JP2016048298A - Light emission control device, light emission control method and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display device capable of reducing influences of flicker and moving image blur irrespective of the size of a display area.SOLUTION: A display device 100 includes: a backlight part 109 that illuminates a display part 105 with a beam of light; and a backlight control section 107 that controls lighting timing as a timing of lighting the backlight part 109 to illuminate the display part 105 based on the display size of an image displayed on the display part 105. The backlight control section 107 controls the backlight part 109 to repeat turning ON/OFF to illuminate the display part 105 at a turning ON/OFF frequency based on the display size.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a light emission control device, a light emission control method, and a display device that control lighting timing of light applied to a display device.

  In recent years, a liquid crystal display device having a backlight using an LED (light-emitting diode) as a light source has become widespread. In a direct type backlight that irradiates from the back of the liquid crystal panel, multiple LEDs are arranged in an array, and lighting control of each area is independently performed, so that high image quality and power consumption can be reduced. is there.

  As a method for adjusting the luminance of the backlight, PWM (pulse-width modulation) control is known. In the PWM control, desired brightness can be obtained by adjusting the light emission period (duty ratio) with respect to the light emission cycle of each LED to blink the LED.

  Patent Document 1 discloses a technique in which a backlight corresponding to a region for displaying a video is blinked while a backlight corresponding to a region for displaying a still image is always lit. Patent Document 2 discloses a technique for blinking a backlight at a timing corresponding to the moving speed of an image.

JP 2005-99367 A JP 2006-323300 A

  Since PWM control is performed so that the lighting period and the extinguishing period are repeated, depending on the blinking frequency, a user viewing an image on the display device may feel flickering due to blinking of the backlight (hereinafter referred to as “flicker”). . In order to make it difficult for the user to recognize flicker, it is common to blink the backlight at a frequency higher than the scanning frequency of the liquid crystal display. On the other hand, since the liquid crystal display is less responsive than self-luminous devices such as cathode ray tube displays and plasma displays, if the blinking frequency of the backlight is too high, “moving image blur” occurs due to the effect of afterimages.

  With respect to such a problem, according to Patent Documents 1 and 2, it is difficult to recognize flicker by determining the flashing frequency of the backlight when displaying an image in consideration of the response speed of the liquid crystal. In addition, it is said that blurring of moving images can be reduced.

  However, in the conventional technology, it is considered that the ease of flicker is affected by the size of the display area, and that the larger the display area, the easier it is for a user viewing an image on the display device to recognize the flicker. Not. Therefore, according to the conventional technique, the backlight is repeatedly turned on / off at a predetermined blinking frequency regardless of the size of the display area. Therefore, there is a problem that flicker is easily recognized when the display area is large.

  Therefore, the present invention has been made in view of the above points, and an object thereof is to reduce the influence of flicker and moving image blur regardless of the size of the display area.

  In order to solve the above-described problems, the light emission control device of the present invention includes a light emitting unit that irradiates light to the display unit, and a display unit that displays the image displayed on the display unit. Control means for controlling a lighting timing that is a timing for lighting the light to be irradiated.

  According to the present invention, it is possible to reduce the influence of flicker and moving image blur regardless of the size of the display area.

It is a figure which shows the external appearance of the display apparatus 100 which concerns on 1st Embodiment. It is explanatory drawing of the lighting timing of a backlight. 2 is a diagram showing a configuration of a display device 100. FIG. It is a figure which shows typically the structure of the LED driver 108 and the backlight part 109. FIG. FIG. 3 is a diagram illustrating an example of connection between an LED driver and a backlight unit 109. It is a figure which shows the timing of lighting and extinguishing of the backlight at the normal time. It is a figure which shows an example of the timing of lighting of the backlight in the case of performing a backlight scan, and light extinction. It is a figure which shows the other example of the timing of lighting of the backlight in the case of performing a backlight scan, and extinction. It is a figure for demonstrating operation | movement of the display apparatus 100 which concerns on 1st Embodiment. It is a figure which shows the blink pattern of the backlight part. It is a figure which shows the other example of the blink pattern of the backlight part. It is a figure which shows the relationship between light intensity and a critical fusion frequency. It is a table which shows the relationship between the light emission luminance of the backlight part 109, and blinking frequency. It is a table which shows the relationship between a display size, a backlight brightness | luminance, and a blinking frequency. It is a figure which shows the structure of the display apparatus 200 which concerns on 3rd Embodiment. It is a table which shows the relationship between illumination intensity and blink frequency. It is a table which shows the relationship between viewing distance and blink frequency. It is a figure which shows the state in which the display apparatus 200 was installed sideways, and the state installed in the vertical direction. It is a table which shows the relationship between an installation direction and a blink frequency.

