JP2019009016A - Light source device, method of controlling the same, and display device - Google Patents

Abstract

To suppress generation of color breakup in a case where a lighting time period and an unlighting time period of a light source is periodically controlled, in a light source device that comprises the light source having an optical conversion member for receiving light from a light-emitting element and emitting light with a different wavelength.SOLUTION: A light source device comprises: a first light source and a second light source each having a light-emitting element that emits light of a first color and a first optical conversion member that emits light of a second color different from the first color in response to that the light of the first color generated from the light-emitting element is emitted; and control means that periodically controls a lighting time period and an unlighting time period of the first light source in a first drive cycle, and periodically controls a lighting time period and an unlighting time period of the second light source in a second drive cycle shorter than the first drive cycle, and thereby individually and independently controls light emission of each light source.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a light source device, a control method thereof, and a display device.

Conventionally, a cold cathode fluorescent lamp (CCFL) has been used as a light source of a light source device for a liquid crystal display device. In recent years, light source devices using light emitting diodes (hereinafter referred to as LEDs) as light sources are increasing. White light sources for light source devices include those that emit white light using a yellow phosphor (YAG: Yttrium Alminium Garnet) for the blue LED and those that emit red light using red and green phosphors for the blue LED. A white light source using red and green phosphors is effective particularly when an image displayed on a liquid crystal display device is desired to have a wide color gamut. However, there are various types of red and green phosphors, and the wavelength and purity of the color excited by the excitation light are different, so it is common to select the phosphor according to the color filter characteristics of the liquid crystal display device It is.

  In a display device using a hold-type display panel such as a liquid crystal display device, when a moving image is displayed, a “moving image blur” occurs in which a moving object is visually recognized as if it is tailed. As a technique for improving the moving image blur of the liquid crystal display device, there is a technology called black insertion that causes the light source device to emit pseudo impulse light by displaying a black image between frames as shown in FIG. There is also a technique called backlight scanning in which the backlight is turned on intermittently. Backlight scanning is a technique for turning on and off LEDs sequentially for each backlight line from the upper side to the lower side of the screen, for example, when a backlight having a plurality of LEDs arranged in a matrix is turned on. A backlight line is a horizontal line of a matrix formed by a plurality of LEDs. These techniques improve the motion blur.

  Some white light sources using phosphors of a plurality of colors such as a red phosphor and a green phosphor have a difference in response time from reception of blue excitation light to fluorescence emission depending on colors. For example, there is a material in which the response time of the red phosphor is delayed by about 10 msec with respect to the response time of green. When backlight scanning is performed with a light source device using a white light source using such a phosphor, green emission starts almost simultaneously with the start of emission of the blue light source, as shown in FIG. Therefore, there is a problem that the cyan color is visible when the LED is turned on, and the red color is visually recognized because the red color is emitted when the LED is turned off.

  Conventionally, as a method for solving the problem when the response characteristics of the red and green phosphors are different, there is a technique described in Patent Document 1. This is because the afterglow of the phosphor is caused by discontinuously exciting a continuously excited light source at the end of continuous excitation, or by discontinuously exciting a continuously excited light source at the start of continuous excitation. It is intended to equalize the characteristics. Patent Document 2 discloses a method for improving the motion blur by synchronizing the black insertion of the liquid crystal display unit and the light emission time of the light source, and shortening the response time of the liquid crystal display element for a color with a long afterglow time of the light source. Have been described.

JP 2001-236034 A JP 2007-248845 A

  However, in the technique of Patent Document 1, since it is necessary to always provide a discontinuous lighting period, for example, when the light source deteriorates and the luminance decreases, the display luminance is limited. In the technique of Patent Document 2, the cell gap of the liquid crystal panel has to be designed in accordance with the light source characteristics, and the versatility is low.

  Therefore, the present invention provides a light source device including a light source having a light conversion member that receives light from a light emitting element and emits light of a different wavelength, in which color breakup occurs when the lighting period and light extinction period of the light source are controlled periodically. It aims at providing the technique which suppresses generation | occurrence | production of this.

The present invention provides a light emitting element that emits light of a first color, and a second color that is different from the first color in response to irradiation of the light of the first color emitted from the light emitting element. A first light source and a second light source each comprising a first light conversion member that emits light;
Periodically controlling the lighting period and extinguishing period of the first light source in a first driving cycle;
Control means for independently controlling the light emission of each light source by periodically controlling the lighting period and extinguishing period of the second light source in a second driving cycle shorter than the first driving cycle;
A light source device comprising:

The present invention provides a light emitting element that emits light of a first color, and a second color that is different from the first color in response to irradiation of the light of the first color emitted from the light emitting element. A method of controlling a light source device including a first light source and a second light source each including a first light conversion member that emits light,
Periodically controlling the lighting period and extinguishing period of the first light source in a first driving cycle;
Controlling the light emission of each light source independently by periodically controlling the lighting period and extinguishing period of the second light source with a second driving period shorter than the first driving period;
A control method for a light source device.

  According to the present invention, in a light source device including a light source having a light conversion member that emits light of different wavelengths in response to light from a light emitting element, color breakup in the case of periodically controlling the lighting period and extinguishing period of the light source Can be suppressed.

