WO2008099997A1 - Luminance and color temperature control system of led backlight unit - Google Patents

Luminance and color temperature control system of led backlight unit Download PDF

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Publication number
WO2008099997A1
WO2008099997A1 PCT/KR2007/004031 KR2007004031W WO2008099997A1 WO 2008099997 A1 WO2008099997 A1 WO 2008099997A1 KR 2007004031 W KR2007004031 W KR 2007004031W WO 2008099997 A1 WO2008099997 A1 WO 2008099997A1
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WO
WIPO (PCT)
Prior art keywords
light
regions
color temperature
luminance
backlight unit
Prior art date
Application number
PCT/KR2007/004031
Other languages
French (fr)
Inventor
Min-Hyung Ahn
Hong-Kyu Park
Original Assignee
L & F Co., Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to KR10-2007-0014332 priority Critical
Priority to KR1020070014332A priority patent/KR100861461B1/en
Application filed by L & F Co., Ltd. filed Critical L & F Co., Ltd.
Publication of WO2008099997A1 publication Critical patent/WO2008099997A1/en

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Classifications

    • 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
    • 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
    • G09G2320/064Adjustment of display parameters for control of overall brightness by time 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
    • G09G2320/00Control of display operating conditions
    • G09G2320/06Adjustment of display parameters
    • G09G2320/0666Adjustment of display parameters for control of colour parameters, e.g. colour temperature
    • 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
    • G09G2360/145Detecting light within display terminals, e.g. using a single or a plurality of photosensors the light originating from the display screen

Abstract

Disclosed is a luminance and color temperature control system of an LED backlight unit. The system includes: a backlight unit including multiple sub-regions each of which includes a predetermined number of light-emitting diodes, the backlight unit outputting light with specific luminance and specific color temperature by causing the light-emitting diodes included in the respective sub-regions to emit light according to powers input to the respective sub-regions; a light detector installed outside of the backlight unit, the light detector including an image pickup device which detects light output from the backlight unit and converts the detected light into an electrical signal, detecting luminance and color temperature distribution of light output from the respective sub-regions based on light output from the backlight unit, and outputting a detection signal which has a level corresponding to luminance and color temperature of light output from the respective sub-regions; and a controller comparing the level of the detection signal output from the light detector with a prestored reference level corresponding to prestored predetermined luminance and color temperature, and outputting a control signal to control power input to the respective sub-regions in order to change luminance and color temperature of light output from the respective sub-regions based on a result of the comparison, so that the light-emitting diodes in the backlight unit can be controlled in real time to uniformly emit light.

Description

Description

LUMINANCE AND COLOR TEMPERATURE CONTROL SYSTEM OF LED BACKLIGHT UNIT

Technical Field

[1] The present invention relates to a luminance and color temperature control system of a light-emitting diode backlight unit, and more particularly to a luminance and color temperature control system of a light-emitting diode backlight unit, which measures the luminance and color temperature of a light-emitting diode backlight for an LCD by means of a video camera capable of easily condensing light, and corrects unevenness of the luminance and color temperature distribution according to the locations of sub- regions and the individual deviations of light-emitting diodes included in the backlight. Background Art

[2] As generally known in the art, display devices are classified into light-emitting type display devices, such as a Cathode Ray Tube (CRT), an Organic Electro-Luminescence Display, and a Plasma Display (PDP), which emit light themselves, and light-receiving type display devices, such as a Liquid Crystal Display (LCD), which cannot emit light itself and require a separate light source to display an image.

[3] A general LCD includes two panels provided with field-generating electrodes and a liquid crystal layer interposed therebetween. The LCD displays desired images by applying voltages to the field-generating electrodes to generate an electric field in the liquid crystal layer, and adjusting the magnitudes of the voltages to control the intensity of the electric field, so as to control the transmittance of light passing through the liquid crystal display. In this case, the light may be may provided from a separate artificial light source, or may be natural light.

