JP7133398B2 - Projection optical system and image projection device - Google Patents

Description

The present invention relates to a projection optical system and an image projection apparatus.

The "image projection device" is widely known as a projector device and the like, and various devices have been proposed.
Various types of projection optical systems have been proposed for use in image projection apparatuses to project an image displayed on an image display element onto a projection surface as an enlarged image. An image forming light flux emitted from a refractive optical system arranged on the image display device side is reflected by the reflective optical system to form an image on a projected surface (Patent Reference 1, etc.).

An object of the present invention is to realize a novel projection optical system having a refractive optical system and a reflective optical system.

A projection optical system according to the present invention is a projection optical system for projecting an image displayed on an image display element onto a projection surface as an enlarged image, comprising: a first refractive optical system; A reflecting optical system and a second refractive optical system are arranged on an optical path of an imaging light beam , the reflecting optical system having a concave mirror, and the first refractive optical system having an aperture within the system. and has a function of forming an intermediate image of the image displayed on the image display element on the reduction side of the concave mirror, the second refractive optical system is a lens system having one or more aspherical surfaces, With the optical axis of the refracting optical system as a reference optical axis, the imaging light flux directed from the image display element to the concave mirror is inclined with respect to the reference optical axis, and the concave mirror directs the incident imaging light flux to the reference optical axis. and is incident on the second refractive optical system, and the second refractive optical system aligns its optical axis with the reference optical axis so that the first refractive optical system and the It is located between the concave mirror and has a cutout portion through which the image forming light flux from the first refractive optical system to the concave mirror passes. , the imaging light beam reflected by the concave mirror is transmitted toward the projection surface, and the chief ray whose object point is the position farthest from the reference optical axis in the effective image display area of the image display element is the outermost angle; As a principal ray, the optical path length from the position where the outermost principal ray is incident on the concave mirror to the reference optical axis: DM, the above to the incident surface of the lens arranged on the most expansion side in the second refractive optical system The optical path length from the incident position of the outermost principal ray to the reference optical axis: DR, and the condition:
(1) 0.9≦ DR/DM<3.0
satisfy.

According to this invention, a novel projection optical system having a refractive optical system and a reflective optical system can be realized.

It is a figure for demonstrating Example 1 of a projection optical system. It is a figure for demonstrating Example 2 of a projection optical system. It is a figure for demonstrating Example 3 of a projection optical system. It is a figure for demonstrating Example 4 of a projection optical system. It is a figure for demonstrating Example 5 of a projection optical system. It is a figure for demonstrating Example 6 of a projection optical system. It is a figure for demonstrating Example 7 of a projection optical system. FIG. 12 is a diagram for explaining an eighth embodiment of the projection optical system; FIG. 12 is a diagram for explaining a ninth embodiment of the projection optical system; FIG. 3 is a diagram showing data of Example 1; 4 is a diagram showing aspheric surface data of Example 1. FIG. FIG. 2 is an aberration diagram of Example 1; FIG. 10 is a diagram showing data of Example 2; FIG. 10 is a diagram showing aspheric surface data of Example 2; FIG. 10 is an aberration diagram of Example 2; It is a figure which shows Example 3 data. FIG. 10 is a diagram showing aspheric surface data of Example 3; FIG. 11 is an aberration diagram of Example 3; FIG. 10 is a diagram showing data of Example 4; FIG. 10 is a diagram showing aspheric surface data of Example 4; FIG. 11 is an aberration diagram of Example 4; FIG. 10 is a diagram showing data of Example 5; FIG. 10 is a diagram showing aspheric surface data of Example 5; FIG. 11 is an aberration diagram of Example 5; FIG. 10 is a diagram showing data of Example 6; FIG. 12 is a diagram showing aspheric surface data of Example 6; FIG. 11 is an aberration diagram of Example 6; FIG. 11 shows data of Example 7; FIG. 12 is a diagram showing aspheric surface data of Example 7; FIG. 11 is an aberration diagram of Example 7; FIG. 11 shows data of Example 8; FIG. 10 is a diagram showing aspheric surface data of Example 8; FIG. 11 is an aberration diagram of Example 8; FIG. 11 shows data of Example 9; FIG. 12 is a diagram showing aspheric surface data of Example 9; FIG. 11 is an aberration diagram of Example 9; FIG. 10 is a diagram showing a list of parameter values of conditions in Examples 1 to 9;

