JPH11120812A - Lighting system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent temperature rise in the vicinity of a light source, and realize high efficiency by reducing the opening number by containing a reflecting optical plane for controlling the spatial distribution on a virtual plane of a main beam of light from the virtual center of the light source and an optical plane to control the direction of the main beam of light from this, and specifying a minimum distance between an electrode contained in a tubular bulb and the reflecting optical plane. SOLUTION: A light flux from an arc in the vicinity of an electrode of a light source 1, such as a discharge lamp, is reflected by a distribution control plane 4a being a reflecting mirror to control the distribution of a main beam of light from the virtual center of the light source 1 in a virtual plane in the vicinity of a direction control plane 4b which is a refracting optical plane. The reflected light passes through the direction control plane 4b and is controlled in its direction, and the opening number of the light flux turns into a constant distribution. An auxiliary image forming device 3 reflects the light flux from the light source 1 and returns it to the light source 1. Influence of the return light on the vicinity of a tubular bulb and radiation heat by a reflecting surface is relieved by setting an interval D between the tubular bulb of the light source 1 and an optical element such as the distribution control plane 4a to (D>2d) (d is the diameter of the tubular bulb), and cloudiness due to crystallization of the tubular bulb can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting device having a small numerical aperture and high efficiency, and particularly to a lighting device utilizing a discharge lamp light source, which belongs to a technical field for extending the life of the light source. It is also suitable as a lighting device for a projector.

[0002]

2. Description of the Related Art The applicant of the present invention has disclosed, in Japanese Patent Application Laid-Open No. 8-532381, a basic structure of a projection type display device provided with an illumination device in which various light flux distribution and direction control elements are combined. Further, in Japanese Patent Application Laid-Open Nos. 8-357423 and 8-357424, a configuration of an auxiliary imaging device for improving utilization efficiency has been proposed. It has a small numerical aperture for a given light source size, and in order to realize a highly efficient illumination system, some light beams emitted from the light source are returned to the light source to reuse the light beam. It describes the effectiveness of the auxiliary imaging device. Such an auxiliary imaging device returns the light flux once emitted from the light source to the light source.
This causes a temperature rise near the light source.

Further, due to the temperature gradient generated inside the bulb of the discharge lamp due to the effect of gravity, the temperature at the upper part of the bulb becomes higher than at other parts. As described in Japanese Patent Application Laid-Open No. Hei 9-180501, the arc itself generated between the electrodes tends to be biased upward due to the effect of this temperature gradient, which also causes a rise in the temperature of the upper portion of the tube.

On the other hand, a parabolic mirror for converting a principal ray into parallel light and an elliptical mirror for re-imaging the light source are often used as an optical element which takes in a light beam from such a light source and guides the light beam to an illumination device. In particular, a parabolic mirror is a reflecting mirror having a large diameter and a deep shape in order to convert a light beam from a light source into parallel light without leakage. In order to reduce the diameter and the size, the focal length of the parabolic mirror must be reduced. In this case, the distance between the tube of the light source and the parabolic mirror is short, so that the tube is directly affected by the reflected light and radiant heat of the parabolic mirror.

Further, in the case of a discharge lamp, the ultraviolet rays generated from the light source have various adverse effects such as not only on the human body but also on the image element and the resin constituting the housing. It is necessary to cut such ultraviolet rays at an early stage of the illumination system. For example, when a flat glass is provided on the front of a parabolic mirror or the like and an ultraviolet reflective film is applied to the flat glass, the reflected ultraviolet rays are again emitted near the bulb. An image will be formed. This also contributes to the temperature rise near the bulb.

[0006]

Problems to be Solved by the Invention Japanese Patent Application Laid-Open No. 8-53238
1. having a relatively small numerical aperture as disclosed in
In order to realize a highly efficient lighting device, it is desirable that the light source be as small as possible. On the other hand, a rise in temperature near the light source causes crystallization of a quartz bulb for enclosing the electrodes and enclosing the gas, causing cloudiness. The white turbidity of the bulb causes scattering of the light flux, which is equivalent to an increase in the size of the light source, and lowers the efficiency. The causes of such a rise in the temperature of the tube are not only the concentration of energy near the electrodes, but also uneven temperature due to convection, unevenness of the arc,
Radiation heat of the reflector around the light source, the effect of the luminous flux returning to the vicinity of the tube, and the like can be cited. The crystallization of the tube proceeds by these comprehensive heat effects. Therefore, in order to maintain the point light source property and the long life of the light source, it is necessary to remove at least a factor that causes a rise in the temperature of the light source. An object of the present invention is to provide a means for preventing such a temperature rise near a light source, and to provide a highly efficient lighting device having a small numerical aperture.

[0007]

In order to achieve the above object, the present invention has the following features. The illuminating device of the present invention is a basic configuration for realizing a relatively small numerical aperture and a highly efficient illuminating device, which is a combination of an optical surface for controlling the distribution of a light beam and an optical surface for controlling the direction of the light beam. In addition, it is assumed that an auxiliary imaging device for returning a part of the light beam from the light source to the light source as needed, and an element for controlling the take-in angle of the light beam from the light source are added. Among the various combinations of such optical elements, the following condition D> 2d is satisfied with respect to the minimum distance D between the electrode and the reflective optical surface constituting the control element and the auxiliary imaging device and the diameter d of the tube. By using only the configuration described above, the influence of the radiant heat from the reflective optical surface directly on the tube is reduced.

Further, by applying a visible light reflecting film which transmits infrared light to the reflecting optical surface constituting the above-mentioned lighting device, infrared light unnecessary for image formation is guided to the outside of the lighting device at an early stage, and the inside of the lighting device is The temperature rise can be reduced gradually. In particular, by applying it to the reflective optical surface constituting the auxiliary imaging device, it is possible to reduce the possibility that infrared rays due to re-imaging directly increase the temperature of the tube.

Further, in the basic configuration of the lighting device, in which the control optical surface includes a refractive optical surface, by providing at least one of the refractive optical surfaces with a visible light transmitting film that reflects ultraviolet light, it is harmful. At the same time, it prevents the ultraviolet rays from being emitted to the illumination light, and at the same time, reduces the rate of the ultraviolet rays returning directly to the vicinity of the bulb, thereby gradually reducing the contribution of the bulb to a rise in temperature. By applying the above means in combination, the temperature rise of the bulb is minimized, and as a result, the crystallization of the quartz tube constituting the bulb is suppressed, and the life of the light source is extended and the efficiency is secured.

[0010]

Embodiments of the present invention will be described below in detail with reference to specific examples. FIG. 1 shows a sectional view of a first embodiment of the present invention. Reference numeral 1 denotes a light source including an electrode therein and an outside covered with a quartz tube. The light beam emitted from the arc localized near the electrode is reflected by the reflecting mirror 4a forming the reflecting optical surface, passes through the refracting optical surface 4b, and travels to another optical element (not shown). The reflecting optical surface 3 is a reflecting mirror that constitutes an auxiliary imaging device that reflects a light beam from the light source and returns the light beam to the light source, and is a spherical reflecting mirror having a center at a virtual center of the light source. These optical surfaces 3, 4a, 4b are constituted by rotationally symmetric surfaces having a common axis (optical axis).

The reflecting mirror 4a controls the distribution of a chief ray emitted from the virtual center of the light source 1 on a virtual plane placed near the refractive optical surface 4b (hereinafter referred to as a distribution control surface or a distribution control element). It is. Also, the refractive optical surface 4b
Is a refractive optical element that receives a chief ray from the distribution control surface 4a and controls its direction (hereinafter referred to as a direction control surface or a direction control element). The present embodiment has a function of converting an incident principal ray into a principal ray parallel to the optical axis.

FIG. 2 shows an example of a configuration in which such a control element is used as a means for illuminating an image forming apparatus such as a liquid crystal.
Shown in FIG. 2 irradiates the image forming apparatus 6b using integrator lenses 5a and 5b and a condenser lens 5c in addition to the basic configuration of FIG. Image forming apparatus 6b
A field lens 6a is provided immediately in front of.
In this case, each control surface placed on the light source side with respect to the integrator 5a makes the angle of the principal ray incident on the integrator 5a uniform, and the numerical aperture of the luminous flux on the incident surface of the integrator 5a is as far as possible regardless of the location. It has the function of controlling the distribution to be constant. The most important factor for the function of adjusting the numerical aperture is the distribution control surface 4a. The direction control surface 4b plays a role in aligning the direction of the principal ray incident on the integrator 5a.

Such a distribution and direction control surface can be constituted by only a reflection surface or only a refraction surface in addition to the combination of the reflection surface and the refraction surface described above. A typical example of this variation is described in Japanese Patent Application Laid-Open No. 8-53.
2381. Here, it is avoided to discuss all combinations, but the content of the present invention is not particularly limited to the combination of the control elements of the reflective surface and the refractive surface.

Now, it will be described that the determination of the shape of the reflecting mirror 4a involves a certain degree of arbitrariness. For example, assume that the first chief ray emitted from the light source 1 in FIG. 1 exits at an angle of 45 degrees with the optical axis. It is assumed that this principal ray is reflected by the reflecting mirror 4a and intersects the optical axis on an imaginary plane near the refractive optical surface 4b. The intersection of the principal ray and the reflecting mirror 4a may intersect anywhere on the extension of the principal ray emitted from the light source 1. By designating the intersection, the refractive optical element 4
By specifying the arrival position (optical axis in this case) on a virtual plane provided in the vicinity of b, the reflection angle at the reflecting mirror 4a is determined. As a result, the inclination of the reflecting mirror 4a at that point is determined. Thereafter, the shape of the reflecting mirror 4a can be sequentially determined so as to satisfy the designated distribution of the principal ray on the virtual plane. The shape of the refractive optical element 4b may be given so that the principal ray from the reflecting mirror 4a sequentially determined in this way becomes parallel to the optical axis. As described above, it can be understood that the shape and size of each control surface can be changed by changing the starting point for determining the shape of the reflecting mirror 4a. This also indicates that there is considerable arbitrariness in the distance between the light source 1, that is, the tube and the reflecting mirror 4a.

FIG. 3 shows an example of a lighting device using a parabolic mirror. The major difference from FIG. 2 is that the light beam from the light source 1 is first reflected by the reflecting mirror 2 and a refraction element having a curved surface 4a on the exit surface side (the entrance surface side is a flat surface), and further on the entrance surface side. The integrator lens 5 passes through a refractive element provided with the curved surface shape 4b (the exit surface side is a flat surface).
a. In this example, there is no auxiliary imaging device, and a light beam with a large opening angle from the light source 1 is captured using only the parabolic mirror 2. Such a configuration is used when a general-purpose light source in which a parabolic mirror or an elliptical mirror is integrated with a light source, or a light source device in which a tube itself is a reflecting mirror is used as it is. These parabolic mirrors and elliptical mirrors can be considered as a kind of reflecting mirror that determines the angle of capture. However, such a configuration may not be used when the size of the light spot of the light source 1 and the size of the image forming apparatus 6b and the required numerical aperture are not well-balanced, because the utilization efficiency of the light beam is reduced.

In general, when taking in a light beam with a large take-in angle using the parabolic mirror 2, the distance between the light source 1 and the parabolic mirror 2 becomes short. The reason is to limit the size of the parabolic mirror 2. That is, it is required that the illuminating unit be compactly packed for miniaturization. One of the factors is the size of the parabolic mirror 2. The size of a parabolic mirror is generally expressed as follows: y is the height from the optical axis, f is the focal length (that is, the distance from the light source to the vertex of the parabola), and θ is the angle measured from the optical axis on the vertex side. Next formula Given by For example, when θ is 135 degrees and y is 50 mm, and the focal length f is calculated, Becomes Therefore, the distance between the light source 1 and the vertex of the parabolic mirror 2 is about 10 mm, and a situation is created in which the reflecting mirror and the tube may almost come into contact with each other. The features of the arrangement of the light source and the illumination system have been described based on the specific examples of FIGS. In the configuration of FIG. 2, it is shown that a relatively large degree of freedom can be obtained with respect to the distance between the reflecting mirror 4a and the light source 1, whereas the use of the parabolic mirror 2 of FIG. 3 has little degree of freedom.

[0017] Among several specifications required for the illumination system, the life of the light source is important for brightness and uniformity. Particularly, in a projector, it is the most important factor when used in a general home. This is even more so in the case of an illumination system requiring a relatively small numerical aperture as in the present invention. In the case of discharge or the like, the key element is the cloudiness of the quartz bulb surrounding the electrodes. It is said that the turbidity of the tube is caused by crystallization of part of the quartz, but the temperature of the tube is a major factor in the crystallization. When the temperature of the bulb exceeds a certain critical temperature, the crystallization of the bulb proceeds rapidly. The following can be considered as factors of the temperature rise of the bulb. For example, the energy concentrated near the arc of the light source, the influence of the luminous flux emitted from the arc itself, the unevenness of the temperature due to convection in the tube, the effect of the luminous flux returning to the vicinity of the tube, and the radiant heat generated by a reflector or the like are raised. It is considered that these synergistic effects cause the temperature of the bulb to rise and the temperature to become non-uniform, thereby causing crystallization.
In general, clouding of the tube tends to occur upward with respect to the gravity of the lighting posture, and it can be understood that a slight difference in temperature has a great effect on clouding. The present invention
Among these factors, the effect of light returning to the vicinity of the tube and the effect of radiant heat due to the reflection surface are alleviated, and the life of the light source is extended.

