JP2015079732A - Light source device, control method for light source device, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology which can reliably and highly accurately reduce a change in light emission characteristic of a light source.SOLUTION: A light source device has: a light source which cyclically emits light; light detection means for detecting light emitted by the light source; determination means for determining target luminance of the light source; and adjustment means which adjusts drive duty ratio to be ratio of a total lighting time of the light source in one cycle with respect to one cycle of light emission of the light source on the basis of the target luminance determined by the determination means and the light detection value of the light detection means. The adjustment means adjusts the drive duty ratio by using the light detection value obtained after a prescribed time has passed since the light source starts lighting when the one lighting time of the light source is a prescribed time or longer, and adjusts the drive duty ratio by using the light detection value used when drive duty ratio has been adjusted in the past when one lighting time of the light source is shorter than the prescribed time.

Description

  The present invention relates to a light source device, a control method for the light source device, and a program.

  In recent years, liquid crystal display devices have become mainstream as image display devices. Since the liquid crystal panel is not a self-luminous device, a backlight using a light source such as an LED (Light Emitting Diode) 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 (Pulse Width Modulation) control (pulse width modulation control) is often used as means for adjusting the luminance 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 lighting period and the extinguishing 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. Therefore, it is common to perform PWM control of the backlight at a high frequency of 200 Hz or higher. As a result, for example, if the frame frequency of the image is 60 Hz, the backlight is repeatedly turned on and off several times during one frame of the image.

  Many LEDs are laid on a backlight using LEDs. The number of LEDs varies depending on the size of the display screen, required luminance, and the like. Here, as shown in FIG. 17, the backlight is divided into 10 areas each composed of one or a plurality of LEDs, and the light emission of the LEDs in each area can be controlled independently, and the phase of the PWM signal is different for each area. It shall be possible to 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. The horizontal axis in FIG. 18 is time, and the vertical axis is 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 a significant fluctuation in the total current.

Further, the light emission characteristics of a light source such as an LED change due to its aging and temperature change. Therefore, the light emission luminance and color of the light source change due to aging and temperature changes. 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. Further, the brightness varies from LED to LED due to a temperature difference in the screen or deterioration due to aging. Further, 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, the brightness variation of each LED block is accurately grasped, and then the luminance unevenness of the backlight is suppressed by changing the duty ratio of the PWM signal for each LED block. Is effective.

  Conventionally, as a technique related to a liquid crystal display or an illuminating device using an LED as a light source, a technique for reducing a change in light emission characteristics due to a secular change or a temperature change has been proposed (Patent Documents 2 and 3). In the technique described in Patent Document 2, light emitted from an LED included in the backlight is detected by an optical sensor provided in the backlight. And the change of the light emission characteristic of LED is suppressed by controlling the electric current amount supplied to LED according to the detected value of an optical sensor. In the technique described in Patent Document 3, a value obtained by smoothing a detection value of an optical sensor provided in the illumination device is not used, but a peak value of the detection value is used.

  As described above, as a method of suppressing the luminance unevenness of the backlight, there is a method of performing control such as obtaining the luminance variation of the LED block using the luminance sensor and changing the duty ratio for each LED block based on the obtained result. is there. Here, in order to accurately acquire the luminance sensor value for each LED block, only the LED block (acquisition target LED block) that is the sensor value acquisition target is turned on, and the other LED blocks (non-acquisition target blocks) are turned off It is effective to suppress the influence on the measurement value due to light leakage. However, as described above, when the emission control is performed by changing the phase of the PWM signal for each area of the backlight, the LED block in any area of the backlight is always lit unless the duty ratio is extremely low. ing. Even if the duty ratio is extremely low, lighting is started simultaneously between LED blocks having the same lighting phase.

  Therefore, there is almost no opportunity to be in a lighting state in which all LED blocks other than the acquisition target LED block are turned off. When the display is not used, it is also possible to measure by turning on only the acquisition target LED block 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 (non-acquisition target blocks) other than the acquisition target LED block are extinguished in the predetermined sensor value acquisition period, and the sensor value of the acquisition target LED block 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 the acquisition target LED block. As shown in FIG. 20, in the sensor value acquisition period, only the acquisition target LED block in area 1 is lit, and other LED blocks in area 1 (non-acquisition target LED blocks) 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.

However, as described above, when the LEDs other than the acquisition target LED block are extinguished for a moment, the extinguishing itself is momentary, so that it is difficult for human eyes to visually recognize. However, the luminance is slightly reduced by the amount of light that is turned off. 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 the LED blocks other than the acquisition target LED block in area 1 accompanying sensor value acquisition of the acquisition target LED block. The brightness of area 1 decreases. Further, in areas 7, 8, 9, and 10, the lighting period in which lighting is started in the previous PWM cycle is shortened, so that 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, in the forced extinction by the sensor value acquisition, there are areas where the luminance is reduced and areas where the luminance does not occur. At this time, whether or not the luminance is lowered 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 an LED block in which the luminance is not reduced if the setting of the duty ratio is different for each LED block. Further, even when all the blocks have the same duty ratio, when sensor values are acquired in areas with different phases, luminance drop in different areas occurs. FIG. 21 shows a diagram in the case where the sensor value of one block in area 4 is acquired. In this case, a luminance drop occurs in the non-acquisition target LED blocks in areas 1, 2, 3 and area 4, and area 10 of the previous PWM cycle, and no luminance drop occurs in other areas. As described above, there are cases where the luminance drop occurs and does not occur due to various factors such as the phase and duty ratio of the area from which the sensor value is acquired. Therefore, when sensor values are continuously acquired while changing the block from which the sensor value is acquired, there are a period in which the luminance is reduced and a period in which the luminance is not reduced for each block. Such a change in luminance for each period is visually recognized as flicker.

  There are the following methods for preventing this. That is, by calculating in advance the lighting start phase and the duty ratio the blocks where the brightness drop occurs due to turning off for sensor value acquisition, and changing the duty ratio setting of the block where the brightness drop occurs There is a method for preventing a decrease in luminance.

  For example, as shown in FIG. 22, when the sensor value acquisition of the LED block in area 4 is performed in PWM cycle 2, the PWM duty ratio in area 10 is increased in PWM cycle 1. Further, in the PWM cycle 2, the PWM duty ratios of the non-acquisition target LED blocks in areas 1 to 3 and area 4 are increased. Thereby, the brightness | luminance fluctuation | variation of a backlight can be suppressed. Thus, by calculating from the acquisition target LED block, the lighting start phase, and the original duty ratio, and setting the duty ratio high in advance, it is possible to suppress luminance fluctuation and prevent flicker. By performing the control as described above, it is possible to provide a backlight that prevents flicker and suppresses uneven brightness.

  Next, the operation of the backlight during sensor acquisition will be described in detail with reference to FIG. FIG. 23 is a timing chart showing the operation of the backlight during sensor acquisition. The backlight control unit turns off all the LEDs other than the sensor acquisition block in accordance with the timing at which the PWM cycle of the sensor acquisition block starts. Then, the backlight control unit asserts a sensor value obtainable signal simultaneously with completion of the extinction control. The sensor control unit starts acquisition of the sensor value in response to the assertion of the sensor value acquisition possible signal. While this sensor acquisition possible signal is asserted, the LEDs other than the acquisition target LED block are turned off. Therefore, if the sensor value acquisition is completed during this period, it is not affected by the light of other LED blocks. One block of sensor values can be acquired. When the predetermined time elapses, the backlight control unit negates the sensor value obtainable signal and simultaneously relights the LED of the block that has been turned off. By performing the operation as described above, it is possible to accurately grasp the luminance of only one LED block. By performing this operation for all the blocks in order, it is possible to acquire the brightness of the LEDs of all the blocks in the screen.

By the way, in the liquid crystal display, when displaying black, the light of the backlight is shielded by closing the liquid crystal shutter. However, the liquid crystal shutter cannot be sufficiently shielded from light, and even if the liquid crystal shutter is closed, a slight leak of light causes a so-called “black float” in which sufficient black cannot be expressed. Therefore, when the control is performed so that the luminance of the backlight is uniform over the entire screen, the contrast ratio in the screen is limited due to black floating.

  Here, as a technique related to the liquid crystal display, there is a technique for individually controlling the light emission luminance (light emission amount) of each light source (LED block) included in the backlight. For example, there is a technique for individually controlling the light emission luminance of each light source based on input image data (image data displayed on a liquid crystal display). Specifically, there is a technique for individually controlling the light emission luminance of each light source so that the light emission luminance of the light source is lower in the screen region where dark image data is displayed than in the screen region where bright image data is displayed. is there. Such control is called “local dimming control”. A conventional technique related to local dimming control is disclosed in Patent Document 4, for example. By performing the local dimming control, it is possible to reduce the black float of the display image (image displayed on the screen) and increase the contrast of the display image.

JP 2010-153359 A JP 2008-210878 A JP 2010-205530 A JP 2001-142409 A

  As described above, the light emission luminance of the light source is generally controlled by PWM control. For example, by reducing the width of the pulse signal (pulse width), the lighting time of the light source is shortened, and the light emission luminance of the light source is reduced.

  However, when local dimming control is performed, a location with high luminance (high duty ratio) and a location with low luminance (low duty ratio) appear locally depending on the input image. When the lighting period of the light source with a low duty ratio is shorter than the predetermined time (time for acquiring the detection value of the optical sensor), not only the sensor value when the light source is lit but also the light source is turned off. Incorrect feedback control is performed using the sensor value when the sensor is in the middle. As a result, luminance unevenness in the screen increases with high probability.