1 is a block diagram illustrating a schematic configuration of a light source device according to Embodiment 1. FIG. It is a figure which shows LED arrangement | positioning of the light source device of Example 1. FIG. It is a figure which shows the lighting state of the light source device of Example 1. FIG. 6 is a flowchart for explaining lighting control of the light source device according to the first embodiment. It is a figure which shows the lighting state at the time of the backlight scan of the light source device of Example 1. FIG. FIG. 6 is a block diagram illustrating a schematic configuration of a light source device according to a second embodiment. It is a figure which shows the lighting state of the light source device of Example 2. FIG. It is a figure for demonstrating the conventional backlight scan technique. It is a figure for demonstrating the color breakage which arises with LED using the fluorescent substance of multiple colors.

Example 1
Example 1 of the present invention will be described. Example 1 is an example in which the light source device of the present invention is applied to a backlight that irradiates light from the back to a liquid crystal panel of a liquid crystal display device.

With reference to FIG. 1, a schematic configuration of a light source device 100 according to the first embodiment will be described.
The light source device 100 is a backlight that irradiates the liquid crystal panel 150 of the image display device 160 with light. The liquid crystal panel 150 is a display panel that displays an image in a display area by modulating light from the light source device 100 based on an image signal. The light source device 100 includes a light source unit 101, a light source unit 102, a drive circuit unit 103, a drive circuit unit 104, a power supply unit 105, a control unit 106, a reflection unit 107, a holding unit 108, a light source block 109, and a memory 110.

The light source device 100 includes a plurality of light source blocks 109. Each light source block 109 includes a light source unit 101 and a light source unit 102. The plurality of light source blocks 109 correspond to a plurality of partial areas obtained by virtually dividing the display area of the liquid crystal panel 150. The control unit 106 independently controls the light emission of the plurality of light source blocks.
Each of the light source unit 101 and the light source unit 102 includes N (N ≧ 1) white light sources that can independently control light emission. It is assumed that the light source unit 101 includes 12 white light sources 1 and the light source unit 102 includes 12 white light sources 2.

  The characteristics of the white light source constituting the light source unit 101 and the light source unit 102 will be described. Here, it is assumed that the white light source 1 and the white light source 2 are the same white light source. The white light source includes a light emitting element that emits blue light and a phosphor that emits light of a color different from blue in response to irradiation of the blue light emitted from the light emitting element. The light emitting element is assumed to be an LED, for example. In this example, the white light source was irradiated with the green phosphor that emits green light in response to the irradiation of the blue light emitted from the light emitting element, and the blue light emitted from the light emitting element. And a red phosphor that emits red light according to the above. Note that the phosphor included in the white light source may be a phosphor that emits yellow light in response to irradiation with blue light emitted from the light emitting element. That is, it can be said that the white light source is a light source that emits white light using excitation light emitted from the light emitting element and fluorescence of a plurality of wavelengths emitted from the phosphor. Here, the blue light emitted from the light emitting element is excitation light, and the light emitted from the phosphor is fluorescence. The phosphor emits fluorescence after a predetermined response period elapses after the excitation light is irradiated. In Example 1, the response time from when the red phosphor receives blue excitation light to the emission of red fluorescence is greater than the response time from when the green phosphor receives blue excitation light to emission of the red fluorescence. long. In addition, the fluorescent substance should just be a light conversion member which emits the light of the color different from the color of excitation light according to irradiation of excitation light. For example, quantum dots may be used.

The arrangement of the light source unit 101 and the light source unit 102 will be described with reference to FIG.
In FIG. 2, in a state where the light source device 100 is assembled to the liquid crystal panel, the direction perpendicular to the screen is defined as the Z direction, and the directions parallel to the screen are defined as the X and Y directions. In FIG. 2, constituent members such as a diffusion plate and a circuit board provided in an actual light source device are omitted because they are not directly related to the description of the embodiments of the invention.

FIG. 2A is a diagram of the light source device 100 viewed from the Z direction. FIG. 2B is a view of a cross section of the light source device 100 taken along the line AA in FIG.
The four light source blocks 109 are a group of white light sources arranged in four rows physically arranged in the Y direction. The four light source blocks 109 correspond to partial areas in which the liquid crystal panel is virtually divided into four in the vertical direction. The interval between the light source blocks 109 in the Y direction is L.

  One light source block 109 includes a light source unit 101 including a row of N white light sources 1 arranged in the X direction, and a light source unit 102 including a row of N white light sources 2 arranged in the X direction. Composed. The interval in the Y direction between the white light source column of the light source unit 101 and the white light source column of the light source unit 102 constituting one light source block 109 is defined as S1. An interval in the X direction between N white light sources constituting each of the light source unit 101 and the light source unit 102 is S2.

The drive circuit unit 103, the drive circuit unit 104, and the control unit 106 are control units for independently controlling light emission of each light source unit. Specifically, the drive circuit unit 103 and the control unit 106 periodically control the light emission of the light source unit 101 with the drive cycle λ1. In addition, the drive circuit unit 104 and the control unit 106 periodically control the light emission of the light source unit 102 with the drive cycle λ2. The light emission of the light source unit 101 and the light source unit 102 is controlled by controlling the amount of current flowing through each light source unit for each drive cycle of each light source unit by PWM (Pulse Width Modulation) control. Thereby, in Example 1, the light source part 101 and the light source part 102 are intermittently light-emitted independently. The light emission of each light source part can also control the amount of current flowing through each light source part by controlling the current value. Further, the light emission of each light source unit can control the amount of current flowing through each light source unit by a combination of current value control and PWM control. In this embodiment, for simplicity, a case will be described in which the current value flowing through each light source unit is constant, and the amount of current flowing through each light source unit is controlled by PWM control.

