WO2008029831A1

WO2008029831A1 - Light receiving element, and illumination device and display device using the same

Info

Publication number: WO2008029831A1
Application number: PCT/JP2007/067269
Authority: WO
Inventors: Keiji Hayashi; Kentaro Kamada
Original assignee: Sharp Kabushiki Kaisha
Priority date: 2006-09-05
Filing date: 2007-09-05
Publication date: 2008-03-13

Abstract

It is possible to provide a light receiving element capable of detecting a wavelength change of a received light by using a simple configuration and to provide an illumination device capable of appropriately adjusting the color balance by using the light receiving element and a display device using the illumination device. The light receiving element (1) detects a light quantity from a plurality of light sources having different light emission bands. The light receiving element (1) has a plurality of narrow-band light receiving regions (10R, 10G, 10B) having a sensitivity based on the respective light emission bands of the light sources and a wide-band light receiving region (10W) having sensitivity based on the light emission bands of at least two light sources among the light sources.

Description

Specification

Light receiving element, illumination device using the same, and display device

Technical field

TECHNICAL FIELD [0001] The present invention relates to a light receiving element, an illumination device using the same, and a display device, and in particular, a light receiving element that detects the light amounts of a plurality of color LED light sources and a color of a plurality of color LED light sources using the light receiving elements The present invention relates to a lighting device that compensates for balance, and a display device using the lighting device.

Background art

In recent years, light emitting diodes (LEDs) have begun to be used as light sources for backlights of liquid crystal display devices in place of cold cathode tubes that have been mainstream. When using an LED as a light source for a backlight, it is common to use a three-color LED of red LED, green LED, and blue LED, or a four-color LED with white added to obtain white light. is there.

[0003] However, in general, LEDs do not always have a constant brightness even when the same current with large manufacturing variation is applied. Therefore, when LED is used as a light source for backlight, there is a problem that the color balance (generally white balance) must be adjusted. In addition, since the characteristics of LEDs tend to change depending on the temperature, even if the white balance was adjusted during the manufacture of the knocklight, the amount of light emitted changed with the temperature change during use, causing the white balance to be lost.

For this reason, a light receiving element is provided in the vicinity of each color LED to detect the amount of each color light emitted from these LEDs, and the supply current to the LED is controlled according to the amount of light detected by this light receiving element. By doing so, a display device that adjusts the white balance is known (Japanese Patent Publication No. 2004-184852).

Disclosure of the invention

Problems to be solved by the invention

However, when the light receiving element is configured to detect the amount of light from each color LED, there are the following problems. In other words, as a light receiving element that detects the amount of color light, A photodetector having sensitivity to the color wavelength is used. For example, as a light-receiving element that detects the amount of light emitted from a red LED, a photodetector having a sensitivity peak around 630 nm is used, as shown in Fig. 10 (a). Conventionally, in order to detect the light quantity of three colors of red, green, and blue LEDs, the light receiving surface of the light receiving element is generally divided into three parts as shown in FIG. A light receiving element provided with a red filter 97R, a green filter 97G, and a blue filter 97B is used.

[0006] However, the change in the light intensity of the LED is mainly caused by changes in the color of the emitted light due to temperature changes (shifts in the emission wavelength) and in cases where the absolute light intensity changes due to aging degradation of the LED (such as emission). There are two ways of reducing the amount of light. The emission wavelength shift is particularly remarkable in red LEDs. In other words, as shown in the characteristic curve rl of Fig. 10 (b), when the emission wavelength of the LED shifts to the longer wavelength side than the original characteristic curve r, the peak wavelength of the emitted light amount changes from the sensitivity peak of the light receiving element. The amount of light detected by the light receiving element is reduced. Also, as shown in the characteristic curve r2 in Fig. 10 (b), when the absolute light quantity of the LED decreases, the peak wavelength of the light emission quantity is the same. The amount of light detected is reduced. In other words, it cannot be determined from the output of the conventional light receiving element alone whether the emission wavelength shift or the emission amount reduction occurs.

As described above, the emission wavelength shift is significant in the red LED. Therefore, when the environmental temperature changes, the light receiving element output to the red LED is greatly reduced. In this case, if feed knock control is performed to increase the supply current to the red LED based on the light receiving element output, the amount of light at the peak emission wavelength shifted in the red LED increases, and the white balance deteriorates. End up.