  Further, the waveform of the detection value (light detection value) of the optical sensor does not rise steeply like a rectangular wave, but has a rise delay (waveform rounding). Therefore, when the lighting time of the light source is shortened by local dimming control or the like, a completely stable value cannot be obtained as the light detection value, and the light detection accuracy of the light sensor is lowered. As a result, the change in the light emission characteristics of the light source cannot be reduced with high accuracy.

Patent Documents 2 and 3 do not particularly describe a control method in the case where the lighting time of the light source is shortened by local dimming control or the like. It will occur.
Moreover, in the technique described in Patent Document 3, a light detection value when the light amount of the combined light obtained by combining the light emitted from all the light sources becomes maximum is used. For this reason, the technique described in Patent Document 3 cannot reduce the change in the light emission characteristics of the light source with high accuracy when performing local dimming control. For example, in the technique described in Patent Document 3, the light detection value changes not only by changing the light emission characteristics of the light source but also by individually controlling the light emission luminance of each light source. Therefore, with the technique disclosed in Patent Document 3, it cannot be determined why the light detection value has changed, and the change in the light emission characteristics of the light source cannot be reduced with high accuracy.

  An object of this invention is to provide the technique which can reduce the change of the light emission characteristic of a light source reliably and with high precision.

The first aspect of the present invention is:
A light source that emits light periodically;
Light detection means for detecting light emitted from the light source;
Determining means for determining a target luminance of the light source;
Based on the target luminance determined by the determining means and the light detection value of the light detecting means, a drive duty ratio that is a ratio of the total lighting time of the light source within one period to one period of light emission of the light source Adjusting means for adjusting
Have
The adjusting means includes
When the lighting time of one time of the light source is equal to or longer than a predetermined time, the drive duty ratio is adjusted using a light detection value obtained after the predetermined time has elapsed since the light source started lighting. ,
The drive duty ratio is adjusted using a light detection value used when the drive duty ratio has been adjusted in the past when the lighting time of the light source once is shorter than the predetermined time. It is a light source device.

The second aspect of the present invention is:
A light source that emits light periodically;
Light detection means for detecting light emitted from the light source;
Determining means for determining a target luminance of the light source;
Based on the target luminance determined by the determining means and the light detection value of the light detecting means, a drive duty ratio that is a ratio of the total lighting time of the light source within one period to one period of light emission of the light source Adjusting means for adjusting
Have
The adjusting means includes
When the lighting time of one time of the light source is equal to or longer than a predetermined time, using the light detection value obtained in the acquisition period that is a period from when the light source starts lighting until the predetermined time elapses, Adjusting the drive duty ratio;
When the lighting time of the light source once is shorter than the predetermined time, the drive duty ratio is adjusted without using the light detection value obtained in the acquisition period after the light source is turned off. It is the light source device characterized by doing.

The third aspect of the present invention is:
A light source that emits light periodically;
Light detection means for detecting light emitted from the light source;
A method of controlling a light source device comprising:
A determining step for determining a target brightness of the light source;
Based on the target luminance determined in the determining step and the light detection value of the light detection means, a drive duty ratio that is a ratio of the total lighting time of the light source within one cycle to one cycle of light emission of the light source Adjustment steps to adjust,
Have
In the adjustment step,
When the lighting time of one time of the light source is equal to or longer than a predetermined time, the drive duty ratio is adjusted using a light detection value obtained after the predetermined time has elapsed since the light source started lighting. ,
The drive duty ratio is adjusted using a light detection value used when the drive duty ratio has been adjusted in the past when the lighting time of the light source once is shorter than the predetermined time. It is the control method of a light source device.

The fourth aspect of the present invention is:
A light source that emits light periodically;
Light detection means for detecting light emitted from the light source;
A method of controlling a light source device comprising:
A determining step for determining a target brightness of the light source;
Based on the target luminance determined in the determining step and the light detection value of the light detection means, a drive duty ratio that is a ratio of the total lighting time of the light source within one cycle to one cycle of light emission of the light source Adjustment steps to adjust,
Have
In the adjustment step,
When the lighting time of one time of the light source is equal to or longer than a predetermined time, using the light detection value obtained in the acquisition period that is a period from when the light source starts lighting until the predetermined time elapses, Adjusting the drive duty ratio;
When the lighting time of the light source once is shorter than the predetermined time, the drive duty ratio is adjusted without using the light detection value obtained in the acquisition period after the light source is turned off. It is the control method of the light source device characterized by doing.

  According to a fifth aspect of the present invention, there is provided a program that causes a computer to execute each step of the above-described light source device control method.

  According to the present invention, the change in the light emission characteristics of the light source can be reliably and accurately reduced.

1 is a block diagram illustrating an example of a configuration of a display device according to a first embodiment. The figure which shows an example of a structure of the light source part which concerns on Example 1. FIG. The figure which shows an example of the output value of the photosensor which concerns on Example 1. FIG. FIG. 3 is a flowchart showing an example of a flow of local dimming control according to the first embodiment. FIG. 6 is a flowchart showing an example of a flow of light emission characteristic change correction processing according to the first embodiment. FIG. 6 is a block diagram illustrating an example of a configuration of a display device according to a second embodiment. FIG. 9 is a flowchart illustrating an example of a flow of light emission characteristic change correction processing according to the second embodiment. FIG. 6 is a block diagram illustrating an outline of an image display apparatus according to a third embodiment. The figure which shows an example of the conventional sensor value acquisition process The figure which shows an example of the sensor value acquisition process which concerns on a present Example. FIG. 9 is a flowchart illustrating an example of the operation of the sensor control unit according to the third embodiment. The figure which shows an example of the conventional sensor value acquisition process The figure which shows an example of the conventional sensor value acquisition process The figure which shows an example of the sensor value acquisition process which concerns on Example 4. FIG. The figure which shows an example of the sensor value acquisition process which concerns on Example 4. FIG. The figure which shows an example of the sensor value acquisition process which concerns on Example 5. FIG. Diagram showing backlight area division Diagram showing PWM control in the prior art Diagram showing PWM control in the prior art The figure which shows the PWM control at the time of sensor value acquisition in a prior art The figure which shows the PWM control at the time of sensor value acquisition in a prior art The figure which shows brightness compensation at the time of sensor value acquisition in the prior art The figure which shows an example of the conventional sensor value acquisition process

<Example 1>
A light source device and a control method thereof according to Embodiment 1 of the present invention will be described.
In the following, an example in which the light source device according to the present embodiment is used in a display device that displays an image on a screen by modulating light emitted from the light source device will be described. The light source device according to the embodiment is not limited to this. The light source device according to the present embodiment may be, for example, a lighting device such as a street lamp or indoor lighting.
In the following, an example in which the display device according to the present embodiment is a transmissive liquid crystal display device will be described, but the display device according to the present embodiment is not limited thereto. The display device according to the present embodiment may be a display device that displays an image on a screen by modulating light emitted from the light source device. For example, the display device according to the present embodiment may be a reflective liquid crystal display device. In addition, the display device according to the present embodiment may be a MEMS shutter type display using a MEMS (Micro Electro Mechanical System) shutter instead of the liquid crystal element.

  FIG. 1 is a block diagram illustrating an example of the configuration of the display device according to the present embodiment. As shown in FIG. 1, the display device according to the present embodiment includes an image input unit 101, a display unit 102, a storage unit 103, a light source unit 104, a light detection unit 105, a target luminance determination unit 106, a control unit 107, and a light source drive. Part 108, and the like.

  The image input unit 101 acquires image data from the outside, and outputs the acquired image data to the target luminance determination unit 106 and the display unit 102. The image input unit 101 is an image input terminal of a standard such as HDMI (High-Definition Multimedia Interface), DVI (Digital Visual Interface), and DisplayPort. The image input unit 101 is connected to an image output device such as a personal computer or a video player using a signal line. The image input unit 101 receives image data output from the image output device via a signal line, and outputs the received image data to the target luminance determination unit 106 and the display unit 102.

  The display unit 102 displays an image on the screen according to the image data output from the image input unit 101. For example, the display unit 102 is a liquid crystal panel having a plurality of liquid crystal elements, and is output from the image input unit 101. The transmittance of each liquid crystal element is controlled according to the image data. An image is displayed on the screen by modulating the light emitted from the light source unit 104. Then, light emitted from the light source unit 104 passes through each liquid crystal element, so that an image is displayed on the screen.

  The storage unit 103 is a rewritable storage medium such as a nonvolatile memory. In the storage unit 103, a detection response time, an ideal duty ratio table, and a reference light detection value are recorded in advance. Details of the detection response time, the ideal duty ratio table, and the reference light detection value will be described later. The storage unit 103 outputs the ideal duty ratio table, the detection response time, and the reference light detection value to the control unit 107.

The light source unit 104 is a planar light emitting body (backlight) having one or more light sources, and irradiates light (for example, white light) to the back surface of the display unit 102.
As shown in FIG. 2, in this embodiment, the area of the screen (the light emitting surface of the light source unit 104) is composed of four divided areas (areas 51 to 54) of 2 rows and 2 columns, 3 for each divided area. Two light sources (red LED 55, blue LED 56, and green LED 57) are provided. One light detection unit 105 is provided for each divided region. The light emission luminance (light emission amount) of each light source can be individually controlled. The red LED 55 is an LED that emits red light, the blue LED 56 is an LED that emits blue light, and the green LED 57 is an LED that emits green light. The light emitted from the red LED 55, the blue LED 56, and the green LED 57 is mixed, whereby white light is emitted from the light source unit 104.

