JP2004295107A - Variable power optical system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a variable power optical system having compact constitution, where the occurrence of aberration such as hromatic aberration is restrained while obtaining a desired variable power ratio. <P>SOLUTION: The variable power optical system is constituted of an optical block R having reflection curved surfaces R1 to R3 and an optical block C arranged nearer to a reduction side than the optical block R. The optical block C has a plurality of movable lens units and performs variable power by moving a plurality of lens units. In the case of tracing a light beam from the reduction side to an enlargement side, the optical block C forms the image of a conjugate point on the reduction side nearer to the enlargement side than the optical surface (reflection surface R1) of the optical block R nearest to the reduction side. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a variable power optical system, and for example, relates to a variable power optical system that magnifies and projects an original image on a projection surface such as a screen so as to be variable.

  In recent years, as portable computers such as notebook-type personal computers and mobile computers have become widely used, in order to enlarge and display images created on the computer at meetings and presentations in offices. Projection display devices such as front projection type front projectors are widely used. Furthermore, as DVDs (Digital Versatile Disks) are penetrating the general market, and with the diversification and high definition of video information distribution such as digital broadcasting, images can be viewed on a large screen using a projector even at home. It has become.

  Conventionally, a refraction optical system including a plurality of lenses has been widely used as a projection optical system for a projector. When this type of optical system is used as a projection display device such as a front projector, the center of the screen is shifted from the optical axis of the optical system in order to secure the field of view of the observer. This is because the panel surface is decentered parallel to the optical axis within the angle of view guaranteed by the optical system, that is, using a part of the effective angle of view. Needs to be set to a sufficiently wide angle of view. Further, it is also necessary to suppress various aberrations, such as chromatic aberration of magnification, which are likely to occur strongly with a wide angle of view. Also, with regard to rear projection for projecting a screen from the back, a very wide angle of view is required even if the screen is not shifted from the optical axis because the size of the device is required to be reduced. Even in this case, it is necessary to sufficiently correct the chromatic aberration of magnification which largely affects the quality of the image.

  Against this background, in order to appreciate a large screen in various usage environments in a limited space, the projection optical system is bright, high-definition, yet further compact, wide-angle, high magnification, etc. Is required.

  Patent Documents 1 and 2 realize a wide angle of view using a coaxial optical system. In Patent Document 1, the ratio of the focal length of the entire system to the focal length of the front group is regulated by a configuration including the front group and the rear group, thereby maintaining the group spacing, the back focus, and the telecentricity, while suppressing spherical aberration and coma. Correction has been performed. This achieves a wide angle of view of at least a half-angle of view of 35 ° while securing a group distance for inserting a return mirror for a back focus in which a dichroic mirror can be inserted and for miniaturization by layout of an optical system. .

  Patent Document 2 discloses a zoom lens having a five-group configuration, in which a diffractive optical element is appropriately set in a predetermined lens group to correct chromatic aberration of magnification, and to reduce the size of the entire lens system. Thus, a zoom lens in which various aberrations are sufficiently corrected while maintaining a large aperture of about Fno2 at a zoom ratio of 1.2 or more and maintaining back focus and telecentricity has been proposed.

  On the other hand, a projection optical system capable of projecting an image obliquely on a screen has been made in order to perform image projection without obstructing the field of view of an observer in front projection and to reduce the size of rear projection. However, since a so-called trapezoidal distortion is generated by projecting the screen obliquely, an invention for correcting the trapezoidal distortion has been made. For example, in Patent Document 3, trapezoidal distortion is corrected using an eccentric aspheric surface.

  In a non-coaxial optical system, a design method and a calculation method of a paraxial amount such as a focal length are described in Patent Literature 4, and a reference axis is shown in Patent Literature 5, Patent Literature 6, and Patent Literature 7 as design examples are shown in Patent Literature 7. It has become clear that by introducing the concept and making the constituent surfaces asymmetrical aspherical surfaces, it is possible to construct an optical system in which aberrations are sufficiently corrected. Such a non-coaxial optical system is an Off-Axial optical system (when considering a reference axis along a ray passing through the center of the image and the center of the pupil, a curved surface whose surface normal at the intersection with the reference axis of the constituent surface is not on the reference axis) (In this case, the optical system is defined as an optical system including an (Off-Axial curved surface), and at this time, the reference axis has a bent shape.) In this Off-Axial optical system, the constituent surface is generally non-coaxial, and there is no vignetting even on the reflecting surface. Therefore, it is easy to construct an optical system using the reflecting surface. Also, by forming an intermediate image in the optical system, a compact optical system having a high angle of view is formed. Further, a compact optical system can be configured because the optical path can be relatively freely routed even though the optical system is a front stop. Taking advantage of these facts, Patent Documents 8 and 9 correct trapezoidal distortion using a rotationally asymmetric reflective surface having a curvature.

Patent Document 10 discloses an optical system including an optical element having a plurality of optical working surfaces including at least one reflecting surface, and having a longitudinal direction in which an optical working surface adjacent to the optical working surfaces is disposed. The optical system is characterized in that the optical element is moved in and out of the optical path in a direction different from the longitudinal direction to change the paraxial amount of the system. This makes it possible to replace the magnifying-side reflecting optical block with one having a different focal length, in addition to the zooming function of the coaxial optical system on the reduction side, thereby expanding the zooming range of the entire optical system.
JP-A-11-109227 JP-A-2002-182110 JP-A-10-282451 JP 09-005650 A JP 08-292371 A JP 08-292372 A JP-A-09-222561 JP 2001-255462 A JP 2000-089227 A JP 2001-264633 A

  According to Patent Literature 1, it is expected that it will be difficult to maintain a compact optical system while correcting various aberrations such as chromatic aberration of magnification, as the angle of view widens to a half angle of view of 40 ° or more in the future. Further, since the embodiment does not have a zooming function, it is suitable for use at a fixed angle of view as in rear projection, but unsuitable for use in front projection.

  In Patent Document 2, although the number of lenses is reduced and the chromatic aberration of magnification is suppressed by using a diffractive optical element, the zoom ratio remains at 1.2, and the fundamental solution for increasing the zoom ratio is as follows. Therefore, it is not possible to expect a wide angle of view and a high zoom ratio.

  Patent Literature 3 corrects trapezoidal distortion using an eccentric aspherical surface. However, the amount of shift of the screen is limited, and it is not suitable for a projector because it is not telecentric with respect to a liquid crystal panel. Patent Documents 8 and 9 realize wide-angle trapezoidal distortion correction using a rotationally asymmetric reflecting surface having a curvature. However, these methods are specialized for oblique projection. This is not an embodiment having a zooming function.

  Further, in the imaging system, Patent Document 7 discloses that an optical element formed of a coaxial refracting surface and an integrally formed optical element having surface mirrors decentered from each other are used, and the relative positions of at least two elements are changed. Is changing the magnification. However, when tracing light rays from the image sensor side, the coaxial optical system forms an image at approximately the same magnification at the wide-angle end with the reflective optical system, and the magnification of the reflective optical system further increases at the telephoto end. ing. For this reason, various aberrations generated in the coaxial optical system having the variable power function are enlarged in the reflection optical system, and it becomes impossible to correct various aberrations. Also, since the coaxial optical system forms an image once with the reflective optical system, and the image is enlarged by the reflective optical system, the magnification of the coaxial optical system is reduced in order to suppress the expansion of aberration by the reflective optical system. Even if the share is increased, it is not suitable for downsizing the optical system.

  Further, in Patent Document 10, magnifications of the image sensor of the coaxial optical system in the examples as an object plane are −0.59 at the wide-angle end, −0.87 at the middle, and −1.23 at the telephoto end. Particularly at the wide-angle end, since the reflection optical block has a higher magnification, this is also an optical system in which the aberration is easily enlarged.

  In view of the above, it is an object of the present invention to provide a variable power optical system having a compact configuration while suppressing the occurrence of various aberrations such as chromatic aberration of magnification while obtaining a desired variable power ratio.

  In order to solve the above problems, a variable power optical system as an example of the present invention is configured to enlarge an image on a reduction side onto a predetermined image plane on an enlargement side or reduce an image on the enlargement side to a predetermined image plane on a reduction side. This is a variable power optical system for projecting. This variable power optical system has a first optical component and a second optical component arranged on the reduction side with respect to the first optical component. The first optical component has a reflection curved surface. The second optical component has a plurality of movable lens units, and performs zooming by moving the plurality of lens units. Then, when tracing a light ray from the reduction side to the enlargement side, the second optical component forms an image of a reduction side conjugate point on the enlargement side from the optical surface of the first optical component on the most reduction side.

  According to the present invention, it is possible to realize a variable-magnification optical system having a wide field angle and a high zoom ratio, and having a compact configuration that is bright and suppresses the occurrence of chromatic aberration of magnification.

  Before starting the description of the embodiment, a description will be given of a method of expressing the configuration data of the embodiment and common matters of the entire embodiment. FIG. 9 is an explanatory diagram of a coordinate system that defines the configuration data of the optical system. In this embodiment, the i-th surface is defined as the i-th surface along one light ray (shown by a dashed line in FIG. 9 and referred to as a reference axis light ray) that travels from the reduction side to the image plane on the enlargement side. In the present description, a target plane on which an image is projected is expressed as a screen or a predetermined image plane, and a projected image is expressed as an image, an image plane, or a screen, and can be freely substituted. Further, in the embodiment, a description will be given of a form in which the image is projected on a predetermined image plane on the enlargement side with the reduction side as the object plane, but the reduction projection may be performed on the opposite optical path.

  In FIG. 9, the first surface R1 is a refraction surface, the second surface R2 is a reflection surface tilted with respect to the first surface R1, and the third surface R3 and the fourth surface R4 are shifted and tilted with respect to each front surface. The reflecting surface and the fifth surface R5 are refracting surfaces shifted and tilted with respect to the fourth surface R4. Each surface from the first surface R1 to the fifth surface R5 is formed on one optical element made of a medium such as glass or plastic, and is referred to as a first optical element B in FIG.

  Therefore, in the configuration of FIG. 9, the medium from the object surface (not shown) to the first surface R1 is air, the common medium is from the first surface R1 to the fifth surface R5, and the sixth surface (not shown) from the fifth surface R5. The medium up to R6 is composed of air.

  Since the optical system of the present embodiment is an Off-Axial optical system, each surface constituting the optical system does not have a common optical axis. Therefore, first, an absolute coordinate system having the center of the first surface as the origin is set.

  The path of a light ray (reference axis light ray) passing through the origin and the center of the final imaging plane is defined as a reference axis of the optical system. Further, the reference axis in the present embodiment has a direction (direction). The direction is the direction in which the reference axis ray travels.

  In the present embodiment, the reference axis serving as the reference of the optical system is set as described above. However, how to determine the reference axis of the optical system depends on the optical design, the arrangement of aberrations, or each surface constituting the optical system. Any axis that is convenient for expressing the shape may be used. However, in general, the path of a light ray passing through the center of the image plane and either the stop, the entrance pupil or the exit pupil, or the center of the first surface or the center of the last surface of the optical system is referred to as a reference axis serving as a reference of the optical system. Set to.

  That is, in this embodiment, the reference axis passes through the center point of the first surface, and the path along which the light (reference axis light) reaching the center of the final imaging plane is refracted / reflected by each refraction surface and reflection surface is referred to as the reference axis. Is set to The order of each surface is set in the order in which the reference axis rays are refracted and reflected.

  Therefore, the reference axis finally reaches the center of the image plane while changing its direction along the set order of each surface according to the law of refraction or reflection. The terms “reduced side”, “panel surface side”, “object plane side”, and “enlarged side”, “predetermined image plane side”, and “screen side” mean on which side the object is located along the direction of the reference axis.

Each axis of the absolute coordinate system of the optical system in each embodiment of the present invention is determined as follows. Z axis: A straight line passing through the origin and the center of the object plane. Y-axis whose direction from the object plane toward the first surface R1 is positive Y-axis: a straight line passing through the origin and forming 90 ° counterclockwise with respect to the Z-axis in the plane of the paper according to the definition of the right-handed coordinate system X-axis: passing through the origin Straight lines perpendicular to each of the Z and Y axes. Also, to express the surface shape and tilt angle of the i-th surface that constitutes the optical system, the reference axis and the tilt axis are expressed rather than expressing the surface shape and tilt angle in an absolute coordinate system. A local coordinate system having the origin at the point where the i-th surface intersects is set, the surface shape of the surface is represented by the local coordinate system, and the tilt angle is represented by the angle formed by the reference axis and the local coordinate system. For easy understanding upon recognition, the surface shape of the i-th surface is expressed by the following local coordinate system. For that purpose, first, the following coordinate system on the reference axis is set for an arbitrary point on the reference axis.
zb axis: The direction of the reference axis passes through an arbitrary point on the reference axis and is positive. At the deflection point of the reference axis, the yb axis whose incident direction is positive: a straight line passing through any point on the reference axis and forming 90 ° counterclockwise with respect to the zb axis in the plane of the drawing according to the definition of the right-handed coordinate system Xb axis: coincides with the Y axis of the absolute coordinate system at the origin of the absolute coordinate system, and does not rotate thereafter with respect to the zb axis. Xb axis: passes through an arbitrary point on the reference axis and is perpendicular to the zb and yb axes. Next, set the local coordinate system.
z-axis: surface normal passing through the origin of local coordinates y-axis: straight line passing through the origin of local coordinates and making 90 ° counterclockwise to the z-direction in the paper according to the definition of the right-handed coordinate system x-axis: local coordinates Therefore, the tilt angle of the i-th surface in the ybzb plane is such that the z-axis of the local coordinate system is acutely counterclockwise with respect to the zb-axis of the coordinate system on the reference axis. Θxb, i (degrees), and the tilt angle of the i-th surface in the xbzb plane is the angle θyb, i (degrees) with the counterclockwise direction positive with respect to the zb axis of the coordinate system on the reference axis. The tilt angle of the i-th plane in the xbyb plane is represented by an angle θzb, i (degree) with the counterclockwise direction being positive with respect to the yb axis of the absolute coordinate system. However, θzb, i usually corresponds to the rotation of the surface and does not exist in the embodiment of the present invention. FIG. 10 shows the relationship among the absolute coordinate system, the coordinate system on the reference axis, and the local coordinate system.

  Di is a scalar representing the distance between the origins of the local coordinates between the i-th surface and the (i + 1) -th surface, and Ndi and νdi are the refractive index and Abbe number of the medium between the i-th and the (i + 1) -th surface. is there.

  Here, the spherical surface has a shape represented by the following equation:

Further, the optical system of this embodiment has at least one or more rotationally asymmetric aspheric surfaces, and the shape is represented by the following equation:
^{z = C02y 2 + C20x 2 +} C03y 3 + C21x 2 y + C04y 4 + C22x 2 y 2 + C40x 4 + C05y 5 + C23x2y 3 + C41x 4 y + C06y 6 + C24x 2 y 4 + C42x 4 y 2 + C60x 6
Since the above-mentioned curved surface expression has only even-order terms with respect to x, the curved surface defined by the above-mentioned curved surface expression has a plane-symmetric shape with the yz plane as a symmetric surface. Further, when the following condition is satisfied, the shape is symmetric with respect to the xz plane.

C03 = C21 = C05 = C23 = C41 = t = 0
Further, C02 = C20 C04 = C40 = C22 / 2 C06 = C60 = C24 / 3 = C42 / 3
Is satisfied, a rotationally symmetric shape is represented. If the above conditions are not satisfied, the shape is non-rotationally symmetric.

  Next, the configuration of a variable power optical system according to the present embodiment will be described with reference to FIGS. 1, 2, and 3. FIG. However, the numerical details will be described later. FIG. 1 is a diagram illustrating the entire configuration of an optical system, FIG. 2 is a diagram illustrating an optical path of only a reduction-side optical block (second optical component) excluding an enlargement-side optical block (first optical component) from FIG. FIG. 3 is a diagram in which the optical block on the enlargement side is superimposed on the image forming optical path of the optical block on the reduction side shown in FIG. In FIGS. 1 and 2, (a) shows the state at the wide-angle end, (b) shows the state at the intermediate focal length, and (c) shows the state at the telephoto end.

  1 to 3, L denotes an illumination system which illuminates an image display panel (light valve) LV using a transmission liquid crystal, a reflection dot matrix liquid crystal, a digital micromirror device, or the like. The illumination system L includes a lamp, a condenser lens, a filter for selecting a wavelength, and the like, and is omitted in FIGS. 1B and 1C and FIGS. 2B and 2C. D is a dichroic optical element that performs photosynthesis corresponding to a three-plate image display panel. As described above, the optical system of the present embodiment is an optical system for a three-plate system, but FIG. 1 does not show the optical path diagram of only one image display panel. In the following description, as described above, it is assumed that light travels from the image display panel LV side (reduction side) to a screen side (magnification side) (not shown) on which an image of the image display panel LV is projected. Explanation is given.

  C is an optical block on the reduction side corresponding to the second optical component, and is constituted by a rotationally symmetric coaxial lens having a zooming function. The optical block C performs zooming from the wide-angle end (short focal length end) to the telephoto end (long focal length end) by moving a lens unit constituting the optical block C along the optical axis. R is an enlargement side optical block corresponding to the first optical component. R1 to R3 constituting the optical block R are Off-Axial reflecting surfaces, which are arranged eccentrically to each other. The reflecting surfaces R1 to R3 constituting the optical block R are stationary during zooming. The exit pupil of the optical block C coincides with the entrance pupil of the optical block R. In the figure, EXP is the pupil of the variable power optical system, which corresponds to the exit pupil of the optical block C and the entrance pupil of the optical block R. , An aperture stop is arranged. That is, the pupil EXP of the variable power optical system is located on the reduction side of the optical block R and on the enlargement side of the image display panel LV corresponding to the conjugate point on the reduction side. “Reduction side of the optical block R” means “reduction side of the optical surface of the optical block R closest to the reduction side”.

  In Japanese Unexamined Patent Publication No. 9-222561 described in the section of the conventional example, a coaxial optical system (corresponding to the optical block C of the present embodiment) and a reflecting optical system (corresponding to the optical block R of the present embodiment) are provided. Although an image was formed, in this embodiment, the image of the image display panel LV by the optical block C on the reduction side is a real image on the enlargement side of the optical block C and the optical surface of the optical block R on the most reduction side. It is formed in the optical path of the optical block R on the enlargement side of the (reflection surface R1). That is, by positioning the pupil on the reduction side of the optical block R and on the enlargement side of the image display panel LV, the optical path to the intermediate image and the image partially overlaps with the optical path of the optical block R on the enlargement side and is absorbed. Therefore, the entire optical system can be made compact as compared with the conventional example in which an image is formed between optical blocks and relay is performed. Further, since the reflection surface of the optical block R on the reduction side from the intermediate image shares the image forming action of the optical block C, it also suppresses various aberrations such as chromatic aberration of magnification. Since the light can be arranged without vignetting, the brightness is not impaired over the periphery of the image plane.

  Next, a detailed configuration of the optical block C on the reduction side will be described with reference to FIG. In FIG. 2, reference numerals L1 to L5 denote lens units constituting the optical block C. In the order from the reduction side, a fixed lens unit L1 composed of a lens having a positive power (a reciprocal of the focal length) and a bonding unit having a negative power Movable lens unit L2 consisting of a cemented lens, movable lens unit L3 consisting of a cemented lens with negative power, movable lens unit L4 consisting of a rotationally symmetric aspheric lens with positive power, negative power , And has a positive power as a whole. However, the sign of the power of the lens units L1 to L5 is not limited to this.

  As shown in FIG. 2, only the optical block C on the reduction side forms an image of the image display panel in a spherical SP shape. The spherical image is enlarged or reduced by moving the lens units L2 to L5. This spherical image is transformed by the optical block R on the enlargement side so as to form a plane image on a predetermined image plane (screen). The optical block C forms a plane image, and the optical block R on the enlargement side produces a planar image. The image may be re-imaged from to a plane.

  FIG. 3 is a diagram in which the optical paths of the optical block R are overlapped while the image forming light flux of the optical block C shown in FIG. 2 is illustrated. The optical paths of the two optical blocks are combined such that the exit pupil of the optical block C matches the entrance pupil of the optical block R. Actually, as shown in FIG. 1, the image forming light flux from the optical block C is guided to the optical block R, and is reflected at each reflecting surface. As shown in FIG. 3, since the image forming plane of the optical block C is taken into the optical block R on the enlargement side, the focal length of the optical block C is increased and a magnification having a large absolute value is provided. However, the optical system can be made compact.

  Further, since the reflecting surfaces R1 to R3 constituting the optical block R on the enlargement side are arranged in the air in this embodiment, chromatic aberration does not occur. Even if the enlargement side optical block R is filled with an optical material such as glass or plastic, chromatic aberration can be suppressed as described in JP-A-09-222563 and JP-A-10-221604. is there.

  FIGS. 4A and 4B show the state of projection at each zooming position of the zooming optical system of this embodiment. FIG. 4A shows the state at the wide angle end, FIG. 4B shows the intermediate focal length, and FIG. 4C shows the state at the telephoto end. is there.

  In FIG. 4, P denotes a variable power optical system of the present embodiment, E denotes a screen (predetermined image plane), and S denotes an image plane (screen). The size of the image display panel LV is 0.7 inches (10.668 × 14.224 mm) with an aspect ratio of 3: 4, and the projection distance (P) from the variable power optical system P to the image plane S along the reference axis is P. The distance from the center of the exit pupil to the center of S is approximately 1700 mm, and is a 2 × zoom optical system from the wide-angle end of 70 inches (1422.4 × 1066.8 mm) to the telephoto end of 35 inches (711.2 × 533.4 mm). It has become. The variable power optical system of this embodiment is telecentric on the image display panel side.

At this time, the focal length of the optical block C ′ on the reduction side is 46.87 mm to 92.85 mm from the wide-angle end, and the magnification values are −4.08, −3.07, −2.05 (at the wide-angle end, Middle, telephoto end). That is, when the magnification of the optical block C when tracing the light beam from the reduction side to the enlargement side is b1,
b1 <-1
Satisfies the following conditions. In this way, by making the optical block C on the reduction side share a magnification smaller than −1 (larger in absolute value), it is possible to suppress the expansion of aberration in the optical block R on the enlargement side. When the magnification of the optical block C is larger than -1 and smaller than 0, the optical block on the enlargement side enlarges various aberrations generated in the optical block C with a very large magnification, and the occurrence of aberration is suppressed. Is not preferred. In the present embodiment, when the expression that the magnification is high (large) or low (small) is used without explanation, it means that the absolute value is large or small.

  Hereinafter, configuration data of the variable power optical system of the present embodiment will be shown.

  FIGS. 5A, 5B, and 5C show distortion at the wide-angle end, the middle end, and the telephoto end in the variable power optical system of the present embodiment. FIGS. 6, 7, and 8 show lateral aberration diagrams at the wide-angle end, the middle position, and the telephoto end at the evaluation positions (1) to (5) in FIG. As can be seen from FIG. 5, there is no large distortion and there is little asymmetric distortion. The axes of the lateral aberration diagrams in FIGS. 6, 7, and 8 are defined such that the horizontal axis is the x or y axis on the pupil plane, and the vertical axis is the amount of aberration on the screen. It can be seen that the images are formed well.

  As described above, in the variable power optical system disclosed in this embodiment, by performing the variable power function by the refraction system (optical block C) on the reduction side, variable power can be achieved by a simple method of moving the lens. Since magnification can be gained by the magnifying-side reflecting system (optical block R), a compact and high-performance zooming optical block can be achieved relatively easily as the reducing-side optical block while achieving a high zooming ratio. it can. Further, by using a reflection system as the optical block on the enlargement side, it is possible to suppress chromatic aberration of magnification that is likely to occur in a conventional refraction system even in an optical system having a high magnification as a whole.

  Further, by always making the magnification of the optical block on the reduction side smaller than −1 during zooming, it is possible to prevent the magnification of the optical block on the enlargement side from becoming high and to suppress the enlargement of aberration.

  Further, if the optical block on the enlargement side is an Off-Axial reflection optical system, an asymmetry of the system can be generated and the image can be projected obliquely on a predetermined image plane to form an image. An optical system having a smaller volume than the conventional method of projecting using a part of the corner can be achieved. Also, front projection is effective in securing the field of view of the observer and improving the degree of freedom of the installation position of the projection device. In rear projection, the degree of freedom in the layout of the optical system is increased, which is effective in miniaturization.

FIG. 1 is an overall configuration diagram of a variable power optical system according to the present embodiment. FIG. 2 is a configuration diagram of an optical block on a reduction side of the variable power optical system shown in FIG. 1. FIG. 3 is a diagram in which an optical block on the enlargement side is superimposed on an image forming optical path of the optical block on the reduction side shown in FIG. FIG. 4 is a diagram illustrating a state of projection at each variable power position of the variable power optical system of the present embodiment. FIG. 4 is an explanatory diagram illustrating distortion of the variable power optical system of the present example. FIG. 4 is an explanatory diagram illustrating lateral aberration at the wide end of the variable power optical system according to the present embodiment. FIG. 4 is an explanatory diagram illustrating lateral aberrations at a middle position of the variable power optical system of the present example. FIG. 4 is an explanatory diagram showing lateral aberrations at the telephoto end of the variable power optical system of the present example. It is an explanatory view of a coordinate system. FIG. 3 is an explanatory diagram of an absolute coordinate system, a coordinate system on a reference axis, and a local coordinate system. It is explanatory drawing which shows the evaluation position of a lateral aberration.

Explanation of reference numerals

P Variable power optical system B Optical element L Illumination system LV Light valve (image display panel)
C Coaxial rotationally symmetric optical block D Dichroic optical element R Optical block having a reflective surface with curvature as a component Ri i-th Off-axial reflective free-form surface E Projection effective area (extended screen)
S Image display surface Si Image display position EXP Exit pupil of optical block on reduction side b1 Magnification of optical block on reduction side (i = 1, 2, ‥‥)

Claims (6)

  A first optical component having a reflection curved surface; a movable plurality of movable optical systems; a first optical component having a reflective curved surface; And a second optical component disposed on a reduction side with respect to the first optical component, wherein the second optical component is disposed on the reduction side with respect to the first optical component. The variable power optical system, wherein the second optical component forms an image of a conjugate point on the reduction side on the enlargement side of the optical surface on the reduction side of the first optical component.   2. The variable power optical system according to claim 1, wherein when tracing a ray from a reduction side to an enlargement side, the second optical component forms an image of a reduction side conjugate point in the first optical component. .   3. The variable power optical system according to claim 1, wherein a pupil of the variable power optical system is located on a reduction side of the first optical component and on an enlargement side of a reduction side conjugate point. 4.   The variable power optical system according to claim 1, wherein a pupil of the variable power optical system is located between the first optical component and the second optical component. When tracing a light beam from the reduction side to the enlargement side, the magnification b1 of the second optical component is:
b1 <-1
5. The variable power optical system according to claim 1, wherein the following condition is satisfied at an arbitrary variable power position. A projector comprising: an image display unit; and the variable power optical system according to claim 1 for projecting an image of the image display unit.

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