JP5338824B2 - Image projection device - 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&amp;INPIT

Description

This inventions relates to 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.

  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. On the other hand, it is an object to realize a projection optical system capable of correcting chromatic aberration and projecting a large screen, and a thin image projection apparatus using such a projection optical system.

Projection optical system according to the present invention is a "projection optical system for enlarging and projecting the image formed on the light valve on a projection plane", has the following characteristics.

That is, the projection optical system has a lens optical system and first and second reflecting surfaces.
The “lens optical system” includes a plurality of lenses and forms an “intermediate image” between the projection surface and the light valve, and has positive power.
The “first reflecting surface” has a positive power for reflecting the diverging light beam after forming the intermediate image and forming an image on the projection surface.
The “second reflection surface” is a reflection surface for causing the light emitted from the lens optical system to enter the first reflection surface.
That is, the light beam from the light valve is guided to the projection surface by the lens optical system and the first and second reflecting surfaces to project an enlarged image, but first, it is formed as an intermediate image by the lens optical system. The light beam that forms the intermediate image is reflected by the second reflecting surface, enters the first reflecting surface while diverging, and is reflected by the first reflecting surface toward the projection surface.
Projecting Shako Science system of reference technology 1 according to the present invention is characterized in the following points.
That is, the plurality of lenses and the second reflecting surface are arranged on a straight line parallel to the projection surface, the second reflecting surface is arranged with the back facing the projection surface, and the first reflecting surface is , Arranged toward the projection plane.

Projecting Shako Science system of reference technique 2 of the present invention is characterized in the following points.
That is, the plurality of lenses and the second reflecting surface are disposed along a plane including the projection surface, the second reflecting surface is disposed facing the projection surface, and the first reflecting surface is , Arranged toward the projection plane.
As a supplement, the shape of the intermediate image can be “a shape that reduces the trapezoidal distortion of the final image”, and “forms an intermediate image that is distorted opposite to the trapezoidal distortion of the final image”. Can be configured.
The intermediate image can have a shape of “the side with the largest incident angle on the projection surface is the shortest”.

The intermediate image can be inclined with respect to the principal ray of the light beam emitted from the center of the light valve, and the image plane can be curved.
The first reflecting surface can be a free-form surface.

As described above, the lens optical system includes a plurality of lenses.

The lens surface of the lens constituting the lens optical system can have a “aspherical refractive surface” as a free-form surface.

In the "image projection apparatus that irradiates the light bulb for image formation with illumination light from the light source and enlarges and projects the image formed on the light valve by the projection optical system", the image formed on the light valve is enlarged and projected. it can be used reference technology 1 or reference technology 2 for even the as a projection optical system.
The image projection apparatus according to claim 1 is provided with “a light source, a light valve, and a projection optical system,
The light from the light source is illuminated on the light valve, the light beam from the light valve is guided to the screen by the projection optical system, and a final image obtained by enlarging the image formed on the light valve on the screen is projected. An image projection device that forms an image on a surface ,
The projection optical system includes a plurality of lenses, and a lens optical system having a positive power for forming an intermediate image of the image between the projection surface and the light valve;
A first reflecting surface having a positive power for reflecting a diverging light beam after forming the intermediate image and forming an image on the projection surface;
A second reflecting surface that is disposed on the optical path of the emitted light from the lens optical system and that causes the emitted light to enter the first reflecting surface;
The first reflecting surface is disposed toward the projection surface;
The second reflective surface is disposed between a plane including the projection surface and the first reflective surface, and is disposed so as to face the first reflective surface,
The plurality of lenses are arranged such that the extension of the optical axis is between the first reflecting surface and the projection surface ”.

  The projection optical system “guides the light flux from the light valve to the screen and projects it from a direction inclined with respect to the normal line of the screen to form an enlarged image of the image formed on the light valve on the screen”. It can be a magnifying projection optical system.

  The “light valve (LV)” may be a transmissive or reflective liquid crystal panel, a digital micromirror device (DMD), or the like.

Hereinafter, an enlarged projection optical system having a reflection optical system and a transmission optical system will be described as a reference technique.
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 magnifying projection optical system, “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 the optical element disposed on the screen side is It is preferable that the diaphragm image is formed at a negative reduction magnification.

