JP2017187662A - Projection optical system and projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection optical system that comprises a relatively small number of lenses and yet can cover a wide zoom range, and to provide a projector having the same.SOLUTION: A projection optical system comprises, in order from the reduction side, a first optical group comprising a plurality of lenses and having positive power, and a second optical group having a reflective surface of an aspherical concave shape. The first optical group comprises a 1-1 lens group having positive power and a 1-2 lens group having negative power with an air gap therebetween. The 1-2 lens group, which is a focusing lens group, consists of a lens F1 comprising a single positive lens having a convex surface on the reduction side, a lens F2 comprising a single negative meniscus lens having a convex surface on the expansion side, and a lens F3 comprising a single negative lens. The 1-2 lens group is configured to move for focusing while zooming.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a projection optical system suitable for incorporation into a projector that magnifies and projects an image of an image display element, and a projector using the same.

  In recent years, as a projection optical system for a projector capable of projecting from a short distance and obtaining a large screen, one using a refractive optical system and a concave mirror has been proposed (see, for example, Patent Documents 1 and 2).

  However, for example, in Patent Document 1 (Japanese Patent Laid-Open No. 2006-235516), a very wide angle of view is realized using a refractive optical system and a concave mirror, but the curved mirror is very large and the total length is also very large. It has become a long thing. In Patent Document 2 (Japanese Patent Application Laid-Open No. 2007-079524), for example, the mirror size is reduced by combining a concave mirror and a convex mirror while the angle of view is about 60 degrees in the eighth embodiment. However, like the above-mentioned Patent Document 2, the total length is very long. In addition, the two mirrors that are configured are aspherical, and are extremely difficult to manufacture from the viewpoint of accuracy and assembly.

  As described above, in the composite optical system of the refractive optical system and the concave mirror, an ultra-wide field angle can be obtained, but it is difficult to reduce the total length. Therefore, the composite optical system is not suitable for a device that places importance on portability, such as a front projector.

JP 2006-235516 A JP 2007-079524 A

  The present invention has been made in view of the above background, and provides a projection optical system capable of covering a wide zooming range while including a relatively small number of lenses, and a projector including the projection optical system. With the goal.

  In order to achieve the above object, a projection optical system according to the present invention includes, in order from the reduction side, a first optical group including a plurality of lenses and having a positive power, and a reflecting surface having a single concave aspherical shape. A projection optical system comprising a second optical group, wherein the first optical group is fixed at the time of focusing accompanying zooming and has positive power at the widest air interval. The first lens unit includes a first lens unit and a first lens unit that moves when focusing with zooming and has a negative power as a whole. Three lenses: an F1 lens composed of one positive lens having a convex surface, an F2 lens composed of one negative meniscus lens having a convex surface on the enlargement side, and an F3 lens composed of one negative lens. It is characterized by being configured.

  In the projection optical system, the first-second lens group is disposed on the enlargement side of the first optical group, and requires a relatively large lens. In the projection optical system, the first-second lens group includes an F1 lens including one positive lens having a convex surface on the reduction side, and an F2 lens including one negative meniscus lens having a convex surface on the enlargement side. By having an F3 lens composed of one negative lens, a desired zooming range can be covered. And the whole projection optical system can be made compact.

  According to a specific aspect of the present invention, the 1-1st lens group has an aperture stop inside the 1-1st lens group, and is a positive lens having a convex aspheric surface on the reduction side of the aperture stop. Includes a lens. In this case, even if the first-second lens group is a simple lens composed of three lenses, it is possible to obtain a high-contrast image with little flare. Further, the total lens length can be shortened by suppressing the number of constituent lenses.

  According to another aspect of the present invention, the 1-1st lens group includes an aperture stop inside the 1-1st lens group, and includes a positive lens including at least one positive lens on the enlargement side of the aperture stop. A lens group having the following power is provided. In this case, the state of the light bundle is adjusted in the first-first lens group that takes in the light bundle emitted from the object side (hereinafter also referred to as a light beam) and sends it to the first-second lens group. Thus, an appropriate primary image (intermediate image) can be created with the first-second lens group in a wide zooming range.

  According to still another aspect of the present invention, the 1-1st lens group has an aperture stop inside the 1-1st lens group, and two positive lenses on the reduction side of the aperture stop, A first cemented lens composed of a positive lens and a negative lens and a second cemented lens composed of a positive lens and a negative lens are included. In this case, it is possible to prevent the occurrence of chromatic aberration, for example, by including a cemented lens in the first-first lens group.

  According to still another aspect of the present invention, the 1-1st lens group has an aperture stop inside the 1-1st lens group, and has a negative aspheric shape on at least one surface in the vicinity of the aperture stop. A lens is placed. Here, the lens arranged in the vicinity of the aperture stop means a lens closest to the aperture stop among the lenses constituting the projection optical system. In this case, the numerical aperture on the object side can be increased by using a lens disposed in the vicinity of the aperture stop as a negative lens having an aspheric shape on at least one surface.

  According to still another aspect of the present invention, the first-second lens group moves the three lenses into at least two lens groups, respectively. In this case, it is possible to create a primary image (intermediate image) that can finally obtain a good image even in a wide zoom range (for example, 1.5 times or more).

