JP2006302570A - Lighting device and display device using this - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lighting device and a display device using the same capable of carrying out brightness correction in a short time with the use of visual characteristics of a human being. <P>SOLUTION: The lighting device comprises a plurality of LEDs with different emission colors R, G, B, a means each of setting a target brightness of each LED, a means each of detecting an actual brightness of each LED, a brightness correction means carrying out in travelling by time sharing brightness correction of each LED so that a difference of the target brightness and the actual brightness is decreased, and generates illumination light with a desired emission color by mixing irradiated light of each LED. The brightness correction means is so structured as to be equipped with a function of setting and changing separately travelling frequencies for brightness correction for each LED. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a lighting device and a display device using the same.

  Conventionally, a plurality of light emitting means having different light emission colors (for example, three light emitting diodes having red, green, and blue light emission colors) are used, and the light emitted from each light emitting means is mixed to obtain a desired light emission color. 2. Description of the Related Art Lighting devices that generate illumination light are widely used in general.

  As for the color correction of the lighting device, a conventional technique for correcting the color of the illumination light by controlling the luminance of each color based on a color table that defines the target luminance of each light emitting means is disclosed and proposed. (For example, see Patent Document 1).

As another conventional technique related to the present invention, a color correction system (for example, refer to Patent Document 2) that performs luminance correction so that the voltages generated in the photosensors by the respective light emitting means coincide with each other is disclosed and proposed. ing.
JP 2002-1000048 A1 JP 2000-148075 A

  Certainly, with the above-described conventional illumination device, it is possible to generate luminance light having a desired emission color by performing luminance correction for each light emitting means.

  However, it has been shown that the luminance correction of each light emitting means in the conventional lighting apparatus is performed for each color, and little attention has been paid to the luminance correction order and correction time for each color.

  Further, when performing luminance correction for each color as described above, the frequency of the clock that regulates the luminance correction operation has to be increased in order to shorten the time required for correction. For this reason, the conventional lighting device has a problem that power consumption is increased as the brightness correction is performed at higher speed.

  An object of this invention is to provide the illuminating device which can perform appropriate brightness | luminance correction in a short time, and a display apparatus using the same in view of said problem.

  In order to achieve the above object, a lighting device according to the present invention includes a plurality of light emitting means having different emission colors, target luminance setting means for setting a target luminance of each light emitting means, and actual luminance of each light emitting means. And a luminance correction unit for performing luminance correction for each light emitting unit so as to reduce the difference between the target luminance and the actual luminance. An illumination apparatus that generates illumination light having a desired emission color by mixing, wherein the brightness correction unit performs brightness correction for each light emission unit while traveling in a time-sharing manner, and for each light emission unit A configuration (first configuration) is provided that includes a function for setting / changing the cyclic frequency of luminance correction.

  With such a configuration, it is possible to perform flexible and appropriate luminance correction in accordance with an error amount between the target luminance and the actual luminance, a user operation, or the like.

  Moreover, if the cyclic frequency of luminance correction is set appropriately, the color of illumination light can be brought close to a desired emission color in a shorter time than in the past due to human visual characteristics.

  For example, in the lighting device having the first configuration, the light emitting means is three light emitting diodes having red, green, and blue light emission colors, and the luminance correcting means emits red light and blue light, respectively. A configuration (second configuration) in which the cyclic frequency of luminance correction is set / changed for each light emitting diode so that the luminance correction of the light emitting diode emitting green light is preferentially performed over the luminance correction of the light emitting diode. Good.

  In this way, if the luminance correction of each light emitting means is performed in the priority order in consideration of human visual characteristics, the luminance correction is apparently speeded up without the need for clock-up that increases power consumption. It becomes possible to do.

  In the illumination device having the second configuration, when the luminance correction of the light emitting diode that emits green light proceeds to a predetermined level, the luminance correction unit thereafter performs redness rather than the luminance correction of the light emitting diode. In order to preferentially perform luminance correction of the light emitting diodes that respectively emit light and blue light, a configuration (third configuration) in which the cyclic frequency of luminance correction is set / changed for each light emitting diode may be used.

  In this way, by giving priority to the luminance correction of the light emitting diode that emits green light, it is possible to realize an increase in the luminance correction apparently. Then, correct brightness correction can be performed by performing brightness correction of the light emitting diodes that respectively emit red light and blue light. Accordingly, it is possible to maintain the final required time required until the target luminance of all the light emitting means and the actual luminance coincide with each other as before.

  Further, in the illumination device having any one of the first to third configurations described above, when the target brightness and the actual brightness of all the light emitting means match or fall within a predetermined range, the brightness correction means thereafter A configuration (fourth configuration) may be employed that reduces the frequency of the clock that regulates the luminance correction operation. With such a configuration, it is possible to maintain the color of the illumination light in a desired emission color while reducing the power consumption after the luminance correction is once completed.

  The display device according to the present invention is a display device including a display panel and a lighting device that illuminates the display panel, and the lighting device is any one of the first to fourth described above. It is good to make it the structure (5th structure) which has the illuminating device which consists of a structure. With such a configuration, it is possible to perform flexible and appropriate luminance correction in a short time using human visual characteristics in accordance with the error amount between the target luminance and the actual luminance, or user operation, etc. As a result, it is possible to obtain good display quality without color misregistration or the like.

  In the display device having the fifth configuration, the actual luminance detecting unit may be configured to detect the actual luminance of each light emitting unit by detecting light irradiated to the display panel via a light guide plate. . By adopting such a configuration, it is possible to appropriately correct the characteristic variation caused by the deterioration or malfunction of the entire lighting device including the light guide plate.

  As described above, in the lighting device according to the present invention and a display device using the same, flexible and appropriate luminance correction is performed by human vision according to the error amount between the target luminance and the actual luminance or the user operation. It becomes possible to carry out in a short time using the characteristics.

  FIG. 1 is a block diagram showing an embodiment of a display device according to the present invention. As shown in the figure, the display device of the present embodiment includes a light emitting unit 1 (a plurality of LEDs [Light Emitting Diodes] having different emission colors), LED drivers 21 to 2n, a memory 3, and an optical sensor 4. An analog / digital converter 5 (hereinafter referred to as ADC 5 [Analog / Digital Converter]), a central processing unit 6 (hereinafter referred to as CPU [Central Processing Unit] 6), a light guide plate 7, and a liquid crystal display A transmissive liquid crystal display including a panel 8 (hereinafter referred to as an LCD [Liquid Crystal Display] panel 8) and a liquid crystal display controller 9 (hereinafter referred to as an LCD controller 9).

  The light emitting unit 1 includes n (≧ 1) LEDs 11R to 1nR that emit red light, n LEDs 11G to 1nG that emit green light, and n LEDs 11B to 1nB that emit blue light. It consists of LEDs having red, green, and blue emission colors are arranged adjacent to each other so as to form a group. That is, the light emitting unit 1 is configured to include three LEDs having emission colors of red, green, and blue as a group and n sets of the LED groups. Therefore, in the light emission part 1, the illumination light which has a desired luminescent color (for example, white) is produced | generated by mixing the emitted light of each LED. The illumination light generated by the light emitting unit 1 is used as a backlight that illuminates the LCD panel 8 through the light guide plate 7.

  The LED drivers 21 to 2n are means for performing luminance control (luminance correction) of the light emitting unit 1 based on an instruction from the CPU 6. More specifically, the LED driver 21 performs luminance control for each color by performing drive current control for each of the LEDs 11R, 11G, and 11B forming a group. Similarly, the LED driver 22 performs luminance control of the LEDs 12R, 12G, and 12B, and the LED driver 2n performs luminance control of the LEDs 1nR, 1nG, and 1nB. In the present embodiment, a configuration in which LED drivers are associated one-to-one with one LED group is taken as an example. However, the configuration of the present invention is not limited to this, and one LED driver is used. A configuration in which a plurality of LED groups are collectively controlled may be used.

  The memory 3 is a storage means having a ROM [Read Only Memory] and a RAM [Random Access Memory], and is used as a target brightness setting means for setting a target brightness for each LED constituting the light emitting unit 1. . That is, the target luminance information (such as luminance correction table data) of each LED is stored in the memory 3 in advance.

  The optical sensor 4 is actual luminance detection means for detecting the actual luminance of the LEDs constituting the light emitting unit 1. In this embodiment, the single light sensor 4 capable of separately detecting red light, green light, and blue light is used, and the emitted light of one set of LED groups (LEDs 11R, 11G, and 11B). However, the configuration of the present invention is not limited to this, and a plurality of photosensors may be provided for each color, or a plurality of LED groups may be provided. Alternatively, an optical sensor may be provided for each. Further, the configuration may be such that the irradiation light to the LCD panel 8 via the light guide plate 7 is detected. That is, in this specification, the term “actual luminance” is used as a concept that includes not only luminance obtained by directly detecting light emitted from an LED but also luminance obtained indirectly through the light guide plate 7. It is. Thus, if it is the structure which detects the irradiation light through the light-guide plate 7, it will become possible to correct | amend appropriately also about the characteristic fluctuation | variation resulting from degradation and malfunction of the whole illuminating device containing the light-guide plate 7. FIG.

  The ADC 5 is means for converting an analog luminance signal obtained by the optical sensor 4 into a digital luminance signal and sending it to the CPU 6.

  The CPU 6 is a means for comprehensively controlling the entire operation of the display device. The CPU 6 has a function of correcting the luminance of the light emitting unit 1 through the LED drivers 21 to 2n and a function of performing drawing control of the LCD panel 8 through the LCD controller 9. Etc. The luminance correction (illumination light color correction) of the light emitting unit 1 by the CPU 6 is performed in a time-sharing manner so as to reduce the difference between the target luminance and the actual luminance for each LED having red, green, and blue emission colors. (See FIG. 3). The brightness correction operation by the CPU 6 will be described in detail later.

  The light guide plate 7 is a unit that uniformly emits light emitted from the light emitting unit 1 and guides it to the entire LCD panel 8, and generally includes a transparent plate (for example, an acrylic plate) whose surface is specially processed. .

  The LCD panel 8 is means for displaying an image by enclosing a liquid crystal between two glass plates and applying a voltage to change the molecular direction of the liquid crystal and increase or decrease the light transmittance.

  The LCD controller 9 is means for performing drawing control of the LCD panel 8 based on an instruction from the CPU 6.

  Next, luminance correction (color correction of illumination light) of the light emitting unit 1 by the CPU 6 will be described in detail with reference to FIGS. 2 and 3.

  FIG. 2 is a flowchart illustrating an example of the luminance correction routine, and FIG. 3 is a diagram illustrating an example in which the cyclic frequency of luminance correction is changed for each RGB color.

  When the brightness correction routine is started, the CPU 6 first sets the frequency of the clock that regulates the brightness correction operation to a normal value in step S5, and then emits red light and blue light respectively in step S10. The frequency of brightness correction is set for each LED so that the brightness correction of the LED emitting green light is preferentially performed over the brightness correction of (noted as G priority correction mode in FIG. 3).

  In the G priority correction mode, as shown in FIG. 3A, the luminance correction task for green is given priority, such as G, R, G, B, G, R, G, B,. To be done. Here, each color correction task shown in FIG. 3A represents that the plurality of LEDs of each color in FIG. 1 are subjected to luminance correction one after another (FIG. 3C). See).

  Here, the algorithm for preferentially correcting the luminance of the LED that emits green light is made in view of human visual characteristics that the green color difference is more sensitive than the red or blue color difference. That is, the above-described luminance correction algorithm has a conventional configuration in which luminance correction for each color is performed cyclically at a uniform cycle by preferentially performing luminance correction of an LED that emits green light at the initial stage of luminance correction. Rather than the user's subjective, based on the idea that the color of the illumination light can be quickly brought close to the desired emission color, the present inventor has conducted earnest research, resulting in a newly created technology It can be said that it is an ideal thought.

  Thus, if the brightness correction is performed for each LED having red, green, and blue emission colors in the priority order in consideration of human visual characteristics, it is necessary to increase the clock of the CPU 6 that causes an increase in power consumption. Therefore, it is possible to speed up the luminance correction apparently.

  While the G priority correction mode is selected, the CPU 6 determines in step S15 that the luminance correction of the LED emitting green light has a predetermined level (in other words, the error between the target luminance and the actual luminance is a predetermined level). It is determined whether or not it has advanced to Here, if it is determined that the luminance correction has progressed to a predetermined level, the flow proceeds to step S20. On the other hand, if it is determined that the luminance correction has not progressed to the predetermined level, the flow returns to step S10, and the G priority correction mode is continued.

  If it is determined in step S15 that the luminance correction has progressed to a predetermined level, the CPU 6 emits red light and blue light respectively in step S20 rather than luminance correction of the LED that emits green light. In order to preferentially perform the luminance correction, the frequency of cyclicity of luminance correction is changed for each LED (in FIG. 3, expressed as R and B priority correction modes).

  In the above R, B priority correction mode, as shown in FIG. 3B, luminance correction for red and blue is performed such as G, R, B, R, B, G, R, B,. Tasks are given priority.

  By adopting such a configuration, priority is given to the luminance correction of the LED that emits green light, and apparently after the speed of the luminance correction is realized, the LED that emits red light and blue light respectively. The delay in brightness correction can be recovered. Therefore, it is possible to maintain the final required time required to match the target luminance of all the LEDs with the actual luminance as before.

  While the above R and B priority correction modes are selected, the CPU 6 matches all target luminances and actual luminances for each LED having red, green, and blue emission colors in step S25 or a predetermined value. It is determined whether or not it is within the range (in other words, whether or not it has reached a state where brightness correction can be completed once). Here, when it is determined that the target luminance and the actual luminance are the same for all the LEDs or are within a predetermined range, the flow proceeds to step S30. On the other hand, if it is determined that the target luminance does not match the actual luminance for some LEDs, the flow returns to step S20, and the R and B priority correction modes described above are continued.

  If it is determined in step S25 that the target luminance and the actual luminance match for all LEDs, the CPU 6 sets the frequency of the clock that regulates the luminance correction operation to a value lower than the normal value (for example, 1) in step S30. / 2), and in the subsequent step S35, the cyclic frequency of luminance correction is changed for each LED so that the luminance correction of each LED having red, green, and blue emission colors is equally performed (FIG. 3 is expressed as RGB uniform correction mode).

  In the above-described RGB uniform correction mode, as shown in FIG. 3C, G, R, G, B,..., And so on, are longer than the G priority correction mode and the R, B priority correction mode. However, the luminance correction tasks for red, green, and blue are equally performed.

  As described above, once the luminance correction is completed, if the processing capacity of the CPU 6 is reduced, the power consumption can be reduced and the color of the illumination light can be maintained at a desired emission color. Of course, in order to continuously obtain good display quality free from color misregistration, it is necessary to continuously correct luminance fluctuations caused by fluctuations in ambient temperature, etc., once luminance correction has been completed. . However, since such luminance fluctuation exhibits a relatively slow behavior, it is considered that no particular trouble will occur even if the processing capacity of the CPU 6 is slightly reduced.

  In the above embodiment, the case where the present invention is applied to a transmissive liquid crystal display device has been described as an example. However, the application target of the present invention is not limited to this, and other illumination devices are used. And can be widely applied to display devices.

  The configuration of the present invention can be variously modified within the scope of the present invention in addition to the above embodiment.

  For example, in the above embodiment, in view of human visual characteristics, the description has been given by taking as an example a configuration that preferentially corrects the luminance of green light, but the configuration of the present invention is not limited to this. Depending on the amount of error between the target luminance and the actual luminance, the luminance of the emission color having a large difference may be preferentially corrected, or the luminance may be corrected according to the user operation.

  With such a configuration, flexible and appropriate luminance correction can be performed in a short time using human visual characteristics in accordance with the amount of error between the target luminance and the actual luminance or a user operation. Thus, it is possible to obtain a good display quality without color misregistration.

  In the above-described embodiment, the configuration using three LEDs having red, green, and blue emission colors as the light emitting means has been described as an example. However, the application target of the present invention is limited to this. Of course, the present invention can also be applied to configurations using light emitting means having other emission colors.

  The illumination device according to the present invention can be used, for example, as a backlight of a liquid crystal display, and as a display device including the same, a liquid crystal television receiver or a PDA [Personal Digital / Data Assistant] is used. A liquid crystal display or a liquid crystal display of a mobile phone can be used.

These are block diagrams which show one Embodiment of the display apparatus which concerns on this invention. These are flowcharts which show an example of a luminance correction routine. These are figures which show the example in which the cyclic frequency of brightness correction is changed for each RGB color.

Explanation of symbols

1 Light emitting part 11R, 12R, ..., 1nR LED (red)
11G, 12G, ... 1nG LED (green)
11B, 12B, ... 1nB LED (blue)
21 to 2n LED driver 3 Memory 4 Optical sensor 5 Analog / digital converter (ADC)
6 Central processing unit (CPU)
7 Light guide plate 8 Liquid crystal display panel (LCD panel)
9 Liquid crystal display controller (LCD controller)

Claims (6)

A plurality of light emitting means having different emission colors, target luminance setting means for setting the target luminance of each light emitting means, actual luminance detecting means for detecting the actual luminance of each light emitting means, the target luminance and the actual luminance Brightness correction means for performing brightness correction for each light emitting means so as to reduce the difference between the light emitting means, and generating illumination light having a desired emission color by mixing the emitted light of each light emitting means A device,
The brightness correction means includes a function of performing brightness correction for each light emitting means while traveling in a time-sharing manner and setting / changing the frequency of brightness correction for each light emitting means. Lighting device.   The light emitting means is three light emitting diodes having emission colors of red, green, and blue, and the luminance correction means emits green light rather than luminance correction of the light emitting diodes that emit red light and blue light, respectively. The lighting device according to claim 1, wherein the brightness correction cyclic frequency is set / changed for each light emitting diode so that the brightness correction of the light emitting diode is preferentially performed.   When the luminance correction of the light emitting diode that emits green light proceeds to a predetermined level, the luminance correction means thereafter corrects the luminance of the light emitting diode that emits red light and blue light rather than the luminance correction of the light emitting diode. The lighting device according to claim 2, wherein the cyclic frequency of luminance correction is set / changed for each light emitting diode so as to be preferentially performed.   2. The brightness correction means, when the target brightness and the actual brightness of all the light emitting means match or fall within a predetermined range, thereafter reduce the frequency of the clock that regulates the brightness correction operation. The lighting device according to claim 3.   A display device comprising a display panel and an illumination device that illuminates the display panel, wherein the illumination device comprises the illumination device according to any one of claims 1 to 4. A display device characterized by that. The display device according to claim 5, wherein the actual luminance detecting unit detects an actual luminance of each light emitting unit by detecting light irradiated to the display panel via a light guide plate.

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