[0008] In addition, in the above Japanese Patent Application Laid-Open No. 2004-184852, as a light receiving element, in addition to the amount of light, a device having a wavelength detection function for measuring a spectral characteristic or! / It is also described to use and adjust white balance based on wavelength. However, with such a configuration, it is necessary to use a high-performance light-receiving element that measures spectral characteristics and wavelength changes, resulting in an increase in cost.

[0009] Therefore, the present invention has been made in view of the above problems, and a light receiving element that can detect a change in wavelength of received light with a simple configuration, and a color variation by using the light receiving element. The aim is to provide an illuminating device capable of appropriately adjusting the illuminance and a display device using the illuminating device.

Means for solving the problem

In order to achieve the above object, a light receiving element according to the present invention is a light receiving element that detects light amounts in a plurality of different optical bands, and has a sensitivity corresponding to each of the plurality of optical bands. In addition to a plurality of narrow-band light receiving regions having a sensitivity band extending to at least two of the plurality of optical bands, and a ratio of sensitivity to light in each of the optical bands is narrow. It is further characterized by having a broadband light receiving area different from the sensitivity ratio of the band light receiving area.

[0011] Thus, in addition to a plurality of narrow-band light receiving areas having a sensitivity corresponding to each of a plurality of optical bands, it has a sensitivity band covering at least two of the plurality of optical bands. The ratio of the sensitivity to the light in each optical band is further provided with a broadband light-receiving area different from the sensitivity ratio of the narrow-band light-receiving area, so that compared to a conventional light-receiving element having only a narrow-band light-receiving area, By detecting light in the broadband light receiving region, it is possible to detect the emission wavelength shift of the received light. Accordingly, it is possible to provide a light receiving element that can detect a wavelength change of received light with a simple configuration.

[0012] In the light-emitting element according to the present invention, the plurality of narrow-band light receiving regions have a sensitivity corresponding to an optical band of 400ηm to 450nm, an optical band of 480nm to 550nm, and an optical band of 650nm to 700nm. It is preferable that the three light receiving regions each have

In order to achieve the above object, an illumination device according to the present invention includes a light receiving element according to the present invention, a plurality of light sources having different light emission bands, and narrow-band light reception of the light receiving element. A dimming circuit that controls the emission intensity of at least one of the plurality of light sources based on a change between an intensity signal of light received by at least one of the areas and an intensity signal of light received by the broadband light receiving area It is characterized by comprising.

[0014] According to this configuration, it is possible to provide an illumination device capable of appropriately adjusting the color balance at a low cost by using the light receiving element that can detect the wavelength change of the light emitted from the light source with a simple configuration.

[0015] In the lighting device according to the present invention, the dimming circuit includes the broadband light receiving region. Based on a difference intensity signal obtained by subtracting a signal obtained by multiplying a light intensity signal received in at least one of the narrow-band light receiving areas by a specific coefficient from an intensity signal of light received in the area, and It is preferable to control at least one emission intensity of the plurality of light sources.

[0016] In the illumination device according to the present invention, the dimming circuit receives light in the narrowband light receiving region having sensitivity according to the light emission band on the longest wavelength side among the plurality of narrowband light receiving regions. Based on the change between the light intensity signal and the light intensity signal received by the broadband light receiving region, the light source that emits at least the light emission band on the longest wavelength side among the plurality of light sources, and the long wavelength It is preferable to control the emission intensity of at least two light sources, with the light source emitting in the second emission band from the side.

[0017] According to this configuration, in the light source that emits light in the light emission band on the longest wavelength side, the light emission of the light source that emits light in the second light emission band from the long wavelength side when the phenomenon of light emission band force S shift occurs. By controlling the intensity, it is possible to compensate for the loss of color balance due to the shift of the light emission band of the light source that emits light in the light emission band on the longest wavelength side.

[0018] In the case of the above-described preferable configuration, the dimming circuit further receives light in a narrow-band light receiving region having sensitivity corresponding to the light emission band on the longest wavelength side among the plurality of narrow-band light receiving regions. When the intensity of light increases and the intensity of light received by the broadband light receiving region decreases, the emission intensity of the light source that emits light in the second emission band from the long wavelength side among the plurality of light sources is It is preferable to control to increase.

[0019] In order to achieve the above object, a display device according to the present invention includes an illumination device according to the present invention and a transmissive or transflective display element irradiated by the illuminator. It is characterized by having. As the display element, a liquid crystal display element is preferably used. This reduces the display device that can adjust the color balance appropriately by controlling the emission intensity of the light source of the lighting device using a light receiving element that can detect the wavelength change of the light emitted from the light source with a simple configuration. Can be provided at a cost.