The control unit 106 determines control parameters for controlling the light emission of each light source unit, and controls each drive circuit unit. Specifically, the control unit 106 controls the drive circuit unit 103 and the drive circuit unit 104 to control the current value of the constant current circuit, the PWM value of the PWM control, the PWM cycle, and the like. The control unit 106 is configured by a CPU or FPGA (Field Programmable Gate Array),
By executing the program read from the memory 110, various controls described later are realized.

  The PWM cycle is a drive cycle of PWM control of each light source unit. The PWM frequency is a PWM control drive frequency of each light source unit. The PWM period is the reciprocal of the PWM frequency. The control unit 106 individually determines the PWM frequency of each light source unit. The control unit 106 controls each drive circuit unit so that the light source unit 102 is controlled with a PWM cycle λ2 shorter than the PWM cycle λ1 of the light source unit 101. That is, the control unit 106 controls each drive circuit unit so that the light source unit 102 is controlled at a PWM frequency f2 higher than the PWM frequency f1 of the light source unit 101. For example, assume that the PWM frequency f1 is 60 Hz and the PWM frequency f2 is 300 Hz. In order to synchronize the light emission of the light source unit at regular intervals, the PWM frequency f2 is desirably an integer multiple of the PWM frequency f1. In other words, it can be said that the PWM cycle λ1 is desirably an integer multiple of the PWM cycle λ2.

The PWM value is a value indicating a duty ratio that is a ratio of a lighting period to a PWM cycle of each light source unit. The PWM value corresponds to the light emission amount of each light source unit. Here, the PWM period is a unit period for periodically controlling the lighting period and the extinguishing period. The PWM value is represented by a value of 4096 levels. The PWM value 0 corresponds to the case where the luminance of the light source unit is minimum (lights off). Here, the case where the duty ratio is 0% is set to the PWM value 0. The PWM value 4095 corresponds to the case where the luminance of the light source unit is maximum. Here, the case where the duty ratio is 100% is set as the PWM value 4095.
The control unit 106 determines the PWM value according to the target luminance of each light source unit. For example, it is assumed that the control unit 106 determines the target luminance in accordance with the brightness of the image displayed in the partial area corresponding to each light source block 109.

  The light source unit is turned on during the lighting period having a length corresponding to the PWM value in the PWM cycle, and is turned off during the other light-out periods. For example, when the PWM value is 0, the light source unit is turned off over the entire PWM period. When the PWM value is 4095, the light source unit is turned on over the entire PWM period. When the PWM value is any other value, a part of the PWM period is a lighting period and the remaining part is a light extinction period. In each PWM cycle, a light extinction period may be provided after the lighting period, or a lighting period may be provided after the extinction period.

In the input image signal, a vertical synchronization signal (Vsync signal) which is a synchronization signal in the vertical direction of the liquid crystal panel is set as a timing at which one frame starts. The start timing of the PWM cycle is determined based on the vertical synchronization signal. As described above, in the PWM cycle, the lighting period may be provided first, or the extinguishing period may be provided first. When the PWM period starts from the lighting period, a lighting period corresponding to the duty ratio is provided from the start timing of the PWM period, and the remaining period of the PWM period after the lighting period has elapsed is set as the extinguishing period. When the PWM cycle starts from the extinguishing period, the lighting period is provided according to the duty ratio by going back from the end timing of the PWM period, and the other is set as the extinguishing period. In the first embodiment, the case where the PWM period starts from the extinguishing period will be described as an example.

  The drive circuit unit 103 and the drive circuit unit 104 are provided for each light source block 109, and the PWM value can be set independently for each light source block. Thereby, the luminance can be controlled independently for each light source block 109. The drive circuit unit 103 and the drive circuit unit 104 are each configured by a constant current circuit and a PWM drive circuit. The drive circuit unit 103 and the drive circuit unit 104 periodically control the light emission of each light source unit based on the control parameter set by the control unit 106.

  The drive circuit unit 103 is a drive circuit that drives the N white light sources 1 constituting the light source unit 101. The drive circuit unit 103 drives the light source unit 101 based on the PWM cycle λ1 and the PWM value of the light source unit 101 determined by the control unit 106. As described above, it is assumed that the PWM frequency f1 is 60 Hz. When the frame frequency of the input image signal is 60 Hz, the length of the PWM cycle λ1 of the drive circuit unit 103 is equal to the length of one frame period. The drive circuit unit 103 controls the brightness of the light source unit 101 by controlling the lighting period of the white light source 1 according to the PWM value with reference to the time obtained by dividing 1/60 seconds into 4095.

  The drive circuit unit 104 is a drive circuit that drives the N white light sources 2 constituting the light source unit 102. The circuit configuration is the same as that of the drive circuit unit 103. As described above, the PWM frequency f2 of the drive circuit unit 104 is assumed to be 300 Hz. That is, the driving cycle λ2 of the light source unit 102 is shorter than the driving cycle λ1 of the light source unit 101.

