JP2007286359A - Lighting system, display and lighting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enlarge the feedback periods based on the properties of the light emitting sources to simplify the system and to save the costs by controlling colors by using only a single simple feedback system. <P>SOLUTION: This lighting system has a three primary-color light emitting source 23 consisting of a red, green, and blue light emitting diodes 23R, 23G, and B, a back light unit 26 to output white light by mixing the light from the above light emitting source 23, a light quantity detector 32 to obtain the amount of each color light from the above light emitting source 23, and a controller 33 to control the light quantity balance of the color light from the light emitting source 23 based on the outputs of the light quantity detector 32. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an illumination device that illuminates a display panel, a display device, and an illumination method.

  Instead of CRT (Cathode Ray Tube), which has been used for many years since the start of television broadcasting, it has been made very thin, such as a liquid crystal display (LCD) and a plasma display (PDP). Television receivers have been devised and put into practical use. In particular, liquid crystal display devices using a liquid crystal display panel can be driven with low power consumption, and it is considered that the liquid crystal display device will be used at an accelerated pace due to the price reduction of large liquid crystal display panels. It is a display device that can be expected to develop further.

  In the liquid crystal display device, the light of the backlight arranged on the back side of the liquid crystal display panel is displayed by controlling the transmittance of each pixel. For color display of liquid crystal, red R, green G, and blue B filters are introduced into the pixels, the transmittance of each of R, G, B is controlled, and the ratio of R, G, B is controlled to provide various colors. it's shown.

  In order to display these colors, the ratio of R, G, and B in the backlight must be made accurate and a predetermined white color must be realized. As a method for realizing such a backlight, there is a case where a light source that emits light from a surface is used. However, in most cases, a method called a light guide plate method is employed in most of the small liquid crystal modules at present. A point or linear light source is placed on the side of the light guide plate, and the light incident on the light guide plate is totally reflected within the light guide plate, and a reflection microprism or scattering pattern is formed at a predetermined location, and the reflected light Alternatively, a surface light source is formed so that scattered light is uniformly emitted on the surface. Further, a prism sheet may be disposed on the light guide plate in order to condense light onto the liquid crystal on the surface.

  In such a light guide plate type backlight, a white cold cathode fluorescent lamp (CCFL) or a white light emitting diode (LED) is often used as a predetermined white light source. In addition, since the CCFL encloses mercury in a fluorescent tube and thus has an adverse effect on the environment, a light emitting diode (LED) is promising as a light source of a backlight device that replaces the CCFL (for example, Patent Document 1). In the case of a fluorescent tube, since a high voltage is required to light it, it is hardly used in a small mobile liquid crystal. Currently almost white LED light sources are used.

  However, the current white LED has a basic structure of an LED that emits blue light and a phosphor that emits yellow light when applied in front of the LED and receives blue light. Such an LED has only a pseudo white color. In particular, the balance when viewed in R, G, and B is extremely poor, and the R component is very low. Therefore, even if the filter characteristics of the liquid crystal are improved, the liquid crystal control method is improved and correct color display cannot be performed. That is, in a white LED, these lights have a poor balance between wavelengths, and in particular, R light is insufficient, and a correct color cannot be displayed through liquid crystal. Therefore, R, G, B three-color LEDs have been studied as light sources. Yes.

  In order to improve these problems, the use of LEDs that emit R, G, and B light in place of the pseudo-white LEDs is being studied.

  In recent years, with the development of blue light emitting diodes, light emitting diodes that emit red light, green light, and blue light, which are the three primary colors of light, have been prepared, and red light, green light, and blue light emitted from these light emitting diodes have been prepared. By mixing light, white light with high color purity can be obtained. Therefore, by using this light emitting diode as the light source of the backlight device, the color purity of the color light via the liquid crystal display panel is increased, so that the color reproduction range can be greatly expanded compared with the CCFL. Compared to the pseudo white LED, the R, G, B LEDs can optimize the wavelength of light required for color display of the liquid crystal to the color filter, and by adjusting the R, G, B wavelength and brightness. It is possible to make an ideal light source for liquid crystal display.