Prior to describing specific embodiments, the configuration of the present invention will be described.
The projection optical system of the present invention has the following "basic configuration".
That is, it is a projection optical system for projecting an image displayed on an image display element onto a projection surface as an enlarged image, comprising a first refractive optical system, a reflective optical system, a second A refracting optical system is arranged on the optical path of the imaging light flux, and the "reflecting optical system" has a single concave mirror.
The "first refractive optical system" has an aperture within the system and has a function of forming an intermediate image of the image displayed on the image display device on the reduction side of the concave mirror.
A "second refractive optical system" is a lens system having one or more aspherical surfaces.
Since the second refractive optical system is a lens system, it can be composed of one or more lenses.
The reduction side is the image display element side, and the enlargement side is the projection surface side.
The second refractive optical system uses the optical axis of the first refractive optical system as a reference optical axis. The image forming light flux directed from the image display element toward the concave mirror is inclined with respect to the reference optical axis, and the concave mirror reflects the incident image forming light flux in a direction inclined with respect to the reference optical axis, thereby It is made incident on a two-refractive optical system.
The second refractive optical system is located between the first refractive optical system and the concave mirror with its optical axis aligned with the reference optical axis, and an imaging light flux directed from the first refractive optical system to the concave mirror. The part that passes through is notched. Then, the incident imaging light flux reflected by the concave mirror is transmitted toward the projected surface.
In the effective image display area of the image display device, the principal ray whose object point is the position furthest from the reference optical axis is defined as the outermost principal ray, and the position at which the outermost principal ray enters the concave mirror is measured from the reference optical axis. optical path length to: DM, optical path length from the incident position of the outermost angle chief ray to the incident surface of the lens arranged on the most expansion side in the second refractive optical system to the reference optical axis: DR, ,conditions:
(1) 0.9≦DR/DM<3.0
satisfy.

In this basic configuration, as described above, the optical axis of the first refractive optical system is the "reference optical axis", and the object point is the position furthest from the reference optical axis in the effective image display area of the image display device. Let the ray be the “outermost chief ray”.

The "effective image display area" is an area area where "an image to be projected as an enlarged image by the projection optical system" is displayed on the display surface of the image display device.

The basic configuration satisfies the above condition (1).

In this basic configuration, the height from the reference optical axis of the incident position of the outermost-angle principal ray to the incident surface of the lens on the most magnification side: Y _LB , the outermost-angle principal ray on the mirror surface of the concave mirror of the reflecting optical system The height from the reference optical axis of: Y _MR is the condition:
(2) 0.2< _YLB / _YMR <3.5
can satisfy you. This configuration is referred to as "configuration 2".

In the basic configuration, the maximum height from the reference optical axis to the effective image display area: Yi, the distance on the reference optical axis from the lens surface closest to the image display side to the mirror surface of the concave mirror: OAL, are the conditions:
(3) 5.0<OAL/Yi<30.0
can satisfy you. This configuration is referred to as "configuration 3".

In the basic configuration, the focal length of the first refractive optical system: f _1A , the focal length of the entire system: f, the conditions:
(4) 0.04<f/ _f1A <0.5
can satisfy you. This configuration is referred to as "configuration 4".

In the basic configuration, the maximum height from the reference optical axis to the effective image display area: Yi, the height of the outermost principal ray on the concave mirror from the reference optical axis: Y _MR are the conditions:
(5) 1.5< _YMR /Yi<5.0
can satisfy you. This configuration is referred to as "configuration 5".

In the basic configuration, the distance from the vertex of the lens closest to the enlargement side in the first refractive optical system to the position where the chief ray at each image height intersects the upper ray or the lower ray and is closer to the image display element When defining the image, the intermediate image at the image height closest to the reference optical axis in the effective image display area: TA and the intermediate image position at the farthest image height: TB are the conditions:
(6) 0.10<TB/TA<0.80
can satisfy you. This "configuration 6" is called.