In the present embodiment, an example in which the light source unit 104 includes a total of 12 light sources is described, but the present invention is not limited thereto. One light source (for example, a white LED that emits white light) may be provided for each divided region. That is, the number of light sources included in the light source unit 104 may be the same as the number of divided regions. Further, the number of light sources included in the light source unit 104 may be one.
In addition, although a present Example demonstrates the example in case the one photon detection part 105 is provided for every division area, it is not restricted to this. For example, one light detection unit 105 may be provided for each light source, or one light detection unit 105 may be provided for all light sources.
In addition, although a present Example demonstrates the example in case a light source is LED, it is not restricted to this. For example, the light source may be an organic EL element, a cold cathode tube, or the like.

In this embodiment, the light emission of the light source is controlled so as to emit light periodically. For example, one light emission period of the light source is a period of one frame of image data.
The light emission luminance of the light source can be controlled, for example, by controlling the pulse width of the pulse signal supplied to the light source. Each light source of the light source unit 104 is turned on when the pulse signal is High, and is turned off during the Low period. The emission luminance of the light source is controlled by controlling the duty ratio (drive duty ratio) of the pulse signal. The drive duty ratio is a ratio of the total lighting time of the light source (total time during which the pulse signal is High) within one cycle to one cycle of light emission of the light source (one cycle of the pulse signal). Therefore, when the drive duty ratio increases, the period during which the pulse signal is High increases, and the lighting time of the light source within one cycle also increases. As a result, the light emission luminance (light emission amount) of the light source is increased. On the other hand, when the drive duty ratio decreases, the period during which the pulse signal is high decreases, and the lighting time of the light source within one cycle also decreases. As a result, the light emission luminance (light emission amount) of the light source decreases.

Note that a plurality of lighting periods (periods in which the pulse signal is high) may be set in one cycle, or only one may be set.
In the present embodiment, an example in which the light emission luminance of the light source is controlled by controlling the drive duty ratio will be described, but the present invention is not limited to this. The light emission luminance of the light source can also be controlled by controlling the pulse amplitude of the pulse signal supplied to the light source. Therefore, the light emission luminance of the light source may be controlled by controlling both the drive duty ratio and the pulse amplitude.

The light detection unit 105 detects light emitted from the light source included in the light source unit 104 and outputs the detection result to the control unit 107. For example, the light detection unit 105 detects the light amount and the luminance. In this embodiment, for each divided region, light emitted from the light source provided in the divided region is detected using the light detection unit 105 provided in the divided region. The light detection unit 105 includes, for example, a photosensor that outputs an analog value indicating the amount of incident light, and an A / D converter that converts the analog value output from the photosensor into a digital value.
For example, the detection value (light detection value) of the light detection unit 105 in the area 51 when only the red LED 55 in the area 51 is lit is the detection result of the light emitted from the red LED 55 in the area 51 (red light detection value). ) Is output. In other words, the output value of the photosensor in area 51 when only the red LED 55 in area 51 is lit is sampled, and the sampled output value is converted into a digital value by the A / D converter in area 51. The obtained digital value is the detection result of the light emitted from the red LED 55 in the area 51 (
(Red light detection value).
Detection results are similarly obtained and output for other light sources. The detection result of the light emitted from the blue LED 56 is described as “blue light detection value”, and the detection result of the light emitted from the green LED 57 is described as “green light detection value”.

FIG. 3 is a diagram illustrating an example of the output value of the photosensor. In FIG. 3, the horizontal axis represents time, and the vertical axis represents the output value of the photosensor. FIG. 3 shows an example in which only the red LED provided in the same divided area as the photosensor emits light.
The red LED is driven by a pulse signal having one cycle from time T1 to time T5. From time T1 to time T4 is a lighting period, and from time T4 to time T5 is a light extinction period. The output value of the photosensor rises gradually from time T1 due to the rising characteristics of the pulse signal, the response characteristics of the photosensor, and the like, and stabilizes at time T2. The length of the period from time T 1 to time T 2, that is, the time required for the light detection value to stabilize is the detection response time recorded in the storage unit 103. The light detection unit 105 samples the output value of the photosensor during a period from time T2 to time T3 when the detection response time has elapsed.
The detection response time may or may not be a common time between the light sources and between the light detection units. For example, the detection response time when detecting light from a red LED, the detection response time when detecting light from a green LED, and the detection response time when detecting light from a blue LED are different from each other. May be.

The target brightness determination unit 106 determines the target brightness of each light source and outputs information indicating the target brightness of each light source to the control unit 107. In this embodiment, the target luminance of each light source is determined based on image data displayed on the display device (image data output from the image input unit 101). For example, the target brightness of each light source is determined so that the target brightness is lower in the dark area of the image data than in the bright area of the image data. Specifically, for each divided area, a feature amount indicating the brightness of the image data to be displayed in the divided area is acquired from the image data output from the image input unit 101. Then, for each divided region, the target luminance of the light source corresponding to the divided region is determined according to the feature amount of the divided region so that the target luminance becomes higher as the brightness indicated by the feature amount becomes brighter. The The target luminance is determined using information (table or function) indicating the correspondence between the feature amount and the target luminance, for example. By determining the target luminance in this way, it is possible to reduce the black float of the display image (image displayed on the screen) and improve the contrast.
In this embodiment, image data is input for each frame. Then, the target brightness determination unit 106 determines the target brightness of each light source for each frame based on the image data of that frame.

Note that the target luminance determination method is not limited to the method described above. For example, the target brightness of each light source may be determined by a method other than the above-described method so that the target brightness is lower in the dark area of the image data than in the bright area of the image data. Further, the target luminance of each light source may be determined according to a user operation (for example, a user operation for changing the light emission luminance of the light source).
The feature amount may be any value as long as it is a value indicating the brightness of the image data. For example, the feature amount may be a representative value (maximum value, minimum value, mode value, intermediate value, average value, etc.) of pixel values of image data to be displayed in the divided area, or displayed in the divided area. It may be a representative value of the luminance value of the power image data. Moreover, the histogram of the pixel value of the image data which should be displayed on a division area may be sufficient, and the histogram of the luminance value of the image data which should be displayed on a division area may be sufficient.

  The control unit 107 adjusts the drive duty ratio for each light source based on the target luminance determined by the target luminance determination unit 106 and the light detection value of the light detection unit 105. Thereby, the control unit 107 adjusts the light emission luminance and the light emission color of the light source unit 104. The control unit 107 is configured as part of a program executed by a microcomputer, for example.

First, when receiving the target luminance for each light source from the target luminance determining unit 106, the control unit 107 determines the ideal duty ratio of the light source for each light source based on the target luminance of the light source. The ideal duty ratio is a drive duty ratio that should be set when the light emission characteristics of the light source are ideal characteristics. In other words, the ideal duty ratio is a drive duty ratio that allows the light emission luminance of the light source to be controlled to the target luminance when the light source does not deteriorate over time and the temperature of the light source is a predetermined temperature.
In the present embodiment, the correspondence relationship between the light emission luminance and the drive duty ratio of a light source having no aging deterioration and a predetermined temperature is measured as the correspondence relationship between the target luminance and the ideal duty ratio. For example, in the manufacturing stage of the display device, the correspondence between the light emission luminance of the light source and the drive duty ratio is measured as the correspondence between the target luminance and the ideal duty ratio. Then, table data indicating the correspondence relationship is stored in advance in the storage unit 103 as an ideal duty ratio table. The control unit 107 reads out the ideal duty ratio corresponding to the target luminance determined by the target luminance determination unit 106 from the ideal duty ratio table for each light source. When the ideal duty ratio corresponding to the target brightness determined by the target brightness determination unit 106 is not prepared in advance, interpolation processing and extrapolation processing using the ideal duty ratio prepared in the ideal duty ratio table are performed. Just do it. Thereby, the ideal duty ratio corresponding to the target luminance determined by the target luminance determining unit 106 can be determined.
In this embodiment, since the target luminance is determined for each frame, the ideal duty ratio is also determined for each frame.
In addition, as a correspondence relationship between the target luminance and the ideal duty ratio, a correspondence relationship for each light source may or may not be prepared. A common correspondence between a plurality of light sources may be prepared. A correspondence relationship for each emission color of the light source may be prepared.

  Next, the control unit 107 receives the light detection value of each light source from the light detection unit 105. Then, the control unit 107 determines the adjusted drive duty ratio for each light source by correcting the ideal duty ratio of the light source based on the light detection value of the light source. Thereafter, the control unit 107 outputs the drive duty ratio (adjusted drive duty ratio) of each light source to the light source drive unit 108.

Specifically, the control unit 107 determines a correction coefficient for each light source based on the light detection value of the light source. The correction coefficient is a correction coefficient for correcting the ideal duty ratio, and is a correction coefficient for correcting a change in the light emission characteristics of the light source due to aged deterioration or a temperature change. In the present embodiment, the light detection value when the light emission characteristic of the light source is an ideal characteristic is measured as the reference light detection value. For example, the light detection value is measured as the reference light detection value in the manufacturing stage of the display device. The reference light detection value is stored in the storage unit 103 in advance. The control unit 107 calculates a correction coefficient by dividing the reference light detection value by the light detection value detected by the light detection unit 105.
In addition, the reference light detection value for every light source may be prepared as a reference light detection value, and it may not be so. One reference light detection value common to a plurality of light sources may be prepared. A reference light detection value for each emission color of the light source may be prepared.

  Then, for each light source, the control unit 107 multiplies the ideal duty ratio of the light source by the correction coefficient of the light source to determine the adjusted drive duty ratio of the light source.

In the present embodiment, the control unit 107 performs different processing depending on whether the lighting time of one light source is longer than a predetermined time or when the lighting time of one light source is shorter than the predetermined time. Details will be described later.
In this embodiment, an example in which the predetermined time is the detection response time will be described. However, the predetermined time may be longer or shorter than the detection response time.

