JP2000098488A - Illumination optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an illumination optical device using a multilens array capable of shortening optical path length, being miniaturized and condensing light with high efficiency. SOLUTION: This illumination optical device is equipped with a light source lamp 1, a first lens array 11 constituted of a plurality of condensing lenses and condensing emitted light for a light source so that a plurality of images may be formed, a second lens array 12 constituted of plural condensing lenses put near the plurality of images formed by the lens array 11, and a condensing lens system consisting of plural condensing lenses 21, 22 and 23 superposing and condensing the plurality of images formed by the lens array 11 and transmitted through the lens array 12 in similar shape on the same position. The device is provided with at least one condensing lens 23 possessing a surface having such negative power that parallel beams made incident on the lenses 21, 22 and 23 constituting the condensing lens system are diverged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illumination optical device, and more particularly to an illumination optical device that can be used for a projector device using a spatial light modulator.

[0002]

2. Description of the Related Art In a projector device, when a signal of the same level is input to the entire screen, it is required that the screen luminance distribution is constant even on the screen. Such uniformity of the brightness on the screen is called high screen uniformity, and is one of the important items in achieving high quality image quality.

Generally, a light source generally has uneven brightness at a light emitting portion. Now, a projector device using a spatial light modulator that forms light from a light emitting portion of a light source on a spatial light modulator that inputs an image signal, and forms an image of the spatial light modulator on a screen by a projection lens. Consider a configuration like When such an optical system is used, uneven brightness of the light emitting portion is displayed on the screen as it is with the configuration as it is, and the screen uniformity cannot be increased.

[0004] In order to improve this, it is necessary to provide a configuration of an optical element capable of uniformly illuminating the spatial light modulation element in an optical system (referred to as an illumination optical system) from the light source to the spatial light modulation element. . Such an optical element is generally called a light integrator. Two types of light integrators are generally known, one using a multi-lens array (hereinafter abbreviated as MLA) or a fly-eye lens and the other using a transparent rod. The present invention relates to an apparatus using MLA. The MLA aims to uniformly illuminate by spatially arranging a plurality of small lenses and superposing light from these lenses on a spatial light modulator.

FIG. 5 is a schematic view of an MLA element. ML
A is a combination of a plurality of lenses as shown in the figure. In this figure, one surface has a curvature and the other surface is shown as a plane, but it is also possible to realize a lens having a convex lens shape on both surfaces. The shape of each lens is rectangular in the drawing, but is not necessarily limited to this. 6 and 7 show a conventional illumination optical system using the MLA. Hereinafter, the operation of the illumination optical system using the conventional MLA will be described.

In the MLA illumination optical system, an image of each lens of the first MLA 11 is superimposed and projected on an object such as the spatial light modulator 31. At the stage of the first MLA 11, even if there is spatially uneven brightness, uniformity can be improved by dividing and overlapping.
Since the image of each lens in the first MLA 11 is projected onto the spatial light modulator, the first ML is used for efficient illumination.
Each lens of A11 needs to have a shape similar to or similar to the spatial light modulation element 31. 1st MLA11
In order to share the same lens system as the condenser lenses 21 and 22 when projecting the plurality of lenses included in the first MLA 11 onto the spatial light modulator 31, the lenses included in the first MLA 11 are generally formed in the same shape.

[0007] The second MLA 12 is located near the focal point of the first MLA 11. The second MLA 12 is installed so as to correspond to each of the light beams split by the plurality of lenses of the first MLA 11. The second MLA 12 is the first MLA 1
It is not always necessary to have a similar shape to the spatial light modulator 31 as in FIG. Condensing lens systems 21 and 22 are provided between the second MLA 12 and a spatial light modulation element 31 such as a liquid crystal element. As shown in FIG. 6, one lens 21 is provided in the condenser lens system.
Is used, the light incident on the spatial light modulator 31 is not telecentric. Many projectors require that the light incident on the spatial light modulation element 31 be telecentric. Therefore, as shown in FIG. 7, a condensing lens 2 (22) called a field lens is placed immediately before the panel, and the principal ray is By bending, a telecentric optical system is realized.

