JP2007141799A - Surface lighting light source, luminance correction circuit and luminance correction method used for surface lighting light source - Google Patents

Surface lighting light source, luminance correction circuit and luminance correction method used for surface lighting light source Download PDF

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JP2007141799A
JP2007141799A JP2005337871A JP2005337871A JP2007141799A JP 2007141799 A JP2007141799 A JP 2007141799A JP 2005337871 A JP2005337871 A JP 2005337871A JP 2005337871 A JP2005337871 A JP 2005337871A JP 2007141799 A JP2007141799 A JP 2007141799A
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luminance
light emitting
led
emitting elements
light source
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JP2005337871A
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Japanese (ja)
Inventor
Nobuaki Honpo
Yuji Kondo
信明 本保
祐司 近藤
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Nec Lcd Technologies Ltd
Nec液晶テクノロジー株式会社
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    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09GARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/3406Control of illumination source
    • G09G3/342Control of illumination source using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines
    • G09G3/3426Control of illumination source using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines the different display panel areas being distributed in two dimensions, e.g. matrix
    • GPHYSICS
    • G02OPTICS
    • G02FDEVICES OR ARRANGEMENTS, THE OPTICAL OPERATION OF WHICH IS MODIFIED BY CHANGING THE OPTICAL PROPERTIES OF THE MEDIUM OF THE DEVICES OR ARRANGEMENTS FOR THE CONTROL OF THE INTENSITY, COLOUR, PHASE, POLARISATION OR DIRECTION OF LIGHT, e.g. SWITCHING, GATING, MODULATING OR DEMODULATING; TECHNIQUES OR PROCEDURES FOR THE OPERATION THEREOF; FREQUENCY-CHANGING; NON-LINEAR OPTICS; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating, or modulating; Non-linear optics
    • G02F1/01Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating, or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating, or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333Constructional arrangements; Manufacturing methods
    • G02F1/1335Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/1336Illuminating devices
    • G02F1/133602Direct backlight
    • G02F1/133603Direct backlight with LEDs
    • GPHYSICS
    • G02OPTICS
    • G02FDEVICES OR ARRANGEMENTS, THE OPTICAL OPERATION OF WHICH IS MODIFIED BY CHANGING THE OPTICAL PROPERTIES OF THE MEDIUM OF THE DEVICES OR ARRANGEMENTS FOR THE CONTROL OF THE INTENSITY, COLOUR, PHASE, POLARISATION OR DIRECTION OF LIGHT, e.g. SWITCHING, GATING, MODULATING OR DEMODULATING; TECHNIQUES OR PROCEDURES FOR THE OPERATION THEREOF; FREQUENCY-CHANGING; NON-LINEAR OPTICS; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating, or modulating; Non-linear optics
    • G02F1/01Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating, or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating, or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333Constructional arrangements; Manufacturing methods
    • G02F1/1335Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/1336Illuminating devices
    • G02F1/133602Direct backlight
    • G02F2001/133612Electrical details
    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09GARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00Control of display operating conditions
    • G09G2320/04Maintaining the quality of display appearance
    • G09G2320/041Temperature compensation
    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09GARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00Control of display operating conditions
    • G09G2320/06Adjustment of display parameters
    • G09G2320/0626Adjustment of display parameters for control of overall brightness
    • G09G2320/0633Adjustment of display parameters for control of overall brightness by amplitude modulation of the brightness of the illumination source
    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09GARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2360/00Aspects of the architecture of display systems
    • G09G2360/14Detecting light within display terminals, e.g. using a single or a plurality of photosensors

Abstract

【Task】
Provided is a surface illumination light source that provides illumination light with uniform luminance from the back surface to the entire display area of a transmissive display panel such as a liquid crystal display device.
An LED drive / correction circuit 73 supplies current or voltage to an LED 71. A part of the luminance of the emitted LED 71 is received by the photodiode 72 and converted into light / electricity, and the resistance value of the photodiode 72 decreases in proportion to the luminance. That is, if the brightness of the LED 71 increases, the resistance value of the photodiode 72 decreases, and if the brightness of the LED 71 decreases, the resistance value of the photodiode 72 increases. This resistance value is detected by the drive / detection circuit 74, and the resistance value is fed back to the LED drive / correction circuit 73. The LED driving / correcting circuit 73 changes the driving current or the driving voltage so that the luminance of the LED 71 becomes a value corresponding to the luminance setting voltage V1. The photodiode 72 is provided for each LED 71 on a one-to-one basis.
[Selection] Figure 1

Description

  The present invention relates to a surface illumination light source, a brightness correction circuit and a brightness correction method used for the surface illumination light source, and in particular, uniform brightness over the entire display area of a display panel such as a backlight of a liquid crystal display device. The present invention relates to a surface illumination light source suitable for use in the case where it is necessary to provide illumination light, a luminance correction circuit and a luminance correction method used for the surface illumination light source.