  However, when R, G, and B three-color LEDs are used, the predetermined white balance and color cannot be accurately displayed because the temporal changes in the R, G, and B LED luminances are different.

  Therefore, in the conventional backlight device, for example, as shown in FIG. 7, the light from the light source 122 composed of the R, G, B three-color LEDs 122R, 122G, 122B driven by the LED driving unit 121 is transmitted to the backlight unit 125. Light that has been captured and mixed in the backlight unit 125 is detected by color sensors 131R, 131G, and 131B having sensitivities that match the wavelengths of R, G, and B, for example, as shown in FIG. , 131B is used to feed back the detection output of the light of each color to the LED drive unit 121 via the control unit 133, and control the drive currents that flow through the R LED 122R, the G LED 122G, and the B LED 122B. By adjusting the output of 122G and 122B, the whiteness can be adjusted. It had to be an integer.

  Each of the color sensors 131R, 131G, and 131B is an optical sensor such as a phototransistor and is disposed on the light incident side of the light guide plate 124 of the backlight unit 125, and detects leakage light from the backlight unit 125.

Japanese Patent Laid-Open No. 7-191311

  In the conventional backlight device as described above, in order to separate the R, G, and B signals from the leaked light of the backlight, three photosensors are arranged, and the light receiving surface of the sensor of the first system has R light receiving surfaces. An R color filter was formed so that only light could enter. Similarly, a G color filter was formed on the second sensor and a B color filter was formed on the third sensor. Moreover, it is necessary to drive the sensors separately. For this reason, the system is complicated, and power consumption and a large space are also required. Therefore, the liquid crystal module is not suitable for downsizing.

  Further, the conventional backlight device as described above is based on the premise that the brightness of the LED is subject to severe time fluctuations, and is always in operation.

  However, when the luminance change of the actual LED light source was measured, it was found that it was very gradual, and it was not always necessary to continue the feedback.

  Accordingly, an object of the present invention is to provide a lighting device that can significantly reduce the cost by widening the feedback period from the characteristics of a plurality of light emitting sources, simplifying the system, and performing color control with a simple one-line feedback, A display device and an illumination method are provided.

  Other objects of the present invention and specific advantages obtained by the present invention will become more apparent from the description of embodiments described below.

  In the present invention, the feedback, which is required for three systems in the conventional backlight device, is simplified to one system. If the three systems of R, G, and B are simply made into one system, only one type of light of R, G, and B can be detected as a matter of course. For example, when only one system is used, it is possible to stabilize the R light by detecting the change in the R light and constructing a feedback system. However, it is necessary to detect and control the change in G and B. I can't. Similarly, even if one system of G and B is adopted, only G and B light can be controlled. In this way, it can be seen that color stabilization can be achieved with a simple system of only one system. A plan to detect white light as one system is also conceivable, but this can be achieved by detecting the luminance added by R, G, and B and feeding back to some extent, but color control is still not possible. .

  Therefore, in the present invention, the timing detected by the light quantity sensor is controlled in order to perform color control with a simple one-system feedback.

  In the conventional system, it is assumed that the luminance of the LED always changes greatly, and the luminance of each color is always detected and fed back. However, from the experimental results, the inventor has found that the LED backlight of R, G, B Although the brightness of R, G, and B changes, it has been found that it does not change constantly but changes very slowly.

  Therefore, in the present invention, in consideration of this characteristic, instead of the constant feedback, the brightness of R, G, B is detected at a certain time interval, and when the brightness changes, it is fed back to the LED driver, and R, G , B brightness balance is adjusted. This is possible for the first time after clarifying the luminance change of the LED.

  Furthermore, in the present invention, on the premise that the luminance is adjusted every certain time interval, when the luminance is detected, the LED driver and the light amount sensor are synchronized so that the lighting timing of the LED and the light intensity detection timing of the light amount sensor are synchronized. Synchronize the drive. The brightness detected from the light quantity sensor when the R LED is turned on is set as the intensity of R, the output of the light quantity sensor is set as the G light intensity when the G LED is turned on, and the light output when the B LED is turned on. Light intensity. By adopting this method, it becomes possible for the first time to detect R, G, B light with only one sensor system.