  The light source drive unit 108 generates a pulse signal according to the drive duty ratio (adjusted drive duty ratio) determined by the control unit 107 for each light source, and performs a process of driving the light source with the generated pulse signal.

Next, an example of the flow of processing (local dimming control) in which the display apparatus according to the present embodiment controls the light emission luminance of the light source unit 104 will be described with reference to the flowchart of FIG.
The display device according to the present embodiment performs the processing shown in the flowchart of FIG. 4 for each frame.
First, the target brightness determination unit 106 acquires the feature amount of the image data, and determines the target brightness of each light source based on the acquired feature amount (S11).
Next, the control unit 107 determines an ideal duty ratio for each light source based on the target luminance determined in S11 (S12).
Then, the control unit 107 calculates the adjusted drive duty ratio by multiplying the ideal duty ratio determined in S12 for each light source by the correction coefficient determined in the flowchart shown in FIG. 5 (S13). . The flowchart of FIG. 5 will be described later.
Next, the light source driving unit 108 generates a pulse signal for each light source according to the driving duty ratio calculated in S13, and performs a process of driving the light source with the generated pulse signal (S14).

Next, an example of a processing flow in which the display device according to the present embodiment corrects a change in the light emission characteristics of the light source will be described with reference to the flowchart of FIG.
The process shown in the flowchart of FIG. 5 is performed, for example, at a cycle of 1 minute when the display device is stable. When the display device is turned on, the temperature of the light source changes sharply due to the heat of the light source unit 104, etc., so that the light emission characteristics of the light source change rapidly. Therefore, when the display device is turned on, the process shown in the flowchart of FIG. 5 is executed in a short cycle (for example, a cycle of 5 seconds). In addition, when the brightness of the light source unit 104 is changed by a user operation or the like, the heat generated from the light source unit 104 changes, so that the light emission characteristics of the light source change rapidly. Therefore, when the brightness of the light source unit 104 is changed, the process shown in the flowchart of FIG. 5 is executed in a short cycle.
Note that the above-mentioned “1 minute cycle” and “5 second cycle” are merely examples, and the execution cycle of the flowchart of FIG. 5 is not limited to these cycles.
In the following, processing for one light source will be described, but the processing shown in the flowchart of FIG. 5 is performed for all light sources.

  First, light from the light source is detected by the light detection unit 105 (S21).

  Next, the control unit 107 determines whether or not the lighting time of one light source when the process of S21 is performed is equal to or longer than the detection response time (S22). If the one lighting time of the light source is equal to or longer than the detection response time, the process proceeds to S23. If the one lighting time of the light source is shorter than the detection response time, the process proceeds to S24.

In S23, the control unit 107 detects the current light detection value (the light detection value detected in S21) and the N light beams (N is an integer equal to or greater than 2) used when the drive duty ratio has been adjusted in the past. A representative light detection value (first representative light detection value) representative of the detection value is determined. In the present embodiment, the average value of the N + 1 light detection values is calculated as the first representative light detection value. For example, it is assumed that the current photodetection value (the photodetection value detected in S21) is B0, and the photodetection value used in the adjustment of the drive duty ratio one cycle before is B1. The light detection value used in the adjustment of the drive duty ratio two cycles before is B2, the light detection value used in the adjustment of the drive duty ratio three cycles before is B3, and the drive duty four cycles ago Assume that the photodetection value used in the ratio adjustment is B4. In that case, (B0 + B1 + B2 + B3 + B4) / 5 is calculated as the first representative light detection value.
Here, the “current light detection value” is “a light detection value obtained after a predetermined time (detection response time) has elapsed since the light source started lighting”.
Thereafter, the process proceeds to S25.

Note that the first representative light detection value is not limited to the average value of the N + 1 light detection values. For example, the first representative light detection value may be a maximum value, a minimum value, a mode value, an intermediate value, or the like of N + 1 light detection values.
In this embodiment, an example of N = 4 will be described, but N is not limited to 4. N may be smaller or larger than 4.

In S24, the control unit 107 determines the second representative light detection value.
This will be described in detail below.
First, the control unit 107 estimates a light detection value (estimated light detection value) to be acquired as the current light detection value based on the N light detection values. In this embodiment, the average value of the N light detection values is calculated as the estimated light detection value. For example, it is assumed that the light detection value used in the adjustment of the drive duty ratio one cycle before is B1, and the light detection value used in the adjustment of the drive duty ratio two cycles before is B2. Assume that the light detection value used in the adjustment of the drive duty ratio three cycles before is B3 and the light detection value used in the adjustment of the drive duty ratio four cycles before is B4. In that case, (B1 + B2 + B3 + B4) / 4 is calculated as the estimated light detection value Be.
Then, the control unit 107 determines a representative light detection value (second representative light detection value) representing the estimated light detection value and the N light detection values. In this embodiment, the average value of the N + 1 light detection values is calculated as the second representative light detection value. That is, (Be + B1 + B2 + B3 + B4) / 5 is calculated as the second representative light detection value.
Thereafter, the process proceeds to S25.

The estimated light detection value is not limited to the average value of N light detection values. For example, the estimated light detection value may be a maximum value, a minimum value, a mode value, an intermediate value, or the like of N light detection values.
Note that the second representative light detection value is not limited to the average value of the N + 1 light detection values. For example, the second representative light detection value may be a maximum value, a minimum value, a mode value, an intermediate value, or the like of N + 1 light detection values.

  In S25, the control unit 107 calculates a correction coefficient by dividing the reference light detection value by the representative light detection value. When the process of S23 is performed, the correction coefficient is calculated by dividing the reference light detection value by the first representative light detection value. When the process of S24 is performed, the correction coefficient is calculated by dividing the reference light detection value by the second representative light detection value.

  When the execution cycle of the flowchart of FIG. 5 is longer than the execution cycle of the flowchart of FIG. 4, the control unit 107 uses the correction coefficient calculated immediately before the correction coefficient is calculated next time. The process of S13 in FIG. 4 (calculation of drive duty ratio) is performed. Then, the control unit 107 updates the correction coefficient used in the process of S13 every time the correction coefficient is calculated.

According to the flowcharts shown in FIGS. 4 and 5, the representative light detection value and the reference light detection value recorded in advance in the storage unit 103 are repeatedly compared.
If the representative detection value is smaller than the reference light detection value, the correction coefficient is increased and the drive duty ratio is increased. That is, when the light emission luminance of the light source is reduced, the drive duty ratio is increased. As a result, the light emission luminance of the light source is increased so that the lighting time of the light source within one cycle of light emission of the light source is extended and the decrease in the light emission luminance of the light source is suppressed.
If the representative detection value is larger than the reference light detection value, the correction coefficient is reduced and the drive duty ratio is reduced. That is, when the light emission luminance of the light source increases, the drive duty ratio is reduced. As a result, the light emission luminance of the light source is reduced so that the lighting time of the light source within one cycle of light emission of the light source is shortened and an increase in the light emission luminance of the light source is suppressed.
Since the above processing is executed for each light source, the light emission luminance can be kept constant for all light sources, and the light emission color of the light source unit 104 can also be kept constant. That is, the change in the light emission characteristics of the light source can be corrected with high accuracy.

Furthermore, according to this embodiment, when the lighting time of one light source is equal to or longer than the detection response time, the drive duty ratio is adjusted using the first representative light detection value. That is, when the lighting time of one light source is equal to or longer than the detection response time, the drive duty ratio is adjusted using the current light detection value and the N light detection values used in the past. Thereby, the change in the light emission characteristics of the light source can be corrected with high accuracy.
Further, according to the present embodiment, when the one-time lighting time of the light source is shorter than the detection response time, the drive duty ratio is adjusted using the second representative light detection value. That is, when the lighting time of one light source is equal to or longer than the detection response time, the drive duty ratio is adjusted using only the N light detection values used in the past without using the current light detection value. Is done. Thereby, even if the lighting time of one light source is shorter than the detection response time, the change in the light emission characteristics of the light source can be corrected with high accuracy. As a result, highly accurate correction processing (processing for correcting the change in the light emission characteristics of the light source with high accuracy) can be performed more reliably than in the past.

  As described above, according to the present embodiment, a change in the light emission characteristics of the light source is corrected by using a stable light detection value regardless of whether the lighting time of the light source is long or short. can do. As a result, a change in the light emission characteristics of the light source can be reliably and accurately reduced.

  In this embodiment, the example of performing the two-stage process of determining the ideal duty ratio and correcting the ideal duty ratio has been described, but the present invention is not limited to this. Instead of determining the ideal duty ratio, the adjusted drive duty ratio may be determined from the target brightness and the light detection value in one step of processing.

  In this embodiment, the example in which the drive duty ratio is adjusted using the representative light detection value has been described. However, the present invention is not limited to this. For example, when the lighting time of one light source is a predetermined time or more, the drive duty ratio may be determined using only the current light detection value. And when the lighting time of one time of a light source is shorter than predetermined time, you may determine a drive duty ratio using an estimated light detection value. When the lighting time of one light source is shorter than a predetermined time, only one light detection value used in the past (for example, the light detection value used last time) is determined without determining the estimated light detection value. It may be used to determine the drive duty ratio.

  In this embodiment, the “photodetection value used in the past” may or may not be a representative photodetection value used in the past. For example, the “light detection value used in the past” is a light detection value (a light detection value or an estimated light detection value of the light detection unit 105) used when determining a representative light detection value used in the past. There may be.

