JP2009259564A - Light source unit and projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology which can efficiently condense light from a light source unit used in a projection apparatus such as a projector. <P>SOLUTION: When a rotating ellipse mirror is formed as a reflection mirror 40 in a projector 100, the longer axis L1 of an ellipse E2 slopes down to the left with respect to an axis of rotation (optical axis L). Then, the second focal point F2 of the ellipse E2 is set at a position of a DMD 70 on the optical axis L. Furthermore, the first focal point F1 of the ellipse E2 is set at a virtual image position A2 of a discharge lamp 10. Therefore, light W1, W2 emitted from a light emitting position A1 which shows the first focal point F1 as the virtual image position A2 is reflected so as to be focused at the second focal point F2 of the ellipse E2 on a reflection surface of the reflection mirror 40. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a light source unit and a projector, and more particularly to a light source unit including a discharge lamp and a reflecting mirror and a projector including such a light source unit.

  The light source unit provided in the projector employs a discharge lamp such as a high-pressure mercury lamp as a light source, and has a reflecting mirror for reflecting and emitting light emitted from the light source in a predetermined direction. .

  Brightness is one of the important performance indicators of projectors, and how to increase the amount of light projected from the projector is a major issue. Various technologies have been proposed to improve the brightness. Yes. For example, there is an increase in the amount of light of the discharge lamp, and various technologies have been introduced by lamp manufacturers. In another aspect, the amount of light finally obtained can be increased by efficiently using the light emitted from the discharge lamp. In other words, by appropriately setting the direction of the light emitted from the discharge lamp, emission in a useless direction is prevented. At this time, the shape of the reflecting mirror becomes very important.

  The shape of the reflector is roughly divided into an elliptical shape and a parabolic shape. Each of the reflecting surfaces of the reflecting mirror is formed by rotating an elliptic curve or a part of a parabola around the optical axis. In recent years, a DMD (digital mirror device) has been adopted as an optical modulation element of a projector, and an elliptical reflecting mirror is mainly used in a light source unit of a projector employing the DMD. Hereinafter, a reflecting mirror having a reflecting surface formed by rotating an elliptic curve around the optical axis is also referred to as a rotating ellipsoidal mirror.

Various shapes have been proposed as elliptical shapes.For example, in order to improve the quality in a relatively wide irradiation area, one focal point of the elliptic curve is set to coincide with the light source, and the other focal point is the optical axis. There is a technique of forming a reflecting surface by rotating the elliptic curve around the optical axis so as to be away from the optical axis (see, for example, Patent Document 1).
JP-A-5-5952

  In the technique disclosed in Patent Document 1, the illuminance ratio is improved by efficiently irradiating light from a light source to achieve high brightness and high quality. However, for example, from the viewpoint of condensing light on a light modulation element such as DMD, the above technique cannot be applied, and another technique has been demanded. Further, the discharge lamp is formed with a glass sealing body in order to keep the inside of the lamp at a high pressure, and discharge is performed inside the glass envelope. Then, the lens effect (refraction) occurs due to the shape and thickness of the glass envelope, and the apparent light emission position (virtual image position) is shifted from the actual light emission position. As a result, there is a problem that the condensing area is enlarged at the position where the DMD or the like that collects the light emitted from the reflecting mirror is installed, and the condensing efficiency is lowered.

  In view of the above problems, an object of the present invention is to provide a technique capable of efficiently condensing light from a light source unit used in a projection apparatus such as a projector.

The apparatus according to the present invention relates to a light source unit. This light source unit is a light source unit including a discharge lamp and a reflecting mirror that condenses light emitted from the discharge lamp at a predetermined position on an optical axis, and the reflecting surface of the reflecting mirror is the discharge lamp. The first inclination on the side where the lens is disposed is set to be shifted from the optical axis, and the elliptical curve in which the second focal point on the light collecting side is set on the optical axis is rotated around the optical axis. It is formed by an ellipse.
The first focus of the ellipse may be set at a virtual image position of the discharge lamp.
Another apparatus according to the present invention is a projector and includes the light source unit described above.

  ADVANTAGE OF THE INVENTION According to this invention, the technique which can condense efficiently the light of the light source unit utilized in projection apparatuses, such as a projector, can be provided.

  Next, the best mode for carrying out the present invention (hereinafter simply referred to as “embodiment”) will be specifically described with reference to the drawings.

  FIG. 1 is a diagram showing the structure of the projector 100 according to the present embodiment mainly focusing on the optical system. The projector 100 includes a light source unit 50, a color wheel 60, a DMD 70, and a light projecting optical system 80. The light emitted from the light source unit 50 passes through the color wheel 60 and is collected on the DMD 70 disposed on the optical axis L. Then, the light is modulated by the DMD 70 and projected from the light projecting optical system 80 onto an external screen or the like. A lens or the like for adjusting the length of the optical path may be disposed on the path from the light source unit 50 to the DMD 70. Here, the optical axis L is an axis connecting the light emission position of the discharge lamp 10 and the center of the condensing area in the DMD 70.