<First Embodiment>
[Overview of this embodiment]
FIG. 1 is a diagram illustrating an appearance of a display device 100 according to the first embodiment. The display device 100 includes a display unit 105. The display unit 105 is a liquid crystal panel that displays an image in an image display region R set by a user, for example. The display device 100 controls the timing of lighting the light emitting means that irradiates the display unit 105 according to the size of the image display region R. Hereinafter, a backlight will be described as an example of the light emitting means.

  FIG. 2 is an explanatory diagram of the lighting timing of the backlight. FIG. 2A shows the response speed characteristics of the liquid crystal. In FIG. 2A, the horizontal axis indicates the elapsed time after switching a black display pixel to white display, and the vertical axis indicates the chromaticity of the pixel. The origin corresponds to the frame start timing at which the vertical synchronization signal is generated. The time T is the reciprocal of the scanning frequency of the display unit 105 and corresponds to a frame period that is a time interval of the vertical synchronization signal. As shown in FIG. 2A, the chromaticity of the liquid crystal pixels stabilizes after gradually changing after the displayed image is switched.

  FIG. 2B is a diagram illustrating a lighting timing pattern of the backlight. An “on” period in FIG. 2B indicates a period during which the backlight is lit. The display device 100 controls the lighting timing of the backlight in different patterns such as pattern 1, pattern 2, and pattern 3 shown in FIG. 2B, for example, by changing the length of the lighting period and the length of the extinguishing period. it can. In this specification, the length of a period including one lighting period and at least one lighting period when the lighting period and the lighting period are repeated is referred to as a blinking period. The reciprocal of the blinking cycle is called the blinking frequency.

  When the scanning frequency is 60 Hz, the blinking frequency in the pattern 1 is 300 Hz. In pattern 1, five blinking cycles are included in one frame period. In this specification, the number of blinking cycles included in one frame period is referred to as the number of blinking cycles. The number of blinking periods of pattern 1 in FIG.

  In the pattern 2, the lighting period becomes longer and the blinking frequency becomes lower with the passage of time from the start timing of the frame. The number of blinking periods in pattern 2 is 3. The blinking frequency in Pattern 3 is 60 Hz, the same as the scanning frequency, and the blinking cycle number is 1.

  The display device 100 relatively shortens the backlight lighting period before a predetermined time elapses from the frame start timing, and lengthens the backlight lighting period as time elapses from the frame start timing. Perform a backlight scan. The display device 100 can reduce the moving image blur caused by the slow response speed of the liquid crystal by performing the backlight scan.

In addition, it is known that human eyes are more likely to recognize flicker as the area of the blinking light source increases. For example, when the backlight brightness is 100 cd / m ² and the blinking frequency is 60 Hz, when the user views an image on a 30-inch display, compared to when the user views an image on a 7-inch display, The user can easily recognize flicker. Therefore, the display device 100 changes the blinking frequency and the number of blinking cycles according to the size of the area for displaying an image (hereinafter referred to as “display size”), as shown in the examples from pattern 1 to pattern 3. Can do.

  For example, when the display size is relatively large, the display device 100 increases the blinking frequency as in pattern 1 or increases the blinking cycle number, thereby making it difficult for the user to recognize flicker. Further, when the display size is relatively small, the display device 100 reduces the blinking frequency and the number of blinking cycles as in pattern 2 or pattern 3. In this way, the display device 100 can make it difficult for the user to recognize flicker regardless of the display size by controlling the lighting timing of the backlight according to the display size.

[Configuration of Display Device 100]
Details of the configuration of the display device 100 will be described below.
FIG. 3 is a diagram illustrating a configuration of the display device 100. The display device 100 includes a CPU 101, an input unit 102, an image processing unit 103, a display size control unit 104, a display unit 105, an operation input unit 106, a backlight control unit 107, an LED driver 108, a backlight, And a light unit 109. The backlight control unit 107, the LED driver 108, and the backlight unit 109 constitute a light emission control device 150.

The CPU 101 is connected to a ROM and a RAM (not shown) via a data bus. The CPU 101 controls the operation of the display device 100 using the RAM as a work memory by executing a program stored in the ROM.
The input unit 102 decodes image data input from an image output device such as a computer. The input unit 102 outputs the decoded image data to the image processing unit 103.

  The image processing unit 103 performs signal processing such as γ correction and color correction on the image data input from the input unit 102. The image processing unit 103 outputs the image data after the signal processing to the display size control unit 104.

  The display size control unit 104 controls the display size of an image displayed on the display unit 105. For example, the display size control unit 104 generates image data to be output to the display unit 105 based on the display size input by the user via the operation input unit 106. The display size control unit 104 may determine an appropriate display size based on an arbitrary condition such as the type of image to be displayed and the ambient brightness, and generate image data corresponding to the determined display size. Good.

  The display unit 105 is a liquid crystal panel, for example. The display unit 105 displays an image based on the image data by aligning the liquid crystal based on the image data input from the display size control unit 104.

  The operation input unit 106 receives an input of a user operation. The operation input unit 106 displays, for example, a menu screen for selecting the display size of the image on the display unit 105, and accepts a selection by the user. For example, the operation input unit 106 displays a plurality of display size candidates of 100%, 50%, and 25% with respect to the size of the display unit 105, and displays information indicating the display size selected from the plurality of display size candidates. And output to the display size control unit 104 and the backlight control unit 107.

  The backlight control unit 107 controls the lighting timing of light emitting diodes (hereinafter referred to as “LEDs”) that constitute the backlight unit 109. Specifically, the backlight control unit 107 controls either the blinking frequency or the blinking cycle number of the LED based on the display size of the image displayed on the display unit 105. Details of the operation of the backlight control unit 107 will be described later.

  The LED driver 108 blinks the LED included in the backlight unit 109 based on the control information input from the backlight control unit 107. The LED driver 108 performs PWM control of the backlight unit 109 based on the blinking frequency and duty ratio set for each driving cycle.

  The backlight unit 109 irradiates the display unit 105 from the back surface or side surface of the display unit 105. The backlight unit 109 has a plurality of LEDs, and switches between the lighting state and the unlighting state of each LED based on the control of the backlight control unit 107.

  FIG. 4 is a diagram schematically showing the configuration of the LED driver 108 and the backlight unit 109. The LED driver 108 includes four LED drivers 108a, 108b, 108c, and 108d, and the backlight unit 109 is divided into four regions a, b, c, and d. The LED drivers 108a, 108b, 108c, and 108d drive the LEDs in the regions a, b, c, and d, respectively. The regions a, b, c, and d are each divided into 16 sub-regions (hereinafter referred to as “LED blocks”). In FIG. 4, the LED blocks are indicated as LB1, LB2,.

  FIG. 5 is a diagram illustrating a connection example between the LED driver 108 and the backlight unit 109. The backlight unit 109 includes an LED string 91 including a plurality of LEDs connected in series to each LED block. Each LED driver 108 has a plurality of terminals 81 for controlling the LED string 91. One LED string 91 is connected to each terminal 81, and the LEDs connected to one LED string 91 are turned on or off simultaneously. The LED driver 108 can set the magnitude of the current to be output and the PWM duty ratio for each of the terminals 81. One LED string 91 corresponds to one LED block shown in FIG. 4, and the backlight unit 109 can be turned on and off at different timings for each LED block.

  A group composed of a plurality of LED blocks arranged in the horizontal direction in FIG. 4 is referred to as a backlight control line 201. In the following description, it is assumed that LED blocks included in the same backlight control line 201 are turned on and off at the same timing.

[Example of backlight on / off timing]
FIG. 6 is a diagram illustrating the timing of turning on and off the backlight in the normal time when the backlight scan is not performed. 6, line 1, line 2,..., Line 8 are arranged in order from the upper backlight control line 201 in the backlight unit 109 shown in FIG.

  The period (frame period) between the vertical synchronizing signals in FIG. 6 is divided into five subframe periods. The backlight unit 109 turns on the LED of the line 1 at a timing when the vertical synchronization signal becomes high level, and turns off the LED after a predetermined lighting period has elapsed. Then, the backlight unit 109 turns the LED of line 1 on again after a time of N / 5 frames (N is an integer of 1 or more and 4 or less) and turns off the light after the lighting period has elapsed. .

  The backlight unit 109 turns on the LED of the line 2 after the predetermined time has elapsed with respect to the timing of turning on the LED of the line 1 and turns off the LED after the predetermined lighting period. In the same manner for other lines, the LED is switched between the on state and the off state. For example, the backlight unit 109 sets the first 50% of each subframe period to a lighting state and the remaining period to a lighting state.

  FIG. 7 is a diagram illustrating an example of the timing of turning on and off the backlight when performing backlight scanning. When performing a backlight scan, the LED is repeatedly turned on / off at a lower frequency than that shown in FIG. The number of blinking periods in the example of FIG.

  As shown in FIG. 7, when performing a backlight scan, the backlight unit 109 turns on the LED of the line 1 after the response delay time Rd of the liquid crystal elapses from the timing when the vertical synchronization signal becomes high level. The light is turned off after a predetermined lighting period has elapsed. Further, in addition to the response delay time Rd, the backlight unit 109 turns on the LED of the line 2 after the time of (1 frame period) / (number of backlight control lines) = Ld has elapsed, for a predetermined lighting period. Turns off after elapses. In the same manner for other lines, the LED is switched between the on state and the off state.