Here, the telecentric system will be briefly described. A telecentric system is an optical system in which either the entrance pupil or the exit pupil is located at an infinite circle. As shown in FIG. 11, when the aperture stop 2 is placed at the rear focal point of the image space or at the front focal point 6 of the object space, all the principal rays (light rays passing through the center of the aperture stop) correspond to each.
Reference numeral 7 denotes an object space or an image space which is parallel to the optical axis 8. As a result, in a telecentric system, the influence of an error in the position of the object plane or image plane on an error in the size of an image to be photographed or measured is reduced. Even in a projector device using a spatial light modulator such as a liquid crystal element, it is necessary to use an optical device to prevent image distortion, blur, uneven brightness, uneven color, etc. due to errors in the position of the spatial light modulator or the angle of light rays. The system must be telecentric.

When three spatial light modulators are used to process a color image, each of the spatial light modulators is illuminated with the three primary colors of light. In general, as shown in FIG. 8, light is separated by wavelength by putting color separation mirrors 41 and 42 in the condenser lens systems 21 to 24. The distance from the lamp 1 to the spatial light modulators 31 to 33 can be the same for the two spatial light modulators 31 and 32, but the other color is condensed using the relay lens 81.

In a projector using a spatial light modulator that uses polarized light such as a liquid crystal element and a light source that emits non-polarized light such as a discharge lamp, a polarizing beam splitter and a wave plate are placed near the second MLA 12 so as to reduce the polarization component. It is common to use a changing polarization conversion. In this case, the optical system of the MLA is almost the same.

The illumination optical system using the conventional MLA has been described above. The problems of this method are described below. 6 to 8
In any case, the distance from the second MLA 12 to the spatial light modulators 31 to 33 is long. This is convenient when three spatial light modulators are used and the color separation mirrors 41 and 42 are arranged as shown in FIG. However, FIGS. 6 and 7
When only one spatial light modulation element 31 shown in FIG.
There is a problem that the projector device becomes large.

When three spatial light modulators are used, it is considered that color separation is to be performed by a telecentric optical system. In the example of FIG. 8, since the color separation portion is not a telecentric optical system, there is a possibility that brightness unevenness and color unevenness may occur on the spatial light modulator when performing color separation. Since there is a color separation mirror 1 (41) and a color separation mirror 2 (42) between the condenser lens 1 (21) and the condenser lens 2 (22) in FIG. 8, color separation is not performed by telecentricity.

FIG. 9 shows a problem occurring when color separation is performed in a place other than the telecentric optical system. Light beams incident on different positions of the spatial light modulation element 31 have different incident angles on the color separation mirror 41. In the example of FIG.
The angles of incidence on the color separation mirror 41 are different between the upper and lower parts of the figure. In an optical element utilizing light interference, such as the color separation mirror 41, the transmission and reflection characteristics change depending on the angle of incidence on the element. Therefore, in FIG. 9, the spatial light modulator 3
The wavelength of the light reaching the position 1 may differ depending on the location, and color unevenness may occur on the screen. To perform color separation and synthesis by telecentricity, as shown in FIG.
It is necessary to increase the distance to the spatial light modulator 31. In the case of such an optical system, there is a disadvantage that the optical path length of the MLA illumination optical system increases and the size of the projector device further increases.

As described above, the conventional MLA illumination optical system has a drawback that the optical path length increases when the telecentric optical system is maintained. This drawback has led to an increase in the size of the optics.

[0015]

As described above, in the conventional MLA illumination optical apparatus, if the telecentric optical system is to be maintained to prevent color and luminance unevenness, the optical path length becomes longer and the apparatus becomes larger. was there.

The present invention solves this point in a relatively simple manner, and can reduce the optical path length, and is compact and illuminates using a multi-lens array (MLA) capable of highly efficient light collection. An object is to realize an optical device.