The invention's effect

As described above, according to the present invention, a light receiving element that can detect a wavelength change of light emitted from a light source with a simple configuration, and an illumination that can appropriately adjust the color balance by using this light receiving element. It is possible to provide a device and a display device using the lighting device. Brief Description of Drawings

FIG. 1 is a plan view showing a schematic configuration of a light receiving element according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along line AA shown in FIG.

[FIG. 3 (a)] FIG. 3 (a) is a plan view and a cross-sectional view showing a structure in one main manufacturing process of the light receiving element.

[FIG. 3 (b)] FIG. 3 (b) is a plan view and a cross-sectional view showing a structure in one main manufacturing process of the light receiving element.

[FIG. 3 (c)] FIG. 3 (c) is a plan view and a cross-sectional view showing a structure in one main manufacturing process of the light receiving element.

[FIG. 3 (d)] FIG. 3 (d) is a plan view and a cross-sectional view showing a structure in one main manufacturing process of the light receiving element.

[FIG. 3 (e)] FIG. 3 (e) is a plan view and a cross-sectional view showing a structure in one main manufacturing process of the light receiving element.

FIG. 4 is a plan view showing a schematic configuration of a backlight device for a liquid crystal display device as an illumination device according to an embodiment of the present invention.

FIG. 5 is a cross-sectional view showing a schematic configuration of a liquid crystal display device including the backlight device shown in FIG. 4, and shows a cross-sectional structure at a position corresponding to line BB in FIG.

FIG. 6 is a plan view showing an internal schematic configuration of the LED package.

[FIG. 7] FIG. 7 is a wiring diagram showing a wiring state on a mounting board on which an LED package is mounted.

FIG. 8 is a block diagram showing a schematic configuration of a circuit that performs feedback control on each color LED based on the output of the light receiving element in the backlight device.

[Fig. 9] Fig. 9 (a) is a graph showing the sensitivity characteristics of the light receiving element according to the embodiment of the present invention, and Fig. 9 (b) shows two kinds of changes in the light emission characteristics of the LED. Is a graph

[FIG. 10] FIG. 10 (a) is a graph showing the sensitivity characteristics of a conventional light receiving element, and FIG. 10 (b) is a graph showing two types of changes in the light emission characteristics of the LED. FIG. 11 is a plan view showing a schematic configuration of a conventional light receiving element.

[FIG. 12 (a)] FIG. 12 (a) is a plan view and a cross-sectional view showing a structure in one manufacturing process of a conventional light receiving element having only a region for detecting each color light of RGB.

[FIG. 12 (b)] FIG. 12 (b) is a plan view and a cross-sectional view showing a structure in one manufacturing process of a conventional light receiving element.

[FIG. 12 (c)] FIG. 12 (c) is a plan view and a cross-sectional view showing a structure in one manufacturing process of a conventional light receiving element.

[FIG. 12 (d)] FIG. 12 (d) is a plan view and a cross-sectional view showing a structure in one manufacturing process of a conventional light receiving element.

[FIG. 12 (e)] FIG. 12 (e) is a plan view and a cross-sectional view showing a structure in one manufacturing process of a conventional light receiving element.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, for convenience of explanation, the drawings referred to below show only the main members necessary for explaining the present invention in a simplified manner among the constituent members of one embodiment of the present invention. Therefore, the implementation of the present invention may include any component not shown in the drawings to which this specification refers. In addition, the dimensions of the members shown in each figure do not faithfully represent the dimensions of the actual component members and the dimensional ratios of the members.

FIG. 1 is a plan view showing a schematic configuration of a light receiving element 1 according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line AA shown in FIG. As shown in FIGS. 1 and 2, the light receiving element 1 includes a silicon photodiode substrate 2, an electrode 3 connected to the silicon photodiode substrate 2, a lead wire 4 connected to the electrode 3, and a force metal case 5. It is a configuration enclosed in Four electrodes 3 are formed on the light receiving surface of the silicon photodiode substrate 2 and on the opposite surface, respectively. The lead spring 4 is pulled out of the metal case 5 and connected to a feedback control circuit or the like described later.

Note that the electrodes 3 and the lead wires 4 are represented as, for example, electrodes 3R and 3R and lead wires 4R and 4R, depending on the positions where they are formed. Where "3" or "4"

1 2 1 2

The letters `` R '', `` G '', `` B '', or `` W '' shown later indicate the electrode and lead, respectively. It distinguishes the type of filter that covers the area where the line is formed (details will be described later). The subscript “1” following the letter “R” or the like indicates that the electrode 3 and the lead wire 4 are provided on the light receiving surface side of the light receiving element 1. In addition, when the subscript is “2”, it indicates that the electrode 3 and the lead wire 4 are provided on the side opposite to the light receiving surface of the light receiving element 1.

The upper surface of the metal case 5 is sealed with a glass or resin lid 6 that transmits light. A filter layer 10 is laminated on the light receiving surface of the light receiving element 1, that is, the upper surface of the silicon photodiode substrate 2. In FIG. 2, in order to show the configuration of the light receiving element 1 in an easy-to-understand manner, a gap is shown between the filter layer 10 and the silicon photodiode substrate 2, but in actuality, the filter layer 10 Is formed in close contact with the surface of the silicon photodiode substrate 2 and the electrode 3 formed on the surface.

[0026] As shown in FIG. 1, the light receiving surface of the light receiving element 1 has a substantially disk shape and is divided into four fan-shaped regions having a central angle of approximately 90 °. The silicon photodiode substrate 2 is also divided into four at the same position as the light receiving surface, and the divided regions are insulated from each other. The filter layer 10 stacked on the light-receiving surface includes the deep red filter 10R, the green filter 10G, and the blue filter 10B that are stacked on the surface of three of the four regions, and the remaining one region. And a visual sensitivity correction filter 10 W stacked on the substrate. The deep red finoleta 10R transmits light in the wavelength range of about 650 nm to about 700 nm. The green filter 10G transmits light in a wavelength range of about 480 nm to about 550 nm. The blue filter 10B transmits light having a wavelength range of about 400 nm to about 450 nm. The visibility correction filter 10W transmits the entire visible light wavelength range and has a transmittance spectrum substantially along the visibility curve. As the visibility correction filter 10W, for example, “Lumicle UCF (trade name)” manufactured by Kureha Chemical Industry Co., Ltd. can be used. The visibility correction filter 10W may extend to the upper layer of other light receiving regions (crimson finoretta 10R, green finoleta 10G, and blue filter 1OB). However, for the purpose of increasing the signal strength and increasing the S / N ratio, it is desirable that the visibility correction filter 10W be stacked only in one of the four areas where the light receiving surface is divided.

In FIG. 1, a substantially transparent visibility correction filter is provided on the light receiving surface side of the light receiving element 1.

Although only the electrode 3W under 10W is visible, the crimson filter 10R The electrodes 3R, 3G, and 3B are also provided below the green filter 10G and the blue filter 10B, as indicated by broken lines in FIG. Electrode 3W, 3R, 3G, 3B respectively

1 1 1 1 1 1 1

Connected to the lead wires 4W, 4R, 4G, 4B. Also not shown in Figure 1.

1 1 1 1

However, the electrodes 3W, 3R, 3G, and 3B are provided on the surface opposite to the light receiving surface of the light receiving element 1 (see FIG. 2). Lead wires 4W, 4R, 4G and 4B are connected to the electrodes 3W, 3R, 3G and 3B, respectively. As a result, the light receiving element 1 receives the received light amount in the region where the crimson filter 10R is provided, the received light amount in the region where the green filter 10G is provided, the received light amount in the region where the blue filter 10B is provided, Separately outputs the received light amount of the area where only the sensitivity correction filter 10W is provided.

Here, a method for manufacturing the light receiving element 1 will be described with reference to FIG. In each of FIGS. 3 (a) to 3 (e), the left side is a plan view of the light receiving element, and the right side is a cross-sectional view taken along the line AA in the plan view. First, a slit is made in the silicon photodiode substrate 2 shown in Fig. 3 (a), and it is divided into four regions 2W, 2R, 2G, and 2B as shown in Fig. 3 (b), and the dividing boundaries of these regions are divided. Insulate. Next, as shown in FIG. 3 (c), an electrode 3 and a lead wire 4 are attached to each region of the silicon photodiode substrate 2 divided into four. Next, as shown in FIG. 3 (d), the deep red filter 10R, the green filter 10G, and the blue color are formed on the surface of the regions 2R, 2G, and 2B of the regions divided into four in the silicon photodiode substrate 2. Filters 10B are formed sequentially. Also, a visibility correction filter 10W is formed on the surface of the region 2W. Next, the silicon photodiode substrate 2 is placed in a metal case 5 and sealed with a lid 6 as shown in FIG.

