JPH11125795A - Lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the lighting device which can be reduced in cost while making the divergence angle of lighting luminous flux by improving the use efficiency of the luminous flux from a light source. SOLUTION: This lighting device consists of the light source 1a which has a relatively small light spot, an optical element 1b which determines the taking-in solid angle of the luminous flux, 1c which controls the spatial distribution of the luminous flux, 1d which controls the direction of the luminous flux, a 1st integrator 1e and a 2nd integrator 1f which has many curved surfaces formed on the surfaces in a grating shape, and a condenser lens 1g and irradiates an image formation part with the luminous flux from the light source. In this case, the projection luminous flux from 1g is nearly as large as or larger than the circle circumscribed with the external diameter of the image formation part, 1e has the same surface shape and external diameter shape with formed optical elements, and 1e and 1f are in the same shape. Consequently, while the cost is reduced, the lighting device which has high efficiency and illumination luminous flux with a small divergence angle is actualized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting device used as a part of a projection type display device which requires a light beam having a high efficiency and a small opening angle.

[0002]

2. Description of the Related Art One of the present applicants is PCT / JP96 /
In 01767, one form of a projection display device was proposed. Among them, the illumination device, which is one of the basic components of the projection display device, controls the relationship between the control of the angle of luminous flux from the light source, the illuminance distribution, and the direction, and controls them using optical elements. A proposal was made on specific means for realizing it.

FIG. 8 shows a typical embodiment among them. In the figure, a light source 1a is composed of a discharge lamp such as a metal halide lamp. A chief ray emitted from a virtual center of the light source (for example, a mechanical center between two electrodes) is reflected by a first reflecting mirror 1c that performs both the control of the taking-in angle and the distribution, and enters the direction control lens 1d. Next, the direction control lens 1d
The light beam having passed through the light source irradiates a target image forming unit 2 via two integrators 1e and 1f and a condenser lens 1g constituting a shape conversion part group. Image forming unit 2
Is a condenser lens such as 2a and 2c and a transmissive T
It comprises a passive image forming apparatus 2b which functions as an optical switching element such as N liquid crystal. Image forming unit 2
The light flux selectively reflected or transmitted by the function of is enlarged and projected on the screen by the function of the image forming unit 3. The specific configuration of the image forming unit 2, the type of the element (including the transmission type and the reflection type), and the specific content of the image forming unit 3 are not essential to the present invention, and thus the description thereof is omitted.

In this embodiment, it should be noted that the light beam control subgroup includes a reflecting mirror 1c and a lens 1d, and controls the opening angle, the opening angle distribution, the illuminance distribution, and the direction of the light beam before entering the integrator. That is, the effect of the integrator as a means for improving the lighting efficiency is significantly improved. See PCT / JP96 / 017 for details of the reason.
67 has been described using a specific example. However, in the conventional example shown in FIG. 8, since there are many optical elements in the optical path, there is a problem that the light flux loss due to the surface reflection at the interface of the optical elements increases, and good illumination efficiency cannot be obtained.

[0005] In addition, since a light beam whose opening angle is kept small by the light beam control subgroup enters the integrator lens, internally reflected light and scattered light from the peripheral edge are generated on the side surface of the integrator. The internally reflected light and the scattered light are projected on a screen (not shown), which is one of the causes of a decrease in contrast.

[Problems to be solved by the invention]

The present invention aims to reduce the cost and eliminate stray light while improving the use efficiency of the light flux from the light source.
An object of the present invention is to provide a lighting device having a highly efficient illumination light beam with a small opening angle.

[Means for Solving the Problems]

In order to achieve the above object, an illuminating device according to one aspect of the present invention includes a light source and at least one optical surface that receives a chief ray emitted from a virtual center of the light source and controls a capturing solid angle thereof. (The optical surface means a boundary surface that has the function of changing the path of a light beam, such as a reflecting mirror, a refracting surface of a lens, a Fresnel lens, a diffraction grating, a gradient index element, etc.) At least two optical surfaces, an optical surface for controlling the spatial distribution of the chief ray on a virtual plane provided in the traveling direction of the chief ray to be emitted and an optical surface for controlling the direction of the chief ray from this surface, A light flux controlling subgroup, an integrator lens including a first integrator and a second integrator having a large number of curved surfaces formed in a lattice on the surface thereof, and a condenser lens. A plurality of optical elements formed in one integrator have the same surface shape and outer diameter shape, and the first integrator and the second integrator are constituted by optical elements having the same shape. The illumination device of the present invention emits light from a condenser lens. The light beam to be emitted has a size substantially equal to or less than a circle circumscribing the outer diameter of the image generating unit.

In a preferred embodiment of the present invention, the internal reflection generated on the side of the integrator is removed, stray light projected on the projection screen can be eliminated, and the contrast can be improved.
It is preferable that the size of the integrator is formed so as to include the maximum diameter of the light beam incident on each of the first and second integrators.

In a preferred embodiment of the present invention, an optical surface for controlling the direction of the principal ray is provided on the incident surface side and the first surface is provided on the exit side.
The surface having the function of the integrator constitutes an integral refractive optical element, and the surface having the function of the second integrator on the incident surface side and the refractive surface of the condenser lens constitute the integral refractive optical element on the exit side. . An integral structure can be obtained by bringing the lens and the lens into close contact with an adhesive. With the integrated structure, the interface can be eliminated and the illumination efficiency can be improved. In addition, by forming an optical element having a plurality of optical elements such as an integrator lens and a circular lens in close contact with each other, it is possible to reduce an adjustment process such as center axis alignment of the integrator lens.

In a preferred embodiment of the present invention, one set of orthogonal boundaries formed by a plurality of optical elements in the integrator lens coincides with horizontal and vertical axes orthogonal to a normal passing through the central axis of the integrator lens. It is preferable to configure the integrator lens as described above.

Further, in a preferred embodiment of the present invention, the degree of freedom at the time of assembling adjustment can be ensured, the interface can be reduced and the illumination efficiency can be improved, so that the second integrator and the condenser lens can be combined with the second integrator. It is preferable to have a mechanism for adjusting the condenser lens while being in close contact with the liquid through a liquid having a refractive index similar to that of the condenser lens.

In a preferred embodiment of the present invention, the first integrator and the second integrator are configured as an integrated optical element. Further, in the light flux controlling subgroup, an integral refractive optical element having a surface for controlling the spatial distribution on the incident side of the light beam and a surface for controlling the direction on the exit side is configured. As a result, the illumination efficiency is improved by reducing the number of interfaces, and the number of components and the number of assembly steps can be reduced by omitting the optical element, thereby reducing costs.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of a lighting device according to the present invention will be described below with reference to FIGS. FIG. 1 is a cross-sectional view for explaining the overall configuration of a lighting device according to an embodiment of the present invention. FIG. 2 is a cross-sectional view for explaining the operation principle of the integrator. FIG. 3 is a cross-sectional view showing the miniaturization of the lighting device. FIG. 4A is a front view of a first integrator lens of the illumination device shown in FIG. FIG. 4B is a front view of a second integrator lens of the illumination device shown in FIG. FIGS. 5, 6, and 7 are cross-sectional views when the optical element is formed as an integral structure.

Embodiment An embodiment of a lighting device according to the present invention will be described in detail with reference to FIG.

The illumination device of the present invention shown in FIG. 1 has a rotationally symmetric shape with respect to the optical axis for light emitted from a light source 1a having a relatively small light spot such as a xenon lamp or a metal halide lamp placed along the optical axis. Reflective optical element 1b
And reflected toward the right side of the figure. The reflective optical element having a rotationally symmetric shape with respect to the optical axis is, for example, a parabolic mirror. The light emitted from the reflection optical element is the lens 1c
Thereby, the luminous flux is controlled so that the principal ray has a predetermined distribution on the virtual plane. Although the position of the virtual plane is arbitrary, a location convenient for design, such as the vicinity of the subsequent optical element, is selected. The light whose distribution is controlled on the virtual plane is the lens 1
The direction of the principal ray is controlled by d to be parallel to the optical axis of the illumination device, and the image forming apparatus 2 is irradiated by the integrator lens including the first integrator 1e and the second integrator 1f and the condenser lens 1g. .

Next, the operation principle of the integrator lens will be described with reference to FIG. The incident light beam from the lens 1d is an arbitrary lens 1e among a plurality of lenses constituting 1e.
A light beam having an opening angle γ is formed on a. This opening angle γ
Is a lens 1fa corresponding to 1ea on 1f.
The image forming unit 2 via the condenser lens 1g
Imaged on top. On the other hand, the principal ray from the lens 1d enters the lens 1e in parallel with the optical axis, passes through the center of the lens 1fa, and reaches the image forming unit 2 in the same manner. When an integrator lens is constructed based on such a principle, the interval between 1ea and 1fa is almost equal to the focal length of 1ea, and 1fa and 1fa.
The optical magnification β of g is the ratio of 1ea to the size of the image forming unit 2.

Further, in the embodiment, the sizes of 1f and 1g are set so that the size of the light beam emitted from the condenser lens 1g is substantially equal to the circle circumscribing the outer diameter of the image forming unit 2. The distance between the image generating unit 2 and 1 g is set so as to reduce the opening angle θ of the light beam shown in FIG. At this time, an integrator lens according to the above-described operation principle is configured. In other words, the distance between the first integrator 1e and the second integrator 1f satisfies the magnification relationship, and the plurality of lenses forming 1e and 1f have a surface shape, and the outer diameter shape satisfies the magnification relationship. It has a similar shape. At this time, as shown in FIG. 3, if the light beams emitted from the condenser lens 1g are substantially equal to or smaller than a circle circumscribing the outer diameter of the image forming unit 2, the light beams 1f, 1g and the image forming unit 2 are adjusted.
Is very advantageous for miniaturization of the entire lighting device.

The integrator lens that operates in this way is very effective in terms of effective use of light beams and uniformity of illuminance. However, as described in Japanese Patent Application Laid-Open No. 7-174974, a light beam from a light source is parabolic. In a configuration in which the light beam is directly transmitted to the integrator lens by a mirror or the like, the divergence angle and distribution of the luminous flux on the incident surface of the integrator lens become non-uniform. Therefore, when 1e and 1f are configured by a lens array of the same size, Light flux coupling loss occurs between them. Also, as described in PCT / JP96 / 01767, it is necessary to reduce the opening angle of the illumination light beam.
This increases the possibility of luminous flux loss between e and 1f.

However, in the embodiment, the lenses 1c and 1c are used before the light beam enters the integrator lens.
By optimizing the size of the opening angle of the light beam and the opening angle distribution by 1d, the surface shape and the outer diameter shape of the plurality of lenses formed in the first integrator 1e are the same, and the second integrator 1f is , 1e, and the luminous flux emitted from the condenser lens 1g has a light flux loss of an integrator lens configured to have a size substantially equal to a circle circumscribing the outer diameter of the image forming unit 2. Can be kept to a minimum.

Among the light beams incident on the integrators 1e and 1f, the light beams reaching the peripheral portions of the integrators 1e and 1f generate internal reflection on the side surfaces of the light beams 1e and 1f due to a small opening angle. The internal reflection may cause stray light on the image forming part after the image forming part 2 and further on the projection screen depending on the exit angle, which may affect the contrast and the like. There are various methods to remove the internal reflection, such as wedge-filling the surface of the generator or applying a dark coat, or changing the size of the integrator. In the case of the integrator as in the embodiment, the lighting device itself is used. Since the size of the integrator can be freely set as long as the size of the integrator is maintained, the emission direction of internal reflection can be changed by increasing the size of the integrator, thereby removing stray light. Specifically, as shown in FIG. 4A, the integrator 1e is configured to include the maximum diameter 11 of the light beam incident on the integrator 1e and the maximum diameter 12 of the light beam incident on 1f. Further, as shown in FIG. 4B, the integrator 1f is configured so as to include the maximum diameter 11 of the light beam incident on the integrator 1e and the maximum diameter 12 of the light beam incident on 1f.

Next, as is clear from the operation principle of the integrator lens, it is important to secure the alignment accuracy between the integrators in order to secure the illumination efficiency. In addition, since the axis shift between the integrators changes the traveling direction of the illumination light beam, the entire surface of the image forming unit 2 may not be irradiated. When the lens 1d and the first integrator 1e have a close contact structure as in the embodiment and the second integrator 1f and the condenser lens 1g have a close contact structure, in order to ensure the alignment accuracy between the integrators, It is important to ensure the alignment accuracy between the optical elements at the time of forming the contact structure. In the embodiment, as shown in FIG. 4, with respect to the center axis 13 of the integrator lens, an integrator lens in which a horizontal axis 14, a vertical axis 15 and a set of orthogonal lines of boundaries formed by a plurality of optical elements coincide. With this lens arrangement, the center reference on the integrator side when creating a contact structure can be taken. Alignment accuracy can be ensured using this center reference. This makes it possible to perform axis alignment between the integrators on the basis of the outer diameter of the circular lens and to omit the adjustment process.

The integrator lens is generally manufactured by molding at a low cost. Since molding is performed at a very high temperature, the molded product is stretched due to strain, and the position of each lens is shifted. The fact that the integrator lens has a lens arrangement as shown in FIG.
Even if distortion occurs during molding, the center standard can be taken.
Since the integrator and the second integrator are molded from the same mold, displacement of individual lenses due to distortion can be absorbed. This ensures illumination efficiency and improves the yield of integrators.

In the embodiment, 1f and 1g may be brought into close contact with each other via a liquid having a refractive index substantially equal to the refractive index of both. As a result, it is possible to move 1 g while being in close contact with each other, so that the deviation in the traveling direction of the light beam caused by the axial deviation between the integrator lenses can be adjusted with 1 g.
The entire surface of the image forming section 2 can be satisfactorily irradiated.

Further, it is easily conceivable to adopt a three-dimensional layout in which the optical path of the lighting device is folded back by a plurality of mirrors to reduce the size of the entire device. In the case of a three-dimensional layout, a rectangular light beam that reaches the image forming unit 2 rotates around the axis depending on the turn-back state of the optical path, and the light beam may not cover the entire surface of the image forming unit 2. In this case, it is necessary to rotate the integrator that forms the rectangular light beam around the optical axis of the lighting device. Generally, it is very difficult to accurately rotate a rectangular lens about an axis. In the case of the integrator of the illumination device according to the present invention, the integrator can be rotated about the axis by a simple method of simply rotating the lens based on the outer diameter of the attached lens.

Next, since a high target value is generally set for the amount of luminous flux reaching the image forming section 2, it is advantageous to reduce the number of interfaces in the optical path of the illumination device to reduce the influence of surface reflection. It is. In the conventional example as shown in FIG. 8, even if the illumination efficiency is improved by the light flux controlling subgroup and the integrator, the efficiency cannot be sufficiently improved due to the influence of the interface. In such a case, it is necessary to reduce the refractive index difference between the optical elements and reduce the number of interfaces.

For example, as in the embodiment shown in FIG. 1, when the lens 1d for controlling the direction of the light beam and the integrator 1e have the same refractive index, and the integrator 1f and the condenser lens 1g have substantially the same refractive index, 1d and 1e are used.
Are adhered to each other using an adhesive approximately equal in both refractive indices to form an integral optical element, and if 1f and 1g are adhered to each other using an adhesive approximately equal in both refractive indices to constitute an integral optical element, an interface is formed. It is possible to reduce.

Next, when the number of interfaces is reduced by omitting each optical element, as shown in FIG. 5, 1d and 1e and 1f and 1g can be each one optical element. Also, since 1e and 1f have the same refractive index, the arrangement of the integrator is changed as is easily understood from FIG.
As shown in FIG. 6, one optical element can be used, and a close contact structure using an adhesive can be adopted. Further, even in the light flux controlling subgroups 1c and 1d, an integral structure as shown in FIG. 7 is formed by using two surfaces, that is, a surface for controlling the distribution of the principal ray and a surface for controlling the direction of the principal ray. It is possible to control the opening angle and the opening angle distribution. Also one
When c and 1d have substantially the same refractive index, a close contact structure via an adhesive can also be obtained. In the case where the optical element in the optical path of the illuminating device is formed as one optical element in a portion, the number of parts, assembly and adjustment steps can be reduced, which is very advantageous for cost reduction. As described above, the present invention is not limited to the above-described embodiment, but can take various forms.

[0028]

As described above, according to the illuminating device of the present invention, the optical system for controlling the distribution and direction of the light beam from the light source is provided, so that the light beam emitted from the condenser lens has the outer diameter of the image forming unit. Has a size substantially equal to or smaller than the circle circumscribed by the first integrator and the second integrator.
By configuring the integrators to have the same shape, it is possible to reduce the number of parts and improve the yield while minimizing the luminous flux loss at the integrator lens. In addition, by providing the size of the integrator lens so as to include the maximum diameter of the incident light beam, it is possible to eliminate internal reflection and eliminate stray light. In addition, it is possible to improve the alignment accuracy of the integrator lens by arranging the lenses such that the orthogonal boundary line of the plurality of lenses in the integrator lens coincides with the horizontal and vertical axes of the integrator lens and providing an integrator axis reference. . The lighting device of the present invention has a close-contact structure or an integral structure by combining the respective optical elements, thereby reducing the influence of surface reflection, obtaining good lighting efficiency, and reducing the number of parts. This makes it possible to reduce the adjustment process such as axis alignment between integrators. This makes it possible to realize a low-cost, highly efficient illumination device having an illumination light beam with a small opening angle.

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating the principle of operation of the integrator.

FIG. 3 is a cross-sectional view showing the miniaturization of the lighting device.

FIG. 4 is a front view of the integrator according to the embodiment of the present invention.

FIG. 5 is a cross-sectional view when the surface for controlling the direction of the principal ray and the first integrator are integrated, and a cross-sectional view when the second integrator and the condenser lens are integrated.

FIG. 6 is a cross-sectional view when a first integrator and a second integrator are integrated.

FIG. 7 is a cross-sectional view in a case where a surface for controlling the spatial distribution of the principal ray and a surface for controlling the direction of the principal ray are integrated.

FIG. 8 is a cross-sectional view illustrating a configuration of a conventional lighting unit shown in FIG. 7 of PCT / JP96 / 01767.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Illumination device of this invention 1a Light source 1b 1c 1d 1e 1f 1g Optical element of illumination device 2 Image forming part 2a 2c Optical element of image forming part 2b Image forming device 3 Image forming part 3a 3b 3c 3d 3e Optical element of image forming part

Claims (7)

[Claims] 1. A capture angle control subgroup including a light source, at least one optical surface for receiving a chief ray emitted from a virtual center of the light source and controlling the capture solid angle, and the progress of the chief ray emitted from this subgroup. At least an optical surface having a function of mainly controlling the spatial distribution of chief rays on a virtual surface provided transversely to the direction, and an optical surface having a function of receiving chief rays from this surface and mainly controlling the direction thereof; A light flux controlling part group including two optical surfaces, an integrator lens including a first integrator and a second integrator having a large number of curved surfaces formed in a lattice shape on the surface, and a condenser lens; In the illumination device that irradiates the image forming unit with light, the light flux emitted from the condenser lens is substantially equal to a circle circumscribing the outer diameter of the image forming unit. It has come of or less in size, the surface shape of the plurality of optical elements formed on the first integrator, and with the outer diameter shape is the same, the first
A lighting device, wherein the integrator and the second integrator are optical elements having the same shape. 2. The illumination device according to claim 1, wherein the size of the integrator lens includes a maximum diameter of a light beam incident on each of the first and second integrators. 3. An optical surface for controlling the direction and the first integrator are formed by an integral optical element.
2. The device according to claim 1, wherein the second integrator and the condenser lens are formed as an integrated optical element.
The lighting device according to the above. 4. An integrator lens according to claim 1, wherein a set of orthogonal lines formed by a plurality of optical elements coincides with horizontal and vertical axes orthogonal to a normal passing through a center axis of the integrator lens. The lighting device according to claim 1, wherein: 5. A condenser lens, wherein the second integrator and the condenser lens are brought into close contact with each other via a liquid having a refractive index substantially equal to the refractive index of the second integrator and the condenser lens. The lighting device according to claim 1, wherein: 6. The lighting device according to claim 1, wherein the first and second integrators are configured as an integrated optical element. 7. The light flux controlling part group, wherein an optical surface having a function of controlling a spatial distribution of a principal ray and an optical surface having a function of controlling a direction are constituted by an integrated optical element. The lighting device according to claim 1.