JP2013218173A - Illuminating device, control method therefor, and backlight device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an illuminating device including a plurality of blocks each of which can be controlled independently, in which fluctuation of brightness in a screen occurring when brightness of each block is measured with a sensor is suppressed.SOLUTION: An illuminating device includes: control means for controlling brightness of a light source by way of pulse width modulation control; and measurement means for measuring brightness of a light source as a measurement target by receiving light from the light source as a measurement target for a prescribed measurement period. In the illuminating device, when the brightness of the light source as a measurement target is measured by the measurement means, the control means: forcibly turns off a light source, for which a measurement period by the measurement means exists during a light emission period originally determined by way of a pulse width modulation control, out of light sources which are not the measurement target; and in at least either a cycle for forcible light-turning-off or a cycle which comes before or after the cycle and is adapted to extend the light emission period originally determined by way of pulse width modulation control, extends, by way of pulse width modulation control, the originally determined light emission period so that luminance reduction caused by the forcible light-turning-off of the light source can be compensated.

Description

  The present invention relates to a lighting device, a control method thereof, and a backlight device.

In recent years, liquid crystal display devices have become mainstream as image display devices. Since a liquid crystal panel is not a self-luminous device, a backlight using a light source such as an LED is required. In addition, as a method of adjusting the luminance of an image with a liquid crystal display, there are a method of adjusting luminance by controlling liquid crystal and a method of adjusting the luminance of backlight. By using the method of adjusting the luminance by the backlight, it is possible to increase the contrast ratio in the screen, and there is an advantage that power consumption can be suppressed.

PWM control (pulse width modulation control) is often used as a means for adjusting the brightness of the backlight. In the PWM control, the backlight is turned on and off at a constant cycle, and the luminance of the backlight is adjusted by changing the ratio (duty ratio) between the turn-on period and the turn-off period. When the cycle of turning on and off is long, the blinking of light is visually recognized by human eyes, and flicker may be felt. For this reason, it is common to perform PWM control of the backlight at a high frequency of 200 Hz or higher. Therefore, for example, if the frame frequency of the image is 60 Hz, the backlight is repeatedly turned on and off a plurality of times during one frame of the image.

Many LEDs are laid in the backlight using LEDs. The number of LEDs varies depending on the size of the display screen and the required brightness. Here, as shown in Fig. 2 (A), the backlight can be divided into 10 areas each consisting of one or more LEDs, and the light emission of the LEDs in each area can be controlled independently. It is assumed that the phase can be made different. FIG. 18 shows an example of a time chart of PWM control when the LEDs in all areas are turned on and off with the same phase. In FIG. 18, the horizontal axis represents time, and the vertical axis represents the amount of current. The blacked out part represents the lighting period, and the other part represents the extinguishing period. The sum of the current amounts in each area is the total current.

As can be seen from the total current in FIG. 18, when PWM control of the same phase is performed in all areas, the time variation of the total current amount increases in one cycle of PWM control. If the amount of current fluctuates greatly as described above, power efficiency is lowered and power consumption is increased. In addition, it is necessary to design the power supply of the backlight so that it can withstand large fluctuations, leading to higher costs. Therefore, as a technique for suppressing the fluctuation of the total current amount, there is a method of shifting the phase of the PWM signal for each area. For example, Patent Document 1 discloses a technique for turning on the backlight by shifting the phase for each area. FIG. 19 shows an example of a time chart of PWM control in the case where lighting is performed by shifting the phase of the PWM signal for each area. As shown in FIG. 19, by shifting the phase of the PWM signal for each area, it is possible to suppress significant fluctuations in the total current.

As described above, in order to suppress flicker, the backlight is generally blinked at a high frequency with respect to the frame frequency of the image.
There is also a technique for making the frequency of the same as the frame frequency of the image. The liquid crystal panel has low responsiveness compared to a self-luminous device such as a cathode ray tube display or a plasma display, so that moving image display may be noticeable when moving images are displayed. One technique for suppressing motion blur is a technique called backlight scanning. Backlight scanning is a technique for reducing moving image blur by turning off the backlight in accordance with the scanning (scanning) of the liquid crystal and making the moment of switching of the liquid crystal invisible. This technique is disclosed in Patent Document 2 and the like.

In addition, there is an individual difference (variation) in the luminance of the LED, and even if lighting is performed with a PWM signal having the same current amount and the same duty ratio, a luminance difference occurs for each LED. In addition, the brightness varies from LED to LED due to temperature differences in the screen and deterioration due to aging. In addition, even when a plurality of LEDs are connected in series to form an LED block and control is performed for each LED block, luminance variation occurs for each LED block due to LED luminance variation. The variation in the luminance of each LED block becomes the luminance unevenness of the backlight and affects the display image. In order to enable high-quality image display, it is necessary to accurately grasp the variation in brightness of each LED block, and to reduce the uneven brightness of the backlight by changing the duty ratio of the PWM signal for each LED block. Is effective.

As a method of suppressing the luminance unevenness of the backlight, there is a method of performing control such as obtaining a variation in luminance of the LED block using a luminance sensor and changing the duty ratio for each LED block based on the obtained result. Here, in order to accurately acquire the luminance sensor value for each LED block, it is effective to turn on only the corresponding LED block and turn off the other LED blocks to suppress the influence on the measurement value due to light leakage. However, as described above, when controlling the light emission by changing the phase of the PWM signal for each backlight area, the LED block in any area of the backlight is always lit unless the duty ratio is extremely low. ing.

For this reason, there is almost no opportunity to enter a lighting state in which all the LED blocks other than the LED block to be measured are turned off. When the display is not used, it is also possible to measure by turning on only the LED block for obtaining the sensor value and turning off all other LED blocks. However, since the change in the light emission characteristics of the LED block may occur even during use of the display, it is preferable to measure the luminance even during use of the display.

Therefore, all the LED blocks other than the LED block that is the sensor value acquisition target are turned off during the predetermined sensor value acquisition period, and the sensor value of the LED block that is the sensor value acquisition target is acquired. Control to return to can be considered. Here, it is assumed that the sensor value acquisition period is long enough to measure the luminance of the LED block to be measured by the optical sensor and is short enough not to be visually recognized by human eyes.

FIG. 20 shows an example of a time chart of PWM control before and after the sensor value acquisition period when one block in area 1 is a sensor value acquisition block. As shown in FIG. 20, in the sensor value acquisition period, only the sensor value acquisition block in area 1 is lit, and other LED blocks in area 1 (non-sensor value acquisition block) and all LED blocks in other areas Is forcibly turned off. By acquiring the value measured by the luminance sensor during this sensor value acquisition period, it is possible to measure the luminance of the LED for one block. If the same measurement is performed while changing the LED block to be lit, the luminance of all the LED blocks can be measured.

