JP2005062446A - Lighting system and projection type display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lighting system whereby illumination efficiency is improved by illuminating a specific area with light having a predetermined range of incident angle, and to provide a projection type display device using the lighting system. <P>SOLUTION: The lighting system includes: a light source 10; a collimator lens 20 disposed on one of the light emission sides of the light source 10; and an elliptic reflector 30 disposed on the other of the light emission sides of the light source 10. The collimator lens 20 is disposed such that the position of the front focal point 22 of the collimator lens 20 and the position of the light emitting part of the light source 10 or the position of a virtual image formed by the lens effect of the package of the light source 10 are substantially the same. The elliptic reflector 30 is disposed such that the position of the first focal point 32 of the reflector 30 and the position of the light emitting part or virtual image are substantially the same and also the position of the second focal point 33 of the reflector 30 and the position of the front main point 21 of the collimator lens 20 are substantially the same. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an illumination device and a projection display device.

Projection-type display devices such as projectors are widely known in which light emitted from an irradiation device is incident on light modulation means such as a liquid crystal light valve, and image light emitted from the light modulation means is enlarged and projected onto a screen by a projection lens or the like. It has been. Fig.5 (a) is side sectional drawing of the illuminating device based on a prior art. The lighting device 100 is provided with a light source 110. In general, the light source 110 emits light radially. Therefore, a reflector (concave mirror) 120 that reflects light irradiated radially from the light source backward (downstream) is provided on the side of the light source 110. In addition, when the incident angle of light with respect to light modulation means such as a liquid crystal light valve increases, there arises a problem that the contrast ratio of the image is lowered. Therefore, a parabolic reflector 120 in which the reflected light becomes parallel light is employed.
Japanese Patent Application Laid-Open No. 10-311944

However, the light 140 emitted from the light source 110 at an angle equal to or greater than the predetermined angle α with respect to the optical axis is incident on the reflector 120, but the light 142 irradiated at an angle equal to or smaller than the predetermined angle α is not incident on the reflector 120. And the light 142 which does not enter into the reflector 120 goes straight radially, and is not utilized for the image display of a projection type display apparatus. Therefore, there is a problem that the light use efficiency is low.
The intensity of light emitted from the light source tends to be stronger as the angle with respect to the optical axis is smaller and weaker as the angle is larger. For this reason, if the light irradiated at an angle less than or equal to the predetermined angle α with respect to the optical axis cannot be used, the light use efficiency is significantly reduced. Further, in a projection display device such as a projector, it is an important problem to ensure the luminance of an image projected on a screen. Therefore, a decrease in light utilization efficiency has a significant effect on the performance of the projection display device.

  On the other hand, Patent Document 1 discloses an illumination device using a concave lens. FIG. 5B is a side cross-sectional view of the illumination device according to Patent Document 1. In the illumination device 200, the light emitting unit of the lamp 210 is disposed at the first focal position of the elliptical reflector 220. A concave lens 230 is disposed between the first focal position and the second focal position of the reflector 220. The light 240 irradiated from the lamp 210 and reflected by the reflector 220 is incident on the concave lens 230 on the way to the second focal position, and is refracted in the negative direction to become substantially parallel light. On the other hand, the light 242 irradiated from the lamp 210 and directly incident on the concave lens 230 is emitted from the concave lens 230 as divergent light.

  However, the configuration of Patent Document 1 has a problem in that an image of the light emitting unit cannot be formed at the front focal point of the concave lens 230 because the glass portion covering the light emitting unit of the lamp 210 has a lens effect. Moreover, since the light irradiated from the lamp 210 and directly incident on the concave lens 230 becomes diverging light, it is difficult to illuminate a predetermined area to be illuminated with light having an incident angle within a predetermined angle. That is, there is a problem that it is difficult to ensure sufficient light use efficiency.

  The present invention has been made to solve the above-described problem, and an illumination device capable of improving illumination efficiency by illuminating a predetermined region with light having an incident angle within a predetermined angle, and the same An object of the present invention is to provide a projection type display device using the above-mentioned.

  In order to achieve the above object, an illuminating device of the present invention includes a light source, a collimator lens disposed on one light exit surface side of the light source, and an elliptic reflector disposed on the other light exit surface side of the light source. The collimator lens is disposed at a position where a front focal position of the collimator lens and a position of a virtual image formed by a lens effect of a light emitting unit in the light source or a package in the light source are substantially the same, and the elliptical reflector is The first focal position of the elliptical reflector and the position of the light emitting unit or the virtual image are substantially the same, and the second focal position of the elliptical reflector and the front principal point position of the collimator lens are substantially the same. It is characterized by that.

That is, in the illuminating device of the present invention, the position of the light emitting unit or the virtual image is substantially the same as the position of the front focal point, so that the light emitted from the light emitting unit and incident on the collimator lens is collimated by the collimator lens. . Therefore, a predetermined area can be illuminated with light having an incident angle within a predetermined angle, and the illumination efficiency can be improved.
In addition, since the position of the light emitting unit or the virtual image and the position of the first focus are substantially the same, and the position of the front principal point and the position of the second focus are substantially the same, the light is emitted from the light emitting unit. Light incident on the elliptical reflector is reflected so as to be condensed in the vicinity of the principal point position. Therefore, the incident angle at which the reflected light enters the predetermined area becomes small, and the predetermined area can be illuminated with light having an incident angle within a predetermined angle, so that the illumination efficiency can be improved.

More specifically, in order to realize the above configuration, it is desirable that the diameter of the elliptical reflector at the first focal position is approximately 1 to 1.5 times the maximum outer diameter of the light source.
According to this configuration, even if the diameter of the elliptical reflector at the first focal position is small, it is approximately one time the maximum outer diameter of the light source, so that all the light emitted from the light source to the elliptical reflector side is collimator lens. Can be reflected to the side. In addition, since the diameter at the first focal position is at most about 1.5 times the maximum outer diameter of the light source, the incident angle at which the light reflected by the elliptical reflector is incident on the predetermined area is illuminated. Can be prevented from becoming larger than a predetermined angle. Therefore, it is possible to secure light that illuminates a predetermined region with an incident angle within a predetermined angle, and it is possible to prevent a decrease in illumination efficiency.
Further, since the upper limit of the diameter at the first focal position is set to approximately 1.5 times the maximum outer diameter of the light source, the size thereof is not impaired without impairing the illumination efficiency as compared with a conventional illumination device having a parabolic reflector or the like. Can be reduced.

A projection display device according to the present invention is a projection display device including an illumination device, a light modulation unit that modulates light from the illumination device, and a projection unit that projects light modulated by the light modulation unit. The illumination device is the illumination device of the present invention.
That is, since the projection display apparatus of the present invention uses the illumination apparatus of the present invention, the incident angle of light incident on the light modulation means is within a predetermined angle, and a high quality image with a high contrast ratio is obtained. Can project.
In addition, since the size of the illumination device can be reduced, the size of the projection display device can also be reduced.

[Lighting device]
[First embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to FIG. 1 and FIG.
FIG. 1 is a side sectional view of the lighting device according to the present embodiment.
The illumination device 1 according to the present embodiment mainly includes a light source 10, a collimator lens 20 that refracts light emitted from the light source 10 and converts the light into parallel light, and an elliptic reflector that reflects light emitted from the light source 10. 30.

In the present embodiment, a solid light source such as a light emitting diode (hereinafter referred to as LED) element is used as the light source 10. The LED element is mainly composed of an LED chip in which a p-type semiconductor and an n-type semiconductor are joined, a pair of electrodes made of a conductive material such as Al, and a package made of a transparent material such as resin.
One end surface of the LED chip is surface bonded to the upper surface of one of the pair of electrodes. Moreover, the other end surface of the LED chip and the upper surface of one of the pair of electrodes are connected by wire bonding. The entire pair of electrodes and the LED chip are hermetically sealed by the package. This package uses a package having a shape or material that does not exhibit the lens effect due to the light emitted from the LED chip being refracted. For example, an example in which the shape of the light emitting side of the package is formed in a substantially planar shape that does not show a lens effect can be given. A lead frame is drawn from the pair of electrodes to the outside of the package, and electricity can be supplied from the outside.
The light source 10 may be a halogen lamp, a metal halide lamp, a high-pressure mercury lamp, or the like as well as a solid light source such as the LED element described above.

  An LED is a diode that emits light when a current flows through a junction. An LED with a simple homojunction structure is a p-type semiconductor and an n-type semiconductor crystal made of the same material. When a forward bias voltage is applied to the LED having a homojunction structure, electrons of the n-type semiconductor move to the p-type semiconductor, fall from a high energy conduction band to a low energy valence band, and recombine with holes. The energy lost at that time is released as light, and the LED emits light. Note that the color of emitted light depends on the energy difference (band gap) between the conduction band and the valence band, and the band gap is determined by the semiconductor material used. For example, if AlGaAs or the like is used, light is emitted in red, if GaP or the like is used, light is emitted in green, and if InGaN or the like is used, light is emitted in blue. Thus, the LED becomes a monochromatic light source.

  In addition, since LED of a homojunction structure has low luminous efficiency, it is preferable to employ | adopt LED of a double heterojunction structure or a quantum well junction structure for the light source 10. FIG. An LED having a double heterojunction structure is obtained by sandwiching an active layer having a small band gap between a p-type semiconductor and an n-type semiconductor. When a forward bias voltage is applied to an LED having a double heterojunction structure, electrons and holes are confined in the active layer to increase the density. Thereby, recombination is performed efficiently and high luminous efficiency can be obtained. In addition, an LED having a quantum well junction structure is obtained by sandwiching a plurality of semiconductor layers that are as thin as an electron wavelength (about 10 nm) between a p-type semiconductor and an n-type semiconductor. When a forward bias voltage is applied to an LED having a quantum well junction structure, only electrons and holes having a predetermined energy can be collected in the junction region. Thereby, recombination is performed efficiently and high luminous efficiency can be obtained. In addition, it is possible to obtain light that has a small wavelength width and is close to a single color. By adopting the LED having high luminous efficiency as a light source for a projection display device such as a projector as described above, it is possible to improve the luminance of the image and reduce the power consumption.

  As shown in FIG. 1, the collimator lens 20 is arranged on the system optical axis C on the surface side of the light source 10 in the light emitting direction (right direction in FIG. 1) of the illumination device 1. The distance (focal length) from the front principal point 21 to the front focal point 22 of the collimator lens 20 is f1, and the collimator lens 20 is arranged so that the front focal point 22 of the collimator lens 20 and the light emitting part of the light source 10 substantially coincide. Has been.

The elliptical reflector 30 is on the surface side of the light source 10 in the direction opposite to the light emitting direction of the illumination device 1 (leftward in FIG. 1), and the system optical axis C and the major axis of the elliptical reflector 30 are substantially coincident with each other. And it arrange | positions so that a concave surface may become the light source 10 side. The inner surface of the elliptical reflector 30 is in a mirror state so as to reflect light from the light source 10.
Further, if the point where the elliptical reflector 30 and the optical axis C intersect with the base point 31, the distance from the base point 31 to the first focal point 32 (first focal length) is f 2, and the distance from the base point 31 to the second focal point 33. The (second focal length) is f3. In the elliptical reflector 30, the first focal point 32 of the elliptical reflector 30 and the light emitting part of the light source 10 substantially coincide with each other, and the second focal point 33 of the elliptical reflector 30 and the front principal point 21 of the collimator lens 20 substantially coincide with each other. Has been placed.
Further, the diameter of the elliptical reflector 30 at the first focal point 32, that is, the diameter of a circle appearing on the cut surface obtained by cutting the elliptical reflector 30 at the first focal point 32 by a plane perpendicular to the system optical axis C is the maximum outer diameter of the light source 10. It is formed to be 1 to 1.5 times (diameter of the circumscribed circle of the light source 10). This is because when the diameter is smaller than 1 time, it becomes impossible to reflect all the light emitted from the light source 10 toward the elliptical reflector 30, and the light use efficiency is lowered. Further, when the diameter is larger than 1.5 times, the angle of the light reflected from the peripheral portion of the elliptical reflector 30 with respect to the system optical axis C is increased, and the light use efficiency is lowered.

Next, the effect | action in the illuminating device 1 which consists of said structure is demonstrated.
Of the light irradiated radially from the light source 10, the light 20 irradiated toward the collimator lens 20 is converted into parallel light 41 by the collimator lens 20 because the front focal point 22 is disposed in the light emitting portion of the light source 10. And emitted from the lighting device 1.
Further, the light 42 radiated radially from the light source 10 toward the elliptical reflector 30 is reflected so as to be condensed in the vicinity of the second focus 33 because the first focus 32 is disposed in the light emitting portion of the light source 10. Is done. The reflected light 43 has a small angle with respect to the system optical axis C, passes through the light source 10 and the collimator lens 20, and is emitted from the illumination device 1.

Next, the simulation result of the illumination efficiency in the illuminating device of this invention is demonstrated compared with the simulation result of the conventional illuminating device.
FIG. 2A is a schematic diagram of a model used for simulation of a conventional lighting device, and FIG. 2B is a schematic diagram of a model used for simulation of the lighting device of the present invention.
As a light source used for the simulation, a square LED chip having a length of 1 mm and a width of 1 mm was used, and a light distribution of light emitted from the LED chip was a Lambertian distribution.
In the conventional lighting device model, as shown in FIG. 2A, the mirror M is disposed on the back surface of the light source 10 and the collimator lens 20 is disposed in the light emitting direction. Thereby, the light emitted in the direction of the mirror M is reflected by the mirror M toward the collimator lens 20 side. The front focal point of the collimator lens 20 is located at the light emitting portion of the light source 10, and the light incident on the collimator lens 20 by the light emitted from the light source 10 is converted into parallel light and emitted from the collimator lens 20.
In the illumination device model of the present invention, as shown in FIG. 2B, the elliptic reflector 30 is disposed on the back surface of the light source 10 described above, and the collimator lens 20 is disposed in the light emitting direction. The diameter of the first focal point of the elliptical reflector 30 used for the simulation is 2 mm, which is approximately 1.42 times the outermost diameter (approximately 1.41 mm) of the light source 10. Further, since the relative positional relationship among the light source 10, the collimator lens 20, and the elliptical reflector 30 is the same as that in the first embodiment of the present invention described above, description thereof is omitted.

As the illumination efficiency, the ratio (%) of the amount of light emitted from the illumination device and incident on a predetermined area at a predetermined incident angle with respect to the amount of light emitted from the light source 10 is obtained.
As a result of simulating lighting efficiency in each lighting device based on the above conditions,
The illumination efficiency in the conventional illumination device was 49.8%, and the illumination efficiency in the illumination device of the present invention was 67%. That is, the illumination efficiency of the illumination device of the present invention was about 1.3 times higher than the conventional one.

According to the above configuration, since the position of the light emitting portion of the light source 10 and the position of the front focal point 22 are substantially the same, the light emitted from the light source 10 and incident on the collimator lens 20 is collimated by the collimator lens 20. Therefore, a predetermined area can be illuminated with light having an incident angle within a predetermined angle, and the illumination efficiency can be improved.
Further, since the position of the light emitting portion of the light source 10 and the position of the first focal point 32 are substantially the same, and the position of the front principal point 21 and the position of the second focal point 33 are substantially the same, the elliptical reflector emitted from the light source 10 is used. The light incident on 30 is reflected so as to be condensed near the position of the front principal point 21. Therefore, the angle of the reflected light with respect to the system optical axis C becomes small, and a predetermined area can be illuminated with light having an incident angle within a predetermined angle, and the illumination efficiency can be improved.

Even if the diameter of the elliptical reflector 30 at the position of the first focal point 32 is small, it is about one time the maximum outer diameter of the light source 10, so that all the light emitted from the light source 10 to the elliptical reflector 30 side is a collimator lens. It can be reflected to the 20 side.
In addition, even if the diameter is large, it is approximately 1.5 times the maximum outer diameter of the light source 10, so that the incident angle at which the reflected light is incident on the predetermined area illuminated is larger than the predetermined angle. Can be prevented. Therefore, it is possible to secure light that illuminates a predetermined region with an incident angle within a predetermined angle, and it is possible to prevent a decrease in illumination efficiency.
Furthermore, since the upper limit of the diameter is about 1.5 times the maximum outer diameter of the light source 10, it is possible to reduce the size without impairing the illumination efficiency as compared with a conventional illumination device having a parabolic reflector. it can.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIG.
The basic configuration of the lighting device in the present embodiment is the same as that of the first embodiment, but the configuration of the light source is different from that of the first embodiment. Therefore, in the present embodiment, only the periphery of the light source will be described using FIG. 3, and the description of the collimator lens and the like will be omitted.
FIG. 3 is a side sectional view of the lighting device according to the present embodiment.
In the present embodiment, a solid light source such as a light emitting diode (hereinafter referred to as LED) element is used as the light source 50. The LED element is mainly configured by an LED chip obtained by bonding a p-type semiconductor and an n-type semiconductor, a pair of electrodes made of a conductive material such as Al, and a package 51 made of a transparent material such as resin.
In the package 51, the light emitting direction (right direction in FIG. 3) of the lighting device 2 is formed on the convex curved surface 52, and the light emitted from the LED chip is refracted to exhibit a lens effect. The package 51 may be entirely formed of a thermosetting resin such as an epoxy resin, or may be formed by injecting gel or the like into the solid cover.

The collimator lens 20 is disposed so that the front focal point 22 of the collimator lens 20 and the position of the virtual image 53 of the light source 50 are substantially coincident with each other.
As shown in FIG. 3, the position of the virtual image 53 of the light source 50 indicates a position where the emission direction of the light 55 emitted from the light source 50 extends in the direction of the light source 50 along a straight line 56 and intersects. The virtual image 53 of the light source 50 is an image of the light source 50 that can be seen when the light source 50 is viewed from the light emitting direction of the illumination device.
The elliptic reflector 30 is configured so that the first focal point 32 of the elliptical reflector 30 and the virtual image 53 of the light source 10 substantially coincide, and the second focal point 33 of the elliptical reflector 30 and the front principal point 21 of the collimator lens 20 substantially coincide. Has been placed.

Next, the operation of the illumination device 2 having the above configuration will be described.
The light 54 emitted from the LED chip of the light source 50 propagates through the package 51 and is refracted at the convex curved surface 52 to be emitted from the light source 50 as light 55. Since the light 55 can be regarded as light emitted from the virtual image 53, the light 55 is converted into parallel light 41 by the collimator lens 20 and emitted from the illumination device 2 in the same manner as the light emitted from the front focal point 22.
Further, the light emitted radially from the light source 50 toward the elliptical reflector 30 is reflected toward the second focal point 33 side. The reflected light has a small angle with respect to the system optical axis C, passes through the light source 500 and the collimator lens 20, and is emitted from the illumination device 2.

According to the above configuration, since the position of the virtual image 53 and the position of the front focal point 22 are substantially the same, the light emitted from the light source 50 and incident on the collimator lens 20 is collimated by the collimator lens 20. Therefore, a predetermined area can be illuminated with light having an incident angle within a predetermined angle, and the illumination efficiency can be improved.
Further, since the position of the virtual image 53 and the position of the first focal point 32 are substantially the same, and the position of the front principal point 21 and the position of the second focal point 33 are substantially the same, the light is emitted from the light source 50 and applied to the elliptical reflector 30. Incident light is reflected so as to be condensed near the position of the front principal point 21. Therefore, the incident angle at which the reflected light enters the predetermined area becomes small, and the predetermined area can be illuminated with light having an incident angle within a predetermined angle, so that the illumination efficiency can be improved.

[Projection type display device]
FIG. 4 is an explanatory diagram of a projector including the illumination device according to the present invention. In the figure, reference numerals 512, 513, and 514 denote illumination devices, 522, 523, and 524 denote liquid crystal light valves (light modulation means), 525 denotes a cross dichroic prism, and 526 denotes a projection lens (projection means).

  The projector (projection display device) 500 in FIG. 4 includes three illumination devices 512, 513, and 514 configured as in the present embodiment. LED elements that emit red (R), green (G), and blue (B) light are used as the light sources of the illumination devices 512, 513, and 514, respectively. In addition, a rod lens or a fly-eye lens may be arranged behind each lighting 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 512 is reflected by the reflection mirror 517 via the superimposing lens 535R and enters the liquid crystal light valve 522 for red light. Further, the light beam from the green light source 513 enters the green light liquid crystal light valve 523 via the superimposing lens 535G. The light beam from the blue light source 512 is reflected by the reflection mirror 516 and enters the liquid crystal light valve 522 for blue light via the superimposing lens 535B. The light flux from each light source is superimposed on the display area of the liquid crystal light valve via the superimposing lens, and the liquid crystal light valve is illuminated uniformly.

  Further, polarizing plates (not shown) are arranged on the incident side and the emission side of each liquid crystal light valve. Then, only linearly polarized light in a predetermined direction out of the light flux from each light source passes through the incident side polarizing plate and enters each liquid crystal light valve. Further, a polarization conversion means (not shown) may be provided in front of the incident side polarizing plate. In this case, it is possible to recycle the light beam reflected by the incident-side polarizing plate and make it incident on each liquid crystal light valve, thereby improving the light utilization efficiency.

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

  As described above, since the use efficiency of the light source light is improved by the illumination device according to the present embodiment, the ratio of the light source light that can be used for image display is increasing. Therefore, the brightness of the image can be ensured. Further, since the light beam can be incident on the light modulation means such as a liquid crystal light valve at an angle close to the vertical, all the light beams can be modulated by the light modulation means. Therefore, the contrast ratio of the image can be improved.

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-described embodiment, the lighting device of the present invention has been described as being adapted to the lighting device of a three-plate projection display device, but is adapted to the lighting device of this three-plate projection display device. The present invention is not limited to this, and can be applied to illumination devices for various other projection display devices, such as a lighting device for a single-plate projection display device.

It is side surface sectional drawing of the illuminating device which concerns on 1st Embodiment by this invention. It is the schematic of the model used for the illumination efficiency simulation of an illuminating device. It is side surface sectional drawing of the illuminating device which concerns on 2nd Embodiment by this invention. It is explanatory drawing of the projector provided with the illuminating device which concerns on this invention. It is side surface sectional drawing of the illuminating device which concerns on a prior art.

Explanation of symbols

1, 2, 512, 513, 514... Illumination device 10, 50... Light source, 20... Collimator lens, 21. Reflector, 32 ... first focus, 33 ... second focus, 51 ... package, 53 ... virtual image, 500 ... projector (projection display), 522, 523, 524 ... Liquid crystal light valve (light modulation means), 526... Projection lens (projection means)

Claims (3)

A light source, a collimator lens disposed on one light exit surface side of the light source, and an elliptical reflector disposed on the other light exit surface side of the light source,
The collimator lens is disposed at a position where the front focal position of the collimator lens and the position of the virtual image formed by the lens effect of the light emitting part in the light source or the package in the light source are substantially the same,
In the elliptical reflector, the first focal position of the elliptical reflector and the position of the light emitting unit or the virtual image are substantially the same, and the second focal position of the elliptical reflector and the front principal point position of the collimator lens are substantially the same. A lighting device characterized by being arranged at a position.   The illumination device according to claim 1, wherein a diameter of the elliptical reflector at the first focal point is approximately 1 to approximately 1.5 times a maximum outer diameter of the light source. A projection display device comprising: an illumination device; a light modulation unit that modulates light from the illumination device; and a projection unit that projects light modulated by the light modulation unit.
The projection display device, wherein the illumination device is the illumination device according to claim 1.

Images