[4] Meanwhile, a light source for an LCD generally includes a plurality of lamps, in which fluorescent lamps (such as external electrode fluorescent lamps (EEFLs) or cold cathode fluorescent lamps (CCFLs)) or light emitting diodes (LEDs) are used as a light source to uniformly transfer light to an entire liquid crystal panel from the real surface of the liquid crystal panel.

[5] The LCD, which is a light-receiving device, displays a screen by means of light irradiated from a backlight, so that the quality of the display screen is determined depending on the backlight. However, a backlight source has a problem in that luminance and color temperature deviation are caused due to external temperature, generation of heat within the display device, and irregularity of the characteristics of the light source. Such luminance and color temperature deviation are common phenomena in all light sources, and these cause degradation in the image quality of the LCD.

[6] Particularly, the biggest advantage of a light-emitting diode backlight for an LCD is to provide the best color quality desired by the user by combining light irradiated from red (R), green (G), and blue (B) light-emitting diodes and providing the light to the LCD. However, the light efficiency of the light-emitting diodes used as a backlight source largely varies depending on heat. As a result, the backlight source becomes susceptible to the internal heat generator and the external environment of the LCD, thereby upsetting the color balance.

[7] In order to prevent the image quality from being degraded due to the deviation of the backlight source, it is necessary to determine if the color coordinates and luminance of light irradiated to the panel of the LCD are identical to preset values by comparing them with each other and to compensate for the differences therebetween. Disclosure of Invention Technical Problem

[8] To this end, in the conventional technology, a color sensor is installed within a backlight unit to measure the luminance and color temperature of light from a backlight source, and to correct the luminance and color temperature. However, since the color sensor cannot control the quantity of introduced light, it is difficult to control the level of a converted electrical signal, and moreover, the color sensor has a disadvantage in that it is susceptible to temperature variation. Accordingly, when a color sensor is installed within a backlight unit, there are problems in that it is difficult to determine the position of the sensor, and malfunctioning of the sensor frequently occurs due to temperature variation within the backlight unit. Technical Solution

[9] Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior art, and the present invention provides a luminance and color temperature control system for a light-emitting diode backlight unit, which measures the luminance and color temperature of the light-emitting diode backlight for a liquid crystal display (LCD) by means of a video camera which can easily condense light, and corrects unevenness of the luminance and color temperature distribution according to the locations of sub-regions and the individual deviations of light-emitting diodes forming the backlight.

[10] In accordance with a first aspect of the present invention, there is provided a luminance and color temperature control system of a light-emitting diode backlight unit, the system including: a backlight unit including multiple sub-regions each of which includes a predetermined number of light-emitting diodes, the backlight unit outputting light with specific luminance and specific color temperature by causing the light-emitting diodes included in the respective sub-regions to emit light according to powers input to the respective sub-regions; a light detector installed outside of the backlight unit, the light detector including an image pickup device which detects light output from the backlight unit and converts the detected light into an electrical signal, detecting luminance and color temperature distribution of light output from the respective sub-regions based on light output from the backlight unit, and outputting a detection signal which has a level corresponding to luminance and color temperature of light output from the respective sub-regions; and a controller comparing the level of the detection signal output from the light detector with a prestored reference level corresponding to prestored predetermined luminance and color temperature, and outputting a control signal to control power input to the respective sub-regions in order to change luminance and color temperature of light output from the respective sub- regions based on a result of the comparison.

[11] Preferably, the luminance and color temperature control system of the light-emitting diode backlight unit according to the first aspect of the present invention may further include a driving unit for receiving the control signal output from the controller, and supplying the respective sub-regions with power corresponding to the control signal.

[12] Preferably, in the luminance and color temperature control system of the light- emitting diode backlight unit according to the first aspect of the present invention, when the prestored predetermined luminance and color temperature are reset, the controller may cooperate with an external terminal equipped with a relevant application.