The luminous flux emitted from the light source includes ultraviolet rays and infrared rays in addition to commonly used visible light rays. These adversely affect the operation failure and the element itself due to the temperature rise of the image element. In particular, in the case of ultraviolet rays, it is dangerous for a user to emit the light outside the apparatus. Therefore, it is necessary to remove them early in the lighting section. Normally, the parabolic mirror 2 shown in FIG. 3 is provided with a so-called cold mirror that transmits infrared light and reflects visible light. This allows infrared rays to pass through and by using a separate cooling means,
Released as heat outside the device. Generally, an alternate film of titanium oxide and silicon oxide is used for such a cold mirror. Titanium oxide also has the function of absorbing ultraviolet light, and thus can prevent the reflection of ultraviolet light to some extent. However, it is very difficult to form a transparent film having a clear rise on the ultraviolet side and the infrared side, and in the case of a cold mirror, reflection is left on the ultraviolet side. Here, for example, parabolic mirror 2
If a flat glass is provided at the exit of the tube and an ultraviolet reflecting film is applied, it is possible to prevent the ultraviolet light from being emitted first, but the return light is reflected by the parabolic mirror 2 again, and It will be concentrated near the ball.

In the case of FIG. 3, by providing such an ultraviolet reflecting film on the surfaces of the distribution control surface 4a and the direction control surface 4b, it is possible to prevent the return light of the ultraviolet light from directly concentrating near the bulb. Although the distribution control surface 4a in FIG. 3 can be directed to the parabolic mirror 2, the unnecessary light reflected from the distribution control surface 4a can be made divergent light, and the effect can be secured. I can do it. In the case of FIG. 2, in addition to the surface of the direction control surface 4a, a flat glass is provided at a portion of the spherical mirror 3 constituting the auxiliary imaging device where the light beam from the reflecting mirror 4a on the side of the direction control element exits. May be provided with an ultraviolet reflecting film. The direction control element 4a and the integrator lens 5a, and the integrator lens 5b and the condenser lens 5c in FIGS. 2 and 3 can be bonded to each other with their opposing surfaces being planes. In order to prevent deterioration, it is effective to remove the harmful light before that stage.

For infrared light, for example, by applying an infrared transmitting film to the distribution control reflecting mirror 4a of FIG. 2 or the spherical mirror 3 of the auxiliary imaging device, it is possible to effectively extract heat rays from the illumination section. In particular, in the case of the spherical mirror 3, the light flux returns directly to the bulb, which is a particularly important factor.

On the other hand, the infrared transmitting film allows ultraviolet rays and infrared rays which are relatively easily absorbed by the glass to pass through the glass, so that the temperature of the glass itself increases due to the absorption. The reflecting mirror 4a in FIG. 2, the reflecting mirror 2 in FIG. 3, and the reflecting mirror 3 as an auxiliary imaging device shown in FIG. The temperature rises. Such a rise in the temperature of the optical element due to several factors also affects the bulb of the light source 1. In particular, when the distance between the bulb and the optical element is short, this is a factor that cannot be ignored. In the case of the configuration shown in FIG. 2, since a degree of freedom can be secured in securing the distance between the tube and the reflecting mirror as described above, it is possible to provide a constant interval. It is desirable to make the interval as wide as possible. However, there is a restriction on the overall size. Therefore, when the diameter of the tube is d and the minimum distance from the electrode to the reflecting mirror is D, at least the following equation D> 2d By satisfying the relationship, the effect can be reduced. In the case of the embodiment of FIG. 2, d = 10 mm, D
= 26 mm sufficiently satisfies the above conditions.

On the other hand, in the case of FIG. 3, d = 10 mm, D = 1
0 mm, and D> 2d, which does not satisfy the required conditions. For this reason, it has been confirmed that clouding occurs earlier in the configuration using the parabolic mirror in FIG. 3 than in the configuration in FIG. It is clearly disadvantageous to cover a large acquisition angle with the parabolic mirror 2, and it is advantageous to employ an elliptical mirror even for the same quadric surface. Even if the parabolic mirror is the same, if the capture angle is narrowed and θ is up to 90 degrees, the height is 40 mm (the diameter of the parabolic mirror is 80 m).
m), the focal length f can be set as long as 20 mm. In this case, it is necessary to use an auxiliary imaging device together in order to increase the utilization efficiency. The use of the auxiliary imaging device causes a rise in temperature near the bulb because the light flux is returned to the light source, but the effect is more effective if the distance between the bulb and the reflector is increased.

Finally, FIG. 4 is a configuration diagram of a proposal made in Japanese Patent Application Laid-Open No. 8-357424 in order to reduce the size when an auxiliary imaging device is used. Reference numeral 3 in FIG. 4 denotes a spherical mirror, which constitutes an auxiliary imaging device. The light source 1 is fixed to the spherical mirror 3 and has an integral structure. In this case, the spherical mirror 3
It is clear from the figure that the size of the lens can be freely set, and it is possible to configure an illuminating device that satisfies the above-mentioned condition regarding the distance between the tube 1 and the spherical mirror 3.

[0024]

As the optical element which receives the light beam from the light source first, a reflecting mirror which covers a large solid angle and can be compactly assembled is optimal. When the reflectors closest to the light source are classified by function, they can be used as parabolic mirrors or elliptical mirrors to control the angle of incidence, reflectors to control the distribution of chief rays, and as auxiliary imaging devices. There is a reflecting mirror. With respect to the reflector having these functions, when the diameter d of the bulb and the minimum distance D from the electrode to the reflector satisfy the following condition D> 2d, the temperature of the bulb increases due to the radiation of the reflector. Thus, the progress of clouding of the tube can be suppressed. As a result, the life of the light source can be extended. Further, by applying an infrared transmitting film to the above-mentioned reflecting mirror, it is possible to effectively release the heat inside the illuminating device to the outside and prevent the heat rays from returning to the vicinity of the tube. Also,
In the case of an illuminating device in which the distribution control element or the direction control element is constituted by a refractive optical element, it is possible to prevent ultraviolet rays from returning to the vicinity of the bulb by forming an ultraviolet reflection film on the control surface. By combining and using the above, it is possible to reduce the cause of temperature rise near the bulb and prolong the life of the light source.

[Brief description of the drawings]

FIG. 1 is a schematic diagram for explaining an embodiment of the present invention.

FIG. 2 is a configuration diagram showing an embodiment in which the embodiment of the present invention is configured as a lighting device.

FIG. 3 is a configuration diagram of a lighting device using a parabolic mirror for taking in a light beam from a light source.

FIG. 4 is a schematic diagram for explaining a second embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 light source 2 capture angle control optical element 3 auxiliary imaging device 4a distribution control surface 4b direction control surface 5a, 5b, 5c optical element constituting integrator 6a field lens 6b image forming device

Claims (5)

[Claims] 1. A light source comprising an electrode and a bulb surrounding the electrode, and a reflection optics for controlling a spatial distribution of the chief ray on a virtual plane separately provided by receiving a chief ray emitted from a virtual center of the light source. In an illuminating device including a surface and at least two optical surfaces for controlling the direction of the principal ray by receiving the principal ray from the reflecting optical surface, the diameter of a bulb surrounding the electrode is d, and the electrode and the principal An illumination device characterized by satisfying D> 2d, where D is a minimum distance from a reflecting optical surface for controlling a spatial distribution of light rays. 2. A light source comprising an electrode and a bulb surrounding the electrode, and a light source comprising at least one reflecting optical surface for controlling a solid angle of a chief ray emitted from a virtual center of the light source into a lighting device. An angle control sub-group, an optical surface for controlling the spatial distribution of the chief ray on a virtual surface separately provided in response to the chief ray from the capture angle control sub-group, and a chief ray in response to the chief ray from this optical surface In an illuminating device including at least two optical surfaces for controlling the direction of light, the diameter of the bulb surrounding the electrode is d, and the minimum distance between the electrode and the reflecting optical surface for controlling the solid angle for taking in the principal ray. A lighting device characterized by satisfying D> 2d. 3. An auxiliary imaging device comprising at least one reflection optical surface for receiving and reflecting a light beam not taken into the illumination device on the reflection optical surface and condensing the light again near the electrode. 3. The lighting device according to claim 1, wherein D> 2d, where d is the diameter of the envelope to be wrapped, and D is the minimum distance between the electrode and the reflecting optical surface forming the auxiliary imaging device. 4. The illuminating device according to claim 1, wherein the reflection film on at least one of the reflection optical surfaces is formed of a visible light reflection film having infrared transmission characteristics. . 5. An illumination device according to claim 1, wherein at least one of the optical surface for controlling the spatial distribution of the chief ray and the optical surface for controlling the direction of the chief ray comprises at least one refractive optical surface. 4. The illuminating device according to claim 1, wherein said at least one refractive optical surface is formed of a visible light transmitting film having an ultraviolet reflection characteristic.