JP 2010-153359 A Japanese Patent Laid-Open No. 11-202286

As described above, when the LEDs other than the sensor acquisition block are extinguished for a moment, the extinguishing itself is momentary, and thus it is difficult for human eyes to visually recognize. However, since the actual duty ratio is reduced by the amount of light that has been extinguished, the luminance of the entire backlight is slightly reduced. Figure
In the example shown in Fig. 20, the actual lighting period in the PWM cycle in which sensor value acquisition is performed is shortened by turning off LED blocks other than the sensor value acquisition block in area 1 due to sensor value acquisition in the sensor value acquisition block. The brightness of 1 decreases. In areas 7, 8, 9, and 10, since the lighting period in which lighting starts in the previous PWM cycle is shortened, the luminance similarly decreases.

On the other hand, in areas 2 to 6, since the sensor value acquisition timing corresponds to the extinguishing period in the PWM control, the luminance does not change. Therefore, with the forced turn-off due to this sensor value acquisition, a difference in luminance depending on the area occurs. At this time, whether or not the luminance is reduced also varies depending on the set PWM duty ratio. For example, even in the same area, there may be both an LED block in which the luminance is reduced and a LED block in which the luminance is not reduced if the duty ratio setting is different for each LED block.

FIG. 21 schematically shows the luminance distribution of the backlight based on PWM control for two cycles including the sensor value acquisition period when the duty ratios of the LED blocks in the same area are all the same. As shown in FIG. 21, the brightness of the non-sensor value acquisition block of area 1 and areas 7 to 10 that are forcibly turned off during the sensor value acquisition period are the brightness of the sensor value acquisition block of area 1 and the areas 2 to 6 It is low compared.

FIG. 22 shows an example of a time chart of PWM control before and after the sensor value acquisition period when one block in area 4 is a sensor value acquisition block. In the example of FIG. 22, in the PWM cycle including the sensor value acquisition period, the luminance is reduced due to forced extinction in the non-sensor value acquisition block in areas 1, 2, 3 and area 4. In addition, in area 10, since the forced turn-off is performed during the lighting period started in the previous PWM cycle, the luminance similarly decreases. FIG. 23 schematically shows the luminance distribution of the backlight based on PWM control for two cycles including the sensor value acquisition period.

  As shown in FIGS. 21 and 23, when the area to which the sensor value acquisition block belongs changes, the area in which the luminance decreases due to forced turn-off accompanying sensor value acquisition also changes. Therefore, if sensor values are acquired for each LED block of the backlight one block at a time, the luminance of some areas in the screen continues to decrease during the period when sensor values are acquired.

For example, assuming that sensor values are acquired once per image frame (60 Hz), and each area consists of 20 LED blocks, the total number of LED blocks is 200, and all LED block sensors It takes about 3.3 seconds to get the value. In this case, the brightness will fluctuate within the screen for 3.3 seconds, but since the human eye is sensitive to changes in brightness at low frequencies, this change in brightness is easily visible to the viewer's eyes. It will be recognized as a drop in image quality.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a technique for suppressing fluctuations in luminance in a screen when measuring luminance for each block by a sensor in a lighting device composed of a plurality of blocks capable of independently controlling light emission. .

The present invention includes a plurality of light sources capable of independently controlling light emission,
Control means for controlling the luminance of the light source by pulse width modulation control for adjusting the duty ratio between the lighting period and the extinguishing period within a predetermined period;
Measuring means for measuring the luminance of the light source to be measured by receiving light from the light source to be measured over a predetermined measurement period;
With
When the measuring means measures the luminance of the light source to be measured by the measuring means, among the light sources that are not the measuring object, the measuring period by the measuring means exists during the lighting period initially determined by the pulse width modulation control. The light source is forcibly turned off during the measurement period, and the light source is forcibly turned on at least one of a period for which the light is forcibly turned off, or a period before and after the period for which the light source is forcibly extinguished. It is an illuminating device that extends the lighting period of the light source, which is initially determined by pulse width modulation control so as to compensate for a decrease in luminance due to extinction.

The present invention includes a plurality of light sources capable of independently controlling light emission,
Measuring means for measuring the luminance of the light source to be measured by receiving light from the light source to be measured over a predetermined measurement period;
A method for controlling a lighting device comprising:
A control step of controlling the luminance of the light source by pulse width modulation control for adjusting the duty ratio of the lighting period and the extinguishing period within a predetermined period;
When measuring the luminance of the light source to be measured by the measurement means, among the light sources that are not the measurement target, the light source having the measurement period by the measurement means during the lighting period initially determined by the pulse width modulation control is measured. In at least one of the period in which the light source is forcibly turned off in the period and the period for which the light source is forcibly turned off, or the period before and after that, and the lighting period initially determined by the pulse width modulation control can be extended, And a step of extending the lighting period of the light source initially determined by the pulse width modulation control so as to compensate.

  ADVANTAGE OF THE INVENTION According to this invention, in the illuminating device which consists of a some block which can control light emission independently, the fluctuation | variation of the brightness | luminance in a screen at the time of measuring the brightness | luminance for every block with a sensor can be suppressed.

FIG. 1 is a block diagram illustrating a schematic configuration of an image display apparatus according to a first embodiment. The figure which shows the lighting state at the time of sensor division of area division and area 1 of the backlight The figure which shows PWM control of Example 1 The figure which shows PWM control of the compensation of the brightness | luminance reduction by sensor value acquisition of Example 1 The figure explaining the determination method of the presence or absence of the forced light extinction accompanying sensor acquisition in Example 1. The figure which shows PWM control of the compensation of the brightness | luminance reduction by sensor value acquisition of Example 1 The figure which shows PWM control of Example 1 The figure which shows PWM control of the compensation of the brightness | luminance reduction by sensor value acquisition of Example 1 The figure which shows the PWM control at the time of the backlight scan of Example 2. The figure which shows PWM control at the time of sensor value acquisition of Example 2 The figure which shows PWM control of the compensation of the brightness | luminance fall by sensor value acquisition of Example 2 The figure which shows the PWM control at the time of the backlight scan of Example 2. The figure which shows PWM control at the time of sensor value acquisition of Example 2 The figure which shows PWM control of the compensation of the brightness | luminance fall by sensor value acquisition of Example 2 The figure which shows PWM control at the time of sensor value acquisition of Example 3 The figure which shows PWM control of the compensation of the brightness | luminance reduction by sensor value acquisition of Example 3 The figure which shows PWM control at the time of sensor value acquisition of Example 3 Diagram showing PWM control in the prior art Diagram showing PWM control in the prior art Diagram showing PWM control at the time of sensor value acquisition in the prior art The figure explaining the brightness nonuniformity which arises by sensor value acquisition in a prior art Diagram showing PWM control at the time of sensor value acquisition in the prior art The figure explaining the brightness nonuniformity which arises by sensor value acquisition in a prior art

Example 1
A first embodiment of the present invention will be described. FIG. 1 is a block diagram showing an outline of an image display device including the illumination device of the present invention as a backlight device. The image display apparatus 100 analyzes the image signal input from the image input unit 101 by the image analysis unit 102, and determines the luminance of the display image and the backlight. The LCD control unit 103 controls the LCD panel 104 so that the image determined by the image analysis unit 102 can be displayed, and aligns the liquid crystal of each pixel of the LCD panel 104 so that the image can be displayed. The backlight control unit 105 sets a necessary current value, a PWM duty ratio, and the like for the LED driver 106 so that the backlight luminance determined by the image analysis unit 102 is realized.