  The magnifying projection optical system 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 at which the light beam first enters” can be negative.

  In this magnifying projection optical system, it is preferable that the reflecting surface following the “reflecting surface having a negative power on which the light beam having passed through the aperture first enters” has a positive power.

  The reflection optical system in the above-mentioned enlargement projection optical system includes “a plurality of reflection surfaces having power and includes one or more rotationally asymmetric reflection surfaces”, and the transmission optical system includes “a transmission surface having refractive power. It is preferable to include one or more spherical surfaces.

Another magnification projection optical system has the following characteristics.
That is, an intermediate image of a negative magnification (an intermediate image of an image panel generated on the optical path of the imaged light beam by the magnifying projection optical system) of the image display panel that generates a light beam from the image display panel side to the screen, and the screen An intermediate image of negative magnification of the screen generated by the light flux from the side to the image display panel (the intermediate image of the screen generated on the optical path when light is virtually incident on the enlargement projection optical system from the screen side) Incidentally, the position and shape of the screen image at this time is a reduced image formed on the image display panel).

  This magnifying projection optical system can have a “reflecting optical system consisting of a plurality of reflecting surfaces” and a “transmitting optical system consisting of a plurality of transmitting surfaces”. In this case, the magnifying projection optical system has an “aperture”. The power of the “reflecting surface having the power at which the light beam that has passed through the aperture first enters” among the reflecting surfaces in the reflecting optical system can be negative). In this case, it is preferable that the “reflecting surface following the reflecting surface having a negative power on which the light beam having passed through the diaphragm first enters” has a positive power.

  In the above-mentioned magnified projection optical system, the reflection optical system is “consisting of a plurality of reflective surfaces having power and including one or more rotationally asymmetric reflection surfaces”, and the transmission optical system is composed of “transmission surfaces having refractive power” And a configuration including one or more aspherical surfaces ”.

  In the magnifying projection optical system, it is preferable that the “rotationally asymmetric reflection surface” included in the reflection optical system is disposed on the most screen side in the projection optical path.

  In the magnifying projection optical system, the transmission optical system preferably includes a “rotationally asymmetric transmission surface having refractive power”.

  In the magnifying projection optical system, the optical axis of the transmissive optical system is the light guide optical path (from the center of the image display panel in the optical path from the image display panel to the screen) to the center of the enlarged image on the screen with respect to the image display panel position. Can be set eccentrically in the plane including the optical path of the principal ray leading to

  Further, the reflection optical system in the above-mentioned enlarged projection optical system can be configured as a “unit”.

  Using the above-mentioned enlarged projection optical system, “displaying an image on the image display panel, illuminating the image display panel with light from the light source, and guiding the luminous flux from the illuminated image display panel to the screen with the enlarged projection optical system, It is possible to configure an “enlarged projection device” that projects from a direction inclined with respect to the normal line of the screen and projects an enlarged image of the image displayed on the image display panel on the screen.

To supplement a little, 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 “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 “light valve as an image display panel” used in the magnifying projection device 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 above-mentioned enlargement projection optical system, the imaged light beam is projected from the direction inclined with respect to the screen normal and imaged on the screen. It is possible to effectively reduce the “distortion of the display image that occurs when tilted with respect to the line”.

  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.

  Further, a stop 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 an image of the stop is transmitted in the entire optical system by a light beam from the panel side. When the image is formed once, the imaging 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.

  By making the shape and position of the intermediate image of the diaphragm 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 thereon.

  If the final surface on the imaging optical path is a rotationally asymmetric reflecting surface, 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, aberrations that cannot be generated by the rotationally symmetric transmission surface can be generated, and the aberrations thus generated can be used for canceling other aberrations.

  When the optical axis of the transmission optical system is decentered in the plane including the light guide optical path with respect to the position of the image display panel, an aberration opposite to the aberration generated on the eccentric reflection surface in the reflection optical system is transmitted. And can be canceled.

The projection optical system 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.

  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”. Can do. That is, parallel eccentricity or tilt eccentricity is performed in “optical element units”.

  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.

  In the first optical system, each element of the first optical system may not be “tilt decentered” with respect to the optical axis of “the optical element having the refractive power closest to the object side”.

  In this case, a configuration in which the first optical system is composed of two or more groups and at least one of the two or more groups is decentered in parallel can be adopted.

  One or more of the reflecting surfaces included in the second optical system are preferably “free-form surfaces”. Among the reflecting surfaces included in the second optical system, “only the reflecting surface closest to the imaging position side of the normal image” is used. Can be a free-form surface.

  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 preferably a rotationally symmetric surface. In this case, the rotationally symmetric reflecting surface is referred to as a “spherical reflecting surface”. can do.

  In the projection optical system, the “first optical system can be configured only by a refractive optical system”, and in this case, the refractive optical system in the first optical system should be “not including an aspherical shape”. be able to.

  An image projection apparatus for guiding a light beam from an image display panel to a screen by a projection optical system, and forming a normal image of an image displayed on the image display panel on the screen, the projection optical system as the projection optical system Can be configured.

  To supplement a little, in the image projection apparatus using the projection optical system described above, the object to be projected is illuminated with light from an external light source such as a light valve such as a liquid crystal panel, DMD, slide film, etc. Of course, it is possible to use self-luminous image display means such as a two-dimensional array of light emitting diodes, a plasma display, and an EL light emitting element array.

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

Hereinafter, another aspect will be described.
The projection optical system refers to “a projection optical system that guides and projects a light beam from a projection object surface onto a projection surface via a transmission refractive optical system and a reflective refractive optical system including one or two reflecting mirrors. "

  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 refers to “a projection optical system that guides and projects a light beam from a projection object surface onto a projection surface via a transmissive refractive optical system and a reflective refractive optical system including one or two reflecting mirrors. The transmission-type refractive optical system has a plurality of transmission-type refractive elements, and is substantially telecentric from the projection object surface to the first surface of the transmission-type refractive optical system, and is more reflective than the transmission-type refractive optical system. An intermediate image plane of the object surface to be projected is positioned on the side of the mold refracting optical 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 one reflection mirror However, it is an anamorphic polynomial free-form surface with different power in the vertical direction and the horizontal direction, and the light beam from the reflective refractive optical system to the projection surface is guided with an inclination with respect to the normal line of the projection surface. be able to.

  “The transmission-type refractive optical system is decentered with respect to the normal of the object surface to be projected, and the plurality of transmission-type refractive elements included in the transmission-type refractive optical system are configured without being decentered from each other at the group unit level.” be able to.

  These projection optical systems have the following features: “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 intermediate image plane of the object surface to be projected is Located 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 an anamorphic polynomial whose power is different in the vertical and horizontal directions. It can be a curved surface.

  Further, as “a means for correcting the aspect ratio of the intermediate image of the projection target surface”, an anamorphic polynomial free-form surface having different powers in the vertical direction and the horizontal direction can be provided in the transmissive refractive optical system.

  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.

  Although the adoption of a polynomial free-form surface in a transmissive refractive optical system is not limited to one surface, in the example described later, a sufficient correction effect was obtained by using only one polynomial free-form surface in the transmissive refractive optical system. . 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 example described later, a polynomial free-form surface is adopted as the final surface of the transmissive refractive optical system.

  The projection optical system 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 surface side”.

  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 the projection optical system, the intermediate image plane can be “inclined with respect to the principal ray of the light beam emitted from the center of the projection object surface and the image plane is curved”. 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 the final surface of the transmissive refractive 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 preferably substantially parallel”.

  “Magnification of intermediate image: M1 is about 1 to 5” is preferable. The projection magnification can be 40 or more. In this case, it is preferable that the projection angle θ relative to the projection plane is larger than 5 °.

  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.

  As a projection optical system of an “image projection apparatus for enlarging and projecting an image formed on a light valve, which is a projection object surface, onto the projection surface by a projection optical system”, a projector using any of the above is a front projector type. Or a rear projector type having a folding mirror that folds the imaging optical path.

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, an image projection apparatus using a novel projection optical system can be realized.

The projection optical system according to the present invention includes a lens optical system and first and second reflecting surfaces, and an image formed by the light valve is formed on the imaging optical path by the light optical valve and the projection surface by the lens optical system. When the color composition prism is used, a large projection magnification can be realized and the lens optical system is composed of two or more lenses. Also, the chromatic aberration can be corrected by utilizing the chromatic dispersion characteristics, and the optical path of the imaging light beam is folded back by the first and second reflecting surfaces, so that a compact configuration can be achieved.

