JP2008181152A - Projection optical system, magnification projection optical system, magnification projection apparatus, and image projection apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projection optical system that can increase projection screen in size, employ an imaging optical system that includes a reflecting surface to reduce a projection space outside a projection apparatus, and correct chromatic aberrations, and to provide an image projection apparatus that has such a projection optical system. <P>SOLUTION: The projection optical system includes a transmissive optical system 3, consisting of transmitting surfaces having refractive index, the optical system 3 propagating luminous flux emitted from an image display panel; and a reflecting optical system provided downstream of the transmissive optical system, the reflecting optical system including a plurality of reflecting surfaces among which a reflective surface 4 having negative power is located on the most upstream side than other reflecting surfaces. The projection optical system images an intermediate image 9 as an erected image on a screen S, where the intermediate image 9 of the image display panel at negative magnification is imaged downstream of the reflecting surface, having the negative power. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

Liquid crystal projectors that are widely known as image projection apparatuses have recently been improved in the resolution of liquid crystal panels, the improvement in brightness accompanying the increase in efficiency of light source lamps, and the reduction in price.
In addition, compact and lightweight image projection devices using DMD (Digital Micro-mirror Device) have become widespread, and these image projection devices are widely used not only in offices and schools but also at home. In particular, front-type projectors have improved portability and have been used for small meetings of several people.

  A projector that is an image projection apparatus is required to be able to project an image on a large screen (enlarge the projection screen) and to make the “projection space required outside the projector” as small as possible.

  In order to reduce the projection space outside the projector while enlarging the projection screen, the optical path of the imaging light beam that forms the projected image should be “retracted inside the image projection device” as much as possible. As an image projection apparatus having such a device, those described in Patent Documents 1 to 5 are known.

  The image projection apparatus described in Patent Document 1 includes first to fourth reflecting mirrors in order to suppress an increase in the size of the imaging optical system and widen the angle of view, and the first reflecting mirror has a concave shape and a second shape. The fourth reflecting mirror is a convex surface, and an imaging optical system is configured by these reflecting mirrors. In addition, at least one of the first to fourth reflecting mirrors has a free-form surface to ensure projection performance.

  The image projection apparatus described in Patent Document 2 is a surface projection type display in which a projection distance to a screen is shortened, and an imaging optical system is configured by a pair of a concave mirror, a “convex mirror having a diverging action”, and a projection lens. ing.

  The image projection apparatus described in Patent Document 3 is a “video projector”, and the first mirror surface in the imaging optical system is formed in a convex shape to reduce the thickness of the apparatus.

  The image projection methods described in Patent Documents 1 and 3 have an advantage that, in order to enlarge and project the light valve image on the screen, the image is formed only by the reflecting mirror, and chromatic aberration does not occur in principle. . However, if the red, green, and blue images are displayed separately on the three light valves and are combined on the screen as in the three-plate type instead of the single-plate type, a cross prism, a Philips prism, etc. In this case, the chromatic aberration is generated at the time of the color synthesis, but the chromatic aberration cannot be corrected by the imaging optical system using only the reflecting surface.

  In the image projection apparatus described in Patent Document 4, the light beam from the image display panel is sequentially applied to the screen by an enlargement projection optical system including an imaging lens system having a positive power and a reflection optical system including a curved mirror having a negative power. The light is guided to form an image.

  The height of the screen and the imaging lens system are set so as to be shifted from each other, folded back by a mirror, and guided to the screen. For this reason, the optical path length of the imaging light flux is different between the upper side and the lower side of the center portion of the enlarged projection image on the screen (corresponding to the center portion of the image display panel). As a result, so-called “trapezoidal distortion” occurs. To do.

  The trapezoidal distortion can be corrected by “keystone correction”, but the keystone correction tends to cause image quality deterioration of the enlarged image on the screen.

  As a configuration for reducing the trapezoidal distortion, a configuration is known in which “a convex mirror is provided eccentrically with respect to the optical axis of the imaging lens” between the imaging lens system and the screen. When the convex mirror is arranged eccentrically, a convex mirror is arranged on the imaging lens system "on the imaging lens side than the focal position on the screen side", and the focal position of the projection lens is extended by the negative refractive power of the convex mirror. .

  In order to realize a thin and large screen enlargement projection device with such a configuration, there is a method of increasing the negative power of the convex mirror to widen the angle of view, but the shape accuracy and assembly tolerance of the convex mirror are severe. And distortion increases.

  Increasing the distance between the imaging lens and the convex mirror can weaken the refractive power of the convex mirror and reduce distortion. However, as the distance between the imaging lens and the convex mirror increases, the convex mirror becomes larger. As a result, the cost of the mirror increases, and the enlargement projection device tends to increase in size.

  In Patent Document 5, an enlargement projection optical system is configured only by a reflection mirror. As described above, when obtaining desired optical performance without using the lens optical system, it is necessary to set the surface accuracy and position accuracy of each reflecting surface to be extremely high, and the assembling accuracy of the magnifying projection optical system becomes severe. .

JP 2002-40326 JP 2002-174853 A Japanese Patent Publication No. 6-91641 JP 2001-264627 A JP 2002-296503 A

The present invention has been made in view of the above-described circumstances, and employs an imaging optical system including a reflecting surface in order to reduce the projection space outside the projection apparatus while increasing the size of the projection screen. However, an object of the present invention is to realize a projection optical system, an enlarged projection optical system, an enlarged projection apparatus, and an image projection apparatus using such a projection optical system that can also correct chromatic aberration.
Another object of the present invention is to reduce the thickness of the image projection apparatus and to project a large screen without distortion.

Prior to the description of the invention below, the reference technique S1 and the like similar to the present invention will be described, and the terms will be explained together. Reference techniques S1, S2,... Are also referred to as “S1, S2,.
The projection optical system of S1 is “in the image projection apparatus that irradiates the light valve that forms an image according to the modulation signal with the illumination light from the light source and enlarges and projects the image formed on the light valve by the projection optical system. A projection optical system for enlarging and projecting an image formed on a bulb ”, which has the following characteristics.

That is, the first and second optical systems are arranged in the first and second order from the light valve side on the light valve projection side (projection light beam traveling side).
The “first optical system” includes one or more refractive optical systems and has a positive power.
The “second optical system” includes one or more reflecting surfaces having power and has positive power.
The image formed by the light valve is once formed as an “intermediate image” on the optical paths of the first and second optical systems by the action of the first and second optical systems, and this intermediate image is further enlarged. Projected onto a display surface such as a screen.

In the projection optical system of S1, a negative power for “making the imaging position of the intermediate image close to the reflecting surface having a positive power in the second optical system” on the optical paths of the first and second optical systems is provided. The optical element can be provided on the “light valve side of the intermediate image” (S2). In this case, the second optical system can at least “have a reflecting surface having a positive power and a reflecting surface having a negative power” (S3).

In any one of the projection optical systems S1 to S3, one or more of the reflecting surfaces of the second optical system can be configured as a free-form surface (S4).
In any one of the projection optical systems S1 to S4, it is preferable to form a “reflecting surface having a positive power that first reflects the light beam after forming the intermediate image” as a free-form surface (S5).

  In any one of the projection optical systems S1 to S5 described above, the first optical system can be configured by “only a refractive optical system” (S6), or “a reflective surface having a rotational symmetry axis and a refractive optical system” ("S").

  In the projection optical system of S6 or S7, the refractive optical system can have a “aspherical refractive surface” as a free-form surface (S8).

  The image projection apparatus of S9 is "an image projection apparatus that irradiates a light valve that forms an image according to a modulation signal with illumination light from a light source and enlarges and projects an image formed on the light valve by a projection optical system". The projection optical system for enlarging and projecting the image formed on the light valve has any one of S1 to S8.

  The enlargement projection optical system of S10 guides the light beam from the image display panel to the screen, projects it from a direction inclined with respect to the normal line of the screen, and enlarges the image displayed on the image display panel on the screen. Is an enlarged projection optical system that forms an image.

  The “image display panel” is a light valve (LV) such as various transmissive or reflective liquid crystal panels, a digital micromirror device (DMD), or the like.

The enlargement projection optical system of S10 has the following characteristics.
That is, the enlargement projection optical system has a reflection optical system and a transmission optical system.
The “reflection optical system” is composed of a plurality of reflecting surfaces having power, and includes one or more rotationally asymmetric reflecting surfaces. The “rotationally asymmetric reflection surface” is a reflection surface in which the shape of the reflection surface does not have a rotational symmetry axis.
The “transmission optical system” is constituted by a transmission surface having refractive power and includes one or more aspheric surfaces.

  In the enlargement projection optical system of S10, “a diaphragm is provided between the first surface from the image display panel side in the transmission optical system and the first surface from the screen side in the reflection optical system, and an optical element disposed on the screen side is used. It is preferable that the image of the aperture is formed with a negative reduction magnification ”(S11).

The enlargement projection optical system in S12 has the following characteristics.
That is, it has “a transmission optical system composed of a plurality of transmission surfaces”, “a reflection optical system composed of a plurality of reflection surfaces”, and “aperture”. The power of the reflecting surface having the power incident on is negative.

  In the enlargement projection optical system of S12, it is preferable that the reflecting surface following the “reflecting surface having negative power on which the light beam having passed through the aperture first enters” has positive power (S13).

  The reflecting optical system in the magnifying projection optical system described in S12 or S13 includes “a plurality of reflecting surfaces having power and includes at least one rotationally asymmetric reflecting surface”, and the transmitting optical system includes “a transmitting surface having refractive power. It is preferable to include one or more aspherical surfaces ”(S14).

The magnifying projection optical system according to claim 1 has the following characteristics.
That is, the light flux from the image display panel is guided to the screen and projected from a direction inclined with respect to the normal line of the screen, and an enlarged image of the image displayed on the image display panel is formed on the screen. The magnifying projection optical system includes a `` transmission optical system including a transmission surface having a refractive index and propagating a light beam from the image display panel '' and a `` multiple reflection surface of the plurality of reflection surfaces ''. Of these, the most upstream side has a negative power reflecting surface, and an intermediate image of the negative magnification of the image panel formed on the image side of this negative power reflecting surface is formed on the screen as an upright image of the above image. A reflective optical system for imaging ".