  The power supply unit 105 is a power supply circuit that supplies power necessary for lighting the light source unit 101 and the light source unit 102. In Example 1, since twelve white light sources are connected in series to each of the light source unit 101 and the light source unit 102, the power source unit 105 has a voltage equal to or higher than a voltage obtained by multiplying the voltage drop value for one white light source by 12 times. Output.

  The reflection unit 107 is provided to reflect white light emitted from the light source unit 101 and the light source unit 102 and to irradiate the liquid crystal panel 150 efficiently.

  The holding unit 108 holds the substrate and the reflection unit 107 that fix the light source unit 101 and the light source unit 102. The side wall of the holding unit 108 is shaped so that uneven display luminance of the liquid crystal panel 150 is suppressed.

  The memory 110 is a storage device that stores data input from the outside and outputs the stored data to the outside in response to a request. The memory 110 stores a program for causing a CPU constituting the control unit 106 to execute various controls described later.

  The characteristic point of the light source device 100 according to the first embodiment is that one light source block 109 includes a plurality of light source units that can be driven by PWM signals having different PWM frequencies. For example, the drive circuit unit 103 is configured to drive the light source unit 101 with a 60 Hz PWM signal, and the drive circuit unit 104 is configured to drive the light source unit 102 with a 300 Hz PWM signal. Of course, the drive circuit unit 103 and the drive circuit unit 104 can also drive the light source unit 101 and the light source unit 102 with PWM signals having the same PWM frequency, respectively.

FIG. 3 is a diagram illustrating an example of a change in luminance of the light source block 109 when the light source unit 101 and the light source unit 102 are controlled to emit light with PWM signals having different PWM frequencies. FIG. 3 shows the liquid crystal panel 1
50 shows a change in the transmittance of the liquid crystal panel 150 and a change in the luminance of each light source unit in the case of performing a backlight scan for controlling turning on and off of the light source device 100 in synchronization with the image signal input to 50.

  FIG. 3A shows a vertical synchronization signal of the input image signal. In FIG. 3, the nth vertical synchronization signal is represented by Vsync (n). FIG. 3B shows a change in transmittance of the liquid crystal panel 150. The example of FIG. 3B shows a change in transmittance of the liquid crystal panel 150 when a white image is input by Vsync (1) and a black image is input by Vsync (3). 3C shows a change in luminance of the light source unit 101, and FIG. 3D shows a change in luminance of the light source unit 102. FIG. FIG. 3E shows a change in luminance of the light source block 109 realized by combining light from the light source unit 101 and the light source unit 102.

  In the example of FIG. 3, it is assumed that the duty ratios of the light source unit 101 and the light source unit 102 are both 50% (PWM value 2048).

  As shown in FIG. 3C, the lighting period of the light source unit 101 in the Vsync (1) period is a period corresponding to a duty ratio of 50% (PWM period (1 / (1)) with the end of the Vsync (1) period as a reference. 60%). The end of the period of Vsync (1) is also the rise of Vsync (2). Since the PWM cycle of the light source unit 101 is the same as the frame cycle, the PWM cycle composed of such a lighting period and other extinguishing periods is one time, and the rising of Vsync (2) is the end of the lighting period. Is set as follows.

  As shown in FIG. 3D, the lighting period of the light source unit 102 in the period of Vsync (1) is a period (PWM period (1/1) corresponding to a duty ratio of 50% with reference to the end of the period of Vsync (1). 50% of 300 seconds). The end of the period of Vsync (1) is also the rise of Vsync (2). Since the PWM cycle of the light source unit 101 is 1/5 of the frame cycle, the PWM cycle composed of such a lighting period and other extinguishing periods is five times, and the rise of Vsync (2) is the end of the lighting period. Is set to be

  As shown in FIG. 3C, in the luminance change of the light source unit 101, mainly during the period from the timing when the drive circuit unit 103 turns off the light source unit 101 (time t1) to the next timing when it is turned on (time t2). There is a lighting period due to the fluorescence of the red phosphor. During the red lighting period, as shown in FIG. 3D, the light source unit 102 is repeatedly turned on and off in a short cycle. That is, the light emission of the light source unit 101 and the light source unit 102 is controlled so that at least one lighting period of the light source unit 102 is included in the extinguishing period of the light source unit 101. In the first embodiment, at least one lighting period of the light source unit 102 is included in a period corresponding to a response time from the start of the extinguishing period of the light source unit 101 until the red phosphor emits fluorescence after receiving the excitation light. It is trying to be. That is, in the first embodiment, at least one lighting period of the light source unit 102 is included in a period corresponding to the longer response time of the fluorescence response times of a plurality of wavelengths. By such control, as shown in FIG. 3E, in the luminance change of the light source block 109, red light by the red phosphor of the light source unit 101 and light of the light source unit 102 are combined, thereby The red light component of the phosphor is less visible. Therefore, occurrence of color breakup can be suppressed.

  Next, lighting control of the light source device 100 according to the first embodiment will be described based on the flowchart of FIG. The processing of each step in this flowchart is executed by the control unit 106.

  In step S <b> 100, the control unit 106 starts lighting control of the light source device 100. The lighting control is started when a power-on instruction is input to the liquid crystal display device including the light source device 100, or when an instruction is input to return the liquid crystal display device from a light-off state to a display state by a power saving mode or the like.

  In step S101, the control unit 106 inputs an image signal from the outside. For example, the image signal is transferred from the image signal input unit provided in the liquid crystal display device including the light source device 100 to the control unit 106 of the light source device 100.

