JP2000122178A - Illuminator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a compact illuminator capable of uniformly irradiating a surface to be irradiated with high efficiency with luminous flux radiated from an inexpensive surface light source such as a halogen lamp by providing a spherical mirror with center at the light emission center part of a light source and a parabolic mirror installed in a ring shape at the periphery part of the spherical mirror. SOLUTION: The concave spherical mirror 41 and the parabolic mirror 42 in ring shape arranged to surround the periphery of the mirror 41 are installed at the rear of the surface light source 40. The apertures diameters of the mirror 41 and a collector lens 44 are made nearly the same as the diameter of the glass tube of the light source 40. The luminous flux diverged from a part out of the axis of the light source 40 is made incident on the center cell of a fly-eye lens 45 as oblique light even after passing through the lens 44, and condensed on the edge part of the lens part 46B at the center part of a heat absorbing filter 46A, so that a secondary light source is formed. The light outgoing from plural seondary light sources passes through condenser lenses 48 and 49, superimposed on a mask surface 50 and projected to the position of the entrance pupil of a projection lens 51.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for illuminating a liquid crystal in a liquid crystal projector, and more particularly to a method for reducing unevenness in illumination and reducing the size of an object while using an inexpensive and flat light source such as a halogen lamp. The present invention relates to a lighting device that is advantageous and has high light use efficiency.

[0002]

2. Description of the Related Art As a general illumination system, a Koehler illumination optical system is known. Since the Koehler illumination optical system corrects the luminance distribution in the plane direction perpendicular to the optical axis, the illumination unevenness is sufficiently removed in the ordinary illumination system. It is not sufficient for the purpose of strictly suppressing the illuminance distribution in the entire region. The Koehler illumination optical system, as shown in FIG.
It has a light source 10, a spherical reflecting mirror 11, a collector lens 12, a condenser lens 15, and a projection lens 17. Since the Koehler illumination optical system does not have a fly-eye lens, it has a simple configuration.However, in an illuminating device that needs to severely suppress illuminance unevenness, the illuminance unevenness is caused by the unevenness of the brightness of the light source in the direction orthogonal to the optical axis. Also needs to be corrected. (First Fly-Eye Lens Illumination System) As shown in FIG. 5, a first fly-eye lens illumination system including a fly-eye lens is used to remove illuminance unevenness caused by uneven brightness of a light source in a direction orthogonal to the optical axis. A system has been proposed. This optical system includes, as shown in FIG.
1, a collector lens 22, a fly-eye lens 24, a condenser lens 26, and a projection lens 28. The fly-eye lens 24 has nxm lens elements 24a. The thickness of each lens element 24a is determined so that the focal position of one surface coincides with the vertex of the other surface, and each lens element 24a on the surface orthogonal to the optical axis is rectangular, and the plurality of lens elements 24a Are joined without gaps.

The collector lens 22 disposed between the surface light source 20 and the fly-eye lens 24 converts a light beam from the surface light source 20 into parallel light as shown in FIG. The distance from the collector lens 22 is substantially equal to the focal length of the collector lens 22. However, since the focal lengths of the fly-eye lens 24, the condenser lens 26, and the projection lens 28 are determined by off-axis light of the surface light source 20, the angle of oblique light emitted from the collector lens 22 is It is designed so that the focal length does not become too short. Collector lens 2
The light beam collimated to the optical axis by 2 enters from the field stop 23 side of the fly-eye lens 24, that is, the rear surface thereof, and forms a large number of secondary light sources on the aperture stop 25 side of the fly-eye lens 24, that is, the front surface.

The light from the surface light source 20, that is, a position distant from the optical axis of the filament, becomes oblique light, enters the fly-eye lens 24 from the field stop 23 side, and is emitted from the aperture stop 25 side as parallel light. In an application such as a liquid crystal projector, as shown in FIG. 5, a liquid crystal panel, that is, a rectangular mask surface 27 is provided between a condenser lens 26 and a projection lens 28, so that the emitted parallel light is projected by the condenser lens 26. It is desirable that the light is focused on the focus surface of the lens 28, that is, on the position of the mask surface 27. Further, in order to make the focus surface of the projection lens 28 a completely uniform illuminance surface, it is necessary that the rectangular shape and the focus surface of the lens element 24a of the fly-eye lens 24 are completely similar to each other. On the other hand, the light beam formed as a secondary light source on the fly-eye lens 24 is imaged by the condenser lens 26 at the position of the entrance pupil of the projection lens 28.

[0005] The spherical reflecting mirror 21 behind the surface light source 20 is for returning the luminous flux from the light source backward to the front again. When the effective NA of the spherical reflecting mirror 21 is increased, more luminous flux is forwarded. You can go back.

However, the NA of the spherical reflecting mirror 21 is
Satisfying the condition with respect to off-axis rays while increasing the size of the lens increases the number of lenses and the diameter of the collector lens 22 due to the design of the collector lens 22, which makes it difficult to reduce the size of the entire illumination system. . Further, the collector lens 22 itself passes a parallel light beam as a parallel light beam to all of the n × m lens elements 24a, so that the aperture is required to be substantially equal to the diameter. Even if the NA of the spherical reflecting mirror 21 is reduced, the fly-eye lens 24 It is meaningless if is large, and there is a limit to miniaturization in this illumination system. (Second fly-eye lens illumination system) As shown in FIG. 6, a second fly-eye lens illumination system including a fly-eye lens for removing illuminance unevenness due to uneven brightness of a light source in a direction orthogonal to the optical axis, as shown in FIG. , A parabolic reflector 31, a fly-eye lens 33, condenser lenses 34 and 35, and a projection lens 37.

In this case, since the light source 30 is a point light source, there is no need to consider an off-axis light beam.
The reflecting mirror 31 can be a paraboloid. In the case of this fly-eye lens illumination system, the light beam becomes parallel to the optical axis after being reflected by the parabolic reflector 31, and is incident on the fly-eye lens 33 as it is. It does not require a collector lens as in a lens illumination system. However, in actuality, there is a discharge arc length that cannot be ignored, and there are restrictions such as that the diameter of the parabolic mirror 31 must be maintained at a certain value or more. However, if there is a light beam emitted from the front of the point light source 30, as long as such an illumination system is used, the point light source 3
Since the light flux emitted from the front of 0 becomes stray light in the illumination system, it does not contribute to the improvement of the brightness of the subject illumination.

For this reason, if a general halogen lamp is used in the second fly-eye lens illumination system, the light beam emitted forward cannot be used as a secondary light source because there is no collector lens. Parabolic mirror 3 in FIG.
A plurality of secondary light sources are formed on the condenser lens 34 of the light flux reflected by the light source 1. These secondary light sources are imaged on the entrance pupil of the projection lens 37 by the condenser lens 35. In the case of such an illumination system, it is recommended that the point light source 30 has a small light emitting area as described above. In the current products, these include metal halides, xenon lamps and the like, but these have the problem that the cost of the illumination optical system including the lighting circuit is very high.

[0009]

The above-mentioned conventional lighting device has the following problems. A first problem is that in the first fly-eye lens illumination system having a surface light source, it is necessary to reduce the size of the collector lens in order to realize the miniaturization of the entire apparatus, that is, the shortening in the optical axis direction. Since it is important how to increase the luminous intensity in the direction of the projection lens 28 to secure a large illuminance over the entire surface to be irradiated, as shown in FIG. The role of the reflecting mirror 21 is important because the reflecting mirror 21 returns the light beam emitted backward to the projection lens 28 side. It is easily conceivable to increase the NA of the reflecting mirror 21 so as to return the light beam directed backward to the projection lens 28 side. However, in the collector lens 22 provided immediately before the conventional fly-eye lens 24, N of reflector
As A increases, the aperture of the collector lens 22 also increases. Moreover, the collector lens 22
Since the angle of incidence becomes large and the light beam must be bent more greatly, the design becomes difficult, and depending on the condition, a large number of lenses may be required. The size of the collector lens 22 is also affected by the size of the filament of the surface light source 20. When the focal lengths of the fly-eye lens 24, the condenser lens 26, and the like are determined in correspondence with the projection lens 28 ignoring the size of the filament, the collector lens 22 is often considerably large. In that case, it is necessary to reconsider the balance between the magnification and the focal length of the entire apparatus.

Increasing the NA of the spherical mirror 21 behind the surface light source 20 not only makes optical design difficult, but is disadvantageous in reducing the size, and reducing the NA increases the illuminance on the optical axis. There is a problem that can not be. The second problem is as follows. In the second fly-eye lens illuminating system having a point light source, light emitted by an arc discharge such as a commonly used metal halide lamp may have a point light source due to its structure if the light emitting portion has a certain length of arc. In many cases, the electrode part is located in front of the lamp, ignoring light from the front,
It mainly used only the reflected light of the parabolic mirror combined. Since such a configuration has high efficiency, it is often used for illumination for a liquid crystal projector. However, assuming that an inexpensive halogen lamp is used, a large amount of light is emitted from the front of the halogen lamp and cannot be ignored.
Utilizing this forward light beam requires some light condensing means.

A third problem is that with respect to an illumination system used in a future liquid crystal projector, if the size of a liquid crystal panel or various mirrors is reduced, it becomes difficult to obtain sufficient brightness as an illumination device. In particular, the size of the liquid crystal panel is currently 1
It is desirable to provide an illuminating device which is becoming smaller than 2 inches (25.4 mm), and which can efficiently illuminate the illuminating light flux and irradiate an illuminating light beam with high illuminance on a small area.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in a conventional lighting device, and has been made in consideration of the problems described above by using a light beam emitted from a cost-effective surface light source such as a halogen lamp. It is an object of the present invention to provide a small-sized lighting device capable of uniformly irradiating an irradiated surface with high efficiency.

[0013]

According to the present invention, there is provided a light source for emitting light, a collector lens having a focal length determined based on an entrance pupil diameter, a pupil distance, and an effective diameter on an entrance side of a projection lens.
A fly-eye lens, a lens member at the center of the heat ray absorption filter, a condenser lens, a spherical mirror around the emission center of the light source, and a parabolic mirror installed in a ring around the spherical mirror. It is a lighting device characterized by the above. Embodiments of the present invention are as follows. The diameter of the spherical mirror is substantially the same as the diameter of the light source section (outer wall glass section). The inside diameter of the parabolic mirror (the diameter replacing the spherical mirror) is substantially the same as the tube diameter of the light source section (outer glass section). The diameter of the collector lens is substantially the same as the diameter of the light source section (outer wall glass section). The collector lens is made of a heat ray absorbing type glass material. The collector lens is made of a glass material having high refractive index and high heat resistance. A heat ray absorbing filter is arranged between the fly-eye lens and the condenser lens, and only the central portion has a lens effect. A member having a lens function only at the center of the collector lens has the same shape as the center cell of the fly-eye lens. The heat ray absorbing filter and the central lens member serve as a secondary light source of an illumination system. The condenser lens unit has a two-part configuration including an aspherical lens and a plano-convex lens (including an aspherical shape) disposed immediately before the light source side of the focus surface (mask surface) of the projection lens. The condenser lens section has a single aspheric lens. The projection lens unit may be a zoom lens or a varifocal lens. A liquid crystal panel is arranged at a position of a focus surface (mask surface) of the projection lens, and a polarizing plate and the like are further arranged to be used for a liquid crystal projection television or a liquid crystal projector.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. As shown in FIG. 1, in the illumination device of the embodiment, a concave spherical mirror 41 and a parabolic mirror 42 on a ring arranged to surround the concave mirror 41 are arranged behind a planar light source 40. The concave spherical mirror 41 and the parabolic mirror 42 are arranged so as to be centered at the same position on the optical axis. Curvature radius R of concave spherical mirror 41 is parabolic mirror 42
Is 1/2 of the R component. When R is increased, that is, when the focal length of the parabolic mirror 42 is increased, the luminous flux N
Since the diameter of the parabolic mirror 42 is not increased in order to increase A, it is necessary to select a well-balanced optimum value for the entire apparatus at the time of design. The collector lens 44 is arranged immediately before the light source 40. The collector lens 44
Since the light diverging forward from the light source 40 is converted into a parallel light flux, the distance between the light source 40 and the collector lens 44 is substantially equal to the focal length of the collector lens 44.

The outer diameter of the collector lens 44 is made substantially equal to the diameter of the glass tube of the light source 40. The reason is that if the outer diameter of the collector lens 44 is increased, the light beam reflected by the parabolic mirror 42 may be blocked. In order to convert as many light beams as possible from the light source 40 into parallel light beams, the collector lens 44 is used.
As close as possible to the light source 40 and the collector lens 44
Is set to be approximately the same as the diameter of the glass tube of the light source 40. If the outer diameter of the lens 44 is approximately equal to the diameter of the glass tube of the light source 40, it is easy to design the focal length of the collector lens 44 to be short, and this can greatly contribute to downsizing of the entire lighting device. Since the collector lens 44 is disposed adjacent to the light source 40 having high heat generation, the collector lens 44 should employ a glass material having high heat resistance. In addition, when a glass material having a high refractive index is used for the collector lens 44, a design advantageous for further miniaturization of the device can be realized. Further, when a heat ray absorbing type glass material is employed, the infrared light radiated from the light source 40 is partially cut, so that the thermal load on the fly-eye lens 45 can be reduced.

Another problem in the design of the collector lens 44 is the processing of a light beam diverging from outside the optical axis of the light source 40. If the focal length of the collector lens 44 is shortened to increase the NA, it becomes difficult to convert the off-axis light beam into a parallel light beam, and the lens system is designed with a sense of balance so as not to complicate the lens system. Since the incident height of the collector lens 44 largely depends on the shape of the light emitting portion of the light source 40, attention should be paid to the selection of the light source 40, that is, the selection of the filament shape. As described above, the luminous flux diverged from the on-axis and off-axis of the light source 40 by the collector lens 44 is converted into a parallel luminous flux, but the luminous flux diverged from the off-axis is converted into oblique light even after passing through the collector lens 44 as a fly-eye lens. It is incident on the central cell at 45. This light beam is condensed by the fly-eye lens 45 at the edge of a lens portion 46B provided at the center of the next heat ray absorption filter 46A, and forms a secondary light source. This lens part 46B
Works as a field lens for such a light beam diverged from the axis of the light source 40.

The rectangular mask surface 50 after passing through the condenser lenses 48 and 49 can be designed so that the light beam can cover the entire surface. In FIG. 1, the condenser lens 48 on the side close to the fly-eye lens 45 is an aspherical lens to reduce light loss, and the number of lenses is reduced as much as possible. The condenser lens 48 has a role of converting a light beam from the secondary light source into a parallel light beam, and converts the parallel light beam into a condenser (collimator).
The lens 49 projects the light at the position of the entrance pupil of the projection lens. With this design, regarding the central optical system such as a light beam passing through the collector lens 44, the mask surface 50 and the condenser lens 48 are conjugate, the incident height of the fly-eye lens 45 is h, the mask surface is h, Where H is the image height of the lens, f _{con is} the focal length of the condenser lens 48, and f _int is the focal length of the center cell of the fly-eye lens 45, and H / h ≒ f _con / f _int . easy.

However, the light beam turned back by the parabolic mirror 42 at the peripheral portion is incident on the fly-eye lens 45 obliquely by the off-axis light beam of the surface light source 40.
By writing the surface shape of each cell except for the central cell, the light beam forms a secondary light source with little aberration by forming an aspherical shape that is offset or inclined from each optical axis. 46 may be a plane. An aperture stop 47 is provided immediately before the heat ray absorption filter 46A (on the side of the projection lens), and the diameter of the aperture stop 47 determines the numerical aperture of the illumination system. The aperture stop diameter Θ is set to Θ ≒ sin θ · 2f _con so that the focal position of the condenser lens 48 is at the position of the mask surface 50, and the aperture diameter is such that the condenser lens 48 and the projection lens Although it depends on the imaging performance of the combination of the condenser (collimator) lens 49 for narrowing down to the position of the entrance pupil, the light beam can be used most effectively by covering the entire range in which the secondary light source is formed.

Since the light emitted from the plurality of secondary light source images is weighed on the mask surface 50, the unevenness in brightness and color of the light source 40 has no effect on the mask surface 50. FIG. 3 shows the shape of the mask surface. The aperture size of the mask surface 52 is designed such that the length d of the vertical and horizontal diagonal lines is substantially equal to the diameter of the incident side object image circle 53 of the projection lens. Since this aspect ratio can be changed depending on the size of the original to be illuminated, it is set to, for example, a: b. FIG. 2 is a front view of the fly-eye lens 60. For example, if the mask surface 52 is a: b for the above-described reason, the ratio e: f per cell of the fly-eye lens 60 is also the same. This improves light use efficiency.

[0020]

As described above, by satisfying the constitution and constitutional conditions of the present invention, a light source unit having a high surface light source such as a halogen lamp which is less expensive than a metal halide lamp or the like can be used, and the rear of the light source can be used. A concave spherical mirror having a diameter about the diameter of the glass tube of the light source, and a ring-shaped parabolic mirror arranged so as to surround it, and the diameter of the glass tube of the light source in front of the light source on the opposite side This is a lighting device equipped with a collector (condensing) lens of a degree, and a light beam directed backward from the light source reflected by the concave spherical mirror and a light beam directed directly forward from the light source are collimated by the collector lens in front of the light source, and are rearranged. The high-angle light beam that cannot be captured by the concave spherical mirror heading toward the mirror is directly collimated by the ring-shaped parabolic mirror around the concave spherical mirror, and this light beam is collected by the front collector lens. , Since only the glass tube diameter of approximately sources without a bore, it never is most deficient. Also, in the present invention, a number of secondary light sources are formed on a heat ray absorbing filter by using together with a fly-eye integrator whose peripheral cell is an aspherical surface. The light flux diverging from the surface light source (the periphery of the filament) can be collected.

With such a configuration, even if an inexpensive halogen lamp having a high surface light source property is used, the light use efficiency is high, and a small illumination system with less illuminance unevenness on the surface to be irradiated can be realized. It is. Further, it is possible to realize a small-sized illumination system which is hardly affected by luminance unevenness in the surface direction and the angle direction of the light source and has less illuminance unevenness on the irradiated surface. In the future, many LCD panels of 1 inch or less will appear,
In the case of adoption, a liquid crystal projector of uniform and high image quality can be realized by disposing a liquid crystal panel on the mask surface of the present invention.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an illumination optical system according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a shape of a mask slit surface.

FIG. 3 is a schematic configuration diagram of a fly-eye lens.

FIG. 4 is a configuration diagram of an illumination optical system in a conventional general Koehler illumination method.

FIG. 5 is a configuration diagram of an illumination optical system to which a conventional fly-eye integrator is applied.

[Fig. 6] Applying a conventional fly-eye integrator,
It is a block diagram of the illumination optical system which adopted the parabolic surface for the reflecting mirror.

[Explanation of symbols]

 Reference Signs List 10 light source 11 spherical reflector 12 collector lens 13 field stop 14 aperture stop 21 spherical reflector 23 field stop 24 fly-eye lens 25 aperture stop 28 projection lens 30 light source 31 parabolic reflector 33 fly-eye lens 34 condenser lens 35 condenser lens 36 Mask surface 40 Light source 41 Spherical reflector 42 Parabolic reflector 44 Collector lens 45 Fly-eye lens 46A Heat absorption filter 46B Central lens unit 49 Condenser (collimator) lens 50 Mask surface 51 Projection lens

Claims (13)

[Claims] 1. A light source for emitting light, a collector lens having a focal length determined based on an entrance pupil diameter, a pupil distance, and an effective diameter on the entrance side of a projection lens, a fly-eye lens having a spherical center cell only, and a heat ray A lighting device comprising: a lens member at the center of an absorption filter, a condenser lens, a spherical mirror centered on a light emitting center of the light source, and a parabolic mirror installed in a ring shape around the spherical mirror. apparatus. 2. The apparatus according to claim 1, wherein the diameter of the spherical mirror is substantially the same as the diameter of the light source section (outer wall glass section).
The lighting device according to the above. 3. The illumination according to claim 1, wherein the inner diameter of the parabolic mirror (the diameter that replaces the spherical mirror) is substantially the same as the tube diameter of the light source section (outer wall glass section). apparatus. 4. The illuminating device according to claim 1, wherein the diameter of the collector lens is substantially the same as the diameter of the tube of the light source section (outer wall glass section). 5. The lighting device according to claim 1, wherein the collector lens is made of a heat ray absorbing type glass material. 6. The illumination device according to claim 1, wherein the collector lens is made of a glass material having a high refractive index and a high heat resistance. 7. The illuminating device according to claim 1, wherein a heat ray absorbing filter is disposed between the fly-eye lens and the condenser lens, and only a central portion has a lens effect. 8. The illuminating device according to claim 1, wherein the member having only a central portion of the collector lens having a lens function has a shape equivalent to a central cell of a fly-eye lens. 9. The lighting device according to claim 1, wherein the heat ray absorbing filter and the central lens member serve as a secondary light source of an illumination system. 10. A condenser lens portion comprising a plano-convex lens (including an aspherical shape) disposed immediately before the aspherical lens and the light source side with respect to the focus surface (mask surface) of the projection lens.
The lighting device according to claim 1, wherein the lighting device has a single-plate configuration. 11. The lighting device according to claim 1, wherein the condenser lens section is constituted by one aspherical lens. 12. The lighting device according to claim 1, wherein the projection lens unit is a zoom lens or a varifocal lens. 13. A liquid crystal projection television or a liquid crystal projector, wherein a liquid crystal panel is arranged at a position of a focus surface (mask surface) of the projection lens.
The lighting device according to claim 1.