JP2006119268A - Back light adjusting system, program, and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve color unevenness adjusting performance of an LED backlight system. <P>SOLUTION: LED modules 5, 6, 7 and 8 in each of which LEDs of R, G and B are arranged are disposed in point symmetry with respect to a screen center point of an LCD panel 2 and driven by LED drivers 9, 10, 11 and 12, respectively, and electric power values supplied thereto are individually controlled. Each ray of R, G and B from the respective LED modules is color-mixed by a light guide plate 1 and a white ray as a backlight is obtained. When a screen is adjusted, a color sensor 18 detecting luminance/chromaticity is attached to the screen center and color unevenness can be reduced by adjusting the same luminance/chromaticity for every LED module 5, 6, 7 and 8 when viewed from the screen center based on the result of the color sensor. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a backlight adjustment system for a transmitted light display type image display device having a backlight such as a liquid crystal display device, a program used in the system, and a recording medium on which the program is recorded.

6 is described in, for example, 43.3: High-efficiency Slim LED Backlight System with Mixing Light Guide, Youri Martynov, Huub Konijn, Nicola Pfeffer, Simon Kuppens and Wim Timmers, and Lumileds Lighting described in SID2003 Proceedings (SID03 Digest) It is a block diagram which shows typically the part regarding the LED backlight system in the conventional image display apparatus which is.
In FIG. 6, reference numeral 1 denotes a light guide plate, to which a diffusion sheet and a reflection sheet (not shown) are attached, and R (red), G (green), and B (blue) from the LED module 3 described later. By introducing each color light and mixing the colors, white light as a backlight is obtained. Reference numeral 2 denotes an LCD (liquid crystal) panel that is mounted on the light guide plate 1 and has a large number of LCD elements with R, G, and B color filters attached to each pixel on the surface. The white light is separated by a filter and only R, G, and B color light is transmitted. The LCD elements constituting each pixel are driven by a liquid crystal drive circuit (not shown), and an image according to an image signal supplied to the drive circuit is displayed. Reference numeral 3 denotes an LED module that serves as a light source for a conventional LED backlight system. A plurality of LEDs (Light Emitting Diodes) that emit light at R, G, and B wavelengths are connected in series according to color, and the line direction It is comprised by the LED group arranged in.

  Reference numeral 4 denotes an LED driver for driving the LED module 3, which is composed of a 3-channel LED driver for driving each of the R, G, and B LED groups. This LED driver 4 is driven by a drive circuit (not shown) provided in the image display device, and is driven by PWM (Pulse Width Modulation) by a preset current value, and PWM ON / OFF switching is performed. The input power to each LED group is controlled according to the duty ratio.

  In the above configuration, light emitted from each of the R, G, and B LED groups of the LED module 3 is guided into the light guide plate 1 and mixed into white light. The white light passes through the liquid crystal panel 2 to display a color image. Here, when the ratio of the power input to each LED group of R, G, and B and the total power are changed, the chromaticity (color temperature) and luminance of white change. Regarding the brightness and chromaticity of white, different settings are made according to the environment, application, and purpose of using the image display apparatus.

Conventionally, a technique for controlling the light emission timings of R, G, and B of an image display apparatus having a backlight has been proposed (for example, see Patent Document 1). In addition, a technique using a plurality of LED light sources as in the present invention described later has been proposed (see, for example, Patent Documents 2, 3, and 4).
Japanese Patent No. 3371200 JP 2001-147431 A JP 2002-350846 A JP 2003-107472 A

  In the conventional LED backlight system configured as described above, since the backlight light source is a point light source, color unevenness due to the mixed color residue of the three colors of R, G, and B, and each LED constituting the LED module 3 Due to variations in brightness and emission wavelength, variation in drive conditions (current), etc., the color unevenness is large compared to a CCFL (Cold Cathode Fluorescent Lamp) type backlight system using a conventional cold cathode tube. For this reason, there is no problem when applied to applications where the required specifications for color irregularity performance such as TV are not so strict, but there are requirements for color irregularity performance for displays used in DTP (Desk Top Publishing) and pre-printing processes. It has been a problem when applied to severe applications. In addition, when applying to all applications, the light emission brightness and wavelength selection conditions of the LEDs used in the LED module are relaxed and cost reduction is a trade-off with color unevenness performance. .

  In addition, the above-mentioned Patent Document 1 eliminates luminance unevenness and color unevenness by controlling the light emission timings of R, G, and B, and the above-mentioned Patent Document 2 uses a plurality of LED light sources at the corners of the screen. By arranging them in this way, the degree of freedom of the connector position for connecting the printed circuit board is obtained particularly in the case of a large screen. In Patent Documents 3 and 4, a decrease in brightness is suppressed by using a plurality of LED light sources. However, in each of the above documents, no consideration is given to color unevenness caused by variations in R, G, and B LEDs themselves, variations in drive current, and the like. Will essentially have.

  The present invention improves the color unevenness performance due to the variation of the LED and current of the conventional LED backlight system described above, and can be applied to applications where the required specifications regarding the color unevenness performance are strict, or the LED used for the backlight The purpose is to reduce the cost by preventing the color unevenness performance from significantly deteriorating even if the selection conditions are relaxed.

  An image display device according to the present invention introduces a screen section for displaying an image, a plurality of point light source groups each including a plurality of point light sources having different light emission colors, and light emission of the plurality of point light source groups. An image display device comprising: a light guide plate that mixes colors and uses the mixed light as a backlight of the screen unit; and a control unit that independently controls power supplied to the plurality of point light source groups; It comprises a screen adjustment device that adjusts the power supplied by the control unit to each point light source group so that the luminance and / or chromaticity of the backlight is uniform.

  The program according to the present invention introduces light emitted from a plurality of point light source groups, each of which has a plurality of point light sources having different light emission colors, into a light guide plate and mixes the light, and displays the mixed color light on a screen backlight for displaying an image. And a program used for adjusting the backlight of the image display device that controls each point light source group independently, and a lighting process for sequentially lighting each point light source group, In the lighting period, the computer executes a detection process for detecting the luminance and / or chromaticity of the center of the screen and an adjustment process for adjusting the power supplied to each point light source group based on the detection value. .

  A computer-readable recording medium according to the present invention records the program.

  According to the present invention, it is particularly suitable for applications where the required specifications regarding color unevenness performance are strict, and when applied to all applications, the light emission luminance and wavelength selection conditions of the LEDs used in the LED module The problem of trade-off with color unevenness performance in the case of reducing the cost and reducing the cost can be solved.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 2 is a configuration diagram schematically showing a part related to the LED backlight system in the image display device according to the embodiment of the present invention.
In FIG. 2, reference numeral 1 denotes a light guide plate, which has a diffusion sheet and a reflection sheet (not shown) attached thereto, and introduces R, G, and B color light from LED modules 5, 6, 7, and 8, which will be described later. By mixing the colors, white light as a backlight is obtained. Reference numeral 2 denotes an LCD panel as a screen unit that is attached to the light guide plate 1 in an overlapping manner. On the surface of the LCD panel, a large number of LCD elements with R, G, and B color filters attached are arranged for each pixel. The white light is dispersed by the color filter and only the R, G, and B color lights are transmitted. The LED elements constituting each pixel are driven by a liquid crystal driving circuit (not shown), and an image according to an image signal supplied to the driving circuit is displayed.

  Reference numerals 5, 6, 7, and 8 denote LED modules as point light source groups that serve as light sources of the LED backlight system according to the present embodiment. In each module, point light sources that emit light at wavelengths of R, G, and B, respectively. A plurality of LEDs (Light Emitting Diodes) are connected in series for each emission color, and are configured by LED groups arranged in the line direction. The LED modules 5, 6, 7, and 8 are attached at positions that are point-symmetric with respect to the screen center point of the LCD panel 2. Reference numerals 9, 10, 11, and 12 denote LED drivers that drive the LED modules 5, 6, 7, and 8, respectively, and are configured by 3-channel LED drivers that drive the R, G, and B LED groups. An LED that emits white light may be used.

FIG. 1 is a block diagram showing a backlight adjustment system according to the present embodiment. Parts corresponding to those in FIG.
In FIG. 1, reference numeral 13 denotes a screen adjustment device comprising a computer system, and 20 denotes an image display device whose backlight is adjusted by the screen adjustment device 13.
In the screen adjustment device 13, 14 is a luminance / chromaticity adjustment unit in which application software is incorporated, 15 is a communication function unit composed of DDC / CI (Display Data Channel Command Interface), and 16 is a graphic system including the communication function unit 15. (Graphic accelerator) 17 is a USB interface.

  In the image display device 20, reference numeral 18 denotes a color sensor connected to the USB interface 17, which is detachably attached to the center of the screen of the LCD panel 2. A control unit 19 includes LED drivers 9, 10, 11, and 12, an MPU 21 that controls each LED driver, and a nonvolatile memory 22.

FIG. 3 is a flowchart showing the operation of the application software incorporated in the brightness / chromaticity adjustment unit 14 of the screen adjustment device 13. The operation of the backlight adjustment system according to the present embodiment will be described below with reference to FIG.
When adjusting the screen in a factory or the like, first, the mounting position of the color sensor 18 is displayed on the screen of the LCD panel 2. The attachment position is such that the light receiving portion of the color sensor 18 is at the center position of the screen (ST1). Next, whether or not the user has completed the installation of the color sensor 18 is confirmed by inputting from a keyboard (not shown) of the computer system (ST2). When the installation is completed, an all white screen is displayed on the LCD panel 2 (ST3). Next, the setting value of the backlight luminance is set to a predetermined intermediate value, and the white balance (balance of driving power of the R, G, and B LEDs) is also set to a predetermined value. For example, the duty ratios of the drive PWM operations of the LED drivers 9, 10, 11, and 12 are all set to 70% (ST4).

  Next, the LED modules 5, 6, 7, and 8 are individually turned on sequentially in the order indicated by (1), (2), (3), and (4) in FIG. 4 and attached to the center of the screen during each lighting period. Luminance and chromaticity are measured by the color sensor 18 (ST5). At this time, the duty ratio of the PWM operation is still set to 70% in ST4, for example. Next, as a result of the above sequential lighting and measurement, the LED module with the darkest brightness is identified, the drive power of the R and B LEDs of that LED module is adjusted, and the brightness and chromaticity (color temperature) of white are specified. Adjust so that the value is within the range (ST6). The luminance adjustment target value at this time is 1/4 of 50 cd / m 2 when the maximum luminance of the LCD panel 3 is 200 cd / m 2. The target value of chromaticity is, for example, 6500K (x = 0.313, y = 0.329).

  Next, for the remaining three LED modules, using the brightness and chromaticity adjusted in ST5 above as the target values, the drive power of the R and B LEDs is adjusted in the same way to obtain white brightness and chromaticity (color temperature). ) Is adjusted to a predetermined value range (ST7). The above adjustment result (backlight drive duty ratio) data is recorded in the nonvolatile memory 22 (ST8). Thereafter, the image display device 20 reduces the unevenness of color and luminance by controlling the power supplied to the LED drivers 9, 10, 11 and 12 by the MPU 21 based on the data recorded in the nonvolatile memory 22, respectively. Screen can be obtained.

  As described above, according to the present embodiment, there is a variation in luminance and chromaticity of each LED constituting the LED modules 5, 6, 7, and 8, and even when this is a cause of occurrence of color unevenness, Since each of the four LED modules 5, 6, 7, and 8 is adjusted to the same luminance and chromaticity as viewed from the center of the screen, the effect of reducing color unevenness and luminance unevenness can be obtained.

  FIG. 5 shows that the backlight drive system according to the present embodiment is used so that the PWM drive duty ratios of the R, G, and B LEDs are the same for each color for the four LED modules 5, 6, 7, and 8. ΔCab between the center of the screen and the four peripheral points when it is set, that is, when the color / brightness unevenness adjustment by the backlight is not performed and when the brightness / color unevenness adjustment is performed according to the steps ST1 to ST8 in FIG. It is the result of measuring the average, maximum, and minimum values of (two-dimensional color difference in color space) and ΔEab (three-dimensional color difference in color space), respectively. As shown in the figure, both ΔCab and ΔEab become smaller after adjustment, and it can be seen that luminance and color unevenness are improved.

Next, a program according to the present embodiment and a recording medium for recording the program will be described.
A program as application software incorporated in the luminance / chromaticity adjustment unit 14 for the CPU of the computer system in the screen adjustment device 13 to execute the processing shown in the flowchart of FIG. 3 according to the configuration of the backlight adjustment system of FIG. Constitutes a program according to the invention.

  The recording medium for recording the program constitutes a computer-readable recording medium according to the present invention. As this recording medium, a magneto-optical disk, an optical disk, a semiconductor memory, a magnetic recording medium, and the like can be used, and these may be configured and used in ROM, RAM, CD-ROM, flexible disk, memory card, and the like.

  In addition, this recording medium can be programmed for a certain period of time, such as a volatile memory such as a RAM in a computer system as a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. The thing to hold is also included.

  The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. The transmission medium is a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line.

  The program may be for realizing part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, what is called a difference file (difference program) may be sufficient.

  Therefore, even when this program and recording medium are used in a system or apparatus different from the system or apparatus in FIG. 2 and the computer of the system or apparatus executes this program, the functions and effects described in the embodiment are equivalent. Functions and effects can be obtained, and the problems of the present invention can be solved.

It is a block diagram which shows the adjustment system of the LED backlight system by embodiment of this invention. It is a block diagram which shows the LED backlight system of the image display apparatus by embodiment of this invention. It is a flowchart which shows operation | movement of the adjustment system of the LED backlight system by embodiment of this invention. It is a block diagram which shows the attachment position of the color sensor of the adjustment system of an LED backlight system, and the light emission order of an LED module. It is a block diagram which shows the data of the brightness | luminance and color nonuniformity improvement effect of the LED backlight system by embodiment of this invention. It is a block diagram which shows the adjustment system of the conventional LED backlight system.

Explanation of symbols

1 Light guide plate 2 LCD panel (screen part)
5, 6, 7, 8 LED module (point light source group)
9, 10, 11, 12 LED driver 13 Screen adjustment device 18 Color sensor 19 Control unit 20 Image display device 21 MPU
22 Nonvolatile memory

Claims (8)

A screen for displaying images;
A plurality of point light source groups in which point light sources having a plurality of different emission colors are respectively arranged;
A light guide plate that introduces light emission of the plurality of point light source groups to mix colors, and uses the mixed light as a backlight of the screen unit;
An image display device comprising: a control unit that independently controls power supplied to the plurality of point light source groups;
A backlight adjustment system comprising a screen adjustment device that adjusts the power supplied from the control unit to each point light source group so that the luminance and / or chromaticity of the backlight in the screen unit is uniform. The screen adjustment device
A color sensor that is attached to the center of the screen and detects luminance and / or chromaticity;
An adjustment unit that sequentially lights each point light source group individually by the control unit, and adjusts the power that the control unit supplies to each point light source group based on the detection value of the color sensor in each lighting period; Backlight adjustment system characterized by that.   The backlight adjustment system according to claim 1, wherein the point light source group includes a plurality of light emitting diodes that emit different color lights.   The backlight adjustment system according to claim 1, wherein the screen unit includes a liquid crystal panel.   The backlight adjustment system according to claim 1, wherein the backlight using the mixed color light is white light.   The backlight adjustment system according to claim 1, wherein the plurality of point light source groups are arranged point-symmetrically with respect to a center of the screen. Introducing light from a plurality of point light source groups each having a plurality of point light sources having different emission colors into a light guide plate and mixing the colors, displaying an image on a screen using the mixed light as a backlight, and A program used for adjusting the backlight of the image display device configured to independently control the light source group,
A lighting process for lighting each point light source group individually in sequence,
A detection process for detecting the brightness and / or chromaticity of the center of the screen in each lighting period;
The program which makes a computer perform the adjustment process which adjusts the electric power supplied to each said point light source group based on the said detection value. A computer-readable recording medium on which the program according to claim 7 is recorded.

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