  In step S102, the control unit 106 determines whether the input image signal is a moving image or a still image. If the input image signal is a still image, the process proceeds to step S103. If the input image signal is a moving image, the process proceeds to step S104.

  In step S103, the control unit 106 instructs the drive circuit unit 103 and the drive circuit unit 104 to turn on the light source unit 101 and the light source unit 102 with PWM signals having the same PWM frequency. Here, the same PWM frequency is set to 300 Hz. That is, in step S103, the control unit 106 sets both the PWM frequency f1 of the drive circuit unit 103 and the PWM frequency f2 of the drive circuit unit 104 to 300 Hz.

  In step S <b> 104, the control unit 106 instructs the drive circuit unit 103 and the drive circuit unit 104 so that the PWM frequency f <b> 2 of the drive circuit unit 104 is higher than the PWM frequency f <b> 1 of the drive circuit unit 103. Here, the PWM frequency f1 is set to 60 Hz in accordance with the vertical scanning frequency (60 Hz) of the liquid crystal display device. The reason for setting in this way is that when the image signal is a moving image, backlight scan control is performed to suppress motion blur. When performing the backlight scan control, the effect of suppressing the motion blur is enhanced by matching the PWM frequency f1 of the light source unit 101 with the vertical scanning frequency of the liquid crystal display device. Further, the PWM frequency f2 is set to a frequency higher than the PWM frequency f1 (here, 60 Hz), here, 300 Hz. By making the PWM frequency f2 higher than the PWM frequency f1, as described with reference to FIG. 3, the white light of the light source unit 102 in which the red light of the red phosphor of the light source unit 101 driven at a low frequency is driven at a high frequency. Combined with light, it becomes difficult to see.

  In step S105, the control unit 106 turns on the light source unit 101 and the light source unit 102. The control unit 106 instructs the drive circuit unit 103 and the drive circuit unit 104 with the PWM frequency determined in step S103 or step S104. The drive circuit unit 103 and the drive circuit unit 104 drive the light source unit 101 and the light source unit 102 with the instructed PWM frequency, so that the light source unit 101 and the light source unit 102 are turned on.

  In step S106, the control unit 106 determines whether to end the lighting control of the light source device 100. When the power-off instruction is input to the liquid crystal display device including the light source device 100 or when the input of the image signal to the liquid crystal display device is stopped, the control unit 106 determines that the lighting control is finished. When the lighting control is not terminated, the control unit 106 repeats the processing from step S102 to step S105.

  In step S107, the control unit 106 ends the lighting control of the light source device 100. As described above, in the first embodiment, when the input image signal is a moving image, the control unit 106 emits light from the light source unit 101 and the light source unit 102 in the first driving cycle and the second driving cycle that are different from each other. Control periodically. When the input image signal is a still image, the control unit 106 periodically controls light emission of the light source unit 101 and the light source unit 102 with the same first drive cycle and second drive cycle.

  FIG. 5 shows an example of a change in luminance of each light source block 109 of the light source device 100 when performing a backlight scan when a moving image is displayed on the liquid crystal display device including the light source device 100 of the first embodiment. FIG. 5A shows a vertical synchronization signal of the input image signal. FIGS. 5B to 5E show changes in luminance of the light source blocks 109 in the first to fourth rows in FIG. 2, respectively.

  As shown in FIG. 5 (B) to FIG. 5 (E), from the light source block 109 in the first row to the light source block 109 in the fourth row, every 4.17 msec obtained by dividing one period of the vertical synchronizing signal into four parts, Light up sequentially. As described above, the moving image blur of the liquid crystal display device can be suppressed by performing the backlight scan in which the plurality of light source blocks are sequentially turned on in accordance with the progress of the vertical scanning of the liquid crystal display device. In the luminance change of the light source block 109 in each row, as described with reference to FIG. 3E, the light source block 109 is configured by a plurality of light source units driven at different PWM frequencies, so that the response speed of the phosphor varies. This makes it difficult to visually recognize red and cyan light components.

  According to the first embodiment, when a light source device including a white light source that emits white light using fluorescence of a plurality of wavelengths emitted by a red phosphor and a green phosphor having different excitation characteristics is intermittently emitted by backlight scanning. Color breakup can be suppressed.

(Example 2)
A second embodiment of the present invention will be described. The second embodiment further suppresses the color breakup by delaying the lighting timing of the light source unit 102 with a high PWM frequency by the response time of the red phosphor of the white light source with respect to the lighting timing of the light source unit 101. This is an example of this.

With reference to FIG. 6, a schematic configuration of the light source device 200 according to the second embodiment will be described.
The light source device 200 is a backlight that irradiates the liquid crystal panel 250 of the image display device 260 with light. The liquid crystal panel 250 is a display panel that displays an image by modulating light from the light source device 200 based on an image signal. The light source device 200 includes a light source unit 201, a light source unit 202, a drive circuit unit 203, a drive circuit unit 204, a power supply unit 205, a control unit 206, a light source block 209, a memory 210, and a delay circuit unit 211.