  According to still another aspect of the present invention, the F3 lens is a double-sided aspheric lens formed of resin. According to this configuration, like the F3 lens, it tends to be large because it is arranged on the magnification side of the first optical group, and it is easy to make even if it has aspheric surfaces on both sides. Moreover, there is a possibility that the F3 lens interferes with the light beam returned by the reflecting mirror constituting the second optical group. For this reason, it may be necessary to cut out a part of the lens constituting the F3 lens. However, by using resin molding, the lens can be easily formed into a non-circular shape or the like.

  According to still another aspect of the present invention, the F3 lens has a concave shape on the reduction side in the vicinity of the optical axis. In this case, it is easy to make the F2 lens into a negative meniscus lens shape having a convex surface on the enlargement side.

  According to still another aspect of the present invention, the numerical aperture on the object side is 0.3 or more. In this case, a sufficiently bright projection image can be formed.

  According to yet another aspect of the invention, the reduction side is substantially telecentric.

  According to still another aspect of the present invention, all the elements constituting the first optical group and the second optical group are rotationally symmetric systems.

  According to still another aspect of the present invention, the zooming range is 1.5 times or more.

  In order to achieve the above object, a projector according to the present invention includes a light modulation element that modulates light from a light source to form image light, and any one of the above-described projection optical systems that projects image light from the light modulation element. Is provided. By providing any one of the above-described projection optical systems, the projector can cover a desired zooming range with a configuration in which the number of lenses is suppressed.

It is a figure which shows schematic structure of the projector incorporating the projection optical system of embodiment. It is a structure and light ray figure from an object surface in a projection optical system of an embodiment or Example 1 to a projection surface. FIG. 3 is a partially enlarged view from the object plane to the concave reflecting mirror in FIG. 2. 1 is a diagram illustrating a configuration of a projection optical system according to Example 1. FIG. FIGS. 4A to 4C are reduction side aberration diagrams of the projection optical system of Example 1. FIGS. FIGS. 5A to 5E are lateral aberration diagrams of the projection optical system corresponding to FIG. FIGS. 5A to 5E are lateral aberration diagrams of the projection optical system corresponding to FIG. FIGS. 5A to 5E are lateral aberration diagrams of the projection optical system corresponding to FIG. FIG. 6 is a diagram illustrating a configuration of a projection optical system of Example 2. FIGS. 4A to 4C are reduction side aberration diagrams of the projection optical system of Example 2. FIGS. FIGS. 10A to 10E are lateral aberration diagrams of the projection optical system corresponding to FIG. FIGS. 10A to 10E are lateral aberration diagrams of the projection optical system corresponding to FIG. FIGS. 10A to 10E are lateral aberration diagrams of the projection optical system corresponding to FIG. FIG. 6 is a diagram illustrating a configuration of a projection optical system according to Example 3. FIGS. 4A to 4C are reduction side aberration diagrams of the projection optical system according to Example 3. FIGS. (A)-(E) are lateral aberration diagrams of the projection optical system corresponding to FIG. (A)-(E) are lateral aberration diagrams of the projection optical system corresponding to FIG. 15 (B). (A)-(E) are lateral aberration diagrams of the projection optical system corresponding to FIG. FIG. 10 is a diagram illustrating a configuration of a projection optical system according to Example 4. FIGS. 6A to 6C are reduction side aberration diagrams of the projection optical system of Example 4. FIGS. (A)-(E) are lateral aberration diagrams of the projection optical system corresponding to FIG. (A)-(E) are lateral aberration diagrams of the projection optical system corresponding to FIG. (A)-(E) are lateral aberration diagrams of the projection optical system corresponding to FIG.

  Hereinafter, a projection optical system according to an embodiment of the present invention will be described in detail with reference to the drawings.

  As shown in FIG. 1, a projector 2 incorporating a projection optical system according to an embodiment of the present invention includes an optical system portion 50 that projects image light, and a circuit device 80 that controls the operation of the optical system portion 50. Prepare.

  In the optical system portion 50, the light source 10 is an ultra-high pressure mercury lamp, for example, and emits light including R light, G light, and B light. Here, the light source 10 may be a discharge light source other than an ultra-high pressure mercury lamp, or may be a solid light source such as an LED or a laser. The first integrator lens 11 and the second integrator lens 12 have a plurality of lens elements arranged in an array. The first integrator lens 11 splits the light flux from the light source 10 into a plurality of parts. Each lens element of the first integrator lens 11 condenses the light beam from the light source 10 in the vicinity of the lens element of the second integrator lens 12. The lens elements of the second integrator lens 12 cooperate with the superimposing lens 14 to form images of the lens elements of the first integrator lens 11 on the liquid crystal panels 18R, 18G, and 18B. With such a configuration, the light from the light source 10 illuminates the entire display area of the liquid crystal panels 18R, 18G, and 18B with substantially uniform brightness.

  The polarization conversion element 13 converts light from the second integrator lens 12 into predetermined linearly polarized light. The superimposing lens 14 superimposes the image of each lens element of the first integrator lens 11 on the display area of the liquid crystal panels 18R, 18G, and 18B via the second integrator lens 12.

  The first dichroic mirror 15 reflects R light incident from the superimposing lens 14 and transmits G light and B light. The R light reflected by the first dichroic mirror 15 passes through the reflection mirror 16 and the field lens 17R and enters the liquid crystal panel 18R that is a light modulation element. The liquid crystal panel 18R forms an R color image by modulating the R light according to the image signal.