<Example 2>
A light source device and a control method thereof according to Embodiment 2 of the present invention will be described.
In the first embodiment, the example in which the light emission luminance of the light source is controlled based on the light detection value of the light detection unit 105 has been described. In this embodiment, an example in which the light emission luminance of a light source is controlled in consideration of the temperature of the light source will be described. Hereinafter, a description will be given focusing on differences from the first embodiment.

FIG. 6 is a block diagram illustrating an example of the configuration of the display device according to the present embodiment. As shown in FIG. 6, the display apparatus according to the present embodiment includes an image input unit 101, a display unit 102, a storage unit 103, a light source unit 104, a light detection unit 105, a target luminance determination unit 106, a control unit 207, and a light source drive. Unit 108, temperature detection unit 209, and the like.
Hereinafter, each functional unit of the display device according to the present embodiment will be described. In addition, the same code | symbol is attached | subjected to the same function part as Example 1 (FIG. 1), and the description is abbreviate | omitted.

The temperature detection unit 209 detects the temperature of the light source included in the light source unit 104 and outputs the detection result to the control unit 207. In the present embodiment, one temperature detection unit 209 is provided for each divided region. The temperature detected by the temperature detection unit 209 is regarded as the temperature of each light source provided in the divided area corresponding to the temperature detection unit 209. That is, the temperature detection unit 209 detects the temperature of each light source provided in the divided region corresponding to the temperature detection unit 209.
In addition, although a present Example demonstrates the example in case the one temperature detection part 209 is provided for every division area, it is not restricted to this. For example, one temperature detection unit 209 may be provided for each light source, or one temperature detection unit 209 may be provided for all light sources.

The operation of the control unit 207 when the lighting time of one light source is equal to or longer than a predetermined time (detection response time in the present embodiment) is the same as that of the control unit 107 of the first embodiment.
The operation of the control unit 207 is different from that of the control unit 107 when the lighting time of the light source is shorter than a predetermined time (detection response time in this embodiment).
The control unit 207 receives the temperature detection value of each light source from the temperature detection unit 201. This process is performed regardless of whether or not the lighting time of the light source is equal to or longer than the detection response time.
When the lighting time of one light source is shorter than the detection response time, the control unit 207 drives after adjustment based on the light detection value of the light detection unit 105 and the temperature detection value of the temperature detection unit 209. Determine the duty ratio.

Next, an example of the flow of processing in which the display device in this embodiment corrects the change in the light emission characteristics of the light source will be described with reference to the flowchart of FIG.
In the following, processing for one light source will be described, but the processing shown in the flowchart of FIG. 7 is performed for all light sources.
Note that the flow of local dimming control according to the present embodiment is the same as that of the first embodiment (FIG. 4), and a description thereof will be omitted.

First, the light detection unit 105 detects light from the light source (S31).
Next, the temperature detection unit 201 detects the temperature of the light source (S32).
Then, the control unit 207 determines whether or not the lighting time of one light source when the process of S31 is performed is equal to or longer than the detection response time (S33). If the one lighting time of the light source is equal to or longer than the detection response time, the process proceeds to S34. If the one lighting time of the light source is shorter than the detection response time, the process proceeds to S35.

  In S34, the first representative light detection value is determined in the same manner as in S23 of FIG. Then, the process proceeds to S36.

In S35, the control unit 207 determines the second representative light detection value in consideration of a change in the temperature detection value. Then, the process proceeds to S36.
This will be described in detail below.

  First, the control unit 207 determines the estimated light detection value by the same method as in the first embodiment. For example, it is assumed that the light detection value used in the adjustment of the drive duty ratio one cycle before is B1, and the light detection value used in the adjustment of the drive duty ratio two cycles before is B2. Assume that the light detection value used in the adjustment of the drive duty ratio three cycles before is B3 and the light detection value used in the adjustment of the drive duty ratio four cycles before is B4. In that case, (B1 + B2 + B3 + B4) / 4 is calculated as the estimated light detection value Be.

Next, the control unit 207 corrects the estimated light detection value based on the change in the temperature detection value. Specifically, the control unit 207 displays the current temperature detection value (the temperature detection value detected in S32) and the N temperature detection values when the N light detection values used in the past are obtained. Based on the above, the estimated light detection value is corrected. In this embodiment, the average value of the N detected temperature values is calculated as the representative temperature detected value. Then, the estimated light detection value is corrected using the current temperature detection value and the representative temperature detection value.
For example, the temperature detection value detected in S32 is C0, the temperature detection value when the light detection value B1 is obtained is C1, and the temperature detection value when the light detection value B2 is obtained is C2. Suppose. The temperature detection value when the light detection value B3 is obtained is C3, and the temperature detection value when the light detection value B4 is obtained is C4. In that case, (C1 + C2 + C3 + C4) / 4 is calculated as the representative temperature detection value Cr. Then, the temperature detection value C0 and the representative temperature detection value Cr are compared, and the estimated light detection value Be is corrected according to the comparison result. For example, when C0 <Cr, it is determined that the light emission efficiency has increased due to the temperature change of the light source, and the estimated light detection value Be is increased. In the case of C0 <Cr, it is determined that the light emission efficiency has decreased due to the temperature change of the light source, and the estimated light detection value Be is reduced.
The representative temperature detection value is not limited to the average value of the N temperature detection values. For example, the representative temperature detection value may be a maximum value, a minimum value, a mode value, an intermediate value, or the like of N temperature detection values.

  Then, the control unit 207 calculates the second representative light detection value by the same method as in the first embodiment, using the corrected estimated detection value.

  In S36, the correction coefficient is calculated in the same manner as in S25 of FIG.

  When the execution cycle of the flowchart of FIG. 7 is longer than the execution cycle of the flowchart of FIG. 4, the control unit 207 uses the correction coefficient calculated immediately before the correction coefficient is calculated next time. The process of S13 in FIG. 4 (calculation of drive duty ratio) is performed. Then, the control unit 207 updates the correction coefficient used in the process of S13 every time the correction coefficient is calculated.

  As described above, according to the present embodiment, the change in the light emission characteristic of the light source is corrected in consideration of the change in the light emission characteristic due to the temperature change of the light source. Thereby, it is possible to correct the change in the light emission characteristics with higher accuracy than in the first embodiment.

  In this embodiment, the example in which the estimated detection value is corrected based on the current temperature detection value and the representative temperature detection value has been described. However, the present invention is not limited to this. For example, the estimated detection value may be corrected using the current temperature detection value and the N temperature detection values without determining the representative temperature detection value. Specifically, a function indicating a time change of the temperature detection value is calculated from the N + 1 temperature detection values, and it is determined whether or not the temperature of the light source is increased according to the slope of the calculated function. Good. Even if the estimated light detection value is corrected so that the estimated light detection value is increased when the temperature of the light source is increased, and the estimated light detection value is decreased when the temperature of the light source is decreased. Good.

  As described in the first embodiment, the drive duty ratio may be adjusted without determining the estimated light detection value or the representative light detection value. For example, when the lighting time of one light source is shorter than a predetermined time, the current temperature detection value, one or more light detection values used in the past, and 1 when the drive duty ratio is adjusted in the past The drive duty ratio may be adjusted using two or more temperature detection values.

<Example 3>
A light source device and a control method thereof according to Embodiment 3 of the present invention will be described.
FIG. 8 is a block diagram illustrating an outline of an image display apparatus 1000 including the light source device according to the present embodiment as a backlight device for an image display apparatus such as a liquid crystal display apparatus.

The image input unit 1010 acquires image data (input image data) and outputs the input image data to the image analysis unit 1020. The input image data is acquired from an external device, for example.
Note that the image display apparatus 1000 may have a storage medium (magnetic disk, semiconductor memory, optical disk, etc.) for storing image data. Then, the image input unit 1010 may acquire input image data from the storage medium.

  The image analysis unit 1020 analyzes the input image data and determines the target luminance of the backlight 1070 (specifically, the target luminance of each light source included in the backlight 1070). The image analysis unit 1020 generates display image data by correcting the input image data based on the determined target luminance. Then, the image analysis unit 1020 outputs the generated display image data to the LCD control unit 1030, and notifies the backlight control unit 1050 of the determined target luminance.

  The LCD control unit 1030 controls the LCD panel 1040 according to the display image data. The LCD panel 1040 is a display panel having a plurality of liquid crystal elements corresponding to a plurality of pixels. The LCD control unit 1030 orients the liquid crystal elements of the LCD panel 1040 according to the display image data, thereby bringing the LCD panel 1040 into a state where image display is possible.

  The backlight control unit 1050 sets a necessary current value, a PWM duty ratio (drive duty ratio), and the like for the LED driver 1060 so that the target luminance determined by the image analysis unit 1020 is realized. In this embodiment, the backlight control unit 1050 determines the current value and the driving duty based on the target luminance determined by the image analysis unit 1020 and the luminance (light detection value; sensor value) detected by the luminance sensor 1080. Set the ratio etc.

  The LED driver 1060 has a plurality of channels. Each channel of the LED driver 1060 is connected to an LED block (light source) included in the backlight 1070. In this embodiment, the backlight 1070 has a plurality of LED blocks arranged in a matrix. The plurality of LED blocks can individually control light emission. The LED driver 1060 causes the LED block to emit light periodically. The LED driver 1060 performs pulse width modulation control (PWM control) for adjusting the drive duty ratio of the LED block according to the conditions set by the backlight control unit 1050. The drive duty ratio is a ratio of the total lighting time of the LED block within one period to one period of light emission of the LED block. By performing PWM control, the light emission luminance of the LED block is controlled.

