JP2011204702A - Backlight system, liquid crystal display device, and backlight adjusting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a backlight system capable of simply and surely adjusting light-emission of each LED and attaining a suitable white balance that does not have color shifts, and to provide a liquid crystal display device, and a backlight adjustment method.SOLUTION: In a structure wherein one photosensor is arranged in the vicinity of the center of a short side of LED sections, having a plurality of rows of LED units where a plurality of LEDs are arranged, calibration of the photosensor is performed at an optimal state by adjusting the gain of the photosensor on the basis of gain information established, in response to positions of the LED units, in advance. Furthermore, in the structure wherein the photosensor is arranged on each LED unit, white balance of the other LED units are adjusted, on the basis of a current value to each LED unit established, in advance, so as to make output of each photosensor approximately equal and information for determining while balance of one LED unit.

Description

  The present invention relates to a backlight system, a liquid crystal display device including the backlight system, and a backlight adjustment method.

  Liquid crystal display devices are used in a wide range of fields such as OA devices, AV devices, and portable terminal devices because of their thinness, light weight, and low power consumption. This liquid crystal display device includes a backlight light source on the back side of the liquid crystal display panel, and displays by controlling the amount of light transmitted from the backlight light source with liquid crystal. Conventionally, a fluorescent tube has been used as the backlight light source. However, in order to turn on the fluorescent tube, a peripheral circuit such as an inverter circuit is necessary, and noise is generated from the inverter circuit. An LED (Light Emitting Diode) is used.

  Here, when displaying a moving image using a liquid crystal display device, there is a problem that an afterimage is detected in a portion where the image has moved due to the response speed of the liquid crystal itself, and the display quality is deteriorated, and this afterimage is prevented. Therefore, a method is used in which the LED group is turned off at least once per field period to darken the screen. In this method, the LED group is turned off all at once during the period during which any RGB image is written, and the corresponding LED group is turned on while any RGB image is written and held. This method is a method of repeating the operation, but this method has a problem that the light emission period of the LED group in the field period is shortened, so that the display becomes darker than that of the steady illumination.

  In order to solve the above problem, a method of sequentially turning off a part of the LED group has been proposed. In this method, the liquid crystal panel is divided into a plurality of regions, and the LED group is also divided into a plurality of regions corresponding to the liquid crystal panel. It is a method of turning off the LED group area corresponding to the response transition period area, and afterimages can be prevented by turning off the LED group in the response transition period area, and bright display by turning on the LED groups in other areas Can be obtained.

  However, since the light emission characteristics and light emission amount of the LED are not constant and change over time, the method of sequentially turning off a part of the LED group has a low luminance during the period when the LED with weak light emission is on. If the light emitted from any of the RGB LEDs is weak, the white balance is shifted, and the desired luminance, luminance uniformity and white balance cannot be obtained visually, and stable display cannot be obtained.

  Therefore, for example, in Patent Document 1 below, as shown in FIG. 7, the light emission area of the backlight light source is divided into a plurality of divided areas, and lighting is performed except for one divided area among the plurality of light emitting areas. In addition, the backlight control unit 106 that performs dimming control of the backlight light source and the backlight light source for the backlight 100 that is sequentially selected from the plurality of divided regions and is turned off. And a photosensor 107 that detects the amount of light emitted from the photosensor 107, and the backlight control unit 106 discloses a liquid crystal display device that controls the amount of light emitted from each of the plurality of divided regions based on the output from the photosensor 107. .

Japanese Patent Laying-Open No. 2005-208486 (page 5-7, FIG. 1)

  However, in the backlight 100 described in Patent Literature 1, for the feedback control, the light amount of the backlight light source must be continuously detected by the photosensor 107 during all the divided periods. There is a problem that the scale of the backlight control unit 106 becomes large because a calculation for matching the brightness and white balance of all the areas must be performed. In addition, since the control becomes complicated, there is a possibility that the backlight 100 may not be able to cope with an increase in size and a large number of divisions.