[0017]

In order to achieve the above object, the present invention is directed to a first embodiment comprising a light source and a plurality of condenser lenses, which collects light emitted from the light source and forms a plurality of images.
A second lens array composed of a plurality of condenser lenses placed near a plurality of images formed by the first lens array, and the second lens array formed by the first lens array. A converging lens system comprising a plurality of converging lenses that converge and converge a plurality of images transmitted through the lens array at the same position in a similar shape. At least one condenser lens having a surface having a negative power that diverges parallel light incident on the plurality of condenser lenses is provided.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an illumination optical device according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a schematic view of an embodiment of the illumination optical device of the present invention. In FIG. 1, 11 is the first MLA, 12 is the second MLA, 2
1 is a condenser lens 1, 22 is a condenser lens 2, 23 is a condenser lens 3, and 31 is a spatial modulation element. In the present embodiment, the condenser lens 21 of the illumination optical system using the MLAs 11 and 12
The use of a concave lens among the lenses 23 to 23 aims to shorten the optical path length of the illumination optical system. In the illumination optical system using the conventional MLAs 11 and 12 shown in FIG.
A number of convex lenses were used. On the other hand, in the present embodiment, the power of refracting the light beam of the first convex lens (condensing lens 1) 21 is increased, and the concave lens (condensing lens 3) 23 is inserted into the second convex lens (condensing lens 3). The convex lens of the eye (condensing lens 2) 22 converges on the object.

The principle of the present invention will be described with reference to FIG.
In the present invention, it is considered that the spatial light modulator 31 is illuminated with light at the same angle and the same size as in the conventional method. MLA1
In the cases of 1 and 12, it is only necessary to consider the light beam emitted from the element at the end and the light beam emitted from the center as a representative.

In the conventional illumination optical system shown in FIG. 4, illumination is performed by using two convex lenses, that is, two lens elements (condensing lenses 1 and 2) 21 and 22 having positive power. In contrast, in the present invention, lens elements 21, 22, and 23 having three powers of + and + are used.
Moreover, in order to illuminate at the same angle and the same size as in the case of FIG.
The positive power of 1, 22 is made stronger than the positive power of the two convex lenses 21, 22 of the conventional method shown in FIG. Using the lens 23 having a negative power,
The spatial light modulator 31 is illuminated at the same size and at the same angle. At this time, since the light beam is bent halfway, it can be understood that a short distance is sufficient. Thereby, the present invention can achieve a short optical path,
The illumination optical device and the projector device and the like using the same can be made small.

FIG. 2 is a schematic diagram of another embodiment of the present invention. In FIG. 2, 11 is the first MLA, 12 is the second MLA, 2
1 is a condenser lens 1, 25 is a condenser lens 2, and 31 is a spatial modulation element. In the present invention, a method is to configure an MLA illumination optical system including a condenser lens system using a lens that performs refraction such that a parallel light beam spreads, that is, a lens having negative power. Therefore, in the embodiment of FIG. 1 described above, three lenses are used. However, as shown in FIG. 2, in the present embodiment, the condensing lens 2 having one surface having a negative power and one surface having a positive power. (25) is used. In this case, the number of the condenser lenses 21 and 25 is two, but the power is +
The one having the arrangement of-+ can be realized. In this case, as long as the condenser lens 2 (25) has a surface having negative power, it is not necessarily required to be a concave lens.

FIG. 3 is a schematic diagram of still another embodiment of the present invention. In the present embodiment, power is divided into a plurality of lenses for aberration correction. In FIG. 3, 11 is the first MLA, 12 is the second MLA, 21
Is a condenser lens 1, 22 is a condenser lens 2, 25 is a condenser lens 3, and 31 is a spatial modulation element. In FIG. 3, three condenser lenses are used, and a condenser lens 1 (21) and a condenser lens 2 (2
A condenser lens 3 (25) having a surface having a negative power is inserted between 2) and 2). In the case where the present invention is realized with a small number of surfaces as in the embodiment of FIG. 2 described above, the angle at which the light beam is bent tends to be strong, thereby increasing the optical aberration. In the embodiment of FIG. 3, in order to correct this, aberrations can be corrected or reduced by increasing the number of lenses and the number of refraction surfaces of light rays.

As described above, according to the present invention, the optical path length can be shortened. As a result, the size of devices and devices can be reduced. Reducing the size of equipment and devices leads to a reduction in manufacturing costs and materials used. Further, by using a lens having a negative power, the Petzval sum can be reduced. This is synonymous with the ability to reduce the field distortion, and enables more efficient light collection. When a projector or the like is configured as a device, the arrangement of the illumination optical system is limited by other components such as an electric circuit. In an illumination optical system using the MLA, if the illumination optical path length can be adjusted when the illumination optical system is actually arranged, the entire arrangement can be realized very easily. In the present invention, by using a lens of negative power,
When the illumination optical system is incorporated in the device, the device can be efficiently arranged with a minimum volume.