The luminance sensor 1080 detects (measures) the luminance of light emitted from the backlight (LED block) and applied to the luminance sensor 1080. Then, the luminance sensor 1080 outputs the detected luminance (sensor value) to the sensor control unit 1090. In other words, the luminance sensor 1080 receives the light emitted from the backlight 1070 and notifies the sensor control unit 1090 of the luminance of the received light.
Note that the optical sensor is not limited to a luminance sensor. As the optical sensor, a chromaticity sensor that detects the color of light may be used, or a sensor that detects both the luminance and the color of light may be used.

  The sensor control unit 1090 acquires the output value (sensor value) from the luminance sensor 1080 as a measurement result of the luminance of light emitted from the measurement target LED block (acquisition target LED block) during the sensor value acquisition period. Then, the sensor control unit 1090 feeds back the sensor value for each LED block to the backlight control unit 1050. The sensor value acquisition period is a period from when the measurement target LED block starts to light until a predetermined time elapses.

  Based on the sensor value for each LED block acquired from the sensor control unit 1090, the backlight control unit 1050 sets the current value and the drive duty ratio that are set in the LED driver 1060 so as to minimize the luminance unevenness of the backlight 1070. adjust. The light emitted from the backlight 1070 is transmitted through each pixel of the LCD panel 1040 with the transmittance after being controlled by the LCD control unit 1030, whereby an image that can be observed by the observer is displayed on the image display unit 1100. The image display unit 1100 is, for example, a glass substrate provided on the front surface of the LCD panel 1040. The front surface of the image display unit 1100 (the surface opposite to the LCD panel 1040 side) is a screen.

  The backlight control unit 1050 operates in synchronization with the sensor control unit 1090. Specifically, the backlight control unit 1050 turns off the non-acquisition target LED blocks that are LED blocks other than the acquisition target LED block in the sensor value acquisition period. Thereby, a value that well represents the luminance of light from the acquisition target LED block can be obtained as the sensor value.

  By the way, when the drive duty ratio of the acquisition target LED block becomes low, as shown in FIG. 9, the one lighting time of the acquisition target LED block becomes a value shorter than the length (predetermined time) of the sensor acquisition period. There is. As a result, in the sensor control unit 1090, as the sensor value of the acquisition target LED block, not only the sensor value when the acquisition target LED block is lit but also the sensor value when the acquisition target LED block is turned off (invalid Appropriate sensor values) may also be obtained. In the prior art, the drive duty ratio may be erroneously adjusted using such an inappropriate sensor value.

In order to prevent such misadjustment, in the present embodiment, the period after the acquisition target LED block is extinguished in the sensor value acquisition period when the one lighting time of the acquisition target LED block is shorter than the predetermined time. The drive duty ratio is adjusted without using the obtained sensor value.
In addition, when one lighting time of the acquisition target LED block is a predetermined time or more, the drive duty ratio is adjusted using the sensor value obtained during the sensor value acquisition period.
Hereinafter, the above process will be described in detail.

The backlight control unit 1050 communicates with the LED driver 1060 before adjusting the drive duty ratio, and acquires the drive duty ratio currently set in the acquisition target LED block from the LED driver 1060. Then, the backlight control unit 1050 determines whether one lighting time of the acquisition target LED block is shorter than a predetermined time based on the drive duty ratio currently set for the acquisition target LED block.
Note that the backlight control unit 1050 may grasp the drive duty ratio currently set for each LED block. In that case, the process which acquires the drive duty ratio currently set to the acquisition object LED block from the LED driver 1060 is unnecessary.

  As illustrated in FIG. 10, the backlight control unit 1050 asserts the sensor value notification flag at the timing of turning on the acquisition target LED block and turning off the non-acquisition target LED block. 10, the sensor value notification flag “High” means that the sensor value notification flag is asserted, and the sensor value notification flag “Low” means that the sensor value notification flag is negated. The sensor control unit 1090 notifies the backlight control unit 1050 of the sensor value acquired during the period when the sensor value notification flag is asserted.

And when the lighting time of one time of acquisition object LED block is shorter than predetermined time, as shown in FIG. 10, the backlight control part 1050 is a sensor value notification flag at the timing when the process object LED block turned off. To negate. Thereby, it can suppress that the sensor value when the acquisition object LED block is light-extinguishing is notified to the backlight control part 1050, and can suppress that a drive duty ratio is misadjusted. When the lighting time of one LED block to be acquired is equal to or longer than a predetermined time, the backlight control unit 1050 negates the sensor value notification flag at a timing when a predetermined time has elapsed from the timing at which the sensor value notification flag is asserted. To do.

  Thereafter, the backlight control unit 1090 relights the non-acquisition target LED block that has been turned off at a timing when a predetermined time has elapsed from the timing at which the sensor value notification flag is asserted.

  The operation of the sensor control unit 1090 will be described using the flowchart of FIG. FIG. 11 is a flowchart illustrating an example of a sensor value acquisition process (a process in which the sensor control unit 1090 acquires a sensor value from the luminance sensor 1080 and notifies the backlight control unit 1050) according to the present embodiment.

First, the sensor control unit 1090 determines whether or not the sensor value notification flag is “High” (S401).
When the sensor value notification flag becomes “High” (S401: YES), the sensor control unit 1090 starts acquiring sensor values (S402).
Then, the sensor control unit 1090 ends the acquisition of the sensor value at a timing when a predetermined time has elapsed from the timing at which the sensor value notification flag becomes “High” (S403).
Simultaneously with the end of acquisition of the sensor value, the sensor control unit 1090 determines whether or not the sensor value notification flag is “High” (S404).

  If the sensor value notification flag is “High” at the moment of the end of sensor value acquisition (S404: YES), the sensor control unit 1090 displays the sensor value acquired between the process of S402 and the process of S403. The backlight control unit 1050 is notified (S405). In the backlight control unit 1050, the drive duty ratio is adjusted using the sensor value acquired from the process of S402 to the process of S403.

  On the other hand, when the sensor value notification flag is “Low” at the moment when the sensor value acquisition ends, it is highly likely that an inappropriate sensor value has been acquired. Specifically, since the lighting period of the acquisition target LED block has ended before the acquisition of the sensor value is completed, there is a high possibility that a sensor value lower than the desired value has been acquired. In this case, the sensor control unit 1090 determines that it is not preferable to use the sensor value acquired between the process of S402 and the process of S403, and acquires it between the process of S402 and the process of S403. The sensor value is discarded (S406). By performing such control, use of an inappropriate sensor value for adjusting the drive duty ratio can be suppressed, and an increase in unevenness of light from the backlight 1070 can be suppressed.

In addition, when the sensor value notification flag is “Low” at the moment when the sensor value acquisition ends, the process of acquiring the sensor value of the acquisition target LED block may be executed again. For example, when the sensor value notification flag is “Low” at the moment of the end of sensor value acquisition, the backlight control unit 1050 reduces the current value of the acquisition target LED block and sets the drive duty ratio of the acquisition target LED block. May be raised. Thereafter, the process of acquiring the sensor value of the acquisition target LED block may be executed again.
Further, when the sensor value notification flag is “Low” at the moment when the sensor value acquisition ends, the drive duty ratio may be adjusted based on the past acquisition result.

  Of the sensor values acquired from the process of S402 to the process of S403, the sensor value acquired during the period when the sensor value notification flag is “High” may be notified to the backlight control unit 1050. . Then, the drive duty ratio may be adjusted using the sensor value acquired during the period when the sensor value notification flag is “High” among the sensor values acquired from the process of S402 to the process of S403. . Such processing can be realized, for example, by the sensor control unit 1090 monitoring a sensor value notification flag during execution of sensor value acquisition. Further, as the sensor value acquired during the period when the sensor value notification flag is “Low”, the sensor value acquired during the period when the sensor value notification flag is “High” may be substituted.

  Although not described, the sensor control unit 1090 samples the sensor value of the luminance sensor 1080 once or a plurality of times within the period from the process of S402 to the process of S403. Then, the sensor control unit 1090 notifies the backlight control unit 1050 of the acquired one or more sensor values. As a method for adjusting the drive duty ratio using a plurality of sensor values, there is a method of calculating an average value of a plurality of sensor values and adjusting the drive duty ratio based on the calculated average value. Here, among the plurality of sensor values, the sensor value having the largest value (maximum sensor value) and the sensor value having the smallest value (minimum sensor value) are likely to be inappropriate values. For example, the maximum sensor value and the minimum sensor value are highly likely to be greatly affected by noise. Therefore, it is preferable not to use at least one of the maximum sensor value and the minimum sensor value when adjusting the drive duty ratio.

<Example 4>
A light source device and a control method thereof according to Embodiment 4 of the present invention will be described.
In the third embodiment, the example in which the non-acquisition target LED block is turned off and the sensor value acquired from the timing when the acquisition target LED block is lit is notified to the backlight control unit 1050 has been described. However, immediately after the LED block is turned on, the sensor value may not be stabilized due to the influence of the delay in the output of the sensor value, the swing back due to a sudden change in the sensor value, and the like. Therefore, in order to adjust the drive duty ratio using a more accurate value, it is better to acquire the sensor value notified to the backlight control unit 1050 after waiting for a certain amount of time (wait time). FIG. 12 shows an example in which the acquisition of sensor values is delayed. FIG. 12 shows an example in which the sensor value is sampled four times for one lighting of the acquisition target LED block. The backlight control unit 1050 adjusts the drive duty ratio based on the average value of the four sensor values obtained by the four samplings.