  In addition, since the distance from the photo sensor 107 differs depending on the LED groups 101 to 104, the amount of light incident on the photo sensor 107 differs. As a result, further correction is necessary to match the luminance and chromaticity of the LED groups 101 to 104. On the other hand, when a light guide or a condenser is used to make the amount of light incident on the photosensor 107 constant, there is a problem that the cost increases accordingly.

  The present invention has been made in view of the above problems, and its main purpose is to make it possible to easily and reliably adjust the light emission of each LED, and to realize a good white balance without color misregistration. A light system, a liquid crystal display device including the backlight system, and a backlight adjustment method are provided.

  In order to achieve the above object, the present invention provides an LED unit including a plurality of columns of LED units in which LEDs of a plurality of emission colors are arranged, a backlight control unit that outputs an LED drive signal based on a timing signal, and In a backlight system including at least an LED driver unit that sequentially turns on or off each LED unit based on an LED drive signal, the amount of light of each LED unit is near the longitudinal end of each LED unit. The plurality of photosensor units are adjusted so that substantially the same output can be obtained with respect to the same light amount, and the backlight control unit has an output of each of the photosensor units. In order to make the LED units substantially equal to each other, the current value passed through each of the LED units is stored, Based information to determine the white balance of an LED unit and to said current value, in which the white balance of the other of the LED unit is adjusted.

  In the present invention, each of the LED units is divided into a plurality of blocks, and can be controlled to be turned on or off for each block. The photosensor unit includes gain correction information according to the position of each of the blocks. Can be stored, and the gain of the photosensor unit can be adjusted based on the gain correction information corresponding to the block to be adjusted.

  The liquid crystal display device of the present invention includes at least the backlight system according to any one of the above and a liquid crystal panel in which a liquid crystal is sandwiched between a pair of substrates, and is synchronized with the display of the liquid crystal panel. The LED unit is controlled to be turned on or off.

  In addition, the present invention is based on an LED unit including a plurality of rows of LED units in which LEDs of a plurality of emission colors are arranged, a backlight control unit that outputs an LED drive signal based on a timing signal, and the LED drive signal. An LED driver for sequentially turning on or off each of the LED units, and a plurality of photosensors for detecting the light amount of each of the LED units, provided in the vicinity of the longitudinal end of each of the LED units. A backlight adjustment method in a backlight system comprising at least a first step of adjusting a plurality of the photosensor units so as to obtain a substantially equal output with respect to the same light amount, and the backlight control unit, In order to make the output of each of the photo sensor sections substantially equal, Based on the second step of storing the current value, the third step of adjusting the white balance of the predetermined LED unit, the information for determining the white balance of the LED unit, and the current value, the other And a fourth step of adjusting the white balance of the LED unit. Each of the LED units is divided into a plurality of blocks, and lighting or extinguishing can be controlled for each block. In this step, gain correction information corresponding to the position of each block is stored in the photo sensor unit, and the gain of the photo sensor unit is determined based on the gain correction information corresponding to the block to be adjusted. To adjust the white balance for each block of the predetermined LED unit. It can be.

  Thus, in the configuration in which one photosensor unit is provided for a plurality of LED units, by adjusting the gain of the photosensor unit based on the gain correction information set in advance according to the position of the LED unit, Calibration of the photo sensor unit can be performed in an optimum state.

  Further, in the configuration in which the photo sensor unit is provided for each of the plurality of LED units, the current value for each LED unit set so that the outputs of the respective photo sensor units are substantially equal to each other, and the white value of one LED unit. Based on the information for determining the balance, the white balance of the other LED units can be adjusted.

  Also, each LED unit is divided into a plurality of blocks, and the gain of the photo sensor unit is adjusted based on gain correction information set in advance according to the position of the block, thereby achieving white balance for each block. Can do.

