JPH10186509A - Oblique projection optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oblique projection optical device capable of obtaining an excellent image even at a large oblique projection angle by using a comparatively compact and inexpensive projection lens. SOLUTION: In this oblique projection optical device arranged so that a straight line connecting the center of the diaphragm of a projection lens group 7 to the center of the surface of a screen 3 formed at a fixed angle with the normal of the surface of the screen 3, the surfaces of the screen 3 and an original member 1 are arranged almost in parallel with each other, the projection lens group 7 is composed of at least two co-axial lens groups and the co-axial lens groups are arranged eccentrically to each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an enlargement projection device such as an overhead projector or a liquid crystal projector, and is applicable to a reduction projection device such as an image scanner.

[0002]

2. Description of the Related Art Conventionally, an overhead projector (hereinafter referred to as an OHP) for enlarging and projecting a transparent original such as a transparent film or a liquid crystal panel on a screen in a conference or a lecture or the like while showing a diagram or the like. Is often used. The OHP is usually composed of a projection lens for projecting an image of a transparent original onto a screen and a reflecting mirror for changing the direction of an optical path from a light source to the screen direction.
Since it is configured to be attached to the upper part of the P device main body by the support member, when viewing the image on the screen, those members often hinder the visual field.

Further, in a conventional projection apparatus including a liquid crystal projector, since the projection is performed perpendicularly from the front to the screen, in addition to the above-described problem of obstructing the field of view, the rear projection type In the projector, the bending angle of the reflection mirror is limited, so that there is a problem that the device becomes large and the like.

[0004] In order to solve the above disadvantages, for example, O
In the HP, as shown in FIG. 11, if oblique projection from the OHP 11 onto the screen 3 is possible, the observer 13
Can be prevented from obstructing the visual field of the user. In the figure, reference numeral 12 denotes a user who handles the OHP 11. And FIG.
As shown in FIG. 2, for example, when the width of the screen 3 is 1.2 m and the distance from the screen 3 to the OHP 11 is 1.5 m, if the projection angle α = 20 °, the field of view can be almost prevented even from the rear of the OHP 11. The screen 3 can be observed without any trouble.

Further, as shown in FIG. 13, it is possible to project diagonally upward at a projection angle θ using a similar optical system. Further, as shown in FIG. 14, an optical system capable of oblique projection can be applied to realize a thin rear projection type projector. In FIG. 1, reference numeral 1 denotes a document member such as a liquid crystal panel, and 7 denotes a projection lens group.

As described above, several inventions have conventionally been made in order to enable an image without distortion to be obliquely projected on a screen surface. For example, as described in Japanese Patent Publication No. 4-56297, a lens movable supporting means and a mounting table movable supporting means are provided, and the inclination attitude of the document mounting table and the optical lens can be set to a desired one, and distortion can be reduced. Not to be able to obtain a projected image. In addition, Japanese Patent Application Laid-Open No. H5-241096
As described in Japanese Patent Application Laid-Open Publication No. H10-209, the screen surface is arranged obliquely with respect to the projection lens, and an optical system in which a part of the projection lens is inclined is used to correct the trapezoidal distortion caused thereby. .

[0007]

However, in the configuration as disclosed in Japanese Patent Publication No. 4-56297, it is necessary to use a wide-angle projection lens having a large aperture in order to obtain a projection angle of 20 ° or more. Yes, the cost was high. Further, at this time, as shown in FIG. 15, since the stop 8 is arranged perpendicular to the optical axis of the projection lens group 7, there is a problem that large unevenness in light amount occurs asymmetrically with respect to the center of the image plane of the screen 3. I was holding it.

Further, in the ordinary optical system, when the projection distance is changed, focusing is performed by moving the projection lens in the direction of the optical axis. However, in the oblique projection optical system, as shown in FIG. When the projection lens group 7 and the diaphragm 8 are moved in the direction of the optical axis as shown by the arrows from the place where the light is emitted, light from the light source 6 that is incident obliquely with respect to the optical axis is cut off, and the amount of light shown by oblique lines is reduced. Area B
This causes a problem that light quantity is largely lost and uneven light quantity is caused. Incidentally, in FIG.
Is a condenser lens for condensing light from the light source 6.