[13] Preferably, in the luminance and color temperature control system of the light- emitting diode backlight unit according to the first aspect of the present invention, the controller may include: a real-time compensation control signal generator for comparing the level of the detection signal output in real time from the light detector with the reference level corresponding to the prestored predetermined luminance and color temperature, and outputting a Control signal to control power input to at least one specific sub-region of the multiple sub-regions based on a result of the comparison in order to accord luminance and color temperature of light output from said at least one specific sub-region with luminance and color temperature corresponding to the reference level; a sub-region compensation control signal generator for receiving the detection signal from the light detector in cooperation with the real-time compensation control signal generator according to a number of the sub-regions, comparing the level of the detection signal with the reference level corresponding to the prestored predetermined luminance and color temperature, and outputting a Control signal to control power input to the respective sub-regions based on a result of the comparison in order to accord luminance and color temperature of light output from the respective sub- regions with luminance and color temperature corresponding to the reference level; a data storage unit for storing the detection- signal reference level; and an interface unit for providing an interface with the light detector.

[14] Preferably, in the luminance and color temperature control system of the light- emitting diode backlight unit according to the first aspect of the present invention, the controller may further include an interface unit for providing an interface with the external terminal.

[15] Preferably, in the luminance and color temperature control system of the light- emitting diode backlight unit according to the first aspect of the present invention, the interface unit may cooperate with the external terminal in an RS-232C scheme.

[16] Preferably, in the luminance and color temperature control system of the light- emitting diode backlight unit according to the first aspect of the present invention, the backlight unit may be configured with the multiple sub-regions obtained by dividing the backlight unit in horizontal and vertical directions, symmetrical sub-regions located at mutually symmetrical positions may be grouped among the multiple sub-regions, and power input to the grouped symmetrical sub-regions may be controlled by an equal control signal.

[17] In accordance with a second aspect of the present invention, there is provided a luminance and color temperature control system of a light-emitting diode backlight unit, the system including: a backlight unit including multiple sub-regions, each of which includes a predetermined number of light-emitting diodes, the backlight unit outputting light with specific luminance and specific color temperature by causing the light-emitting diodes included in the respective sub-regions to emit light according to powers input to the respective sub-regions; a light detector installed in an interior of the backlight unit, the light detector including an image pickup device which detects light output from the backlight unit and converts the detected light into an electrical signal, detecting luminance and color temperature distribution of light output from the respective sub-regions based on light output from the backlight unit, and outputting a detection signal which has a level corresponding to luminance and color temperature of light output from the respective sub-regions; and a controller comparing the level of the detection signal output from the light detector with a prestored reference level corresponding to prestored predetermined luminance and color temperature, and outputting a control signal to control power input to the respective sub-regions in order to change luminance and color temperature of light output from the respective sub- regions based on a result of the comparison.

[18] Preferably, the luminance and color temperature control system of the light-emitting diode backlight unit according to the second aspect of the present invention may further include a driving unit for receiving the Control signal output from the controller, and supplying the respective sub-regions with power corresponding to the Control signal.

[19] Preferably, in the luminance and color temperature control system of the light- emitting diode backlight unit according to the second aspect of the present invention, the light detector may include a camera, which is located in an interior of the backlight unit so as to detect light output from the backlight unit and to output the detection signal corresponding to luminance and color temperature of light output from the respective sub-regions, and more preferably, the camera may be a small-sized video camera.

[20] Preferably, in the luminance and color temperature control system of the light- emitting diode backlight unit according to the second aspect of the present invention, the controller may include: a real-time compensation control signal generator for comparing the level of the detection signal output in real time from the light detector with the reference level corresponding to the prestored predetermined luminance and color temperature, and outputting a Control signal to control power input to the respective sub-regions based on a result of the comparison in order to accord luminance and color temperature of light output from at least one specific sub-region of the multiple sub-regions with luminance and color temperature corresponding to the reference level; a data storage unit for storing the detection- signal reference level; and an interface unit for providing an interface with the light detector.