The LED driver 106 has a plurality of channels, and each channel has a backlight 107.
Are connected to an LED block which is a light source capable of independently controlling light emission.
Here, it is assumed that the LED blocks are a plurality of light emitting blocks arranged in the vertical direction and the horizontal direction of the backlight. The LED driver 106 performs pulse width modulation control (PWM) that adjusts the duty ratio between the lighting period and the extinguishing period within a predetermined period under the conditions set by the backlight control unit 105.
Control) to control the brightness of the LED block.

  The luminance sensor 108 receives the light emitted from the backlight 107 for a predetermined measurement period, measures the luminance of the LED block to be measured, and outputs the measurement result to the sensor control unit 109. The sensor control unit 109 operates in synchronization with the backlight control unit 105. That is, the backlight control unit 105 turns off the non-sensor value acquisition LED blocks that are LED blocks other than the LED block that is the sensor value acquisition target during the period when the sensor value acquisition is performed by the sensor control unit 109.

The sensor control unit 109 acquires the luminance of the sensor value acquisition target LED block by acquiring the output value from the sensor 108 during the sensor value acquisition period. The sensor control unit 109 feeds back the sensor value for each LED block to the backlight control unit 105. Based on the sensor value for each LED block acquired from the sensor control unit 109, the backlight control unit 105 adjusts the PWM control by the LED driver 106 so as to minimize the luminance unevenness of the backlight 107. The backlight 107 irradiates the LCD panel 104, and the irradiated light is transmitted according to the transmittance of each pixel of the LCD panel 104, whereby an image that can be observed by the observer is displayed on the image display unit 110.

Next, details of the sensor value acquisition method will be described. As shown in FIG.
Are divided into 10 areas in the vertical direction of the screen, and the backlight control unit 105 controls the light emission of the backlight 107 by shifting the phase of the PWM signal for each area. Each area is composed of multiple LED blocks, and one or more LEDs are placed in one LED block, and the light emission is controlled by changing the current value and PWM duty ratio setting independently for each LED block. It is assumed that the configuration is possible.

One frame period of the image signal is a period corresponding to a plurality of periods of the PWM signal for controlling the light emission of the LED block. In this embodiment, as an example, the frame frequency of the image signal is 60 Hz, and the frequency of the PWM signal is 300 Hz. FIG. 3 shows an example of a timing chart of PWM control in each area at the normal time when sensor value acquisition is not performed.

In the PWM control of this embodiment, one cycle (PWM cycle) of the PWM signal starts from the lighting period, the length of the lighting period is determined by the duty ratio, and after the lighting period ends, the extinguishing period starts, It is assumed that the PWM cycle ends at the end timing. By changing the duty ratio, the timing of shifting from lighting to extinguishing changes, and the length of the lighting period changes. In addition, the time until the lighting of each area starts when the PWM reference position is the starting point is defined as DELAY_n (n: 1 to 10). The PWM reference position is a timing that serves as a reference for the phase of the PWM signal, and is determined based on, for example, the position of the vertical synchronization signal of the image signal.

In FIG. 3, the frame period of the image signal is divided into five by the PWM period, and the PWM reference position coincides with the vertical synchronization signal every five PWM periods. However, this method of determining the PWM reference position is an example, and the vertical synchronization signal of the image signal and the PWM reference position do not have to match. In this embodiment, it is assumed that DELAY_1 is 0 and the lighting start position of area 1 is equal to the PWM reference position. In this embodiment, it is assumed that the phase (DELAY_n) of the lighting start position with respect to the PWM reference position can be varied for each area. In the example of FIG. 3, the duty ratio is common to each area at 50%, but the lighting start position (PWM cycle start timing) is different for each area.

FIG. 2 (B) is a diagram schematically showing the lighting state of the backlight 107 during the sensor value acquisition period for acquiring the sensor value of one LED block in area 1. FIG. As shown in FIG. 2 (B), in the image display device of the present embodiment, only one LED block is turned on during the sensor value acquisition period, and the other LED blocks are turned off. The brightness of the LED block is measured by obtaining the output value. During the sensor value acquisition period, the sensor control unit 109 forcibly turns off the LED blocks (non-sensor value acquisition LED blocks) other than the sensor value acquisition target LED block.

The forced turn-off of the non-sensor value acquisition LED block by the sensor control unit 109 can be realized by various methods. For example, a switch for interrupting the current is provided for each LED block, and the sensor control unit 109 switches the switch to cut off the current flowing through the LED block, thereby forcibly turning off the light. In addition, the sensor control unit 109 controls the LED driver 106 to instruct the LED driver 106 that drives the non-sensor value acquisition LED block to set the current value to 0, thereby turning off the non-sensor value acquisition LED block. May be performed. Alternatively, the sensor control unit 109 may turn off the non-sensor value acquisition LED block by instructing the backlight control unit 105 to set the current of the non-sensor value acquisition LED block to 0.

In any case, in this embodiment, it is assumed that the sensor control unit 109 has means (function) for turning off the non-sensor value acquisition LED block. In either case, the sensor control unit 109
Assume that the backlight control unit 105 is notified in advance of information related to the sensor value acquisition operation (information such as the position of the sensor value acquisition block). The sensor control unit 109 has means for acquiring information on the phase of the PWM signal in each area and lighting start timing, and can acquire the sensor value of the LED block in each area at an appropriate timing.

First, a case where the luminance of one LED block in area 1 is measured will be described. In order to measure the luminance of a certain LED block, it is necessary to acquire the sensor value within the lighting period of the area to which the LED block belongs. The length of the lighting period varies depending on the duty ratio setting. If the duty ratio is small, the lighting period is short and the sensor value acquisition period can be set short, but if the duty ratio is not 0, the PWM cycle start timing of each area, that is, the DELAY_N timing relative to the PWM reference position Then, area N is always lit.

Therefore, in this embodiment, the sensor value acquisition of the LED block in area N is performed at the timing of DELAY_N from the PWM reference position. FIG. 4 shows an example of a timing chart of the PWM control when the sensor value acquisition of the LED block in area 1 is performed. PWM cycles 1 to 3 in the figure are DELAY_1
Indicates the PWM cycle of area 1 when 0 is 0. If DELAY_1 increases, area 1 is increased accordingly.
PWM cycles 1 to 3 will also shift to the right.