In the basic configuration, the angle of the outermost principal ray reflected by the concave mirror with respect to the reference optical axis: θ is the condition,
(7) 1.5<tan θ<10.0
can satisfy you. This "configuration 7" is called.

In the basic configuration, any two or more of the conditions (2) to (7) can be satisfied. This configuration is referred to as "configuration 8".

An image projection apparatus according to the present invention comprises an image display element and a projection optical system for projecting an image displayed on the image display element onto a projection surface as an enlarged image, wherein the projection optical system has any of the above configurations 1 to 8 is used.
The significance of conditions (1) to (7) will be explained below.
If the parameter of condition (1): DR/DM exceeds the lower limit, the second refractive optical system and the concave mirror are brought close to each other, which is disadvantageous in terms of "aberration correction" such as curvature of field and distortion. If the upper limit is exceeded, the distance between the second refractive optical system and the concave mirror becomes long, which is advantageous in terms of aberration correction, but the second refractive optical system and, in turn, the projection optical system tend to be large.

If the parameter of condition (2): Y _LB /Y _MR exceeds the lower limit, the second refractive optical system and the concave mirror are brought close to each other, which is disadvantageous in terms of "aberration correction" such as curvature of field and distortion. If the upper limit is exceeded, the second refractive optical system moves away from the optical axis, which is advantageous for correcting aberrations, but the second refractive optical system and, in turn, the projection optical system tend to be large.

If the parameter of condition (3): OAL/Yi exceeds the lower limit, the total length of the projection lens with respect to the image size becomes short, making it difficult to correct aberrations such as curvature of field. Further, when the upper limit is exceeded, although it is advantageous for correcting aberrations, the distance from the entrance surface of the first refractive optical system to the concave mirror increases, and the projection optical system tends to be large.

If the parameter of condition (4): f/f _1A exceeds the lower limit, the focal length of the first refractive optical system: f _1A becomes larger than the focal length of the entire system: f, making it difficult to widen the angle. . If the upper limit is exceeded, the focal length of the first refractive optical system: f _1A becomes smaller than the focal length of the entire system: f. Since the intermediate image is formed at , the size of the mirror surface of the concave mirror becomes large, which tends to increase the size of the entire projection optical system.

If the parameter of condition (5): Y _MR /Yi exceeds the lower limit, the size of the concave mirror is small relative to the effective image display area, which is advantageous for miniaturization of the concave mirror, but the power of the concave mirror is weakened. This is disadvantageous in terms of aberration correction and widening of the angle of view. If the upper limit is exceeded, the size of the concave mirror increases, which is advantageous for correcting aberrations, but tends to increase the size of the projection optical system.

When the parameter of condition (6): TB/TA exceeds the lower limit, the intermediate image position on the outermost principal ray is separated from the intermediate image position on the image height close to the reference optical axis. In this case, the luminous flux diameter becomes wider, which is advantageous for aberration correction, but the size of the concave mirror tends to increase. If the upper limit is exceeded, the intermediate image position of the outermost chief ray approaches the intermediate image position of the image height close to the optical axis, which is advantageous for downsizing the concave mirror, but the beam diameter on the concave mirror becomes narrow. This is disadvantageous for aberration correction.

Condition (7) is advantageous for widening the angle of projection optical system, and the range of condition (7) is suitable for the value of the parameter tan θ.
Embodiments of the invention will be described below.
1 to 9 show the essential parts of the image projection apparatus, that is, the configuration of the image display surface and effective image display area of the image display device and the projection optical system.
1 to 9 correspond to Embodiments 1 to 9, which will be described later, in the order shown.
In order to avoid complication, reference numerals are used in common in FIGS.
That is, with respect to the projection optical system, the first refractive optical system is indicated by reference numeral I, the reflective optical system is indicated by reference numeral II, and the second refractive optical system is indicated by reference numeral III. In Examples 1 to 9, the second refractive optical system III is shown as "a configuration with one lens", but is not limited to this, and the second refractive optical system III can be configured as a system of two or more lenses. You may
The optical axis of the second refractive optical system III coincides with the reference optical axis, which is the optical axis of the first refractive optical system. The portion through which it passes is cut off, and the imaging light flux from the first refractive optical system enters the reflecting optical system II through the "notched portion" of the second refractive optical system.
1 to 9, reference numeral 10 denotes an "image display surface" of the image display device, and reference numeral EIm denotes an "effective image display area" of an image displayed on the image display surface 10. FIG.