  In the magnifying projection optical system according to claim 1, the transmission optical system has “a plurality of transmission surfaces having a refractive index” and is between the surfaces of the transmission optical system or “between the transmission optical system and the reflection optical system”. It may have a configuration in which a “diaphragm image” is formed at a negative reduction magnification in the optical path of the reflective optical system.

  In the magnifying projection optical system according to claim 2, "the power of the reflecting surface following the reflecting surface having a negative power first incident on the reflecting surface of the reflecting optical system through which the light beam having passed through the stop is positive" is positive. (Claim 3).

  The magnifying projection optical system according to any one of claims 1 to 3, wherein the reflection optical system is constituted by "a plurality of reflection surfaces having power", includes at least one rotationally asymmetric reflection surface, and the transmission optical system is " It is preferably composed of a transmissive surface having a refractive power and including at least one aspherical surface.

  The magnifying projection optical system according to a fourth aspect of the present invention can be “a configuration in which the rotationally asymmetric reflecting surface is disposed on the most screen side in the projection optical path” (Claim 5).

  The magnifying projection optical system according to any one of claims 1 to 5 can be "a transmission optical system includes a rotationally asymmetric transmission surface having refractive power" (claim 6).

  The magnifying projection optical system according to any one of claims 1 to 6, wherein “the optical axis of the transmission optical system is set eccentric with respect to the image display panel position in a plane including the light guide optical path”. (Claim 7). The reflection optical system in the magnification projection optical system according to any one of claims 1 to 7 can be “configured as a unit” (claim 8).

  The magnifying projection apparatus according to claim 9 displays an image on an image display panel, illuminates the image display panel with light from a light source, and guides a light beam from the illuminated image display panel to a screen by an magnifying projection optical system. And an enlarged projection device that projects an enlarged image of the image displayed on the image display panel on the screen by projecting from a direction inclined with respect to the normal line of the screen, and as an enlarged projection optical system. The magnifying projection optical system according to any one of 1 to 8 is used.

When supplementing the inventions of claims 1 to 9 slightly, the “transmission surface” included in the “transmission optical system” described above may be not only a lens surface but also a Fresnel lens surface.
In addition, a configuration in which the reflection of light on the reflection surface included in the reflection optical system satisfies the “total internal reflection condition” may be employed. As described above, when the reflection surface is the “total internal reflection surface”, the “surface that takes in the light beam from the transmission optical system” is the transmission surface. In this case, it is preferable to make the light beam incident on the transmission surface perpendicular to the surface because no aberration occurs during the incidence.

  The “image display panel” used in the magnifying projection apparatus is not limited to one. Using three image display panels, each R (red), G (green), and B (blue) color component image is displayed on a “different image display panel” for each color, and light from these image display panels is displayed. Needless to say, the image can be synthesized and guided to the screen by the enlarged projection optical system, and a color image can be displayed on the screen.

  In the magnifying projection optical system of the present invention, the imaged light beam is projected from the direction inclined with respect to the screen normal, and is imaged on the screen. It is possible to effectively reduce the “distortion of the display image that occurs when tilted with respect to the screen normal”.

  In addition, the transmission surface having the refractive power of the transmission optical system can be easily realized by a lens system, can be easily made into a cell, and can be easily assembled, resulting in a cost reduction effect. Further, an asymmetrical aberration component can be corrected by the rotationally asymmetric reflecting surface included in the reflecting optical system.

  If the magnifying projection optical system is configured with only the refracting surface, the arrangement of the refracting surfaces extends in one direction, so the three-dimensional structure of the optical system cannot be reduced in size, but the optical path is folded by the combination of the transmitting surface and the reflecting surface. The optical system can be miniaturized.

  For example, if the optical path of the transmission optical system is set parallel to the screen and the optical path is bent toward the screen on the image side of the transmission optical system, a thin configuration can be realized even with an optical system having the same optical path length.

  Like the enlarged projection optical system of S1, a diaphragm is disposed between the first surface on the image display panel side in the transmission optical system and the first surface on the screen side in the reflection optical system, and by the light beam from the panel side, When the image of the aperture is formed once in the entire optical system, the image formation position of the aperture image becomes the exit pupil on the screen side. The aperture image is a real image and has a negative reduction magnification. By forming the image of the aperture at a reduced magnification, the effective diameter of the light beam on the reflective surface after the aperture image can be kept small, and the size of the reflective surface can be reduced.

  The stop can be arranged in the transmission optical system or “between the transmission optical system and the reflection optical system”. The “reflecting surface having power” on which the light passing through the stop first enters is in the reflecting optical system. It is difficult to integrate the reflection optical system and the transmission optical system, and the transmission optical system and the reflection optical system are assembled separately. At this time, since an assembly error is attached to each of the transmission optical system and the reflection optical system, it is difficult to completely eliminate the “relative displacement” of both optical systems, and it is assumed that relative displacement occurs. Then, from the viewpoint of tolerance sensitivity, the “power reflecting surface” is preferably a negative power reflecting surface.

  The case where the light beam emitted from the transmission optical system is a divergent light beam is rare, and is usually condensed. At this time, if the power of the surface having the first reflected power in the reflective optical system is positive, it acts in the direction in which the light beam is more focused. On the other hand, if the power of the surface is negative, it acts in a direction in which the light beam is condensed. When both are compared, the “change in the state of the light beam due to the relative positional deviation between the transmission optical system and the reflection optical system” is large in the former, and the assembly tolerance becomes severe. By making the power of the reflecting surface negative, the assembly tolerance can be relaxed.

  If a reflecting surface having a positive power is arranged subsequent to the reflecting surface having a negative power, separation of light beams having different angles of view can be suppressed, and the reflecting surface that receives these light beams can be miniaturized.

  In addition, by making the shape and position of the intermediate image of the aperture and the screen substantially coincide, the sum of the distortion aberration from the image display panel to the intermediate image and the distortion aberration from the intermediate image to the screen can be brought close to zero. An image with less distortion can be formed on the screen.

  If the final surface on the imaging optical path is a rotationally asymmetric reflecting surface as in the fifth aspect of the invention, the degree of freedom of the surface shape that can be taken corresponding to the irradiation position of each light beam is increased. The residual aberration of the light flux at each image height position reaching the final surface is easily corrected by giving a shape suitable for each incident position.

  When a rotationally asymmetric transmission surface is used in the transmission optical system as in the sixth aspect of the invention, an aberration that cannot be generated by the rotationally symmetric transmission surface can be generated. It can be used to cancel other aberrations.

  If the optical axis of the transmissive optical system is decentered within the plane including the light guide optical path with respect to the position of the image display panel as in the seventh aspect of the invention, it is generated on the decentered reflective surface in the reflective optical system. Aberrations opposite to the generated aberrations can be generated in the transmission optical system, and both can be canceled.

The projection optical system in S15 has first and second optical systems.
The “first optical system” includes at least one refractive optical system and has a positive power.

  The “second optical system” includes at least one reflecting surface having power, and has a positive power as a whole.

  These first and second optical systems are arranged in the order of the first and second optical systems from the side close to the object plane, so that the object image is once formed as an intermediate image and then formed as a normal image. Configured.

The projection optical system of S15 has the following characteristics.
That is, in the first optical system, the other optical element is decentered in parallel and / or tilted at one or more positions with respect to the optical axis of “the optical element having the refractive power closest to the object side”. Yes. That is, parallel eccentricity or tilt eccentricity is performed in “optical element units”.

The projection optical system in S16 has first and second optical systems.
The “first optical system” includes at least one refractive optical system and has a positive power.

  The “second optical system” includes at least one reflecting surface having power, and has a positive power as a whole.

  These first and second optical systems are arranged in the order of the first and second optical systems from the side close to the object plane, so that the object image is once formed as an intermediate image and then formed as a normal image. Configured.

The projection optical system of S16 has the following characteristics.
That is, in the first optical system, each element of the first optical system is not “tilt decentered” with respect to the optical axis of “an optical element having a refractive power closest to the object side”.

  In the projection optical system of S16, “the first optical system is composed of two or more groups, and at least one of the two or more groups is parallelly decentered” (S17). .

  In any one projection optical system of S15 to S17, it is preferable that at least one of the reflecting surfaces included in the second optical system is a “free curved surface” (S18). In this case, among the reflecting surfaces included in the second optical system, “only the reflecting surface closest to the normal image forming position side” can be a free-form surface (S19).

  In any of the projection optical systems of S15 to S19, it is preferable that the “reflecting surface having a positive power on which the light beam incident on the second optical system is reflected for the first time” be a rotationally symmetric surface (S20). In this case, the rotationally symmetric reflecting surface can be a “spherical reflecting surface” (S21).

  In any one of the projection optical systems of S15 to S21, “the first optical system is configured only by the refractive optical system” can be performed (S22). In this case, the refractive optical system in the first optical system can be “not including an aspheric shape” (S23).

  The image projection apparatus in S24 is an image projection apparatus that guides a light beam from an image display panel to a screen by a projection optical system, and forms a normal image of the image displayed on the image display panel on the screen. As an optical system, the projection optical system according to any one of S15 to S23 is mounted.

  To supplement a little about the invention described in S15 to S24, in the image projection apparatus using the projection optical system described in S15 to S23, as an object for displaying a projected object image, a light valve such as a liquid crystal panel, Of course, it is possible to use image display means that is illuminated with light from an external light source such as DMD and slide film, as well as two-dimensionally arranged light emitting diodes, plasma displays, EL light emitting element arrays, etc. Needless to say, self-luminous image display means can be used.

  In addition to the lens, the “refractive optical system” can also be a “light transmission element exhibiting a diffractive action”.

Hereinafter, other reference techniques similar to the present invention will be described as reference techniques SS1 to SS13.
The projection optical system of the reference technology SS1 “projects the light beam from the object surface to be projected onto the projection surface via the transmission refractive optical system and the reflective refractive optical system including one or two reflecting mirrors. Projection optical system "having the following characteristics.

  The “transmissive refractive optical system” has a plurality of transmissive refractive elements.