  The light source unit 50 includes the discharge lamp 10 and the reflecting mirror 40. The reflecting mirror 40 is a rotating ellipsoidal mirror, and the discharge lamp 10 is arranged so that the first focal point F1 of the elliptic curve constituting the reflecting surface is in the vicinity of the light emission position A1. Further, the DMD 70 is disposed so that the position of the DMD 70 is the second focal point F2 of the elliptic curve. Although details will be described later in this embodiment, the spheroid mirror constituting the reflecting mirror 40 has a second condensing position (DMD 70) when the part of the elliptic curve is rotated around the optical axis. The elliptic curve is inclined so as to shift to the focal point F2 and to shift the first focal point F1 on the one light source side from the optical axis L to the virtual image position A2 (for example, see FIG. 7). In FIG. 1, the distance between the light emission position A1 and the first focal point F1 (virtual image position A2) is very short and coincides with each other. However, as described later in FIG. The focal point F1 coincides with the virtual image position A2 that is shifted from the light emission position A1. Therefore, first, the characteristics (light distribution characteristic and lens effect) of the discharge lamp 10 and the reflection mirror of a general spheroid mirror will be briefly described as prerequisite technologies, and then the characteristic shape of the reflection mirror in this embodiment will be described. .

  FIG. 2 is a diagram schematically showing a light distribution of a general discharge lamp. Here, the right side of the figure shows the light distribution of the AC type discharge lamp, and the left side of the figure shows the light distribution of the DC type discharge lamp. In the AC type discharge lamp, since the discharge position changes vertically, the emitted light also shows a light distribution with a vertically symmetrical shape. On the other hand, in a direct current type discharge lamp, the discharge position is one of the upper and lower electrodes, so that the light distribution in the upper region becomes wider as shown in the figure, for example. The reflecting mirror needs to efficiently collect the light indicated by this light distribution in a desired direction, more specifically, on a light modulation element such as a DMD.

  FIG. 3 is a cross-sectional view schematically showing the structure of a general AC type discharge lamp 10. FIG. 4 is an enlarged view mainly showing the light emitting unit 20 of the discharge lamp 10. As shown in FIG. 3, the discharge lamp 10 includes a central light emitting unit 20 and side tube portions 12 extending from the light emitting unit 20 to the left and right sides in the drawing.

  The light emitting section 20 and the side tube section 12 are formed as a glass sealed body in which high pressure gas is sealed with, for example, quartz glass. The light emitting section 20 is formed with a high pressure sealed space 26 in which mercury and a rare gas of high pressure gas are sealed inside maintained at a high pressure. Further, arc electrodes 21 and 22 are arranged extending from the side tube section 12. ing. The side tube portion 12 is provided with lead electrodes 23 and 24, and molybdenum sheets 27 and 28 that electrically connect the lead electrodes 23 and 24 and the arc electrodes 21 and 22.

  Then, the light emitted from the light emission position A1 between the arc electrodes 21 and 22 reflects the mirror 40 as shown by a broken line in FIG. 3 when the thickness, refractive index, etc. of the glass sealing material of the light emitting unit 20 are not taken into consideration. Go straight on. On the other hand, the actual optical path in consideration of the thickness and refractive index of the glass sealing material of the light emitting unit 20 is refracted so that the light distribution direction is narrowed by the convex lens structure of the light emitting unit 20 as shown by the solid line. This action is also called a lens effect, and this lens effect may improve the light collection efficiency.

  By the way, as shown in FIG. 4, the light emitted from the light emission position A1 is refracted by the bulb inner surface 32 and the bulb outer surface 31 due to the lens effect described above, so the apparent light emission position (virtual image position A2) is as shown in the figure. Is shifted downward from the light emission position A1.

  FIG. 5 is a diagram illustrating a light path in a state where the virtual image position A2 does not occur (no lens effect), and FIG. 6 illustrates a light path in a state where the virtual image position A2 is shifted from the light emission position A1 due to the lens effect. Each of them is a spheroid reflecting mirror 140 that is conventionally used. For convenience, two optical paths (W1, W2) are shown. In the ellipse E1 for forming the reflecting surface of the reflecting mirror 140, the optical axis L, which is the rotation axis when rotating the curve of the ellipse E1, and the major axis L1 of the ellipse E1 coincide. Further, the light emission position A1 coincides with the first focal point F1 of the ellipse E1. As shown in FIG. 5, when there is no lens effect, the condensing point C of the two optical paths W1 and W2 coincides with the second focal point F2. However, as shown in FIG. 6, when a deviation amount D occurs due to the lens effect, the condensing point C of the two optical paths W1 and W2 does not coincide with the second focal point F2. That is, the light collection efficiency is reduced or the illuminance ratio is deteriorated.