In addition, in the configuration as disclosed in Japanese Patent Application Laid-Open No. H5-241096, it is difficult to cope with a large oblique projection angle because remarkable performance degradation occurs by inclining a part of the projection lens. SUMMARY OF THE INVENTION It is an object of the present invention to provide an oblique projection optical device capable of obtaining a good image even at a large oblique projection angle, and to realize the same using a relatively small and low-cost projection lens. It is another object of the present invention to correct a brightness distribution that is generated asymmetrically with respect to the center of the screen surface, and to further correct a change in the brightness distribution caused by shading of light from a light source during focusing.

[0010]

In order to achieve the above object, the present invention has a projection lens system for enlarging or reducing a primary image to a secondary image and projecting the same, and the stop center of the projection lens system. In a diagonal projection optical apparatus in which a straight line connecting the center of the enlarged image plane and the normal of the enlarged image plane is arranged at a predetermined angle, the enlarged image plane and the reduced image plane Are arranged substantially parallel to each other, and the projection lens system is constituted by at least two coaxial lens groups, and the coaxial lens groups are arranged to be eccentric to each other.

At this time, when the primary image is enlarged and projected on the secondary image, the reduced image plane is on the primary image side, and the enlarged image plane is on the secondary image side. Further, when the primary image is reduced and projected onto the secondary image, the enlarged image plane is the primary image side, and the reduced image plane is the secondary image side. In this way, the invention can be applied to both applications.

A vertical direction of a plane including the stop of the projection lens system is inclined with respect to a normal to the reduction-side image plane in a direction approaching a straight line connecting the center of the stop and the center of the reduction-side image plane. Configuration. Alternatively, the stop of the projection lens system may be arranged in a plane substantially perpendicular to a straight line connecting the center of the stop and the center of the reduction-side image plane.

Further, the projection lens system and the stop are configured to change a projection distance by moving integrally in a direction substantially parallel to a straight line connecting the center of the stop and the center of the reduced image plane. I do.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. Normally, in the oblique projection optical device, the trapezoidal distortion is prevented from occurring as shown in FIG.
As shown in FIG. 1A, the respective surfaces of the original member 1 and the screen 3 are arranged substantially in parallel. In the present invention, however, as shown in FIG.
Or by tilting the screen 3 by θ, (a)
The diameter D of the projection lens group 7 is reduced as compared with the case of the above, thereby achieving miniaturization.

As shown in FIG. 2, when the stop 8 is parallel to the document member 1, the angle A at which the light rays entering the stop 8 from the points P and Q at both ends of the document member 1 are angled. Since the image is larger than B, the image projected on the screen 3 is bright at the point P and dark at the point Q.
Therefore, as shown in FIG. 3, the perpendicular direction of the stop 8 with respect to the normal line of the document member 1 is set to the center of the stop 8 and the center of the document member 1 so that the amount of light entering the stop 8 from the point Q increases. The brightness distribution on the surface of the screen 3 is corrected by inclining in the linear direction connecting.

If the stop 8 is tilted until the angles A and B become the same, the luminous flux passing through the peripheral portion of the optical system becomes thicker. In general, it is more difficult to secure the imaging performance in design as in the peripheral part of the optical system, and it is not realistic to incline the angles A and B until the angles become completely the same. Therefore, it is desirable to arrange the aperture 8 at an angle so that a straight line connecting the center of the aperture 8 and the center of the document member 1 intersects the surface of the aperture 8 at an angle close to a right angle.