  “Transmissive refraction element” means “all optical elements that exhibit a refractive action of light at the boundary surface of a light-transmitting medium”, and a typical element is a lens. It can also be a “transmission element”.

  The reflection mirror that forms the “reflection-type refractive optical system” means all optical elements that exhibit the catadioptric action of light at the reflection boundary surface, and can also be a “light-reflective optical element that exhibits a diffraction action”.

  The distance from the projection object surface to the first surface of the transmissive refractive optical system is substantially telecentric.

  The “projected object plane” is a plane on which an image to be projected is displayed as an object, and what constitutes the substance of this plane is a light valve such as a liquid crystal panel, a DMD, a slide film, etc. It is possible to use an image display means that is illuminated with light from an external light source, and furthermore, a self-luminous image display such as a two-dimensional array of light emitting diodes, a plasma display, an EL light emitting element array, etc. Means can be used.

  The intermediate image plane of the object surface to be projected is located closer to the reflective refractive optical system than the transmissive refractive optical system, and the intermediate image on the intermediate image plane is re-imaged as a normal image on the projection plane via the reflecting mirror. Is done.

At least one reflection mirror (if the reflection type refractive optical system is constituted by one reflection mirror, the reflection mirror; if the reflection type refractive optical system is constituted by two reflection mirrors, one or more reflection mirrors; The reflection mirror is an anamorphic polynomial free-form surface having different powers in the vertical direction and the horizontal direction.
Light rays from the reflective refractive optical system to the projection surface are guided with an inclination with respect to the normal line of the projection surface.

  The transmission refractive optical system is decentered with respect to the normal line of the projection object surface, and the plurality of transmission refractive elements included in the transmission refractive optical system are configured without being decentered from each other.

  The projection optical system of the reference technology SS2 “projects the light beam from the object surface to be projected onto the projection surface via the transmission type refractive optical system and the reflection type refractive optical system composed of one or two reflecting mirrors. A transmissive refractive optical system having a plurality of transmissive refracting elements, and substantially telecentric from the projection object surface to the first surface of the transmissive refractive optical system. An intermediate image plane of the object surface to be projected is positioned on the reflective refractive optical system side of the system, and the intermediate image on the intermediate image plane is re-imaged as a normal image on the projection plane via the reflection mirror, and at least 1 The reflecting mirrors are anamorphic polynomial free-form surfaces with different powers in the vertical and horizontal directions. Light rays from the reflective refractive optical system to the projection surface are guided with an inclination with respect to the normal line of the projection surface. Is the same as the projection optical system of Reference Technology S1. .

  The feature of the projection optical system of the reference technology SS2 is that “the transmission refractive optical system is decentered with respect to the normal of the object surface to be projected, and the plurality of transmission refractive elements included in the transmission refractive optical system are in group units. The level is configured without being eccentric from each other. "

  The projection optical system of the above-mentioned reference technique SS1 or SS2 is “a catadioptric refractive optical system has two reflecting mirrors arranged in the first and second order from the transmission refractive optical system side, and the object to be projected An intermediate image plane is positioned between the first and second reflecting mirrors, the first reflecting mirror is an axisymmetric reflecting surface with negative power, and the second reflecting mirror is powered in the vertical and horizontal directions. Can be different anamorphic polynomial free-form surfaces (Reference Technology SS3).

  The projection optical system of the reference technology SS1, SS2, or SS3 is an anamorphic that has different powers in the vertical and horizontal directions in the transmissive refractive optical system as “a means for correcting the aspect ratio of the intermediate image of the projection target surface”. A polynomial free-form surface (reference technique SS4).

  It is not impossible to perform the “aspect ratio of the intermediate image” by the shape of the reflection mirror of the reflective refractive optical system. However, it is desirable to determine the shape of the reflection mirror of the reflective refractive optical system mainly with distortion correction as the center. Therefore, it is desirable that the aspect ratio can be adjusted in advance in the transmissive refractive optical system, and it is effective to use the polynomial free-form surface as means for correcting the aspect ratio in the transmissive refractive optical system.

  The adoption of a polynomial free-form surface in a transmissive refractive optical system is not limited to one surface, but in a reference specific example described later, a sufficient correction effect can be obtained by using only one polynomial free-form surface in a transmissive refractive optical system. It was. The polynomial free-form surface employed in the transmissive refractive optical system may be employed at a position close to the projection object surface, but is preferably employed at a position close to the projection surface side in order to enhance the correction effect. Incidentally, in the reference specific example, a polynomial free-form surface is adopted as the final surface of the transmissive refractive optical system.

  Any one of the projection optical systems of the reference techniques SS1 to SS4 preferably has “the NA on the projection object surface side in the transmissive refractive optical system is larger than the NA on the intermediate image plane side” (reference technique SS5).

  When a transmissive refractive optical system is configured, the NA on the projection object plane side (referred to as “NA1”) is determined by the orientation distribution characteristics of the illumination system, but the NA on the intermediate image plane side (referred to as “NA2”). Can be changed depending on the arrangement of the transmissive refractive optical system. In order to increase the projection magnification, it is effective to increase the power of the reflective refracting optical system. However, if this is done, the focal length of the image side of the reflective refracting optical system is shortened. It is closer to the reflection mirror side of the reflection type refractive optical system, so that only a small-sized regular image can be formed, that is, the enlargement magnification is reduced. In order to clear this problem, attention was paid to the NA2 of the light beam incident on the reflective refractive optical system, and it was found that making NA2 smaller than NA1 had a special effect in increasing the projection optical system magnification. It was.

  In any one of the projection optical systems of the above-described reference techniques SS1 to SS5, the intermediate image plane can be “inclined and curved with respect to the principal ray of the light beam emitted from the center of the projection target surface” (reference technique SS6). ). In this way, the degree of freedom with respect to the intermediate image plane is increased, and the design of the entire optical system is facilitated.

  In any one projection optical system of the reference technologies SS1 to SS6, “a principal ray emitted from the center of the projection object surface and a principal ray emitted from the periphery of the projection object surface on the final surface of the transmission type refractive optical system; Are preferably substantially parallel "(Reference Technique SS7).

  In any one projection optical system of the reference techniques SS1 to SS7, “intermediate image magnification: M1 is about 1 to 5” is preferable (reference technique SS8). In any one projection optical system of the reference techniques SS1 to SS8, the projection magnification can be 40 or more (reference technique SS9). In this case, it is preferable that the projection angle: θ with respect to the projection plane is larger than 5 ° (reference technique SS10).

  In order to realize an enlargement projection optical system for enlarging and projecting an image of an object surface of 0.9 inch diagonally on a 60 inch screen with “thinness: 500 mm or less”, the NA2 is about 0.005 to 0.01. It turned out that it would be good to be. If NA2 is made too small, the entire length of the transmissive refracting system is extended. Therefore, considering that the overall size of the apparatus is reduced, NA2 is preferably about 0.005 to 0.01.

  When NA2 is 0.01 or more, the transmission type refraction system becomes compact. However, as NA increases, it tends to be difficult to correct distortion of the projection screen or to ensure magnification performance. Of course, when the screen size is smaller than 60 inches, the upper limit of NA2 may be 0.01 or more.

  The image projection apparatus of the reference technique SS11 is an “image projection apparatus that enlarges and projects an image displayed on the projection object surface onto the projection surface by the projection optical system”, and any of the reference techniques SS1 to SS10 is used as the projection optical system. 1 is used. The image projection apparatus of the reference technology SS11 can be configured as a front projector type (reference technology SS12), or can be configured as a rear projector type having a folding mirror that folds the imaging optical path (reference technology SS13). It goes without saying that the image projectors described in other claims can be similarly made into a front projector type and a rear projector type.

In the above description, the “anamorphic polynomial free-form surface having different power in the vertical direction and the horizontal direction” refers to the vertical direction (considering the vertical direction and the horizontal direction based on the projected image) as the Y direction and the horizontal direction. The direction is the X direction, the depth of the curved surface is Z, and "X2, Y2, X2Y, Y3, X2Y2, etc."
^{Z = X2 · x 2 + Y2} · y 2 + X2Y · x 2 y + Y3 · y 3 + X4 · x 4 + X2Y2 · x 2 y 2 + Y4 · y 4 +
X4Y · x ⁴ y + X2Y3 · x ² y ³ + Y5 · y ⁵ + X6 · x ⁶ + X4Y2 · x ⁴ y ² + X2Y4 · x ² y ⁴ + Y6 · y ⁶ + · · (1)
It is a shape represented by.

As described above, according to the present invention, a novel projection optical system, enlarged projection optical system, enlarged projection apparatus, and image projection apparatus can be realized.

  Any one projection optical system of S1 to S8 is composed of the first and second optical systems, and an image formed by the light valve is formed as an intermediate image on the optical path of the first and second optical systems. Since this intermediate image is further magnified and projected, a large projection magnification can be realized, and the first optical system includes a refractive optical system. Therefore, even when a color synthesis prism is used, color dispersion characteristics are used. Chromatic aberration correction is possible, and the optical path of the imaging light beam is folded back by the reflecting surface included in the second optical system, so that a compact configuration can be achieved.

  Therefore, the image projection apparatus of S9 can be configured compactly, and the optical path of the imaging light beam can be made long in the apparatus space, so that a large-size image can be projected and displayed while reducing the projection space outside the apparatus.

  An enlarged projection optical system according to any one of claims 1 to 9 can project an image on an image display panel on a screen as a “large screen with little distortion”. The enlargement projection device used can be made thin.

  In the projection optical system described in any one of S15 to S23, an intermediate image is formed by the first optical system, and enlarged projection is performed by the second optical system, thereby increasing the magnification of the synthesis of the optical system. In addition, by adding a refractive optical system to the first optical system, even when a color separation prism is used, chromatic aberration correction can be performed using chromatic dispersion characteristics. Further, by causing the lens elements constituting the refractive optical system to be decentered in parallel or tilt, it is possible to “effectively generate reverse distortion in the intermediate image” so as not to cause distortion in the projected image. Therefore, the image projection apparatus of S23 can project at a close distance at a desired magnification.