In the example of FIG. 4, the duty ratio of each area is common at 50%. When performing sensor value acquisition, LED blocks other than the sensor value acquisition LED block (non-sensor value acquisition LED block) are forcibly turned off during the sensor value acquisition period. In the example of FIG. 4, the sensor value of the LED block in area 1 is acquired in the PWM cycle 2 in area 1. Therefore, PWM cycle 1 area 7, 8, 9, 10 and PWM
In the lighting period of the non-sensor value acquisition block in area 1 of cycle 2, the period corresponding to the sensor value acquisition period of area 1 in PWM cycle 2 is forcibly set as the extinguishing period.

In this embodiment, as described above, an LED block in which a part of the PWM lighting period is forcibly set to the extinguishing period is obtained as the sensor values of other LED blocks are acquired. Then, the setting of the PWM duty ratio of these LED blocks that are forcibly turned off is changed in advance to suppress a decrease in luminance of the LED blocks that are forcibly turned off.

In FIG. 4, communication 1 to 3 from the backlight control unit to the LED driver is for the backlight control unit 105 to set the duty ratio of each LED block in the PWM periods 1 to 3 for the LED driver 106. Represents communication.

In the example of FIG. 4, the backlight control unit 105 is set to increase the duty ratio of the PWM in the areas 7, 8, 9, and 10 in the PWM cycle 1 by communication 1. Through the next communication 2, the backlight control unit 105 sets the duty ratio of the non-sensor value acquisition LED block in area 1 in the PWM cycle 2 and increases the duty ratio of the PWM in areas 7, 8, 9, and 10. Set the ratio back to its original value. Through the next communication 3, the backlight control unit 105 sets the duty ratio of the non-sensor value acquisition LED block in area 1 in the PWM cycle 3 to be restored.

In this way, the duty ratio of the LED block subject to forced turn-off is made longer than the original value (50% in FIG. 4) in advance so that the substantial shortening of the lighting period due to forced turn-off is compensated for, The end timing of the lighting period is made later than the original timing. As a result, it is possible to suppress fluctuations in the luminance of the backlight before and after the PWM cycle in which sensor value acquisition is performed.

Next, the presence / absence of a specific duty ratio change and a method for determining the duty ratio after the change will be described. FIG. 5 (A) shows a method of determining the duty ratio in PWM cycle 1. Initially defined LED
When the lighting time of the block is set to DUTY, the LED block in area n (n = 1 to 10) starts lighting from DELAY_n with PWM reference position 1 as the reference and lights up to "DELAY_n + DUTY" become. Further, the length of one PWM period is T_pwm, and the DELAY time of the area to which the sensor value acquisition LED block belongs is DELAY_s. At this time, the sensor value acquisition period is a period from “T_pwm + DELAY_s” to “T_pwm + DELAY_s + sensor value acquisition time”. Therefore, in the non-sensor value acquisition LED block belonging to the area n satisfying the following expression, a part of the PWM lighting period is forcibly set to the extinguishing period with the sensor value acquisition of the other LED blocks.

DELAY_n <T_pwm + DELAY_s + sensor value acquisition time <DELAY_n + DUTY

For the non-sensor value acquisition LED block belonging to the area n that satisfies the above formula, the PWM duty ratio in the PWM cycle 1 is reset to “DUTY + sensor value acquisition time”. Thereby, the fall of the brightness | luminance by forced light extinction accompanying sensor value acquisition of another LED block can be suppressed.

Next, a method for setting the PWM duty ratio in the PWM cycle 2 will be described with reference to FIG. In the PWM cycle 2, the LED block in the area n starts lighting from the time of DELAY_n with the PWM reference position 2 as a reference, and lights up to “DELAY_n + DUTY”. On the other hand, the period during which sensor values are acquired is a period from DELAY_s to “DELAY_s + sensor value acquisition time”. Therefore, the non-sensor value acquisition LED block belonging to the area n satisfying the following formula is
A part of the lighting period of the PWM is forcibly set to the extinguishing period with the sensor value acquisition of the other LED blocks.

DELAY_n <DELAY_s + sensor value acquisition time <DELAY_n + DUTY

For the non-sensor value acquisition LED block belonging to the area n that satisfies the above formula, the PWM duty ratio in the PWM cycle 2 is reset to “DUTY + sensor value acquisition time”. As a result, it is possible to suppress a decrease in luminance due to forced turn-off due to sensor value acquisition of other LED blocks. FIG. 6 is a timing chart showing PWM control in the case where sensor value acquisition is performed for the LED block in area 4, which is obtained based on the above-described determination method. When sensor value acquisition is performed for LED blocks in area 4 in PWM cycle 2, the PWM duty ratio in area 10 is increased in PWM cycle 1, and non-sensor value acquisition blocks in areas 1 to 3 and area 4 in PWM cycle 2 Increase the PWM duty ratio. Thereby, the brightness | luminance fluctuation | variation of the backlight 107 can be suppressed.

Next, the case where the PWM signal starts from the extinguishing period and the lighting period starts after the extinguishing period ends will be described. As shown in FIG. 7, in this case, the time from the PWM reference position to the start of extinguishing (PWM cycle start) is defined as DELAY_n. In the case of PWM control in which the PWM signal starts from the extinguishing period, when the duty ratio becomes small, the LED is turned on only at the end of the PWM cycle. Therefore, in the case of PWM control in which the PWM signal starts from the extinguishing period, in this embodiment, the sensor value is acquired at the end timing of the PWM cycle.

FIG. 8 (A) shows an example of a timing chart when the sensor value of the LED block in area 1 is acquired in the PWM control in which the PWM signal starts from the extinguishing period. In the example of FIG. 8 (A), along with the sensor value acquisition of area 1, the forced turn-off period is set during the PWM turn-on period in areas 1 (non-sensor value acquisition block) and areas 2 to 5 of PWM cycle 1. . Therefore, in the present embodiment, in the communication 1 of FIG. 8A, a setting value that extends the PWM lighting period of the area 1 (non-sensor value acquisition block) and the areas 2 to 5 is transmitted from the backlight control unit 105 to the LED. It is transmitted to the driver 106.

In the case of PWM control in which the PWM signal starts from the light-off period, the luminance compensation of the LED block that is forcibly turned off is performed by extending the PWM light-on period forward as shown in FIG. 8 (A).
In other words, by reducing the lighting start timing (making the extinguishing end timing earlier), the luminance reduction due to forced extinction is compensated. Further, as shown in FIG. 8 (A), in the PWM cycle 2, no forced turn-off period is set in the PWM turn-on period in any area. Accordingly, the backlight control unit 105 instructs the LED driver 106 to return the duty ratios of all areas to the original set values in the communication 2.