  Conventionally, a cold cathode tube is often used as a backlight of a liquid crystal display device, but in recent years, a backlight using an LED (Light Emitting Diode) has been manufactured. In an LED backlight, usually, a plurality of LEDs are connected in series and driven with a constant current. For this reason, the variation in the current luminance characteristics of the individual LEDs is directly reflected in the luminance variation in the display area of the liquid crystal display device. Here, the variation is a luminance characteristic with respect to current, a luminance characteristic with respect to temperature, and a secular change of these luminance characteristics. Conventionally, techniques for correcting this type of variation include those described in the following documents, for example.

FIG. 12 is a diagram illustrating an electrical configuration of a main part of the lighting device described in Patent Document 1.
As shown in the figure, the lighting device includes an LED substrate 10, a constant current power source 20, and a temperature compensation circuit 30. A large number of LEDs 11,..., 11 are mounted on the LED substrate 10. The constant current power supply 20 includes a resistor 21, a transistor 22, an amplifier circuit 23, and a comparison voltage generation circuit 24. The temperature compensation circuit 30 includes a field effect transistor (FET) 31, an LED 32, an amplifier circuit 33, and a light receiving element 34.

  In this lighting device, the LED 32 having the same temperature characteristics as the lighting LEDs 11,..., 11 emits light, and the luminance is converted into an electric signal by the light receiving element 34, and the electric signal is input to the comparison voltage generation circuit 24. The The output signal of the comparison voltage generation circuit 24 is input to the amplifier circuit 23. Based on the output signal of the amplifier circuit 23, a current designated by a constant reference value is supplied from the transistor 22 to the LEDs 11,. The temperature characteristics of the LEDs 11, ..., 11 are compensated. In this case, as shown in the characteristic diagram G2 in FIG. 13, when the luminance of the LED 32 changes with respect to the temperature (air temperature) change, the comparison voltage generation circuit 24, the amplifier circuit 23, and the transistor 22 show the characteristic diagram H1. As described above, the output current of the constant current power supply 20 changes, and the luminance of the LED substrate 10 is corrected. As a result, the characteristic does not change with respect to the temperature as shown in the characteristic chart G3 with respect to the characteristic diagram G1 that shows the state in which the luminance changes with respect to the temperature.

Moreover, FIG. 14 is a figure which shows one structural example of the conventional LED backlight.
In this LED backlight, the LEDs 41,..., 41 are composed of a combination of red (R), blue (B), green (G), or white. The LEDs 41,..., 41 are mounted on the substrate 42 and connected in series every predetermined number. In this case, in the white LED, the number corresponding to the power supply voltage is connected in series, and when it does not fit in one column, it may be configured in a plurality of columns and connected in parallel. In addition, when R, G, and B LEDs are used, a predetermined number of LEDs for each color are connected in series. In this LED backlight, a part of the luminance of the entire LEDs 41,... In this case, the light receiving element 43 and the color filter 44 are arranged for each of R, G, and B, or the light receiving characteristics of the light receiving element 43 are made wavelength dependent so that the luminance for each of R, G, and B is an electric signal Is converted to The drive current and voltage for the LEDs 41,..., 41 are adjusted based on the electrical signal proportional to the brightness, and the brightness received by the light receiving element 43 is controlled to be constant.

  For this reason, the luminance of the LEDs 41,..., 41 in the vicinity of the light receiving element 43 is controlled to follow smoothly, but the luminance of the LEDs 41,. There is a problem that it is difficult to do. Further, in the central portion of the substrate 42, since heat radiation is difficult, the temperature is likely to rise. Therefore, there is a problem that the ambient temperature of the LEDs 41,... 41 varies depending on the location, and it is difficult to make the luminance distribution uniform due to the temperature dependence of the LEDs 41,. Further, even when the luminance of each LED 41 varies due to the aging of the LEDs 41,..., 41, only the luminance characteristics of the LED 41 in the vicinity of the light receiving element 43 are adjusted. There is a problem that the luminance distribution characteristics vary. In order to improve this problem, Patent Document 2 proposes an LED backlight in which light receiving elements are provided in a plurality of places instead of one place.