Therefore, an image projection apparatus using a projection optical system according to the present invention, compact configurable, since taken longer at the optical path of the device in space of the imaging light beam, an image of a large size while reducing the device outside the projection space Projection display is possible.

  And the expansion projection apparatus using this expansion projection optical system can be realized thinly, the installation floor area can be effectively reduced, and it can be arranged in a narrow part.

Further, by forming an intermediate image with the lens optical system and enlarging and projecting it on the first and second reflecting surfaces, it is possible to increase the magnification of the combined optical system, and the lens elements constituting the refractive optical system are made parallel. By decentering or tilting decentering, it is possible to “effectively generate reverse distortion in the intermediate image” so that the projected image is not distorted, and it is also possible to realize close-up projection at a desired magnification. .

It is a figure for demonstrating one form of a projection optical system and an image projection apparatus. It is a figure for demonstrating the projection optical system of the form shown in FIG. It is a figure for demonstrating one form of a projection optical system. It is a figure for demonstrating one form of a projection optical system. It is a figure for demonstrating one form of a projection optical system. It is a figure for demonstrating one form of an expansion projection optical system. It is a figure for demonstrating one form of reference 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 reference form of an image projection apparatus. It is a figure for demonstrating the other reference form of an image projector. It is a figure which shows the state of the distortion on the screen in the reference example 1. FIG. It is a figure for demonstrating embodiment of an image projection apparatus. It is a figure which expands and shows the projection optical system part in FIG. FIG. 6 is a diagram for explaining an evaluation point of MTF on a screen related to Example 1 . FIG. 4 is a diagram showing MTF characteristics related to Example 1 . FIG. 4 is a diagram showing MTF characteristics related to Example 1 . FIG. 4 is a diagram showing MTF characteristics related to Example 1 .

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

A “light valve” indicated by reference numeral 15 is a liquid crystal panel in this reference 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. It is also possible to incline the intermediate image with respect to the principal ray of the light beam emitted from the center of the light valve and to curve the image surface.

  In the form shown in FIGS. 1 and 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 to return the optical path, and the intermediate image Iint is obtained. The projection image is projected in the direction opposite to the traveling direction of the light beam to be formed.

  1 and 2 are examples in which the second optical system 19 is configured by a single concave mirror. However, the second optical system is not limited to this, and can include two or more reflecting surfaces. In addition, a refractive optical system can be included 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 influenced by the shape of the “reflection area A” ”of the second optical system 19, and the image formation with respect to the light beam from the position: B is performed. The performance is affected by the shape of the “reflection area B ″”.

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, the position on the screen 21 starting from the positions A and B on the panel 15:
The interval between the principal rays reaching a ′ and b ′ is about 362 mm, and the enlargement ratio is improved as compared with the case shown in FIG. 3 (208 mm). 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.
Incidentally, FIG. 3, with reference embodiment of FIG. 4, the first optical system is constituted by the refractive optical system consisting of one or more lenses having a positive power, the second optical system 1 having a power An image formed by the light reflection valve 19 and having a positive power and formed by the light valve 15 is converted into an intermediate image by a first optical system in a space between the first optical system and the reflection surface. Iint is imaged, the divergent light beam after being imaged as the intermediate image Iint is reflected by the reflecting surface 19, and an image obtained by further enlarging the intermediate image by the positive power of the reflecting surface 19 is used as a final image on the projection surface. The incident angle of the light beam projected onto a certain screen 21 and reflected by the second optical system 19 on the projection surface 21 is the farthest position from the light valve 15 on the final image (the top of the image in FIGS. 3 and 4). It is configured to be larger than the closest position.

  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.

  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 another form. 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 of the second optical system 190 is brought close to the reflecting surface 192 having the positive power of the second optical system 190 according to Reference Technique 2 of the present invention. This is an example of an “optical system having a negative power having an action”.

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.

  By using “an optical element having a negative power to bring the imaging position of the intermediate image closer to a reflecting surface having a positive power in the second optical system”, “reflection having a positive power in the second optical system” Adjustment to narrow the “degree of divergence” of the incident light beam on the “surface” is possible, and the “effective reflection area” of the reflecting surface having the positive power can be reduced.