In the embodiments shown in FIGS. 1 to 9, it is assumed that a "enlarged color image" is projected onto a projection surface (generally a "screen", hereinafter also referred to as a screen), and an image display element. , three liquid crystal panels are assumed.
It goes without saying that the image display element is not limited to a liquid crystal panel, and a DMD (digital mirror device) or the like can be used.
Color component images corresponding to images of three primary colors, for example, R (red), G (green), and B (blue), are individually displayed on three liquid crystal panels assumed as image display elements. , and the transmitted light beams or the reflected light beams become the respective color image lights.
These color image lights are synthesized by a "color synthesizing prism" indicated by reference numeral 11 in the figure, and the synthesized color imaging light flux enters the first refractive optical system I, and when it exits from the first refractive optical system I, After being imaged as an "intermediate image", it enters the "concave mirror" which is the reflecting optical system II, and when reflected, enters the second refractive optical system III and emerges from the second refractive optical system III to become a projection light flux. to form a "color enlarged image" on a screen (not shown).
Nine specific examples are given below.
In each of Examples 1 to 9, the first refractive optical system I has an "aperture" within the system.
In the data of each example, "i" indicates the surface number of the surface (including the diaphragm surface) counted on the enlargement side, with the surface of the image display surface 10 being 0 and the incident surface of the color synthesizing prism 11 being 1, "IMG" indicates the screen surface.
"R" is the radius of curvature of each surface, "D" is the surface spacing, "j" is the optical element number, "Nd" is the d-line refractive index of the material of the optical element, and "vd" is the d-line Abbe number of
Also, the aspherical surface employed in each embodiment is represented by the well-known formula below.

In addition, in each embodiment, the effective image display area EIm set on the image display surface 10 of the image display device has a rectangular shape whose longitudinal direction is the direction orthogonal to the drawing, and the center of the longitudinal direction is the and is in the same plane as the optical axis of the first imaging optical system, ie, the "reference optical axis".

In the vertical direction of the figure, that is, in the "transverse direction", the rectangular effective image display area as a whole is located above the reference optical axis in the figure.
The unit of numerical values in the examples is "mm".
"Example 1"
Data for Example 1 are shown in FIG. Also, FIG. 11 shows the aspheric surface data of Example 1. As shown in FIG.
In the "aspheric surface data", for example, "7.582571E-17" represents "7.582571×10 ⁻¹⁷ " in exponential notation. The same applies to the aspheric surface data in Examples 2 to 9 below.

FIG. 12 shows an aberration diagram of Example 1. FIG.
Aberration diagrams show "spherical aberration", "astigmatism" and "distortion" in order from the left in the upper diagram.

"S" in the astigmatism diagram is sagittal, and "T" is tangential. The figure below the aberration diagram is a diagram of "coma aberration". The notation of the aberration diagrams is the same in the aberration diagrams relating to Examples 2 to 9 given below.
"various characteristics"
Focal length 3.62
NA 0.278
Effective image display area maximum height 13.195
"Example 2"
Data for Example 2 are shown in FIG. FIG. 14 shows the aspheric surface data of Example 2. FIG.
FIG. 15 shows an aberration diagram of Example 2. FIG.
"various characteristics"
Focal length 3.46
NA 0.278
Effective image display area maximum height 13.2
"Example 3"
Data for Example 3 are shown in FIG. FIG. 17 shows the aspheric surface data of Example 3. In FIG.
FIG. 18 shows aberration diagrams of Example 3. FIG.
"various characteristics"
Focal length 2.28
NA 0.250
Effective image display area maximum height 13.20
"Example 4"
Data for Example 4 are shown in FIG. Also, FIG. 20 shows the aspheric surface data of Example 4. As shown in FIG.
FIG. 21 shows an aberration diagram of Example 4. FIG.
"various characteristics"
Focal length 3.70
NA 0.250
Effective image display area maximum height 13.20
"Example 5"
Data for Example 5 are shown in FIG. Also, FIG. 23 shows the aspheric surface data of Example 5. As shown in FIG.
FIG. 24 shows an aberration diagram of Example 5. FIG.
"various characteristics"
Focal length 3.53
NA 0.278
Effective image display area maximum height 13.20
"Example 6"
Data for Example 6 are shown in FIG. Also, FIG. 26 shows the aspheric surface data of Example 6. As shown in FIG.
FIG. 27 shows aberration diagrams of Example 6. FIG.
"various characteristics"
Focal length 3.73
NA 0.278
Effective image display area maximum height 13.20
"Example 7"
Data for Example 7 are shown in FIG. Also, FIG. 29 shows the aspheric surface data of Example 7. As shown in FIG.
FIG. 30 shows an aberration diagram of Example 7. FIG.
"various characteristics"
Focal length 3.96
NA 0.278
Effective image display area maximum height 13.20
"Example 8"
Data for Example 8 are shown in FIG. FIG. 32 shows the aspheric surface data of Example 8. In FIG.
FIG. 33 shows an aberration diagram of Example 8. FIG.
"various characteristics"
Focal length 4.22
NA 0.313
Effective image display area maximum height 13.15
"Example 9"
Data for Example 9 are shown in FIG. Also, FIG. 35 shows the aspheric surface data of Example 9. As shown in FIG.
FIG. 36 shows aberration diagrams of Example 9. FIG.
"various characteristics"
Focal length 3.64
NA 0.227
Effective image display area maximum height 11.7
FIG. 37 shows a list of the values of the parameters of the conditions (1) to (7) described above in Examples 1 to 9. In FIG.

As can be seen from the aberration diagrams, the projection optical systems of Examples 1 to 9 all have good performance, and distortion is particularly well corrected. This is due to the large correction effect of the aspherical surfaces adopted for the lens surfaces of the second refractive optical system III.

Although the preferred embodiments of the invention have been described above, the invention is not limited to the specific embodiments and examples described above, and unless otherwise specified in the above description, Various modifications and alterations are possible within the spirit of the disclosed invention.
The lens that constitutes the second refractive optical system can also have the function of a "cover glass" in the image projection device.

The effects described in the embodiments of the present invention are merely enumerations of preferred effects resulting from the invention, and the effects of the invention are not limited to "those described in the embodiments".

10 Image display surface of image display element
EIm Effective image display area
11 color synthesis prism
I first refractive optical system
II reflective optical system (concave mirror)
III second refractive optical system

Patent application 2014-80509

Claims (9)