FIG. 15 is a diagram showing a wiring configuration of LEDs of a backlight described in Patent Document 2. As shown in FIG.
In this backlight, as shown in FIG. 15, four LED rows each including 31 LEDs 51 connected in series are mounted on a substrate 50.

FIG. 16 is a diagram showing another wiring configuration of the LED of the backlight described in Patent Document 2.
In this backlight, as shown in FIG. 16, a large number of LED rows each including three to seven LEDs 51 connected in series are provided.

FIG. 17 is a cross-sectional view of a backlight provided with the LED 51 in FIG. 15 or FIG.
In the backlight 52, as shown in FIG. 17, each light receiving element 53 is arranged between the LEDs 51, and a diffuser 54 and an LCD (Liquid Crystal Display) panel 55 are provided in the light emitting direction of the LEDs 51. It has been.

FIG. 18 is a block diagram showing the configuration of a correction circuit that corrects the luminance characteristics of the LED 51 in FIG. 15 or FIG.
In this correction circuit, the output signal a of the light receiving element 53 is detected by the detector 61, and the luminance characteristic of the LED 51 is corrected by the control unit 62 based on the detection signal b.

In the backlight control device for a liquid crystal display described in Patent Document 3, the amount of light emitted from an LED disposed as a backlight on the back side of the liquid crystal panel is controlled according to the brightness of the surroundings of the liquid crystal panel. Even if the use temperature of the LED changes, the amount of emitted light is controlled to be a predetermined value.
JP 2004-221158 (abstract, FIGS. 1 and 4) Japanese Patent Laying-Open No. 2005-115372 (Abstract, FIGS. 7A, 7B, 8B, and 10) JP 2003-215534 A (Abstract, FIG. 1)

However, the above conventional technique has the following problems.
That is, in the illumination device described in Patent Document 1 and the backlight described in Patent Document 2, the brightness of each LED constituting the LED light source is detected with respect to the LED light source composed of a plurality of LEDs. Cannot be corrected. For this reason, there has been a problem that when the luminance change due to aging of the LED occurs, the luminance distribution in the liquid crystal panel changes. In addition, even with respect to a luminance change due to a temperature change, even though the change in the total amount can be corrected, it is not a correction for the luminance change of each LED, so there is a problem that the luminance distribution in the liquid crystal panel changes.

  In addition, in the illumination device described in Patent Document 1, when detecting a temperature change or aging change of an LED, the brightness of the LED different from the light source of the actual panel is referred to. In this case, since it is rare that the temperature, temperature characteristics, and aging characteristics (life characteristics) of the light source LED and the reference LED match, there is a problem that it is difficult to correct these characteristics. Further, in the backlight described in Patent Document 2, a plurality of LEDs are connected in series, but it is impossible to individually correct characteristics such as luminance of these LEDs. It is only possible to adjust the drive current of the LED group connected in series to change the luminance of the LED group as a whole. Further, the backlight control device described in Patent Document 3 controls the light emission luminance of the LED in accordance with the brightness around the liquid crystal panel. Therefore, the present invention is different from the present invention. Not improved.

  The present invention has been made in view of the above-described circumstances, and provides a surface illumination light source that provides illumination light with uniform brightness to the entire display area of a display panel such as a liquid crystal display device, and a luminance correction circuit used for the surface illumination light source. The purpose is to provide.

  In order to solve the above-described problem, the invention according to claim 1 is a surface illumination light source in which a plurality of light emitting elements are arranged in a planar shape, and illumination light is incident on the display area of a transmissive display panel from the back side. Therefore, the luminance is set to a predetermined target value for each of the light emitting elements, and the deviation amount of the luminance at the time of lighting from the target value is detected for each of the light emitting elements, and the detected deviation amount is set to the detected deviation amount. A luminance correction circuit for matching the luminance with the target value is provided.

  A second aspect of the present invention relates to the surface illumination light source according to the first aspect, wherein the luminance correction circuit is provided one-to-one with respect to the plurality of light emitting elements, and emits light emitted from the light emitting elements. A plurality of light receiving elements that receive light and generate a luminance detection signal of a level corresponding to the luminance, and a one-to-one correspondence with the plurality of light emitting elements, and supply driving power to each of the light emitting elements And a drive / correction circuit that detects a deviation of the luminance of the light emitting element from each target value based on the level of the luminance detection signal and corrects the driving power so as to compensate for the deviation. It is characterized by being.

  According to a third aspect of the present invention, there is provided the surface illumination light source according to the second aspect, wherein the light emitting elements and the light receiving elements are arranged close to each other in a one-to-one relationship.