  The light source unit 201, the light source unit 202, the drive circuit unit 203, the drive circuit unit 204, the power supply unit 205, the control unit 206, the light source block 209, and the memory 210 are the same as the components having the same names in the first embodiment. In addition, components corresponding to the reflection unit 107 and the holding unit 108 of the first embodiment are not shown, but are also provided in the light source device 200 of the second embodiment. The difference between the first embodiment and the second embodiment is that a delay circuit section 211 is provided between the drive circuit section 204 and the control section 206.

  The delay circuit unit 211 is a circuit that delays the lighting start timing of the light source unit 202 from the light source unit 201 in accordance with the response speed of the red phosphor of the white light source used for the light source unit 201 and the light source unit 202. That is, in the color breakup suppression control, the light emission period start timing of the light source unit 202 with respect to the light emission period start timing is the response time from when the red phosphor receives excitation light until it emits fluorescence. Delays according to the time. In Example 2, the fluorescence is delayed by a time corresponding to the longer response time of the fluorescence response times of a plurality of wavelengths. In the second embodiment, assuming that the response time of the red phosphor is delayed by about 10 msec from the green phosphor, the lighting start of the light source unit 202 is also delayed by 10 msec with respect to the light source unit 201.

  FIG. 7 illustrates an example of a change in luminance of the light source block 209 when the light source unit 201 and the light source unit 202 are controlled to emit light with PWM signals having different PWM frequencies, and the lighting start timing of the light source unit 202 is delayed with respect to the light source unit 201. FIG.

FIG. 7A shows a vertical synchronization signal of the input image signal. FIG. 7B shows a change in transmittance of the liquid crystal panel 250. The example of FIG. 7B shows a change in the transmittance of the liquid crystal when a white image is input by Vsync (1) and a black image is input by Vsync (3). FIG. 7C shows a change in luminance of the light source unit 201, and FIG. 7D shows a change in luminance of the light source unit 202. FIG. 7E shows a change in luminance of the light source block 109 realized by combining light from the light source unit 101 and the light source unit 102.

  As shown in FIG. 7C, the response of the red phosphor of the light source unit 201 is delayed and the light source is turned on as shown in FIG. The unit 202 repeats turning on and off in a short cycle. Therefore, as shown in FIG. 7E, in the luminance change of the light source block 209, the red light component due to the red phosphor of the light source unit 201 is more difficult to be visually recognized. Therefore, the occurrence of color breakup can be more reliably suppressed.

  According to the second embodiment, when a light source device including a white light source that emits white light using a plurality of wavelengths of fluorescence emitted by a red phosphor and a green phosphor having different excitation characteristics is intermittently emitted by backlight scanning. Color breakage can be further suppressed than in Example 1.

(Modification)
Each said Example is an example for implementing this invention, and this invention is not limited to each said Example. Each of the above embodiments can be variously modified and combined within the scope of the present invention.

  In the above embodiment, each of the light source unit 101 and the light source unit 102 includes a blue LED as a light emitting element that emits light of the first color. In addition, a red phosphor is provided as a first light conversion member that emits a second color different from the first color in response to the irradiation of the first color light emitted from the light emitting element. Further, a blue phosphor as a second light conversion member that emits light of a third color different from the first color and the second color in response to irradiation with the light of the first color emitted from the light emitting element Is provided. The first light conversion member emits the second color light (red) after the first period after the first color light (blue) is irradiated to the first light conversion member, and the second light. The conversion member emits light of the third color (green) after the second period after the first color of light (blue) is applied to the second light conversion member. In the above-described embodiment, the embodiment has been described in which the light source device including the light source unit 101 and the light source unit 102 as the first light source and the second light source performs control for suppressing color breakup. That is, the lighting period and extinguishing period of the first light source are periodically controlled by the first driving period λ1, and the lighting period and extinguishing period of the second light source are controlled by the second driving period λ2 shorter than the first driving period λ1. The example which controls light emission of each light source independently by controlling periodically was demonstrated. Specifically, in the first embodiment, the first light source is turned off within a period corresponding to the longer one of the first period and the second period (the first period in the first embodiment) from the start of the extinguishing period of the first light source. The example in which the light emission of the first light source and the second light source is controlled so that at least one lighting period of the two light sources is included has been described. Further, in the second embodiment, the start timing of the second drive cycle λ2 is longer of the first period and the second period than the start timing of the first drive cycle λ1 (the first period in the second embodiment). The example which delays only the time according to) was demonstrated.

However, the present invention is not limited to this example. A light source device in which the first light source and the second light source each include a light emitting element and a first light conversion member is also included in the present invention. For example, a blue LED is provided as a light emitting element that emits light of the first color, and a second color that is different from the first color is emitted in response to irradiation of the first color light emitted from the light emitting element. A light source device including a first light source and a second light source each including a yellow phosphor as the first light conversion member is also included. In this case, the first light conversion member emits the second color light (yellow) after the first period after the first color light (blue) is irradiated to the first light conversion member. And According to the present invention, in the light source device including the first light source and the second light source, it is possible to perform control for suppressing color breakup. That is, the lighting period and extinguishing period of the first light source are periodically controlled with the first driving period, and the lighting period and extinguishing period of the second light source are periodically controlled with the second driving period shorter than the first driving period. By doing so, the light emission of each light source may be controlled independently. Specifically, the first light source and the second light source emit light so that at least one lighting period of the second light source is included in a period corresponding to the first period from the start of the extinguishing period of the first light source. It is good to control. Further, similarly to the second embodiment, the start timing of the second drive cycle may be delayed by the time corresponding to the first period with respect to the start timing of the first drive cycle. By performing such control, it can be suppressed that the light of the second color is visually recognized in the first period after the light emitting element is turned off, and color breakup can be suppressed.

