JP2006309981A - Backlight device and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce color unevenness and luminance unevenness of a backlight by providing a transparent light guide plate with a planar optical element. <P>SOLUTION: In a backlight device to illuminate a liquid-crystal display panel from the back side which comprises a point light source as a light source and a transparent plate above this point light source, the transparent plate is provided with the planar optical element which has the function of controling a direction of travel of light emitted by the point light source. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a backlight device used to display an image by irradiating light onto a liquid crystal display panel or the like, and a liquid crystal display device using the backlight device. More specifically, the backlight device reduces luminance unevenness and color unevenness. The present invention relates to a light device and a liquid crystal display device.

  Currently, a liquid crystal display (LCD) is mainly a backlight system that displays a color image by illuminating a transmissive liquid crystal display panel equipped with a color filter from the back side with a backlight device. ing. As a light source of the backlight device, a fluorescent lamp such as a CCFL (Cold Cathode Fluorescent Lamp) that emits white light using a fluorescent tube is often used. However, since CCFL encloses mercury in the fluorescent tube, The light emitting diode (LED: Light Emitting Diode) is considered promising as a light source of a backlight device that replaces the CCFL (see, for example, Patent Document 1).

  However, in a backlight device using a point light source such as a light emitting diode, a ball-like high-luminance portion is generated directly above the point light source. It is known that a reflection plate is provided between the point light source and light emitted from the point light source is reflected by the reflection plate to prevent uneven brightness (for example, see Patent Document 2).

  In addition, with the development of blue light-emitting diodes, light-emitting diodes that emit red, green, 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, a backlight device using light emitting diodes of these three colors as a light source is known.

However, in a backlight device using a three-color light emitting diode as a light source, a portion with high red luminance is generated directly above the red light emitting diode, and a portion with high green luminance is directly above the green light emitting diode. As a result, a portion with high blue luminance is generated immediately above the blue light emitting diode. Therefore, in order to prevent this, a transparent plate is provided between the diffusion plate and the light emitting diode of each color, and dots are formed by applying an absorbing material or a reflecting material to the transparent plate, and emitted from the light emitting diode. It is known to prevent luminance unevenness and color unevenness by absorbing or reflecting light at a dot portion (see, for example, Non-Patent Document 1).
Japanese Patent Laid-Open No. 7-191311 Japanese Patent Application Laid-Open No. 2004-313153 Nikkei Electronics (Nikkei BP), December 20, 2004 (No. 889), pages 123-130

  However, when reducing the thickness of a backlight device or a liquid crystal display device using the backlight device, it is necessary to reduce the distance between the light emitting diode and the diffusion plate, so that the light emitted from the light emitting diode is reflected by the reflecting plate. Even if it does so, since the optical path length for mixing light cannot be sufficiently ensured until the reflected light enters the diffuser plate, there arises a problem that luminance unevenness and color unevenness cannot be prevented. .

  In addition, when dots are formed with an absorbent material on a transparent plate, the light emitted from the light emitting diodes is absorbed by the dots, so there is not enough light to secure the luminance necessary to display an appropriate image. The problem of end up occurs.

  In consideration of the above points, the present invention provides a backlight device and a liquid crystal display device that can reduce color unevenness and brightness unevenness.

  A backlight device according to the present invention is a backlight device that illuminates a liquid crystal display panel from the back side, and includes a point light source as a light source, and a transparent plate above the point light source. The planar optical element having a function of controlling the traveling direction of the light emitted from the point light source is provided.

  The liquid crystal display device according to the present invention is a liquid crystal display device comprising a liquid crystal display panel and a backlight device that illuminates the liquid crystal display panel from the back side, and the backlight device includes a point light source as a light source, In addition, a transparent plate is provided above the point light source, and a planar optical element having a function of controlling the traveling direction of light emitted from the point light source is provided on the transparent plate.

  In the backlight device and the liquid crystal display device of the present invention, color unevenness and luminance unevenness are prevented from occurring by controlling the traveling direction of the light emitted from the light source.

  According to the backlight device according to the present invention, color unevenness and luminance unevenness of the backlight can be reduced.

  According to the liquid crystal display device of the present invention, it is possible to reduce the color unevenness and luminance unevenness of the backlight and improve the quality of the displayed image.

Hereinafter, examples of the best mode for carrying out the backlight device and the liquid crystal display device according to the present invention will be described, but the present invention is not limited to the following examples.
The present invention can be applied to, for example, a transmissive color liquid crystal display device 100 configured as shown in FIG. The transmissive color liquid crystal display device 100 includes a transmissive color liquid crystal display panel 110 and a backlight device 140 provided on the back side of the color liquid crystal display panel 110. Although not shown, the transmissive color liquid crystal display device 100 includes a receiving unit such as an analog tuner and a digital tuner that receives terrestrial and satellite waves, and a video signal that processes a video signal and an audio signal received by the receiving unit, respectively. An audio signal output unit such as a processing unit, an audio signal processing unit, a speaker that outputs an audio signal processed by the audio signal processing unit, and the like may be provided.

  In the transmissive color liquid crystal display panel 110, two transparent substrates (TFT substrate 111 and counter electrode substrate 112) made of glass or the like are arranged to face each other, and, for example, twisted nematic (TN) liquid crystal is provided in the gap. The liquid crystal layer 113 encapsulating the liquid crystal layer 113 is provided. On the TFT substrate 111, signal lines 114 arranged in a matrix, scanning lines 115, thin film transistors 116 serving as switching elements arranged at intersections of the signal lines 114 and the scanning lines 115, and pixel electrodes 117 are formed. Has been. The thin film transistor 116 is sequentially selected by the scanning line 115 and writes the video signal supplied from the signal line 114 to the corresponding pixel electrode 117. On the other hand, a counter electrode 118 and a color filter 119 are formed on the inner surface of the counter electrode substrate 112.

  The color filter 119 is divided into a plurality of segments corresponding to each pixel. For example, as shown in FIG. 2, it is divided into three segments of a red filter CFR, a green filter CFG, and a blue filter CFB which are three primary colors. The arrangement pattern of the color filter 119 includes a delta arrangement and a square arrangement, although not shown, in addition to the stripe arrangement shown in FIG.

  The configuration of the transmissive color liquid crystal display device 100 will be described again with reference to FIG. In the transmissive color liquid crystal display device 100, the transmissive color liquid crystal display panel 110 having such a configuration is sandwiched between two polarizing plates 131 and 132, and white light is irradiated from the back side by the backlight device 140. By driving with an active matrix system, a desired full-color image can be displayed.

  The backlight device 140 illuminates the color liquid crystal display panel 110 from the back side. As shown in FIG. 1, the backlight device 140 includes a diffusion plate 141, a light source (not shown), and a backlight plate 120 in order to mix light emitted from the light source into white light. The configuration includes an optical function sheet group 145 such as a diffusion sheet 142, a prism sheet 143, and a polarization conversion sheet 144 that are arranged on the diffusion plate 141.

The diffusing plate 141 makes the luminance emitted from the surface emission uniform by internally diffusing the light emitted from the backlight casing 120.
In general, the optical function sheet group 145 includes, for example, a function of decomposing incident light into orthogonal polarization components, a function of compensating for a phase difference of light waves to achieve a wide-angle viewing angle and preventing coloring, a function of diffusing incident light, and luminance. It is composed of a sheet having a function to improve, and is provided to convert light emitted from the backlight device 140 into illumination light having optical characteristics optimal for illumination of the color liquid crystal display panel 110. Yes. Therefore, the configuration of the optical function sheet group 145 is not limited to the diffusion sheet 142, the prism sheet 143, and the polarization conversion sheet 144 described above, and various optical function sheets can be used.

  FIG. 3 shows a schematic configuration diagram in the backlight housing 120. As shown in FIG. 3, the backlight casing 120 includes a red light emitting diode 21R that emits red light, a green light emitting diode 21G that emits green light, and a blue light emitting diode 21B that emits blue light. Is arranged as. For example, the peak wavelengths of red light emitted from the red light emitting diode 21R, green light emitted from the green light emitting diode 21G, and blue light emitted from the blue light emitting diode 21B are about 640 nm, 530 nm, and 450 nm, respectively. The peak wavelengths of red light and blue light emitted by the red light emitting diode 21R and the blue light emitting diode 21B may be shifted from 640 nm to the long wavelength side and from 450 nm to the short wavelength side, respectively. In this way, when the peak wavelength is shifted to the long wavelength side and the short wavelength side, the color gamut can be expanded, so that the color reproduction range of the image displayed on the color liquid crystal display panel can be expanded.