  According to the backlight system, the liquid crystal display device including the backlight system, and the backlight adjustment method of the present invention, the light emission of each LED can be adjusted easily and surely, and thereby a good white balance without color misregistration can be achieved. Can be realized.

  The reason is that, in the configuration in which one photosensor unit for detecting the light of the LED is arranged in the vicinity of the center of the short side of the LED unit having a plurality of rows of LED units in which LEDs of a plurality of emission colors are arranged, the LED unit This is because the calibration of the photo sensor unit can be performed in an optimum state by adjusting the gain of the photo sensor unit based on the gain correction information set in accordance with the position of.

  In addition, in the configuration in which the photo sensor unit is arranged in each LED unit of the LED unit including a plurality of rows of LED units in which LEDs of a plurality of light emitting colors are arranged, the output of each photo sensor unit is set to be approximately equal in advance. This is because the white balance of the other LED units can be adjusted based on the current value for each LED unit and the information for determining the white balance of one LED unit.

  Further, each LED unit is divided into a plurality of blocks, and the white balance is adjusted for each block by adjusting the gain of the photo sensor unit based on gain correction information set in advance according to the position of the block. Because it can.

1 is a block diagram showing a schematic configuration of a liquid crystal display device according to a first embodiment of the present invention. It is a figure which shows the structure of the LED part and photosensor part which concern on the 1st Example of this invention. It is a circuit diagram which shows the structure of the photosensor part which concerns on 1st Example of this invention. It is a figure which shows the structure of the LED part and photosensor part which concern on the 2nd Example of this invention. It is a figure which shows the operation state of the LED part which concerns on the 2nd Example of this invention. It is a figure which shows the operation state of the LED part which concerns on the 2nd Example of this invention. It is a block diagram which shows schematic structure of the conventional liquid crystal display device.

  As shown in the prior art, when a part of the LED group in the screen is sequentially blinked, the desired luminance, luminance uniformity and white balance cannot be obtained because the light emission characteristics and light emission amount of the LED are not constant. Patent Document 1 discloses a technique in which a backlight control unit controls a light emission amount of each of a plurality of divided regions based on an output from a photosensor. However, this method requires continuous detection of light in all divided periods and correction for matching the luminance and white balance of all divided areas. Since the scale of the light control unit becomes large and the distance from the photosensor differs depending on the LED group, there arises a problem that further correction is required to match the luminance and chromaticity of the LED group.

  Therefore, in the present invention, in a scan-type backlight having an LED unit having a plurality of rows of LED units in which a plurality of LEDs are arranged, a photosensor unit for detecting the amount of light from the LED is placed near the center of the short side of the LED unit. The photo sensor unit is provided with a function of automatically adjusting the gain according to the position where the LED unit is lit, so that the photo sensor unit can be calibrated in an optimum state.

  In the above-described scan type backlight, a photo sensor unit for detecting LED light is arranged at a position corresponding to each LED unit, and a plurality of photo sensor units are adjusted in advance so that the same output is obtained with the same light amount. The current value of each LED unit is adjusted and stored so that the output of each photo sensor unit is the same (that is, the light emission of each LED unit is the same), and the white of one LED unit is stored. The balance is adjusted, and PWM control is performed in common for each LED unit.

  Also, each LED unit is divided into a plurality of blocks, and the current value is adjusted for each block so as to match the reference block. At this time, the gain of the photo sensor unit is adjusted so that the variation does not increase even in the block of the LED unit at a distance from the photo sensor unit.

  As a result, it is possible to easily and surely adjust the brightness and white balance without increasing the scale of the backlight control unit, and to provide a scan-type backlight system that can achieve white balance without color shift. .