  However, if a sufficient waiting time is ensured, a sufficient number of sensor values cannot be obtained as accurate sensor values. FIG. 13 shows an example when the drive duty ratio is low. In the example of FIG. 13, the acquisition target LED block is turned off before the acquisition of the sensor value is completed. Therefore, out of the four sensor values 1 to 4 obtained by the two samplings, an accurate value is obtained as the first two sensor values 1 and 2, but the latter two sensor values 3 and 4 are obtained. As a result, an inappropriate value will be obtained. If such an average value of the two sensor values 1 and 2 is used, the drive duty ratio cannot be adjusted with high accuracy.

Therefore, in this embodiment, a short time (including 0) is set as the wait time, and the number of sensor values that can be used for adjusting the drive duty ratio is increased.
Specifically, the sensor control unit 1090 acquires M (M is an integer of 3 or more) sensor values in the sensor value acquisition period, and m (m is 3 or more and less than M) of the M sensor values. (Integer) sensor value is notified to the backlight control unit 1050. Then, the sensor control unit 1090 displays the m sensor values acquired immediately before the acquisition target LED block is turned off when the one lighting time of the acquisition target LED block is shorter than a predetermined time. Notify
In the backlight control unit 1050, the drive duty ratio is adjusted based on the m sensor values.

Note that M and m are preferably sufficiently large values.
In the following, an example where m = 4 will be described, but m may be larger or smaller than four. In the following, an example where M = 8 will be described, but M may be larger or smaller than eight.

  FIG. 14 shows an example of sensor value acquisition processing according to the present embodiment. FIG. 14 shows an example in which the drive duty ratio is high and the lighting time for one time of the acquisition target LED block is equal to or longer than a predetermined time. As shown in FIG. 14, in this embodiment, the sensor control unit 1090 performs sampling eight times during the sensor value acquisition period. In this embodiment, acquisition of the sensor value is started from the timing when the sensor value notification flag is asserted without setting the wait time. Thereby, eight samplings are possible during the sensor value acquisition period. However, among the eight sensor values 1 to 8 obtained by sampling eight times, the sensor value obtained at an early time is highly likely not to be a stable value. It is preferable to use the sensor values obtained in Therefore, in this embodiment, the sensor control unit 1090 notifies the backlight control unit 1050 of the second half sensor values 5 to 8 without notifying the first half sensor values 1 to 4 to the backlight control unit 1050. Thereby, the backlight control unit 1050 adjusts the drive duty ratio based on the average value of the four sensor values 5 to 8.

  FIG. 15 shows another example of the sensor value acquisition process according to the present embodiment. FIG. 15 shows an example in which the drive duty ratio is low and the lighting time of one acquisition target LED block is a predetermined time or more. In the example of FIG. 15, the acquisition target LED is turned off at the acquisition timing of the sensor values 7 and 8. Therefore, the sensor values 7 and 8 are inappropriate values. It can be determined that the sensor values 7 and 8 are inappropriate values by checking the sensor notification flag. When the sensor control unit 1090 determines that the sensor values 7 and 8 are inappropriate values based on the sensor notification flag, the sensor control unit 1090 excludes the sensor values 7 and 8 from the sensor values notified to the backlight control unit 1050. As described above, it is preferable to use a sensor value obtained at a later time for adjusting the drive duty ratio. The sensor control unit 1090 determines that the four sensor values 3 to 6 obtained immediately before the acquisition target LED block is turned off are appropriate as the sensor values to be notified to the backlight control unit 1050, and the four sensor values. 3 to 6 are notified to the backlight control unit 1050. Thereby, the backlight control unit 1050 adjusts the drive duty ratio based on the average value of the four sensor values 3 to 6.

  As described above, according to the present embodiment, the sensor control unit 1090 acquires many sensor values by advancing the timing for starting acquisition of sensor values. The sensor value when the acquisition target LED block is turned off is excluded from many sensor values, and a sensor value with high stability is preferentially used for adjusting the drive duty ratio. Thereby, it is possible to suppress the sensor value when the acquisition target LED block is turned off from being used for adjusting the drive duty ratio, and to increase the number of sensor values used for adjusting the drive duty ratio. . As a result, the drive duty ratio can be adjusted with high accuracy.

<Example 5>
A light source device and a control method thereof according to Embodiment 5 of the present invention will be described.
In the present embodiment, an example will be described in which the number of sensor values used for adjusting the drive duty ratio is changed depending on the situation as well as the sensor value used for adjusting the drive duty ratio is selected.
Specifically, in the present embodiment, a correspondence relationship between the lighting time of one acquisition target LED block and the number of sensor values and the time position used when adjusting the drive duty ratio is determined in advance. It shall be. The correspondence relationship is stored in advance in a storage unit included in the image display device. In this embodiment, the sensor control unit 1090 determines the number of sensor values used for adjusting the drive duty ratio and the time position based on one lighting time of the acquisition target LED block and the above correspondence. decide. The “time position of the sensor value” is a relative value of the time when the sensor value is acquired with respect to the time when the sensor control unit 1090 starts acquiring the sensor value.
The correspondence relationship may be a fixed relationship determined in advance by a manufacturer or the like, or a relationship that can be changed by the user.

  FIG. 16 shows an example of sensor value acquisition processing according to the present embodiment. FIG. 16 shows an example in which the drive duty ratio is lower than that in FIG. In the example of FIG. 16, the acquisition target LED is turned off at the acquisition timing of the sensor values 6 to 8. Therefore, the sensor values 6 to 8 are inappropriate values. However, the sensor values 1 to 4 are all values before stabilization, and the sensor value 1 is a value having a particularly large error. Therefore, the drive duty ratio can be adjusted with higher accuracy by using the sensor values 2 to 4 than the sensor values 1 to 4 as the sensor values used for adjusting the drive duty ratio. In the present embodiment, the correspondence relationship is determined in advance so that sensor values 2 to 4 are selected for the drive duty ratio shown in FIG. As a result, the sensor control unit 1090 performs processing for notifying the backlight control unit 1050 of the three sensor values 2 to 4, and the backlight control unit 1050 sets the average value of the three sensor values 2 to 4. Based on this, the drive duty ratio is adjusted.

  In addition, the correspondence is determined so that sensor values 3 and 4 are selected for a lower drive duty ratio. Therefore, when the drive duty ratio further decreases, the sensor control unit 1090 performs processing for notifying the backlight control unit 1050 of the two sensor values 3 and 4. The backlight control unit 1050 adjusts the drive duty ratio based on the average value of the two sensor values 3 and 4.

Thus, if the number of sensor values and the time position average used when adjusting the drive duty ratio are changed according to the situation, a sensor with relatively high reliability even when the drive duty ratio is low It becomes possible to adjust the drive duty ratio with high accuracy using the value.
Note that the correspondence relationship between the lighting time of one time of the acquisition target LED block and the number of sensor values and the time position used when adjusting the drive duty ratio is not limited to the above relationship. The correspondence relationship may be any relationship as long as the drive duty ratio can be adjusted with high accuracy.
In the above correspondence relationship, a plurality of patterns of sensor values and time positions may be associated with one drive duty ratio. The reliability may be associated with each of the plurality of patterns. In that case, what is necessary is just to determine the number of sensor values to be used, and a time position according to the pattern with the highest reliability from a plurality of patterns.

<Other examples>
The present invention can also be implemented by a system (or a device such as a CPU or MPU) of a system or apparatus that implements the functions of the above-described embodiments by reading and executing a program recorded in a storage device. The present invention can also be implemented by a method comprising steps executed by a computer of a system or apparatus that implements the functions of the above-described embodiments by reading and executing a program recorded in a storage device, for example. . For this purpose, the program is stored in the computer from, for example, various types of recording media that can serve as the storage device (ie, computer-readable recording media that holds data non-temporarily). Provided to. Therefore, the computer (including devices such as CPU and MPU), the method, the program (including program code and program product), and the computer-readable recording medium that holds the program non-temporarily are all present. It is included in the category of the invention.

  104: Light source unit 105: Light detection unit 106: Target luminance determination unit 107: Control unit

Claims (41)