  According to a fourth aspect of the present invention, there is provided the surface illumination light source according to the third aspect, wherein the light emitting elements and the light receiving elements are mounted in the same package.

  The invention according to claim 5 relates to a luminance correction circuit, and is used as a surface illumination light source in which a plurality of light emitting elements are arranged in a planar shape, and illumination light is incident on the display area of a transmissive display panel from the back side. The luminance is set to a predetermined target value for each of the light emitting elements, and the amount of deviation of the luminance at the time of lighting from the target value is detected for each of the light emitting elements, and based on the detected amount of deviation The brightness is made to coincide with the target value.

  A sixth aspect of the present invention relates to the luminance correction circuit according to the fifth aspect, wherein the plurality of light emitting elements are provided on a one-to-one basis, receive light emitted from the light emitting elements, and adjust the luminance thereof. A plurality of light receiving elements that generate a luminance detection signal of a corresponding level and a one-to-one correspondence with each of the plurality of light emitting elements, supplying driving power to each of the light emitting elements, and the luminance detection signal And a drive / correction circuit that detects the deviation of the luminance of the light-emitting element from the target values and corrects the driving power so as to compensate for the deviation. .

  The invention according to claim 7 relates to a luminance correction method, and is used for a surface illumination light source in which a plurality of light emitting elements are arranged in a planar shape, and illumination light is incident on the display area of a transmissive display panel from the back side. The luminance is set to a predetermined target value for each of the light emitting elements, and the deviation amount of the luminance at the time of lighting from the target value is detected for each of the light emitting elements, and based on the detected deviation amount The brightness is made to coincide with the target value.

  According to the configuration of the present invention, the luminance is set to a predetermined target value for each light emitting element, the amount of deviation of the luminance of each light emitting element from the target value is detected, and the luminance is based on the amount of deviation. Since the luminance correction circuit that matches the target value is provided, the luminance of each light emitting element can be made uniform, and the brightness of the entire display area of the display panel can be made uniform. In addition, the luminance of each light emitting element is 1: 1 and converted to a luminance detection signal by each light receiving element, and the luminance detection signal is fed back to the drive / correction circuit. Can compensate. Further, since the luminance of each light emitting element is fed back, it is not necessary to extract only the amount of temperature change and feed back, so that the temperature correction circuit for each light emitting element can be made unnecessary. In addition, since each light emitting element and each light receiving element are arranged close to each other in the same package on a one-to-one basis, the luminance of each light emitting element is individually corrected, so that the light emitting element and the light receiving element vary. Even if there is, the brightness of each light emitting element can be made uniform by appropriately setting the target value of brightness. In addition, since each light emitting element and each light receiving element have a one-to-one correspondence, even if each light emitting element has any of R, G, and B emission colors, color balance can be achieved without using a color filter. Can compensate for changes. Therefore, when this surface illumination light source is used as, for example, a backlight of a transmissive liquid crystal panel, illumination light can be given to the entire display area of the liquid crystal panel with uniform luminance.

  A luminance correction circuit used for a surface illumination light source and a surface illumination light source in which the luminance of each LED (light emitting element) is converted into a luminance detection signal by each light receiving element on a one-to-one basis and the luminance detection signal is fed back to the luminance correction circuit. provide.

FIG. 1 is a block diagram showing the electrical configuration of the main part of a surface illumination light source according to the first embodiment of the present invention.
The surface illumination light source of this example is used as, for example, a backlight of a transmissive liquid crystal panel provided in a liquid crystal display device, and as shown in the figure, an LED 71, a photodiode 72, an LED drive / correction circuit 73, Drive / detection circuit 74. Although one LED 71 is displayed in this figure, it is composed of a plurality of backlights and arranged in a plane. The photodiode 72 is provided on a one-to-one basis for each LED 71, receives light from the LED 71, and generates a luminance detection voltage a having a level corresponding to the luminance. The drive / detection circuit 74 is provided on a one-to-one basis for each photodiode 72, supplies power to the photodiode 72, and uses the luminance detection voltage a from the photodiode 72 as the luminance detection voltage V2 as it is as an LED drive / correction circuit. To 73.

  The LED drive / correction circuit 73 is provided on a one-to-one basis for each LED 71, supplies driving power c to the LED 71, and based on the level of the luminance detection voltage V2 from the drive / detection circuit 74. Deviations with respect to each target value (value corresponding to the luminance setting voltage V1) of the luminance of the LED 71 are detected, and the driving power c is corrected so as to compensate for the deviation. In particular, in this embodiment, the LED drive / correction circuit 73 increases the supplied current in accordance with, for example, a decrease in the luminance of the LED 71. The photodiode 72, the LED drive / correction circuit 73, and the drive / detection circuit 74 constitute a luminance correction circuit. The luminance correction circuit sets the luminance for each LED 71 to a predetermined target value, detects the amount of deviation of the luminance of the LED 71 from the target value, and determines the luminance based on the amount of deviation. Match the target value.

FIG. 2 is a circuit diagram showing an example of the electrical configuration of the LED drive / correction circuit 73 and the drive / detection circuit 74 in FIG.
As shown in FIG. 2, the LED drive / correction circuit 73 includes resistors 81, 82, 83, 84, an operational amplifier (operational amplifier) 85, resistors 86, 87, 88, an operational amplifier 89, and a resistor 90. , An operational amplifier 91 and a resistor 92. The drive / detection circuit 74 includes a constant current circuit 93 and an operational amplifier 94.

FIG. 3 is a diagram showing an example of an arrangement state of the LED 71, the photodiode 72, the LED drive / correction circuit 73, and the drive / detection circuit 74 in FIG.
As shown in FIG. 3, the LED 71, the photodiode 72, the LED drive / correction circuit 73, and the drive / detection circuit 74 are arranged on the substrate 75 one by one. In this case, the LED 71 has a shape sealed with a transparent resin or the like, or a bare chip. In the case of a bare chip, it is desirable to seal part or all of the LED 71 mounting portion of the substrate 75 with resin or the like. In particular, in this embodiment, the LEDs 71 and the photodiodes 72 are arranged close to each other on a one-to-one basis, and the LED drive / correction circuit 73 and the drive / detection circuit 74 are integrated.

FIG. 4 is a diagram showing another example of the arrangement state of the LED 71, the photodiode 72, the LED drive / correction circuit 73, and the drive / detection circuit 74 in FIG.
As shown in FIG. 4, for example, 20 sets of LED 71, photodiode 72, LED drive / correction circuit 73 and drive / detection circuit 74 are arranged on a substrate 75. In this case, when a certain group of photodiodes 72 receives light from an adjacent group of LEDs 71, it is affected by light other than the LED 71 that should be compensated for, so that the light from the other LEDs 71 is blocked. It is desirable to take specific measures.

  In the luminance correction method used for this surface illumination light source, the luminance is set to a predetermined target value for each LED 71, and the deviation amount of the luminance at the time of lighting from the target value is detected for each LED 71, Based on the detected amount of deviation, the luminance is corrected so as to match the target value. In this case, current or voltage is supplied to the LED 71 from the LED drive / correction circuit 73 in FIG. At this time, the driving method may be constant current driving or constant voltage driving. A part of the luminance of the emitted LED 71 is received by the photodiode 72 and subjected to optical / electrical conversion, and the resistance value of the photodiode 72 decreases in proportion to the luminance. That is, if the brightness of the LED 71 increases, the resistance value of the photodiode 72 decreases, and if the brightness of the LED 71 decreases, the resistance value of the photodiode 72 increases. This resistance value is detected by the drive / detection circuit 74, and the resistance value is fed back to the LED drive / correction circuit 73. The LED driving / correcting circuit 73 changes the driving current or the driving voltage so that the luminance of the LED 71 becomes a value corresponding to the luminance setting voltage V1.

That is, as shown in FIG. 2, in order to determine the drive current of the LED 71, the luminance setting voltage V1 is input, and the luminance of the LED 71 is set as a voltage. Then, the current I 0 is supplied from the LED drive / correction circuit 73 to the LED 71. This current I0 is expressed by the following equation (1).
I0 = V3 / RSC (1)
However,
RSC: Resistance value of the resistor 90 The voltage V3 that determines the value of the current I0 is the output voltage of the adder / subtractor circuit constituted by the operational amplifier 85 and is expressed by the following equation (2).
V3 = (-R2 / R1) * V1 + (R4 / R3) * V2 (2)
However,
R1: Resistance value of the resistor 81
R2: Resistance value of resistor 82
R3: Resistance value of resistor 83
R4: Resistance value of resistor 84

  The luminance detection voltage V2 is obtained by feeding back the drive voltage of the photodiode 72 to the LED drive / correction circuit 73 through the voltage follower by the operational amplifier 94. Since the photodiode 72 is driven by the constant current circuit 93, the photodiode 72 has a resistance value corresponding to the luminance of the LED 71. That is, when the luminance of the LED 71 decreases, the resistance value of the photodiode 72 increases, the driving voltage of the photodiode 72 increases, and the luminance detection voltage V2 increases. When the luminance detection voltage V2 increases, the voltage V3 increases by a voltage R4 / R3 times the luminance detection voltage V2 based on the equation (2). When the voltage V3 increases, the drive current of the LED 71 increases and the luminance increases. Therefore, by selecting the resistance values R1, R2, R3, R4 and the current value Id of the constant current circuit 93, feedback by the photodiode 72 is applied according to the luminance change of the LED 71, and the luminance change is compensated.

  As described above, in this first embodiment, the brightness of each LED 71 is 1: 1 and converted to the brightness detection voltage V2 by each photodiode 72, and the brightness detection voltage V2 is fed back to the drive / detection circuit 74. The variation and change in luminance of each LED 71 are automatically compensated. Further, since the brightness of each LED 71 is fed back, it is not necessary to extract only the temperature change amount and feed back, so that the temperature correction circuit for each LED 71 becomes unnecessary. Further, since each LED 71 and each photodiode 72 are arranged close to each other in a one-to-one relationship, the brightness of each LED 71 is individually corrected. By appropriately setting the voltage V1, the brightness of each LED 71 becomes uniform. In addition, since each LED 71 and each photodiode 72 have a one-to-one correspondence, even if each LED 71 has an emission color of R, G, or B, the color balance can be changed without using a color filter. Compensated.

FIG. 5 is a cross-sectional view showing the arrangement of the main part of the surface illumination light source according to the second embodiment of the present invention, which is common to the elements common to the elements in FIG. 4 showing the first embodiment. The code | symbol is attached | subjected.
In the surface illumination light source of this example, as shown in FIG. 5, the LED 71, the photodiode 72, the LED drive / correction circuit 73 and the drive / detection circuit 74 are mounted on the same package 76. The package 76 is formed with terminals (not shown) for connection to the outside. In this surface illumination light source, the LED 71 and the photodiode 72 are arranged close to the package 76 on a one-to-one basis, and the LED drive / correction circuit 73 and the drive / detection circuit 74 are integrated, which is the same as in the first embodiment. There are advantages.

FIG. 6 is a sectional view showing the arrangement of the main part of the surface illumination light source according to the third embodiment of the present invention, and is common to the elements common to the elements in FIG. 5 showing the second embodiment. The code | symbol is attached | subjected.
In the surface illumination light source of this example, as shown in FIG. 6, the photodiode 72, the LED drive / correction circuit 73 and the drive / detection circuit 74 in FIG. Has been. In this surface illumination light source, as in the first embodiment, the LEDs 71 and the photodiodes 72 are arranged close to each other on a one-to-one basis and have the same advantages.

FIG. 7 is a sectional view showing the arrangement of the main part of the surface illumination light source according to the fourth embodiment of the present invention.
In the surface illumination light source of this example, as shown in FIG. 7, the LED drive / correction circuit 73 and the drive / detection circuit 74 are outside the package 76 and are mounted on the substrate 75 together with the package 76. The substrate 75 is made of an organic material or an inorganic material. In this surface illumination light source, as in the first embodiment, the LEDs 71 and the photodiodes 72 are arranged close to each other in a one-to-one relationship and have the same advantages.

FIG. 8 is a sectional view showing the arrangement of the main part of the surface illumination light source according to the fifth embodiment of the present invention.
In the surface illumination light source of this example, as shown in FIG. 8, a package 76 similar to that in FIG. 6 is mounted on the substrate 75, and a correction element 78 is newly mounted on the substrate 75. The correction element 78 can write, for example, a variable resistor, a pressure film printing resistance element trimmed by a laser, a zener zap element composed of a resistor and a zener diode, or data corresponding to each target value of luminance. A brightness setting voltage V1 is applied to the LED drive / correction circuit 73. In this surface illumination light source, even if each LED 71 and each photodiode 72 have variations, the brightness of each LED 71 becomes uniform by appropriately setting the brightness setting voltage V1 by the correction element 78.

FIG. 9 is a sectional view showing the arrangement of the main part of the surface illumination light source according to the sixth embodiment of the present invention, showing the elements in FIG. 7 showing the fourth embodiment and the fifth embodiment. Elements common to the elements in FIG. 8 are given common reference numerals.
In the surface illumination light source of this example, as shown in FIG. 9, the correction element 78 in FIG. 8 is mounted on the substrate 75 in FIG. In this surface illumination light source, even if each LED 71 and each photodiode 72 have variations, the brightness setting voltage V1 is appropriately set by the correction element 78 in the same manner as in the eighth embodiment, whereby the brightness of each LED 71 is set. Becomes uniform.

FIG. 10 is a cross-sectional view showing the arrangement of the main part of the surface illumination light source according to the seventh embodiment of the present invention, and is common to the elements common to the elements in FIG. 9 showing the sixth embodiment. The code | symbol is attached | subjected.
In the surface illumination light source of this example, as shown in FIG. 10, the LED drive / correction circuit 73 and the drive / detection circuit 74 and the correction element 78 in FIG. 9 are integrated into a single IC 79. Yes. In this surface illumination light source, even if each LED 71 and each photodiode 72 vary, the brightness setting voltage V1 is appropriately set by the correction element 78 of the IC 79 as in the case of the eighth embodiment. The brightness becomes uniform.

FIG. 11 is a circuit diagram showing an electrical configuration of a luminance correction circuit used in the surface illumination light source according to the eighth embodiment of the present invention, and is common to the elements in FIG. 2 showing the first embodiment. Are denoted by common reference numerals.
In the luminance correction circuit of this example, as shown in FIG. 11, an LED drive / correction circuit 73A having a different configuration is provided instead of the LED drive / correction circuit 73 in FIG. The LED drive / correction circuit 73A includes resistors 81, 82, 83, and 84, an operational amplifier 85, an operational amplifier 95, an n-channel MOSFET (nMOS) 96, and a variable resistor 97.

In this luminance correction circuit, the current I0 flowing through the LED 71 is expressed by the following equation (3).
I0 = V4 / RICC (3)
However,
RICC: Resistance value of variable resistor 97 Since this brightness correction circuit operates so that the voltage V3 of the non-inverting input terminal (+) of the operational amplifier 95 and the voltage of the inverting input terminal (-) become the same, the voltage V3 The voltage V4 is almost the same. The voltage V4 and the resistance value RICC of the variable resistor 97 determine the current I0 flowing through the LED 71. Further, by adjusting the resistance value RICC, a desired current flows through the LED 71, and the LED 71 emits light with a desired luminance. Since the operational amplifier 85 constitutes an addition / subtraction circuit as in the first embodiment, the voltage V3 is changed by changing the luminance setting voltage V1. As described above, the luminance correction circuit having a configuration different from that of the first embodiment provides almost the same advantage.

The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to the embodiment, and even if there is a design change without departing from the gist of the present invention, Included in the invention.
For example, the configuration of the luminance correction circuit illustrated in FIG. 2 or 11 may be another circuit configuration as long as it has a similar function.

  The present invention can be generally applied to a case where illumination light needs to be given with uniform luminance to the entire display area of a display panel, such as a backlight of a liquid crystal display device.

It is a block diagram which shows the electric constitution of the principal part of the surface illumination light source which is 1st Example of this invention. FIG. 2 is a circuit diagram showing an electrical configuration of an LED drive / correction circuit 73 and a drive / detection circuit 74 in FIG. 1. It is a figure which shows the example of arrangement | positioning state of LED71 in FIG. 1, the photodiode 72, the LED drive / correction circuit 73, and the drive / detection circuit 74. FIG. It is a figure which shows the other example of arrangement | positioning state of LED71 in FIG. 1, the photodiode 72, the LED drive / correction circuit 73, and the drive / detection circuit 74. FIG. It is sectional drawing which shows the arrangement | positioning state of the principal part of the surface illumination light source which is 2nd Example of this invention. It is sectional drawing which shows the arrangement | positioning state of the principal part of the surface illumination light source which is the 3rd Example of this invention. It is sectional drawing which shows the arrangement | positioning state of the principal part of the surface illumination light source which is the 4th Example of this invention. It is sectional drawing which shows the arrangement | positioning state of the principal part of the surface illumination light source which is 5th Example of this invention. It is sectional drawing which shows the arrangement | positioning state of the principal part of the surface illumination light source which is the 6th Example of this invention. It is sectional drawing which shows the arrangement | positioning state of the principal part of the surface illumination light source which is the 7th Example of this invention. It is a circuit diagram which shows the electrical constitution of the brightness correction circuit used for the surface illumination light source which is the 8th Example of this invention. It is a figure which shows the electrical constitution of the principal part of the illuminating device described in patent document 1. FIG. It is a figure explaining operation | movement of the illuminating device of FIG. It is a figure which shows one structural example of the conventional LED backlight. It is a figure which shows the wiring structure of LED of the backlight described in patent document 2. FIG. It is a figure which shows the other wiring structure of LED of the backlight described in patent document 2. FIG. It is sectional drawing of the backlight in which LED51 in FIG. 15 or FIG. 16 was provided. It is a block diagram which shows the structure of the correction circuit which correct | amends the luminance characteristic of LED51 in FIG. 15 or FIG.

Explanation of symbols

71 LED (light emitting element)
72 Photodiode (light receiving element)
73, 73A LED drive / correction circuit (part of the drive / correction circuit)
74 Drive / detection circuit (part of drive / correction circuit)
76 Package 78 Correction element (part of drive / correction circuit)
V1 brightness setting voltage (target value of brightness)
V2 luminance detection voltage (luminance detection signal)

Claims (7)

  1. A surface illumination light source in which a plurality of light emitting elements are arranged in a plane shape, and illumination light is incident on the display area of a transmissive display panel from the back,
    The luminance is set to a predetermined target value for each of the light emitting elements, and a deviation amount of the luminance at the time of lighting from the target value is detected for each of the light emitting elements, and based on the detected deviation amount, A surface illumination light source characterized in that a luminance correction circuit for matching the luminance with the target value is provided.
  2. The brightness correction circuit includes:
    A plurality of light receiving elements that are provided one-to-one with respect to the plurality of light emitting elements, receive light emitted from each of the light emitting elements, and generate a luminance detection signal of a level corresponding to the luminance;
    The plurality of light emitting elements are provided on a one-to-one basis, supplying driving power to the light emitting elements, and for each target value of the luminance of the light emitting elements based on the level of the luminance detection signal. 2. The surface illumination light source according to claim 1, comprising a drive / correction circuit that detects a deviation and corrects the driving power so as to compensate for the deviation.
  3.   3. The surface illumination light source according to claim 2, wherein the light emitting elements and the light receiving elements are arranged close to each other in a one-to-one relationship.
  4.   4. The surface illumination light source according to claim 3, wherein each light emitting element and each light receiving element are mounted in the same package.
  5. A plurality of light emitting elements are arranged in a planar shape, and are used as a surface illumination light source for making illumination light incident on the display area of a transmissive display panel from the back,
    The luminance is set to a predetermined target value for each of the light emitting elements, and a deviation amount of the luminance at the time of lighting from the target value is detected for each of the light emitting elements, and based on the detected deviation amount, A luminance correction circuit characterized in that luminance is made to coincide with the target value.
  6. A plurality of light receiving elements that are provided one-to-one with respect to the plurality of light emitting elements, receive light emitted from each of the light emitting elements, and generate a luminance detection signal of a level corresponding to the luminance;
    The plurality of light emitting elements are provided on a one-to-one basis, supplying driving power to the light emitting elements, and for each target value of the luminance of the light emitting elements based on the level of the luminance detection signal. 6. The luminance correction circuit according to claim 5, further comprising a drive / correction circuit that detects a deviation and corrects the driving power so as to compensate for the deviation.
  7. A plurality of light emitting elements are arranged in a planar shape, and are used as a surface illumination light source for making illumination light incident on the display area of a transmissive display panel from the back,
    The luminance is set to a predetermined target value for each of the light emitting elements, and a deviation amount of the luminance at the time of lighting from the target value is detected for each of the light emitting elements, and based on the detected deviation amount, A luminance correction method characterized by matching luminance with the target value.
JP2005337871A 2005-11-22 2005-11-22 Surface lighting light source, luminance correction circuit and luminance correction method used for surface lighting light source Withdrawn JP2007141799A (en)

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JP2005337871A JP2007141799A (en) 2005-11-22 2005-11-22 Surface lighting light source, luminance correction circuit and luminance correction method used for surface lighting light source
US11/592,289 US20070115685A1 (en) 2005-11-22 2006-11-03 Flat lighting source, luminance correcting circuit, luminance correcting method and liquid crystal display
KR20060112670A KR100854192B1 (en) 2005-11-22 2006-11-15 Flat lighting source, luminance correcting circuit, luminance correcting method and liquid crystal display
TW095142426A TW200727047A (en) 2005-11-22 2006-11-16 Flat lighting source, luminance correcting circuit, luminance correcting method and liquid crystal display
CN 200610162418 CN1971367A (en) 2005-11-22 2006-11-22 Flat lighting source, luminance correcting circuit, luminance correcting method and liquid crystal display

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US20070115685A1 (en) 2007-05-24
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KR20070054101A (en) 2007-05-28
TW200727047A (en) 2007-07-16

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