  To describe the above-described embodiment of the present invention in more detail, the backlight system, the liquid crystal display device, and the backlight adjustment method according to the first embodiment of the present invention will be described with reference to FIGS. explain. FIG. 1 is a diagram showing a schematic configuration of a backlight system of the present embodiment and a liquid crystal display device using the backlight system, and FIG. 2 is a diagram showing details of an LED unit and a photosensor unit of FIG. FIG. 3 is a circuit diagram showing a specific configuration of the photosensor section.

  As shown in FIG. 1, the liquid crystal display device including the backlight system of the present embodiment detects an LED unit 1 including a plurality of LEDs, an LED driver unit 2 that drives the LED unit 1, and light from the LED unit 1. A photosensor unit 10 that controls the LED driver unit 2 and the photosensor unit 10, and a liquid crystal panel 4 in which liquid crystal is sandwiched between a pair of substrates (the drive system and the configuration of the switching elements are arbitrary) ) And an LCD driver unit 5 for driving the liquid crystal panel 4.

  Then, a timing controller (not shown) supplies a signal for driving the liquid crystal display device to the LCD driver unit 5 and the backlight control unit 3, and the LCD driver unit 5 drives the liquid crystal panel 4 by the signal. The backlight control unit 3 outputs an LED drive signal to the LED driver unit 2, and the LED driver unit 2 causes the LED unit 1 to emit light in synchronization with the display on the liquid crystal panel 4 based on the LED drive signal. The photosensor unit 10 detects the light from the LED unit 1, converts it into an electrical signal, returns it to the backlight control unit 3, and constitutes a feedback loop.

  FIG. 2 is a diagram showing the details of the LED unit 1 and the photosensor unit 10 of FIG. 1, and the LED unit 1 of the present embodiment has a plurality of light emitting color LEDs such as RGB arranged in a straight line. This is a scan-type backlight including a plurality of LED units D1 to D5, and each LED unit is configured to achieve white balance in units of LED units. Further, only one photosensor unit 10 that detects the light of the LED is disposed in the vicinity of the center of the short side of the LED unit 1 (side on the end side in the longitudinal direction of the LED unit).

  Although FIG. 2 shows a configuration including five rows of LED units, the LED units may be in a plurality of rows, and the quantity and arrangement of LEDs included in each LED unit are arbitrary. In FIG. 2, the photosensor unit 10 is arranged at the approximate center of the short side, but it is not always necessary to arrange it at the center, as long as the light from each LED unit can be detected.

  The operation of the backlight system having the above configuration will be described. The LED units are turned on one by one in order of D1, D2,..., And the light emission of each LED is adjusted so as to achieve the same white balance for each LED unit. At this time, the gain of the detection sensitivity of the photosensor unit 10 is adjusted according to the position of each LED unit, and the calibration of the photosensor unit 10 is performed in an optimum state.

  The photo sensor unit 10 has a configuration as shown in FIG. 3, for example, and G in the figure indicates a green photodiode, which is converted into a current and voltage by the resistance of Amp and VR, and a voltage corresponding to the amount of light. Is output to Vout. Then, the automatic gain control unit 11 controls the gain set by the backlight control unit 3.

  That is, gain correction information corresponding to the position of the LED unit is stored in advance in the automatic gain control unit 11, the LED unit that is lit is identified based on the signal from the backlight control unit 3, and the LED that is lit The gain is adjusted based on the gain correction information corresponding to the unit. For example, when detecting light of an LED unit far from the photo sensor unit 10, the gain of the photo sensor unit 10 is increased and detected, and when detecting light of an LED unit near the photo sensor unit 10, the gain is decreased. To detect.

  In this way, the LED unit 1 is provided with a plurality of rows of LED units each configured to achieve white balance, and one photosensor unit 10 is disposed at a substantially central portion on the short side of the LED unit 1. The gain correction information corresponding to the position of the LED unit is stored in the photo sensor unit 10, and when detecting the light of each LED unit, the gain is adjusted based on the gain correction information corresponding to the LED unit. By doing so, it is possible to easily and surely adjust the light emission of each LED, and it is possible to realize a good white balance without color misregistration.

  Next, a backlight system, a liquid crystal display device, and a backlight adjustment method according to a second embodiment of the present invention will be described with reference to FIGS. FIG. 4 is a diagram illustrating a configuration example of the LED unit and the photosensor unit, and FIGS. 5 and 6 are diagrams illustrating an operation state of the LED unit.

  In the first embodiment described above, one photosensor unit 10 is provided for a plurality of LED units. However, in this embodiment, a plurality of emission colors such as RGB are linearly formed as shown in FIG. Photo sensor portions 10a to 10e for detecting the light of the respective LED units are arranged in the vicinity of the ends in the longitudinal direction of the respective LED units D1 to D5 in which the LEDs are arranged. Further, each LED unit D1 to D5 is further divided into a plurality of blocks such as D1-1, D1-2, D1-3, and D1-4, and each block of each LED unit is individually driven. I can do it.

  FIG. 4 shows a configuration in which five LED units are provided and each LED unit is divided into four blocks. However, the LED unit may be in a plurality of rows, and each LED unit block is also a block. There may be more than one. In addition, it is assumed that the outputs of the photosensor units 10a to 10e are corrected in advance so that the outputs are substantially equal if the light amount is the same. The constituent elements other than the LED unit 1 and the photosensor unit 10 are the same as those of the first embodiment shown in FIG.

  The operation of the backlight system having the above configuration will be described. The LED units are turned on one by one in order of D1, D2,..., And the light emission of each LED is adjusted so as to achieve the same white balance for each LED unit. At this time, a current is supplied to each LED unit, and the light quantity is detected by the photosensor units 10a to 10e corresponding to each LED unit. Then, the LED driver unit 2 is controlled so that the outputs of the respective photo sensor units 10a to 10e are substantially equal to each other, and the current value to be supplied to each LED unit is adjusted. Store in a non-volatile memory. Then, after adjusting the current values for both RGB, the PWM (Pulse Width Modulation) value that determines the white balance, for example, is combined in one central photosensor unit 10 and the output is used in common. Thereby, white balance of other LED units can be adjusted by adjusting white balance for one LED unit.

  Further, as shown in FIGS. 5 and 6, for example, the LED unit D1 is divided into four blocks and individually lit with D1-1, D1-2, D1-3, and D1-4. 5 and 6 indicate the blocks that are lit. At this time, for example, the gain of the detection sensitivity of the photo sensor unit 10a corresponding to the LED unit D1 is increased every time the block that emits light leaves the photo sensor unit 10a, and the same output is obtained if the light emission luminance is the same. To do.

  That is, as in the first embodiment, gain correction information corresponding to the position of the block is stored in advance in the automatic gain control unit 11 and is lit based on a signal from the backlight control unit 3. The block of the unit is specified, and the gain is adjusted based on the gain correction information corresponding to the lighted block. For example, as shown in FIG. 5, when detecting light of a block (D1-1) located close to the photosensor unit 10a, the gain is reduced and detected, and as shown in FIG. 6, a block far from the photosensor unit 10a ( When detecting the light of D1-4), it is detected by increasing the gain of the photosensor unit 10a. Thus, by adjusting the output to the reference region, it is possible to easily achieve white balance in the peripheral portion, and to reduce chromaticity unevenness.

  In this way, the LED unit 1 is provided with a plurality of rows of LED units each configured to achieve white balance, and the photo sensor units 10a to 10e are arranged in the vicinity of the ends in the longitudinal direction of the LED units. Information for determining a white balance of a plurality of LED units (PWM value, etc.) by storing current values for obtaining substantially equal outputs from the respective photo sensor units 10a to 10e in the backlight control unit 3 or the like. By applying to the other LED unit, it is possible to easily and surely adjust the light emission of the LED, and it is possible to realize a good white balance without color misregistration.