  That is, the present invention is an illuminating device for illuminating a display panel, and a plurality of light emitting light sources having different emission colors and a plurality of colors emitted from the plurality of light emitting light sources are mixed and emitted to the display panel. An illumination unit, a light amount detection means for detecting a light amount of at least one color of light of a plurality of colors emitted from the plurality of light emitting sources, and the plurality of light sources based on detection outputs from the light amount detection means at regular time intervals. And a control means for controlling the light quantity balance of light of a plurality of colors emitted from the light emitting light source.

  In addition, the present invention is a display device including a display panel illuminated by a lighting device, wherein the lighting device includes a plurality of light emission sources having different emission colors and a plurality of colors emitted from the plurality of light emission sources. An illumination unit that mixes and emits the light to the display panel, a light amount detection unit that detects the light amount of each color of light emitted from the plurality of light emission sources, and the light amount detection unit at regular time intervals And a control means for controlling the light quantity balance of the light of a plurality of colors emitted from the plurality of light emitting light sources based on the detection output of the above.

  Furthermore, the present invention is an illumination method for illuminating a display panel, wherein a plurality of colors emitted from a plurality of light emission sources having different emission colors are mixed and emitted to the display panel, and the plurality of light emission sources Detecting a light amount of at least one color of light of a plurality of colors emitted from the light source, and controlling a light amount balance of the light of a plurality of colors emitted from the plurality of light emission sources at regular time intervals based on the detection output. Features.

  In the conventional backlight device, three light quantity sensors are required to detect R, G, and B light. However, in the present invention, only one light quantity sensor is required.

  Further, in the conventional backlight device, in order to detect R, G, and B, a color filter is provided on each of the three light quantity sensors. However, in the present invention, these are not required. The structure itself is very simple.

  Furthermore, in the conventional backlight device, a circuit with three systems is also necessary for feedback, but in the present invention, color control can be performed with a simple system of feedback.

  Therefore, according to the present invention, it is possible to provide a lighting device, a display device, and a lighting method that can perform color control with a simple one-system feedback and significantly reduce costs.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Needless to say, the present invention is not limited to the following examples, and can be arbitrarily changed without departing from the gist of the present invention.

  The present invention is applied to, for example, a liquid crystal display device 100 configured as shown in FIG.

  The liquid crystal display device 100 includes a liquid crystal display panel 10 and a backlight device 20 that illuminates the liquid crystal display panel 10 with white light from the back side, as schematically shown in the cross-sectional view of the relevant part in FIG. Is provided.

  The liquid crystal display panel 10 includes a signal line and a scanning line arranged in a matrix, a thin film transistor as a switching element arranged at an intersection of the signal line and the scanning line, a glass substrate 11 on the back side on which a pixel electrode and the like are formed. A liquid crystal layer 13 in which, for example, a twisted nematic (TN) liquid crystal is sealed between the two glass substrates 11 and 12 is opposed to the front glass substrate 12 on which the counter electrode and the color filter are formed on the inner surface. Is a transmissive color liquid crystal display panel.

  The liquid crystal display device 100 is driven by an active matrix method in a state where the liquid crystal display panel 10 having such a configuration is sandwiched between two polarizing plates 14 and 15 and white light is irradiated from the back side by the backlight device 20. Thus, a desired full-color image can be displayed.

  As shown in FIGS. 1 and 2, the backlight device 20 is driven by an LED driving unit 21 to emit three primary color lights, the three primary color light sources 23 including a red LED 22R, a green LED 22G, and a blue LED 22B, and the three primary color light sources 23 are edges. The liquid crystal display panel includes a backlight unit 25 having a light guide plate 24 provided in a portion, and mixes the three primary color light incident from the three primary color light sources 23 with the light guide plate 24 to emit white light. This is a so-called edge light type backlight that illuminates 10 from the back side.

  Between the liquid crystal display panel 10 and the light guide plate 24, two prism sheets 26X and 26Y and a diffusion sheet 27 in which prisms are arranged in a direction orthogonal to each other are disposed. A reflection sheet 28 is disposed on the back surface.

  The backlight device 20 in the liquid crystal display device 100 has an incident surface of the light guide plate 24 on which the three primary color light sources are incident from the three primary color light sources 23 as schematically shown in the block diagram of FIG. And a control unit 33 for controlling the light quantity balance of the three primary color lights emitted from the three primary color light sources 23 based on the detection output by the light quantity detection hand part 32. Is provided.

  The controller 33 controls the light quantity balance of the three primary color lights emitted from the three primary color light sources based on the detection output from the light quantity detector 32 at regular time intervals.

  As the light quantity sensor 31 of the light quantity detection unit 32, a sensor having a characteristic capable of obtaining a sufficient output even if there is a difference in sensitivity over all wavelengths of visible light is used.

  As shown in FIG. 3, the controller 33 drives the red LED 22R, the green LED 22G, and the blue LED 22B in pulses by the LED driving unit 21 at the time of brightness adjustment, and activates the light quantity sensor 31 in synchronization with the pulses. Then, the control unit 33 sets the output obtained from the light quantity sensor 31 when R is lit to R brightness, the output of the light quantity sensor 31 is G brightness when G is lit, and the output of the light quantity sensor 31 is B brightness when B is lit. And the light quantity balance of the three primary color lights emitted from the three primary color light sources 23 is controlled based on the detection output from the light quantity detection unit 32. Since the sensitivity of the light quantity sensor 31 differs in each wavelength region, the true output of the red LED 22R, the green LED 22G, and the blue LED 22B is calculated by performing an appropriate calculation.

  For example, the R, G, and B optimum brightness levels stored in advance as the outputs of the red LED 22R, the green LED 22G, and the blue LED 22B detected by the light quantity detection unit 32, that is, the R, G, and B brightness levels (light quantity) are stored in advance. By performing a comparison operation, a difference from the optimum luminance is determined, and a current adjustment amount for obtaining the optimum luminance is calculated from the difference. Then, the optimal current amount is instructed to the LED drive unit, and the drive current value is corrected.

  Thereby, the light quantity balance of the three primary color lights is controlled by controlling the light quantity of the three primary color lights emitted from the three primary color light sources 23, and the white light obtained by mixing the three primary color lights is controlled within a certain chromaticity range.

  Here, when the luminance change of the actual LED light source was measured, as shown in FIG. 4, it was very gradual, and if the feedback control was performed once every several minutes to several hours, the above three primary color lights were mixed. Thus, the white light obtained can be controlled within a certain chromaticity range.

  As described above, in the backlight device 20 in the liquid crystal display device 100, the light amount detection unit 32 detects the light amount of the three primary color light emitted from the three primary color light source 23 including the red light emitting diode 23R, the green light emitting diode 23G, and the blue light emitting diode B. Then, based on the detection output from the light quantity detector 32, the controller 33 controls the red light quantity of the three primary color lights emitted from the three primary color light sources 23 at regular time intervals, whereby the three primary color light sources 23 are controlled. The white light obtained by mixing the three primary color lights from can be controlled in a certain chromaticity range.

  Further, the light quantity detection unit 32 is composed of one type of light quantity sensor 31, and the control unit 33 turns on the three primary color light sources 23 for each primary color light, and activates the light quantity sensor 31 in synchronization with the lighting. By controlling the light amount of each color by the light amount detection unit 32, color control can be performed with a simple system of feedback.

  As shown in FIG. 5, the temperature characteristics of the LED are between −20 ° C. and + 70 ° C., and the white LED has a small amount of change on the xy chromaticity diagram, and the white color is an R / G / B three-color LED. When is displayed, the amount of change is large. However, when R, G, and B are displayed in a single color, the amount of change on the xy chromaticity diagram is small even in the same environment. As shown in FIG. 6, the reason why the white color changes in the three-color LED is due to a change in luminance (in this case, the output amount of light). At this time, when the change in R, G, and B single colors is seen, the change amount of R is remarkable, but the change amounts of the single color changes of G and B are small compared to the white LED. Therefore, it is also possible to control the white / chromaticity range at the same level as that of the conventional white LED by feedback-controlling the light output of only R.

  Three primary color light sources 23 composed of a red light emitting diode 23R, a green light emitting diode 23G, and a blue light emitting diode B that emit three primary color lights, a backlight unit 26 that emits white light by mixing the three primary color lights from the three primary color light sources 23, and the above A light amount detection unit 32 that detects the light amounts of the three primary color lights emitted from the three primary color light sources 23 and a control that controls the light quantity balance of the three primary color lights emitted from the three primary color light sources 23 based on the detection output from the light amount detection unit 32. Part 33.

  In the above embodiment, the present invention is applied to a backlight type liquid crystal display device (LCD). However, the present invention can also be applied to a front light type display device and a non-self-luminous display other than the LCD. . Further, as the light source of the backlight device, a laser light source or the like can be used in addition to the R, G, and B three-color LEDs, and a light source having four peak wavelengths may be used.

It is principal part sectional drawing which shows typically the structure of the liquid crystal display device to which this invention is applied. It is a block diagram which shows typically the structure of the backlight apparatus in the said liquid crystal display device. It is a time chart which shows the control by the control part in the said backlight apparatus. It is a characteristic view which shows the measurement result of the luminance change of an actual LED light source. It is the characteristic figure which showed on the xy chromaticity diagram the temperature characteristic of chromaticity of white LED and R, G, B three-color LED. It is the characteristic figure which showed the temperature characteristic of the brightness | luminance of white LED and R, G, B three color LED. It is a block diagram which shows typically the structure of the conventional backlight apparatus. It is a characteristic view which shows the sensitivity characteristic of each light quantity sensor with which the light quantity detection part of the said backlight apparatus was equipped.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Liquid crystal display panel, 11, 12 Glass substrate, 13 Liquid crystal layer, 14, 15 Polarizing plate, 20 Backlight apparatus, 21 LED drive part, 22R Red LED, 22G Green LED, 22B Blue LED, 23 Three primary color light source, 24 Light guide plate , 25 Backlight unit, 26X, 26Y Prism sheet, 27 Diffusion sheet, 28 Reflection sheet, 31 Light quantity sensor, 32 Light quantity detection hand part, 33 Control part, 100 Liquid crystal display device

Claims (5)

An illumination device for illuminating a display panel,
A plurality of light emission sources each having a different emission color;
A lighting unit that mixes light of a plurality of colors emitted from the plurality of light emitting light sources and emits the light to a display panel;
A light amount detecting means for detecting a light amount of at least one color of light of a plurality of colors emitted from the plurality of light emitting sources;
And a control means for controlling the light quantity balance of the light of a plurality of colors emitted from the plurality of light emitting light sources based on detection outputs from the light quantity detecting means at regular time intervals. The light amount detecting means is composed of one kind of light amount sensor,
The control means performs control to cause the plurality of light-emitting light sources to pulse-light, activate the light quantity sensor in synchronization with the lighting, and detect the light quantity of each color by the light quantity detection means. The lighting device according to 1. A display device comprising a display panel illuminated by a lighting device,
The lighting device includes a plurality of light emitting light sources having different emission colors, a lighting unit that mixes light of a plurality of colors emitted from the plurality of light emitting light sources and emits the light to a display panel, and the light emitted from the plurality of light emitting sources. A light amount detecting means for detecting the light amount of each color of the plurality of colors of light, and a light amount balance of the light of the plurality of colors emitted from the plurality of light emitting light sources based on detection outputs from the light amount detecting means at regular time intervals. And a control means for controlling the display. An illumination method for illuminating a display panel,
Mixing multiple colors of light emitted from multiple light sources with different emission colors and emitting them to the display panel
Detecting the amount of light of at least one color of light of a plurality of colors emitted from the plurality of light emitting light sources,
An illumination method characterized by controlling the light intensity balance of a plurality of colors emitted from the plurality of light emitting sources at regular time intervals based on the detection output. The illumination method according to claim 4, wherein the plurality of light emitting light sources are pulse-lit, a light amount sensor is started in synchronization with the lighting, and the light amount of each color is detected by one type of the light amount sensor.

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