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 reference embodiment with a free-form surface, the degree of freedom in design increases, and various aberrations can be easily corrected.

  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 the performance can be improved.

  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 that can adjust 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 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.

  Although the first optical system can be configured by “refractive optical system only”, it is necessary to “further improve the degree of freedom in the configuration of the first optical system” when further performance improvement is desired.

  In order to further improve the performance as described above, it is preferable that the first optical system is “consisting of a reflecting surface having a rotational symmetry axis and a refractive optical system”. 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.

The image projection apparatus will be described with reference to FIG.
FIG. 1 is simplified for ease of illustration.
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. After the colors are synthesized by the means, the light is incident on the first optical system 17 and the like, so that the screen 2
Needless to say, a color image can be projected onto the image 1.

  Another embodiment will be described below.

  In the form shown in FIG. 6, the reference beam of the light beam group traveling from the image display panel indicated by reference numeral 1 (hereinafter simply referred to as panel 1) toward the “screen” indicated by reference numeral 2 has the normal to the screen 2 and a predetermined inclination. Is incident on. 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 effect of magnification enlargement” in the transmission optical system 3 is relaxed, and in particular, “the aperture of the lens on the downstream side does not increase”. I have to. 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 effect of correcting 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 a power arrangement is adopted such that the image I9 of the diaphragm 9 forms an image at a reduction magnification, the light beam incident on the reflecting surface (the reflecting surface 8 in the embodiment being described) on the downstream side of the image I9 of the diaphragm 9. Since it does not spread greatly, this reflecting surface can be made small.

  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 form 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 enlarged 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.

  When the power of the reflecting surface 4 is negative as in the above embodiment, the “amount of change in aberration 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 reflecting 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 between the panel 1 and the transmission optical system 3 and a dichroic prism (which is widely known in a color image projection apparatus) can be used. .
The screen is flat.

  As described above, the enlarged projection optical system shown in FIG. 1 guides the light beam 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 an image displayed on the image display panel 1, which includes reflection optical systems 4 to 8 and a transmission optical system 3, and the reflection optical system has a plurality of reflections having power. The transmission optical system 3 is configured by a transmission 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.

  6 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, the illumination against enlarging projection optical system showing a reference embodiment in FIG. 6, by the addition of various known light sources, the image is displayed on the image display panel 1, the image display panel 1 with light from a light source Then, 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 displayed on the screen 2 on the image display panel 1. It is an expansion projection apparatus which projects the enlarged image of the made image.

Hereinafter, reference embodiments and embodiments will be described.

FIG. 7 shows a reference form of the image projection apparatus. 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 lens optical system disposed on the object side, and a portion denoted by reference numeral 72 represents first and second reflecting surfaces disposed on the image side. The lens optical system 71 includes a plurality of lenses 711 to 716 and has a diaphragm S immediately after the lens 713. The lens 713 is a “junction lens”.
Reference numerals 721 and 722 indicate first and second reflecting surfaces, respectively. A portion where the first reflecting surface 722 and the second reflecting surface 721 are combined is hereinafter referred to as a “second optical system”.

The object side of the lens optical system 71, as described with reference to FIG. 6, “reflected liquid crystal panel is irradiated with linearly polarized illumination light via a polarization beam splitter and reflected by the liquid crystal panel. A type in which the light beam becomes an imaging light beam through the polarization beam splitter is assumed, and the symbol PB indicates the “polarization beam splitter”.

The light beam from the object side projects a magnified image on a flat projection surface (screen shown in FIG. 7) (not shown) via the lens optical system 71 and the second optical system 72, but the intermediate image of the object is a reflection surface 721. And 722, and a final 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 reference embodiment shown in FIG. 7 and FIG. 8 is composed of one or more lenses, and has a positive optical power, a lens optical system 71 having a positive power, a single second reflecting surface 721, and a positive power. The plurality of lenses constituting the lens optical system 71 and the second reflecting surface 721 are arranged along a “plane including a screen as a projection surface”.
The object image is configured to be formed as an intermediate image and then formed as a final image.
Further, in the lens optical system, 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.

Specific reference examples and examples will be described later.

12 shows a form of implementation of the image projection apparatus. 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 forms an imaged light beam through a polarizing beam splitter, and the image display surface of the reflective liquid crystal panel is the “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 lens optical system, and a portion denoted by reference numeral 130 represents a second optical system including a first reflecting surface 132 and a second reflecting surface 131 .

The lens optical system 120 includes a plurality of lenses 121 to 127. The lens 123 and the lens 126 are cemented lenses, and the whole is composed of nine lenses. The second optical system 130 includes a single second reflection surface 131 and a first reflection surface 132.

That is, in the projection optical system shown in FIGS. 12 and 13, the light beam from the object surface to be projected is not shown through the second optical system 130 including the lens optical system 120 and the two reflecting surfaces 131 and 132. It is guided and projected onto the surface.
As shown in FIG. 12, the plurality of lenses constituting the lens optical system 120 and the second reflecting surface 131 are arranged on a straight line parallel to the screen as the projection surface, and the second reflecting surface 131 is arranged on the projection surface. The first reflecting surface 132 is disposed toward the projection surface.

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

As shown in an example to be described later, the second reflecting surface 131 is a negative power axisymmetric reflecting surface, and the first reflecting surface 132 is an “anamorphic polynomial free-form surface having different power in the vertical direction and the horizontal direction”. In other words, light rays reaching the projection surface (not shown) from the second reflecting mirror 132 are guided with an inclination with respect to the normal line of the projection surface.

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

  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 can be seen from FIG. 13, the image plane of the intermediate image formed between the first and second reflecting surfaces 132 and 131 is “inclined with respect to the principal ray of the light beam emitted from the center of the projection target surface. “Curved”, and “the principal ray emitted from the center of the object surface to be projected and the principal ray emitted from the periphery of the object surface to be projected are substantially parallel on the final surface (exit side surface of the lens 127) of the transmission refractive optical system. Is.

  Although the image projection apparatus of FIG. 12 is a “front projector type”, it is of course possible to adopt a “rear projector type” by adding a reflecting mirror that bends light in the imaging optical path.

Specific reference examples and examples are 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. Throughout all the reference examples and 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.

“Example 1” is to be read as “Reference Example 1”.
Reference Example 1 is a specific reference example of the image projection apparatus / projection optical system shown in FIGS. That is, a lens optical system 71 composed of a plurality of lenses and having positive power, a second reflecting surface 721, and a second optical system 72 having a first reflecting surface 722 having positive power, and an object The lens optical system and the second optical system are arranged in this order from the side close to the surface (light valve), and the object image is once formed as an intermediate image on the optical path between the first and second reflecting surfaces, and then as an intermediate image. A configuration in which a divergent light beam after being imaged is reflected by a second reflecting surface 722 having a positive power to further enlarge the intermediate image and project it onto a projection surface (screen) as a final image (regular image). It has become.
In the lens optical system, 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.

Table 1 shows the specifications of Reference Example 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 embodiments.

  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 lens 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. .

  The image plane (screen) of the normal image is a plane parallel to the left-right direction in FIG. 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 in reverse to correct the distortion on the final image plane. That is, in the shape of the intermediate image, the side with the largest incident angle to the screen as the projection surface is the shortest. Therefore, the shape of the final image in the plane direction is corrected by the shape of the intermediate image.

  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.

“Example 2” is to be read as “Reference Example 2”.
Reference Example 2 is a specific reference 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 lens 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.

As in Reference Example 1 , the intermediate image is formed as a reverse image by the lens optical system 81 in the middle of the reflecting surfaces 821 and 822. The second reflecting surface 821 that reflects the light beam incident on the second optical system 82 has a positive power and a rotationally symmetric aspherical shape, and the first reflecting surface 822 having the positive power is 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. As is clear from the specific data shown below, the positive power of the first reflecting surface is weak.

The specifications of Reference Example 2 are shown in Table 3.

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 following other embodiments.

  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.

“Example 3” is to be read as “Reference Example 3”.
Reference Example 3 is a specific reference example of the image projection apparatus / projection optical system shown in FIG.
The lens optical system 91 is composed of five lenses 911 to 915, and the second optical system 92 is composed of first and second reflecting surfaces 922 and 921. The lens 913 is a cemented lens.
A diaphragm (not shown) is disposed between the lens 913 and the lens 914.

Similar to Reference 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 lens optical system. The second 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 first reflecting surface 922 has a polynomial free-form surface.

The specifications of Reference Example 3 are shown in Table 6.

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.

“Example 4” is to be read as “Reference Example 4”.
The reference example 4 is different from the above-described reference example 3 in the optical system configuration (FIG. 10).

Table 8 shows the specifications of Reference Example 4 .

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

“Example 5” will be read as “Reference Example 5”.
Reference Example 5 also has different specifications with the same optical system configuration (FIG. 10) as Reference Example 3 described above.

Table 10 shows the specifications of Reference Example 5 .

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

As described above, each of the reference examples 1 to 5 includes a lens optical system including a plurality of lenses and having a positive power, a first reflecting surface, and a second reflecting surface having a positive power.
The plurality of lenses and the second reflection surface are arranged along a plane including the projection surface (screen), the second reflection surface is arranged facing the projection surface, and the first reflection surface is the projection It is arranged toward the surface.
The object image is once formed as an intermediate image and then formed as a final image.
In the lens optical systems of Reference Examples 1 to 5, parallel decentering and / or tilt decentering is performed at one or more other optical elements with respect to the optical axis of the optical element having the refractive power closest to the object side. and which, in reference examples 3 to 5, closest to the object side in the lens optical system 91, the elements of the lens optical system 91 is not tilted decentered with respect to the optical axis of the optical element 911 having a refractive power .

In Reference 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 Reference Examples 1 to 5, at least one of the reflecting surfaces included in the second optical system is a free-form surface, and only the first reflecting surface arranged toward the projection surface among the reflecting surfaces included in the second optical system. is a free curved surface, in reference examples 1 to 5, a second reflecting surface having a positive power light beam incident on the second optical system is reflected in the beginning is a rotationally symmetric surface, reference example 1, 3 In 5 , the rotationally symmetric reflecting surface is a spherical reflecting surface.

In all of Reference Examples 1 to 5, the lens optical system includes a plurality of lenses, and the lens in the lens optical system does not include an aspherical shape.

Therefore, the image projection apparatus combining an object the projection optical system of the reference example, constitutes a specific reference example of the image projection apparatus.

Example 1 given below is a specific example of the projection optical system / image projection apparatus whose embodiment has been described with reference to FIGS.

Table 12 shows the specifications of Example 1 .

  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 Example 1 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 clear from these figures, Example 1 has good MTF characteristics.

In the projection optical system of Example 1 , the reflective optical system has two reflective surfaces arranged in the second and first order from the transmissive refractive optical system side, and the intermediate image plane of the projection object surface is the first. The first reflecting surface is located between the first reflecting surface and the second reflecting surface, the second reflecting surface is an axisymmetric reflecting surface with negative power (the 22nd surface), and the first reflecting surface has an anamorphic polynomial in which the power differs in the vertical and horizontal directions. An anamorphic polynomial free-form surface that is a free-form surface (23rd surface) and has a power that varies in the vertical and horizontal directions in the transmission refractive optical system as a means for correcting the aspect ratio of the intermediate image of the projection object surface. (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 °.
In addition, the projection optical systems of Reference Examples 1 to 5 and Example 1 are configured so that “the light beam emitted from the light valve has a larger incident angle on the projection surface as the light beam is farther from the projection surface”.

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

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

Claims (1)

A light source, a light valve, and a projection optical system;
The light from the light source is illuminated on the light valve, the light beam from the light valve is guided to the screen by the projection optical system, and a final image obtained by enlarging the image formed on the light valve on the screen is projected. An image projection device that forms an image on a surface,
The projection optical system includes a plurality of lenses, and a lens optical system having a positive power for forming an intermediate image of the image between the projection surface and the light valve;
A first reflecting surface having a positive power for reflecting a diverging light beam after forming the intermediate image and forming an image on the projection surface;
The lens is disposed on the optical path of the light emitted from the optical system, and a second reflecting surface for incidence of the emitted light to the first reflecting surface made of,
The first reflecting surface is disposed toward the projection surface;
The second reflective surface is disposed between a plane including the projection surface and the first reflective surface, and is disposed so as to face the first reflective surface,
The plurality of lenses are arranged such that an extension of an optical axis thereof is between the first reflecting surface and the projection surface.

Images