  Further, any one projection optical system of the reference technologies SS1 to SS10 can project a large screen without distortion, and the image projection apparatus of the reference technologies SS11 to SS12 can be configured to be thin.

  FIG. 1 schematically shows a main part of the first embodiment of the image projection apparatus.

  A “light valve” indicated by reference numeral 15 is a liquid crystal panel in this embodiment, and is simply referred to as a panel 15 hereinafter. A light source indicated by reference numeral 10 is composed of a light emitting unit 11 including a lamp and a reflector, and an illumination optical system 12 that uses a light beam from the light emitting unit 11 as an illumination light beam. The illumination light beam from the light source 10 is applied to the panel 15.

  The panel 15, which is a light valve, is “image-formed according to the modulation signal”, and the formed image transmits the illumination light beam from the light source 10 in two-dimensional intensity modulation. The light beam transmitted through the panel 15 is projected and imaged on the screen 21 by a “projection optical system” constituted by the first optical system 17 and the second optical system 19, and “an image formed on the panel 15”. A magnified image of is displayed.

  FIG. 2 is a diagram for explaining a portion of the projection optical system in FIG.

  On the projection side of the panel 15, which is a light valve, there are first and second optical systems 17 and 19 arranged in the first and second order from the panel 15 side. The first optical system 17 is refracted. The optical system (lens) has positive power, and the second optical system 19 has a reflecting surface having power and has positive power.

  The image formed by the panel 15 is formed as an intermediate image Iint on the optical paths of the first and second optical systems 17 and 19, and an “image obtained by further enlarging the intermediate image Iint” is formed on the screen 21. Projected and imaged.

  Although the first optical system 17 is shown as one lens in FIG. 2, specifically, “various forms including refractive optical system”, for example, a configuration using a plurality of lenses, a combination of a lens and a mirror, A configuration in which the reflecting surface and the refracting surface are integrated is possible as appropriate.

  The first optical system 17 has a positive power as a whole, and as shown in FIG. 2, the intermediate image Iint formed by the first optical system 17 is “formed on the panel 15. “An inverted image”. The magnification of the intermediate image Iint is preferably about 1 to several times that of the image on the panel 15. When the intermediate image Iint is a reduced image, in order to obtain a “display image with a large magnification” as the entire first and second optical systems, a large magnification is required for the second optical system, and aberration correction is performed. It becomes difficult to achieve a balance between the large magnification and the like.

On the other hand, if the magnification of the intermediate image Iint is too large, the size of the second optical system is increased, and the projection optical system, and hence the image projection apparatus, is increased in size.

  In FIG. 2, from positions A and B on the panel 15 corresponding to two points of the maximum image height on the + side (position: a in FIG. 1) and the maximum image height on the − side (position: b in FIG. 1). The optical path of the light beam which goes to the said position: a and b is shown typically.

  The intermediate image Iint does not necessarily have to be “planarly formed”, and the image projected on the screen 21 by the composite optical system of the first optical system 17 and the second optical system 19 is “a satisfactory image”. It is only necessary to ensure the performance of the synthetic optical system as a whole. Accordingly, there is no particular restriction on the imaging performance by the first optical system 17.

  In the embodiment shown in FIG. 1 and FIG. 2, the light beam formed by forming the intermediate image Iint formed by the first optical system 17 is reflected by the second optical system 19 and the optical path is turned back. The projection image is projected in the direction opposite to the traveling direction of the light beam forming Iint.

  In the embodiment of FIGS. 1 and 2, the second optical system 19 is an example of a single concave mirror. However, the form of the second optical system is not limited to this, and includes two or more reflecting surfaces. It is also possible to include a refractive optical system together with the reflecting surface.

  In the configuration of FIGS. 1 and 2, the direction of the finally projected light beam is made “reverse to the direction of FIG. 1” by “adding one more reflective surface” to the second optical system. You can also. 1 and FIG. 2, a refractive optical system (lens system) is arranged as a part of the second optical system between the position where the intermediate image Iint is formed and the reflecting surface 19, and reflection is performed. The surface 19 can be “captured light more efficiently”.

  As shown in FIG. 2, the light beam starting from the position A on the panel 15 is gathered so as to have a center of gravity at the position A ′ in the intermediate image Iint, and the condensed light beam has the same divergence angle as the convergence angle. And is reflected by the second optical system 19 having a positive power, and forms an image at a position a on the screen 21 in FIG.

  Similarly, the light beam starting from the position B on the panel 15 gathers so as to have the center of gravity at the position B ′ in the intermediate image Iint, and the condensed light beam spreads at the same divergence angle as the converging angle. Is imaged at a position b on the screen 21 in FIG.

  By forming the intermediate image Iint, it is possible to “locally narrow” the effective area of the reflecting surface 19 that contributes to the image formation of the light beams from the positions A and B on the panel 15. That is, as shown in FIG. 2, the imaging performance with respect to the light beam from the position: A is affected by the shape of the “reflection area A ″” of the second optical system 19, and the connection with respect to the light beam from the position: B is affected. The shape of the “reflection area B ″” affects the image performance.

Therefore, it is possible to optimize the surface shapes of the reflection regions A ″ and B ″ by the configuration shown in FIGS. Furthermore, the condensing characteristic to each part on the screen 21 can be controlled by “locally changing” the shape of the concave surface in the second optical system 19.
In particular, the effect can be maximized by making the concave surface a free-form surface.

  What is necessary is just to perform optimal specification setting by simulation methods, such as the ray tracing method known conventionally. Since the optimization can be performed by the reflecting surface, it is possible to design to improve the other light collecting characteristics while suppressing the occurrence and increase of chromatic aberration.

  Since the first optical system 17 includes a refractive optical system, it is possible to correct “a chromatic aberration that cannot be corrected only by the reflecting surface” by the refractive optical system.

  Further, various aberrations that affect the projected image projected on the screen 21 and cannot be corrected only by the reflecting surface of the second optical system are corrected by actively incorporating a refractive optical system into the second optical system. You may do it.

  In the configuration shown in FIG. 1, in order to increase the imaging magnification of the second optical system 19, the position where the intermediate image Iint is formed should be close to the reflecting surface of the second optical system 19. This will be described with reference to FIGS.

  In FIG. 3, reference numeral 15 denotes a panel, reference numeral 17A denotes a first optical system (lens), reference numeral 19A denotes a second optical system (concave mirror), and reference numeral 21 denotes a screen.

  In accordance with the notation of the optical system, the radius of curvature of the i-th surface counted from the panel side is Ri (i = 1 to 3 where i = 1 is the incident side surface of the first optical system 17A, and i = 3 is the first side. 2), the distance between the i-th surface and the (i + 1) -th surface is Ti (i = 0 to 3 i = 0 is the incidence of the panel 15 and the first optical system 17A). (Between the side surfaces, i = 3 is between the second optical system 19A and the screen 21).

The specifications of the optical system in FIG. 3 are as follows.
i Ri (mm) Ti (mm) Material 0 85
1 65 25 BK7
2-55 225
3-135-400.

  The object height in the panel 15 is ± 7.5 mm.

  If the projection image is set to be optimally formed at the image height position 0 (point P on the screen 21), the position on the screen 21: a, b starting from the position: A, B on the panel 15 as an object. The distance between the chief rays reaching the beam is about 208 mm.

Here, as shown in FIG. 4, the first optical system 17B and the second optical system 19B are used, the power of the first optical system 17B is relaxed, and the position of the intermediate image Iint is shifted from the first optical system 17B. When the positive power in the second optical system 19B is adjusted while maintaining the positional relationship so that the condensing property at the image height of 0 is maintained at the same time, the specifications of these optical systems are as follows: It becomes like this.
i Ri ′ (mm) Ti ′ (mm) Material 0 85
1 65 25 BK7
2-60 225
3-98-400.

  The object height in the panel 15 is ± 7.5 mm.

  4 illustrates the optical arrangement different from that of FIG. 3 for the sake of explanation. As is apparent from the above description, the arrangement of the optical system is the same as that of FIG. The only difference is the curvature of the exit side surface of the first optical system 17B and the curvature of the reflection surface of the second optical system 19B.

  At this time, with the positions on the panel 15: A, B as the starting points, the distance between the principal rays reaching the positions: a ′, b ′ on the screen 21 is about 362 mm, which is larger than the case shown in FIG. 3 (208 mm). The rate has improved. That is, the positive power in the first optical system is weakened and the intermediate image Iint approaches the “reflecting surface having positive power” of the second optical system 19B. As a result, the enlargement ratio is increased. As described above, the enlargement ratio can be improved only by changing the radius of curvature of the refracting surface / reflecting surface without changing the optical arrangement.

  In order to embody the above description, on the optical paths of the first and second optical systems, “to bring the image formation position of the intermediate image closer to the reflecting surface having positive power in the second optical system, An “optical element having negative power” may be provided on the light valve side of the intermediate image (S2).

  In order to bring the position of the intermediate image closer to the reflecting surface having a positive power in the second optical system, an optical element having a negative power provided on the light valve side of the intermediate image may be a concave lens, a Fresnel concave lens, a convex reflection A mirror or a composite system of these can be considered.

  Actually, it is necessary to secure the condensing characteristics at each image height position and correct the distortion of the image plane, but by increasing the number of refracting and reflecting surfaces to increase the degree of freedom of design, etc. Optimization design may be performed by simulation using a ray tracing method known from the above.

FIG. 5 schematically shows an embodiment of S3. In order to avoid complications, the same reference numerals as those in FIG.
In this embodiment, the second optical system 190 includes a reflective surface 192 having a positive power and a reflective surface 191 having a negative power.

  The light beam from the panel 15 becomes an imaged light beam by the action of the first optical system 17. However, before the intermediate image Iint is formed, the light beam enters the reflecting surface 191 having a negative power and travels toward the reflecting surface 192. And reflected. The intermediate image Iint is formed at an intermediate portion between the reflecting surface 191 and the reflecting surface 192. The intermediate image Iint is further magnified by the positive power of the reflecting surface 192, and the image on the panel 15 is projected onto the screen 21.

  That is, the reflecting surface 191 in the second optical system 190 has a negative power having an effect of bringing the position where the intermediate image Iint is formed in S2 closer to the reflecting surface 192 having the positive power of the second optical system 190. This is an example of an “optical system having a”.

  As the reflecting surface 191, a reflecting optical element having a diverging power, such as a convex reflecting surface, a Fresnel convex reflecting mirror, or a hologram reflecting mirror having a positive power, can be used as appropriate.

  In order to move the position of the intermediate image away from the light valve, the projection optical system must be somewhat larger, but by constructing the above "optical system with negative power" with a reflecting mirror, a layout that turns the optical path back. It can be adopted, and the size of the entire optical system can be reduced.

  The “optical element having a negative power for bringing the imaging position of the intermediate image close to the reflecting surface having a positive power in the second optical system” described in S2 and S3 can be used as a “second optical element”. It is possible to make adjustments to narrow the “degree of divergence” of the incident light beam onto the “reflecting surface having positive power in the optical system”, and to reduce the “effective reflection area” of the reflecting surface having positive power. Become.

By adjusting the effective reflection area of the reflecting surface having the positive power and providing the shape of the reflecting surface locally, that is, “setting of a free-form surface”, the light condensing characteristics and distortion can be controlled more finely.
By adopting the configuration as described above, a wider angle can be obtained than in the conventional projection optical system.

  By configuring at least one of the various reflecting surfaces described in the above embodiment as a free-form surface, the degree of freedom in design is increased and various aberrations can be easily corrected (S4).

  The so-called “free-form surface” is a surface including “non-rotationally symmetric surface shape” such as an anamorphic surface or an XY polynomial surface.

  If all surfaces (refractive surfaces, reflective surfaces) included in the projection optical system are configured by free-form surfaces, extremely good imaging characteristics can be realized in terms of design. Since the required accuracy such as the core error becomes severe, the larger the number of free-form surfaces, the better. It is better to set the optimal number of free-form surfaces.

  As described above, the light beam forming the intermediate image Iint becomes a divergent light beam, and enters a reflecting surface (concave mirror) having a positive power in the second optical system. Accordingly, the divergent light beam from each position of the intermediate image Iint is reflected by the local reflection region of the concave mirror and forms an image on the screen. In other words, the light beam that forms an image at each position on the screen corresponds to a “local reflection region for each image height” in the concave mirror.

  For this reason, the surface of the concave mirror (the reflecting surface on which the light beam that formed the intermediate image is reflected first after the intermediate image is formed) is a free-form surface, and the curved surface of the reflecting surface for each “reflection region for each image height”. By adjusting the shape, various aberrations can be corrected most effectively and performance can be improved (S5).

  Considering surface processing and assembly, the number of free-form surfaces should be as small as possible, and it is most effective to preferentially apply to a reflecting surface (concave mirror) having a positive power immediately after forming an intermediate image. . In addition to the adjustment of the reflection region, the shape setting of “a free curved surface capable of adjusting the local shape of the concave surface having the light condensing power” enables the design to further improve the characteristics such as the light condensing characteristic and the image distortion.

  The magnification of the intermediate image only needs to be “approximately 1 to several times”, and the imaging magnification of the first optical system related to the formation of the intermediate image does not need to be large. Therefore, the first optical system has been conventionally used. Optimization is possible with a configuration (S6) using only a certain refractive optical system. If the first optical system is composed only of a refractive optical system, the optical design of the first optical system is facilitated, and the tolerances can be relaxed with respect to surface processing and assembly.

  It is also possible to increase the number of refracting surfaces and the like to increase the degree of design freedom, thereby distributing tolerances and improving performance.

  In S6, the first optical system is configured by “only refractive optical system”. However, if further improvement in performance is desired, it is necessary to “further improve the degree of freedom in the configuration of the first optical system”.

  In order to further improve the performance as described above, the first optical system may be “configured by a reflecting surface having a rotationally symmetric axis and a refractive optical system” (S7). A “reflecting surface having a rotationally symmetric axis” is relatively easy to make and is extremely effective in improving the degree of freedom in design without impairing workability and assembly. The degree of freedom is further improved by making the reflecting surface having the rotational symmetry axis an aspherical surface. In addition, by providing the reflecting surface with a degree of freedom of shift eccentricity and tilt eccentricity, a design with improved degree of freedom becomes possible.

  An aspherical shape can also be used in the refractive optical system. By adopting such a configuration, the degree of freedom in design is improved, and a higher performance projection optical system can be realized.

  Various processing methods such as a conventionally known polishing process, a molding process using a mold, and a precise shape transfer process can be employed for processing the reflecting surface. Further, the refractive transmission surface and the reflection surface may be integrated to form an internal total reflection structure.

With reference to FIG. 1, one embodiment of an image projection apparatus will be described.
As the lamp of the light emitting unit 11 in the light source 10, a halogen lamp, a xenon lamp, a metal halide lamp, an ultrahigh pressure mercury lamp, or the like can be used.

  In order to obtain high illumination efficiency, a reflector provided integrally with the lamp is used in the vicinity of the lamp. Although not shown in FIG. 1, “a well-known illuminance uniformizing unit called an integrator optical system” is used so that a “directed light beam” reflected by a reflector can be irradiated onto the panel 15 with uniform light intensity. Can be used to illuminate the panel surface with a uniform illumination distribution.

  In the case of using a “reflective liquid crystal light valve” instead of the transmissive liquid crystal panel 15 illustrated as a light valve in FIG. 1, a polarization beam splitter or the like is used to separate the illumination optical path from the projection optical path. "Efficient lighting" is possible.

  Further, when a “digital micromirror device (DMD)” is used as a light valve, an “optical path separation optical system using an oblique incident optical system or a total reflection prism” is used. Thus, an appropriate optical system can be employed according to the type of light valve.

  In a front type projector, it is preferable to shift the projection image upward so that the projection image is not shaded by the projector. That is, the light valve 15 is shifted (downward in the figure) in a plane perpendicular to the optical axis of the projection optical system (the optical axis of the first optical system 17), and the light beam enters from below the projection optical system. I try to let them.

  As the shift amount of the light valve 15 increases, it is necessary to increase the effective angle of view as a specification required for the first optical system 17. The above-mentioned shift amount of the light valve 15 is set to an appropriate size as necessary, the intermediate image Iint is once formed by the first optical system 17, and the light valve is formed by the second optical system 19 having a positive power. The image formed at 15 is projected on the screen 21 in an enlarged manner.

  In the rear pro type, it is natural that a plane mirror can be arranged in the projection optical path, and the optical path can be bent to further reduce the space occupation ratio.

  For the sake of simplicity, only one panel 15 is shown above, but three panels for red, green, and blue are used, and light beams modulated by each panel are combined with a known dichroic prism or other color composition. Needless to say, a color image can be projected onto the screen 21 by entering the first optical system 17 and the like after color synthesis by means.

  Embodiments relating to the inventions described in S10 to S14 and claims 1 to 9 will be described below.

  In the embodiment shown in FIG. 6, the reference beam of the light beam group directed from the image display panel indicated by reference numeral 1 (hereinafter simply referred to as panel 1) to the “screen” indicated by reference numeral 2 has a normal line and a predetermined inclination. Incident on the screen 2. The “reference light beam” is the principal light beam of the light beam guided from the center of the panel 1 to the screen 2.

  The panel 1 is a reflective liquid crystal panel, and linearly polarized illumination light is irradiated through the polarizing beam splitter 10A, and the light beam modulated by the panel 1 becomes an image forming light beam through the polarizing beam splitter 10A.

  In the light propagation, when the panel 1 side is called “upstream” and the screen 2 side is called “downstream”, the transmission optics includes “a transmissive surface having refractive power and including one or more aspheric surfaces” on the downstream side of the panel 1. The system 3 is arranged, and a “reflection optical system” having a plurality of reflecting surfaces 4, 5, 6, 7, 8 is arranged downstream thereof.

  The imaging light beam from the panel 1 propagates through the transmission optical system 3 and is guided to the screen 2 through the reflection surfaces 4 to 8 constituting the reflection optical system. Of the reflecting surfaces 4 to 8 constituting the reflecting optical system, the reflecting surface 8 is a “rotationally asymmetric reflecting surface”.

  Although it is preferable to give the light beam condensing function to the transmission optical system 3, in this embodiment, the "loading magnification magnification" in the transmission optical system 3 is relaxed, and in particular, "the diameter of the lens on the downstream side is not increased. " Accordingly, the magnification optical function as the magnification projection optical system is entirely or substantially equivalent to the reflection optical system.

  The rotationally asymmetric reflecting surface 8 corrects “asymmetrical aberration (in the figure, aberration due to asymmetry in the vertical direction of the reference axis)” and decenters the optical axis of the transmission optical system 3 with respect to the panel 1. By setting (in this embodiment, the optical axis is decentered upward in the figure from the center of the panel 1), the correction effect of the asymmetric aberration is enhanced. That is, both the transmission optical system 3 and the reflection optical system are “shared in the correction of asymmetric aberration”.

The transmission optical system 3 is assembled “coaxially” to facilitate cell formation.
As in this embodiment, when the magnifying projection optical system is configured with a transmission optical system and a reflection optical system, it becomes easier to assemble the optical system than when all the optical surfaces are configured with reflection surfaces. The “folding effect” can also be utilized, and the entire system can be reduced in size.

  A “diaphragm” indicated by reference numeral 9 is provided on the downstream side of the transmission optical system 3 and upstream of the reflection surface 4, and the image I 9 of the aperture 9 is “negative reduction magnification” by the reflection surface downstream of the aperture 9. An image is formed on the imaging optical path. That is, the “reduction magnification image I9” of the stop 9 is formed as an inverted image between the reflecting surface 7 and the rotationally asymmetric reflecting surface 8 by the action of the reflecting surfaces 4, 5, 6, and 7 of the reflecting optical system.

  In this way, when the power is arranged such that the image I9 of the stop 9 is formed at a reduction magnification, the light enters the reflecting surface (the reflecting surface 8 in the embodiment being described) on the downstream side of the image I9 of the stop 9. The reflecting surface can be reduced in size because the luminous flux does not spread greatly.

