JP2005085768A - Lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an illumination device capable of dynamically adjusting the etendue of focused light emitted from a light source.
SOLUTION: A light source 41, a concave mirror 42 that reflects light from the light source, and an aperture 46 that is provided on the path of the beam reflected from the concave mirror and transmits a part of the beam 43 reflected by the concave mirror. And a retro-reflecting mirror 45 that reflects the remaining beam 44 reflected by the concave mirror. By changing the size of the aperture, the etendue can be adjusted dynamically and the luminous flux density can be increased. When the solid angle σ is increased, the life of the light source can be prevented from being shortened by reducing the light reflected in the light source direction. When the solid angle is reduced, a smaller etendue is required. For example, the solid angle can be used in a projection optical system illumination device that implements a color image using a color wheel. By using an optical integrator, it is possible to illuminate uniform light with a small etendue, lowering the manufacturing cost and reducing the number of assembly steps.
[Selection] Figure 4

Description

  The present invention relates to an illuminating device that illuminates light generated by a light source in one direction, and more particularly, to an illuminating device having a structure capable of dynamically adjusting etendue of light emitted from a light source.

  In general, the illumination device is widely used as a light source such as an image projection device that implements an image by using an image forming element such as a liquid crystal display element or a digital micromirror element that does not have a voluntary light emission capability.

  In order to achieve the maximum light efficiency in the image projection apparatus, the etendue of the light source is required to be equal to or smaller than the limit etendue of the image forming element. Otherwise, the etendue of the light source and the image forming element does not match each other, thereby causing light loss. Here, etendue indicates the geometric properties of the optical element related to the beam divergence and the cross-sectional size. The smaller the value, the higher the luminous flux density and the higher the brightness.

  A general lighting device includes a light source that generates light and a reflecting mirror that reflects light emitted from the light source in one direction, and has a predetermined etendue value. This Etendue value can be easily understood by multiplying the beam cross-sectional size at the target, which is the focal point of the beam, and the solid angle of the beam. For example, when an elliptical mirror having first and second focal points is adopted as a reflecting mirror and a light source is arranged at the first focal position, the beam cross-sectional size and the solid angle at the second focal position are measured, and this measurement is performed. The Etendue value can be obtained by multiplying the measured beam cross-sectional size and the solid angle.

  As a method for reducing the etendue value, there has been disclosed a lighting device having a structure as shown in FIGS. 1 to 3.

Referring to FIG. 1, an illumination device according to an example of the related art includes an elliptical mirror 11 having first and second focal points f ₁ and f ₂ , and a light source 12 positioned at the first focal point f ₁ of the elliptical mirror 11. And a retroreflecting mirror 15 disposed so as to face the elliptical mirror 11 with the light source 12 interposed therebetween. Here, the retroreflector 15 has a spherical shape, and an aperture 15a through which an incident beam is transmitted is formed at the center thereof.

Here, approximately half of the beams 14 emitted from the light source 12 (shown by solid lines) are directly incident on the elliptical mirror 11, and the remaining part of the beams 16 (shown by dotted lines) are reversed. The light enters the reflecting mirror 15. Directly incident beam into an elliptical mirror 11 is reflected from the reflecting surface 11a, it is tied to the second focus f ₂ through the aperture 15a. On the other hand, the beam incident on the retroreflecting mirror 15 is reflected back (returned and reflected) toward the light source 12, and passes through the light source 12 toward the elliptical mirror 11. The reflected-back beam 16 is connected to the second focus f ₂ through the aperture 15a after being reflected from the elliptical mirror 11.

  When the illumination device is configured in this way, the convergence angle θ by the elliptical mirror 11 is approximately 90 °, and the convergence is smaller by approximately 30 ° than the convergence angle 120 ° of the illumination device having the structure without the retroreflector 15. Has horns. Therefore, since the solid angle σ can be further reduced, the etendue can be reduced.

  However, when the lighting device is configured in this way, firstly, since a retroreflector must be provided, the manufacturing cost is increased, and secondly, there are many assembly process steps for accurate arrangement of the retroreflector. Third, since the aperture size is fixed, it is difficult to dynamically adjust the etendue. Fourth, almost half of the light illuminated from the light source is incident on the light source again. There is a problem that affects the life of the light source.