Further, as shown in FIG. 4, the diaphragm 8 and the projection lens group 7 sandwiching the diaphragm 8 are integrally moved substantially along a straight line connecting the center of the diaphragm 8 and the center of the document member 1 as indicated by an arrow. As a result, it is possible to reduce the area A where the light amount is shaded as shown by the oblique lines, and it is possible to realize an oblique projection optical device in which the light amount loss and the change in the brightness distribution are small.

FIG. 5 is a schematic diagram showing an optical system of one embodiment of the oblique projection optical device of the present invention. As shown in the figure, the image light of the document member 1 is obliquely projected onto the screen 3 by the projection lens group 7 from an oblique direction. As shown in FIG. 6, the projection lens group 7 includes six lenses, and the front and rear lens groups are eccentric with respect to each other with the diaphragm 8 interposed therebetween to perform aberration correction. In addition, since the projection lens group 7 is disposed at an angle, the diameter of the lens can be reduced.

The coordinate axes are the X and Y axes in the plane of the paper and the Z axis perpendicular to the plane of the paper. The X axis is perpendicular to the surface of the screen 3 and the direction from the surface of the screen 3 toward the projection lens group 7 is defined as positive. The origin of the coordinates is set at the center of the aperture 8. Then, an angle between a straight line connecting the origin and the center of the surface of the screen 3 and a perpendicular to the surface of the screen 3 (hereinafter, referred to as an angle)
The oblique projection angle is 32 °. Below, the construction data of this embodiment is shown.

[0020]

<Grp. Of the projection lens group 7> 1> Vertex of first surface: X1 = -59.32 Y1 = 13.8 Rotation angle: θ1 = 6.5 [Symbol of curved surface] [Radius of curvature] [Spacing] [Optical glass name] r1 98.984 LAK31 22.0 r2 465.224 LF5 8.0 r3 95.452 12.0 r4 493.822 PSKS53 10.0 r5 ∞ <Aperture 8> Aperture center ... X = 0.0 Y = 0.0 Rotation angle ... θ = 30.0 Aperture diameter = 35.0

<Grp. Of Projection Lens Group 7> 2> Vertex of first surface: X2 = 9.68 Y2 = 9.79 Rotation angle: θ2 = 4.4 [Symbol of curved surface] [Radius of curvature] [Spacing] [Optical glass name] r6 -106.144 PSKS53 12.5 r7 -71.927 8.5 r8 -56.675 LF5 8.0 r9 -136.513 LAK31 20.0 r10 -84.930

FIG. 7 is a spot diagram obtained by the optical system of this embodiment, and FIG. 8 is a distortion diagram. By the ray trace from the surface of the screen 3,
The evaluation is performed on the surface of the document member 1. These figures show that there is little variation in the distribution of point images, and that projection is performed in a shape that is almost ideal, indicating that the practicality is sufficient.

FIGS. 9 and 10 are schematic diagrams showing the state of the optical system when focusing is performed by changing the projection distance to the screen 3 in this embodiment. The construction data of the projection lens group 7 remains as described above, and the projection distance to the screen 3 is changed by changing the coordinates of the surface of the screen 3 and the surface of the document member 1. Specifically, FIG. 9 shows a case where the distance from the position of the stop 8 to the screen 3 is close to 1.5 m, and FIG.
The case where it is extended to 4 m is shown.

Hereinafter, in the present embodiment, FIG.
9 shows arrangement data of the surface of the screen 3 and the surface of the document member 1 when the state of the optical system as shown in FIGS. 9 and 10 is set. At this time, the angle formed by a straight line connecting the center of the aperture 8 and the center of the surface of the document member 1 with the perpendicular of the surface of the document member 1 is 2
9.4 ° is constant, and the focusing is performed by driving the projection lens group 7 on the straight line. Screen 3
And the rotation angle of the surface of the document member 1 is also constant, and the projection lens group 7 translates parallel to the surface of the document member 1 without tilting, and projects the image on the surface of the screen 3 having the same tilt angle. I have.