  In the following description, when the red light emitting diode 21R, the green light emitting diode 21G, and the blue light emitting diode 21B are collectively referred to, they are simply referred to as the light emitting diode 21. Further, in this example, the light emitting diode 21 having radiation directivity for radiating light emitted from a light source such as a light emitting diode chip from the side surface is used, but the light emitting diode is not limited to this, You may use what has other radiation directivity.

As shown in FIG. 3, the light emitting diodes 21n (n is a natural number) as a light emitting element array are formed by arranging a plurality of the light emitting diodes 21 in a desired order on the substrate 22 as shown in FIG. .
In order to form the light emitting diode unit 21n, the order in which the light emitting diodes 21 are arranged on the substrate 22 is the most basic arrangement method with the red light emitting diode 21R, the green light emitting diode 21G, and the blue light emitting diode 21B as repeating units. There are various arrangement methods such as arranging green light emitting diodes 21G at equal intervals and arranging red light emitting diodes 21R and blue light emitting diodes 21B alternately between adjacent green light emitting diodes 21G.

As shown in FIG. 3, the light emitting diode unit 21n may be arranged in the backlight housing 120 so that the longitudinal direction of the light emitting diode unit 21n is in the horizontal direction. The units 21n may be arranged so that the longitudinal direction thereof is the vertical direction, and the rows of the light emitting diode units may not be arranged on a straight line. Further, the light emitting diode 21 may be directly attached to the backlight housing 120 without using the wiring board 22. In addition, since the method of arranging the longitudinal direction of the light emitting diode unit 21n in the horizontal direction is the same as the CCFL arrangement method used as the light source of the conventional backlight device, the accumulated design know-how is used. It is possible to reduce the cost and the time required for manufacturing.
In addition, the inner wall surface 120a of the backlight housing 120 is a reflective surface or a diffuse reflective surface that has been subjected to reflection processing in order to increase the utilization efficiency of the light emitted from the light emitting diode 21.

  FIG. 4 is a partial cross-sectional view taken along the line XX attached to the transmissive color liquid crystal display device 100 shown in FIG. 1 when the transmissive color liquid crystal display device 100 is assembled. As shown in FIG. 4, a color liquid crystal display panel 110 constituting the liquid crystal display device 100 includes spacers 103 a and 103 b formed by an external frame 101 that is an external housing of the transmissive color liquid crystal display device 100 and an internal frame 102. It is hold | maintained so that it may pinch | interpose through. A guide member 104 is provided between the outer frame 101 and the inner frame 102, and the color liquid crystal display panel 110 sandwiched between the outer frame 101 and the inner frame 102 is displaced in the longitudinal direction. Is suppressed.

  On the other hand, the backlight device 140 constituting the transmissive color liquid crystal display device 100 is provided so as to cover the diffusion plate 141 on which the optical function sheet group 145 is laminated and the light emitting diode 21n as the light source, as described above. A light guide plate (diverter plate) 125 formed of a transparent resin substrate for mixing red (R) light, green (G) light, and blue (B) light emitted from each light emitting diode 21 is provided. . In addition, a reflection sheet 126 is disposed between the light guide plate 125 and the backlight housing 120. The light guide plate 125 has a color mixing function, and diffuses the light emitted from the light emitting diode 21 and the light reflected by the reflection sheet 126.

  A planar optical element 23 for controlling the light emitted from each light emitting diode is provided on the light incident surface 125 a of the light guide plate 125. The optical element 23 has a function of positively controlling, for example, the refraction angle and traveling direction of light incident on the light guide plate 125.

  The reflection sheet 126 is disposed so that the reflection surface thereof faces the light incident surface 125 a of the light guide plate 125 and is closer to the backlight housing 120 than the light emitting direction of the light emitting diode 21. As the reflection sheet 126, for example, a silver-enhanced reflection film formed by sequentially laminating a silver reflection film, a low refractive index film, and a high refractive index film on a sheet base material can be used. The reflection sheet 126 reflects light emitted mainly from the light emitting diode 21 and emitted downward due to the radiation angle distribution, light reflected by the reflection surface 120a of the backlight housing 120, and the like.