[21] Preferably, in the luminance and color temperature control system of the light- emitting diode backlight unit according to the second aspect of the present invention, the backlight unit may be configured with the multiple sub-regions obtained by dividing the backlight unit in horizontal and vertical directions, symmetrical sub- regions located at mutually symmetrical positions may be grouped among the multiple sub-regions, and power input to the grouped symmetrical sub-regions may be controlled by an equal control signal.

Advantageous Effects

[22] According to the luminance and color temperature control system of the light- emitting diode backlight unit of the present invention, a backlight unit is divided into multiple sub-regions, specified luminance and color temperature are set according to each of the divided sub-regions, and light output according to each sub-region is continuously monitored through a camera, so that it is possible to minutely control the quantity of light output from each sub-region, which can be increased or decreased.

[23] In addition, in measuring the quantity of light output from the light-emitting diode backlight unit, a position where the backlight unit is to be installed can be freely selected, not only inside of the backlight unit, but also outside of it, by employing a camera which is not influenced by heat generated by light-emitting diodes. Brief Description of the Drawings

[24] The accompanying drawings included in this specification illustrate exemplary embodiments of the invention, and together with the description serve to provide a better understanding of the technical aspects of the present invention, and are not meant to limit the scope of the invention, in which:

[25] FIG. 1 is a block diagram schematically illustrating the configuration of a luminance and color temperature control system of a light-emitting diode backlight unit according to a first embodiment of the present invention;

[26] FIGs. 2 to 4 are views illustrating the configuration of the region of the light-emitting diode backlight unit according to the first embodiment of the present invention;

[27] FIG. 5 is a block diagram schematically illustrating the configuration of a controller according to the first embodiment of the present invention;

[28] FIG. 6 is a block diagram schematically illustrating the configuration of a luminance and color temperature control system of a light-emitting diode backlight unit according to a second embodiment of the present invention; and

[29] FIG. 7 is a block diagram schematically illustrating the configuration of a controller according to the second embodiment of the present invention. Best Mode for Carrying Out the Invention

[30] Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

[31] FIG. 1 is a block diagram schematically illustrating the configuration of a luminance and color temperature control system of a light-emitting diode backlight unit according to a first embodiment of the present invention.

[32] As shown in FIG. 1, the system according to the first embodiment of the present invention includes: a backlight unit 100 containing a plurality of red (R), green (G), and blue (B) light-emitting diodes; a light detector 200 for detecting light output from the backlight unit 100 and generating a detection signal according to the quantity of light detected thereby; a controller 300 for outputting a control signal according to a level of the detection signal; and a driving unit 400 for receiving the control signal and supplying each sub-region of the backlight unit 100 with power corresponding to the control signal.

[33] The backlight unit 100 is divided into multiple sub-regions, each of which includes a predetermined number of light-emitting diodes, and each of the divided sub-regions outputs light according to power input from the driving unit 400, so as to maintain specific luminance and color temperature. For example, as shown in FIG. 2, the screen of the backlight unit 100 may be divided into 15 sub-regions Al to A15, that is, may be divided into three rows in the vertical direction and into five columns in the horizontal direction, in which each of the divided sub-regions Al to A15 is controlled to have specific luminance and color temperature according to a power which is output from the driving unit 400 corresponding to a control signal generated by the controller 300. In this case, preferably, the present invention is implemented such that the unit number of the sub-regions Al to A15 actually controlled upon controlling the quality of light of the sub-regions Al to A15 can vary depending on the setting of the operator. For example, as shown in FIG. 3, the present invention may be implemented such that sub-regions located at mutually corresponding positions can be controlled by a single control signal. That is, the 15 divided sub-regions may be grouped into six unit regions, that is, into sub-region "A", sub-regions "B_l" and "B_2", sub-regions "C_l" and "C_2", sub-regions "D_l" and "D_2", sub-regions "E_l" and "E_2", and sub- regions "F_l" and "F_2", by taking into consideration the vertical and horizontal correlations of the screen, thereby reducing luminance and color temperature control signals actually required for the backlight from 15 to 6, so that it becomes possible to control the backlight through a group of 6 PWM signals. Otherwise, as shown in FIG. 4, the nine sub-regions into which the screen is divided may be grouped into three unit regions, that is, into sub-region "A", sub-regions "B_l" to "B_4", and sub-regions " C_l" to "C_4" by taking into consideration the vertical and horizontal correlations of the screen, thereby reducing luminance and color temperature control signals actually required for the backlight from nine to three, so that it becomes possible to control the backlight through 3 PWM signals. Accordingly, as shown in FIGs. 3 and 4, although the number of sub-regions increases, it is possible to significantly reduce the number of required control signals by taking into consideration the vertical and horizontal correlations of the screen.

[34] The light detector 200 is installed outside of the backlight unit 100, and includes a camera which detects light components irradiated from the backlight unit 100 and outputs the detection signal corresponding to luminance and color temperature distribution according to multiple sub-regions. Also, the camera can control the quantity of light introduced from the backlight unit 100 by a light quantity control function.

[35] In other words, the camera is configured to detect only color levels according to light introduced from the backlight unit 100 by applying an open loop feed scheme without white balance. In this case, the sizes of the levels of colors of the Light-emitting diodes, which are introduced into the camera, can be controlled by the light quantity control function. Herein, the width of color levels to be controlled is limited within an input voltage range of an amplifier. For reference, in a camera converting an optical signal into an electrical signal, the white balance designates a reference point for converting an optical signal into an electrical signal. [36] Accordingly, when the camera applied to the light detector 200 is installed outside of the backlight unit 100, the camera can easily condense light irradiated from the backlight and detect the quantity of light by the light quantity control function, even without taking into consideration the illumination angle of the backlight.

[37] The controller 300 identifies luminance and color temperature of each of multiple sub-regions according to the levels of detection signals output from the light detector 200, outputs control signals to control the quantity of light output from each sub- region, and stores a detection- signal reference level corresponding to luminance and color temperature set by an operator.

[38] In more detail, as shown in FIG. 5, the controller 300 includes a real-time compensation control signal generator 310, a sub-region compensation control signal generator 320, a data storage unit 330, and an interface unit 340. The real-time compensation control signal generator 310 receives a detection signal output in real time from the light detector 200, identifies luminance and color temperature of at least one specified sub-region of the multiple sub-regions from the level of the detection signal, compares the level of the detection signal with the stored detection- signal reference level, and outputs a control signal to control a power input to each sub-region in order to adjust the luminance and color temperature of light output from each sub-region according to a result of the comparison. The sub-region compensation control signal generator 320 receives a detection signal from the light detector 200 in cooperation with the real-time compensation control signal generator 310 according to the number of sub-regions, identifies luminance and color temperature according to each of the sub-regions, and outputs a control signal to control the quantity of light output from each of the sub-regions in order to increase or decrease the quantity of light based on the stored detection- signal reference level. The data storage unit 330 stores the detection- signal reference level. The interface unit 340 provides an interface between the controller 300 and an external terminal 500 equipped with an application for luminance and color temperature setup when an operator sets up the luminance and color temperature, and an interface between the controller 300 and the light detector 200.

[39] Preferably, the real-time compensation control signal generator 310 and sub-region compensation control signal generator 320 can be pulse- width modulation (PWM) signal generators, which generate the control signals to control powers input to the respective sub-regions through pulse width modulation. That is, the real-time compensation control signal generator 310 and sub-region compensation control signal generator 320 output the control signals, which can be PWM signals, so as to compensate for a variation in the luminance and color temperature of the respective sub-regions included in the backlight unit 100 through control of the pulse widths of powers output from the driving unit 400. The real-time compensation control signal generator 310 may be constructed by applying, for example, a "U-processor," and the sub-region compensation control signal generator 320 may be constructed by applying an "FPGA" which is a programmable logic.

