 16080 calculates the luminance of the backlight 16090 for each region from the combined lighting rate 16061, the optimum phase 16071, the light quantity 16161 per unit time for each region, the synchronization signal 16111, and the write line information 16022. A backlight control signal 16090 is generated and output.

  The backlight control signal 16090 waits for a time defined by the optimum phase 16071 from the time when writing of a line belonging to a certain backlight area is completed, and then turns on the backlight area and is defined by a composite lighting rate 16061. The backlight area is turned on after the backlight area is turned on, and the backlight area is turned off. Further, the backlight control signal 16090 indicates that the area of the backlight 16090 is turned on during the lighting time. The light is emitted with the light amount defined by the light amount 16161 per unit time for each region.

  The configuration example of the display device to which the present invention is applied has been described above. Next, a backlight driving method for adjusting the light amount of the backlight per unit time described above for each region will be described with an example.

  FIG. 17 is a timing chart showing an example of a backlight driving method for adjusting the amount of light of the backlight per unit time for each region. Here, the input signal of the display device is taken as a representative vertical synchronization signal, and an example in which an LED is used as the light emitting element constituting the backlight is taken up. An LED is a light-emitting element that emits light when a current is passed. Even if the current value is constant, the amount of light emission, that is, the brightness, can be adjusted by adjusting the length of time that the current is passed as described above. Possible (PWM format).

  FIG. 17 illustrates the temporal relationship between the backlight drive current waveform and the input signal of the display device. The horizontal axis shows the passage of time. The vertical axis of the vertical synchronization signal is the voltage value, and the vertical axis of the backlight driving current waveform is the current value. In the example of FIG. 17, the example of the brightness adjustment method in the backlight is configured such that the current of the current value I flows when the backlight emits light and the current value is 0 when the backlight is turned off. The lighting rate obtained from the highest gradation value of the entire screen is 60%. In this case, in accordance with the above-described intermittent lighting control method, for example, the backlight is turned on for a period corresponding to 60% of one frame period. This is common to all areas regardless of the maximum gradation value for each area. At this time, the backlight drive waveform when the light amount per unit time is set to 100% is such that the current I flows for a time corresponding to 100% of the lighting time. That is, the current I is allowed to flow during the lighting time. Alternatively, for example, in the backlight driving waveform when the amount of light per unit time is to be 0%, the current I is allowed to flow for a time corresponding to 0% of the lighting time. That is, no current flows during the lighting time. Alternatively, for example, when it is desired to set the amount of light per unit time to 66%, the drive waveform of the backlight is such that the current I flows only for a time corresponding to 66% of the lighting time. In realizing this control, for example, a basic period is set up so that a reference period for turning on / off operation is provided, and a fixed ratio (66% in this case) of the period is turned on. It can comprise so that it may repeat with the said period. Similarly, for example, when the amount of light per unit time is desired to be 33%, the current I is allowed to flow for a time corresponding to 33% of the lighting time. This method can also be used when the amount of light per unit time takes other values.

  FIG. 18 is a timing chart showing an example different from FIG. 17 of the backlight driving method for adjusting the light amount of the backlight per unit time for each region.

  Since it is almost the same as the example of the driving method shown in FIG. In the example of FIG. 17, the method of repeating the reference waveform at a predetermined period when adjusting the light amount has been described. However, in the example of FIG. 18, the reference period is not provided and the light is turned on / off randomly. The points of construction are different. However, also in this case, for example, when it is desired to set the amount of light per unit time to 66%, the total of the lighting times that are lighted randomly (the current I flows) corresponds to 66% of the lighting time. Similarly, for example, when it is desired to set the light amount per unit time to 33%, the total lighting time for lighting randomly (flowing current I) is configured to correspond to 33% of the lighting time. This method can also be used when the amount of light per unit time takes other values. By controlling in this way, it is possible to prevent the backlight areas from being simultaneously turned on and off at the same time, to distribute the time when the current flows, and to prevent a large current from flowing instantaneously through the circuit, as well as electromagnetic noise. It can be expected that the effect of spreading the frequency spectrum is obtained.

  FIG. 19 is a timing chart showing another example of the backlight driving method for adjusting the light amount of the backlight per unit time for each region, different from FIGS. 17 and 18. Since it is almost the same as the example of the driving method shown in FIG. In the example of FIG. 17, the PWM method has been described in which the amount of light of the backlight is adjusted by adjusting the length of the current flowing time while keeping the current value I when turning on the backlight constant. The example of FIG. 19 is different in that a current dimming method is adopted in which the amount of light of the backlight is adjusted by adjusting the current value while keeping the current flowing time constant. At this time, the backlight drive waveform when the amount of light per unit time is set to 100% is such that the current I flows during the lighting time. Alternatively, for example, the backlight driving waveform when the light amount per unit time is set to 0% is such that a current corresponding to 0% of the current I flows during the lighting time. That is, no current flows during the lighting time. Alternatively, for example, when the light amount per unit time is set to 66%, the driving waveform of the backlight is such that a current corresponding to 66% of the current I flows during the lighting time. Similarly, for example, when the amount of light per unit time is desired to be 33%, a current corresponding to 33% of the current I is allowed to flow during the lighting time. This method can be used even when the light quantity takes other values. Here, for the sake of simplification of description, the description has been made on the assumption that the light emitting element has a linear characteristic with respect to the amount of current. If the relationship between the amount of light emitted from the light emitting element and the amount of emitted light is not linear, it is necessary to select a current value so that an appropriate amount of light can be obtained.

  As described above, according to the display device of the present invention, the function of backlight intermittent lighting drive for the purpose of improving moving image blur is provided, and even when the lighting rate is changed according to the content of the video data, Moving image blur can be reduced by adjusting the phase as appropriate and always lighting the backlight at the optimum phase according to the lighting rate. Furthermore, even when combined with local dimming control that controls the brightness of each backlight area according to the content of the video data, etc. for the purpose of reducing power consumption, etc., good display quality without causing area steps Can be obtained.

It is a figure which shows the example of the moving image blurring which generate | occur | produces in a hold type display apparatus. It is a figure which shows the structural example of the display panel and backlight in the display apparatus to which this invention is applied. It is a figure explaining the principle of the moving image blur reduction in a backlight intermittent lighting drive. It is a figure explaining the influence which the lighting standby time in a backlight intermittent lighting drive has on a moving image blur. It is a figure which shows the example of the relationship between the lighting rate of a backlight and the optimal phase in backlight intermittent lighting drive. It is an example of the timing chart which shows operation | movement of the display apparatus to which this invention is applied. It is an example different from FIG. 6 of the timing chart which shows operation | movement of the display apparatus to which this invention is applied. It is a block diagram of the display apparatus of Example 1 of this invention. It is a figure which shows the example of 1 structure of the image | video feature extraction part in FIG. 8 explaining Example 1 of this invention. It is a block diagram of the display apparatus of Example 2 of this invention. It is the timing chart which showed the example of the backlight control signal in the display apparatus of Example 3 of this invention. It is a block diagram of the display apparatus of Example 3 of this invention. It is a block diagram of the display apparatus of Example 4 of this invention. It is a figure explaining the concept of the local light control of the backlight in the display apparatus of Example 5 of this invention. It is an example of the timing chart which shows operation | movement of the display apparatus of Example 5 of this invention. It is a block diagram of the display apparatus of Example 5 of this invention. It is an example of the timing chart which shows the backlight drive method in the display apparatus of Example 5 of this invention. It is an example different from FIG. 17 of the timing chart which shows the backlight drive method in the display apparatus of Example 5 of this invention. FIG. 17 is another example of the timing chart showing the backlight driving method in the display device according to the fifth embodiment of the present invention. It is a figure explaining the gradation reproduction local light control system in the display apparatus of Example 5 of this invention. It is a figure explaining the power consumption priority local light control system in the display apparatus of Example 5 of this invention.

Explanation of symbols

  8001, 9001, 11001, 12001, 16001 ... Sync signal, 8002, 9002, 11002, 12002, 16002 ... Video data, 8003, 9003, 11003, 12003, 16003 ... External setting luminance signal, 8010, 9010 11010, 12010, 16010 ... display panel, 8020, 9020, 11020, 12020, 16020 ... panel control unit, 8021, 9021, 11021, 12021, 16021 ... panel control signal, 8022, 9022, 11022, 12022, 16022 ... Write line information, 8030, 9030, 11030, 12030, 16030 ... Video feature extraction unit, 16130 ... Whole video feature extraction unit, 16140 ... Video feature extraction by region , 8031, 9031, 11031, 12031 ... feature, 16131 ... whole video feature, 16141 ... regional video feature, 8040,9040,11040,12040 ... video-linked luminance adjustment unit, 16140 ... Whole video interlocking luminance adjustment unit, 16140 ... Regional video interlocking luminance adjustment unit, 8041, 9041, 11041, 12041 ... Lighting rate for video interlocking luminance adjustment, 16141 ... Whole video interlocking luminance adjustment Lighting rate for use, 16151... Lighting rate for adjusting image-linked luminance for each region, 8050, 9050, 11050, 12050, 16050 ... Intermittent lighting brightness adjustment unit, 8051, 9051, 11051, 12051, 16051 ... Lighting rate for intermittent lighting brightness adjustment, 8060, 9060, 11060, 12060, 121 0, 16060... Lighting rate calculation unit, 8061, 9061, 11061, 12061, 16061... Combined lighting rate, 8070, 9070, 11070, 12070, 16070 .. phase calculation unit, 8071, 9071, 11071, 12071, 16071 ... Optimum phase, 16160 ... Area-specific light amount calculation unit, 16160 ... Area-specific light amount per unit time, 8080, 9080, 11080, 12080, 16080 ... Backlight control signal generation unit, 8081, 9081, 11081, 12081, 16081 ... Backlight control signal, 8090, 9090, 11090, 12090, 16090 ... Backlight, 9100, 11100, 12100, 16100 ... Internally set brightness adjustment unit, 9101, 11101, 121 1, 16101 ... Internally set brightness adjustment information, 11110, 12110, 16110 ... Data converter, 11111, 12111, 16111 ... Synchronized signal after data conversion, 11112, 12112, 16112 ... After data conversion 12000 ... display device, 12200 ... signal processing device, 13010 ... maximum gradation measurement unit, 13011 ... maximum gradation value, 13020 ... average gradation calculation unit, 13021. ..Average gradation value, 13030... Minimum gradation measurement unit, 13031... Minimum gradation value, 13040... Frequency distribution generation unit, 13041... Frequency distribution (histogram), 13050. Measurement unit, 13051... Tone information, 13070.

Claims (18)

A display device comprising a display panel in which a plurality of pixels are arranged, and a backlight that illuminates the display panel, and accepts video data as input and displays it on the display panel,
A backlight lighting drive circuit that performs lighting and extinguishing of the backlight at least once within one frame time of the video data,
The lighting time of the backlight is variable, the backlight is turned on after a predetermined waiting time has elapsed since the display data of the area illuminated by the backlight of the display panel is updated, and the lighting time is further increased. A circuit for turning off the backlight after elapses;
A display device comprising: a circuit that adjusts the predetermined waiting time according to the length of lighting time of the backlight. In claim 1,
A display device, comprising: a circuit that extracts a feature of the video data; and a circuit that adjusts the length of a lighting time of the backlight according to the feature of the video data. In claim 2,
A data conversion circuit for converting the video data; and a circuit for converting the video data according to the characteristics of the video data extracted by the circuit for extracting the characteristics of the video data and displaying the video data on the display panel. A display device. In any one of Claims 1 thru | or 3,
The display device receives, as an input, an externally set luminance signal for adjusting the brightness of the backlight from an external device, and a circuit that adjusts the length of lighting time of the backlight according to the externally set luminance signal A display device comprising:   5. The display device according to claim 4, further comprising a data conversion circuit that converts the video data, and a circuit that converts the video data according to the externally set luminance signal and displays the video data on the display panel. In any one of Claims 1 thru | or 5,
A display device comprising: a circuit for turning on and off the backlight more than once within a lighting time of the backlight; and a circuit for adjusting the luminance of the backlight by turning on and off the backlight. . In any one of Claims 1 thru | or 6.
A circuit that adjusts the brightness of the backlight based on the brightness information of the video data, and the lighting time of the backlight in the lighting drive circuit of the backlight is shortened as the brightness of the backlight decreases. A display device comprising a circuit. A display device comprising a display panel in which a plurality of pixels are arranged, and a backlight that illuminates the display panel, and accepts video data as input and displays it on the display panel,
A backlight lighting drive circuit for turning on and off the backlight at least once within one frame time of the video data;
A circuit that turns on the backlight after a predetermined standby time has elapsed since the display data of the area illuminated by the backlight of the display panel has been updated, and further turns off the backlight after the lighting time has elapsed; ,
The lighting time of the backlight is variable, and includes the circuit for adjusting the predetermined waiting time according to the length of the lighting time of the backlight,
Accepts luminance information adjusted as a feature of the video data, an externally set luminance signal set by an external device, or a combination of both as input, and adjusts the length of lighting time of the backlight according to the luminance information A display device comprising a circuit that performs the above-described operation. In claim 8,
A display device comprising: a circuit for controlling the backlight lighting time in the lighting driving circuit of the backlight to be shorter as the luminance of the backlight is lower according to the luminance information. A display device comprising a display panel in which a plurality of pixels are arranged, a backlight that illuminates the display panel, and a drive circuit that receives video data as input and displays the data on the display panel,
The backlight has a circuit configuration in which a period from when the video data is written to the pixel to when the backlight starts to light is changed according to the length of lighting time of the backlight within one frame period. A display device comprising: A display device comprising a display panel in which a plurality of pixels are arranged, and a backlight that illuminates the display panel, and accepts video data as input and displays it on the display panel,
The backlight is composed of a plurality of backlight regions,
These backlight areas are associated so as to illuminate a plurality of pixels of the display panel, and each of the backlight areas can be turned on and off at least once within one frame time of the video data, and The lighting time of each of the backlight areas can be varied, the backlight area is turned on after a predetermined waiting time has elapsed since the display data of the plurality of pixels illuminated by the backlight area is updated, and After the lighting time has elapsed, the backlight area is turned off, the predetermined standby time is adjusted according to the length of the lighting time of the backlight area, and the light emission amount per unit time in the lighting time can be varied. With a lighting drive circuit,
The lighting drive circuit includes a circuit that extracts the characteristics of the entire one frame of the video data, and a circuit that extracts the characteristics of a plurality of pixels illuminated by the backlight area of the video data for each backlight area, The length of lighting time of the backlight is adjusted according to the characteristics of the entire frame of the video data, and the amount of light emission per unit time in the lighting time is illuminated by the backlight for each backlight area. A display device that adjusts according to characteristics of a plurality of pixels and characteristics of an entire frame of the video data. In claim 11,
The display device according to claim 1, wherein the characteristic of the entire one frame of the video data is a maximum value of gradation values of the video data included in the one frame.   13. The characteristic of the plurality of pixels illuminated by the backlight for each backlight region according to claim 11 is a maximum value of gradation values of video data corresponding to the plurality of pixels. Display device. In claim 11,
The display device according to claim 1, wherein a characteristic of the entire one frame of the video data is a frequency distribution of gradation values of the video data included in the one frame. In any one of Claims 11 thru | or 14.
The display device characterized in that the plurality of pixels illuminated by the backlight for each backlight region is a frequency distribution of gradation values of video data corresponding to the plurality of pixels. In claim 1,
When there is an unused gradation in the gradation frequency distribution of the video data in a certain area, data conversion is performed so that the gradation frequency distribution of the video data extends to the unused gradation, and the background corresponding to the area is converted. A display device comprising a circuit for adjusting the brightness of a light. In claim 1,
If there is no unused gradation in the video data gradation frequency distribution in a certain area, data conversion is performed so that the gradation distribution of the video data exceeds the usable gradation, and the luminance of the backlight corresponding to the area is adjusted. A display device comprising a circuit for adjustment. In claim 1,
When there is an unused gradation in the gradation frequency distribution of the video data in a certain area, data conversion is performed so that the gradation frequency distribution of the video data extends to the unused gradation, and the background corresponding to the area is converted. When there is no unused gradation in the video data gradation frequency distribution in a certain area and the circuit for adjusting the brightness of the light, the data conversion is performed so that the gradation distribution of the video data exceeds the usable gradation, A display device comprising a circuit for adjusting the luminance of a backlight corresponding to a region.

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