  As shown in FIG. 4, the diffusion device 141, the light guide plate 125, and the reflection sheet 126 included in the backlight device 140 are arranged so as to face each other, and a plurality of optical units provided in the backlight housing unit 120. The studs 105 are held in the backlight casing 120 of the backlight device 140 while maintaining the mutually facing distance. At this time, the end of the diffusing plate 141 is held by the bracket member 108 provided in the backlight housing 120.

FIG. 5 is an enlarged view of the vicinity of where the color liquid crystal display device 100 shown in FIG. 4 is provided with the Fresnel lens 23a of the planar optical element used in the first embodiment of the present invention.
As shown in FIG. 5, a Fresnel lens 23 a as a planar optical element is provided on the lower surface of the light guide plate 125 so as to be positioned directly above the light emitting diode 21. The Fresnel lens 23a is directly formed on the lower surface of the light guide plate 125 by a hot press method or the like.

  The light L1 emitted directly upward from a light emitting diode chip (not shown) of the light emitting diode 21 is primarily refracted in a predetermined direction when entering the Fresnel lens 23a. The refracted light L2 travels in the light guide plate 125 toward the top surface of the light guide plate. The refracted light L2 is second-order refracted when entering the space 127 that exists between the light guide plate 125 and the diffusion plate 141. The refracted light L3 travels through the space 127 toward the diffusion plate 141 and enters the diffusion plate 141.

FIG. 6 is a schematic diagram showing how the light L1 incident on the Fresnel lens 23a shown in FIG. 5 is refracted.
As shown in FIG. 6, minute irregularities 24 are formed on the surface of the Fresnel lens 23a. The light L1 emitted from the light emitting diode 21 enters the concavo-convex portion 24 of the Fresnel lens and primary refraction occurs. In this case, the angle at which the incident light is refracted can be controlled by adjusting the angle of the concavo-convex portion 24 provided in advance on the Fresnel lens.

  The first-order refracted light L2 travels through the light guide plate 125 while maintaining a parallel interval, and performs second-order refraction on the surface of the light guide plate 125 on the diffusion plate 141 side. The second-order refracted light L3 travels through the space 127 while maintaining a parallel interval, and is incident on the diffusion plate 141. As shown in FIG. 6, the refracted light L3 traveling through the space 127 has a spherical waveform L4 with no irregularities on the wavefront.

  Thus, according to the backlight device 140 of this example, the Fresnel lens 23a that controls the refraction angle of the incident light is provided on the light guide plate 125, so that the light emitted from the light emitting diode 21 in the upward direction is diffused. Since it can be converted into light having a spherical waveform before entering the plate 141, luminance unevenness and color unevenness in the backlight can be eliminated. In addition, luminance unevenness that occurs with thinning, color unevenness and opposite phase waveforms are added to the above spherical waveform to add together, even when the backlight device and liquid crystal display device are thinned, luminance unevenness, Color unevenness can be prevented.

FIG. 7 is an enlarged view when the diffraction grating 23b of the planar optical element used in the example of the second embodiment of the present invention is provided in the color liquid crystal display device 100 shown in FIG.
As shown in FIG. 7, the diffraction grating 23 b as a planar optical element is provided on the lower surface of the light guide plate 125 so as to be positioned right above the light emitting diode 21. A diffusion surface 125 c is provided on the upper surface of the light guide plate 125. The diffraction grating 23b is formed by a printing method, an imprinting method, a lithography method using a photomask, a two-beam interference method, or the like. The diffusion surface 125c is formed by sandblasting, but may be formed by attaching a diffusion sheet to the upper surface of the light guide plate 125.

  The light L1 emitted right above from a light emitting diode chip (not shown) of the light emitting diode 21 is diffracted into zero-order light, first-order light, second-order light, and the like when entering the diffraction grating 23b. The diffracted light L2 travels in the light guide plate 125 toward the top surface of the light guide plate. The diffraction L2 is finely diffused as indicated by an arrow L3 shown in FIG. 7 when entering the diffusion surface 125c provided on the upper surface of the light guide plate 125. The diffused light L <b> 3 travels toward the diffuser plate 141 through the space 127 existing between the light guide plate 125 and the diffuser plate 141 and enters the diffuser plate 141.

FIG. 8 is a schematic diagram showing how the light L1 incident on the diffraction grating 23b shown in FIG. 7 diffracts.
As shown in FIG. 8, a minute grating portion 25 is formed on the surface of the diffraction grating 23b. The light L1 emitted from the light emitting diode 21 enters the grating portion 25 of the diffraction grating 23b, and is diffracted into zero-order light, first-order light, and second-order light. That is, the diffracted light L2 traveling through the light guide plate 125 is light having a wavefront having irregularities, as shown in FIG.

  The diffracted light L2 having an uneven wavefront enters and diffuses into a diffusion surface 125c provided on the upper surface of the light guide plate 125. As a result, as shown in FIG. 8, the diffused light L3 is converted into light L4 having a smooth wavefront with no irregularities on the wavefront, travels through the space 127, and enters the diffuser plate 141.

  Thus, according to the backlight device 140 of this example, the diffraction grating 23b that controls the diffraction of light incident from the light emitting diode is provided on the light guide plate 125, and the diffusion surface that smoothes the diffracted light is provided. The light emitted directly from the light emitting diode 21 can be converted into light having a smooth wavefront before entering the diffuser plate 141, and luminance unevenness and color unevenness in the backlight can be reduced. In addition, brightness unevenness and color unevenness that occur with thinning are added to the above smooth waveform to add the uneven brightness even when the backlight and liquid crystal display devices are thinned. Color unevenness can be prevented.

FIG. 9 is an enlarged view when the phase difference plate 23c of the planar optical element used in the example of the third embodiment of the present invention is provided in the color liquid crystal display device 100 shown in FIG.
As shown in FIG. 9, a phase difference plate 23 c as a planar optical element is provided on the lower surface of the light guide plate 125 so as to be positioned directly above the light emitting diode 21. The retardation plate 23 c is formed by attaching a retardation film to a part of the light guide plate 125.

  Light L1 emitted right above from a light emitting diode chip (not shown) of the light emitting diode 21 is light whose phase is aligned in a certain direction determined by the attaching direction of the phase difference plate when passing through the phase difference plate 23c. Only passes and the rest is absorbed or reflected. The light L2 having the same phase of light travels toward the diffusion plate 141 in the space 127 that exists between the light guide plate 125 and the diffusion plate 141. Then, after entering the diffusion plate 141, the light passes through the group of optical function sheets 145 and reaches the liquid crystal display panel 100. Some optical function sheets have a retardation plate function. Therefore, by adjusting the angle between the phase of the optical function sheet and the phase of the retardation plate 23c, the light passing through the optical function sheet can be adjusted. The amount of passage can be controlled.

  As described above, according to the backlight device 140 according to this example, the light emitted from the light emitting diode 21 in the upward direction is provided by providing the phase difference plate 23c on the light guide plate 125 and using the phase difference with the optical function sheet. Can be reduced when passing through the optical function sheet, and luminance unevenness and color unevenness in the backlight can be reduced.

  The transmissive color liquid crystal display device 100 having such a configuration is driven by a drive circuit 200 as shown in FIG. 10, for example. The drive circuit 200 includes a color liquid crystal display panel 110, a power supply 210 that supplies drive power to the backlight device 140, and an X driver circuit 220 and a Y driver circuit 230 that drive the color liquid crystal display panel 110. Further, the drive circuit 200 receives an image signal supplied from the outside or an image signal received by a receiving unit (not shown) included in the transmissive color liquid crystal display device 100 and processed by the image signal processing unit via the input terminal 240. The RGB process processing unit 250 supplied, the image memory 260 connected to the RGB process processing unit 250, the control unit 270, the backlight drive control unit 280 for driving and controlling the backlight device 140, and the like.

  In the driving circuit 200, the video signal input via the input terminal 240 is subjected to signal processing such as chroma processing by the RGB process processing unit 250. Further, the video signal subjected to signal processing is converted from the composite signal to the color signal. It is converted into an RGB separate signal suitable for driving the liquid crystal display panel 110, supplied to the control unit 270, and supplied to the X driver 220 via the image memory 260.

  Further, the control unit 270 controls the X driver circuit 220 and the Y driver circuit 230 at a predetermined timing according to the RGB separate signal, and supplies the X driver circuit 220 together with the video signal from the image memory 260. By driving the color liquid crystal display panel 110 with the RGB separate signal, an image corresponding to the RGB separate signal is displayed.

The backlight drive control unit 280 generates a pulse width modulation (PWM) signal from the voltage supplied from the power supply 210 and drives each light emitting diode 21 that is a light source of the backlight device 140. In general, the color temperature of a light emitting diode has a characteristic that it depends on an operating current. Therefore, in order to reproduce the color faithfully (with a constant color temperature) while obtaining a desired luminance, it is necessary to drive the light emitting diode 21 using a pulse width modulation signal to suppress the color change.
The user interface 300 selects a channel to be received by a receiving unit (not shown) described above, adjusts an audio output amount to be output by an audio output unit (not shown), or from a backlight device 140 that illuminates the color liquid crystal display panel 110. This is an interface for executing brightness adjustment of white light, white balance adjustment, and the like.
For example, when the user adjusts the brightness from the user interface 300, the brightness control signal is transmitted to the backlight drive control unit 280 via the control unit 270 of the drive circuit 200. In response to the luminance control signal, the backlight drive control unit 280 changes the duty ratio of the pulse width modulation signal for each of the red light emitting diode 21R, the green light emitting diode 21G, and the blue light emitting diode 21B to change the red light emitting diode 21R, green The light emitting diode 21G and the blue light emitting diode 21B are driven and controlled.

FIG. 1 is an exploded perspective view of a color liquid crystal display device shown as an example for carrying out the present invention. FIG. 2 is a plan configuration diagram of a color filter of a color liquid crystal display panel shown as an example for carrying out the present invention. FIG. 3 is a perspective configuration diagram of a backlight device shown as an example for implementing the present invention. FIG. 4 is a schematic sectional view of a color liquid crystal display device shown as an example for carrying out the present invention. FIG. 5 is a partial schematic cross-sectional view of a color liquid crystal display device to which the Fresnel lens according to the first embodiment of the present invention is applied. FIG. 6 is a schematic diagram showing a state of refraction of light incident on a Fresnel lens that is a planar optical element. FIG. 7 is a partial schematic cross-sectional view of a color liquid crystal display device to which the diffraction grating according to the second embodiment of the present invention is applied. FIG. 8 is a schematic diagram showing a state of refraction of light incident on the diffraction grating which is the planar optical element shown in FIG. FIG. 9 is a partial schematic cross-sectional view of a color liquid crystal display device to which a retardation plate according to a third embodiment of the present invention is applied. FIG. 10 is a schematic block diagram of a driving circuit for driving a color liquid crystal display device as an example for carrying out the present invention.

Explanation of symbols

  21 .. Light emitting diode, 21 n... Light emitting diode unit, 23 .. Optical element, 23 a .. Fresnel lens, 23 b .. Diffraction grating, 23 c .. Phase plate, 100 .. Liquid crystal display device, 110. Panel 120 ··· Backlight casing 125 ··· Light guide plate 126 ··· Light guide sheet 140 ··· Backlight device 141 ··· Diffusion plate

Claims (9)

A backlight device for illuminating a liquid crystal display panel from the back side,
A point light source as a light source;
A transparent plate is provided above the point light source,
A backlight device, wherein a planar optical element having a function of controlling a traveling direction of light emitted from the point light source is provided on the transparent plate. The backlight device according to claim 1, wherein the transparent plate is provided with a diffusion portion positioned above the planar optical element. The backlight device according to claim 1, wherein the planar optical element is a diffraction grating. The backlight device according to claim 2, wherein the planar optical element is a diffraction grating. The backlight device according to claim 1, wherein the planar optical element is a Fresnel lens. The backlight device according to claim 2, wherein the planar optical element is a Fresnel lens. The backlight device according to claim 1, wherein the planar optical element is a polarizing element. The backlight device according to claim 2, wherein the planar optical element is a polarizing element. A liquid crystal display device comprising a liquid crystal display panel and a backlight device that illuminates the liquid crystal display panel from the back side,
The backlight device includes a point light source as a light source,
A transparent plate is provided above the point light source,
A liquid crystal display device, wherein a planar optical element having a function of controlling a traveling direction of light emitted from the point light source is provided on the transparent plate.

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