  The distance (deviation amount D) between the light emission position A1 and the virtual image position A2 varies depending on the shape, thickness, and material of the light emitting section 20 (bulb outer surface 31 and bulb inner surface 32). The distance between the two arc electrodes 21 and 22 is about 1 mm, and the distance (deviation amount D) between the light emission position A1 and the virtual image position A2 may be about 0.5 mm.

  In recent years, in order to increase the luminance of the discharge lamp 10, the pressure in the high-pressure sealed space 26 may be increased. In this case, it is necessary to increase the sealing material thickness 25 (the distance between the bulb outer surface 31 and the bulb inner surface 32). In this case, since the amount of refraction becomes large, if the amount of deviation D is not taken into account, there is a possibility that the reduction of the light collection efficiency becomes remarkable and a desired light amount cannot be obtained.

  Therefore, in this embodiment, the shape of the reflecting mirror 40 is improved as described below. FIG. 7 is a diagram illustrating the shape of the reflecting mirror 40 according to the present embodiment. As shown in the figure, the curve of the ellipse E2 that forms the reflecting surface of the reflecting mirror 40 is slightly inclined.

  More specifically, the ellipse E2 when the spheroid mirror is formed as the reflecting mirror 40 has its long axis L1 slightly inclined with respect to the optical axis L connecting the light emission position A1 and the center of the DMD 70, and the left in the drawing. Set to Decrease. At this time, the second focal point F2 of the ellipse E2 is set at the position of the DMD 70 on the optical axis L. The first focal point F1 of the ellipse E2 is set at the virtual image position A2 of the discharge lamp 10. In such a geometrical arrangement, the reflecting surface of the reflecting mirror 40 is rotated by rotating some curves (points X to Y) of the ellipse E2 indicated by the bold line in the drawing with the optical axis L as the rotation axis. Formed (illustrated by thick solid and broken lines). The point X is an intersection of the ellipse E2 and the optical axis L, and the point Y is a position corresponding to the opening end of the reflecting mirror 40. By using the reflecting mirror 40 formed in this way, light (W1, W2) emitted from the light emitting position A1 indicating the first focal point F1 as the virtual image position A2 is elliptical E2 on the reflecting surface of the reflecting mirror 40. Converges to the second focal point F2.

  In this way, the reflecting mirror 40 is a rotating oblique elliptical mirror having a reflecting surface formed by tilting and rotating the elliptic curve, so that the light emission position A1 of the discharge lamp 10 changes the virtual image position A2 by the lens effect. Even if it has, since the condensing point C can be made to coincide with DMD70 (2nd focus F2), the condensing efficiency in DMD70 can be improved. Although details are not described, as a result of simulation, improvement in light collection efficiency of about 3 to 5% was confirmed. In the above embodiment, the first focal point F1 of the ellipse E2 is made coincident with the virtual image position A2 of the discharge lamp 10, but the present invention is not limited to this. For example, if the second focus F2 is between the light emission position A1 and the virtual image position A2, the light collection efficiency can be improved although it is slightly inferior to the case where they are completely matched.

  The present invention has been described based on the embodiments. This embodiment is an exemplification, and it is understood by those skilled in the art that various modifications can be made to each of those components and combinations thereof, and such modifications are also within the scope of the present invention.

It is a figure which mainly focuses on an optical system and shows the structure of the projector based on this embodiment. It is the figure which showed typically the light distribution of the general discharge lamp based on this embodiment. It is sectional drawing which shows typically the structure of the general alternating current type discharge lamp based on this embodiment. It is the figure which expanded and showed the light emission part of the general alternating current type discharge lamp based on this embodiment. It is the figure which showed the path | route of the light of the state which does not produce a lens effect in the discharge lamp based on this embodiment. It is the figure which showed the path | route of the light of the state which the lens effect produced in the discharge lamp based on this embodiment, and the virtual image position shifted | deviated from the light emission position. It is a figure explaining the shape of the reflective mirror formed with the spheroid mirror based on this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Discharge lamp 12 Side tube part 20 Light emission part 25 Sealing material thickness 26 High pressure enclosure space 31 Valve | bulb outer surface 32 Valve | bulb inner surface 40 Reflector 50 Light source unit 100 Projector F1 1st focus F2 2nd focus L Optical axis L1 Long axis A1 Light emission position A2 Virtual image position

Claims (3)

A light source unit comprising a discharge lamp and a reflecting mirror for condensing light emitted from the discharge lamp at a predetermined position on the optical axis,
The reflecting surface of the reflecting mirror is an elliptic curve in which the first focal point on the side where the discharge lamp is disposed is set to be shifted from the optical axis, and the second focal point on the light collecting side is set on the optical axis. A light source unit, characterized in that it is formed by a rotationally inclined ellipse that is rotated around the optical axis.   The light source unit according to claim 1, wherein the first focus of the ellipse is set at a virtual image position of the discharge lamp.   A projector comprising the light source unit according to claim 1.

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