[0029] For comparison with the manufacturing process of the light receiving element 1 according to the present embodiment, conventional light receiving having only regions for detecting each color light of RGB is shown in FIGS. 12 (a) to 12 (e). The manufacturing process of the device (see Fig. 11) is shown. In each of FIGS. 12 (a) to 12 (e), a plan view of the conventional light receiving element on the left side is shown, and a cross-sectional view taken along the CC line in the plan view is shown on the right side. In the conventional light receiving element manufacturing process, first, the silicon photodiode substrate 92 shown in FIG. ; As shown in Fig. 12 (b), divide the area 92R, 92G, and 92B into 3 parts and insulate the dividing boundaries of these areas. Next, as shown in FIG. 12 (c), an electrode 93 and a lead wire 94 are attached to each region of the silicon photodiode substrate 92 divided into three. Next, figure 12 (d), a red filter 97R, a green filter 97G, and a blue filter 97B are sequentially formed on the respective surfaces of the regions 92R, 92G, and 92B divided into three in the silicon photodiode substrate 92. Thereafter, a visibility correction filter 97W (see FIG. 12 (e)) is formed on the entire surface of these filter layers. Next, the silicon photodiode substrate 92 is placed in a metal case 95 and sealed with a lid 96 as shown in FIG. This completes the conventional light receiving element.

As can be seen from a comparison between FIG. 3 and FIG. 12, the number of manufacturing steps of the light receiving element 1 is the same as the number of manufacturing steps of the conventional light receiving element. Accordingly, the light receiving element 1 can be easily manufactured without increasing the manufacturing cost as much as the conventional light receiving element having only the region for detecting each color light of RGB.

FIG. 4 is a plan view showing a schematic configuration of a backlight device 20 for a liquid crystal display device as a lighting device according to an embodiment of the present invention. FIG. 5 is a cross-sectional view showing a schematic configuration of the liquid crystal display device 30 including the backlight device 20 shown in FIG. 4, and shows a cross-sectional structure at a position corresponding to the line BB in FIG. As shown in FIGS. 4 and 5, the backlight device 20 includes a bottomed case 21 having an opening on the side on which the liquid crystal panel 31 is installed, and an LED package 22 arranged on the bottom surface of the case 21. Yes. In FIG. 5, the LED drive circuit board 28 that controls the lighting of the LED package 22 is arranged on the lower side of the bottom surface of the case 21. 4 and 5 are diagrams showing only schematic components of the backlight device 20 and the liquid crystal display device 30, and the actual backlight device and the liquid crystal display device are shown in these drawings. There may be no optional components. For example, in FIG. 5, a frame and the like for holding the constituent members of the liquid crystal display device 30 are not shown.

As the liquid crystal panel 31, a transmissive or transflective liquid crystal panel can be used. The configuration and operation mode of the liquid crystal panel 31 are arbitrary, and any known liquid crystal panel can be used.

FIG. 6 is a plan view showing a schematic internal configuration of the LED package 22. LED package

As shown in FIG. 6, a red LED 22R, a green LED 22G, and a blue LED 22B are enclosed in one package, as shown in FIG. The top surface of the LED package 22 is transparent Sealed with a grease case 29. The transparent resin case 29 may have a lens effect in order to give directivity to the emitted light. A predetermined number of LED packages 22 are arranged on the mounting board 23, and the mounting boards 23 are spread on the bottom surface of the case 21. In addition, a white diffuse reflection member 27 is disposed on the mounting substrate 23 so that the light emitted from the LED and the light reflected from the diffuser 32 (see Fig. 5) are reflected toward the diffuser 32. I am letting.

[0034] In FIG. 4, a force exemplifying a configuration in which a plurality of mounting boards 23 on which the LED packages 22 are mounted is laid on the bottom surface of the case 21. The number of LED packages on the mounting board In addition, the number of mounting boards arranged in the case is not limited to the example in FIG. Further, the shape of the LED package 22 and each color LED, the arrangement of each color LED in the LED package 22, and the like are not limited to the example of FIG.