  Similarly, the backlight control unit 105 transmits the same setting value as that in the communication 2 in the communication 3. As shown in FIG. 8A, the backlight control unit 105 does not have to perform the communication 3 itself because there is no influence of the luminance decrease accompanying the sensor value acquisition of the area 1 after the PWM cycle 2.

FIG. 8B shows an example of a timing chart when the sensor value of the LED block in the area 9 is acquired in the PWM control in which the PWM signal starts from the extinguishing period. In the example of Fig. 8 (B), during the lighting period of the PWM of area 9 of PWM cycle 1 (non-sensor value acquisition block), area 10, and areas 1 to 3 of PWM cycle 2 with the sensor value acquisition of area 9 Is set to the forced extinction period.

Therefore, in this embodiment, in the communication 1 in FIG. 8B, a setting value that extends the PWM lighting period of the area 9 (non-sensor value acquisition block) and the area 10 is transmitted from the backlight control unit 105 to the LED driver 106. Sent to. In communication 2, a setting value that extends the PWM lighting period of areas 1 to 3 is transmitted from the backlight control unit 105 to the LED driver 106.

In the present embodiment, an example has been described in which the timing of communication with the LED driver 106 is set before the PWM reference position of the PWM cycle in which there is an LED block that needs to be subjected to luminance compensation. However, if the LED driver 106 can change the duty ratio of the LED block that needs to perform luminance compensation, the communication timing to the LED driver 106 is as shown in FIG. 4, FIG. 6, FIG. 8 (A), FIG. It does not have to be the same as the timing shown in B). In the present embodiment, the sensor control unit 109 performs sensor value acquisition and notifies the backlight control unit 105 of sensor value acquisition LED block information before the timing of performing this communication.

By acquiring the sensor value of the LED block using the method of the present embodiment, it is possible to suppress the variation in the luminance of the backlight due to the acquisition of the sensor value, and it is possible to suppress the deterioration of the image quality. .

(Example 2)
In the second embodiment, a method for acquiring sensor values in a backlight that performs backlight scanning will be described. Constituent elements equivalent to the constituent elements described in the first embodiment are not described in detail by using the same names and reference numerals as those in the first embodiment. When performing backlight scanning, the backlight is turned on and off at the same frequency (for example, 60 Hz) as the frame frequency of the image signal.

As a method for this, there is a method of blinking the backlight at a frequency lower than the PWM frequency of the LED driver 106 by changing the PWM duty ratio for each period without changing the PWM frequency of the LED driver 106. Here, using FIG. 9, the PWM signal of the LED driver 106 is a PWM signal with a driving frequency of 300 Hz, and this PWM signal is used to perform backlight scanning by blinking the backlight with a duty ratio of 50% and a blinking frequency of 60 Hz. explain. Here, it is assumed that the PWM signal of the LED driver 106 is a PWM signal having a specification starting from the lighting period and ending in the extinguishing period. In this case, the light source is driven in units of a plurality of periods including at least one of a period with a duty ratio of 100% and a period with a duty ratio of 0% and one period with a duty ratio of 100% or less.

Taking the case of area 1 as an example, the duty ratio is set to the maximum (100%) in PWM cycle 1.
Next, in the PWM cycle 2, the duty ratio is similarly set to 100%. In the next PWM cycle 3, the duty ratio is set to 50%. In the next PWM cycle 4 and PWM cycle 5, the duty ratio is set to 0%. As described above, by driving the backlight in units of multiple cycles of the PWM signal, it is possible to perform blinking that switches from lighting to unlit only once in image frame 1, that is, blinking at 60 Hz become. If the same duty ratio is set in the next image frame 2 (PWM cycle 6 to 10), lighting and extinguishing at 60 Hz are repeated.

Note that in FIG. 9, a slight gap is shown between PWM cycles so that the breaks in the PWM cycle can be seen, but this is for convenience to make the drawing easier to understand, and actually during the lighting period There are no gaps. Further, “PWM cycles 1 to 10” in FIG. As described in the first embodiment, the phase of the PWM cycle with respect to the PWM reference position can be varied for each area.

In the example of FIG. 9, it is assumed that the PWM cycle of the odd area is the same as that of area 1, and the PWM cycle of the even area is set to have a phase shift of a half cycle with respect to the odd area. The position of the starting point of the PWM cycle for each area is not limited to the present embodiment because it is determined by how much the lighting phase is shifted for each area.

In order to perform backlight scanning effectively, it is necessary to shift the lighting phase for each area. Taking the case of area 5 as an example, the duty ratio is set to 0% in PWM cycles 1 and 2, the duty ratio is set to 100% in PWM cycles 3 and 4, and the duty ratio is set to 50% in PWM cycle 5. As a result, the area 5 can be blinked at 60 Hz with a delay of a certain time (here, two PWM cycles) with respect to the area 1.

  Similarly, by changing the duty ratio for each PWM cycle for each area, it is possible to cause blinking at a frequency different from the original PWM frequency (drive frequency by the LED driver 106). In this embodiment, a method of suppressing the luminance variation of the backlight accompanying the sensor value acquisition of the LED block when performing the PWM control for blinking the backlight at the blinking frequency different from the drive frequency as described above will be described in this embodiment.

FIG. 10A shows an example of a time chart of PWM control in the case where sensor values of LED blocks in area 1 are acquired. 10 (B) and 10 (C) are enlarged views of part of FIG. 10 (A). In area 1, if the duty ratio (duty ratio for the entire image 1 frame period) when viewed in the blinking cycle of the backlight scan is low but not 0, PWM cycle 1 and PWM cycle 6 in FIG.
It always lights up at the start position. Therefore, when performing backlight scanning, PWM
When the signal starts from the lighting period, the sensor value acquisition timing of each area is the start position of the blinking cycle of each area. Area 1 is the start position of PWM cycle 1 and PWM cycle 6, and area 3 is the start position of PWM cycle 2 and PWM cycle 7.

The duty ratio when viewed in terms of the blinking cycle is hereinafter referred to as “flashing duty ratio” and is distinguished from the duty ratio for each PWM cycle. Here, an example in which the sensor value of the LED block in area 1 is acquired at the start position of PWM cycle 6 will be described. In this case, as shown in FIG. 10 (B), the forced extinction period is set in the lighting period of PWM cycle 5 and PWM period 6 of areas 7 to 10 in which the lighting start timing is in the period of image frame 1. More specifically, in the sensor value acquisition period of area 1, the forced extinction period is set to the PWM lighting period in the PWM period 6 of areas 7 and 9 and the PWM period 5 of areas 8 and 10. Further, as shown in FIG. 10C, the forced extinction period is set in the lighting period of the PWM cycle 6 in area 1 (non-sensor value acquisition area) where the lighting start timing is in the period of the image frame 2.