(1) When the projection distance is about 2 m (FIG. 5)

(2) When the projection distance is 1.5 m (FIG. 9)

(3) When the projection distance is 2.4 m (FIG. 10)

[0029]

As described above, according to the present invention,
By decentering the coaxial lens groups before and after the diaphragm with respect to the diaphragm, it is possible to provide an oblique projection optical device that can obtain a good image without trapezoidal distortion even at a large oblique projection angle, and This can be achieved using a small, low cost projection lens. The perpendicular direction of the plane including the aperture is inclined so as to be closer to the direction of a straight line connecting the center of the original member surface and the center of the aperture from the direction of the perpendicular to the original member surface. The present invention can provide an oblique projection optical apparatus that corrects the brightness distribution that occurs asymmetrically and reduces unevenness in the amount of light.

Further, by providing a mechanism for moving the projection lens group in a direction along a straight line connecting the center of the surface of the document member and the center of the aperture, a change in brightness distribution due to light source light shading during focusing can be reduced. It is possible to provide an oblique projection optical device which performs correction and has less light amount loss and light amount unevenness.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of miniaturization of a projection lens group.

FIG. 2 is a diagram illustrating an optical system in which an aperture is parallel to a document member.

FIG. 3 is a diagram illustrating an optical system in which an aperture is arranged to be inclined with respect to a document member.

FIG. 4 is a diagram showing the principle of focusing of the oblique projection optical device of the present invention.

FIG. 5 is a schematic diagram showing an optical system of the oblique projection optical device of the present invention.

FIG. 6 is a diagram showing a configuration of a projection lens group of the oblique projection optical device of the present invention.

FIG. 7 is a spot diagram of an optical system of the oblique projection optical device of the present invention.

FIG. 8 is a distortion diagram of the optical system of the oblique projection optical device of the present invention.

FIG. 9 is a schematic diagram showing an example in which the projection distance is changed in the optical system of the oblique projection optical device of the present invention.

FIG. 10 is a schematic diagram showing an example in which the projection distance is changed in the optical system of the oblique projection optical device of the present invention.

FIG. 11 is a schematic diagram showing a state of oblique projection by the OHP.

FIG. 12 is a diagram showing angle conditions for oblique projection.

FIG. 13 is a schematic diagram showing a state of projecting obliquely upward.

FIG. 14 is a schematic diagram showing a configuration of a thin rear projection type projector.

FIG. 15 is an explanatory diagram of the problem of uneven light amount due to the arrangement of the diaphragm.

FIG. 16 is an explanatory diagram of a problem of light amount fluctuation due to arrangement of a projection lens group.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Original member 3 Screen 5 Condensing lens 6 Light source 7 Projection lens group 8 Aperture

──────────────────────────────────────────────────続 き Continued on front page (51) Int.Cl. ⁶ Identification code FI G03B 21/132 G03B 21/132

Claims (4)

[Claims] 1. A projection lens system for enlarging or reducing a primary image to a secondary image and projecting the same, wherein a straight line connecting the center of the stop of the projection lens system and the center of an image plane on the enlargement side is formed on the enlargement side. In the oblique projection optical device arranged at a predetermined angle with respect to the normal of the image plane, the enlarged image plane and the reduced image plane are arranged substantially in parallel with each other, and the projection lens system includes: An oblique projection optical device, comprising at least two coaxial lens groups, wherein the coaxial lens groups are arranged eccentrically with respect to each other. 2. A vertical direction of a plane including the stop of the projection lens system is inclined with respect to a normal to the reduction-side image plane in a direction approaching a straight line connecting the center of the stop and the center of the reduction-side image plane. The oblique projection optical device according to claim 1, wherein: 3. The projection lens system according to claim 1, wherein the stop of the projection lens system is disposed in a plane substantially perpendicular to a straight line connecting the center of the stop and the center of the reduction-side image plane. Oblique projection optical device. 4. The projection lens system and the stop change the projection distance by moving integrally in a direction substantially parallel to a straight line connecting the center of the stop and the center of the reduction-side image plane. The oblique projection optical device according to claim 1, wherein: