JP2013015585A - Display device and display method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display device capable of displaying a video image by an appropriate driving method corresponding to the video image, and further to provide a display method.SOLUTION: A display device related to one embodiment comprises: an input section to which video image data are input for each frame; a display panel for displaying a video image in response to a video image signal written; and a display controller that performs first processing for alternately writing a video image signal based on video image data of a first frame and a video image signal at a predetermined level into the display panel for each predetermined time period in a case where the video image data of the first frame including pixels at a first gradation level is input to the input section and performs second processing different from the first processing for writing a video image signal based on video image data of a second frame into the display panel in a case where the video image data of the second frame including pixels at a second gradation level higher than the first gradation level is input to the input section.

Description

  Embodiments described herein relate generally to a display device and a display method.

  A liquid crystal display device which is a hold-type display device rewrites a display element of a liquid crystal panel based on an input video signal, and displays a video by irradiating the liquid crystal panel with a backlight. In such a liquid crystal display device, an afterimage may occur when the liquid crystal is held. Therefore, a technique for suppressing the afterimage using a liquid crystal driving method that inserts a black frame for each frame has been proposed. .

JP-A-2005-196108

Here, when displaying an image on the display device, it is preferable that the image can be displayed by a suitable driving method corresponding to the image.
Therefore, an object of the embodiment of the present invention is to provide a display device and a display method capable of displaying an image by a suitable driving method corresponding to the image.

  In order to solve the above-described problems, a display device according to the present embodiment includes an input unit to which video data is input for each frame, a display panel that displays video according to a written video signal, and the input unit. When a first frame of video data including pixels of the first gradation level is input to the display panel, a video signal based on the video data of the first frame and a video signal of a certain level are fixed on the display panel. When a first process of alternately writing for each period is performed, and a second frame including a pixel of a second gradation level higher than the first gradation level is input to the input unit, the display panel receives the second frame A display control unit that writes a video signal based on the video data of two frames and performs a second process different from the first process.

The figure which shows the system configuration example of the display apparatus which concerns on embodiment. The figure which shows the example of a drive system at the time of the display apparatus which concerns on embodiment displays an image | video. FIG. 5 is a diagram illustrating an example of a relationship between a gradation level of a video signal input to the display device according to the embodiment and luminance of a video to be displayed. The figure which shows the example of a switching of the drive system by the display apparatus which concerns on embodiment. The figure which shows the example of a processing flow which concerns on the video display by the display apparatus which concerns on embodiment.

Hereinafter, embodiments will be described with reference to the drawings.
FIG. 1 is a diagram illustrating a system configuration example of a display device according to the present embodiment. In the present embodiment, the display device is realized as, for example, the television device 100, and the television device 100 has a function of displaying an image by switching, for example, the first and second driving methods, as will be described later with reference to FIG. Have The television apparatus 100 includes a tuner 101, a media reader 102, an HDD 103, an operation reception unit 104, a video input unit 105, a decoder 106, a gradation detection unit 107, a drive control unit 108, a gamma adjustment unit 109, a display unit 110, and a backlight control. Unit 111, backlight 112, and the like.

  The tuner 101 is, for example, a satellite digital television broadcast signal received by a BS / CS (Broadcasting Satellite / Communication Satellite) digital broadcast reception antenna (not shown) or a ground wave broadcast reception antenna (not shown). Receiving a digital television broadcast signal. The tuner 101 demodulates digital video data included in the received broadcast signal and outputs the video data to the video input unit 105.

  For example, a portable storage medium such as an optical disk or a USB memory is connected to the media reader 102. Then, the media reader 102 reads the video data stored in the storage medium and outputs the read video data to the video input unit 105.

  The HDD 103 is a storage medium that stores video data. For example, the HDD 103 stores video data received by the tuner 101. Then, the HDD 103 outputs the stored video data to the video input unit 105.

  The operation reception unit 104 receives an operation input from a user. For example, the operation reception unit 104 inputs an operation input for instructing switching (selection) of the driving method of the television apparatus 100, and causes the video input unit 105 to input video from any of the tuner 101, the media reader 102, and the HDD 103. The operation input etc. which instruct | indicate is received. Then, when a drive method switching operation is input, the operation reception unit 104 outputs a signal of the operation input to the drive control unit 108. Here, examples of the drive system switching operation include an operation for designating one of the first and second drive systems described above, or an operation for designating a display mode such as a movie mode, a sport mode, a bruise mode, or the like. It is done. Note that the operation receiving unit 104 may be configured to receive an operation signal from a remote controller (not shown), or may be configured as an operation panel provided in the television apparatus 100, for example.

  Video data is input to the video input unit 105 from any of the tuner 101, media reader 102, and HDD 103. The video data input to the video input unit 105 is input to the decoder 106, and the decoder 106 decodes the input video data. The decoder 106 outputs the decoded video data to the gradation detection unit 107 and the gamma adjustment unit 109.

  The gradation detector 107 detects the gradation level (gray level, brightness level, luminance level) of the video data input from the decoder 106. Here, the gradation detection unit 107 detects the gradation level of each pixel in the frame for each frame from the input video data. Then, the gradation detection unit 107 notifies the drive control unit 108 that a predetermined number or more of pixels having gradation levels equal to or higher than a predetermined threshold are included in one frame, and displays an image using the first drive method. . Further, when a predetermined number or more of pixels having a gradation level equal to or higher than a predetermined threshold is not included in one frame, the gradation detection unit 107 notifies the drive control unit 108 to display an image using the second drive method. Note that the gradation detection unit 107 does not necessarily detect the gradation level from the decoded video data. For example, when the encoded video data includes luminance information or the like, the gradation level of the video is determined from the luminance information or the like. May be detected.

  The drive control unit 108 performs control to switch the driving method of the television device 100. Here, the drive control unit 108 selects one of the first drive method and the second drive method according to the notification from the gradation detection unit 107 and the operation signal from the operation reception unit 104. Then, the drive control unit 108 instructs the gamma adjustment unit 109 and the backlight control unit 111 to drive with the selected drive method. When an operation signal designating either the first or second drive method is input, the drive control unit 108 selects either the first or second drive method according to the operation signal. On the other hand, when an operation signal designating a display mode such as a movie mode, a sports mode, or a vivid mode is input, a driving method associated with the display mode in advance is selected in the television device 100. In the television apparatus 100, for example, the first drive method is associated with the movie mode and the sport mode, and the second drive method is associated with the vivid mode.

  The gamma adjustment unit 109 adjusts the gradation level for each pixel of the video data input from the decoder 106 to a gradation level corresponding to the drive method instructed from the drive control unit 108. The adjustment of the gradation level will be described later with reference to FIG. Then, the gamma adjustment unit 109 converts the video data with the adjusted gradation level into a video signal in a format that can be displayed by the display unit 110, and outputs the video signal obtained by the conversion to the display unit 110 for display. The video signal is written on the liquid crystal panel of the unit 110. For example, when the video signal corresponding to the first driving method is output to the display unit 110, the gamma adjustment unit 109 outputs a synchronization signal regarding the timing of outputting the black level video signal to the display unit 110. To 111.

The display unit 110 is a display device such as a liquid crystal panel, and displays an image by writing an input video signal in a liquid crystal element.
The backlight control unit 111 drives the backlight 112 by a method according to an instruction from the drive control unit 108. In other words, the backlight control unit 111 drives the backlight 112 by, for example, either a control that always turns on the illumination of the backlight 112 or a control that switches ON / OFF of the illumination every predetermined time. The backlight control unit 111 outputs the ON / OFF switching instruction at a timing corresponding to the synchronization signal from the gamma adjustment unit 109.

The backlight 112 is a module that illuminates the display unit 110 and is driven by a method according to an instruction from the drive control unit 108.
The television apparatus 100 may have a function of displaying not only 2D images but also 3D images of, for example, a frame sequential method (shutter glasses method), but the following description will focus on the case of displaying 2D images. To do.

FIG. 2 is a diagram illustrating an example of a driving method when the television apparatus 100 displays an image.
FIG. 2A is a diagram illustrating an operation example of the first driving method by the television device 100. In the first drive method, the gamma adjustment unit 109 outputs a black level video signal to the display unit 110 every predetermined period, and the backlight 112 corresponds to the timing at which the black level video signal is displayed on the display unit 110. Turn off the light. Then, the backlight 112 turns on the illumination in accordance with the timing at which the video signal of the video data is displayed on the display unit 110. Note that the black level means, for example, that the gradation level is 0, but the gamma adjustment unit 109 does not necessarily output the black level video signal, and the gradation level is a constant level close to 0. A video signal may be output.

  That is, for example, when 60 fps video data is input, the gamma adjustment unit 109 inputs the first half (or second half) of 1/120 s out of the 1/60 s period corresponding to one frame of the video data. A video signal having a gray level corresponding to the gray level of the video data is output to the display unit 110, and a black level video signal is output to the display unit 110 in 1 / 120s of the second half (or first half). Here, the backlight 112 illuminates the display unit 110 during a 1 / 120s period of the first half (or second half) of the 1/60 second period corresponding to one frame of video data, and the second half (or first half) 1 The illumination for the display unit 110 is limited to / 120s.

  More specifically, for example, when T1-T2, T2-T3, T3-T4, and T4-T5 correspond to 1/120 s and a frame of video data is input to the gamma correction unit 109 at 60 fps, the gamma The adjustment unit 109 outputs the video signal of the input frame during the period of T1-T2 corresponding to the period of 1 / 120s, and outputs the video signal of the black level during the next period of 1 / 120s (T2-T3). To do. Then, the gamma adjustment unit 109 outputs the video signal of the next input frame during the next 1 / 120s period (T3-T4), and the next 1 / 120s period (T4-T5). During the period, the black level video signal is output again.

The backlight 112 illuminates the display unit 110 during the periods T1-T2 and T3-T4, and restricts illumination to the display unit 110 during the periods T2-T3 and T4-T5.
FIG. 2B is a diagram illustrating an operation example of the second driving method by the television device 100. In the second drive method, the gamma adjustment unit 109 outputs a video signal having a gradation level based on the input video data to the display unit 110, and the backlight 112 continues to illuminate the display unit 110.

  That is, for example, when T1-T2, T2-T3, T3-T4, and T4-T5 correspond to 1/120 s and a frame of video data is input to the gamma correction unit 109 at 60 fps, the gamma adjustment unit 109 The video signal of the input frame is output during the 1/60 s period (T1-T3), and the video signal of the next input frame is output during the next 1/60 s period (T3-T5). And the backlight 112 illuminates the display part 110 during the period of T1-T5.

  Note that in the first drive method of FIG. 2A, the second half T2-T3 of the T1-T3 period corresponding to the display period of one frame is output as a black level (constant level) video signal. Although described as a period, the output period of the video signal of the black level may be longer or shorter. In the second driving method in FIG. 2B, the case where the backlight 112 continues to illuminate without outputting the black level signal has been described. However, the second driving method also has a period corresponding to the display period of one frame. A black level signal may be output during a partial period, and illumination of the backlight 112 may be limited in accordance with the output of the black level signal. However, in this case as well, the black level signal output period of the first drive method is longer than the black level output period of the second drive method.

  That is, the gamma adjustment unit 109 outputs (writes) the video signal based on the video data to the display unit 110 during a part of the period corresponding to the display period of one frame in the first drive method, and performs the second drive. In the method, a video signal based on the video data is output (written) to the display unit 110 in a period longer than a part of the first driving method in a period corresponding to a display period of one frame.

  In the first driving method of FIG. 2A, the backlight 112 is described as being turned off in synchronization with the black level signal output period. However, in the first driving method, for example, the black level signal is constant. The backlight 112 may be continuously turned on by outputting every period, or the backlight 112 may be turned on / off every certain period without outputting the black level signal every certain period. In other words, in the first driving method, writing with a signal of a certain level (black level) to the display unit 110 and / or limitation of illumination of the backlight 112 is performed every certain period. Note that the writing and illumination are limited, for example, during a part of the display period of one frame.

  In the second drive method, writing with a signal of a certain level (black level) to the display unit 110 and / or limitation of illumination of the backlight 112 may be performed every certain period. For example, the writing or illumination is limited in a part of the display period of one frame, but the partial period is shorter than the partial period in which writing or illumination is limited in the first driving method.

Next, the signal level of the video signal output from the gamma adjustment unit 109 to the display unit 110 and the luminance value of the display unit 110 observed from the outside will be described with reference to FIG.
FIG. 3A is a diagram illustrating an example of signal processing when an image is displayed by a driving method corresponding to the first driving method. The “gradation level of the original video data” is the gradation level in the video data input to the gamma adjustment unit 109, and the “signal level of the video signal output to the display unit” is the gamma adjustment unit 109 of the display unit 110. The signal level written to the display unit 110 and “the luminance value of the display unit observed from the outside” is the time of the luminance value monitored (measured) from the outside with respect to the video displayed on the display unit 110 The average is shown.

  Here, when video data having a gradation level of 0 to 1000 is input to the gamma adjustment unit 109, the gamma adjustment unit 109 outputs, for example, a video signal having a level along a curve corresponding to C1 to the display unit 110. Here, the curve of C1 is, for example, a 1/3 function, which is a curve used when the display unit 110 displays an image having a luminance proportional to the level of the input image signal. An actual display panel may have a characteristic in which the input signal level and the display luminance are not proportional to each other. In that case, a video signal having a level that matches the characteristic of the display panel is output to the display panel (display unit). .

  The display unit 110 displays the video of the input video signal. The luminance of the video displayed here is, for example, along the curve of C2. That is, when video data having a gradation level of 1000 is input to the gamma adjustment unit 109 and the video of the video data is displayed on the display unit 110, a video with a luminance value of 40% is observed from the outside. Note that 40% is a value when an image luminance value observed when displaying an image of 1000-level image data by the second driving method described later is 100%. Then, when video data having a gradation level of 0 is input to the gamma adjustment unit 109 and the video of the video data is displayed on the display unit 110, a video with a luminance value of 2% is observed from the outside.

  FIG. 3B is a diagram illustrating an example of signal processing when an image is displayed by a driving method corresponding to the second driving method. Here, when video data having a gradation level of 0 to 1000 is input to the gamma adjustment unit 109, the gamma adjustment unit 109 outputs a video signal having a level along a curve corresponding to C1, for example, as in the first driving method. Output to the display unit 110. The display unit 110 displays the video of the input video signal. The luminance of the video displayed here is, for example, along the curve of C3. That is, when video data with a gradation level of 1000 is input to the gamma adjustment unit 109 and the video of the video data is displayed on the display unit 110, a video having a luminance value of 100% is observed from the outside. On the other hand, when video data having a gradation level of 0 is input to the gamma adjustment unit 109 and the video of the video data is displayed on the display unit 110, a video having a luminance value of 10% is observed from the outside.

  Here, when C2 in FIG. 3A is compared with C3 in FIG. 3B, a low-luminance video can be displayed in the first driving method, and a high-luminance video can be displayed in the second driving method. You can see that you can. Therefore, as shown in FIGS. 3C and 3D, the television device 100 according to the present embodiment switches the first driving method and the second driving method according to the gradation level of the video data, thereby reducing the Brightness and high-luminance video can be suitably displayed. Note that FIG. 3C is a diagram illustrating an example of signal processing in the case where an image is displayed by the first driving method when the driving method is switched and used. FIG. 3D is a diagram illustrating an example of signal processing in a case where an image is displayed by the second driving method when the driving method is switched and used.

  In the first driving method, it is assumed that only an image up to a luminance value of 40% can be displayed as shown in FIG. For a frame including video data that is desired to be displayed with a luminance value of 40% or more with respect to the outside, video signals from 0 level to 1000 level are displayed along the curve C1 using the second driving method. By outputting to the unit 110, the luminance of the video is along the curve C31, and a video having a luminance value of 10-100% can be displayed to the outside.

  On the other hand, for video data of a frame that is desired to be displayed with a luminance value of 40% or less with respect to the outside, a video signal of 0-1000 level is output to the display unit 110 along the curve C1 using the first driving method. By doing so, the luminance of the video is along the curve C21, and a low-luminance video with a luminance value of 2-40% can be displayed. Here, the curve C1 is a curve based on the curve C1, and the level 1000 of the video signal output to the display unit is associated with the gradation level V1 of the original video data. That is, when the video data of the gradation level V1 is input, the gamma adjustment unit 109 outputs a video signal of level 1000 to the display unit 110, and an image with a luminance value of 40% is observed from the outside.

  Furthermore, in the first driving method, since gradation values of 0-1000 level are assigned to video data that is desired to be displayed with a luminance value of 0-40%, display with a luminance value of 0-40% is desired. Compared with the second driving method in which the 0-V1 level gradation value is assigned to the video data, a gradation level of about (1000 / V1) times can be assigned, and the luminance value of the dark portion can be displayed more finely.

  FIG. 3 illustrates the case where the switching between the first driving method and the second driving method is based on 40% of the maximum luminance that can be displayed by the first driving method. A luminance value smaller than the maximum luminance value that can be displayed by one driving method may be used. That is, for example, when the gradation value that is desired to be displayed with a luminance value of 30% is used as a switching reference, the second drive method is used for an image that is desired to be displayed with a luminance value of 30% or more. Use. The first drive method is used for an image that is desired to be displayed with a luminance value of 30% or less.

  Next, with reference to FIG. 4, an example of processing related to determination of drive method switching by the television device 100 will be described. FIG. 4 is a diagram showing the gradation level of each pixel in one frame of the video data input to the gamma adjustment unit 109.

  4A shows the case where the gradation level of the area A1 is 800 and the gradation level of the area A2 is 1000, and FIG. 4B shows the gradation level of the area A3 is 500 and the gradation level of the area A4 is 1000. 4C shows a case where the gradation level of the area A5 is 200 and the gradation level of the area A6 is 1000, and FIG. 4D shows a case where the gradation level of the area A7 is 200 and the gradation level of the area A8. The case where the key level is 600 is shown.

  For example, the gradation detection unit 107 determines whether or not there is a pixel having a gradation level equal to or higher than a predetermined threshold in one frame, and the drive control unit 108 selects a drive method based on the determination result. Here, for example, when the gradation value 700 is set as a threshold value, the frame shown in FIGS. 4A, 4 </ b> B, and 4 </ b> C includes pixels having a gradation value of 700 or more. These frames are determined to be displayed by the second driving method, and the gamma adjustment unit 109 and the backlight control unit 111 are instructed. The gamma adjustment unit 109 outputs the video signal having the level indicated by the curve C1 in FIG. 3D to the display unit 110, and the display unit 110 writes the input video signal to the liquid crystal element corresponding to each pixel. indicate. The backlight control unit 111 drives the backlight 112 by the second driving method described in FIG. Note that the gamma adjustment unit 109 may output a video signal having a level indicated by a curve C1 in FIG. 3D and a black level signal during a display period of one frame.

  Since the frame shown in FIG. 4D does not include pixels with a gradation value of 700 or more, the drive control unit 108 determines to display these frames in the first drive method, and the gamma adjustment unit 109 and Instructs the backlight control unit 111. The gamma adjustment unit 109 outputs a video signal at a level along the curve C1 shown in FIG. 3C to the display unit 110 by the first driving method shown in FIG. 2, and the display unit 110 receives the input video signal. Is written in a liquid crystal element corresponding to each pixel to display an image. The backlight control unit 111 drives the backlight 112 by the first driving method described in FIG.

  Note that when the gradation detection unit 107 detects the gradation level of each pixel in the frame, the gradation detection unit 107 detects whether a pixel having a gradation level equal to or higher than a predetermined threshold exists over a range equal to or larger than a predetermined size. Also good. Even when there is a pixel having a gradation level equal to or higher than the predetermined threshold in the frame, if the area of the gradation level equal to or higher than the predetermined threshold is narrower than the predetermined range, the drive control unit 108 A driving method may be selected.

  Further, the gamma adjustment unit 109 may correct the level of the video signal output to the television device 100 based on the gradation level of the previous frame when switching the driving method. The reason for this will be described assuming that the video of the frame of FIG. 4D is displayed next to the frame of FIG. The area A5 and the area A7 are displayed in the same area when displayed on the display unit 110. Here, when the frame of FIG. 4C is displayed by the second driving method, an image of the region A5 having a luminance value of about 10% is observed from the outside in view of FIG. On the other hand, when the frame of FIG. 4D is displayed by the first drive method, considering from FIG. 3, the image of the region A7 having a luminance value of about 2% is observed from the outside. In other words, when the drive method is switched for each frame and displayed, even when the input video data has the same gradation level, the luminance value of the video observed from the outside may be different.

  For this reason, the gamma adjustment unit 109 may perform correction so as to increase the luminance value of the image displayed outside when the second driving method is switched to the first driving method. Similarly, the gamma adjustment unit 109 may perform correction so that the luminance value of an image displayed outside becomes low when the first drive method is switched to the second drive method.

Next, with reference to FIG. 5, an example of a processing flow relating to video display by the television device 100 will be described.
First, one frame of decoded video data is input to the gradation detection unit 107 and the gamma adjustment unit 109 (S501). The gradation detector 107 detects the gradation level of each pixel in the input data (S502). Here, when the gradation detection unit 107 does not detect a pixel having a gradation level equal to or higher than a predetermined threshold from one frame (No in S503), the drive control unit 108 selects the first drive method as the drive method and displays it. The unit 110 displays an image using the first driving method (S507).

  On the other hand, when the gradation detection unit 107 detects pixels having a gradation level equal to or higher than a predetermined threshold from one frame (Yes in S503), and the range (size) of pixels equal to or higher than the threshold is equal to or higher than the predetermined range. (Yes in S505), the drive control unit 108 selects the second drive method as the drive method, and the display unit 110 displays an image using the second drive method (S506).

  Further, even when the range (size) of the pixels equal to or greater than the threshold is not equal to or greater than the predetermined range in S505 (No in S505), the number of pixels equal to or greater than the threshold is equal to or greater than the predetermined number (Yes in S507). The drive control unit 108 selects the second drive method as the drive method, and the television set 100 executes the process of S506.

  Then, when the television apparatus 100 executes the process of S504 or S506 and displays an image by the first or second driving method, the television apparatus 100 executes the process of S501 again, and the gradation detection unit 107 and the gamma adjustment unit. An image is input to 109. Then, the television device 100 repeats the above processing, and when the video data is no longer input, the processing flow is completed.

  In the example of the processing flow in FIG. 5, the driving method is switched according to the detection result of the gradation detection unit 107, but the television apparatus 100 changes the driving method according to the operation input to the operation reception unit 104 as described above. You may switch. In addition, for example, when the decoded video data header includes data related to the video gradation level, the gradation detection unit 107 may extract the data and detect the video gradation level. . Alternatively, data related to the driving method may be included in the data header of the video data. In this case, the gradation detecting unit 107 extracts the data and outputs the data to the driving detecting unit 108, and the driving detecting unit 108 outputs the data. The driving method may be selected based on the above.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 100 ... Television apparatus, 101 ... Tuner, 102 ... Media reader, 103 ... HDD, 104 ... Operation reception part, 105 ... Video input part, 106 ... Decoder, 107 ... Tone detection part, 108 ... Drive control part, 109 ... Gamma Adjustment unit, 110 ... Display unit, 111 ... Backlight control unit, 112 ... Backlight

Claims (9)

An input unit for inputting video data for each frame;
A display panel for displaying video according to the written video signal;
When video data of a first frame including pixels of a first gradation level is input to the input unit, a video signal based on the video data of the first frame and a video signal of a certain level are input to the display panel. When the second frame including pixels of the second gradation level higher than the first gradation level is input to the input unit, the display panel is A display control unit that writes a video signal based on the video data of the second frame to the display control unit and performs a second process different from the first process.   The display control unit performs the first process when video data of the first frame whose maximum gradation level of a pixel in a frame is equal to or less than a predetermined threshold is input to the input unit, and the input unit The display device according to claim 1, wherein the second process is performed when video data of the second frame in which a maximum gradation level of a pixel in the frame is higher than a predetermined threshold is input.   In the first process, the display control unit writes a video signal based on the video data in the display panel in a part of a period corresponding to the display period of the first frame, and performs the second process. 2. The display device according to claim 1, wherein a video signal based on the video data is written to the display panel in a period longer than the partial period in a period corresponding to the display period of the second frame.   3. The display according to claim 2, wherein the display control unit performs the second process when a pixel whose gradation level is higher than the predetermined threshold is in a range wider than a predetermined range in the second frame. apparatus.   The display device according to claim 2, wherein the display control unit performs the second process when the number of pixels having a gradation level higher than the predetermined threshold is greater than a predetermined number in the second frame.   As for the brightness of the display panel observed from the outside in the first process, the display control unit writes a video signal based on the video data of the predetermined threshold gradation level in the display panel in the first process. The display device according to claim 2, wherein the display device is maximized in such a case. It further comprises operation accepting means for receiving operation input from the user,
The display device according to claim 1, wherein the display control unit switches between the first process and the second process in accordance with the operation input.   When the display control unit switches from one of the first processing and the second processing to the other, the display control unit performs the switching after the switching according to the gradation level of the frame written on the display panel before the switching. The display device according to claim 1, wherein the level of the video signal written to the display panel is corrected. A display method for displaying an image on a display panel,
Video data is input for each frame,
When video data of a first frame including pixels of a first gradation level is input, a video signal based on the video data of the first frame and a video signal at a certain level are input to the display panel for a certain period. Performing a first process of alternately writing each time;
When a second frame including pixels having a second gradation level higher than the first gradation level is input, a video signal based on the video data of the second frame is written to the display panel. Performing a second process different from the process;
A display method comprising:

Images