[0024]

As described above, the first aspect of the present invention comprises a light source and a plurality of condenser lenses, and forms a plurality of images by condensing light emitted from the light source and forming a plurality of images. A second lens array including a lens array and a plurality of condenser lenses disposed near a plurality of images formed by the first lens array;
And a condensing lens system comprising a plurality of condensing lenses formed by the first lens array and transmitted through the second lens array and condensed by superimposing and converging a plurality of images in a similar shape at the same position. The illumination optical apparatus includes at least one condensing lens having a surface having a negative power so as to diverge incident parallel light among a plurality of condensing lenses constituting a condensing lens system. It is characterized by. As a result, the optical path length can be shortened, the devices and devices can be reduced, and further, the use of materials and the manufacturing cost can be reduced.

According to a second aspect of the present invention, the surface of the condenser lens having the negative power is located between the surfaces of the condenser lens having the positive power for condensing the parallel light. I do.
As a result, the optical path length can be shortened, and the field distortion can be reduced.

According to a third aspect of the present invention, among the plurality of condenser lenses constituting the condenser lens system, one surface is a surface having a positive power and the other surface is a surface having a negative power. It is characterized by including at least one certain condenser lens. Thus, the optical path length can be reduced with a small number of lenses.

[Brief description of the drawings]

FIG. 1 is a schematic view of an embodiment of an illumination optical device according to the present invention.

FIG. 2 is a schematic view of another embodiment of the illumination optical device of the present invention.

FIG. 3 is a schematic diagram of still another embodiment of the illumination optical device of the present invention.

FIG. 4 is a schematic view of a conventional example of an illumination optical device.

FIG. 5 is a schematic diagram of an MLA element.

FIG. 6 is a schematic diagram of a conventional example of an illumination optical system using an MLA.

FIG. 7 is a schematic diagram of a conventional example of an illumination optical system using an MLA.

FIG. 8 is a schematic diagram of a conventional example of an illumination optical system using an MLA and three spatial modulation elements.

FIG. 9 is an explanatory diagram showing the occurrence of a problem when performing color separation in a place other than the telecentric optical system.

FIG. 10 is a schematic view of a conventional example of an illumination optical system in which a distance between a lens of a condenser lens system and a spatial light modulator is increased.

FIG. 11 is an explanatory diagram of a telecentric optical system.

[Explanation of symbols]

1 lamp, 2 aperture stop, 3 lens, 4 object, 5
... image, 6 ... focal point, 7 ... principal ray, 8 ... optical axis, 11 ... 1M
LA, 12 ... second MLA, 21 ... condenser lenses 1, 22,
25 condensing lenses 2, 23 condensing lenses 3, 24 condensing lenses 4, 31 spatial modulators 1, 32 spatial modulators 2, 33 spatial modulators 3, 41 color separation mirrors 1, 4
2. Color separation mirror 2, 51 Reflection mirror 1, 52 Reflection mirror 2, 53 Reflection mirror 3, 61 Color synthesis prism 71 Projection lens 81 Relay lens

Claims (3)

[Claims] A first light source configured to collect light emitted from the light source and form a plurality of images;
A second lens array composed of a plurality of condenser lenses placed near a plurality of images formed by the first lens array, and the second lens array formed by the first lens array. A converging lens system comprising a plurality of converging lenses that converge and converge a plurality of images transmitted through the lens array in a similar shape at the same position. An illumination optical device, comprising: at least one condenser lens having a surface having a negative power such that parallel light incident on the plurality of condenser lenses is diverged. 2. The condenser lens according to claim 1, wherein the surface of the condenser lens having a negative power is located between the surfaces of the condenser lens having a positive power for condensing the parallel light. Illumination optics. 3. At least one of a plurality of condenser lenses constituting the condenser lens system, one of which has a surface having a positive power and the other has a surface having a negative power. The illumination optical device according to claim 1, comprising: