JP2006221954A - Light source device and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light source device with the high use efficiency of light emitted by a light source. <P>SOLUTION: In the light source device, a plurality of LED chips 100 (solid emission light source chips) in each of which the intensity distribution of injection light has directivity are arranged in parallel. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a light source device and an image display device such as a projector including the light source device.

In recent years, solid-state light sources such as light emitting diodes (hereinafter, abbreviated as LEDs) with a large amount of light emission have been developed, and projectors using these as light sources have been studied. Solid-state light-emitting light sources such as LEDs are more efficient, consume less power, have a longer service life, and are more reliable than thermoluminescent halogen lamps and discharge-type metal halide lamps that have been used as light sources for conventional projectors. Although it has features, it is still under development and its performance is improving. However, it has the problem that the amount of light emitted is small compared to conventional thermoluminescent and discharge lamps, and the desired brightness cannot be obtained. Was.
Therefore, Patent Document 1 below proposes a configuration of a light source device that increases the luminance by arranging a plurality of LED light sources in an array.
JP 2001-305657 A

  However, when the number of light sources is increased, the area of the entire light emitting unit increases, but there is a limit to the amount of light flux that can be captured by the illuminated system side. is there. Patent Document 1 describes that light is collimated (parallelized) using a shell-type package having a lens function, and only light in a certain angle range is used. However, when the light emitted isotropically from the LED chip is collimated by the lens, the angular distribution of the emitted light is certainly narrowed, but this is equivalent to an increase in the image of the light emitting part, that is, an increase in the area of the light emitting part. Therefore, after all, the problem that the amount of available light flux does not increase remains unsolved.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a light source device with high utilization efficiency of light emitted from a light source. It is another object of the present invention to provide an image display device capable of bright display by adopting the light source device as described above.

  In order to achieve the above object, the light source device of the present invention is characterized in that a plurality of solid state light source chips having a directivity in the intensity distribution of emitted light are arranged in parallel.

  In an optical system such as an image display device, a spatial spread in which a light beam that can be handled effectively exists can be expressed as a product of an area and a solid angle (hereinafter referred to as etendue), and the etendue is stored in the optical system. . Here, if the area of the illuminated region of the light modulation device of the image display device is S ′ and the solid angle of incident light that can be captured by the illuminated region is Ω ′, the etendue on the illuminated region side, that is, S ′ × Ω ′. The value of is determined by design. As described above, since the etendue is stored, if the light emitting area of the light source device is S and the solid angle of the emitted light is Ω, the etendue on the light source device side, that is, the value of S × Ω is the value of S ′ × Ω ′. If it is smaller than that, all the light from the light source device will be used. However, if the value of S × Ω is larger than the value of S ′ × Ω ′, the larger amount of light is wasted. Therefore, it is preferable for the effective use of light that the etendue (S × Ω) on the light source device side is as small as possible.

  In that respect, in the present invention, the intensity distribution of the light emitted from the solid state light source (for example, LED) chip constituting the light source device has directivity. That is, the intensity of the emitted light is not equal isotropic light emission (Lambert) in all directions, but is increased only in a predetermined direction, which is equivalent to a reduction in the solid angle Ω of the emitted light. Thereby, the etendue of the light source device can be reduced, and as a result, the light emission area S can be increased within a range not exceeding the etendue (S ′ × Ω ′ value) on the illuminated region side. Therefore, a plurality of solid state light source chips having directivity in the intensity distribution of emitted light can be arranged in parallel, and a light source device with high utilization efficiency of light emitted from the light source can be provided.

Further, the light at the predetermined radiation solid angle of the isotropic light source in which the maximum value of the light intensity at the predetermined radiation solid angle of the emitted light from the solid light source is equal to the amount of light flux in the whole emitted light is equal to that of the solid light source. It is desirable that the intensity is greater than the maximum value.
According to this configuration, the luminance can be improved as compared with a case where an isotropic light source having the same luminous flux amount as that of the solid light source is used.

An image display device of the present invention includes the light source device of the present invention, a light modulation device that modulates light from the light source device, and a projection lens that projects light modulated by the light modulation device. Features.
According to this configuration, it is possible to realize an image display device capable of bright display by employing the light source device of the present invention.

[Light source device]
Hereinafter, a light source device as an embodiment of the present invention will be described with reference to FIGS.
1 is a plan view of the light source device of the present embodiment, FIG. 2 is a cross-sectional view taken along line AA ′ of FIG. 1, FIG. 3 is a perspective view of an LED chip constituting the light source device, and FIG. FIG. 5 is a diagram for explaining the operation, and FIG. 5 is a diagram showing an intensity distribution of light emitted from the LED chip.
In each of the following drawings, the ratio of dimensions of each component is appropriately changed in order to make it easy to recognize each component.

  As shown in FIGS. 1 and 2, the light source device 1 of the present embodiment includes a plurality of LED chips 100 (solid-state light-emitting light source chips) arranged in parallel on a base substrate 3, the intensity distribution of emitted light having directivity. Yes. In this example, six LED chips 100 are arranged in an array in 2 rows and 3 columns in plan view. Normally, a single LED chip basically emits light isotropically, but in the case of this embodiment, the intensity distribution of emitted light has directivity by the following configuration. 1 and 2 are diagrams showing only an image of the arrangement of the plurality of LED chips 100, and the specific configurations of the quadrangular pyramid prisms, electrodes, wirings, packages, and the like described below are not shown. Yes.

  FIG. 3 is a perspective view of the LED chip 100 according to the present embodiment. FIG. 4 shows a cross-sectional configuration of the LED chip 100. In FIG. 4, a surface light emitting unit 101 is formed by growing a crystal of Ga, In, N or the like on a sapphire substrate 102, and a bonding wire 103 is provided at an end of the surface light emitting unit 101. The surface light emitting unit 101 emits light from the flat light emitting region 101a with substantially equal intensity in all directions. That is, the surface light emitting unit 101 itself functions as a so-called Lambertian surface. A reflective metal electrode 106 that is a reflective portion is provided on one surface side of the surface light emitting portion 101. A square pyramid prism 104 made of an optically transparent member such as a high refractive index glass is fixed to the other surface side of the surface light emitting portion 101 with an optical adhesive. A diffusing plate 107 that scatters incident light is provided on the bottom surface 104 a of the quadrangular pyramid prism 104.

  Next, the behavior of light emitted from the surface light emitting unit 101 in the above configuration will be described. The bottom surface 104a of the quadrangular pyramid prism 104 has a substantially square shape. The bottom surface 104a has substantially the same size and shape as the substantially square planar light emitting region 101a. Further, the refractive index n of the quadrangular pyramid prism 104 made of high refractive index glass may be substantially the same as or higher than the refractive index of the sapphire substrate 102. Preferably, the refractive index n of the quadrangular pyramid prism 104 is at least 1.45 or more. More preferably, the refractive index n of the quadrangular pyramid prism 104 is 1.77. Thereby, the light emitted from the surface light emitting unit 101 and traveling in the sapphire substrate 102 is not totally reflected at the interface between the sapphire substrate 102 and the bottom surface 104 a of the quadrangular pyramid prism 104. For this reason, the light from the surface light emitting unit 101 efficiently enters the quadrangular pyramid prism 104 from the bottom surface 104a.

  Since the surface light emitting unit 101 is a Lambertian surface as described above, it emits light having substantially the same intensity in all directions from the light emitting point. Light that has entered the quadrangular pyramid prism 104 from the bottom surface 104a travels in the quadrangular pyramid prism 104 and reaches the inclined surface 105a. Here, depending on the incident angle to the inclined surface 105a, there are cases where the light is refracted at the interface between the inclined surface 105a and an external medium, for example, air, and there is a case where the light is reflected at the interface. For example, the light L1 is refracted at the interface of the inclined surface 105a at the position P1 and is emitted in a specific direction.

  On the other hand, the light L2 is reflected without being refracted at the interface of the inclined surface 105a at the position P2. The light reflected at the position P2 further travels in the quadrangular pyramid prism 104. The light L2 reflected by the slope 105a travels through the quadrangular pyramid prism 104 and reaches another different slope 105b. When the light L2 is reflected at the position P3 on another different inclined surface 105b, the optical path is further changed and the light L2 travels in the quadrangular pyramid prism 104 toward the bottom surface 104a. The light transmitted through the bottom surface 104 a and returning to the surface light emitting unit 101 further passes through the surface light emitting unit 101. The light transmitted through the surface light emitting unit 101 is applied to the reflective metal electrode 106 which is a reflecting unit provided on one surface side of the surface light emitting unit 101, that is, the surface opposite to the surface on which the quadrangular pyramid prism 104 is provided. Incident. The light L2 incident on the reflective metal electrode 106 is reflected again by the reflective metal electrode 106 toward the quadrangular pyramid prism 104.

  The light L2 reflected again passes through the surface light emitting unit 101 and enters the quadrangular pyramid prism 104 again from the bottom surface 104a. As such reflection is repeated a plurality of times, the angle of incidence on the slope 105b of the prism differs from the angle of incidence on the slope 105b for the first time. For this reason, the light L2 having an angle that can be refracted by the inclined surface 105b is refracted by the inclined surface 105b and emitted in a specific direction. Further, when the light is reflected without being refracted by the slope 105b, the above-described reflection process is further repeated until the light is refracted by the slopes 105a and 105b and emitted. Therefore, if light absorption in the quadrangular pyramid prism 104 and the reflective metal electrode 106 is ignored, all the light emitted from the surface light emitting unit 101 can be emitted in a specific direction. Thereby, directivity can be given to the intensity distribution of the emitted light.

  FIG. 5 shows the difference in intensity distribution of the emitted light between the LED chip 100 having the quadrangular pyramid prism of the present embodiment and a normal LED chip. The intensity distribution of the emitted light of the normal LED chip is isotropic light emission (Lambert) as indicated by a dashed circle, whereas the intensity distribution of the emitted light of the LED chip 100 provided with the quadrangular pyramid prism of the present embodiment. Has directivity having a high intensity distribution in the normal direction of the chip surface (light emitting surface) as indicated by a solid oval. From the viewpoint of etendue, this is equivalent to the narrow solid angle Ω of the emitted light. Therefore, according to Etendue's conservation law, the area S can be increased by the amount that the solid angle Ω of the emitted light is reduced. That is, the number of LED chips can be increased and a plurality of LED chips can be arranged in an array as in the present embodiment.

  In the case of this embodiment, not only the LED chip has directivity but also the maximum value E1 of the light intensity at a predetermined radiation solid angle Ω of the light emitted from the LED chip as shown in FIG. The amount of light flux in the whole emitted light is larger than the maximum value E2 of the light intensity at a predetermined radiation solid angle of the isotropic light emitting LED equal to this LED chip. Therefore, the luminance can be improved as compared with the case where an isotropic light emitting LED is used.

  The inventor obtained a change in the amount of light flux with respect to the number of light sources by simulation for the case of using the LED chip of the present embodiment and the case of using the isotropic LED chip. FIG. 6 shows the simulation results, where the horizontal axis represents the number of light sources (pieces) and the vertical axis represents the amount of light flux (no unit, relative amount). In FIG. 6, the triangle mark (Δ) indicates an isotropic LED chip, and the circle mark (◯) indicates the LED chip of the present embodiment. As is apparent from the figure, in the case of an isotropic light emitting LED chip, the amount of light flux does not increase even if the number of light sources is increased, that is, the brightness cannot be improved. On the other hand, in the case of the LED chip of this embodiment, it was found that the amount of light flux increases as the number of light sources increases, that is, the brightness can be improved.

  As described above, in the light source device of the present embodiment, the light use efficiency can be improved and the luminance can be increased as compared with the case where the isotropic light source is used. Further, since the distance between the chips can be reduced when arraying a plurality of LED chips, the loss at the time of arraying can be reduced.

[projector]
Hereinafter, as an embodiment of the present invention, a projector (image display device) including the light source device of the above embodiment will be described.
FIG. 7 is an explanatory diagram of a projector 500 including the light source device of the above embodiment. In the figure, reference numerals 512, 513, and 514 denote light source devices of the above-described embodiment, 522, 523, and 524 denote liquid crystal light valves (light modulation means), 525 denotes a cross dichroic prism (color light synthesis means), and 526 denotes a projection lens (projection means). ).

  The projector 500 shown in FIG. 7 includes three light source devices 512, 513, and 514 configured as in the present embodiment. LED chips 100R, 100G, and 100B that emit light in red (R), green (G), and blue (B) are employed for the light source devices 512, 513, and 514, respectively. In addition, rod lenses 535R, 535G, and 535B are arranged behind each light source device as a uniform illumination system for making the illuminance distribution of the light source light uniform. The light beam from the red light source device 512 passes through the rod lens 535R and the relay lens 536R and enters the liquid crystal light valve 522 for red light. Further, the light beam from the green light source device 513 passes through the rod lens 535G and the relay lens 536G and enters the liquid crystal light valve 523 for green light. The light beam from the blue light source device 514 passes through the rod lens 535B and the relay lens 536B and enters the liquid crystal light valve 524 for blue light.

  In addition, polarizing plates (not shown) are disposed on the incident side and the emission side of each liquid crystal light valve 522, 523, 524. Of the light beams from the light source devices 512, 513, and 514, only linearly polarized light in a predetermined direction passes through the incident side polarizing plate and enters the liquid crystal light valves 522, 523, and 524. Further, a polarization conversion means (not shown) may be provided in front of the incident side polarizing plate. In this case, the light beam reflected by the incident side polarizing plate can be recycled and made incident on the liquid crystal light valves 522, 523, and 524, and the light use efficiency can be improved.

  The three color lights modulated by the liquid crystal light valves 522, 523, and 524 are incident on the cross dichroic prism 525. This prism is formed by bonding four right-angle prisms, and a dielectric multilayer film that reflects red light and a dielectric multilayer film that reflects blue light are arranged in a cross shape on the inner surface thereof. These dielectric multilayer films combine the three color lights to form light representing a color image. The synthesized light is projected onto the projection screen 527 by the projection lens 526 which is a projection optical system, and an enlarged image is displayed.

  The light source devices 512, 513, and 514 of the present embodiment described above have high light use efficiency and can supply high-luminance light. Therefore, by providing the light source devices 512, 513, and 514 described above, a projector capable of bright display can be provided.

  The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the above embodiment, as a means for imparting directivity to the intensity distribution of the light emitted from the LED, a device having a quadrangular pyramid prism is employed. Instead, for example, the refractive index is provided on the light emitting surface of the LED chip. You may use what made distribution structure, a diffraction grating, etc. built-in.

It is a top view of the light source device which is one Embodiment of this invention. It is sectional drawing which follows the A-A 'line of FIG. It is a perspective view of the LED chip which comprises a light source device equally. It is a figure for demonstrating the effect | action of an LED chip. It is a figure which shows intensity distribution of the emitted light from an LED chip. It is the simulation result of the change of the light beam quantity with respect to the number of light sources in the case where the LED chip of this embodiment is used and the case where the isotropic light emitting LED chip is used. It is a schematic block diagram of the projector of one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,512,513,514 ... Light source device, 100, 100R, 100G, 100B ... LED chip (solid light-emitting light source chip), 500 ... Projector (image display device).

Claims (3)

  A light source device comprising a plurality of solid-state light emitting light source chips having directivity in intensity distribution of emitted light arranged in parallel.   The maximum value of the light intensity at a predetermined radiation solid angle of the emitted light from the solid-state light source is the light intensity at the predetermined radiation solid angle of the isotropic light source in which the amount of light flux in the entire emitted light is equal to the solid light source. The light source device according to claim 1, wherein the light source device is larger than a maximum value. An image comprising: the light source device according to claim 1; a light modulation device that modulates light from the light source device; and a projection lens that projects light modulated by the light modulation device. Display device.

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