  Referring to FIG. 2, an illumination apparatus according to another conventional example includes a parabolic mirror 21 having a single focal point, a light source 22 positioned at the focal point of the parabolic mirror 21, and the parabolic mirror 21 with the light source 22 interposed therebetween. And a retroreflector 25 arranged so as to face a part of the mirror. Here, as shown in the figure, the retroreflecting mirror 25 is formed only on one side with the optical axis as the center, and the parabolic mirror 21 is set so that its focusing angle θ has a value of 120 °.

  Of the beam emitted from the light source 22, the beam incident within the range of the focusing angle θ of the parabolic mirror 11 is reflected from the parabolic mirror 21. Nearly half of the reflected beam 24 (indicated by the solid line) is directly incident on the target 23 while maintaining parallelism.

  On the other hand, the remaining beam 24 (indicated by a dotted line) is incident on the retroreflector 25. The beam incident on the retroreflecting mirror 25 is reflected back to the parabolic mirror 21, and the reflected beam passes through the light source 22 toward the other reflecting surface of the parabolic mirror 21. Then, it goes to the target 23 along the same path as the beam shown by the solid line.

  When the illumination device is configured in this way, the cross section of the incident beam at the target 23 can be reduced, so that the etendue can be reduced.

  However, when the illumination device is configured in this way, first, since the size of the retroreflector is fixed, it is difficult to dynamically adjust the etendue, and secondly, the illumination device is illuminated from the light source. Since almost half of the light is incident on the light source again, there is a problem that affects the life of the light source.

  Referring to FIG. 3, a conventional illumination device according to still another example includes a parabolic mirror 31 having a single focal point, a light source 32 positioned at the focal point of the parabolic mirror 31, and the parabolic mirror sandwiching the light source 32. 31 and a retroreflecting mirror 35 disposed so as to face a predetermined outer peripheral region. Here, the retroreflector 35 has an aperture 35a through which an incident beam passes in the center. The parabolic mirror 31 is set so that its focusing angle θ has a value of 120 °.

  Of the beam emitted from the light source 32, the beam incident within the range of the converging angle θ of the parabolic mirror 31 is reflected from the parabolic mirror 31. A part of the reflected beam 34 (shown by a solid line) is directed to the aperture 35a, passes through the aperture 35a, and is directly incident on the target 33.

  On the other hand, the remaining beam 36 (indicated by a dotted line) is incident on the retroreflector 35. The beam incident on the retroreflecting mirror 35 is reflected back to the parabolic mirror 31, and the reflected beam passes through the light source 32 toward the other reflecting surface of the parabolic mirror 31. Then, it goes to the target 33 along the same path as the beam shown by the solid line.

  When the illumination device is configured in this way, the cross section of the incident beam at the target 33 can be reduced, and the etendue can be reduced.

  However, when the illumination device is configured in this way, first, it is difficult to dynamically adjust the etendue because the size of the aperture is fixed, and secondly, the light illuminated from the light source is difficult. Since almost half of the light is incident again on the light source, there is a problem that affects the life of the light source.

  The present invention has been devised in view of the above-described problems, and can reduce the manufacturing cost, simplify the assembly process, minimize the influence on the light source, and reduce the size of the aperture. The object is to provide a lighting device that can be varied to dynamically adjust etendue.

  In order to achieve the above object, an illumination apparatus according to the present invention includes a light source that generates and illuminates light, a concave mirror that reflects incident light so that a beam illuminated from the light source is directed in one direction, An aperture that is provided on the path of the beam reflected from the concave mirror and transmits a part of the beam reflected from the concave mirror, and a reflection that reflects back (reflects back) the remaining beam reflected from the concave mirror. And a retroreflector having a surface.

  The aperture of the retroreflector is variable in size, further includes a variable unit that varies the aperture, and is reflected back from the reflecting surface by varying the size of the aperture of the retroreflector. The beam can be adjusted dynamically.

  The present invention further includes an optical integrator provided on the path of the beam reflected from the concave mirror and mixing and emitting the incident beam.

  The lighting apparatus according to the present invention uses a retroreflector having a structure that can change the size of the aperture, thereby dynamically adjusting the etendue by changing the size of the aperture by the apparatus employing the lighting apparatus of the present invention. it can. Therefore, the light flux density of the focused light can be increased.

  Here, when the solid angle σ is set to be large, the light reflected back in the light source direction can be reduced and the load of the light source can be reduced, so that it is possible to substantially prevent the life from being shortened.

