JP2016099439A - Projection optical system and image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection optical system that has sufficiently reduced a projection distance, achieves high luminance, and provides high performance with a reduced size.SOLUTION: A projection optical system includes a dioptric system RR that comprises a plurality of optical elements including an aperture diaphragm AD and a plurality of lenses, and a reflection optical system RL that includes a folded plane mirror M1 and a free-form surface concave mirror M2 sequentially arranged between the dioptric system RR and a screen SC. The projection optical system forms one intermediate image between an image display element and the reflection optical system RL, and includes an optical axis A that is shared by the plurality of axially-symmetric lenses in the dioptric system RR; when an axis in a surface including a light beam emitted from the center of the image display element and passing through the center of the aperture diaphragm AD, the axis being orthogonal to the optical axis A is Y-axis, a part of the optical elements B in the dioptric system RR is eccentric in a direction parallel to the Y-axis; an image forming part Lv of the image display element intersects with the optical axis A.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image display device such as a so-called projector that displays an enlarged image on a screen, and more particularly to a projection optical system for enlarging and projecting an image displayed on an image display element on a screen. .

In recent years, a projection-type image display device called a projector or the like has been widely used. In general, this type of projection type image display device projects an enlarged image of a display image of an image display element called a light valve (light valve) such as a DMD (Digital Micromirror Device) or a liquid crystal display panel. An image is displayed on the screen by an optical system.
The DMD used as an image display element is a device that has a large number of micromirrors and can electronically control the angles of these micromirrors individually within a predetermined range. For example, when the angle of one micromirror is −12 °, the reflected light of the illumination light from the micromirror is incident on the projection optical system, and when the angle is + 12 °, the reflected light of the illumination light is projected into the projection optical system. If the angle at which the illumination light enters the DMD is set so that it does not enter the DMD, a digital image can be formed on the display screen of the DMD by controlling the tilt angle of each micromirror of the DMD.
Recently, in this type of projection type image display device, a front projection type projector with an ultra-short projection distance that can display a large screen on a screen set at a close distance by shortening the projection distance compared to the conventional one. The demand for is increasing.

A projection optical system used for a projection image display device with an ultra-short projection distance, such as a front projection projector with an ultra-short projection distance, deflects a projection optical path while correcting distortion of an image using a curved mirror. In some cases, the distance between the image display element and the screen is shortened. This method using a curved mirror has the potential to achieve projection from a very close distance even if it is small.
As described above, for example, Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2007-79524) and Patent Document 2 (Japanese Unexamined Patent Application Publication No. 2011) disclose a projection-type image display device that uses a curved mirror to achieve a small and ultra-short projection distance. No. 242606), Patent Document 3 (Japanese Patent Laid-Open No. 2012-108267), Patent Document 4 (Japanese Patent Laid-Open No. 2009-216883), and the like.
That is, these Patent Document 1, Patent Document 2, Patent Document 3, and Patent Document 4 all show the configuration of a projection-type image display device that combines a refractive optical system and a curved mirror. A short projection distance can be realized.

  Incidentally, in this type of projection-type image display apparatus, that is, an ultra-short projection projector, in recent years, miniaturization and cost reduction have been demanded. In general, a projector using a reflective optical system must adopt a configuration in which the image display element is decentered from the optical axis in order to avoid interference between the light beam and the housing. When the image display element is decentered from the optical axis in this way, the dimension in the thickness direction of the projector is increased by that amount. Further, it is impossible to share an illumination system for illuminating the image display element between a projector using only a refractive optical system and a projector using both a refractive optical system and a reflective optical system. For this reason, these projectors must be individually developed, which contributes to an increase in cost.

However, in the descriptions of Patent Literature 1 and Patent Literature 2, there is no particular mention of thinning and common use of an illumination system, and it does not sufficiently respond to the market demand as described above.
Patent Document 3 discloses a configuration in which an intermediate image is formed in the refractive optical system to reduce the amount of eccentricity of the image display element. If an intermediate image is simply formed, the size in the direction of the optical axis increases, so that it is not possible to appropriately meet the demand for miniaturization.
Patent Document 4 discloses a method of using a plurality of free-form surfaces and a method of decentering a large number of lenses. However, simply applying these methods may increase manufacturing error sensitivity. Because it is, it is not desirable.
The present invention has been made in view of the above-described circumstances, and it is an object of the present invention to provide a compact and high-performance projection optical system that can sufficiently shorten the projection distance and increase the brightness. Yes.

In order to achieve the above-described object, the projection optical system according to the present invention provides
A projection optical system for enlarging and projecting an image displayed on an image display element on a screen,
The projection optical system includes:
A plurality of optical elements including a diaphragm and a plurality of lenses, and a refractive optical system for enlarging an image displayed on the image display element;
A reflective optical system having at least one reflective optical element disposed between the refractive optical system and the screen;
Forming an intermediate image between the image display element and the reflective optical system;
An axis shared by a plurality of axially symmetric lenses in the refractive optical system is defined as an optical axis A, and an in-plane axis including the optical axis A and including a light beam emitted from the center of the image display element and passing through the center of the stop. And when an axis orthogonal to the optical axis A is a Y axis, a part of the optical elements B of the refractive optical system is decentered in a direction parallel to the Y axis,
The image forming portion of the image display element and the optical axis A intersect each other.

According to the present invention,
In a projection optical system that enlarges and projects an image displayed on an image display element on a screen,
The projection optical system includes:
A plurality of optical elements including a diaphragm and a plurality of lenses, and a refractive optical system for enlarging an image displayed on the image display element;
A reflective optical system having at least one reflective optical element disposed between the refractive optical system and the screen;
Forming an intermediate image between the image display element and the reflective optical system;
An axis shared by a plurality of axially symmetric lenses in the refractive optical system is defined as an optical axis A, and an in-plane axis including the optical axis A and including a light beam emitted from the center of the image display element and passing through the center of the stop. And when an axis orthogonal to the optical axis A is a Y axis, a part of the optical elements B of the refractive optical system is decentered in a direction parallel to the Y axis,
By crossing the image forming portion of the image display element and the optical axis A,
The projection distance can be sufficiently shortened and the brightness can be increased, and a compact and high-performance projection optical system can be obtained.

