The present invention relates to a projection display apparatus and an illumination optical system mounted on the projection display apparatus.
In recent years, as a light source for the projection display apparatus, attention has been focused on a solid-state light source such as a LED (light-emitting device) or a semiconductor laser. The projection display apparatus equipped with the solid-state light source includes an illumination optical system that includes a solid-state light source and an optical element configured to guide light emitted from the solid-state light source, an image forming element configured to modulate the light guided by the illumination optical system, and a projection optical system configured to project the light modulated by the image forming element.
The light emission efficiency of the solid-state light source has been improved year by year. For example, even a LED having light emission efficiency exceeding 150[lm/W] is known. However, for a light source of the projection display apparatus required to project a high-luminance image, not only the light emission efficiency but also a light emission amount are important factors.
In this regard, even when one LED module each is prepared for each of the respective colors R, Q, and B, the sum of the amount of light emitted by these three LED modules cannot reach the amount of light emitted by a conventional discharge lamp. A LED module (may be referred to as “high power LED”) having power consumption exceeding several tens W is also known. However, even when one high power LED module each is prepared for each of the respective colors R, G, and B, the sum of the amount of light emitted by these three high power LED modules cannot reach the amount of light emitted by the conventional discharge lamp.
Thus, by preparing a plurality of LED modules for each of the R, G, and B colors, the sum of light emission efficiencies may be increased.
Patent Literature 1: JP2006-106683A
Patent Literature 2: JP2006-106682A
However, when a plurality of LED modules is prepared for each of the R, G, and B colors, the following problems occur.
As shown in
Accordingly, as shown in
Thus, an optical system must be disposed between each LED module and the image forming element, causing an increase of the number of components or enlargement of the illumination optical system.
Further, even when the optical system is disposed between each LED module and the image forming element, light emitted from the plurality of discretely arranged light sources obliquely enters the image forming element. Consequently, light use efficiency is reduced.
A single secondary light source may be formed by a light guide whose size is sufficient to cover an area including the light emission surfaces of two LED chips 101 arranged as shown in
The metal substrate constituting the LED module also functions as a heat sink for releasing heat generated from the LED chip. This requires a sufficient surface area in the metal substrate. Especially in the metal substrate constituting the high power LED of a large heat generation amount, a larger surface area is required. As a result, the metal substrate constituting a high power LED is larger than that constituting a normal LED module. Thus, when two high power LEDs are arrayed, distance T is increased, causing the aforementioned problem to be conspicuous.
Lights emitted from a plurality of light sources discretely arranged for one image forming element are guided to a common light guide to form a single secondary light source. Further, total reflection having no light loss is used as optical path conversion carried out to guide the lights emitted from the plurality of light sources to the common light guide.
The lights emitted from the plurality of light sources can be guided to the image forming element by one optical system. Further, lights emitted from a plurality of light sources can be entered straight into the image forming element.
A projection display apparatus according to the first exemplary embodiment of the present invention will be described.
Needless to say, the projection display apparatus according to this exemplary embodiment includes, in addition to the components shown in
Next, the illumination optical system that is a feature of the projection display apparatus according to this exemplary embodiment will be described in detail. It should be noted that three illumination optical systems 2R, 2G, and 2B shown in
As shown in
First LED module 11 and second LED module 12 are high power LEDs similar in structure to the LED module shown in
The light emission surface of first LED module 11 (LED chip 14) faces light incident surface 21a of first light guide 21 via a very small gap. On the other hand, the light emission surface of second LED module 12 (LED chip 14) faces light incident surface 22a of second light guide 22 via a very small gap. To reduce light loss, it is desirable for the gap between the light emission surface of the LED chip and the light incidence surface of the light guide to be as narrow as possible. However, to generate refraction during incidence on the light guide, the gap must be larger than the light wavelength.
First optical path conversion unit 31 is bonded to light exit surface 21b of first light guide 21. On the other hand, second optical path conversion unit 32 is bonded to light exit surface 22b of second light guide 22.
Specifically, first optical path conversion unit 31 is a right angle prism that includes two surfaces (first surface 31a and second surface 31b) orthogonal to each other and a slope (third surface 31c) over first surface 31a and second surface 31b. First surface 31a is bonded to light exit surface 21b of first light guide 21 by an optical adhesive.
Second optical path conversion unit 32 is a right angle prism that includes two surfaces (first surface 32a and second surface 32b) orthogonal to each other and a slope (third surface 32c) over first surface 32a and second surface 32b. First surface 32a is bonded to light exit surface 22b of second light guide 22 by an optical adhesive.
Further, second surface 31b of first optical path conversion unit 31 and second surface 32b of second optical path conversion unit 32 are bonded to light incident surface 50a of third light guide 50 by an optical adhesive.
In other words, first light guide 21, second light guide 22, first optical path conversion unit 31, second optical path conversion unit 32, and third light guide 50 are integrated.
Next, reflection unit 40 will be described.
Next, the operation of first illumination optical system 2R will be described referring to
The light output from light exit surface 21b of first light guide 21 enters first optical path conversion unit 31 bonded to light exit surface 21b. Specifically, the light output from light exit surface 21b enters first optical path conversion unit 31 from first surface 31a of first optical path conversion unit 31, and then enters third surface 31c of first optical path conversion unit 31.
Air layer 61 is present between third surface 31c of first optical path conversion unit 31 and reflection surface 41a of reflection unit 40. In other words, third surface 31c of first optical path conversion unit 31 is a boundary surface between two media different from each other in refractive index. Accordingly, light that has entered third surface 31c at an angle equal to or larger than a critical angle is totally reflected on third surface 31c.
The light totally reflected on third surface 31c of first optical path conversion unit 31 exits from second surface 31b of first optical path conversion unit 31 to enter third light guide 50.
On the other hand, light that has entered third surface 31c at an angle smaller than the critical angle is transmitted through third surface 31c. The light transmitted through third surface 31c is reflected on reflection surface 41a of reflection unit 40 to reenter first optical path conversion unit 31. As in the case of the light totally reflected on third surface 31c, the light that has reentered first optical path conversion unit 31 exits from second surface 31b to enter third light guide 50.
That is, all the lights guided by first light guide 21 to enter first optical path conversion unit 31 are finally guided to third light guide 50. The light entered into third light guide 50 is repeatedly reflected totally to travel through third light guide 50, and then exits from the light exit surface. In other words, the light entered into third light guide 50 is guided in a third direction (the direction of arrow “c” shown in
On the other hand, the light emitted from second LED module 12 enters second light guide 22 from light incident surface 22a. The light entered into second light guide 22 is repeatedly reflected totally to travel through second light guide 22, and then exits from light exit surface 22b. In other words, the light emitted from second LED module 12 is guided in a second direction (the direction of arrow “b” shown in
The light output from light exit surface 22b of second light guide 22 enters second optical path conversion unit 32 bonded to light exit surface 22b. Then, by the same principle as that of the aforementioned case, all the lights that are guided by second light guide 22 to enter second optical path conversion unit 32 are finally guided to third light guide 50. The light entered into third light guide 50 is repeatedly reflected totally to travel through third light guide 50, and then exits from the light exit surface. In other words, the light entered into third light guide 50 is guided in the third direction (the direction of arrow “c” shown in
In short, the lights emitted from the two solid-state light guides are guided to the common light guide to form a single secondary light source.
First light guide 21 and second light guide 22 according to this exemplary embodiment are square columnar. However, they can be square tubular. As materials for first light guide 21 and second light guide 22, optical glasses such as BK7 or optical resins can be used. Similarly, as materials for first optical path conversion unit 31, second optical path conversion unit 32, and base member 41 of reflection unit 40, optical glasses such as BK7 or optical resins can be used. Desirably, however, for optical path conversion units 31 and 32, materials higher in refractive index than those for light guides 21, 22, and 50 are used. Desirably, materials equal in refractive index are used for three light guides 21, 22, and 50.
As described at the outset, three illumination optical systems 2R, 2G, and 2B shown in
As the metal film constituting reflection surfaces 41a and 41b of reflection unit 40, an aluminum film, a gold film, or a silver film having high reflection efficiency is desirable. Needless to say, a dielectric multilayer film can be used.
As shown in
In this exemplary embodiment, first optical path conversion unit 31 and second optical path conversion unit 32 are integrated via third light guide 50. However, first optical path conversion unit 31 and second optical path conversion unit 32 can be integrally formed, and integrally formed first optical path conversion unit 31 and second optical path conversion unit 32 can be bonded to third light guide 50.
At least one of three illumination optical systems 2R, 2G, and 2B shown in
Hereinafter, the illumination optical system shown in
However, illumination optical system 2 shown in
In other words, in illumination optical system 2R shown in
In illumination optical system 2 shown in
On the other hand, the light emitted from second LED module 12 is guided in a second direction (the direction of arrow “b” shown in
In other words, in illumination optical system 2 shown in
However, as in the aforementioned case, in illumination optical system 2 shown in
The solid-state light sources according to the present invention include a semiconductor laser and an organic EL (electroluminescence). The image forming elements according to the present invention include a DMD (digital micromirror device).
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP2010/059067 | 5/28/2010 | WO | 00 | 10/4/2012 |
Publishing Document | Publishing Date | Country | Kind |
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WO2011/148499 | 12/1/2011 | WO | A |
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Number | Date | Country | |
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20130033685 A1 | Feb 2013 | US |