In the first embodiment, the method of compensating for the luminance decrease due to the forced turn-off by the method of extending the lighting period of the PWM cycle in which the forced turn-off period is set in advance has been described. In other words, brightness compensation was performed by extending the lighting period within the PWM cycle in which the forced extinguishing period was set. If this brightness compensation method is applied to the example in FIG. 10, the duty cycle is set to 50% in PWM cycle 6 of area 7, so the PWM lighting period can be extended within the same cycle. is there.

On the other hand, the duty ratio is set to 100% for the PWM cycle 5 in the areas 8 and 10 and the PWM cycle 6 in the area 9. Therefore, the lighting period cannot be further extended in the same period. Therefore, in this embodiment, when the original duty ratio of the PWM cycle in which the forced turn-off period is set to the PWM turn-on period is 100%, the turn-on period before or after the PWM cycle can be extended. The lighting period is extended in the PWM cycle.

Here, since one cycle of the PWM signal by the LED driver 106 starts from the lighting period and ends with the extinguishing period, the duty ratio is 0% or more in the PWM period after the PWM period in which the forced extinguishing period is set in the PWM lighting period. A PWM period of less than% appears. Therefore, the PWM lighting period is extended in a period after the PWM period in which the forced extinction period is set. Note that if the initial duty ratio of the PWM cycle with a duty cycle of 0% or more and less than 100% in the PWM cycle after the PWM cycle for which the forced turn-off period is set in the lighting period is 0%, the lighting period is extended. In this PWM cycle, a lighting period is provided.

In area 8, the PWM cycle 5 has a duty ratio of 100%, and the next PWM cycle 6 has a duty ratio of 50%. Therefore, in this PWM cycle 6, the PWM lighting period is extended. The instruction to extend the lighting period of the PWM cycle 6 in the area 8 is made by communication 6 from the backlight control unit 105 to the LED driver 106.

In area 9, the PWM cycle 6 in which the forced extinction period is set during the lighting period has an original duty ratio of 100%, and the next PWM period 7 has a duty ratio of 50%. Therefore, the backlight control unit 105 performs a setting to extend the PWM lighting period in the PWM cycle 7 by the communication 7.

In area 10, the original duty ratio is 100% in the PWM cycle 5 in which the forced extinction period is set during the lighting period, and the original duty ratio is 100% also in the next PWM cycle 6. In the next PWM cycle 7, the original duty ratio is 50%.
Thus, the PWM lighting period is set to be extended in the PWM cycle 7.

In the non-sensor value acquisition LED block in area 1, the original duty ratio is 100% in the PWM period 6 in which the forced extinction period is set during the lighting period and the subsequent PWM period 7. Therefore, the backlight control unit 105 performs a setting for extending the PWM lighting period in the next PWM cycle 8 through the communication 8.

FIG. 11 shows a timing chart of PWM control after extending the lighting period. Figure 10,
In the example in Fig. 11, the blinking duty ratio of the backlight scan (per image frame) is 50%, so the PWM period for extending the lighting period is a maximum of two periods from the PWM period for which the forced extinction period is set. It was later. However, when the duty ratio of blinking is higher, the PWM cycle for extending the lighting period may be three cycles or four cycles after the PWM cycle in which the forced extinction period is set.

Next, an example in which backlight scanning is performed when the PWM signal from the LED driver 106 has a specification starting from the extinguishing period and ending in the lighting period will be described with reference to FIG. For example, in area 1, in PWM cycle 1 and PWM cycle 2, the duty ratio of the PWM signal is set to 0% (off). In the next PWM cycle 3, the duty ratio of the PWM signal is set to 50%. PWM in next PWM cycle 4 and PWM cycle 5
Set the signal duty ratio to 100%. As a result, the image frame 1 can be blinked so as to switch from unlit to lit only once, that is, blinking at 60 Hz.

Similarly, in the next image frame 2 (PWM cycle 6 to 10), if the duty ratio of the PWM signal is set, the lighting and lighting at 60 Hz are repeated. By controlling the other areas while changing the duty ratio for each PWM cycle, it is possible to perform light emission control for blinking the backlight at the same frequency as the frequency of the image signal as shown in FIG. Next, a method for suppressing the luminance variation of the backlight accompanying the sensor value acquisition in this case will be described.

The sensor value needs to be acquired at a timing at which the sensor value is always turned on even if the backlight scanning blinking duty ratio is low. Even if the duty ratio of blinking is low, if it is not 0, for example, area 1 is always lit at the end position of PWM cycle 5 in FIG. Therefore, when performing a backlight scan and the PWM signal is a signal starting from the extinguishing period, the sensor value acquisition timing of each area is the end position of the blinking cycle of each area. In the case of area 1, it is the end position of PWM cycle 5, and in the case of area 3, it is the end position of PWM cycle 6.

Here, the case where the sensor value of the LED block in area 7 is acquired will be described as an example. FIG.
(A) shows an example of a time chart of PWM control when the sensor value of the LED block in area 7 is acquired. FIG. 13 (B) shows an enlarged view of areas 7 to 10, and FIG. 13 (C) shows an enlarged view of area 1.

In area 7 (non-sensor value acquisition LED block), the original duty ratio of PWM cycle 8, which is the PWM cycle in which the forced extinction period is set with sensor value acquisition, is 100%. Extend the lighting period. If the PWM signal starts from the light-off period and ends with the light-up period, the PWM cycle is earlier than the PWM period in which the forced light-off period is set by sensor value acquisition, and the original duty ratio is less than 100%. The period for turning on the PWM of the cycle is extended. Note that if the initial duty ratio of 0% is the PWM period before the PWM period in which the forced extinction period is set in the lighting period and the original duty ratio is less than 100%, the lighting period For the extension, a lighting period is provided in the PWM cycle. In the case of area 7 (non-sensor value acquisition LED block), the PWM cycle 8 in which the forced extinction period is set as described above and the previous PWM cycle 7 have the original duty ratio of 100%, and the PWM before that The duty ratio of period 6 is 50%. Therefore,
In this PWM cycle 6, the PWM lighting period is extended.

  In area 8, the PWM cycle 8 in which the forced extinction period is set in accordance with the sensor value acquisition and the previous PWM cycle 7 have a duty ratio of 100%, and the previous PWM cycle 6 has a duty ratio of 50%. Therefore, the PWM lighting period is extended in PWM cycle 6.

In both area 9 and area 10, the PWM cycle is set for the forced extinction period when sensor values are acquired.
Since the duty ratio is 100% and the duty ratio of the previous PWM cycle 7 is 50%, the PWM lighting period is extended in the PWM cycle 7.

In area 1, since the original duty ratio is 50% in the PWM cycle 8 in which the forced extinction period is set as the sensor value is acquired, the PWM lighting period is extended in the PWM cycle 8.

  FIG. 14 shows a timing chart of PWM control after extending the lighting period.

  By performing brightness compensation as described above, when performing backlight scan PWM control that causes the backlight to blink at a blinking frequency that is different from the drive frequency, it suppresses backlight brightness fluctuations associated with LED block sensor value acquisition. be able to.