1 schematically shows the main configuration of the entire projection optical system in an image display apparatus according to Example 1, which is the first embodiment of the present invention, including the optical axis and the long side of the display screen of the image display element is vertical. It is sectional drawing shown along the cross section which crosses. FIG. 2 is a cross-sectional view showing in more detail a portion of a lens system that is mainly a refractive optical system of the projection optical system of FIG. 1 and its focusing operation. It is a schematic diagram which shows typically the form of the image formation part of the image display element in the projection optical system of FIG. 1, and the positional relationship with respect to the optical axis. It is a schematic diagram for demonstrating the relationship of a paraxial image surface, an intermediate image, an optical axis, etc. in the projection optical system of FIG. It is a schematic diagram for demonstrating the relationship between the paraxial image surface in the long distance (100 inches) of the projection optical system of FIG. 1, and the intersection of a chief ray. It is a schematic diagram for demonstrating the relationship between the paraxial image surface in the intermediate distance (80 inches) of the projection optical system of FIG. 1, and the intersection of a chief ray. It is a schematic diagram for demonstrating the relationship between the paraxial image surface in the short distance (60 inches) of the projection optical system of FIG. 1, and the intersection of a chief ray. It is a schematic diagram which shows the spot position of wavelength 550nm on the screen in the long distance (100 inches) of the projection optical system of FIG. It is a schematic diagram which shows the spot position of wavelength 550nm on the screen in the intermediate distance (80 inches) of the projection optical system of FIG. It is a schematic diagram which shows the spot position of wavelength 550nm on the screen in the short distance (60 inches) of the projection optical system of FIG. 2 is a spot diagram showing imaging characteristics of wavelengths 625 nm (red), 550 nm (green) and 425 nm (blue) on a screen at a long distance (100 inches) of the projection optical system of FIG. 1. 2 is a spot diagram showing imaging characteristics of wavelengths 625 nm (red), 550 nm (green) and 425 nm (blue) on a screen at an intermediate distance (80 inches) of the projection optical system of FIG. 1. 2 is a spot diagram showing imaging characteristics of wavelengths 625 nm (red), 550 nm (green) and 425 nm (blue) on a screen at a short distance (60 inches) of the projection optical system of FIG. 1. It is a figure which shows the angle of view corresponding to F1-F13 in the spot diagrams of FIGS. The schematic main configuration of the entire projection optical system in the image display apparatus according to Example 2 which is the second embodiment of the present invention includes the optical axis and the long side of the display screen of the image display element is vertical. It is sectional drawing shown along the cross section which crosses. It is sectional drawing which shows the part of the lens system which is mainly a refractive optical system of the projection optical system of FIG. 15, and its focusing operation | movement in detail. It is a schematic diagram for demonstrating the relationship between the paraxial image surface in the long distance (100 inches) of the projection optical system of FIG. 15, and the intersection of a chief ray. It is a schematic diagram for demonstrating the relationship between the paraxial image surface in the intermediate distance (80 inches) of the projection optical system of FIG. 15, and the intersection of a chief ray. It is a schematic diagram for demonstrating the relationship between the paraxial image surface in the short distance (60 inches) of the projection optical system of FIG. 15, and the intersection of a chief ray. It is a schematic diagram which shows the spot position of wavelength 550nm on the screen in the long distance (100 inches) of the projection optical system of FIG. It is a schematic diagram which shows the spot position of wavelength 550nm on the screen in the intermediate distance (80 inches) of the projection optical system of FIG. It is a schematic diagram which shows the spot position of wavelength 550nm on the screen in the short distance (60 inches) of the projection optical system of FIG. FIG. 16 is a spot diagram showing imaging characteristics of a wavelength of 625 nm (red), 550 nm (green), and 425 nm (blue) on a screen at a long distance (100 inches) of the projection optical system of FIG. 15. 16 is a spot diagram showing imaging characteristics of wavelengths 625 nm (red), 550 nm (green), and 425 nm (blue) on a screen at an intermediate distance (80 inches) of the projection optical system of FIG. 15. 16 is a spot diagram showing imaging characteristics of wavelengths 625 nm (red), 550 nm (green), and 425 nm (blue) on a screen at a short distance (60 inches) of the projection optical system of FIG. 15.

Hereinafter, based on an embodiment of the present invention, a projection optical system according to the present invention will be described in detail with reference to the drawings. Before describing specific embodiments, first, the principle of the present invention will be described.
A projection optical system according to the present invention is a projection optical system for enlarging and projecting an image displayed on an image display element on a screen, and constitutes a projection-type image display device generally called a projector. The projection optical system of the present invention is
A plurality of optical elements including a diaphragm and a plurality of lenses, and a refractive optical system for enlarging an image displayed on the image display element;
A reflective optical system having at least one reflective optical element disposed between the refractive optical system and the screen;
Forming an intermediate image between the image display element and the reflective optical system;
An axis shared by a plurality of axially symmetric lenses in the refractive optical system is defined as an optical axis A, and an in-plane axis including the optical axis A and including a light beam emitted from the center of the image display element and passing through the center of the stop. And when an axis orthogonal to the optical axis A is a Y axis, a part of the optical elements B of the refractive optical system is decentered in a direction parallel to the Y axis,
It is desirable that the image forming portion of the image display element and the optical axis A intersect (corresponding to claim 1). Here, the decentering means that the optical element B does not share the optical axis A with the optical axis.

By decentering some of the optical elements B of the refractive optical system, even if the image display element intersects the optical axis A, the light beam reflected from the mirror of the reflective optical system and the refractive optical system or Interference with the folding mirror or the like can be avoided. Further, by crossing the image display element with the optical axis A, it is possible to reduce the thickness in the Y-axis direction of the housing of a projection-type image display device such as a projector. Here, the optical element B is any of a single lens, a cemented lens, and a lens group that moves together in the refractive optical system.
In general, a front projection type projector using a refractive optical system is often designed by crossing an optical axis with an image display element. However, in a configuration using a reflective optical system such as a mirror, as described above, Since interference between the light beam and the lens is unavoidable, the image display element and the optical axis are arranged so as not to cross each other. For this reason, it has been difficult to share the illumination system. On the other hand, in the present invention, by decentering some of the optical elements B, interference between the light beam and the lens can be avoided even if the image display element and the optical axis cross each other. This makes it possible to share the illumination system with the front projection type projector using the projector.

Furthermore, it is desirable that the optical element B has a negative power (corresponding to claim 2). By decentering the negative power optical element in this way, it is possible to suppress decentration aberrations that affect the optical performance, and thus it is possible to reduce the size of the lens and mirror.
Furthermore, it is desirable that the optical element B is disposed closer to the reflective optical element than the stop (corresponding to claim 3). Thus, by arranging the optical element B closer to the reflective optical element than the stop, it is possible to suppress the occurrence of decentration aberrations and to reduce the size of the lens and mirror.
More preferably, the optical element B may be a spherical lens (corresponding to claim 4). By decentering the spherical lens in this way, it is possible to suppress the occurrence of advanced decentration aberrations.
Desirably, the reflective optical element may be a concave mirror having a free-form surface (corresponding to claim 5). In this way, it is possible to efficiently suppress decentration aberrations such as trapezoidal distortion that are generated by decentering the optical element B, and it is possible to reduce the size of a projection-type image display device such as a projector. Especially in projectors with ultra short projection distances, large trapezoidal distortion occurs due to lens decentration, and rotationally symmetric optical elements often cannot be corrected, but it is effective by using a free-form surface mirror. It becomes possible to correct.

Furthermore, it is desirable that the following conditional expression [1] is satisfied, where TR is the distance from the intersection of the concave mirror and the optical axis A to the screen / screen horizontal width (corresponding to claim 6).
Conditional expression:
[1] TR <0.30
By satisfying conditional expression [1] in this way, it is possible to provide a small projection optical system with a small projection space.
Furthermore, it is desirable that the optical axis A is orthogonal to the image display element (corresponding to claim 7). As described above, since the optical axis A and the image display element are orthogonal to each other, the occurrence of decentration aberration can be suppressed.
Further, in the state where the optical axis of the optical element B is coincident with the optical axis A, the paraxial maximum image height of the intermediate image in the in-focus state where the projection image becomes maximum is Did, and the refractive optical system The maximum value of the distance from the optical axis A of the intersection of the paraxial image plane and the light beam passing through the center of the stop is defined as D,
Conditional expression:
[2] 0.6 <D / Did <0.8
Is preferably satisfied (corresponding to claim 8).

That is, by satisfying conditional expression [2], it is possible to suppress the angle of the outgoing light beam from the refractive optical system, so that the thickness of the projection optical system in the Y-axis direction can be suppressed. If the value of D / Did falls below the lower limit of conditional expression [2], the strain on the free-form surface mirror becomes large to correct distortion, resulting in an increase in manufacturing error sensitivity. Further, if the value of D / Did exceeds the upper limit of conditional expression [2], the thickness increases, so that not only cannot be miniaturized, but in a vertical projector, the folded light beam interferes with the lens. End up. By decentering the optical element B, crossing the image display element and the optical axis A, and simultaneously satisfying conditional expression [2], the thickness of the projection optical system in the Y-axis direction is reduced while suppressing the occurrence of decentration aberrations. It becomes possible to do.
Furthermore, it is desirable that the optical system constituting the projection optical system is a non-telecentric optical system (corresponding to claim 9). Thus, the projection optical system can be reduced in size by using the non-telecentric optical system.
Furthermore, it is desirable to have a glass member having a curvature between the reflective optical system and the screen (corresponding to claim 10). That is, if the amount of eccentricity of the image display element in the Y-axis direction and the amount of eccentricity of the optical element B in the Y-axis direction are reduced, the optical performance is superior, but the image position on the screen is lowered. The incident angle to the glass member becomes large, and the illuminance of the image around the position screen decreases.

Since the incident angle can be reduced by providing a curvature to the glass member, it is possible to reduce the amount of eccentricity, and there is an effect that contributes to the thinning of the projection optical system and the improvement of the optical performance.
Furthermore, it is desirable to satisfy the following conditional expression [3], assuming that the diagonal size of the image display element is Go and the minimum screen size is Gi (corresponding to claim 11).
Conditional expression:
[3] Gi / Go> 73
If the value of Gi / Go is less than the lower limit value in conditional expression [3], the interference between the upper light beam incident on the lower end of the screen and the lens becomes unfavorable. By satisfying conditional expression [3], the substantial numerical aperture NA of the light incident on the screen can be darkened, and interference can be avoided.
More preferably, the following conditional expression [3 ′] is satisfied.
Conditional expression:
[3 '] Gi / Go> 90
Furthermore, the image display apparatus according to the present invention projects and displays an image by enlarging and projecting an image displayed on the image display element on a screen using the above-described projection optical system (corresponding to claim 12).

  Next, more specific embodiments and examples of the projection optical system according to the present invention will be described. In addition, here, as an embodiment and a specific example of the present invention, as a specific example 1 and a second embodiment as the first embodiment according to the projection optical system of the present invention. A specific example 2 will be described.

[First Embodiment]
First, a specific example 1 as the first embodiment of the present invention will be described in detail.

Example 1 is an example of a specific configuration of the projection optical system according to the first embodiment of the present invention.
FIG. 1 is a diagram for explaining a configuration of a projection optical system according to Example 1 which is a first embodiment of the present invention and an image display apparatus using the projection optical system. FIG. 1 shows a schematic main configuration of the entire image display apparatus using the projection optical system according to the first embodiment along a cross section that includes the optical axis and the long sides of the display screen of the image display element intersect perpendicularly. It is shown as a cross-sectional view.
First, main components used in common in all the embodiments and examples below will be described.
Specifically, for example, a DMD (Digital Micromirror Device) is used as a light valve as an image display element. In addition to DMD, for example, a transmissive liquid crystal panel and a reflective liquid crystal panel can be used as the light valve that is an image display element. The present invention is particularly limited to the types of light valves used in the image display element. Is not to be done.

The DMD used as an image display element is a device that has a large number of micromirrors and can electronically control the angles of these micromirrors individually within a predetermined angle range. For example, when the angle of one micromirror is −12 °, the reflected light of the illumination light from the micromirror is incident on the projection optical system, and when the angle is + 12 °, the reflected light of the illumination light enters the projection optical system. If the angle at which the illumination light enters the DMD is set so as not to enter, a digital image can be formed on the display screen of the DMD by controlling the tilt angle of each micromirror of the DMD.
Note that FIG. 1 shows a display screen portion that forms an image to be projected on the light valve, as an image forming unit LV of the light valve as an image display element.
When the image forming unit LV does not have a function of emitting light as in DMD or the like, the image information formed in the image forming unit LV is illuminated with illumination light from the illumination optical system LS. The illumination optical system LS preferably has a function of efficiently illuminating the image forming unit LV. For example, a rod integrator or a fly eye integrator can be used to make the illumination more uniform.

In addition, as an illumination light source in the illumination optical system LS, a white light source such as an ultrahigh pressure mercury lamp, a xenon lamp, a halogen lamp, and a (white) LED (light emitting diode) can be used, and a monochromatic light emitting LED and an LD (laser diode). A monochromatic light source such as) can also be used. The specific configuration of the illumination optical system LS is not particularly limited in the present invention, and detailed description thereof is omitted here in order to avoid complicated description. In Embodiment 1 of the present invention, a DMD is assumed as the image forming unit LV. Further, in the first embodiment of the present invention, as described above, it is assumed that the image forming unit does not have a function of emitting light by itself, but a self-light-emitting type having a function of emitting a generated image is used. In such a case, the illumination optical system LS may be unnecessary.
The parallel flat plate disposed in the vicinity of the image forming unit LV is assumed to be a cover glass (seal glass) FG of the image forming unit LV.
An image formed on the image display surface of the image forming unit LV is incident on the refractive optical system RR via the parallel plate FG, and is enlarged and formed on the screen SC via the refractive optical system RR and the reflective optical system RL. The refractive optical system RR is configured as a lens system including a stop AD.

Main parts other than the screen SC are accommodated in an exterior part HB which is a casing of the projection type image display device, and constitutes a projection type image display device.
The meanings of symbols in Examples (common to Examples 1 and 2) are as follows.
f: Focal length of entire system NA: Numerical aperture ω: Half angle of view (deg)
R: radius of curvature (paraxial radius of curvature for aspheric surfaces)
D: Surface spacing Nd: Refractive index νd: Abbe number K: Aspherical conical constant Ai: i-th order aspherical coefficient Cj: Free-form surface coefficient The aspherical shape is the reciprocal of the paraxial radius of curvature R (paraxial curvature) C Using the height H from the optical axis, the conic constant K, and the aspherical coefficient Ai of each order, where the aspherical amount in the optical axis direction is X, the well-known equation [4]:

The aspherical shape is specified by giving the paraxial radius of curvature R, the conic constant K, and the aspherical coefficient Ai.
The free-form surface shape uses an inverse number of the paraxial radius of curvature R (paraxial curvature) C, a height H from the optical axis, a conic constant K, and a free-form surface coefficient Cj, and the amount of free-form surface in the optical axis direction is X. The well-known formula [5]

  However,

The shape is specified by giving a paraxial radius of curvature R, a conical constant K, and a free-form surface coefficient Cj.

As shown in FIG. 1, the optical axis A is a normal direction of the image forming unit LV and is an axis shared by the axisymmetric lens in the refractive optical system RR (not clearly shown in FIG. 1). Of the display screen of the image display element, that is, the center of the screen of the image forming unit LV, and is perpendicular to the optical axis A among the in-plane axes including light rays passing through the center of the stop AD. The axis is the Y axis, the axis perpendicular to the optical axis A (Z axis parallel to the optical axis) and the Y axis is the X axis, and in FIG. 1, the counterclockwise rotation direction from the Z axis is the + α direction. Moreover, the direction of the arrow shown in the figure indicates the positive direction.
FIG. 1 and FIG. 2 are diagrams for explaining the configuration of an image display apparatus using the projection optical system according to Example 1 which is the first embodiment of the present invention. Among these, FIG. 1 is a cross-sectional view showing a schematic main configuration of the entire projection optical system according to the first embodiment along a cross section that includes the optical axis and in which the long sides of the display screen of the image display element intersect perpendicularly. It is. FIG. 2 is a sectional view showing in more detail the lens system of the refractive optical system and its focusing operation in the projection optical system of FIG.
1 and 2, the image on the display screen of the image forming unit LV of the image display element is projected onto the screen SC from the cover glass FG through the refractive optical system RR and the reflective optical system RL through the dust-proof glass BG. . The image display element (image forming part LV), the cover glass FG, the refractive optical system RR, and the reflective optical system RL are accommodated in the exterior part HB and constitute a projection type image display apparatus. The cover glass FG is provided in the emission part of the projection light from the exterior part HB.

The refractive optical system RR is configured as a lens system including a stop AD, and as shown in FIG. 2, from the image forming unit LV side, the first lens group G1, the second lens group G2, the third lens group G3, and A fourth lens group G4 is disposed. The aperture stop AD is disposed in the first lens group G1.
The reflective optical system RL deflects the light beam emitted from the refractive optical system RR substantially at right angles, and the concave mirror that deflects the light beam from the folded flat mirror M1 and projects it onto the screen SC through the dust-proof glass BG. Has M2.
1 shows the configuration of the projection optical system of the image display apparatus according to the first embodiment of the present invention, and FIG. 2 mainly shows the configuration of the lens system of the refractive optical system RR and the lens at the time of focusing. The trajectory of the group is shown. In FIG. 2, the locus of movement of the lens unit by focusing is shown by a solid line. Further, as shown in FIG. 1, the direction of the optical axis A is the Z axis, the center of the screen of the image forming unit LV and the center of the stop AD, and the direction perpendicular to the optical axis A on the plane including the light beam passing through the center of the screen. The Y axis is assumed. The direction from the image display element (image forming unit LV) toward the folding plane mirror M1 is defined as + Z direction, and the direction from the folding plane mirror M1 toward the concave mirror M2 is defined as + Y direction. Further, the rotation from the + Z direction to the + Y direction is defined as + α rotation on the plane including the light beam passing through the center of the image display element (image forming unit LV), the center of the stop AD, and the center of the screen SC.

A light beam that is two-dimensionally intensity-modulated by the DMD of the image forming unit LV according to image information becomes a projection light beam as object light. The projection light beam from the image forming unit LV is a refractive optical system RR including the optical element B (first lens group G1, second lens group G2, third lens group G3, fourth lens group G4), a folded plane mirror M1, and An imaged light beam passes through the concave mirror M2. That is, the image formed on the DMD (image forming unit LV) is enlarged and projected on the screen SC by the projection optical system, and becomes a projected image. Here, a surface on which an image is formed in the image forming unit LV is defined as an image forming surface.
FIG. 3 is a schematic diagram schematically showing the form of the display screen of the image forming unit LV of the image display element in the projection optical system and the positional relationship with respect to the optical axis, and FIG. 4 is a paraxial image plane in the projection optical system. It is a schematic diagram for demonstrating relations, such as an intermediate image and an optical axis.
Each optical element constituting the refractive optical system RR shares an optical axis, and the image forming unit LV is shifted in the Y direction with respect to the optical axis A as shown in FIG. Intersects. When the intersection of the image forming surface of the image forming unit LV and the optical axis A is C0, the conjugate point of the intersection C0 by the refractive optical system RR when the optical axis of the optical element B is coincident with the optical axis A CC. A plane including the conjugate point CC and perpendicular to the optical axis A is defined as a paraxial image plane. As shown in FIG. 4, among the intersections of the paraxial image plane and a ray passing through the center of the stop (hereinafter referred to as the principal ray), the distance from the intersection CC of the optical axis A and the paraxial image plane is the maximum. Is obtained by multiplying the point where the distance between the optical axis A and the end of the image forming unit LV is maximum (L0 in FIG. 3) by the paraxial magnification by the refractive optical system RR. High Did.

In this embodiment, the refractive optical system RR and a single concave mirror M2 are used to form a substantial optical system. However, even if a mirror is added or the folding mirror is given power. Good. However, this is not preferable because the configuration becomes complicated and not only increases in size but also leads to a significant increase in cost.
The light passing through the refractive optical system RR forms an intermediate image conjugate with the image information formed in the image forming unit LV as an aerial image on the image forming unit LV side from the mirror M1 of the reflective optical system RL. The intermediate image does not need to be formed as a planar image, and is formed as a curved surface image in both the first embodiment and the other embodiments. The intermediate image is enlarged and projected by the free-form curved concave mirror M2 arranged on the most magnified projection side, and projected onto the screen SC. The intermediate image has field curvature and distortion, but this can be corrected by using a free-form surface for the concave mirror M2. For this reason, the burden of aberration correction on the lens system of the refractive optical system RR is reduced, which increases the degree of design freedom and is advantageous for downsizing and the like. In addition, the free-form surface here means that the curvature in the X direction according to the position in the X direction is not constant at any position in the Y direction, and the Y direction according to the position in the Y direction at any position in the X direction. This means an anamorphic surface with a constant curvature.

A dust-proof glass BG is installed between the free-form curved concave mirror M2 and the screen SC. In Example 1, parallel flat glass is used as the dust-proof glass BG, but it may have a curvature or may be an optical element having power such as a lens. In addition, although it is arranged to be inclined with respect to the optical axis A, the angle may be arbitrary and may be perpendicular to the optical axis A.
FIG. 5 is a schematic diagram for explaining the relationship between the paraxial image plane and the intersection of the principal ray at a long distance (screen size is 100 inches) of the projection optical system, and FIG. 6 is an intermediate distance of the projection optical system. FIG. 7 is a schematic diagram for explaining the relationship between the paraxial image plane (at a screen size of 80 inches) and the intersection with the principal ray, and FIG. 7 is a diagram showing a near distance at a short distance (screen size is 60 inches) of the projection optical system. It is a schematic diagram for demonstrating the relationship between an axial image surface and the intersection of a chief ray. That is, FIG. 5, FIG. 6 and FIG. 7 show the intersection of the paraxial image plane and the principal ray at a long distance (screen size 100 inches), an intermediate distance (screen size 80 inches) and a short distance (screen size 60 inches). Is plotted. The black dots indicate the coordinates of the intersection of the principal ray and the paraxial image plane at each angle of view, and the broken lines indicate the paraxial image. From these figures, it can be seen that the barrel is distorted even in each screen size. That is, this is nothing but the intermediate image is compressed. Therefore, since the free-form curved mirror can be reduced in size by reducing the size of the intermediate image, the cost can be reduced and the apparatus can be reduced in size.

When focusing from the long distance side to the short distance side, in this embodiment, the first lens group G1, which is a positive lens group, the folding plane mirror M1, and the free-form surface mirror M2 are fixed with respect to the image forming surface. The second lens group G2, which is a positive lens group, and the third lens group G3, which is a negative lens group, move toward the image forming unit LV, and the fourth lens group G4, which is a positive lens group, is on the magnification projection side. Move to the reflective optical system RL side. In other words, the field curvature and distortion can be controlled to a high degree by performing the floating focus. In this embodiment, the correction effect is further enhanced by using an aspherical lens in the moving lens group.
The entire optical system described above, and parts necessary for image formation, that is, an image processing unit and a power supply unit (not shown), a cooling fan, and the like constitute an exterior unit that forms a housing together with the optical system that constitutes the projection optical system. A projection type image display device is housed in the HB.
A specific configuration of the above-described projection optical system will be described in more detail.

A first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and one sheet having a negative refractive power in order from the image forming unit LV toward the magnification projection side A third lens group G3 including the aspherical lens, a fourth lens group G4 including a single aspherical lens having a positive refractive power, a folding plane mirror M1, and a free curved concave surface closest to the enlargement projection side A mirror M2 is arranged. Focusing with respect to variation in the projection distance is such that, when focusing from the long distance side to the short distance side, the positive second lens group G2 and the negative third lens group G3 move to the image forming unit side, and the positive fourth lens group. G4 moves to the enlarged projection side.
The first lens group G1 includes, in order from the image forming unit LV side, a first lens E1 composed of a biconvex lens in which an aspheric surface is formed on both surfaces with a strong convex surface facing the image forming unit LV side, and an image forming unit LV side. Consists of a second lens E2 composed of a positive meniscus lens having a convex surface, a third lens E3 composed of a negative meniscus lens having a convex surface facing the image forming portion LV, and a positive meniscus lens having a convex surface facing the image forming portion LV. A double-junction lens formed by bonding the fourth lens E4 in close contact with each other, an aperture stop AD, a fifth lens E5 composed of a biconcave lens having a stronger concave surface on the enlargement projection side, and a stronger convex surface on the enlargement projection side A sixth lens E6 composed of a biconvex lens facing the lens, a seventh lens E7 composed of a negative meniscus lens having a convex surface facing the image forming portion LV and aspheric surfaces on both surfaces, and magnified projection The eighth lens E8 composed of a biconvex lens having a stronger convex surface and the ninth lens E9 composed of a biconcave lens having a stronger concave surface directed toward the image forming unit LV are brought into close contact with each other and joined from the optical axis A in the + Y direction. And a tenth lens L10 composed of a positive meniscus lens having a convex surface facing the image forming unit LV, and a decentered optical element B that is shifted by 2.04 mm. . In other words, the two-element cemented lens including the eighth lens E8 and the ninth lens E9 is the optical element B arranged eccentrically.

The second lens group G2 includes an eleventh lens E11 made of a positive meniscus lens having a convex surface directed toward the image forming unit LV. The third lens group G3 includes, sequentially from the image forming unit LV side, a twelfth lens E12 composed of a negative meniscus lens having a convex surface facing the magnified projection side, and a negative meniscus lens having a convex surface facing the magnified projection side. A thirteenth lens E13 and a fourteenth lens E14 composed of a negative meniscus lens having a convex surface facing the image forming portion LV and aspheric surfaces on both surfaces are arranged. The fourth lens group G4 includes a fifteenth lens E15 made of a positive meniscus lens having a convex surface facing the enlargement projection side and aspheric surfaces formed on both surfaces.
The lens groups G1 to G4 described above constitute a refractive optical system RR, and a folding plane mirror M1 and a free-form curved concave mirror M2 are installed on the enlarged projection side.
The optical characteristics of the optical elements in Example 1 are as shown in Table 1 below. In this case, the numerical aperture NA is 0.200.

In Table 1, the lens surface with the surface number indicated by adding “* (asterisk)” to the surface number is an aspherical surface. In Table 1, the 33rd surface, which is the reflecting surface of the concave mirror M2 indicated by attaching “# (also referred to as a number sign, hash mark, etc.)” to the surface number, indicates a free-form surface. The shape of this free-form surface is defined by the equation [5] described above.
Table 1 also shows the material of each lens. In the case of a glass material of optical glass, the number and manufacturer of the glass material are shown. The abbreviations of the glass material manufacturers are OHARA for OHARA Corporation and HOYA for HOYA Corporation.
Further, in Table 1, the variable distance DA between the 21st surface and the 22nd surface, the 23rd surface and the 24th surface, the 29th surface and the 30th surface, the 31st surface and the 32nd surface, and the 33rd surface and the screen SC, DB, DC, DD and DE are the first lens group G1 and the second lens group G2, the second lens group G2 and the third lens group G3, the third lens group G3, the fourth lens group G4, and the fourth lens group G4. The group spacings between the plane mirror M1 and the concave mirror M2 and the screen SC and the screen SC are shown, and the magnification can be changed by changing these group spacings. And a value as shown in Table 2 are changed depending on whether it is 100 inches or 100 inches. Table 2 shows changes in the variable intervals DA, DB, DC, DD, and DE in Table 1 when the projection distance, that is, focusing is performed by changing the screen size.

  In Table 1, the optical surfaces of the fourth surface, the fifth surface, the fifteenth surface, the sixteenth surface, the twenty-eighth surface, the twenty-ninth surface, the thirty-third surface, and the thirty-first surface marked with “*” are aspherical surfaces. Table 3 shows the parameters of each aspheric surface in the equation [4]. In the aspheric coefficient, “En” represents “power of 10”, that is, “× 10n”, and for example, “E-05” represents “× 10-5”. The same applies to the other embodiments.

  The free-form surface of the 33rd concave mirror M2 (see FIG. 1) is defined by giving a coefficient / constant such as Cj according to Table 4 to the equation [5] described above.

  When the projection distance is changed and the screen size is 60 inches, 80 inches, and 100 inches, TR = (concave mirror and optical axis A in conditional expression [1]) Table 5 shows the value of (distance from the intersection with the screen) / (screen width). Therefore, in the projection optical system according to Example 1, the value of “TR” satisfies the conditional expression [1].

The size of the DMD used for the image forming unit LV in the first embodiment is as follows.
Dot size: 7.56 μm
Horizontal length: 14.5152mm
Longitudinal length: 8.1648mm
It is. The shift amount of the image forming unit LV with respect to the optical axis A is as follows.
Optical axis to element center: 3.9824 mm
Furthermore, D / Did of conditional expression [2] and Gi / Go of conditional expression [3] are respectively D / Did: 0.68
Gi / Go: 91.5
It is. Therefore, the projection optical system according to Example 1 satisfies the conditional expressions [2] and [3].
Table 6 shows the position coordinates of the folding plane mirror M1 and the free-form curved concave mirror M2 from the apex in the in-focus state where the projection image of the fifteenth lens E15 located closest to the reflecting surface is the maximum. Note that the rotation angle α indicates the angle formed by the surface normal and the optical axis.

8, 9, and 10 show spot positions with a wavelength of 550 nm on the screen SC at each zoom projection distance in the first embodiment. 8 to 10, it can be seen that a projection image with little distortion can be projected even at each zoom projection distance.
FIG. 11, FIG. 12 and FIG. 13 show spot diagrams at each zoom projection distance. Each spot diagram shows imaging characteristics on the screen SC surface for wavelengths of 625 nm (red), 550 nm (green), and 425 nm (blue). Further, F1 to F13 in FIGS. 11 to 13 correspond to the angles of view shown in FIG.

[Second Embodiment]
Next, a specific example 2 as the above-described second embodiment of the present invention will be described in detail.

Example 2 is an example of a specific configuration of the projection optical system according to the second embodiment of the present invention.
FIG. 15 and FIG. 16 are for explaining the configuration of an image display apparatus using the projection optical system according to Example 2 which is the second embodiment of the present invention. Among these, FIG. 15 shows the main configuration of the entire image display apparatus using the projection optical system according to the second embodiment, along a cross section that includes the optical axis and the long sides of the display screen of the image display element intersect perpendicularly. It is sectional drawing shown. FIG. 16 is a sectional view showing in more detail the lens system of the refractive optical system of the projection optical system of FIG. 15 and its focusing operation.
15 and 16, the image on the display screen of the image forming unit LV of the image display element is projected from the cover glass FG to the screen SC through the refractive optical system RR and the reflective optical system RL through the dust-proof glass BG. . The image display element (image forming unit LV), the cover glass FG, the refractive optical system RR, and the reflective optical system RL are accommodated in the exterior part HBa and constitute a projection type image display apparatus. The cover glass FG is provided in the emission part of the projection light from the exterior part HBa.

The configuration of the second embodiment shown in FIGS. 15 and 16 is basically the same as that of the first embodiment except that the folding plane mirror M1 in the first embodiment is not provided and the reflection is performed only once by the free-form curved concave mirror CM. Since the configuration is the same, in the second embodiment, instead of the exterior portion HB, the reflective optical system RL, and the concave mirror M2 of the first embodiment, an exterior portion HBa, a reflective optical system RLa, and a free-form curved concave mirror CM are provided. Yes.
The refractive optical system RR is configured as a lens system including a stop AD, and sequentially includes a first lens group G1, a second lens group G2, a third lens group G3, and a fourth lens group G4 from the image forming unit LV side. It is arranged. The aperture stop AD is disposed in the first lens group G1.
The reflective optical system RLa has a free-form concave mirror CM that deflects the light beam emitted from the refractive optical system RR and projects it onto the screen SC through the dust-proof glass BG.
15 shows the configuration of the projection optical system of the image display apparatus according to Example 2 in the second embodiment of the present invention, and FIG. 16 mainly shows the configuration of the lens system and focusing of the refractive optical system RR. The locus of the lens group is shown. In FIG. 16, the locus of movement of the lens group by focusing is indicated by a solid line.

Further, as shown in FIG. 15, the direction of the optical axis A is the Z axis, the center of the screen of the image forming unit LV and the center of the stop AD, and the direction perpendicular to the optical axis A on the plane including the light beam passing through the center of the screen. The Y axis is assumed. The direction from the image display element (image forming unit LV) toward the free curved concave mirror CM is defined as + Z direction, and the direction reflected from the free curved concave mirror CM and away from the optical axis A is defined as + Y direction. Further, the rotation from the + Z direction to the + Y direction is defined as + α rotation on the plane including the light beam passing through the center of the image display element (image forming unit LV), the center of the stop AD, and the center of the screen SC.
A light beam that is two-dimensionally intensity-modulated by the DMD of the image forming unit LV according to image information becomes a projection light beam as object light. The projection light beam from the image forming unit LV is a refractive optical system RR (first lens group G1, second lens group G2, third lens group G3, fourth lens group G4) including the optical element B and a free-form curved concave mirror CM. And is formed into an imaging light flux. That is, the image formed on the DMD (image forming unit LV) is enlarged and projected on the screen SC by the projection optical system, and becomes a projected image. Here, a surface on which an image is formed in the image forming unit LV is defined as an image forming surface.

Each optical element constituting the refractive optical system RR shares an optical axis, and the image forming unit LV is shifted in the Y direction with respect to the optical axis A as shown in FIG. Intersects. When the intersection of the image forming surface of the image forming unit LV and the optical axis A is C0, the intersection by the refractive optical system RR when the optical axis of the optical element B at the intersection C0 coincides with the optical axis A Let CC be the conjugate point of CC. A plane including the conjugate point CC and perpendicular to the optical axis A is defined as a paraxial image plane. As shown in FIG. 4, among the intersections of this paraxial image plane and a line passing through the center of the stop AD (hereinafter referred to as the principal ray), the distance from the intersection C of the optical axis A and the paraxial image plane is D Further, a point obtained by multiplying the point (L0 in FIG. 3) where the distance between the optical axis A and the image forming unit is the maximum by the paraxial magnification by the refractive optical system RR is defined as the paraxial maximum image height Did.
In the second embodiment, a substantial optical system is configured by using the refractive optical system RR and one concave mirror CM. However, by adding a mirror or giving power to the folding mirror. Also good. However, this is not preferable because the configuration becomes complicated and not only increases in size but also leads to a significant increase in cost.

The light passing through the refractive optical system RR forms an intermediate image conjugate with the image information formed in the image forming unit LV as an aerial image on the image forming unit LV side from the free curved concave mirror CM constituting the reflective optical system RLa. To do. The intermediate image does not need to be formed as a planar image, and is also formed as a curved image in the second embodiment. The intermediate image is magnified and projected by the free-form curved concave mirror CM arranged on the most magnified projection side, and projected onto the screen SC. The intermediate image has field curvature and distortion, but this can be corrected by using a free-form surface for the concave mirror CM. For this reason, the burden of aberration correction on the lens system of the refractive optical system RR is reduced, which increases the degree of design freedom and is advantageous for downsizing and the like. In addition, the free-form surface here means that the curvature in the X direction according to the position in the X direction is not constant at any Y position, and the Y direction according to the position in the Y direction at any X position. This means an anamorphic surface with a constant curvature.
A dustproof glass BG is installed between the free curved concave mirror CM and the screen SC. In Example 2, parallel flat glass is used as the dust-proof glass BG, but it may have a curvature, or may be an optical element having power such as a lens. In addition, although it is arranged to be inclined rather than perpendicular to the optical axis A, this angle may be arbitrary and may be perpendicular to the optical axis A.

FIG. 17 is a schematic diagram for explaining the relationship between the paraxial image plane at the long distance (screen size 100 inches) of the projection optical system and the intersection of the principal rays. FIG. 18 is a schematic diagram for explaining the relationship between the paraxial image plane at the intermediate distance (screen size 80 inches) of the projection optical system and the intersection of the principal rays. FIG. 19 is a schematic diagram for explaining the relationship between the paraxial image plane at the short distance (screen size 60 inches) of the projection optical system and the intersection of the principal rays. That is, FIG. 17, FIG. 18 and FIG. 19 plot the intersections of the paraxial image plane and the principal ray at a long distance (screen size 100 inches), an intermediate distance (screen size 80 inches), and a short distance (screen size 60 inches). Shows what you did. The black dots indicate the coordinates of the intersection of the principal ray and the paraxial image plane at each angle of view, and the broken lines indicate the paraxial image. From these figures, it can be seen that the barrel is distorted even in each screen size. In other words, this is nothing but the intermediate image is compressed. Therefore, since the free-form curved mirror can be reduced in size by reducing the size of the intermediate image, the cost can be reduced and the apparatus can be reduced in size.
In focusing from the long distance side to the short distance side, in the present embodiment, the first lens group G1, which is a positive lens group, and the free-form surface mirror CM are fixed with respect to the image forming surface. A certain second lens group G2 and a third lens group G3 that is a negative lens group move to the image forming unit LV side, and a fourth lens group G4 that is a positive lens group is a reflection optical system RL side that is an enlargement projection side Move to.

In other words, the field curvature and distortion can be controlled to a high degree by performing the floating focus. In the present embodiment, the effect of correction is further enhanced by using an aspheric lens in the moving lens group.
The entire optical system described above, and parts necessary for image formation, that is, an image processing unit and a power supply unit (not shown), a cooling fan, and the like constitute an exterior unit that forms a housing together with the optical system that constitutes the projection optical system. It is housed in HBa to constitute a projection type image display device.
A specific configuration of the above-described projection optical system will be described in more detail.
A first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and one sheet having a negative refractive power in order from the image forming unit LV toward the magnification projection side A third lens group G3 including an aspherical lens, a fourth lens group G4 including a single aspherical lens having positive refractive power, and a free-form curved concave mirror CM on the most magnified projection side. When focusing from the far side to the near side, the positive second lens group G2 and the negative third lens group G3 are moved to the image forming unit LV side, and focusing on the variation in the projection distance is performed. The lens group G4 moves to the enlarged projection side.

  The first lens group G1 includes, in order from the image forming unit LV side, a first lens E1 composed of a biconvex lens in which an aspheric surface is formed on both surfaces with a strong convex surface facing the image forming unit LV side, and an image forming unit LV side. Consists of a second lens E2 composed of a positive meniscus lens having a convex surface, a third lens E3 composed of a negative meniscus lens having a convex surface facing the image forming portion LV, and a positive meniscus lens having a convex surface facing the image forming portion LV. A double-junction lens formed by bonding the fourth lens E4 in close contact with each other, an aperture stop AD, a fifth lens E5 composed of a biconcave lens having a stronger concave surface on the enlargement projection side, and a stronger convex surface on the enlargement projection side A sixth lens E6 composed of a biconvex lens facing the lens, a seventh lens E7 composed of a negative meniscus lens having a convex surface facing the image forming portion LV and aspheric surfaces on both surfaces, and magnified projection The eighth lens E8 composed of a biconvex lens having a stronger convex surface and the ninth lens E9 composed of a biconcave lens having a stronger concave surface directed toward the image forming unit LV are brought into close contact with each other and joined from the optical axis A in the + Y direction. And a tenth lens L10 composed of a positive meniscus lens having a convex surface facing the image forming unit LV, and a decentered optical element B that is shifted by 2.04 mm. . In other words, the two-element cemented lens including the eighth lens E8 and the ninth lens E9 is the optical element B arranged eccentrically.

The second lens group G2 includes an eleventh lens E11 made of a positive meniscus lens having a convex surface directed toward the image forming unit LV.
The third lens group G3 includes, sequentially from the image forming unit LV side, a twelfth lens E12 composed of a negative meniscus lens having a convex surface facing the magnified projection side, and a negative meniscus lens having a convex surface facing the magnified projection side. A thirteenth lens E13 and a fourteenth lens E14 composed of a negative meniscus lens having a convex surface facing the image forming portion LV and aspheric surfaces on both surfaces are arranged.
The fourth lens group G4 includes a fifteenth lens E15 made of a positive meniscus lens having a convex surface facing the enlargement projection side and aspheric surfaces formed on both surfaces.
The lens groups G1 to G4 described above constitute a refractive optical system RR, and a free-form curved concave mirror CM is installed on the enlarged projection side.
Table 7 shows the optical characteristics of the optical elements in Example 2. In this case, the numerical aperture NA is 0.200.

In Table 7, the lens surface with the surface number indicated by adding “*” to the surface number is an aspherical surface. In Table 1, the 32nd surface, which is the reflecting surface of the concave mirror CM indicated by adding “# (also referred to as a number sign, hash mark, etc.)” to the surface number, indicates a free-form surface. The shape of the free-form surface is defined by the equation [5] described above.
Table 7 also shows the material of each lens. In the case of a glass material of optical glass, the number and manufacturer of the glass material are shown. The abbreviations of the glass material manufacturers are OHARA for OHARA Corporation and HOYA for HOYA Corporation.
Moreover, the variable space | interval (DA, DB, DC, DD, and DE) in the 21st surface and the 22nd surface in Table 7, the 23rd surface and the 24th surface, the 29th surface and the 30th surface, and the 31st surface and the 32nd surface Are a first lens group G1 and a second lens group G2, a second lens group G2 and a third lens group G3, a third lens group G3 and a fourth lens group G4, a fourth lens group G4 and a free-form curved concave mirror CM, respectively. In addition, the group spacing between the free-form curved concave mirror CM and the screen SC is shown, and the enlargement ratio can be changed by changing the group spacing. When the screen size is set to 60 inches and 80 inches The value is changed as shown in Table 8 for the case of 100 inches. Table 8 shows changes in the plane distances of the variable distances DA, DB, DC, DD, and DE in Table 7 when the projection distance, that is, focusing is performed by changing the screen size.

  In Table 7, the optical surfaces of the fourth surface, the fifth surface, the fifteenth surface, the sixteenth surface, the twenty-eighth surface, the twenty-ninth surface, the thirty-third surface, and the thirty-first surface marked with “*” are aspheric surfaces. Table 9 shows the parameters of each aspheric surface in Equation [4].

  The free-form surface of the 33rd concave mirror CM is defined by giving a coefficient / constant such as Cj according to Table 10 to the equation [5] described above.

  When the projection distance is changed and the screen size is 60 inches, 80 inches, and 100 inches, TR = (concave mirror and optical axis A in conditional expression [1]) Table 11 shows the values of (distance from the intersection with the screen) / (screen width).

That is, in Example 2, the value corresponding to the conditional expression [1] satisfies the conditional expression [1] as shown in “TR” of Table 11.
The size of the DMD used for the image forming unit LV in the second embodiment is as follows:
Dot size: 7.56 μm
Horizontal length: 14.5152mm
Longitudinal length: 8.1648mm
It is. The shift amount of the image forming unit LV with respect to the optical axis A is as follows.
Optical axis to element center: 3.9824 mm
Furthermore, D / Did of conditional expression [2] and Gi / Go of conditional expression [3] are respectively D / Did: 0.68
Gi / Go: 91.5
Which satisfies conditional expression [2] and conditional expression [3].
Table 12 shows the position coordinates of the free-form curved concave mirror CM from the apex in the in-focus state where the projection image of the fifteenth lens E15 located closest to the reflecting surface is the maximum. Note that the rotation angle α indicates the angle formed by the surface normal and the optical axis.

20, 21, and 22 show spot positions with a wavelength of 550 nm for each angle of view on the screen SC at each zoom projection distance in the second embodiment. 20 to 22, it can be seen that a projection image with little distortion can be projected even at each zoom projection distance.
23, 24, and 25 show spot diagrams at each zoom projection distance. Each spot diagram shows imaging characteristics on the screen SC surface for wavelengths of 625 nm (red), 550 nm (green), and 425 nm (blue). Further, F1 to F13 in FIGS. 23 to 25 correspond to the angle of view shown in FIG. 14 as in the case of the first embodiment.

LV image forming unit (light valve)
FG cover glass BG dustproof glass HB, HBa exterior SC screen RR refractive optical system G1 first lens group G2 second lens group G3 third lens group G4 fourth lens group AD aperture stop RL, RLa reflective optical system M1 folding plane mirror M2, CM Free curved concave mirror E1 1st lens E2 2nd lens E3 3rd lens E4 4th lens E5 5th lens E6 6th lens E7 7th lens E8 8th lens E9 9th lens E10 10th lens E11 11th Lens E12 12th lens E13 13th lens E14 14th lens E15 15th lens

JP 2007-79524 A JP 2011-242606 A JP 2012-108267 A JP 2009-216883 A

Claims (12)

A projection optical system for enlarging and projecting an image displayed on an image display element on a screen,
The projection optical system includes:
A plurality of optical elements including a diaphragm and a plurality of lenses, and a refractive optical system for enlarging an image displayed on the image display element;
A reflective optical system having at least one reflective optical element disposed between the refractive optical system and the screen,
Forming an intermediate image between the image display element and the reflective optical system;
An axis shared by the plurality of axially symmetric lenses in the refractive optical system is defined as an optical axis A, and includes an optical axis A that includes the optical axis A and includes a light beam emitted from the center of the image display element and passing through the center of the stop. And when the axis perpendicular to the optical axis A is the Y axis, a part of the optical elements B of the refractive optical system is decentered in a direction parallel to the Y axis,
The projection optical system, wherein the image forming unit of the image display element and the optical axis A intersect each other.   The projection optical system according to claim 1, wherein the optical element B has negative power.   The projection optical system according to claim 1, wherein the optical element B is disposed closer to the reflective optical element than the stop.   The projection optical system according to claim 1, wherein the optical element B is a spherical lens.   The projection optical system according to claim 1, wherein the reflective optical element is a concave mirror having a free-form surface. The screen on which the image is projected is
The distance from the intersection of the concave mirror and the optical axis A to the screen / screen width is TR,
Conditional expression:
[1] TR <0.30
The projection optical system according to claim 1, wherein:   The projection optical system according to claim 1, wherein the optical axis A is orthogonal to the image display element. In a state where the optical axis of the optical element B coincides with the optical axis A, the paraxial maximum image height of the intermediate image in a focused state where the projection image is maximum is Did, and the paraxial by the refractive optical system The maximum value of the distance from the optical axis A of the intersection of the image plane and the light beam passing through the center of the stop is defined as D,
Conditional expression:
[2] 0.6 <D / Did <0.8
The projection optical system according to claim 1, wherein:   The projection optical system according to any one of claims 1 to 8, wherein the projection optical system forms a non-telecentric optical system.   The projection optical system according to any one of claims 1 to 9, wherein a glass member having a curvature is disposed between the reflection optical system and the screen. The diagonal size of the image display element is Go, and the minimum screen size is Gi.
Conditional expression:
[3] Gi / Go> 73
The projection optical system according to claim 1, wherein:   An image display device that uses the projection optical system according to any one of claims 1 to 10 to enlarge and project an image displayed on the image display element onto the screen and project and display the image. .