[40] In addition, the sub-region compensation control signal generator 320 is constructed to output PWM signals of more channels (M CHs, wherein "M" is an integer of 1, 2, 3, ..., M; M>N) than those output from the real-time compensation control signal generator 310. In a luminance and color temperature setting mode according to each sub-region by an operator, the sub-region compensation control signal generator 320 can output PWM signals of multiple channels in cooperation with the real-time compensation control signal generator 310. In contrast, in a temporal mode, by driving only the real-time compensation control signal generator 310, which outputs PWM signals of less channels (N CHs, wherein "N" is an integer 1, 2, 3, ..., N; N<M) than those output from the sub-region compensation control signal generator 320, the luminance and color temperature of one or more specified sub-regions of multiple sub-regions are identified in real time, thereby monitoring the luminance and color temperature of the backlight unit 100 on the basis of the detection- signal reference level stored in the data storage unit 330.

[41] Meanwhile, the data storage unit 330 includes a typical "EEPROM." The interface unit 340 includes an RS-232C communication chip for communication with the external terminal 500, e.g., a PC or external adjusting device, so that the controller 300 can cooperate with the external terminal 500 in the RS-232C scheme.

[42] As described above, the luminance and color temperature control system of the light- emitting diode backlight unit according to the first embodiment of the present invention is driven in the sub-region setting mode for designating luminance and color temperature according to each sub-region by detecting light components output from the backlight unit 100 by means of a camera (i.e., the light detector 200) installed outside of the backlight unit 100, and in the temporal mode for correcting luminance and color temperature, which vary depending on temperature in real time.

[43] That is, in the sub-region setting mode, the operator designates luminance and color temperature according to each sub-region by outputting PWM signals corresponding to the luminance and color temperature for each of the multiple sub-regions included in the backlight unit 100 by means of the external terminal 500, in which a detection- signal reference levels according to the designated luminance and color temperature are stored in the data storage unit 330.

[44] In addition, in the temporal mode, the system continuously monitors the output light of the backlight unit 100, compares the result of the monitoring with the detection- signal reference level stored in the data storage unit 330, and controls the quantity of the output light of each sub-region, which increases or decreases due to temporal variation according to temperature and time.

[45] Hereinafter, the luminance and color temperature control system of a light-emitting diode backlight unit according to a second embodiment of the present invention will be described with reference to FIG. 6. FIG. 6 is a block diagram schematically illustrating the configuration of the luminance and color temperature control system of the backlight unit according to the second embodiment of the present invention.

[46] As shown in FIG. 6, the system according to the second embodiment of the present invention includes a backlight unit 100 containing a plurality of Light-emitting diodes, a light detector 200 for detecting light output from the backlight unit 100 and generating detection signal according to the quantity of light, a controller 300 for outputting a control signal according to the level of the detection signal, and a driving unit 400 for receiving the control signal and supplying each sub-region of the backlight unit 100 with power corresponding to the control signal.

[47] The backlight unit 100 according to the second embodiment of the present invention has the same configuration as that according to the first embodiment of the present invention, so a detailed description thereof will be omitted.

[48] The light detector 200 is configured with a small-sized video camera which is installed in the interior of the backlight unit 100 so as to detect the quantity of light irradiated from the backlight unit 100 and to output the detection signal corresponding to luminance and color temperature distribution according to each of multiple sub- regions. The small-sized video camera employed as the light detector 200 can control the quantity of light introduced from the backlight unit 100 by a light quantity control function, and is unsusceptible to variations in the interior temperature of the backlight unit 100. Accordingly, when the small-sized video camera according to the present invention is installed in the interior of the backlight unit based on the easiness of light condensation through the light quantity control function, a position where the small- sized video camera is to be installed can be freely selected. Meanwhile, similar to the camera employed in the first embodiment of the present invention, the small-sized video camera according to the second embodiment of the present invention is configured to detect only color levels according to light introduced from the backlight unit 100 by applying an open loop feedback scheme without white balance. The operation of the small-sized video camera according to such a configuration is the same as that of the camera employed in the first embodiment of the present invention.

[49] The controller 300 identifies luminance and color temperature for each of multiple sub-regions according to the level of detection signal output from the light detector 200, compares the detection signal with a detection-signal reference level prestored corresponding to predetermined luminance and color temperature, and outputs a control signal to control the quantity of output light of each sub-region, which can be increased or decreased. That is, as shown in FIG. 7, the controller 300 includes a realtime compensation control signal generator 310, a data storage unit 330, and an interface unit 340. The real-time compensation control signal generator 310 receives a detection signal output in real time from the light detector 200, compares the level of the received detection signal with a reference level prestored corresponding to predetermined luminance and color temperature, and outputs Control signals to control powers input to the respective sub-regions in order to change luminance and color temperature of light output from the respective sub-regions based on a result of the comparison. The data storage unit 330 stores the detection- signal reference level. The interface unit 340 provides an interface between the controller 300 and the light detector 200.

[50] As described above, the system according to the second embodiment of the present invention measures a variation in luminance and color temperature of the backlight unit, which is caused by temperature and/or temporal variation, in real time, by means of a very small video camera installed in the interior of the backlight unit 100, and repeats to sense and compensate for the variation through the controller 300, thereby maintaining preset luminance and color temperature. In other words, by continuously monitoring light output from the backlight unit 100 and comparing the results of the monitoring with a detection-signal reference level which has been stored, it is possible to control the quantity of output light of each sub-region, which increases or decreases according to temporal variation.

[51] As described above, according to the luminance and color temperature control system of the light-emitting diode backlight unit of the present invention, a backlight unit is divided into multiple sub-regions, specified luminance and color temperature are set according to each of the divided sub-regions, and light output according to each sub-region is continuously monitored through a camera, so that it is possible to minutely control the quantity of light output from each sub-region, which can be increased or decreased.

[52] In addition, in measuring the quantity of light output from the light-emitting diode backlight unit, a position where the backlight unit is to be installed can be freely selected, not only inside of the backlight unit, but also outside of it, by employing a camera which is not influenced by heat generated by light-emitting diodes.

[53] Although an exemplary embodiment of the present invention has been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

Claims
[1] A luminance and color temperature control system of a light-emitting diode backlight unit, the system comprising: a backlight unit including multiple sub-regions each of which comprises a predetermined number of light-emitting diodes, the backlight unit outputting light with specific luminance and specific color temperature by causing the light- emitting diodes included in the respective sub-regions to emit light according to powers input to the respective sub-regions; a light detector installed outside of the backlight unit, the light detector comprising an image pickup device which detects light output from the backlight unit and converts the detected light into an electrical signal, detecting luminance and color temperature distribution of light output from the respective sub-regions based on light output from the backlight unit, and outputting a detection signal which has a level corresponding to luminance and color temperature of light output from the respective sub-regions; and a controller comparing the level of the detection signal output from the light detector with a prestored reference level corresponding to prestored predetermined luminance and color temperature, and outputting a control signal to control power input to the respective sub-regions in order to change luminance and color temperature of light output from the respective sub-regions based on a result of the comparison.
[2] The system as claimed in claim 1, further comprising a driving unit for receiving the Control signal output from the controller, and supplying the respective sub- regions with power corresponding to the Control signal.
[3] The system as claimed in claim 1, wherein when the prestored predetermined luminance and color temperature are reset, the controller cooperates with an external terminal equipped with a relevant application.
[4] The system as claimed in claim 1, wherein the controller comprises: a real-time compensation control signal generator for comparing the level of the detection signal output in real time from the light detector with the reference level corresponding to the prestored predetermined luminance and color temperature, and outputting a Control signal to control power input to at least one specific sub-region of the multiple sub-regions based on a result of the comparison in order to accord luminance and color temperature of light output from said at least one specific sub-region with luminance and color temperature corresponding to the reference level; a sub-region compensation control signal generator for receiving the detection signal from the light detector in cooperation with the real-time compensation control signal generator according to a number of the sub-regions, comparing the level of the detection signal with the reference level corresponding to the prestored predetermined luminance and color temperature, and outputting a Control signal to control power input to the respective sub-regions based on a result of the comparison in order to accord luminance and color temperature of light output from the respective sub-regions with luminance and color temperature corresponding to the reference level; a data storage unit for storing the detection- signal reference level; and an interface unit for providing an interface with the light detector.
[5] The system as claimed in claim 3, wherein the controller further comprises an interface unit for providing an interface with the external terminal.
[6] The system as claimed in claim 5, wherein the interface unit cooperates with the external terminal in an RS-232C scheme.
[7] The system as claimed in claim 1, wherein the backlight unit is configured with the multiple sub-regions obtained by dividing the backlight unit in horizontal and vertical directions, symmetrical sub-regions located at mutually symmetrical positions are grouped among the multiple sub-regions, and power input to the grouped symmetrical sub-regions is controlled by an equal control signal.
[8] A luminance and color temperature control system of a light-emitting diode backlight unit, the system comprising: a backlight unit including multiple sub-regions, each of which comprises a predetermined number of light-emitting diodes, the backlight unit outputting light with specific luminance and specific color temperature by causing the light- emitting diodes included in the respective sub-regions to emit light according to powers input to the respective sub-regions; a light detector installed in an interior of the backlight unit, the light detector comprising an image pickup device which detects light output from the backlight unit and converts the detected light into an electrical signal, detecting luminance and color temperature distribution of light output from the respective sub-regions based on light output from the backlight unit, and outputting a detection signal which has a level corresponding to luminance and color temperature of light output from the respective sub-regions; and a controller comparing the level of the detection signal output from the light detector with a prestored reference level corresponding to prestored predetermined luminance and color temperature, and outputting a control signal to control power input to the respective sub-regions in order to change luminance and color temperature of light output from the respective sub-regions based on a result of the comparison.
[9] The system as claimed in claim 8, further comprising a driving unit for receiving the Control signal output from the controller, and supplying the respective sub- regions with power corresponding to the Control signal.
[10] The system as claimed in claim 8, wherein the light detector comprises a camera, which is located in an interior of the backlight unit so as to detect light output from the backlight unit and to output the detection signal corresponding to luminance and color temperature of light output from the respective sub-regions.
[11] The system as claimed in claim 10, wherein the camera includes a small-sized video camera.
[12] The system as claimed in claim 8, wherein the controller comprises: a real-time compensation control signal generator for comparing the level of the detection signal output in real time from the light detector with the reference level corresponding to the prestored predetermined luminance and color temperature, and outputting a Control signal to control power input to the respective sub-regions based on a result of the comparison in order to accord luminance and color temperature of light output from at least one specific sub- region of the multiple sub-regions with luminance and color temperature corresponding to the reference level; a data storage unit for storing the detection- signal reference level; and an interface unit for providing an interface with the light detector.
[13] The system as claimed in claim 8, wherein the backlight unit is configured with the multiple sub-regions obtained by dividing the backlight unit in horizontal and vertical directions, symmetrical sub-regions located at mutually symmetrical positions are grouped among the multiple sub-regions, and power input to the grouped symmetrical sub-regions is controlled by an equal control signal.
PCT/KR2007/004031 2007-02-12 2007-08-23 Luminance and color temperature control system of led backlight unit WO2008099997A1 (en)

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KR1020070014332A KR100861461B1 (en) 2007-02-12 2007-02-12 Illumination and color temperature control system of r.g.b led back light unit

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KR20080075327A (en) 2008-08-18

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