FIG. 7 is a wiring diagram showing a state of wiring on the mounting board 23. As shown in Figure 6, the LED package 22 on the mounting board 23 supplies current to the red LED 22R. Wiring line 24a, wiring to supply current to the green LED 22G 24b, and wiring to supply current to the blue LED 22B 24c is arranged. As a result, the red LED 22R, green LED 22G, and blue LED 22B of the LED package 22 can be controlled independently. Note that the wiring 24a, the wiring 24b, and the wiring 24c are connected in series or in parallel with each of the LEDs 22R, 22G, and 22B in the LED package 22 mounted on the same mounting board 23. Electric power is supplied from the LED drive circuit board 28 to the LED 22 through the wiring 24a, the selfish line 24b, and the selfish line 24c.

[0036] The inner surface of the case 21 is a white reflecting surface. The light receiving element 1 is attached in the vicinity of the upper end of the opening of the case 21 so that the light receiving surface faces the vicinity of the center of the bottom surface of the case 21. In addition, as shown in FIG. 5, optical sheets such as a diffusion plate 32, diffusion sheets 33 and 35, and a prism sheet 34 are laminated between the opening of the case 21 and the liquid crystal panel 31. By these optical sheets, red light, green light, and blue light emitted from the LEDs of each color of the LED package 22 are mixed and irradiated to the liquid crystal panel 31 as white planar light.

FIG. 8 shows a circuit for performing feedback control on the red LED 22 R, the green LED 22 G, and the blue LED 22 B based on the output of the light receiving element 1 in the backlight device 20. It is a block diagram which shows schematic structure. As shown in FIG. 8, the backlight device 20 inputs the detection result from the light receiving element 1, and controls the supply current to the red LED 22R, the green LED 22G, and the blue LED 22B based on the detection result. It is equipped with a light control circuit 25 that adjusts the amount of light of each color!

[0038] From the light receiving element 1, a signal SR indicating the amount of received light in the region where the deep red filter 10R is provided, a signal SG indicating the amount of received light in the region where the green filter 10G is provided, and a blue filter 10B are provided. A signal SB indicating the amount of light received in the region thus obtained and a signal SW indicating the amount of light received in the region where the visibility correction filter 10W is provided are output to the dimming circuit 25.

[0039] The light control circuit 25 includes a red light fluctuation analysis unit 251, a green light fluctuation analysis unit 252, a blue light fluctuation analysis unit 253, a red LED control unit 254, a green LED control unit 255, and a blue LED control unit 2 56. It has. The red light fluctuation analysis unit 251 inputs the signal SR, the signal SB, and the signal SW, and analyzes the light quantity change of the red LED 22R and the presence / absence of the wavelength shift based on these signals. The green light fluctuation analysis unit 252 analyzes the change in the amount of light of the green LED 22G based on the signal SG. The blue light fluctuation analysis unit 253 analyzes the change in the light amount of the blue LED 22B based on the signal SB.

[0040] The red light fluctuation analysis unit 251 calculates the light amount of the red LED 22R.

SR '= signal SW strength X signal SG strength + 13 X signal SB strength)

(However, α and / 3 are correction constants that have been set in advance to correct the difference in signal intensity for each light receiving area)

Seek strength. When it is detected that the light intensity of the red LED 22R has increased, an instruction is sent to the red LED control unit 254 to decrease the supply current to the red LED 22R.

[0041] Further, when the red light fluctuation analysis unit 251 detects that the light amount of the red LED 22R is decreased, the light amount decrease of the red LED 22R is caused by the emission wavelength shift of the red LED 22R based on the signal SR and the signal SW. It is determined whether it is caused by the decrease in absolute light intensity of the red LED22R.

That is, the red light fluctuation analysis unit 251 includes a memory (not shown) that stores the previous calculation result of the signal SR from the light receiving element 1 and the above SR ′. If the intensity increases from the previous time and the above SR 'calculation result decreases from the previous time, the red Color Judge that the emission wavelength shift of LED22R has occurred. On the other hand, when the intensity of the signal SR is less than or equal to the previous level, and the intensity of the calculated SR ′ is lower than the previous level, the red light fluctuation analysis unit 251 Judge that the absolute light intensity has decreased. The contents of the memory are updated to new values each time the signal SR, signal SW, etc. are sent from the light receiving element 1 to the dimming circuit 25 and feedback control is performed.

[0043] When it is determined that the light intensity of the red LED 22R has decreased and the emission wavelength shift of the red LED 22R has occurred, the red light fluctuation analysis unit 251 supplies the green LED 22G, not the supply current to the red LED 22R. Sends an instruction to the green LED control 255 to increase the current. In other words, in this case, the emission wavelength of the red LED 22R shifts to the longer wavelength side, and the red LED 22R develops high-purity red, resulting in mixing the light rays from the red LED 22R, green LED 22G, and blue LED 22B White coloring power The whiteness shifts toward red and black rather than the original whiteness. This is because the color coordinates of white obtained as a result of color mixing are expressed as a vector sum on the chromaticity coordinates of the colors emitted by the red LED 22R, the green LED 22G, and the blue LED 22B. Therefore, in order to obtain the desired whiteness, it is necessary to correct the amount of white shift by increasing the light emission amount of the green LED 22G and the blue LED 22B. Since the increase in the amount of light required at this time needs to be 3x green compared to X times blue, it is actually only necessary to add correction to the amount of light emitted by the green LED 22G.

[0044] On the other hand, when it is determined that the light intensity of the red LED 22R has decreased and the absolute light intensity of the red LED 22R has decreased, the red light fluctuation analysis unit 251 increases the supply current to the red LED 22R so as to increase the supply current. Sends instructions to LED control unit 254.

[0045] Here, based on the signal SR and the signal SW, the reason why it is possible to determine whether the decrease in the light amount of the red LED 22R is due to the emission wavelength shift of the red LED 22R or the decrease in the absolute light amount of the red LED 22R. This will be described with reference to FIG. The light receiving sensitivity for each region in the light receiving element 1 is as shown in FIG. 9 (a). In FIG. 9 (a), the photosensitivity curve in the region where the blue filter 10B is provided is si, the photosensitivity curve in the region where the green filter 10G is provided is s2, and the deep red filter 10R is provided. The light reception sensitivity curve in the region where the light is received is s3, and the light reception sensitivity curve in the region where the visibility correction filter 10W is provided is s4. [0046] It is assumed that the red LED22R force S was originally emitting light with the characteristics shown in the characteristic curve r in FIG. 9 (b). If the light emission characteristics of the red LED22R shift to the long wavelength side as shown in the characteristic curve rl due to temperature change (temperature rise), it can be seen from the comparison between Fig. 9 (a) and Fig. 9 (b). In addition, the intensity of the signal SR tends to increase because the amount of light having a wavelength that matches the sensitivity peak in the region where the deep red filter 10R is provided increases. In addition, the light emission characteristic of the red LED 22R shifts to the longer wavelength side, so the amount of light with a wavelength that matches the sensitivity peak in the region where the visibility correction filter 10W is provided decreases, so the intensity of the signal SW tends to decrease. Na

[0047] On the other hand, as shown by the characteristic curve r2 in FIG. 9 (b), when the absolute light amount of the red LED 22R is reduced, it can be understood by comparing FIG. 9 (a) and FIG. 9 (b). As described above, the intensity of the signal SR tends to decrease because the amount of light having a wavelength matching the sensitivity peak in the region where the crimson filter 10R is provided decreases. In addition, since the amount of light having a wavelength that matches the sensitivity peak in the region where the visibility correction filter 10W is provided increases, the intensity of the signal SW tends to increase.

[0048] The green light fluctuation analysis unit 252 obtains the light amount of the green LED 22G from the signal SG, and when the light amount of the green LED 22G increases, the green LED control unit 255 is caused to increase the supply current to the green LED 22G. Send instructions. Further, when the light amount of the green LED 22G decreases, the green light fluctuation analysis unit 252 sends an instruction to the green LED control unit 255 to decrease the supply current to the green LED 22G.

[0049] The blue light fluctuation analysis unit 253 obtains the light amount of the blue LED 22B from the signal SB, and when the light amount of the blue LED 22B increases, the blue LED control unit 256 increases the supply current to the blue LED 22B. Send instructions. Further, when the light amount of the blue LED 22B decreases, the blue light fluctuation analysis unit 253 sends an instruction to the blue LED control unit 256 to decrease the supply current to the blue LED 22B.

[0050] As described above, the light control circuit 25 of the backlight device 20 according to the present embodiment includes the light receiving element.

When the amount of red light received by the light receiving element 1 decreases based on the output signals SR and SW from 1, the red LED 22R shifts the emission wavelength and the absolute light amount! Force can be detected. If the emission wavelength shift of the red LED 22R occurs, increase the supply current to the green LED 22G instead of the red LED 22R. When the white light balance is adjusted and the absolute light intensity of the red LED 22R is decreasing, the white balance is adjusted by increasing the supply current to the red LED 22R. Thus, according to the backlight device 20, it is possible to appropriately adjust the color balance without using, for example, a high-performance light receiving element that measures spectral characteristics and wavelength changes.

[0051] While specific embodiments of the present invention have been described above, the above specific examples are merely embodiments of the present invention, and are not intended to limit the technical scope of the present invention. It can be changed.

[0052] For example, in the above-described embodiment, the force S shown in the configuration example in which the feedback current is supplied to the LEDs of three colors of red, green, and blue. It is also possible to control only the LEDs with colors that have a significant effect on the color balance that is not necessary.

In the above embodiment, a light receiving element provided with a light sensitivity correction filter on the light receiving surface in addition to the crimson color filter, the green color filter, and the blue color filter is exemplified, but the visibility correction filter is not essential. . For example, there is no practical problem even if a filter that absorbs near infrared rays (approximately 850 nm or more) is used in place of the above-described visibility correction filter 10W. What is needed here is to prevent the silicon photodiode substrate 2 of the light receiving element 1 from generating an electromotive force due to near infrared rays and erroneously outputting a signal added to the visible light intensity. .

In the above embodiment, a configuration in which a total of three LEDs of a red LED, a green LED, and a blue LED are enclosed in the LED package 22 is exemplified. However, the LED colors to which the present invention can be applied are not limited to the three primary colors RGB. In addition, the configuration is not limited to the configuration in which the same number of LEDs of each color are provided, and the ratio of the number of LEDs of each color is not uniform depending on the light emission characteristics of each color LED and the color tone of light desired as illumination light. Also good.

Industrial applicability

[0055] The present invention uses a light receiving element that can detect a change in wavelength of received light with a simple configuration, a lighting device that can appropriately adjust the color balance by using the light receiving device, and the lighting device. The display device can be used industrially.

Claims

The scope of the claims

[1] A light receiving element that detects light amounts in a plurality of different optical bands,

In addition to a plurality of narrow-band light receiving areas having a sensitivity corresponding to each of the plurality of light bands,

A broadband light-receiving region having a sensitivity band that covers at least two of the plurality of light bands, and having a sensitivity ratio to light in each light band different from a sensitivity ratio of the narrow-band light receiving region A light receiving element characterized by further comprising:

[2] The plurality of narrow-band light receiving regions are three light receiving regions each having a sensitivity corresponding to an optical band of 400 nm to 450 nm, an optical band of 480 nm to 550 nm, and an optical band of 650 nm to 700 nm. The light receiving element described in 1.

[3] The light receiving element according to claim 1 or 2,

A plurality of light sources having different emission bands,

At least one light emission of the plurality of light sources based on a change between an intensity signal of light received by at least one of the narrow-band light receiving regions of the light receiving element and an intensity signal of light received by the broadband light receiving region. An illumination device comprising a dimming circuit for controlling intensity.

[4] The light control circuit is obtained by multiplying a light intensity signal received in at least one of the narrow-band light receiving areas by a specific coefficient from a light intensity signal received in the wide-band light receiving area. The lighting device according to claim 3, wherein the light emission intensity of at least one of the plurality of light sources is controlled based on a difference intensity signal obtained by subtraction.

[5] The light control circuit includes an intensity signal of light received in a narrowband light receiving region having sensitivity according to a light emission band on the longest wavelength side among the plurality of narrowband light receiving regions, and the wideband light receiving region. Based on the change in the intensity signal of the light received at the light source, at least the light source that emits light in the emission band on the longest wavelength side and the light emission in the second emission band from the long wavelength side among the plurality of light sources The lighting device according to claim 3 or 4, which controls the light emission intensity of at least two light sources with the light source.

[6] The light control circuit increases an intensity of light received in a narrow band light receiving region having sensitivity according to a light emission band on a longest wavelength side among the plurality of narrow band light receiving regions, and 6. When the intensity of light received in a broadband light receiving region decreases, control is performed so that the emission intensity of a light source that emits light in a second emission band from the long wavelength side among the plurality of light sources is increased. Lighting equipment.

7. The lighting device according to any one of claims 3 to 6, wherein the light source is a light emitting diode.

[8] The lighting device according to any one of claims 3 to 7,

A display device comprising: a transmissive or transflective display element irradiated by the illumination device.

9. The display device according to claim 8, wherein the display element is a liquid crystal display element.