  On the other hand, when the solid angle is reduced, the etendue can be reduced, so that it can be used in a projection optical system that requires a smaller etendue, for example, a projection optical system illumination device that implements a color image using a color wheel.

  In addition, by configuring the optical integrator together with the illumination device, uniform light with reduced etendue can be illuminated. And since a structure is compactized, a manufacturing cost can be lowered | hung and an assembly process man-hour can be simplified.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  Referring to FIG. 4, an illuminating device according to an embodiment of the present invention includes a light source 41 that generates and irradiates light, a concave mirror 42 that directs a beam emitted from the light source 41 in one direction, and the light source 41. And a retroreflecting mirror 45 disposed so as to face the concave mirror 42. The retro-reflecting mirror 45 is provided on the path of the beam reflected from the concave mirror 42, an aperture 46 for transmitting a part of the beam reflected from the concave mirror 42, and the rest reflected from the concave mirror 42. And a reflecting surface 47 for reflecting back (reflecting) the beam. The reflection surface 47 is preferably a flat surface disposed so that the surface is perpendicular to the incident optical axis. The aperture 46 is provided at the center of the reflecting surface 47 and is formed in a square shape or a circular shape.

  In addition, it is desirable that the illumination device according to the present embodiment further includes a variable unit 50 that makes the aperture 46 variable and makes it variable. In this case, the beam reflected back from the reflecting surface 47 can be dynamically adjusted by varying the size of the aperture 46 via the variable unit 50. The variable unit 50 is made up of a drive source 51 and a control unit 55 by varying the size of the aperture 46 according to the type of optical system in which the illumination apparatus of the present invention is employed, for example, a projection projection optical apparatus. The Since the mechanical configuration of the variable unit 50 is general, detailed description thereof is omitted.

The concave mirror 42 is preferably an elliptical mirror having first and second focal points f ₁ and f ₂ . In this case, the light source 41 is located substantially at the first focal point f ₁ , and the beam illuminated from the light source 41 and reflected from the concave mirror 42 is focused around the second focal point f ₂ . Furthermore, the retroreflector 45 is disposed in the second focus f ₂ position.

  An example of the light source 41 is an arc lamp that generates light by arc discharge. In this case, the arc lamp is classified into a metal-halide lamp, a xenon lamp, and the like depending on a substance that contributes to the discharge, and any of them may be adopted.

It is desirable that the arc gap Ga of the arc lamp satisfies the condition of Formula 1 in consideration of the brightness of the illuminated beam.
[Formula 1]
0.7 ≦ Ga ≦ 3 [mm]

  The operation of the illumination apparatus according to the embodiment of the present invention configured as described above will be described as follows.

Most of the beam emitted from the light source 41 located substantially at the first focal point f ₁ is directly incident on the concave mirror 42 and reflected from the reflecting surface in the direction of the second focal point f ₂ . Here, if the generation of the beam from the light source 41 is described, it can be seen that it does not start from the point light source but occurs from the arc gap Ga. Accordingly, in the case of forming the concave mirror 42 with elliptical mirror is also reflected beam rather than toward the second focal point f ₂ all, it can be seen that the widely distributed in the second focus f ₂ around As shown .

  That is, some of the reflected beams 43 (shown by solid lines) are directly incident on the aperture 46. On the other hand, the remaining beam 44 (indicated by a dotted line) is incident on the reflecting surface 47 and reflected back from the reflecting surface 47 toward the concave mirror 42. The reflected beam is re-reflected by the concave mirror 42 and travels in the direction of the retro-reflecting mirror 45 through another path. A part of this beam passes through the aperture 46 and the rest is reflected back from the reflecting surface 47. While repeating such a reflection process, almost all of the beam illuminated from the light source 41 and reflected by the concave mirror 42 passes through the aperture 46.

  Since the aperture 46 is varied by the variable unit 50, the size of the aperture 46 can be dynamically controlled. Accordingly, the solid angle σ of the beam passing through the aperture 46 can be adjusted. Here, when the solid angle σ is large, the number of reflected beams decreases, so that the light traveling toward the light source 41 can be reduced.

  Thereby, since the load of the light source 41 can be reduced, it is possible to prevent a part of the life from being shortened. On the other hand, when the solid angle σ is reduced, the etendue can be reduced, so that it can be used in a projection optical system that requires a smaller etendue, such as a projection optical system illumination device that implements a color image using a color wheel.

  FIG. 5 is a graph showing a relative light flux change due to the aperture size change of the retroreflector of FIG. Here, the value indicated by A indicates the change in luminous flux due to the aperture size change when the aperture and the reflecting surface are provided, and the value indicated by B has a surface capable of absorbing the incident beam instead of the reflecting surface. Fig. 5 shows a change in luminous flux due to a change in aperture size.

  Referring to this graph, it can be seen that when the reflecting surface 47 is provided as in the embodiment of the present invention, the relative light flux change is small even when the aperture is small. On the other hand, in the case of having an absorption surface (not shown) as in the comparative example, it can be seen that when the aperture is large, the difference does not occur greatly, but when the aperture is small, the relative luminous flux greatly decreases.

  Referring to FIG. 6, an illuminating device according to another embodiment of the present invention includes a light source 61 that generates and irradiates light, a concave mirror 62 that directs a beam emitted from the light source 61 in one direction, and the light source 61. It includes a retroreflecting mirror 65 disposed so as to face the concave mirror 62 and an optical integrator 70. Further, a variable unit 80 for changing the aperture 66 of the retroreflector 65 is included.

  The illumination device according to the present embodiment is characterized in that it further includes an optical integrator 70 when compared with the illumination device according to one embodiment. On the other hand, in the present embodiment, the remaining components, that is, the light source 61, the concave mirror 62, the retroreflecting mirror 65, and the variable unit 80 are as described with reference to FIG.

  The optical integrator 70 is provided on the path of the beam reflected from the concave mirror 62, and mixes the incident beam into a uniform beam. The optical integrator 70 includes an incident end portion 70a on which the beam reflected from the concave mirror 62 is incident, a reflecting portion 70b that guides the progress of light incident through the incident end portion 70a through reflection, And an emission end portion 70c from which a mixed beam is reflected while being reflected from the reflection portion 70b.

  The optical integrator 70 according to one embodiment is composed of a rectangular parallelepiped shaped rod 71 having a structure as shown in FIG. The rod 71 is made of glass or plastic material and has a higher refractive index than the periphery. Accordingly, the beam incident through the incident end 70a travels in the direction of the exit end 70c while being totally reflected by the reflecting portion 70b due to the difference between the incident beam incident angle and the refractive index. As a result, the non-uniform beam incident from the light source 61 side is totally reflected while being mixed equally and becomes a uniform beam.

  As shown in FIG. 8, the optical integrator 70 according to another embodiment includes a lens barrel 75 that covers an internal space in which an incident beam travels, and a reflecting surface 70 b formed on the inner wall of the lens barrel 75. . Accordingly, the beam incident through the incident end portion 70a is reflected from the reflecting portion and is made uniform while proceeding inside.

  The retroreflector 65 is disposed so as to face the exit end portion 70c and regulates the exit beam. That is, the size of the aperture 66 is formed smaller than the size of the emission end portion 70c. Accordingly, a part of the beam emitted from the emission end portion 70 c is reflected back from the reflection surface 67, and the reflected beam passes through the inside of the optical integrator 70 again toward the concave mirror 62. . Thereafter, the light is reflected again by the concave mirror 62 and travels in the direction of the retroreflecting mirror 62 along another path. A part of the beam passes through the aperture 66 and the rest is reflected back from the reflecting surface 67. While repeating such a reflection process, almost all of the beam illuminated from the light source 61 and reflected from the concave mirror 62 passes through the aperture 66.

  By configuring as described above, the beam illuminated from the light source 61 can be made uniform, and the solid angle of the beam transmitted through the aperture 66 can be adjusted by dynamically controlling the size of the aperture 66.

  Referring to FIG. 9, an illumination apparatus according to another embodiment of the present invention includes a light source 161 that generates and emits light, a concave mirror 162 that directs a beam emitted from the light source 161 in one direction, and the light source 161. A retroreflector 165 having an aperture 166 and a reflecting surface 167, and an optical integrator 170, disposed so as to face the concave mirror 162. Further, a variable unit 180 for changing the aperture 166 of the retroreflector 165 is included.

  The illumination device according to this embodiment is characterized in that the arrangement of the light integrator 170 is changed when compared with the illumination devices according to the other embodiments described above.