  Further, each LED unit is divided into a plurality of blocks, gain correction information corresponding to each block is stored in the photosensor unit 10, and the light corresponding to each block is detected when the light is detected. By adjusting the gain based on the gain correction information, it is possible to easily obtain the white balance for each block.

  In the first embodiment, one photosensor unit 10 is provided, and the gain for each LED unit is adjusted based on previously stored gain correction information. In the second embodiment, each LED unit has a plurality of LED units. While dividing into blocks, a photo sensor unit 10 is provided for each LED unit, and the gain for each block is adjusted based on gain correction information stored in advance in each photo sensor unit. It is not limited to an example. For example, by combining the configurations of the first and second embodiments, gain correction corresponding to the position of each block of each LED unit in one photosensor unit 10 Information can be stored and the gain for each block can be adjusted by one photosensor unit 10.

  The present invention is not limited to a backlight system used for lighting a liquid crystal panel, and can be applied to general lighting devices.

DESCRIPTION OF SYMBOLS 1 LED part 2 LED driver part 3 Backlight control part 4 Liquid crystal panel 5 LCD driver part 10 Photo sensor part 11 Automatic gain control part 100 Back light 101-104 LED group 106 Backlight control part 107 Photo sensor 108 LCD driver 109 Liquid crystal panel

Claims (5)

An LED unit including a plurality of rows of LED units in which LEDs of a plurality of emission colors are arranged, a backlight control unit that outputs an LED drive signal based on a timing signal, and each of the LEDs based on the LED drive signal In a backlight system including at least an LED driver unit that sequentially turns on or off the units,
A plurality of photo sensor portions for detecting the light amount of each LED unit are provided in the vicinity of the longitudinal end portion of each LED unit so that the plurality of photo sensor portions can obtain substantially equal outputs with respect to the same light amount. Adjusted to
The backlight control unit stores a current value to be passed through each LED unit in order to make the outputs of the respective photo sensor units substantially equal, and information for determining a white balance of the predetermined LED unit and the current The white balance of the other LED unit is adjusted based on the value. Each of the LED units is divided into a plurality of blocks, and lighting or extinguishing can be controlled for each block.
The photo sensor unit stores gain correction information corresponding to the position of each block, and the gain of the photo sensor unit is adjusted based on the gain correction information corresponding to the block to be adjusted. The backlight system according to claim 1.   The backlight system according to claim 1 or 2 and a liquid crystal panel in which liquid crystal is sandwiched between a pair of substrates are provided, and lighting or extinguishing of the LED unit is controlled in synchronization with the display of the liquid crystal panel. A liquid crystal display device. An LED unit including a plurality of rows of LED units in which LEDs of a plurality of emission colors are arranged, a backlight control unit that outputs an LED drive signal based on a timing signal, and each of the LEDs based on the LED drive signal In a backlight system comprising at least an LED driver unit that sequentially turns on or off the units, and a plurality of photosensor units that are provided in the vicinity of end portions in the longitudinal direction of the LED units and detect the amount of light of the LED units. A method for adjusting the backlight,
A first step of adjusting the plurality of photosensor units so that substantially equal outputs are obtained with respect to the same amount of light;
A second step of storing, in the backlight control unit, a current value to be passed through each of the LED units in order to substantially equalize the output of each of the photosensor units;
A third step of adjusting the white balance of the predetermined LED unit;
4. A backlight adjustment method comprising at least a fourth step of adjusting white balance of another LED unit based on information for determining white balance of the LED unit and the current value. Each of the LED units is divided into a plurality of blocks, and lighting or extinguishing can be controlled for each block.
In the third step, gain correction information corresponding to the position of each block is stored in the photosensor unit, and the photosensor is based on the gain correction information corresponding to the block to be adjusted. The backlight adjustment method according to claim 4, wherein a white balance is adjusted for each of the blocks of the predetermined LED unit by adjusting a gain of the unit.

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