  In the above embodiment, the example in which the light source device of the present invention is applied to the backlight of the liquid crystal display device has been described, but the light source device to which the present invention is applicable is not limited thereto. The light source device according to the present invention is applicable to all light source devices that supply light to a transmissive display panel that displays an image by modulating light according to an image signal and adjusting the transmittance. In addition, a display device including such a light source device and a display panel is also included in the present invention. For example, the present invention can be applied to an illumination device such as an advertisement display device or a sign display device, a light source device used in them, a street lamp, indoor lighting, or microscope lighting.

  In the above embodiment, the configuration in which the light source includes one light emitting element (LED) has been described as an example. However, the light source may include a light emitting element group including a plurality of light emitting elements. In that case, the light emitting elements belonging to the same light emitting element group are driven by the same control signal.

  In the said Example, although the light source was demonstrated to the structure provided with LED which irradiates light to the 1st light conversion member or the 2nd light conversion member as an example, it irradiates light to the 1st light conversion member or the 2nd light conversion member. Configurations including other light emitting elements and fluorescent lamps are also included in the present invention.

  In the above embodiment, the case where the number of light source blocks is four has been described as an example, but the number of light source blocks is not limited thereto. Further, the method of virtually dividing the backlight by the light source block and the method of dividing by the virtual partial area of the display area of the display panel are not limited to the above embodiment. For example, various division methods such as vertical 10 blocks × horizontal 2 blocks may be used.

  In the said Example, although the example of the white light source which has blue LED, a green fluorescent substance, and a red fluorescent substance was demonstrated as a white light source which comprises each of the several light source part which comprises each light source block, a white light source The configuration is not limited to this. The wavelength of excitation light, the wavelength of fluorescence, the type of wavelength, the difference in response time depending on the wavelength, and the like can be variously changed within the scope of the present invention.

  In the above-described embodiment, the control unit 106 is configured by a CPU or FPGA, and various controls executed by the control unit 106 are realized by the CPU or FPGA reading a program from the memory 110 and executing the program. However, the method for executing the control method of the present invention is not limited to this.

The PWM control in the above embodiment is an example and is not limited to this. For example, the case where the PWM cycle λ1 of the drive circuit unit 103 is equal to the frame cycle has been described as an example, but the PWM cycle and the frame cycle may be different. Moreover, although the case where the duty ratio is expressed by a PWM value of 4096 levels has been described, the way of expressing the duty ratio is not limited to this. It can be arbitrarily set whether the PWM cycle starts in the light-off period or the light-up period. Further, although an example has been described in which the PWM frequency of the drive circuit unit 103 and the drive circuit unit 104 is both set to 300 Hz when displaying a still image, this PWM frequency is an example and is not limited to this. The PWM frequency may be appropriately set according to flicker (screen flicker) characteristics and the vertical scanning frequency of the liquid crystal display device. Further, in the case of displaying a moving image, the example in which the PWM frequency f2 (300 Hz) of the drive circuit unit 104 is set to five times the PWM frequency f1 (60 Hz) of the drive circuit unit 103 has been described, but this is also an example. The PWM frequency f2 of the drive circuit unit 104 may not be an integer multiple of the PWM frequency f1 of the drive circuit unit 103. The PWM frequency of the drive circuit unit may be appropriately set according to the response time of the phosphor used for the white light source and the visual characteristics by backlight scanning. Further, in the above embodiment, the ratio of the lighting period of the light source unit 101 to the driving cycle λ1 of the light source unit 101 and the ratio of the lighting period of the light source unit 102 to the driving cycle λ2 of the light source unit 102 are the same. The example which controls the lighting period and light extinction period of each light source was demonstrated. Further, an example has been described in which each light source is controlled so that the luminance of light emitted from the light source unit 102 is lower than the luminance of light emitted from the light source unit 101. However, the present invention is not limited to these. If the target luminance can be achieved by the light emission of the light source unit 101 and the light source unit 102, the ratio and luminance of the lighting periods of the light source unit 101 and the light source unit 102 can be set as appropriate.

  In the above embodiment, an example in which the PWM frequencies of the light source unit 101 and the light source unit 102 are the same when displaying a still image has been described. However, there are various other controls for controlling the light source device when displaying a still image. Conceivable. For example, the lighting time of the light source unit 101 and the light source unit 102 may be controlled to be as long as possible. Since the red light component due to the response delay of the phosphor is visually recognized during the extinguishing period by PWM control, if the extinguishing period is shortened, the red light component becomes difficult to be visually recognized and color breakage can be suppressed. When a still image is displayed, it is not necessary to perform a backlight scan for suppressing moving image blur, and thus it is possible to perform control to shorten the extinguishing period as much as possible.

  When displaying a still image, only one of the light source unit 101 and the light source unit 102 may be turned on. By doing so, the PWM value of the light source unit to be turned on can be increased, so that color breakup can be suppressed. When it is necessary to lower the display brightness when displaying a still image, it is necessary to reduce the PWM value. However, the light source unit is turned off by turning on only one of the light source unit 101 and the light source unit 102. Since it can be shortened, the red light component is hardly visually recognized during the extinguishing period.

  Also, when displaying a still image, the PWM frequency of the light source unit 101 and the light source unit 102 are set to different frequencies as in the case of displaying a moving image, and the PWM value of the light source unit 101 and the PWM value of the light source unit 102 are set. It may be a different value.

  Further, when displaying a still image, current control and PWM control may be performed on the light source unit 101 and the light source unit 102. For example, the current value is adjusted so that the upper limit of the PWM value of the light source unit 101 can be 4095. Further, only when the light source unit 101 starts to be turned on and off, the light source unit 102 can be turned on to make it difficult to visually recognize cyan and red.

(Other examples)
The present invention supplies a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in a computer of the system or apparatus read and execute the program This process can be realized. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

100: light source device, 101: light source unit, 102: light source unit, 103: drive circuit unit, 104: drive circuit unit, 106: control unit

Claims (16)

A light emitting element that emits light of a first color, and a second light that emits light of a second color different from the first color in response to irradiation of the light of the first color emitted from the light emitting element. A first light source and a second light source each comprising a single light conversion member;
Periodically controlling the lighting period and extinguishing period of the first light source in a first driving cycle;
Control means for independently controlling the light emission of each light source by periodically controlling the lighting period and extinguishing period of the second light source in a second driving cycle shorter than the first driving cycle;
A light source device comprising: The control means includes
2. The light emission of the first light source and the second light source is controlled so that at least one lighting period of the second light source is included in a lighting period of the first light source. Light source device. The first light conversion member emits light of the second color after a first period after the first color light is irradiated on the first light conversion member,
The control means includes the first light source and the first light source so that at least one lighting period of the second light source is included in a period according to the first period from the start of the extinguishing period of the first light source. The light source device according to claim 1, wherein the light emission of the second light source is controlled. The first light conversion member emits light of the second color after a first period after the first color light is irradiated on the first light conversion member,
4. The control unit according to claim 1, wherein the control unit delays the start timing of the second drive cycle by a time corresponding to the first period with respect to the start timing of the first drive cycle. The light source device according to 1. The first color light is blue light,
5. The light source device according to claim 1, wherein the second color light is yellow light. 6. The first light source and the second light source are different from the first color and the second color, respectively, in response to the irradiation of the first color light emitted from the light emitting element. A second light conversion member that emits light of three colors;
The first light conversion member emits the light of the second color after the first period after the first color light is irradiated on the first light conversion member, and the second light conversion The member emits the light of the third color after a second period different from the first period after the light of the first color is irradiated on the second light conversion member. ,
The control means includes at least one lighting period of the second light source within a period corresponding to a longer one of the first period and the second period from the start of the extinguishing period of the first light source. The light source device according to claim 1, wherein the light source device controls light emission of the first light source and the second light source so as to be included. The first light source and the second light source are different from the first color and the second color, respectively, in response to the irradiation of the first color light emitted from the light emitting element. A second light conversion member that emits light of three colors;
The first light conversion member emits the light of the second color after the first period after the first color light is irradiated on the first light conversion member, and the second light conversion The member emits the light of the third color after a second period different from the first period after the light of the first color is irradiated on the second light conversion member. ,
The control means delays the start timing of the second drive cycle with respect to the start timing of the first drive cycle by a time corresponding to the longer of the first period and the second period. The light source device according to claim 1 or 2.   The first color light is blue light, the second color light is red light, and the third color light is green light. The light source device according to claim 6 or 7.   9. The light source device according to claim 1, wherein the first driving cycle is an integral multiple of the second driving cycle.   10. The light source device according to claim 1, wherein the luminance of light emitted from the second light source is lower than the luminance of light emitted from the first light source.   The controller is configured to turn on each light source so that the ratio of the lighting period of the first light source to the first driving period is the same as the ratio of the lighting period of the second light source to the second driving period. The light source device according to claim 1, wherein a light extinction period is controlled. A display panel that displays an image in a display area by modulating light based on an image signal;
A display device comprising the light source device according to claim 1 as a backlight for irradiating the display panel with light. The light source device includes a plurality of light source blocks corresponding to a plurality of partial areas obtained by virtually dividing the display area,
Each of the plurality of light source blocks has the first light source and the second light source,
The display device according to claim 12, wherein the control unit independently controls light emission of the plurality of light source blocks.   The control means includes a ratio of a lighting period to the first driving cycle of the first light source of each light source block according to the brightness of an image displayed in the partial region corresponding to each light source block, and the second The display device according to claim 13, wherein a ratio of a lighting period with respect to the second driving cycle of the light source is determined. The control means includes
When the image signal is a moving image, the light emission of each light source is periodically controlled in the first drive cycle and the second drive cycle different from each other,
15. The light emission of each light source is periodically controlled in the same first driving cycle and second driving cycle when the image signal is a still image. The display device according to claim 1. A light emitting element that emits light of a first color, and a second light that emits light of a second color different from the first color in response to irradiation of the light of the first color emitted from the light emitting element. A method of controlling a light source device comprising a first light source and a second light source each comprising a single light conversion member,
Periodically controlling the lighting period and extinguishing period of the first light source in a first driving cycle;
Controlling the light emission of each light source independently by periodically controlling the lighting period and extinguishing period of the second light source with a second driving period shorter than the first driving period;
A control method for a light source device, comprising:

Images