A light source that emits light periodically;
Light detection means for detecting light emitted from the light source;
Determining means for determining a target luminance of the light source;
Based on the target luminance determined by the determining means and the light detection value of the light detecting means, a drive duty ratio that is a ratio of the total lighting time of the light source within one period to one period of light emission of the light source Adjusting means for adjusting
Have
The adjusting means includes
When the lighting time of one time of the light source is equal to or longer than a predetermined time, the drive duty ratio is adjusted using a light detection value obtained after the predetermined time has elapsed since the light source started lighting. ,
The drive duty ratio is adjusted using a light detection value used when the drive duty ratio has been adjusted in the past when the lighting time of the light source once is shorter than the predetermined time. Light source device. The light source device according to claim 1, wherein the predetermined time is a time required for the light detection value to be stabilized. The adjusting means is configured to use N light detection values (N is an integer of 2 or more) used in the past when the driving duty ratio is adjusted when the lighting time of the light source is shorter than the predetermined time. 3. The light source device according to claim 1, wherein the drive duty ratio is adjusted using an estimated light detection value that is a value based on. The light source device according to claim 3, wherein the estimated light detection value is an average value of the N light detection values. The adjusting means includes
When the one-time lighting time of the light source is equal to or longer than the predetermined time, the drive duty ratio is adjusted using a representative light detection value representing the current light detection value and the N light detection values. ,
When the one-time lighting time of the light source is shorter than the predetermined time, the drive duty ratio is adjusted using a representative light detection value representing the estimated light detection value and the N light detection values. The light source device according to claim 3, wherein the light source device is a light source device. The light source device according to claim 5, wherein the representative light detection value is an average value of N + 1 light detection values. A temperature detecting means for detecting the temperature of the light source;
The adjustment unit is configured to adjust the current temperature detection value of the temperature detection unit and the light detection value used when the drive duty ratio has been adjusted in the past when a single lighting time of the light source is shorter than the predetermined time. The light source device according to claim 1, wherein the drive duty ratio is adjusted using a temperature detection value obtained when the drive duty ratio has been adjusted in the past. A temperature detecting means for detecting the temperature of the light source;
In the case where the one lighting time of the light source is shorter than the predetermined time, the adjusting means
Correcting the estimated light detection value based on a current temperature detection value of the temperature detection means and N temperature detection values when the N light detection values are obtained;
The light source device according to claim 3, wherein the drive duty ratio is adjusted using an estimated light detection value after correction. The adjusting means is configured to obtain the estimated light detection value, the current temperature detection value, and the N light detection values when the one-time lighting time of the light source is shorter than the predetermined time. The light source device according to claim 8, wherein correction is performed based on a representative temperature detection value representing N temperature detection values. The light source device according to claim 9, wherein the representative temperature detection value is an average value of N + 1 temperature detection values. The adjusting means includes
Based on the target brightness, determine an ideal duty ratio that is a drive duty ratio to be set when the light emission characteristics of the light source are ideal characteristics;
The light source device according to claim 1, wherein the adjusted drive duty ratio is determined by correcting the ideal duty ratio based on the light detection value. The light source device is used in a display device that displays an image on a screen by modulating light emitted from the light source device,
The light source device according to claim 1, wherein the determining unit determines a target luminance based on image data displayed on the display device. The light source device is used in a display device that displays an image on a screen by modulating light emitted from the light source device,
The light source device according to claim 1, wherein the one cycle is a period of one frame of image data. The light source device has a plurality of light sources,
The light source device according to claim 1, wherein a driving duty ratio of the light source is adjusted for each light source. A light source that emits light periodically;
Light detection means for detecting light emitted from the light source;
Determining means for determining a target luminance of the light source;
Based on the target luminance determined by the determining means and the light detection value of the light detecting means, a drive duty ratio that is a ratio of the total lighting time of the light source within one period to one period of light emission of the light source Adjusting means for adjusting
Have
The adjusting means includes
When the lighting time of one time of the light source is equal to or longer than a predetermined time, using the light detection value obtained in the acquisition period that is a period from when the light source starts lighting until the predetermined time elapses, Adjusting the drive duty ratio;
When the lighting time of the light source once is shorter than the predetermined time, the drive duty ratio is adjusted without using the light detection value obtained in the acquisition period after the light source is turned off. And a light source device. The adjusting means uses the light source as a light detection value obtained from the timing when the light source is extinguished until the timing when the acquisition period ends when one lighting time of the light source is shorter than the predetermined time. The light source device according to claim 15, wherein a light detection value obtained before the light is turned off is used. The light source device according to claim 15 or 16, wherein the adjustment unit adjusts the driving duty ratio based on a plurality of light detection values obtained within a period. In the acquisition period, M sensor values (M is an integer of 3 or more) are acquired,
The adjusting means includes
The drive duty ratio is adjusted using m (m is an integer less than or equal to 3 and less than M) sensor values among the M sensor values.
The drive duty ratio is adjusted using m sensor values acquired immediately before the light source is turned off when a single lighting time of the light source is shorter than the predetermined time. 18. The light source device according to 17. The correspondence between the lighting time of the light source once and the number and time position of the light detection values used when adjusting the drive duty ratio is determined in advance.
The adjusting means determines the number of light detection values and the time position used for adjusting the drive duty ratio based on a single lighting time of the light source and the correspondence relationship. Item 18. The light source device according to Item 17. The light source device according to claim 17, wherein the adjustment unit adjusts the drive duty ratio based on an average value of the plurality of light detection values. A light source that emits light periodically;
Light detection means for detecting light emitted from the light source;
A method of controlling a light source device comprising:
A determining step for determining a target brightness of the light source;
Based on the target luminance determined in the determining step and the light detection value of the light detection means, a drive duty ratio that is a ratio of the total lighting time of the light source within one cycle to one cycle of light emission of the light source Adjustment steps to adjust,
Have
In the adjustment step,
When the lighting time of one time of the light source is equal to or longer than a predetermined time, the drive duty ratio is adjusted using a light detection value obtained after the predetermined time has elapsed since the light source started lighting. ,
The drive duty ratio is adjusted using a light detection value used when the drive duty ratio has been adjusted in the past when the lighting time of the light source once is shorter than the predetermined time. Control method of light source device. The method of controlling a light source device according to claim 21, wherein the predetermined time is a time required for the light detection value to be stabilized. In the adjustment step, N light detection values (N is an integer of 2 or more) used in the past when the drive duty ratio is adjusted when the one lighting time of the light source is shorter than the predetermined time. 23. The method of controlling a light source device according to claim 21 or 22, wherein the drive duty ratio is adjusted using an estimated light detection value that is a value based on. The method of controlling a light source device according to claim 23, wherein the estimated light detection value is an average value of the N light detection values. In the adjustment step,
When the one-time lighting time of the light source is equal to or longer than the predetermined time, the drive duty ratio is adjusted using a representative light detection value representing the current light detection value and the N light detection values. ,
When the one-time lighting time of the light source is shorter than the predetermined time, the drive duty ratio is adjusted using a representative light detection value representing the estimated light detection value and the N light detection values. 25. The method of controlling a light source device according to claim 23 or 24. 26. The method according to claim 25, wherein the representative light detection value is an average value of N + 1 light detection values. The light source device further includes temperature detection means for detecting the temperature of the light source,
In the adjustment step, when the lighting time of the light source once is shorter than the predetermined time, the current temperature detection value of the temperature detection means, the light detection value used when the drive duty ratio has been adjusted in the past 27. The method of controlling a light source device according to claim 21, wherein the drive duty ratio is adjusted using a temperature detection value obtained when the drive duty ratio has been adjusted in the past. . The light source device further includes temperature detection means for detecting the temperature of the light source,
In the adjustment step, when the lighting time of one time of the light source is shorter than the predetermined time,
Correcting the estimated light detection value based on a current temperature detection value of the temperature detection means and N temperature detection values when the N light detection values are obtained;
27. The method of controlling a light source device according to any one of claims 23 to 26, wherein the drive duty ratio is adjusted using a corrected estimated light detection value. In the adjustment step, when the lighting time of one time of the light source is shorter than the predetermined time, the estimated light detection value, the current temperature detection value, and the N light detection values are obtained. 29. The method of controlling a light source device according to claim 28, wherein correction is performed based on representative temperature detection values that represent N temperature detection values. 30. The method of controlling a light source device according to claim 29, wherein the representative temperature detection value is an average value of N + 1 temperature detection values. In the adjustment step,
Based on the target brightness, determine an ideal duty ratio that is a drive duty ratio to be set when the light emission characteristics of the light source are ideal characteristics;
31. The method of controlling a light source device according to claim 21, wherein the adjusted drive duty ratio is determined by correcting the ideal duty ratio based on the light detection value. The light source device is used in a display device that displays an image on a screen by modulating light emitted from the light source device,
The method of controlling a light source device according to any one of claims 21 to 31, wherein in the determining step, a target luminance is determined based on image data displayed on the display device. The light source device is used in a display device that displays an image on a screen by modulating light emitted from the light source device,
The method of controlling a light source device according to any one of claims 21 to 32, wherein the one cycle is a period of one frame of image data. The light source device has a plurality of light sources,
The method of controlling a light source device according to any one of claims 21 to 33, wherein a driving duty ratio of the light source is adjusted for each light source. A light source that emits light periodically;
Light detection means for detecting light emitted from the light source;
A method of controlling a light source device comprising:
A determining step for determining a target brightness of the light source;
Based on the target luminance determined in the determining step and the light detection value of the light detection means, a drive duty ratio that is a ratio of the total lighting time of the light source within one cycle to one cycle of light emission of the light source Adjustment steps to adjust,
Have
In the adjustment step,
When the lighting time of one time of the light source is equal to or longer than a predetermined time, using the light detection value obtained in the acquisition period that is a period from when the light source starts lighting until the predetermined time elapses, Adjusting the drive duty ratio;
When the lighting time of the light source once is shorter than the predetermined time, the drive duty ratio is adjusted without using the light detection value obtained in the acquisition period after the light source is turned off. A method for controlling a light source device. In the adjustment step, the light source as a light detection value obtained from the timing when the light source is extinguished until the timing when the acquisition period ends when one lighting time of the light source is shorter than the predetermined time. 36. The method of controlling a light source device according to claim 35, wherein a light detection value obtained before the light is turned off is used. 37. The method of controlling a light source device according to claim 35 or 36, wherein in the adjustment step, the drive duty ratio is adjusted based on a plurality of light detection values obtained within a period. In the acquisition period, M sensor values (M is an integer of 3 or more) are acquired,
In the adjustment step,
The drive duty ratio is adjusted using m (m is an integer less than or equal to 3 and less than M) sensor values among the M sensor values.
The drive duty ratio is adjusted using m sensor values acquired immediately before the light source is turned off when a single lighting time of the light source is shorter than the predetermined time. 37. A method for controlling the light source device according to 37. The correspondence between the lighting time of the light source once and the number and time position of the light detection values used when adjusting the drive duty ratio is determined in advance.
In the adjustment step, the number of light detection values and the time position used for the adjustment of the drive duty ratio are determined based on one lighting time of the light source and the correspondence relationship. Item 38. The method of controlling the light source device according to Item 37. 40. The method of controlling a light source device according to claim 37, wherein, in the adjustment step, the drive duty ratio is adjusted based on an average value of the plurality of light detection values. The program which makes a computer perform each step of the control method of the light source device of any one of Claims 21-40.

Images