  As described above, the image I9 of the stop 9 is imaged in the optical path of the reflecting optical system (between the reflecting surface 7 and the rotationally asymmetric reflecting surface 8). That is, it becomes the “exit pupil” of the magnifying projection optical system.

  The imaging light beam forms an intermediate image of the panel 1 on the optical path in the reflection optical system. This intermediate image is a “real image with a negative magnification” and is an isometric image, like the image I9 of the stop 9. In the embodiment shown in the figure, the intermediate image of the panel 1 is formed near the reflecting surface of the reflecting surface 7. That is, the intermediate image of the panel 1 is formed by the transmission optical system 3 and the reflection surfaces 4 to 6.

  The image formed on the screen 2 is an “magnified image of the intermediate image of the panel 1 by the reflecting surface 7 and the rotationally asymmetric reflecting surface 8”, and the image forming magnification at this time is also negative. Thus, the light beam from the panel 1 forms an intermediate image as an inverted image, and further forms an image on the screen 2 as an upright image with the inverted image inverted. At that time, the trapezoidal distortion generated in the intermediate image cancels out the trapezoidal distortion generated when the image is formed on the screen, and a display image with little trapezoidal distortion can be obtained.

  When the transmission optical system 3 is formed into a cell as a unit, relative position adjustment between the cell-formed transmission optical system 3 and the reflection optical system remains as position adjustment in the enlargement projection optical system. At this time, if the power of the reflecting surface 4 on the most upstream side in the reflecting optical system is positive, when the light beam emitted from the transmission optical system 3 is a condensed light beam, the light beam is further increased by the positive power of the reflecting surface 4. It receives the action of being condensed.

  In this embodiment, “power of the reflecting surface 4” is negative. When the power of the reflecting surface 4 is positive, the aberration that occurs when the relative position between the transmission optical system 3 and the reflection optical system is “deviation” increases. In other words, when the amount of deviation between the transmission optical system 3 and the “reflection optical system” is the same, the amount of change in aberration with respect to the amount of deviation is large.

  As in the embodiment, when the power of the reflecting surface 4 is negative, the “aberration change amount with respect to the shift amount” is small. Accordingly, the accuracy of the relative positional relationship between the transmission optical system 3 and the reflection optical system becomes moderate, and the optical system can be easily assembled.

  After making the power of the reflection surface 4 negative, the power of the reflection surface 5 arranged downstream is positive. If a negative power reflecting surface continues on the upstream side in the reflecting optical system, the divergence of the incident light beam becomes excessive, and an “aperture image” cannot be formed in the reflecting optical system.

  Making the power of the reflecting surface 5 positive is important for making the imaging light beam reflected by the reflecting surface 5 converge and tend to form the image I9 of the stop 9 in the optical path of the reflecting optical system. That is, the combined power of the optical system (reflecting surfaces 4 to 7) provided between the stop 9 and the stop image I9 is positive.

  The reflecting surface 5 as well as the reflecting surface 4 may have negative power and the power of the reflecting surface 6 on the downstream side may be positive. However, it is necessary to increase the power of the reflecting surface 6 or the distance between the surfaces becomes long. As a result, the amount of aberration increases, the optical system becomes larger, and the number of components increases, so there is not much merit.

  In the magnifying projection optical system in which both the panel 1 and the screen 2 perform “oblique projection” in a plane, in the present invention, “an intermediate image of the negative magnification of the panel 1 that generates a light beam directed from the panel 1 side to the screen 2”, The optical systems on the upstream and downstream sides of the intermediate image plane are configured so that the positions and shapes of the “intermediate image of negative magnification of the screen 2 that generates a light beam traveling from the screen 2 side to the panel 1” are substantially the same. ing.

  The “light beam from the screen 2 side toward the panel 1” refers to a virtual light beam that is used when ray tracing is performed with the screen as the object plane and the panel as the image plane when designing an enlarged projection optical system.

  In the reflection optical system portion, the rotationally asymmetric reflection surface 8 is preferably disposed at a position closest to the screen 2 on the most downstream side in the optical path of the imaging light beam, as in this embodiment. The incident positions of the “respective light beams corresponding to different angles of view” on the reflecting surfaces 4 to 8 are such that the overlapping area is wide in the upstream and the “overlapping area” decreases in the downstream.

  Since the rotationally asymmetric reflecting surface has a high degree of freedom of the surface shape that can be taken with respect to the incident position, the rotationally asymmetric reflecting surface 8 is located on the most downstream side, and at this surface position, “the respective light beams corresponding to different angles of view overlap each other. If the “region” is reduced, it is possible to give the rotationally asymmetric reflecting surface 8 a “surface shape suitable for correcting the residual aberration of the light flux at each angle of view” by the optical system upstream of the rotationally asymmetric reflecting surface 8. A high aberration correction effect can be realized.

  Contrary to the above, if a rotationally asymmetric reflecting surface is provided on the upstream side of the reflecting optical system, the light beams with different angles of view are incident on the same position of the reflecting surface. It is difficult to obtain a “reflecting surface shape solution” that simultaneously corrects aberrations of each of the light beams.

  In this embodiment, the transmission optical system 3 can also share “correction of asymmetrical aberration components”. In such a case, in order to increase the correction effect, the transmission optical system 3 is provided with a “rotationally asymmetric transmission surface”. The rotationally asymmetric surface is effective for “correcting an aberration component difficult to correct with a rotationally symmetric aspherical surface”.

  The reflective optical system is composed of a plurality of reflective surfaces 4 to 8. However, when these are integrated as a unit, the relative positional accuracy between the reflective surfaces can be easily obtained, and the enlarged projection optical system can be easily assembled. become. The integration of the reflecting surfaces can be realized by, for example, a molding method, but is not limited thereto, and may be realized by other appropriate methods.

  In other words, the position where the diaphragm 9 is disposed is not limited to the position shown in FIG. 1, and may be provided between the surfaces of the transmission optical system 3, for example. In this case, a part of the transmission optical system also participates in the image formation of the aperture image.

  The number of image display panels is not limited to one, and three image display panels are used, and R (red), G (green), and B (blue) color component images are displayed on different image display panels for each color. The light from the image display panel can be combined, guided to the screen by the enlarged projection optical system, and a color image can be displayed on the screen.

In such a case, in FIG. 1, a combination of a polarizing beam splitter and a dichroic prism between the panel 1 and the transmission optical system 3 (which is widely known in a color image projection apparatus) can be used. .
Further, the screen does not necessarily have to be a plane.

  As described above, the enlarged projection optical system shown in the embodiment in FIG. 6 guides the light flux from the image display panel 1 to the screen 2 and projects it from the direction inclined with respect to the normal line of the screen 2. An enlarged projection optical system that forms an enlarged image of the image displayed on the image display panel 1 on the screen 2, and includes reflection optical systems 4 to 8 and a transmission optical system 3, and the reflection optical system has power. And includes a rotationally asymmetric reflecting surface 8, and the transmissive optical system 3 is constituted by a transmissive surface having refractive power and includes one or more aspheric surfaces.

  A diaphragm 9 is provided between the first surface from the image display panel side in the transmission optical system 3 and the first surface from the screen side in the reflection optical system, and the diaphragm 9 is arranged by optical elements 4 to 7 arranged on the screen side. The image I9 is formed at a negative reduction magnification.

  1 also includes a transmission optical system 3 composed of a plurality of transmission surfaces, a reflection optical system composed of a plurality of reflection surfaces 4 to 8, and a diaphragm 9. Of the reflection surfaces in the reflection optical system, The power of the reflecting surface 4 having the power at which the light beam passing through the diaphragm 9 is first incident is negative, and the reflecting surface 5 following the reflecting surface 4 having the negative power at which the light beam having passed through the diaphragm 9 is first incident is The reflective optical system has a positive power and is constituted by a plurality of reflective surfaces 4 to 8 having power, includes a rotationally asymmetric reflective surface 8, and the transmissive optical system 3 is constituted by a transmissive surface having refractive power, and is an aspherical surface. 1 or more.

  6 also generates an intermediate image of a negative magnification of the image display panel that generates a light beam from the image display panel 1 side to the screen 2 and a light beam from the screen 2 side to the image display panel 1. The position and shape of the negative magnification intermediate image of the screen 2 are substantially the same, have reflection optical systems 4 to 8 composed of a plurality of reflection surfaces, and transmission optical system 3 composed of a plurality of transmission surfaces. Among the reflecting surfaces in the reflecting optical system, the power of the reflecting surface 4 having the power at which the light beam that has passed through the stop is first incident is negative, and the power at which the light beam that has passed through the stop 9 is first incident is negative. The reflecting surface 5 following the reflecting surface 4 has positive power, the reflecting optical system is composed of a plurality of reflecting surfaces having power, includes a rotationally asymmetric reflecting surface 8, and the transmitting optical system 3 has a refractive power. Containing at least one aspheric surface .

  Further, the rotationally asymmetric reflective surface 8 is disposed “most on the screen 2 side” on the projection optical path, and the transmission optical system 3 includes a rotationally asymmetrical transmission surface having a refractive power, with respect to the position of the image display panel 1. The optical axis of the transmission optical system 3 is set to be decentered in a plane including the light guide optical path. The reflection optical system can be integrally formed as a unit.

  Therefore, by adding various known light sources to the enlarged projection optical system whose embodiment is shown in FIG. 6, an image is displayed on the image display panel 1, and the image display panel 1 is illuminated with light from the light source. Illuminated, the light flux from the illuminated image display panel 1 is guided to the screen 2 by the enlarged projection optical system, projected from the direction inclined with respect to the normal line of the screen 2, and projected onto the image display panel 1 on the screen 2. It is an expansion projection apparatus which projects the enlarged image of the displayed image, Comprising: As an expansion projection optical system, the expansion projection apparatus using the expansion projection optical system of any 1 of Claims 1-8 is realizable.

  Hereinafter, embodiments of S15 to S24 will be described.

  FIG. 7 shows an embodiment of an image projection apparatus having the projection optical system in S14. A portion of the projection optical system is enlarged and shown in FIG.

In FIG. 8, a portion denoted by reference numeral 71 represents a first optical system disposed on the object side, and a portion denoted by reference numeral 72 represents a second optical system disposed on the image side. The first optical system 71 includes lenses 711 to 716 and has a stop S immediately after the lens 713. The lens 713 is a “junction lens”.
Reference numerals 721 and 722 denote two reflecting surfaces constituting the second optical system.

  The object side of the first optical system 71 is irradiated with linearly polarized illumination light via a polarization beam splitter and modulated by the liquid crystal panel as described with reference to FIG. In this case, the reflected light beam becomes an imaging light beam through a polarizing beam splitter ”, and the symbol PB indicates the“ polarizing beam splitter ”.

  The light beam from the object side projects an image on a projection surface (screen shown in FIG. 7) (not shown) via the first optical system 71 and the second optical system 72, but the intermediate image of the object is a reflection surface 721. An image is formed at a position between 722 and a normal image is formed on the projection surface by the reflecting surface 722.

  As the “object for displaying the image to be projected”, the “light valve 15 shown in FIG. 1 is configured to illuminate the light beam from the light emitting unit 11 by the lamp and the reflector with the illumination optical system 12. Can be used. As specific examples of the light emitting section, a halogen lamp, a xenon lamp, a metal halide lamp, an ultrahigh pressure mercury lamp, and the like are suitable. The illumination optical system can also be equipped with an “integrator optical system that makes the intensity of the light beam reflected by the reflector and having directivity uniform with respect to the light valve”.

  As the object, it is also possible to use an “obliquely incident optical system” or a total reflection prism that separates optical paths with respect to the DMD panel. Of course, self-luminous objects such as LED arrays, EL arrays, and plasma displays can also be used.

  That is, the projection optical system in the embodiment shown in FIGS. 7 and 8 includes at least one refractive optical system (lens 711 or the like), a first optical system 71 having positive power, and a reflecting surface having power. (721, etc.) and a second optical system 72 having a positive power as a whole, arranged in order of the first and second optical systems from the side close to the object plane, and the object image is Once formed as an intermediate image, it is formed as a normal image, and another optical element 712 with respect to the optical axis of the optical element 711 having the refractive power closest to the object side in the first optical system. ˜716, 721, 722 are parallel and / or tilt eccentric.

  The configuration related to S16 to S24 will be described later as a specific numerical example.

FIG. 12 shows an embodiment of an image projection apparatus having a projection optical system of a reference example described later. FIG. 13 shows an enlarged portion of the projection optical system.
In FIG. 13, the part denoted by reference numeral 100 is “modulated by the liquid crystal panel 1 by irradiating the reflective liquid crystal panel with linearly polarized illumination light via a polarization beam splitter. The reflected light beam is an object-side portion of a type that becomes an imaging light beam through a polarizing beam splitter, and the image display surface of the reflective liquid crystal panel is a “projected object surface”. In the figure, the symbol PB indicates a polarizing beam splitter. The configuration on the object side is not limited to this, and “the light valve 15 is configured to illuminate the light beam from the light emitting unit 11 by the lamp and the reflector with the illumination optical system 12, or integrated with this, as described with reference to FIG. -An optical system with an optical system "can be used, or an optical system that can perform optical path separation with an oblique incident optical system or a total reflection prism with respect to a DMD panel can be used. LED arrays, EL arrays, plasma displays Self-luminous objects such as these can also be used.

  A portion denoted by reference numeral 120 represents a “transmissive refractive optical system”, and a portion denoted by reference numeral 130 represents a “reflective refractive optical system”.

  The transmissive refractive optical system 120 includes lenses 121 to 127. The lens 123 and the lens 126 are cemented lenses, and the whole is composed of nine lenses. The reflective refractive optical system 130 includes a first reflecting mirror 131 (only the reflecting surface is shown) and a second reflecting mirror 132 (only the reflecting surface is shown).

  That is, in the projection optical system shown in FIGS. 12 and 13, the light beam from the object surface to be projected is arranged in the first and second order from the transmission type refractive optical system 120 and the transmission type refractive optical system side. The light is guided and projected onto a projection surface (not shown) through a reflective refractive optical system 130 including two reflecting mirrors 131 and 132.

  The transmissive refracting optical system 120 includes a plurality of transmissive refracting elements 121 to 127. As shown in the drawing, from the projection object surface to the first surface of the transmissive refracting optical system (the object side surface of the lens 121) is shown in the figure. As described above, it is “substantially telecentric”, and the intermediate image plane of the projection object surface is positioned between the two reflecting mirrors 131 and 132 in the reflective refractive optical system 130, and the intermediate image on the intermediate image plane is The image is re-imaged as a normal image on the projection surface via the second reflecting mirror 132.

  As shown in a reference specific example which will be described later, the first reflecting mirror 131 is a negative power axisymmetric reflecting surface, and the second reflecting mirror 132 is an “anamorphic polynomial having different powers in the vertical and horizontal directions. A light beam that is a “free-form surface” and reaches the projection surface (not shown) from the second reflecting mirror 132 is guided with an inclination with respect to the normal line of the projection surface.

  The transmission refractive optical system 120 is decentered with respect to the normal line of the projection object surface, but the plurality of transmission refractive elements 121 to 127 included in the transmission refractive optical system are configured without being decentered from each other. ing.

  The lens 123 and the lens 126 are cemented lenses, and each of the cemented lenses 123 and 126 constitutes a “group unit” of the lens, but these cemented lenses are “configured without being decentered at the group unit level”. Yes.

  Further, as shown in FIG. 13, the image plane of the intermediate image formed between the reflecting mirrors 132 and 133 is “inclined and curved with respect to the principal ray of the light beam emitted from the center of the projection target surface”. On the final surface (exit side surface of the lens 127) of the transmission / refraction optical system, “the principal ray emitted from the center of the projection object surface and the principal ray emitted from the periphery of the projection object surface are substantially parallel”.

  The image projection apparatus of FIG. 12 is a “front projector type”, but of course, it can be a “rear projector type” by adding a reflecting mirror that bends the optical path in the imaging optical path.

Specific numerical examples will be given below.
In the specifications of the optical system, the surface numbers are sequentially counted as the first surface, the second surface,..., With the object surface (the surface on which the image to be projected is displayed) being the 0th surface. Through all numerical examples, the first surface and the second surface are surfaces of the “polarization beam splitter” on the liquid crystal panel side and the projection optical system side.

"Numerical example 1"
Numerical example 1 is a specific numerical example of the image projection apparatus / projection optical system shown in FIGS. That is, a first optical system 71 including at least one refractive optical system and having a positive power, and a second optical system 72 including at least one reflecting surface having a power and having a positive power as a whole. The first optical system is arranged in the order of the first and second optical systems from the side close to the object plane, and the object image is once formed as an intermediate image and then formed as a normal image. The other optical elements 712 to 716, 721, and 722 are decentered in parallel and / or tilted with respect to the optical axis of the optical element 711 having the refractive power closest to the object side.
The magnification of the intermediate image is about 3 times.

  The specifications of Numerical Example 1 are shown in Table 1.

  In Table 1, “shift” indicates the amount of shift eccentricity, and “tilt” indicates the amount of tilt eccentricity. The unit of the radius of curvature, the surface interval, and the shift eccentricity is “mm”, and the unit of the tilt eccentricity is “degree”. The same applies to the following numerical examples.

  The reflecting surface of the second reflecting mirror, which is the 18th surface, is an “anamorphic polynomial free-form surface having different powers in the vertical direction and the left-right direction” represented by the above-described equation (1). Are listed in Table 2.

In the above notation, for example, “1.14641E-11” means “1.14641 × 10 ⁻¹¹ ”. The same applies to the following.

  As described above, the first optical system is composed of seven lenses, and the second optical system is composed of two reflecting surfaces, but the reflecting surface 721 is a spherical surface and the reflecting surface 722 is a polynomial free-form surface. It is.

  The image plane (screen) of the normal image is a plane parallel to the left-right direction in FIG. 7, but the angle of incidence on the screen is low at a position where the image height is low (side closer to the object) and at a position where the image height is high (side far from the object). Although the difference is large, it tends to be a “projection image with a distorted bottom dent”, but the distortion of the intermediate image is set to be opposite to correct the distortion on the final image plane.

  FIG. 11 shows an “image distortion state” on the final image plane. FIG. 11 shows a state of distortion when an image displayed on a liquid crystal panel having a diagonal of about 0.9 inches is projected on the screen by being enlarged to about 60 inches. As shown in the figure, it can be seen that the grid images can be formed at substantially equal intervals, and the trapezoidal distortion is well corrected. The projection size is 1200 mm × 900 mm, the enlargement ratio is 65 times or more, and the distortion is 0.5% or less, which is very good.

"Numerical example 2"
Numerical example 2 is a specific numerical example of the image projection apparatus / projection optical system shown in FIG. FIG. 9 is an enlarged view of the projection optical system portion of the image projection apparatus.

  The first optical system 81 is composed of six lenses 811 to 816, and the second optical system 82 is composed of two reflecting surfaces 821 and 822. A diaphragm (not shown) is disposed between the lens 813 and the lens 814.

  Similar to Numerical Example 1, the intermediate image is formed as an inverted image by the first optical system 81 in the middle of the reflecting surfaces 821 and 822. The reflecting surface 821 having a positive power that first reflects the light side incident on the second optical system 82 has a rotationally symmetric aspherical shape, and the reflecting surface 822 has a polynomial free-form surface. This is an example in which a design with a higher degree of freedom is possible by adopting a rotationally symmetric aspherical shape.

  Table 3 shows the specifications of Numerical Example 2.

The aspherical surface to be rotated used in the sixteenth surface is such that Z is the depth in the optical axis direction, c is the paraxial radius of curvature, r is the distance in the optical axis orthogonal direction from the optical axis, k is the conic constant, A, A well-known aspherical expression in which B, C,...
Z = c · r ² / [1 + √ {1- (1 + k) c ² r ² }] + Ar ⁴ + Br ⁶ + Cr ⁸
The shape is specified by giving k, A, B, and C. The same applies to the other numerical examples below.

  Table 16 gives the coefficients of the aspheric surface of the sixteenth surface.

  Table 5 gives the values of the coefficients of the polynomial free-form surface of the 17th surface.

"Numerical example 3"
Numerical example 3 is a specific numerical example of the image projection apparatus / projection optical system shown in FIG.
The first optical system 91 is composed of five lenses 911 to 915, and the second optical system 92 is composed of two reflecting surfaces 921 and 922. The lens 913 is a cemented lens. A diaphragm (not shown) is disposed between the lens 913 and the lens 914.

  Similar to Numerical Examples 1 and 2, the intermediate image is formed between the reflecting surfaces 921 and 922. An intermediate image is formed as a reverse image by the first optical system. Further, the reflecting surface 921 having a positive power that first reflects the light side incident on the second optical system has a spherical shape, and the reflecting surface 922 has a polynomial free-form surface.

  Table 6 shows the specifications of Numerical Example 3.

  As is clear from Table 6, the first surface of lens 911 (the third surface in Table 6) is tilted by 2.2 degrees, but lenses 912 to 915 are tilted eccentrically with respect to the optical axis of lens 911. In other words, the lenses 911 to 915 are only eccentrically parallel to the optical axis of the lens 911. The refractive optical system includes a set of cemented lenses 913 that act as a group.

  Table 17 shows the coefficient values of the polynomial free-form surface of the sixteenth surface.

"Numerical example 4"
In numerical example 4, the optical system configuration (FIG. 10) is the same as in numerical example 3 described above, but the specifications are different.

  Table 8 shows the specifications of Numerical Example 4.

  Table 9 shows the coefficient values of the polynomial free-form surface of the sixteenth surface.

"Numerical example 5"
Numerical Example 5 also has different specifications with the same optical system configuration (FIG. 10) as Numerical Example 3 given above.

  Table 10 shows the data of Numerical Example 5.

  Table 11 shows the coefficient values of the polynomial free-form surface of the sixteenth surface.

  As described above, the numerical examples 1 to 5 include at least one refractive optical system, include a first optical system having a positive power, and at least one reflecting surface having a power. The first optical system is arranged in the order of the first and second optical systems from the side close to the object plane, and the object image is once formed as an intermediate image and then formed as a normal image. With respect to the optical axis of the optical element having the refractive power closest to the object side in the first optical system, the other optical element is decentered in parallel and / or tilted at one or more locations. In Numerical Examples 3 to 5, each element of the first optical system 91 is tilted eccentrically with respect to the optical axis of the optical element 911 having the refractive power closest to the object side in the first optical system 91. Not done.

  In Numerical Examples 3 to 4, the first optical system 91 is composed of two or more groups, and a lens 913 forming one group as a cemented lens of the two or more groups is decentered in parallel.

  In Numerical Examples 1 to 5, at least one of the reflecting surfaces included in the second optical system is a free-form surface, and among the reflecting surfaces included in the second optical system, the closest to the imaging position side of the normal image Only the reflecting surface is a free-form surface. In Numerical Examples 1 to 5, the reflecting surface having a positive power on which the light beam incident on the second optical system is reflected for the first time is a rotationally symmetric surface. , To 5, the rotationally symmetric reflecting surface is a spherical reflecting surface.

  In each of Numerical Examples 1 to 5, the first optical system is configured only by a refractive optical system, and the refractive optical system in the first optical system does not include an aspherical shape.

  Therefore, the image projection apparatus in which an object is combined with the projection optical system of the above numerical example constitutes a specific numerical example of the image projection apparatus of S24.

  Reference specific examples given below are numerical examples of the projection optical system / image projection apparatus whose embodiments have been described with reference to FIGS.

  Table 12 shows the specifications of the reference specific examples.

  Table 13 gives the aspheric coefficients of the seventh and fifteenth surfaces.

  Table 14 gives the values of the coefficients of the polynomial free-form surfaces of the 19th and 21st surfaces.

The MTF performance on the screen by the projection optical system of the reference specific example is 60% or more at a frequency of 0.5 c / mm, and the distortion is 2% or less.
In the reference specific example, the size of the screen for projecting the normal image is 60 inches, and the “maximum width in the direction perpendicular to the screen” of the projection optical system is 472 mm.

  As shown in FIG. 14, the screen has ± 1.0Y, ± 0.5Y, 0.0Y, ± 1.0X, ± 0.5X, 0 in the X direction (left and right direction) and Y direction (up and down direction). When a 0.0X grid-like line was set and the MTF value for the evaluation frequency: 0.5 c / mm was examined, it was as shown in Table 15.

  FIG. 15 shows the MTF characteristics in the sagittal direction (s) and the meridional direction (m) at ± 1.0Y and 0.0Y in the frequency range of 0 to 0.5 c / mm at X = 0.0X. FIG. 16 shows the MTF characteristics in the sagittal direction (s) and the meridional direction (m) at ± 1.0Y and 0.0Y in the frequency range of 0 to 0.5 c / mm at X = 0.5X. FIG. 17 shows the MTF characteristics in the sagittal direction (s) and the meridional direction (m) at ± 1.0Y and 0.0Y in the frequency range of 0 to 0.5 c / mm at X = 1.0X. As is apparent from these drawings, Numerical Example 6 has good MTF characteristics.

  The projection optical system of the reference specific example has a reflection-refractive-type refractive optical system having two reflecting mirrors arranged in the first and second order from the transmission-type refractive optical system side, and an intermediate image of the projection object surface. The surface is located between the first and second reflecting mirrors, the first reflecting mirror is an axisymmetric reflecting surface with negative power (the 22nd surface), and the second reflecting mirror is in the vertical and horizontal directions. This is an anamorphic polynomial free-form surface (23rd surface) with different power, and as a means for correcting the aspect ratio of the intermediate image of the projection target surface, power is transmitted in the vertical and horizontal directions in the transmission refractive optical system. Have different anamorphic polynomial free-form surfaces (19th surface).

  Further, the NA (= 0.143) on the object side to be projected in the transmissive refractive optical system is larger than the NA (= 0.01) on the intermediate image plane side, and the magnification of the intermediate image: M1 (= 1.5). ) Is in the range of 1 to 5, the projection magnification (= 75 times) is 40 or more, and the projection angle with respect to the projection plane: θ (= 11 degrees) is larger than 5 °.

It is a figure for demonstrating one Embodiment of a projection optical system and an image projection apparatus. It is a figure for demonstrating the projection optical system of embodiment shown in FIG. It is a figure for demonstrating a reference technique. It is a figure for demonstrating a reference technique. It is a figure for demonstrating a reference technique. It is a figure for demonstrating one Embodiment of an expansion projection optical system. It is a figure for demonstrating one Embodiment of an image projection apparatus. It is a figure which expands and shows the projection optical system part in FIG. It is a figure for demonstrating another form of implementation of an image projection apparatus. It is a figure for demonstrating the other form of implementation of an image projection apparatus. It is a figure which shows the state of the distortion on the screen in the numerical example 1. FIG. It is a figure for demonstrating the other form of implementation of an image projection apparatus. It is a figure which expands and shows the projection optical system part in FIG. It is a figure for demonstrating the evaluation point of MTF on the screen regarding a reference specific example. It is a figure which shows the MTF characteristic regarding a reference specific example. It is a figure which shows the MTF characteristic regarding a reference specific example. It is a figure which shows the MTF characteristic regarding a reference specific example.

Explanation of symbols

L1 1st lens L2 2nd lens L3 3rd lens 1 Image display panel 2 Screen 3 Transmission optical system 4-8 Reflective surface which comprises reflective optical system 8 Rotationally asymmetrical reflective surface 9 Aperture I9 Aperture image

Claims (9)

The light beam from the image display panel is guided to the screen, projected from a direction inclined with respect to the normal line of the screen, and an enlarged image of the image displayed on the image display panel is formed on the screen. A projection optical system,
A transmissive optical system that consists of a transmissive surface having a refractive index and propagates a light beam from the image display panel;
A negative power reflecting surface is provided on the downstream side of the transmission optical system and has a negative power reflecting surface on the most upstream side of the plurality of reflecting surfaces, and the negative image of the image panel formed on the downstream side of the negative power reflecting surface. An enlarged projection optical system comprising: a reflection optical system that forms an intermediate image having a magnification of 1 on the screen as an erect image of the image. The magnification projection optical system according to claim 1,
The transmission optical system has a plurality of transmission surfaces having a refractive index,
A diaphragm is provided between the surfaces of the transmission optical system or between the transmission optical system and the reflection optical system, and an image of the diaphragm is formed at a negative reduction magnification in the optical path of the reflection optical system. Enlarging projection optical system. In the magnifying projection optical system according to claim 2,
An enlarging projection optical system characterized in that, of the reflecting surfaces in the reflecting optical system, the power of the reflecting surface following the reflecting surface having a negative power on which the light beam that has passed through the aperture first enters is positive. In the magnification projection optical system according to any one of claims 1 to 3,
The reflective optical system is composed of a plurality of reflective surfaces having power, and includes one or more rotationally asymmetric reflective surfaces,
The transmissive optical system is constituted by a transmissive surface having a refractive power, and includes one or more aspheric surfaces. The magnification projection optical system according to claim 4,
An enlarged projection optical system characterized in that the rotationally asymmetric reflection surface is disposed on the most screen side in the projection optical path. In the enlarged projection optical system according to any one of claims 1 to 5,
An enlarged projection optical system, wherein the transmission optical system includes a rotationally asymmetric transmission surface having refractive power. In the magnification projection optical system according to any one of claims 1 to 6,
An enlarged projection optical system, wherein an optical axis of a transmission optical system is set eccentric with respect to an image display panel position in a plane including a light guide optical path. In the magnification projection optical system according to any one of claims 1 to 7,
An enlarged projection optical system, wherein the reflection optical system is configured as a unit. An image is displayed on the image display panel, the image display panel is illuminated with light from a light source, a light beam from the illuminated image display panel is guided to the screen by an enlarged projection optical system, and the normal line of the screen is displayed. An enlarged projection device that projects from an inclined direction and projects an enlarged image of the image displayed on the image display panel on the screen,
An enlargement projection apparatus using the enlargement projection optical system according to any one of claims 1 to 8 as an enlargement projection optical system.

Images