(Example 3)
In the first and second embodiments, the target for extending the PWM lighting period is one PWM cycle. In this embodiment, an example in which the PWM lighting period is extended for a plurality of PWM cycles will be described. Here, with reference to FIG. 15, a case where the backlight scan is performed with the specification that the PWM signal starts from the extinguishing period and ends in the lighting period will be described as an example. As shown in FIG. 15A, it is assumed that the blinking duty ratio is about 38%.

For example, in area 1, the PWM signal duty ratio is set to 0% in PWM periods 1 to 3, the PWM signal duty ratio is set to 95% in PWM period 4, and the PWM signal duty ratio is set to PWM period 5. Set to 100%. This achieves a blinking duty ratio of 38%. Similarly, in other areas, it is assumed that the duty ratio of five PWM periods is set to 100%, one is set to 95%, and the other three are set to 0%.

The length of the sensor value acquisition period is assumed to be equivalent to 10% (about 0.33 ms) in terms of the duty ratio of the PWM signal. However, this is only an example, and the sensor 108 is long enough to measure the brightness of the LED block, and when the non-sensor value acquisition LED block is turned off for a length corresponding to the sensor value acquisition period, the light is turned off. This is not limited as long as the length is not visible to the observer. As in the case of FIG. 13, the sensor value acquisition timing of each area is the end position of the blinking cycle of each area.

  For example, a case where sensor values of LED blocks in area 7 are acquired will be described. In this case, the forced turn-off period is set to the PWM turn-on period of area 7 (non-sensor value acquisition LED block) and areas 8 to 10. An enlarged view is shown in FIG.

In area 7 (non-sensor value acquisition LED block), the original duty ratio of PWM cycle 8, which is the PWM cycle in which the forced extinction period is set with sensor value acquisition, is 100%. Extends the PWM lighting period. In the previous PWM cycle 7, the original duty ratio is 95%
It is. Therefore, in this PWM cycle 7, it is possible to extend the PWM lighting period, but only 5% can be extended, so the extension corresponding to the duty ratio of 10% necessary for luminance compensation should be performed only in PWM cycle 7. I can't. Therefore, in this PWM cycle 7, the duty ratio is increased by 5% and the duty ratio is changed to 100%. Further, by changing the duty ratio from 0% to 5% in the previous PWM cycle 6, the remaining 5% necessary for 10% luminance compensation is secured.

In area 8, the PWM lighting period is extended by 5% at each of PWM cycles 7 and 6, and in areas 9 and 10, the PWM lighting period is extended by 5% at each of PWM periods 8 and 7. This compensates for a decrease in luminance due to the setting of a forced extinction period corresponding to a duty ratio of 10%.
FIG. 16 shows a timing chart of the PWM control after expansion.

Next, an application example will be described in which lighting control is performed in which the frequency of the PWM signal is the same as the blinking frequency of the LED block, instead of performing the backlight scan as in the above example.

In the following description, it is assumed that the sensor value acquisition period is 10% (about 0.33 ms) in terms of PWM duty ratio. In this case, if the duty ratio of the original PWM signal exceeds 90%, as described in the first embodiment, the luminance decreases for the forced extinction period in the PWM cycle in which the compulsory extinction period is set as the sensor value is acquired. It is not possible to extend the lighting period to compensate for all of the above.

  Here, as an example, as shown in FIG. 17A, it is assumed that the duty ratio of the original PWM signal set to obtain the target luminance is 94%. Then, as shown in FIG. 17 (B), the sensor value of the LED block in area 1 is acquired at the start timing of the lighting period of PWM cycle 3. At this time, a forced turn-off period equivalent to a duty ratio of 10% is set for the lighting period of PWM cycle 2 in areas 2 to 10 and the lighting period of PWM cycle 3 in area 1 (non-sensor value acquisition LED block). become.

On the other hand, as described in the first embodiment, even if an attempt is made to extend the lighting period to compensate for the luminance decrease for the forced light-off period in the PWM cycle in which the forced light-off period is set, the original duty ratio is Since it is 94%, the duty ratio cannot be extended by 10%. Therefore, in such a case, as shown in FIG. 17C, the PWM lighting period is extended for luminance compensation divided into a plurality of PWM periods.

For areas 2 to 10, the backlight control unit 105 extends the lighting period by 5% for the LED driver 106 in the PWM cycle 2 in which the forced light-off period is set, and sets the duty ratio to 99%.
Instructed by communication 2 to set to. In addition, in PWM cycle 1 immediately before PWM cycle 2, the remaining 5% of the lighting period required for luminance compensation equivalent to 10% is extended to set the duty ratio to 99%. Instruct by.

For area 1 (non-sensor value acquisition LED block), the backlight control unit 105 extends the lighting period for 5% in the PWM cycle 3 in which the forced extinction period is set by communication 3 for the LED driver 106. To set the duty ratio to 99%. Also, in PWM cycle 2 immediately before PWM cycle 3, communication 2 is set so that the duty ratio is set to 99% by extending the remaining 5% of the lighting period required for luminance compensation equivalent to 10%. Instruct by.

  The area 1 (non-sensor value acquisition LED block) is returned to the original duty ratio in the PWM cycle 4, and the areas 2 to 10 are returned to the original duty ratio in the PWM cycle 3.

By extending the lighting period as described above, it is possible to compensate for the luminance reduction of the backlight caused by forcibly turning off the other LED blocks with the acquisition of the sensor value of the LED block.

Here, an example in which the lighting period is extended by 5% equally in each PWM period divided into two PWM periods has been described, but it is not always necessary to make the extension amount of the PWM lighting period in each PWM period the same. . It is also possible to perform expansion in two or more PWM cycles. In other words, the lighting period may be extended in one or more cycles before or after the forced turn-off cycle. However, depending on the relationship between the number of PWM periods in which the lighting period is extended in a divided manner and the interval at which sensor values are acquired, it is conceivable that it is not possible to compensate for all the luminance reductions.

For example, if sensor values are acquired once every image frame (60Hz), if the frequency of the PWM signal is 300Hz, lighting is performed to divide it into 5 or fewer PWM periods to compensate for brightness reduction The period can be extended. A configuration may be adopted in which the sensor value acquisition cycle is determined in accordance with the duty ratio. Even if LEDs are driven with the same amount of current and the same duty ratio, the luminance tends to decrease due to deterioration over time. In such a case, it is common to obtain the target brightness by increasing the duty ratio of the PWM signal. Therefore, the duty ratio of the PWM signal may be increased depending on the degree of LED degradation. According to the present embodiment, even when the original duty ratio of the PWM signal is high, it is possible to suppress the luminance variation of the backlight due to the forced extinction accompanying the sensor value acquisition.

105 Backlight controller
107 backlight
109 Sensor control unit

Claims (16)

A plurality of light sources that can control light emission independently;
Control means for controlling the luminance of the light source by pulse width modulation control for adjusting the duty ratio between the lighting period and the extinguishing period within a predetermined period;
Measuring means for measuring the luminance of the light source to be measured by receiving light from the light source to be measured over a predetermined measurement period;
With
When the measuring means measures the luminance of the light source to be measured by the measuring means, among the light sources that are not the measuring object, the measuring period by the measuring means exists during the lighting period initially determined by the pulse width modulation control. The light source is forcibly turned off during the measurement period, and the light source is forcibly turned on at least one of a period for which the light is forcibly turned off, or a period before and after the period for which the light source is forcibly extinguished. An illuminating device that extends a lighting period of the light source that is initially determined by pulse width modulation control so as to compensate for a decrease in luminance due to turning off. The control means controls the luminance of the light source by pulse width modulation control in which each cycle starts from the lighting period and ends in the extinguishing period,
The lighting device according to claim 1, wherein the lighting period for compensating for the decrease in luminance is extended by extending a lighting period initially determined backward. The control means controls the luminance of the light source by pulse width modulation control in which each cycle starts from the extinguishing period and ends in the lighting period,
The lighting device according to claim 1, wherein the lighting period for compensating for the decrease in luminance is extended by extending a lighting period initially determined in a forward direction. The control means performs the extension of the lighting period in the period for forced extinguishing, and if the decrease in luminance cannot be compensated only by the extension of the lighting period in the period for forced extinguishing, further before or after the period for forced extinguishing The lighting device according to claim 1, wherein the lighting period is extended in one or more cycles. The control means controls the luminance of the light source by pulse width modulation control in which each cycle starts from the lighting period and ends in the extinguishing period, and the duty ratio can be changed for each period of the pulse width modulation control. Is a frequency of pulse width modulation control by driving the light source in units of a plurality of periods consisting of at least one of a period of 100% and a period of 0% of the duty ratio and one period of which the duty ratio is 100% or less. Control to blink the light source at a lower frequency,
The extension of the lighting period to compensate for the brightness reduction is a period for forced extinction among the plurality of periods including the period for forced extinction, or a period after that and a duty ratio initially determined is less than 100% The lighting device according to claim 1, wherein the lighting period is extended backwards. The control means controls the luminance of the light source by pulse width modulation control, each period starting from the extinguishing period and ending in the lighting period, and the duty ratio can be changed for each period of the pulse width modulation control. The frequency of pulse width modulation control by driving the light source in units of multiple periods consisting of at least one of the period of 0% and the period of 100% of the duty ratio and one period of the duty ratio of 100% or less Control to blink the light source at a lower frequency,
The duty cycle initially defined in the plurality of cycles including the cycle for forced extinction or the cycle before the extinction of the lighting period to compensate for the decrease in luminance is less than 100%. The lighting device according to claim 1, wherein the lighting device is performed by extending a lighting period of a predetermined period forward.   When the control means cannot compensate for the luminance drop only by extending the lighting period of the cycle with the initially determined duty ratio of less than 100%, the initially set duty ratio before or after the cycle is further set to 0. The lighting device according to claim 5, wherein the lighting period is extended to a period of%. A backlight device of an image display device including the illumination device according to claim 1,
The backlight device, wherein the plurality of light sources are a plurality of light emitting blocks arranged in a horizontal direction and a vertical direction of a screen of the image display device. A plurality of light sources that can control light emission independently;
Measuring means for measuring the luminance of the light source to be measured by receiving light from the light source to be measured over a predetermined measurement period;
A method for controlling a lighting device comprising:
A control step of controlling the luminance of the light source by pulse width modulation control for adjusting the duty ratio of the lighting period and the extinguishing period within a predetermined period;
When measuring the luminance of the light source to be measured by the measurement means, among the light sources that are not the measurement target, the light source having the measurement period by the measurement means during the lighting period initially determined by the pulse width modulation control is measured. In at least one of the period in which the light source is forcibly turned off in the period and the period for which the light source is forcibly turned off, or the period before and after that, and the lighting period initially determined by the pulse width modulation control can be extended, And a step of extending the lighting period of the light source initially determined by pulse width modulation control so as to compensate. The control step is to control the luminance of the light source by pulse width modulation control in which each cycle starts from the lighting period and ends in the extinguishing period,
The lighting device control method according to claim 9, wherein the lighting period for compensating for the decrease in luminance is extended by extending a lighting period initially determined backward. The control step is to control the luminance of the light source by pulse width modulation control in which each cycle starts from the extinguishing period and ends in the lighting period,
The lighting device control method according to claim 9, wherein the lighting period for compensating for the reduction in luminance is extended by extending a lighting period initially determined in a forward direction. The control step performs an extension of the lighting period in the period for forced extinguishing, and if the decrease in luminance cannot be compensated only by the extension of the lighting period in the period for forced extinguishing, further before or after the period for forced extinguishing The lighting device control method according to claim 9, wherein the lighting period is extended in one or more cycles. The control step is to control the luminance of the light source by pulse width modulation control in which each cycle starts from the lighting period and ends in the extinguishing period, and the duty ratio can be changed for each period of the pulse width modulation control. Is a frequency of pulse width modulation control by driving the light source in units of a plurality of periods consisting of at least one of a period of 100% and a period of 0% of the duty ratio and one period of which the duty ratio is 100% or less. Control to blink the light source at a lower frequency,
The extension of the lighting period to compensate for the brightness reduction is a period for forced extinction among the plurality of periods including the period for forced extinction, or a period after that and a duty ratio initially determined is less than 100% The lighting device control method according to claim 9, wherein the lighting device is performed by extending a lighting period of a predetermined period backward. The control step is to control the luminance of the light source by pulse width modulation control in which each cycle starts from the extinguishing period and ends in the lighting period, and the duty ratio can be changed for each period of the pulse width modulation control. The frequency of pulse width modulation control by driving the light source in units of multiple periods consisting of at least one of the period of 0% and the period of 100% of the duty ratio and one period of the duty ratio of 100% or less Control to blink the light source at a lower frequency,
The duty cycle initially defined in the plurality of cycles including the cycle for forced extinction or the cycle before the extinction of the lighting period to compensate for the decrease in luminance is less than 100%. The lighting device control method according to claim 9, wherein the lighting device is performed by extending a lighting period of a predetermined period forward.   In the control step, when it is not possible to compensate for a decrease in luminance only by extending the lighting period in a cycle in which the initially determined duty ratio is less than 100%, the initially determined duty ratio before or after the cycle is further set to 0. The lighting device control method according to claim 13 or 14, wherein the lighting period is extended to a period of%.   A backlight device of an image display device including the illumination device, wherein the plurality of light sources are a plurality of light emitting blocks arranged in a horizontal direction and a vertical direction of a screen of the image display device. And the control method of the backlight apparatus containing each process of any one of Claims 9-15.

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