  FIG. 8 is a diagram illustrating another example of the timing of turning on and off the backlight when performing backlight scanning. Here, it is assumed that the blinking frequency of the LED necessary for suppressing the moving image blur is 60 Hz, and the duty ratio for obtaining the necessary luminance is 50%. The LED driver 108 divides one frame period (1/60 Hz) into five subframe periods, and performs PWM control of the lighting period and extinguishing period of the LED of the backlight unit 109.

  In the example shown in FIG. 8, the LED driver 108 switches the duty ratio for each subframe. Specifically, the LED driver 108 sets the duty ratio to 0% during the subframe 1 and subframe 2 periods, and turns off the LEDs during the subframe 1 and subframe 2 periods. In the subframe 3 period, the LED driver 108 sets the duty ratio, which is the ratio of the lighting time to the subframe period, to 50%, so that the first half of the subframe 3 period is turned off and the second half is turned on. . The LED driver 108 sets the duty ratio to 100% in the period of the subframe 4 and the subframe 5, and turns on the LED in the period of the subframe 4 and the subframe 5. The LED driver 108 can blink the LED of the backlight unit 109 in the same state as when the light is emitted with the PWM signal having a duty ratio of 50% by switching between the lighting state and the light-off state in this way.

[Control of lighting timing based on image display size]
FIG. 9 is a diagram for explaining the operation of the display device 100 according to the first embodiment. FIG. 9A is an operation flowchart of the display device 100 according to the present embodiment. FIG. 9B is an example of a blinking frequency table used in the present embodiment. As shown in FIG. 9B, the blinking frequency table is set such that the larger the display size, the higher the blinking frequency. The blinking frequency table is stored in a memory included in the backlight control unit 107, for example.

Hereinafter, the operation of the display device 100 will be described with reference to FIG.
The CPU 101 monitors whether or not the user has changed the image display size via the operation input unit 106 (S101). When determining that the display size has been changed, the CPU 101 acquires size information indicating the changed display size from the operation input unit 106 (S102).

  Subsequently, the CPU 101 notifies the display size control unit 104 and the backlight control unit 107 of the changed display size. The display size control unit 104 converts the image data to be displayed on the display unit 105 based on the changed display size (S103). The display unit 105 displays an image based on the converted image data in the changed display size (S104).

  Further, the backlight control unit 107 controls the backlight unit 109 via the LED driver 108 in parallel with the image display processing of S103 and S104. Specifically, when the backlight control unit 107 receives a display size notification from the CPU 101, the backlight control unit 107 refers to the flashing frequency table and specifies the flashing frequency corresponding to the display size (S105). The backlight control unit 107 controls the lighting timing of the backlight unit 109 via the LED driver 108 so that the LED blinks at the specified blinking frequency (S106).

  The CPU 101 synchronizes with the vertical synchronization signal in order to synchronize the timing when the display unit 105 starts displaying the image after changing the display size and the timing when the backlight control unit 107 changes the blinking frequency of the backlight. The display size after the change may be notified to the display unit 105 and the backlight control unit 107 at the timing. For example, the CPU 101 notifies the display size to the display unit 105 and the backlight control unit 107 at the timing when the vertical synchronization signal is generated. By doing so, the display unit 105 starts displaying an image corresponding to the changed display size from the timing when the next vertical synchronization signal is generated, and the backlight control unit 107 displays the changed display size. The backlight unit 109 can be blinked at a blinking frequency corresponding to.

[Details of blinking pattern]
FIG. 10 is a diagram showing a blinking pattern of the backlight unit 109. FIG. 10A shows a blinking pattern when the drive frequency of the LED driver 108 is 300 Hz and the blinking frequency of the backlight unit 109 is changed to 180 Hz, 120 Hz, and 60 Hz. FIG. 10B shows the blinking pattern when the driving frequency and blinking frequency are the same as those in FIG. 10A and the lighting periods are different. In FIG. 10, the number N of blinking cycles (N is an integer of 1 or more), which is the number of blinking cycles included in the frame period, is N = 3 when the blinking frequency is 180 Hz, and N when the blinking frequency is 120 Hz. = 2 and N = 1 when the blinking frequency is 60 Hz.

  In FIG. 10, a period indicated by diagonal lines is a lighting period. In FIG. 10, the blinking cycle of the backlight unit 109 is an integral multiple of the driving cycle of the LED driver 108. The driving cycle is equal to the subframe period indicated as SF1 to SF5 in FIG. Therefore, the backlight control unit 107 can control the lighting timing in each blinking cycle by adjusting the duty ratio for each subframe period.

  The backlight control unit 107 stores the relationship between the number n of subframe periods included in the frame period (where n is an integer equal to or greater than 1) and the number N of blinking periods in association with the display size. Accordingly, the backlight unit 109 can be controlled with various lighting patterns. For example, assuming that the scanning frequency is 60 Hz, the backlight control unit 107 sets the flashing frequency to n = 5 and N = 3 when the display size is 100% of the screen size of the display unit 105. The backlight unit 109 can be controlled with a lighting pattern in which the number of blinking cycles is 3 at 180 Hz. Further, when the display size is 50% of the screen size, the backlight control unit 107 sets n = 5 and N = 2 so that the backlight pattern 107 has a lighting pattern with a blinking frequency of 120 Hz and a blinking cycle number of 2. The light unit 109 can be controlled.

The backlight control unit 107 determines the timing to turn on the backlight unit 109 in each blinking cycle according to the following procedure.
First, the backlight control unit 107 determines each blinking that is a ratio of the lighting period in each blinking period to the frame period based on the light emission ratio assigned to each of the N blinking periods included in one frame period. Determine the duty ratio of the period. Specifically, the backlight control unit 107 calculates the duty ratio Di of the blinking cycle Ni as Di = D × Ri, where Ri is the light emission ratio of the blinking cycle Ni (i is an integer of 1 or more). Here, D is a duty ratio corresponding to the light emission luminance required when N = 1. The light emission ratio is determined based on, for example, the response characteristics of the liquid crystal of the display unit 105, and the backlight control unit 107 can increase the light emission ratio as the elapsed time from the frame start timing is longer.

  Subsequently, the backlight control unit 107 determines the timing for turning on the backlight unit 109 for each subframe included in each blinking cycle. Here, the ratio of the lighting period in the blinking period Ni to the frame period is referred to as a duty ratio Di of the blinking period Ni.

  When the blinking cycle Ni includes one subframe, the backlight control unit 107 sets the lighting period in the subframe as a period corresponding to the duty ratio Di of the blinking cycle Ni. Specifically, the backlight control unit 107 performs control so that the backlight unit 109 is lit only during a period corresponding to Di with respect to the frame period in the subframe included in the blinking cycle Ni.

  When the plurality of subframes are included in the blinking period Ni, the backlight control unit 107 determines whether the duty ratio Di of the blinking period Ni is smaller than the maximum duty ratio d = 1 / n that can be assigned to one subframe. Determine whether or not. When the duty ratio Di of the blinking cycle Ni is smaller than the maximum duty ratio d = 1 / n, the backlight control unit 107 sets the duty ratio of one subframe included in the blinking cycle Ni as Di and the remaining subframes The duty ratio is 0% (lights off).

  When the duty ratio Di of the blinking cycle Ni is greater than or equal to the maximum duty ratio d = 1 / n, the backlight control unit 107 sets the duty ratio of one subframe included in the blinking cycle Ni to d = 1 / n. The backlight unit 109 is turned on during the subframe period. Subsequently, the backlight control unit 107 determines whether Di-d is smaller than the maximum duty ratio d = 1 / n. When Di-d is smaller than d, the backlight control unit 107 sets the duty ratio of the second subframe to Di-d and sets the duty ratio of the remaining subframes to 0%. The backlight control unit 107 repeats such a procedure to calculate the duty ratios of all the subframes and determine the lighting timing.

  For example, in the case of a pattern with a blinking frequency of 180 Hz shown in FIG. 10A, N = 3, n = 5, D = 0.6, R1 = 0.1, R2 = 0.3, R3 = 0.6 Then, D1 = 0.06, D2 = 0.18, and D3 = 0.36. In this case, the backlight control unit 107 calculates the duty ratio in the subframe SF1 corresponding to the blinking cycle 1 as 0.06. The LED driver 108 turns on the backlight unit 109 during a period of 0.06 × 5 = 0.3 in the subframe SF1 corresponding to the blinking cycle 1, and turns off the backlight unit 109 during a period of 0.7.

  The duty ratio D2 = 0.18 of the blinking cycle 2 is smaller than the maximum duty ratio d = 1/5 = 0.20 of the subframe. Therefore, the backlight control unit 107 calculates the duty ratio of one subframe SF3 included in the blinking cycle 2 as 0.18, and calculates the duty ratio of the remaining subframe SF2 as 0. The LED driver 108 turns off the backlight unit 109 during the subframe SF2. Further, the LED driver 108 turns on the backlight unit 109 during a period of 0.18 × 5 = 0.9 in the period of the subframe SF3 and turns off the backlight unit 109 during a period of 0.1.

  The duty ratio D3 = 0.36 of the blink period 3 is equal to or greater than the maximum duty ratio d = 1/5 = 0.20 of the subframe. Therefore, the backlight control unit 107 calculates the duty ratio of one subframe SF5 included in the blinking cycle 3 as 0.20, and calculates the duty ratio of the remaining subframe SF4 as 0.16. The LED driver 108 turns on the backlight unit 109 during the period of 0.16 × 5 = 0.8 in the period of the subframe SF4 and turns off the backlight unit 109 during the period of 0.2. In addition, the LED driver 108 lights the backlight unit 109 during the subframe SF5.

  In FIG. 10A, each blinking period starts from the extinguishing period, but the backlight control unit 107 can provide a lighting period in any period within each blinking period. Specifically, the backlight control unit 107 can start the blinking cycle from the lighting period and provide the extinguishing period after the lighting period ends. As shown in FIG. 10B, the backlight control unit 107 can also provide a lighting period in the middle of the blinking cycle.

  FIG. 11 is a diagram illustrating another example of the blinking pattern of the backlight unit 109. Specifically, FIG. 11 shows a blinking pattern when the drive frequency of the LED driver 108 is 180 Hz, 120 Hz, and 60 Hz and the blinking frequency of the backlight unit 109 is changed to 180 Hz, 120 Hz, and 60 Hz. In FIG. 11, the blinking cycle of the backlight unit 109 is equal to the driving cycle of the LED driver 108. The number of blinking cycles when the blinking frequency is 180 Hz is 3, the number of blinking cycles when the blinking frequency is 120 Hz is 2, and the number of blinking cycles when the blinking frequency is 60 Hz is 1.

  As shown in FIG. 11, the backlight control unit 107, when the drive frequency and the blinking frequency are equal, based on the light emission ratio assigned to each of the N blinking periods included in one frame period, The duty ratio is calculated for each subframe corresponding to the drive cycle.

  In both the case of FIG. 10 and the case of FIG. 11, the backlight control unit 107 may increase the duty ratio in the rear subframe within one frame period. By doing so, the backlight lighting period from the start of the frame period to the stabilization of the liquid crystal characteristics is shortened, and the backlight lighting period after the liquid crystal characteristics are stabilized is lengthened. Therefore, it is possible to reduce the motion blur.

[Effect in the first embodiment]
As described above, the display device 100 according to the first embodiment controls the lighting timing of the backlight based on the display size of the image. Specifically, the display device 100 makes it difficult to recognize flicker by increasing the blinking frequency or increasing the number of blinking cycles in a large display size in which flicker is easily recognized. Further, the display device 100 reduces motion blur by shortening the lighting period of the backlight unit 109 in a predetermined period after the frame period starts. On the other hand, in a small display size in which flicker is difficult to recognize, the display device 100 reduces the blinking frequency or the blinking cycle number so that the user cannot see the image before the liquid crystal characteristics are stabilized. By doing so, motion blur can be reduced.

<Second Embodiment>
[Control based on set brightness]
The display device 100 according to the second embodiment is different from the display device 100 according to the first embodiment in that the lighting timing of the backlight unit 109 is controlled based on the light emission luminance of the backlight unit 109. Same in terms.

  FIG. 12 is a diagram showing the relationship between light intensity and critical fusion frequency. The critical fusion frequency is the lowest frequency at which flicker can be recognized. From FIG. 12, it can be seen that, as the light intensity increases, the minimum frequency at which flicker can be recognized increases, so that at the same frequency, the greater the light intensity, the easier the flicker can be recognized. Therefore, the backlight control unit 107 according to the second embodiment controls the lighting timing of the backlight unit 109 so that the blinking frequency increases as the emission luminance of the backlight unit 109 increases.

  FIG. 13 is a table showing the relationship between the light emission luminance of the backlight unit 109 and the blinking frequency. When the backlight control unit 107 obtains the setting value of the light emission luminance of the backlight unit 109 from the CPU 101, the backlight control unit 107 determines the blinking frequency with reference to the table shown in FIG. Specifically, the backlight control unit 107 controls the LED driver 108 such that the blinking frequency increases as the duty ratio or the value of the current flowing through the LED increases.

  The display device 100 may control the lighting timing of the backlight unit 109 based on the image display size and the light emission luminance of the backlight unit 109 described in the first embodiment. FIG. 14 is a table showing the relationship between the display size, the light emission luminance of the backlight, and the blinking frequency. In the table shown in FIG. 14, a plurality of blinking frequencies are set for each emission luminance of the backlight in association with each display size. When the backlight control unit 107 receives a notification regarding the change in the display size of the image from the CPU 101, the backlight control unit 107 acquires the setting value of the light emission luminance of the backlight unit 109 from the CPU 101, and determines the blinking frequency with reference to the table shown in FIG. To do. Note that the backlight control unit 107 may control the number of blinking cycles instead of the blinking frequency based on the light emission luminance of the backlight unit 109.

[Effects of Second Embodiment]
The display device 100 according to the second embodiment controls the lighting timing of the backlight unit 109 based on the light emission luminance of the backlight unit 109. In this way, the display device 100 can make it difficult to recognize flicker even when the light emission luminance is high. Further, the display device 100 controls the blinking frequency based on the display size of the image and the light emission luminance of the backlight unit 109, so that the user can change the display size and the light emission luminance depending on the image content. Flicker can be made difficult to recognize, and moving image blur can be reduced.

<Third Embodiment>
[Control lighting timing based on external light intensity]
FIG. 15 is a diagram illustrating a configuration of a display device 200 according to the third embodiment. The display device 200 illustrated in FIG. 15 is different from the display device 100 illustrated in FIG. 3 in that it further includes a sensor 111 and a sensor control unit 112, and is the same in other respects. The backlight control unit 107, the LED driver 108, the backlight unit 109, the sensor 111, and the sensor control unit 112 constitute a light emission control device 250. The display device 200 according to the third embodiment is different from the display device 100 according to the first embodiment in that the lighting timing of the backlight unit 109 is controlled based on the intensity of external light.

  It is known that human eyes recognize flicker more easily when the environment in which the display device 100 is viewed is brighter. Therefore, the backlight control unit 107 according to the third embodiment controls the lighting timing of the backlight unit 109 so that the blinking frequency increases as the external light amount increases.

  The sensor 111 in the present embodiment detects the amount of external light around the display device 200. The sensor control unit 112 notifies the backlight control unit 107 of illuminance [lx] indicating the external light amount detected by the sensor 111. The backlight control unit 107 controls the lighting timing of the backlight unit 109 based on the illuminance received from the sensor control unit 112.

  FIG. 16 is a table showing the relationship between illuminance and blinking frequency. When the backlight control unit 107 acquires the illuminance from the sensor control unit 112, the backlight control unit 107 controls the blinking frequency of the backlight unit 109 with reference to the table shown in FIG. The backlight control unit 107 may control the lighting timing of the backlight unit 109 based on the display size and the illuminance. In this case, the backlight control unit 107 controls the lighting timing of the backlight unit 109 based on a table in which the display size, the illuminance, and the blinking frequency are associated. Note that the backlight control unit 107 may control the number of blinking cycles instead of the blinking frequency.

[Effect in the third embodiment]
The display device 200 according to the third embodiment controls the lighting timing of the backlight unit 109 based on the external light amount. In this way, the display device 200 can make it difficult to recognize flicker regardless of the surrounding environment.

<Fourth Embodiment>
[Control lighting timing based on viewing distance]
The fourth embodiment differs from the display device 200 according to the third embodiment in that the lighting timing of the backlight unit 109 is controlled based on the distance between the user and the display device 200, and is the same in other respects. is there. The sensor 111 in the fourth embodiment detects the distance to the user. The sensor 111 has a light source and a light receiving element. The sensor 111 irradiates light from an internal light source, and detects the distance based on the timing at which the light receiving element receives light reflected by the user as the measurement object.

  As the viewing distance of the user is shorter, the amount of light entering the user's eyes increases, and flicker is easily recognized. Therefore, the backlight control unit 107 according to the fourth embodiment controls the lighting timing of the backlight unit 109 so that the blinking frequency becomes higher as the viewing distance is shorter.

  FIG. 17 is a table showing the relationship between the viewing distance and the blinking frequency. In the table shown in FIG. 17, the blinking frequency when the viewing distance is less than 0.8 m is 180 Hz, and the blinking frequency when the viewing distance is 0.8 m or more is 60 Hz. When the backlight control unit 107 acquires information indicating the viewing distance from the sensor control unit 112, the backlight control unit 107 controls the blinking frequency of the backlight unit 109 with reference to the table illustrated in FIG.

  The backlight control unit 107 may control the lighting timing of the backlight unit 109 based on the display size and the viewing distance. In this case, the backlight control unit 107 controls the lighting timing of the backlight unit 109 based on a table that associates the display size, the viewing distance, and the blinking frequency. Note that the backlight control unit 107 may control the number of blinking cycles instead of the blinking frequency.

[Effects of the fourth embodiment]
The display device 200 according to the fourth embodiment controls the lighting timing of the backlight unit 109 based on the viewing distance. In this way, the display device 200 can make it difficult to recognize flicker regardless of the viewing position of the user.

<Fifth Embodiment>
[Control lighting timing based on installation direction]
The fifth embodiment differs from the display device 200 according to the third embodiment in that the lighting timing of the backlight unit 109 is controlled based on the direction in which the display device 200 is installed. is there. The sensor 111 in the fifth embodiment detects whether the display device 200 is installed horizontally or vertically.

  FIG. 18 is a diagram illustrating a state in which the display device 200 is installed sideways and a state in which the display device 200 is installed vertically. In the state where the display device 200 is installed in the horizontal direction, the visual field area H of the region included in the user's visual field in the display unit 105 is included in the user's visual field in the display unit 105 in the state where the display device 200 is installed in the vertical direction. It is larger than the visual field area V of the region. The larger the field of view, the greater the amount of light entering the user's eyes, making it easier to recognize flicker. Therefore, the backlight control unit 107 according to the fifth embodiment performs backlighting so that the blinking frequency when the display device 200 is installed in the horizontal direction is larger than the blinking frequency when the display device 200 is set in the vertical direction. The lighting timing of the light unit 109 is controlled.

  FIG. 19 is a table showing the relationship between the installation direction and the blinking frequency. In the table shown in FIG. 19, the blinking frequency in the state of being installed horizontally is 180 Hz, and the blinking frequency in the state of being installed vertically is 60 Hz. When the backlight control unit 107 acquires information indicating the installation direction from the sensor control unit 112, the backlight control unit 107 controls the blinking frequency of the backlight unit 109 with reference to the table shown in FIG.

  The backlight control unit 107 may control the lighting timing of the backlight unit 109 based on the display size and the installation direction. In this case, the backlight control unit 107 controls the lighting timing of the backlight unit 109 based on a table that associates the display size, the installation direction, and the blinking frequency. Note that the backlight control unit 107 may control the number of blinking cycles instead of the blinking frequency.

[Effects of Fifth Embodiment]
The display device 200 according to the fifth embodiment controls the lighting timing of the backlight unit 109 based on the installation direction. By doing so, the display device 200 can make it difficult to recognize flicker regardless of the installation direction.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment, A various deformation | transformation and change are possible within the range of the summary. is there. For example, in the above-described embodiment, the example in which the display unit 105 is a liquid crystal panel has been described. However, the present invention is not limited to this. For example, instead of the liquid crystal panel, a display panel having a display element other than the liquid crystal element may be used as a display element that transmits light from the light emitting means.

  In the above embodiment, the configuration in which the backlight control unit 107 that controls the lighting timing of the backlight unit 109 based on the display size of the image is incorporated in the display device 100 and the display device 200 has been described. Part of the display device 100 may be provided as a separate unit. For example, the display device 100 may be configured by combining the light emission control device 150 including the backlight control unit 107, the LED driver 108, and the backlight unit 109 with a liquid crystal display unit including the display unit 105.

DESCRIPTION OF SYMBOLS 100 Display apparatus 105 Display part 107 Backlight control part 109 Backlight part 150 Light emission control apparatus

Claims (12)

Light emitting means for irradiating the display means with light;
Control means for controlling a lighting timing which is a timing at which the light emitting means turns on the light emitted to the display means based on a display size of an image displayed on the display means;
A light emission control device comprising: The control means repeats turning on and off the light that the light emitting means irradiates the display means at a blinking frequency based on the display size,
The light emission control device according to claim 1. The control means increases the blinking frequency as the display size is larger.
The light emission control device according to claim 2. As the display size is larger, the control means has a number of blinking periods, each of which includes one lighting period and at least one extinguishing period of light that the light emitting means irradiates the display means within a predetermined period. Characterized by increasing
The light emission control apparatus of any one of Claim 1 to 3. The control means increases the lighting period of light that the light emitting means irradiates the display means as time elapses from the frame switching timing in the display means.
The light emission control apparatus of any one of Claim 1 to 4. The control means controls the lighting timing based on the luminance of light emitted by the light emitting means.
The light emission control device according to any one of claims 1 to 5. Photodetection means for detecting an external light amount indicating the intensity of external light around the display means,
The control means controls the lighting timing based on the external light amount,
The light emission control device according to any one of claims 1 to 6. A distance detection means for detecting a distance between the display means and a user viewing the display means;
The control means controls the lighting timing based on the distance.
The light emission control apparatus of any one of Claim 1 to 7. Direction detecting means for detecting the direction of the display means;
The control means controls the lighting timing based on the orientation of the display means.
The light emission control apparatus of any one of Claim 1 to 8. A light emitting means for irradiating light to a display means for displaying an image;
Control means for controlling the timing at which the light emitting means turns on the light emitted to the display means based on the luminance of the light emitted by the light emitting means;
A light emission control device comprising: Display means for displaying an image;
Obtaining means for obtaining size information indicating a display size of an image to be displayed on the display means;
A light emitting means for irradiating the display means with light;
Based on the size information, a control unit that controls a lighting timing that is a timing at which the light emitting unit turns on the light applied to the display unit;
A display device comprising: A procedure for obtaining size information indicating a display size of an image to be displayed on the display means;
Based on the size information, a procedure for controlling a lighting timing that is a timing for lighting the light irradiating the display means;
The light emission control method characterized by having.