A projection optical system for projecting an image displayed on an image display element onto a projection surface as an enlarged image,
A first refractive optical system, a reflective optical system, and a second refractive optical system are arranged in order from the reduction side to the expansion side on the optical path of the imaging light flux ,
The reflective optical system has a single concave mirror,
The first refractive optical system has an aperture in the system and has a function of forming an intermediate image of an image displayed on the image display device on the reduction side of the concave mirror,
the second refractive optical system is a lens system having one or more aspherical surfaces;
With the optical axis of the first refracting optical system as a reference optical axis, the image forming light beam directed from the image display element to the concave mirror is inclined with respect to the reference optical axis, and the concave mirror tilts the incident image forming light beam to the reference optical axis. reflect in a direction tilting with respect to the optical axis and enter the second refractive optical system;
The second refractive optical system is located between the first refractive optical system and the concave mirror with its optical axis aligned with the reference optical axis, and is a coupling from the first refractive optical system to the concave mirror. a portion through which the image light flux passes is cut off, and the image light flux reflected by the concave mirror is transmitted toward the projection surface;
A principal ray whose object point is the position furthest from the reference optical axis in the effective image display area of the image display element is the outermost principal ray,
Optical path length from the position where the outermost-angle principal ray enters the concave mirror to the reference optical axis: DM, the outermost-angle principal ray to the incident surface of the lens arranged on the most expansion side in the second refractive optical system The optical path length from the incident position to the reference optical axis: DR, but the condition:
(1) 0.9≦ DR/DM<3.0
A projection optical system that satisfies The projection optical system according to claim 1,
The optical axis of the first refractive optical system is defined as a reference optical axis, and the principal ray whose object point is the position furthest from the reference optical axis in the effective image display area of the image display device is defined as the outermost principal ray,
Height from the reference optical axis of the incident position of the outermost-angle principal ray to the incident surface of the lens on the most magnification side in the second refractive optical system : Y _LB , the outermost angle on the mirror surface of the concave mirror of the reflective optical system The height of the principal ray from the reference optical axis: Y _MR is the condition:
(2) 0.2< _YLB / _YMR <3.5
A projection optical system that satisfies The projection optical system according to claim 1,
The optical axis of the first refractive optical system is defined as a reference optical axis, and the principal ray whose object point is the position furthest from the reference optical axis in the effective image display area of the image display device is defined as the outermost principal ray,
The maximum height from the reference optical axis to the effective image display area: Yi, the distance on the reference optical axis from the lens surface closest to the image display side to the mirror surface of the concave mirror: OAL, are the conditions:
(3) 5.0<OAL/Yi<30.0
A projection optical system that satisfies The projection optical system according to claim 1,
The focal length of the first refractive optical system: f _1A , the focal length of the entire system: f, the conditions:
(4) 0.04<f/ _f1A <0.5
A projection optical system that satisfies The projection optical system according to claim 1,
The optical axis of the first refractive optical system is defined as a reference optical axis, and the principal ray whose object point is the position furthest from the reference optical axis in the effective image display area of the image display device is defined as the outermost principal ray,
The maximum height from the reference optical axis to the effective image display area: Yi, the height of the outermost principal ray in the concave mirror from the reference optical axis: Y _MR are the conditions:
(5) 1.5< _YMR /Yi<5.0
A projection optical system that satisfies The projection optical system according to claim 1,
The optical axis of the first refracting optical system is a reference optical axis, the chief ray having an object point at a position farthest from the reference optical axis in the effective image display area of the image display element is the outermost chief ray, and the first When the intermediate image is defined by the distance from the apex of the lens closest to the enlargement side in the refractive optical system to the position where the chief ray and the upper ray or the lower ray at each image height intersect, and whichever is closer to the image display device ,
An intermediate image at an image height closest to the reference optical axis in the effective image display area: TA and an intermediate image position at the farthest image height: TB are the conditions:
(6) 0.10<TB/TA<0.80
A projection optical system that satisfies The projection optical system according to claim 1,
The optical axis of the first refractive optical system is defined as a reference optical axis, and the principal ray whose object point is the position furthest from the reference optical axis in the effective image display area of the image display device is defined as the outermost principal ray,
The angle of the outermost principal ray reflected by the concave mirror with respect to the reference optical axis: θ is the condition:
(7) 1.5<tan θ<10.0
A projection optical system that satisfies The projection optical system according to claim 1,
Height from the reference optical axis of the incident position of the outermost-angle principal ray to the incident surface of the lens on the most magnification side in the second refractive optical system: Y _LB , the outermost angle on the mirror surface of the concave mirror of the reflective optical system Height of the principal ray from the reference optical axis: Y _MR Maximum height from the reference optical axis to the effective image display area: Yi Reference from the lens surface closest to the image display surface to the mirror surface of the concave mirror Distance on the optical axis: OAL, focal length of the first refractive optical system: f _1A , focal length of the entire system: f, maximum height from the reference optical axis to the effective image display area: Yi, in the concave mirror The height of the outermost principal ray from the reference optical axis: Y _MR , the intermediate image at the image height closest to the reference optical axis in the effective image display area: TA, and the intermediate image position at the farthest image height: TB , the angle of the outermost principal ray reflected by the concave mirror with respect to the reference optical axis: θ is the condition:
(2) 0.2< _YLB / _YMR <3.5
(3) 5.0<OAL/Yi<30.0
(4) 0.04<f/ _f1A <0.5
(5) 1.5< _YMR /Yi< 5.0
(6) 0.10<TB/TA<0.80
(7) 1.5<tan θ<10.0
A projection optical system that satisfies any two or more of an image display element; and a projection optical system for projecting an image displayed on the image display element onto a projection surface as an enlarged image,
An image projection apparatus comprising the projection optical system according to any one of claims 1 to 8 as the projection optical system.

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