  On the other hand, the configuration and function of the light source 161, the concave mirror 162, the retroreflecting mirror 165, the variable unit 180, and the optical integrator 170 themselves are the same as those described with reference to FIGS. Omitted.

  The light integrator 170 is provided on the path of the light transmitted through the aperture 166 of the retroreflecting mirror 165, and mixes the incident beams into a uniform beam. In this case, the beam deviating from the incident end of the optical integrator 170 is reflected by the reflecting surface 167 and reflected back toward the concave mirror 162.

  The above-described embodiments are merely illustrative, and various modifications and equivalent other embodiments can be made by those skilled in the art. Therefore, the true technical protection scope of the present invention is determined by the technical idea of the invention described in the claims.

  The illuminating device according to the present invention can be applied to an image projecting device that implements an image by using an image forming element such as a liquid crystal display element or a digital micromirror element that does not have a light emission capability.

It is the schematic sectional drawing which showed the illuminating device using the conventional elliptical mirror. It is the schematic sectional drawing which showed an example of the illuminating device using the conventional parabolic mirror. It is the schematic sectional drawing which showed the other example of the illuminating device using the conventional parabolic mirror. 1 is a schematic cross-sectional view illustrating a lighting device according to an embodiment of the present invention. It is the graph which showed the relative light beam change by the size change of the aperture of the retroreflector of FIG. FIG. 6 is a schematic cross-sectional view illustrating a lighting device according to another embodiment of the present invention. FIG. 7 is a schematic perspective view illustrating an optical integrator and a retroreflector according to the example illustrated in FIG. 6. FIG. 7 is a schematic cross-sectional view showing another example of the optical integrator in FIG. 6. FIG. 6 is a schematic cross-sectional view illustrating a lighting device according to another embodiment of the present invention.

Explanation of symbols

41 Light source 42 Concave mirror 43 Partial light 44 Remaining light 45 Retroreflector 46 Aperture 47 Reflecting surface 50 Variable unit 51 Driver 55 Controller f ₁ First focus f ₂ Second focus Ga Arc gap σ Solid angle

Claims (11)

A light source that generates and illuminates light;
A concave mirror that reflects the incident light so that the beam illuminated from the light source is directed in one direction;
An aperture that is provided on the focal point of the beam reflected from the concave mirror and transmits a part of the beam reflected from the concave mirror; and a reflection surface that reflects back the remaining beam reflected from the concave mirror. And a retroreflective mirror. The concave mirror is an elliptical mirror having first and second focal points;
The light source is located substantially at the first focus;
The illumination device according to claim 1, wherein the retroreflecting mirror is disposed at the second focal position. The aperture of the retroreflector is variable in size,
2. A variable unit for varying the aperture, wherein the beam reflected from the reflecting surface can be dynamically adjusted by varying the size of the aperture of the retroreflector. The lighting device described in 1. The reflecting surface is a plane arranged perpendicular to the incident optical axis;
The illumination device according to claim 1, wherein the aperture is provided at a central portion of the reflecting surface and is formed in a quadrangular shape or a circular shape. The light source is
The lighting device according to claim 1, wherein the lighting device is an arc lamp that generates light by arc discharge. The lighting device according to claim 5, wherein the arc gap Ga of the arc lamp satisfies the following conditional expression:
<Conditional expression>
0.7 ≦ Ga ≦ 3 [mm].   The illumination device according to claim 1, further comprising an optical integrator provided on a path of the beam reflected from the concave mirror and mixing and emitting the incident beam.   The illumination device according to claim 7, wherein the retroreflecting mirror is provided at an emission end of the optical integrator, and a part of a beam incident through the optical integrator is reflected back.   8. The illumination according to claim 7, wherein the retroreflecting mirror is provided at an incident end of the optical integrator, and a beam deviating from the incident end of the optical integrator is reflected back toward the concave reflecting mirror. apparatus. The optical integrator is
Including a hexahedron shaped rod made of glass or plastic material,
The illumination apparatus according to claim 7, wherein the incident beam is totally reflected by a difference in refractive index from the periphery. The optical integrator is
A lens barrel that covers the internal space through which the incident beam travels, and a reflecting portion that is formed on the inner wall of the lens barrel,
The illumination apparatus according to claim 7, wherein the incident beam is formed into a uniform beam while proceeding inside while being reflected from the reflection unit.

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