  The second dichroic mirror 21 reflects the G light from the first dichroic mirror 15 and transmits the B light. The G light reflected by the second dichroic mirror 21 passes through the field lens 17G and enters the liquid crystal panel 18G that is a light modulation element. The liquid crystal panel 18G modulates the G light according to the image signal to form a G color image. The B light transmitted through the second dichroic mirror 21 passes through the relay lenses 22 and 24, the reflection mirrors 23 and 25, and the field lens 17B and enters the liquid crystal panel 18B that is a light modulation element. The liquid crystal panel 18B forms a B-color image by modulating the B light according to the image signal.

  The cross dichroic prism 19 is a light combining prism, which combines light modulated by the liquid crystal panels 18R, 18G, and 18B into image light and advances it to the projection optical system 40.

  The projection optical system 40 is a projection zoom lens that enlarges and projects the image light modulated by the liquid crystal panels 18G, 18R, and 18B and synthesized by the cross dichroic prism 19 onto a screen (not shown).

  The circuit device 80 includes an image processing unit 81 to which an external image signal such as a video signal is input, and display driving for driving the liquid crystal panels 18G, 18R, and 18B provided in the optical system portion 50 based on the output of the image processing unit 81. Unit 82, a lens driving unit 83 that adjusts the state of the projection optical system 40 by operating a drive mechanism (not shown) provided in the projection optical system 40, and the operations of these circuit portions 81, 82, 83, etc. And a main control unit 88 for controlling automatically.

  The image processing unit 81 converts the input external image signal into an image signal including a gradation of each color. The image processing unit 81 can also perform various image processing such as distortion correction and color correction on the external image signal.

  The display driving unit 82 can operate the liquid crystal panels 18G, 18R, and 18B based on the image signal output from the image processing unit 81, and can display an image corresponding to the image signal or an image that has been subjected to image processing. Corresponding images can be formed on the liquid crystal panels 18G, 18R, 18B.

  The lens driving unit 83 operates under the control of the main control unit 88, and appropriately moves a part of the optical elements constituting the projection optical system 40 along the optical axis OA via the actuator AC. In the projection of the image on the screen by 40, it is possible to perform focus accompanying zooming (focus during zooming). The lens driving unit 83 can also change the vertical position of the image projected on the screen by adjusting the tilt of moving the entire projection optical system 40 in the vertical direction perpendicular to the optical axis OA.

  Hereinafter, the projection optical system 40 according to the embodiment will be described in detail with reference to FIGS. The projection optical system 40 illustrated in FIG. 2 and the like has the same configuration as the projection optical system 40 of Example 1 described later.

  The projection optical system 40 of the embodiment projects an image formed on the liquid crystal panel 18G (18R, 18B) on a screen (not shown). Here, a prism PR corresponding to the cross dichroic prism 19 of FIG. 1 is disposed between the projection optical system 40 and the liquid crystal panel 18G (18R, 18B).

  The projection optical system 40 includes, in order from the reduction side, a first optical group 40a that includes a plurality of lenses and has positive power, and a second optical group 40b that includes a mirror MR including a reflecting surface having a concave aspherical shape. Consists of. The first optical group 40a is provided on the reduction side with the widest air interval BD in the space formed between the included lenses as a boundary, and the first lens group 41 having a positive power and an enlargement And a first-second lens group 42 having a negative power weaker than the power of the first-first lens group 41.

  The 1-1st lens group 41 has an aperture stop ST inside the 1-1st lens group 41, a lens group E1 on the reduction side with respect to the aperture stop ST, and a lens group E2 on the enlargement side with respect to the aperture stop ST. It consists of.

  The first-second lens group 42 includes, in order from the reduction side, an F1 lens (hereinafter referred to as a lens F1), an F2 lens (hereinafter referred to as a lens F2), and an F3 lens (hereinafter referred to as a lens F3). Each of the lens F1, the lens F2, and the lens F3 moves in the optical axis direction during focusing accompanying zooming. Among the lenses F1 to F3, the lens F1 located closest to the reduction side is a positive lens (lens L12) having a convex surface on the reduction side, and the lens F2 located between the lenses F1 and F3 is located on the enlargement side. A negative meniscus lens (lens L13) having a convex surface, and the lens F3 located closest to the enlargement side is a negative lens (lens L14). The lens F3 is also a double-sided aspheric lens formed of resin, and has a concave shape on the reduction side in the vicinity of the optical axis. The lenses F1 to F3 are moved by the actuator AC in the direction A1 along the optical axis OA when focusing at the time of zooming. Here, it is assumed that the lenses F1 and F2 can move together, and the lens F3 can move independently of the lenses F1 and F2. That is, the lenses F1 to F3 are divided into at least two lens groups (a lens group including the lenses F1 and F2 and a lens group including the lens F3), and each lens group is movable independently of each other. This makes it possible to create a primary image that can finally obtain a good image even in a wide zoom range. In addition, about the method of moving the lenses F1-F3 by the actuator AC, various modes are possible depending on the focus mode at the time of zooming. For example, the lenses F1 to F3 may be moved completely independently, or may be moved in conjunction with each other using a cam mechanism or the like.

  Hereinafter, the lenses constituting each lens group will be described in order from the reduction side. The lens group E1 includes lenses L1 to L9, and the lens group E2 includes lenses L10 and L11. The lens F1 is composed of a lens L12, the lens F2 is composed of a lens L13, and the lens F3 is composed of a lens L14. That is, the first optical group 40a is composed of 14 lenses L1 to L14 as a whole.

  Each of the lenses L2, L4, L6, and L7 is a positive lens, and each of the lenses L3, L5, and L8 is a negative lens. The lens L2 and the lens L3 are first cemented lenses, and the lens L4 and the lens L5 are second cemented lenses. The lens L6 has a convex aspherical surface. The lens L7 and the lens L8 are cemented lenses. The first-first lens group 41 includes at least two (three in this case) cemented lenses including a positive lens and a negative lens provided on the reduction side of the aperture stop ST, and at least one convex aspheric surface. And a positive lens. Each of the lenses L1 to L9 is a glass lens and has a circular shape that is symmetric about the optical axis OA. All of the lenses other than the lens L6 are spherical lenses.

  The lens L10, which is a negative meniscus lens, and the lens L11, which is a biconvex positive lens, are cemented lenses. In other words, the lens group E2 can be said to be a lens group having a positive power including at least one positive lens (lens L11). In this case, by adjusting the state of the light bundle in the first-first lens group 41 that takes in the light bundle emitted from the object side, that is, the panel surface PI and sends it to the first-second lens group, a wide zooming range. In the first-second lens group 42, an appropriate primary image (intermediate image) can be formed. The lenses L10 and L11 are glass spherical lenses and have a circular shape that is symmetric about the optical axis OA.

  As described above, the first-first lens group 41 includes 11 lenses L1 to L11 as a whole. The projection optical system 40 according to the present embodiment can reduce chromatic aberration with a relatively small number of lenses. Furthermore, the numerical aperture can be increased. In addition, the influence of variations during assembly is small. Further, since the aspheric positive lens (L6) made of glass is provided on the reduction side (lens group E1) of the aperture stop ST, the first-second lens group 42 is simply configured by three lenses F1 to F3. Even if it is a thing, it becomes possible to obtain an image with little flare and high contrast. Further, the total lens length can be shortened by suppressing the number of constituent lenses.

  The lens L12 is a positive lens having a convex surface at least on the reduction side. The lens L12 not only plays a role of converting the light beam emitted from the first-first lens group 41 as divergent light into a state close to parallel light and guiding it to the lens L13, but also corrects aberrations by the lens L13 and the lens L14 during focusing. Has the role of facilitating When the reduction-side surface of the lens L12 is a flat surface or a concave surface, since the aberration correction effect on the reduction-side surface is small, it is difficult to correct the aberration by the lenses L13 and L14. Therefore, the F1 lens is preferably a positive lens having a convex surface on the reduction side. The lens L12 is a glass spherical lens and has a circular shape that is symmetric about the optical axis OA.

  The lens L13 is a negative meniscus lens having a convex surface on the enlargement side. The lens L13 cooperates with the lens L12 to create a good primary image during focusing. Since the lens L13 has a concave diverging surface on the reduction side, it is possible to correct the aberration at the time of focusing with the lens L12 in a balanced manner. In addition, since the lens L13 has a convex condensing surface on the enlargement side, the divergence of the light incident on the lens L14 can be suppressed, and the influence of variations of the lens L14 having a strong aspheric surface is reduced. It becomes possible. The lens L13 is a glass spherical lens and has a circular shape that is symmetric about the optical axis OA.

  As described above, the lens L14 is a double-sided aspheric lens having negative power in the vicinity of the optical axis OA, and is molded of resin. Since the lens L14, that is, the lens F3 is an aspherical lens having a concave surface on the reduction side, the lens L13, that is, the lens F2, can be easily formed into a negative meniscus lens shape having a convex surface on the enlargement side. The lens L14 may have a circular shape that is axisymmetric with respect to the optical axis OA, or may be a non-circular shape. For example, it may have a shape in which a part of the upper side (the side on which the image light is projected) that is axisymmetric about the optical axis OA is notched.

  As described above, the second optical group 40b includes the mirror MR having a concave aspherical shape. The mirror MR reflects the image light emitted from the first optical group 40a toward the screen.

  As described above, each of the lenses L1 to L14 constituting the first optical group 40a has a circular shape that is axially symmetric about the optical axis OA, or at least the lens L14 is a circularly symmetrical circle about the optical axis OA. The shape is cut out of a part of the shape. Further, the mirror MR constituting the second optical group 40b also has a shape obtained by cutting out a part of an axially symmetric shape with respect to the optical axis OA. That is, each of the lenses L1 to L14 and the reflecting surface of the mirror MR is a rotationally symmetric system. Further, as shown in the figure, in the projection optical system 40, the reduction side is substantially telecentric. As a result, for example, as described above, when the light modulated by the liquid crystal panels 18R, 18G, and 18B is combined into image light in the cross dichroic prism 19, the assembly variation can be easily absorbed. .

  In the proximity projection optical system, the distance to the screen is generally very close. In the projection optical system 40, the image formed on the panel surface PI of the liquid crystal panel 18G (18R, 18B) is temporarily formed by the first optical group 40a before the mirror of the second optical group 40b, and then the second optical Proximity projection is performed by re-imaging the image on the screen by the group 40b. That is, the first optical group 40a creates a primary image (intermediate image) before the mirror MR. In the close-up projection optical system as described above, since the aberration fluctuation at the time of zooming is relatively large, there is a possibility that the zooming range cannot be made very large. Therefore, the primary image formed by the first optical group 40a is preferably optimized so that a good image can be obtained even when the projection magnification is changed. Further, in a general proximity projection optical system, contrast reduction due to field curvature and astigmatism variation is large. In addition, a change in distortion during zooming tends to be larger than that in a normal lens system.

  However, in the projection optical system 40 of the present embodiment, as described above, the first-second lens group 42 as the focus lens group is configured by three lenses (one positive lens and two negative lenses). In addition, the aspherical lens has a simple configuration of only one of the most negative lens (lens L14) on the enlargement side, but the first-second lens group 42 is movable along the optical axis OA. A desired zooming range can be covered. Furthermore, the projection optical system can be made compact and the cost can be reduced. More specifically, the three lenses constituting the first-second lens group 42 are divided into at least two lens groups in order to form a good image in a wide zooming range during focusing accompanying zooming. The at least two lens groups can be moved individually. The first-second lens group 42 is a positive lens (lens F1, ie, lens L12) disposed on the reduction side, and the angle of the divergent light beam from the first-first lens group 41 is relaxed so that the next negative lens The lens F2 is incident on the lens F2 (ie, the lens L13) and relayed without deteriorating the well-corrected aberration, and the negative lens (lens F3, that is, the lens L14) disposed on the enlargement side is further diverged. By forming an image, a necessary primary image (intermediate image) is formed.

  In the present embodiment, in the 1-1st lens group 41 constituting the fixed group that does not move during focusing, for example, an aspheric surface (lens surface of the lens L6) made of glass is disposed on the reduction side of the aperture stop ST. Thus, aberration variation is reduced even in a wide zoom range without increasing the sensitivity of the resin aspheric lens (lens L14). More specifically, first, as described above, the plurality of lenses L1 to L9 arranged on the reduction side (lens group E1) with respect to the aperture stop ST of the 1-1st lens group 41 has the panel surface PI. Efficiently captures light bundles from Here, when the 1-1st lens group 41 including the lenses L1 to L9 is composed of only spherical lenses, the number of lenses increases. However, in the projection optical system 40, as the number of lenses increases, the transmittance decreases and the total length of the lens increases. Therefore, it is required to minimize the number of lens components. Further, when the first-second lens group 42 is configured with the minimum number of three elements as described above, it is necessary to appropriately control the light beam incident on the first-second lens group 42. On the other hand, in the present embodiment, the first-first lens group 41 includes at least one convex aspherical surface, thereby suppressing flare and providing a high-contrast image. . In the first-first lens group 41, at least on the enlargement side (lens group E2) of the aperture stop ST so that an appropriate intermediate image can be more reliably formed in the first-second lens group 42 in a wide zoom range. Two lenses (L10, L11) are arranged. In addition, in the first-second lens group 42, the lens F3 configured with an aspherical lens having negative power has a second optical group 40b configured with a mirror MR having a concave aspherical shape. Collaborate to correct the final aberration. The second optical group 40b is a reflecting surface on which light beams of respective image heights are separated and incident, and the lens F3 disposed immediately before the second optical group 40b in the first optical group 40a is an aspherical lens. Thus, it is possible to effectively perform the optimum correction for each image height. With the configuration as described above, the number of the first and second lens groups 42 constituting the focus lens group is three, the projection optical system 40 as a whole is about 13 to 14, and the second optical group 40b. Even if it is constituted by a single mirror MR, it is possible to improve the image projected on the screen through the second optical group 40b with less aberration by including an appropriate aberration in the primary image. Can be. In other words, the projector 2 which is a proximity type projector covers a wide zooming range and can cope with a high-resolution image display element.

  Furthermore, with the above-described configuration, the object-side numerical aperture is 0.27 or more, that is, the F number is about 1.5 times or more while having the brightness of about 1.8 (or 1.6). A high zoom range is ensured, and the performance is sufficiently compatible with a high-resolution image display element. As will be described later in Example 3, by appropriately arranging the glass aspheric surfaces, the number of constituent lenses can be suppressed, so that the total lens length can be shortened. Further, as will be described later in Example 4, by appropriately arranging a glass aspheric surface in the vicinity of the aperture stop ST, the numerical aperture is 0.3 or more, that is, the brightness of the F number is about 1.6, and the flare is reduced. It is also possible to obtain an image with a low contrast.

〔Example〕
Hereinafter, specific examples of the projection optical system 40 will be described. The meanings of specifications common to Examples 1 to 4 described below are summarized below.
f Total focal length ω Half angle of view NA Numerical aperture R Curvature radius D Top surface spacing (lens thickness or lens spacing)
Nd d-line refractive index Vd d-line Abbe number

ただし、
ｃ： 曲率（１／Ｒ）
ｈ： 光軸からの高さ
ｋ： 非球面の円錐係数
Ａｉ：非球面の高次非球面係数
なお、ＯＢＪは、パネル面ＰＩを意味し、ＳＴＯは開口絞りＳＴを意味し、ＩＭＧは、スクリーン上の像面（被投射面）を意味する。また、面番号の前に「＊」が記載されている面は、非球面形状を有する面である。 The aspherical surface is specified by the following polynomial (aspherical surface equation).

However,
c: Curvature (1 / R)
h: Height from optical axis k: Aspherical cone coefficient Ai: Aspherical higher-order aspherical coefficient OBJ means panel surface PI, STO means aperture stop ST, IMG means screen It means the upper image surface (projected surface). In addition, a surface having “*” written before the surface number is a surface having an aspherical shape.

Example 1
The lens surface data of Example 1 is shown in Table 1 below.
[Table 1]
f 3.704
ω 73.0 °
NA 0.278

RD Nd Vd
OBJ Infinity 8.700
1 Infinity 26.840 1.51633 64.14
2 Infinity 0.000
3 37.319 6.138 1.61800 63.39
4 -133.798 0.200
5 23.872 6.923 1.49700 81.54
6 -264.396 1.200 1.80518 25.42
7 36.078 0.200
8 22.107 8.505 1.48749 70.24
9 -21.997 1.200 1.83400 37.16
10 21.503 0.100
* 11 15.632 6.259 1.58913 61.15
* 12 -37.637 0.100
13 23.994 7.021 1.76182 26.52
14 -13.000 1.100 1.90366 31.31
15 23.666 1.781
16 -178.477 1.200 1.79952 42.22
17 35.531 2.353
STO Infinity 0.000
19 50.623 1.200 1.83400 37.16
20 26.471 4.758 1.68893 31.07
21 -23.883 Variable interval
22 43.859 7.234 1.48749 70.24
23 8927.895 11.507
24 -31.802 2.000 1.80518 25.42
25 -65.670 Variable spacing
* 26 -37.988 3.080 1.53116 56.04
* 27 79.666 Variable interval
* 28 -56.904 Variable interval
IMG Infinity
In Table 1 and the following table, a power of 10 (for example, 1.00 × 10 ⁺¹⁸ ) is expressed using E (for example, 1.00E + 18).

Table 2 below shows the aspheric coefficients of the lens surfaces of Example 1.
[Table 2]
Aspheric coefficient
K A04 A06 A08 A10
A12 A14
11 -0.3254 -4.0562E-05 -3.8171E-08 1.6672E-09 -5.9264E-12
0.0000E + 00 0.0000E + 00
12 -1.0000 -3.0034E-06 -1.3441E-07 1.1456E-09 -4.6079E-12
0.0000E + 00 0.0000E + 00
26 -8.9406 -4.1419E-06 4.2736E-08 -7.7451E-11 7.8109E-14
-3.2998E-17 0.0000E + 00
27 0.0000 -2.0077E-05 4.1069E-08 -7.3163E-11 9.4882E-14
-6.5519E-17 1.9494E-20
28 -2.0932 -7.0770E-07 9.1586E-11 -3.1672E-14 7.2156E-18
-9.7659E-22 4.7976E-26

Table 3 below shows the values of the variable intervals 21, 25, 27, and 28 in Table 1 at a projection magnification of 125 times, a projection magnification of 101 times, and a projection magnification of 169 times.
[Table 3]
Variable interval
125x 101x 169x
21 24.547 23.760 25.343
25 4.000 4.520 3.409
27 109.855 110.122 109.650
28 -501.000 -408.310 -665.306

  FIG. 4 is a sectional view of the projection optical system 40 of the first embodiment. The projection optical system 40 in FIG. 4 corresponds to the projection optical system 40 in the first embodiment. In FIG. 4, the projection optical system 40 enlarges and projects an image on the panel surface PI at a magnification according to the distance to the screen. The projection optical system 40 includes, in order from the reduction side, lenses L1 to L9 constituting the lens group E1 of the 1-1st lens group 41, lenses L10 and L11 constituting the lens group E2, and a 1-2 lens group 42. 14 lenses L1 to L14, which are a lens L12 constituting the lens F1, a lens L13 constituting the lens F2, and a lens L14 constituting the lens F3. For example, as in the case of changing from the wall surface projection to the floor surface projection, the magnification is changed by changing the projection position (the projection distance is changed). During focusing due to such zooming, the first-first lens group 41 remains fixed, while the lenses F1 to F3 move. Here, the first-second lens group 42 moves the lenses F1 and F2 out of the three lenses F1, F2, and F3 at the time of zooming, and moves the lens F3 independently of the lenses F1 and F2. Focus on.

  The lenses L1 to L14 will be described in detail. The lens L1 as the first lens is a biconvex positive lens, the lens L2 as the second lens is a biconvex positive lens, and is a third lens. A certain lens L3 is a biconcave negative lens, the second lens and the third lens are cemented lenses, and the lens L4 that is the fourth lens is a biconvex positive lens, which is a fifth lens. The lens L5 is a biconcave negative lens, the fourth lens and the fifth lens are cemented lenses, and the sixth lens L6 is a biconvex positive lens with aspheric surfaces on both sides. The lens L7 as the seventh lens is a biconvex positive lens, the lens L8 as the eighth lens is a biconcave negative lens, and the seventh lens and the eighth lens are cemented lenses. The lens L which is the ninth lens Is a biconcave negative lens. The lens L10, which is the tenth lens located after the aperture stop ST, is a biconcave negative lens, and the lens L11, which is the eleventh lens, is biconvex. It is a positive lens, and the tenth lens and the eleventh lens are cemented lenses. The lens L12 as the twelfth lens is a biconvex positive lens (that is, a positive lens having a convex surface on at least the reduction side), and the lens L13 as the thirteenth lens is a negative meniscus lens having a convex surface on the enlargement side. The lens L14, which is the fourteenth lens, is a biconcave negative lens in which both surfaces are aspheric and near the optical axis. The lens L14 is a lens formed of resin. The second optical group 40b is composed of a single concave aspherical mirror.

  FIG. 5A is a reduction side aberration diagram (spherical aberration, astigmatism, distortion) of the projection optical system when the projection magnification is 125 times, and FIG. 5B is a diagram when the projection magnification is 100 times. FIG. 5C is a reduction aberration diagram of the projection optical system, and FIG. 5C is a reduction aberration diagram of the projection optical system when the projection magnification is 169 times. 6 (A) to 6 (E) are lateral aberration diagrams of the projection optical system corresponding to FIG. 5 (A). FIGS. 6A to 6E show lateral aberrations at image heights of 100%, 80%, 60%, 40%, and 15%, respectively. FIG. 6A corresponds to the case of the maximum field angle. Similarly, FIGS. 7A to 7E are lateral aberration diagrams of the projection optical system corresponding to FIG. 5B, and FIGS. 8A to 8E are FIGS. FIG. 6 is a lateral aberration diagram of the projection optical system corresponding to FIG.

(Example 2)
The lens surface data of Example 2 is shown in Table 4 below.
[Table 4]
f 3.716
ω 72.8 °
NA 0.278

RD Nd Vd
OBJ Infinity 8.700
1 Infinity 0.000
2 Infinity 26.840 1.51633 64.14
3 Infinity 0.000
4 43.228 6.423 1.61800 63.39
5 -83.194 0.200
6 23.780 7.928 1.49700 81.54
7 -79.179 1.200 1.84666 23.78
8 46.000 0.200
9 35.223 7.666 1.48749 70.24
10 -22.326 1.200 1.83400 37.16
11 41.000 0.100
* 12 23.142 5.529 1.58913 61.15
* 13 -55.168 0.100
14 33.722 8.100 1.76182 26.52
15 -13.000 1.100 1.90366 31.31
16 33.721 4.731
17 -141.896 2.000 1.84666 23.78
18 -35.107 0.000
STO Infinity 8.500
20 591.882 1.200 1.83400 37.16
21 24.868 4.119 1.68893 31.07
22 -81.476 Variable spacing
23 49.060 7.814 1.48749 70.24
24 -200.026 Variable interval
25 -35.027 2.000 1.80518 25.42
26 -83.099 Variable interval
* 27 -33.918 3.080 1.53116 56.04
* 28 80.282 100.297
* 29 -57.462 Variable interval
IMG Infinity

Table 5 below shows aspheric coefficients of the lens surfaces of Example 2.
[Table 5]
Aspheric coefficient
K A04 A06 A08 A10
A12 A14
12 1.4552 -3.7373E-05 5.0779E-09 5.0980E-10 -9.2415E-13
0.0000E + 00 0.0000E + 00
13 -1.0000 -5.4149E-07 -4.3725E-08 6.8720E-10 -1.8348E-12
0.0000E + 00 0.0000E + 00
27 -7.2727 -3.3388E-06 4.6930E-08 -8.5733E-11 7.7697E-14
-2.6557E-17 0.0000E + 00
28 0.0000 -1.4420E-05 2.8803E-08 -4.6804E-11 5.9059E-14
-4.8230E-17 2.1287E-20
29 -1.4486 -4.1373E-07 5.1283E-11 -3.4557E-14 8.4223E-18
-1.0922E-21 4.5356E-26

Table 6 below shows the values of the variable intervals 22, 24, 26, and 29 in Table 4 at a projection magnification of 125 times, a projection magnification of 101 times, and a projection magnification of 169 times.
[Table 6]
Variable interval
125x 101x 169x
22 22.901 22.108 23.764
24 7.775 7.606 7.946
26 12.297 13.260 11.264
29 -501.000 -409.553 -663.904

  FIG. 9 is a sectional view of the projection optical system 40 of the second embodiment. In Example 2, the first optical group 40a is composed of 14 lenses from the lens L1 (first lens) to the lens L14 (14th lens) counted from the reduction side, and the first optical group 40a is the most. A first lens group 41 having positive power on the reduction side and a negative power weaker than that of the first lens group 41 on the enlargement side, with a wide air space BD as a boundary. -2 lens group 42. The second optical group 40b is composed of a single concave aspherical mirror MR. Although the lens L12, the mirror MR, and the like are drawn as they are without being cut out in FIG. 9, in an actual optical system, at least the mirror MR has a shape partially cut out from a circular shape, and other optical systems are also circular. The shape may be partially cut out.

  In FIG. 9, the projection optical system 40 enlarges and projects an image on the panel surface PI at a magnification according to the distance to the screen. That is, in order from the reduction side, the lenses L1 to L9 constituting the lens group E1 of the 1-1st lens group 41, the lenses L10 and L11 constituting the lens group E2, and the lens F1 of the 1-2nd lens group 42 are arranged. It has 14 lenses L1 to L14, which are a lens L12 constituting the lens, a lens L13 constituting the lens F2, and a lens L14 constituting the lens F3. For example, as in the case of changing from the wall surface projection to the floor surface projection, the magnification is changed by changing the projection position (the projection distance is changed). During focusing at the time of zooming, the lens F3 among the lenses F1 to F3 constituting the 1-1st lens group 41 and the 1-2nd lens group 42 remains fixed, while the lenses F1, F2 Each move. That is, the first-second lens group 42 performs focusing by moving the two lenses F1, F2 out of the three lenses F1, F2, F3 independently during zooming.

  The lenses L1 to L14 will be described in detail. The lens L1 as the first lens is a biconvex positive lens, the lens L2 as the second lens is a biconvex positive lens, and is a third lens. A certain lens L3 is a biconcave negative lens, the second lens and the third lens are cemented lenses, and the lens L4 that is the fourth lens is a biconvex positive lens, which is a fifth lens. The lens L5 is a biconcave negative lens, the fourth lens and the fifth lens are cemented lenses, and the sixth lens L6 is a biconvex positive lens with aspheric surfaces on both sides. The lens L7 as the seventh lens is a biconvex positive lens, the lens L8 as the eighth lens is a biconcave negative lens, and the seventh lens and the eighth lens are cemented lenses. The lens L which is the ninth lens Is a positive meniscus lens having a convex surface on the magnifying side, and a lens L10, which is a tenth lens located at the rear stage of the aperture stop ST, is a negative meniscus lens having a convex surface on the reduction side, and is an eleventh lens. The lens L11 is a biconvex positive lens, and the tenth lens and the eleventh lens are cemented lenses. The lens L12 as the twelfth lens is a biconvex positive lens (that is, a positive lens having a convex surface on at least the reduction side), and the lens L13 as the thirteenth lens is a negative meniscus having a convex surface on the magnification side. The lens L14, which is a fourteenth lens, is a negative lens that is aspherical on both sides and has a biconcave shape near the optical axis. Among these, the lens L14 is a lens formed of resin. As described above, the second optical group 40b is composed of a single concave aspherical mirror.

  FIG. 10A is a reduction aberration diagram (spherical aberration, astigmatism, distortion) of the projection optical system when the projection magnification is 125 times, and FIG. 10B is a diagram when the projection magnification is 100 times. FIG. 10C is a reduction side aberration diagram of the projection optical system, and FIG. 10C is a reduction side aberration diagram of the projection optical system when the projection magnification is 169 times. FIGS. 11A to 11E are lateral aberration diagrams of the projection optical system corresponding to FIG. FIGS. 11A to 11E show lateral aberrations at image heights of 100%, 80%, 60%, 40%, and 15%, respectively. FIG. 11A corresponds to the case of the maximum field angle. Similarly, FIGS. 12 (A) to 12 (E) are lateral aberration diagrams of the projection optical system corresponding to FIG. 10 (B), and FIGS. 13 (A) to 13 (E) are FIGS. FIG. 6 is a lateral aberration diagram of the projection optical system corresponding to FIG.

(Example 3)
The lens surface data of Example 3 is shown in Table 7 below. In particular, in this embodiment, since the negative lens (lenses L6 and L9) having an aspheric surface on at least one surface is arranged in the 1-1st lens group 41, the increase in the number of lenses is reduced and the size of the apparatus is reduced. We are trying to make it.
[Table 7]
f 3.741
ω 72.7 °
NA 0.278

RD Nd Vd
OBJ Infinity 8.700
1 Infinity 26.840 1.51633 64.14
2 Infinity 0.000
3 47.695 7.461 1.61800 63.39
4 -59.921 0.200
5 25.323 7.957 1.49700 81.54
6 -99.197 1.200 1.80518 25.42
7 33.769 0.200
8 18.826 10.100 1.48749 70.24
9 -20.890 1.200 1.83400 37.16
10 28.304 0.200
* 11 15.298 4.464 1.51633 64.06
* 12 32.543 1.036
13 21.116 7.957 1.76182 26.52
14 -13.000 1.100 1.90366 31.31
15 -91.275 0.200
* 16 95.123 1.400 1.79952 42.22
* 17 33.002 1.325
STO Infinity 11.700
19 228.052 2.200 1.68893 31.07
20 -120.975 Variable spacing
21 41.911 7.308 1.59522 67.73
22 389.552 Variable spacing
23 -32.143 2.000 1.80518 25.42
24 -50.558 Variable interval
* 25 -43.069 3.080 1.53116 56.04
* 26 53.557 Variable interval
* 27 -51.941 Variable interval
IMG Infinity

Table 8 below shows the aspheric coefficients of the lens surfaces of Example 3.
[Table 8]
Aspheric coefficient
K A04 A06 A08 A10
A12 A14
11 0.3636 -6.0523E-05 -2.0810E-07 3.7326E-10 1.7724E-12
0.0000E + 00 0.0000E + 00
12 -1.0000 -1.5597E-05 -6.3727E-07 6.7222E-10 1.0035E-11
0.0000E + 00 0.0000E + 00
16 0.0000 4.3352E-05 -2.9757E-06 1.8550E-08 0.0000E + 00
0.0000E + 00 0.0000E + 00
17 0.0000 9.9190E-05 -2.7153E-06 1.9674E-08 0.0000E + 00
0.0000E + 00 0.0000E + 00
25 -12.4724 -1.0026E-06 4.3380E-08 -8.0926E-11 8.2590E-14
-3.2998E-17 0.0000E + 00
26 0.0000 -1.5565E-05 3.1830E-08 -4.2046E-11 4.6170E-14
-3.2438E-17 1.9494E-20
27 -1.77476 -6.65E-07 6.02E-11 -2.82E-14 6.36E-18
-9.52E-22 4.80E-26

Table 9 below shows the values of the variable intervals 20, 22, 24, 26, and 27 in Table 7 at a projection magnification of 125 times, a projection magnification of 101 times, and a projection magnification of 169 times.
[Table 9]
Variable interval
125x 101x 169x
20 18.449 17.497 19.543
22 8.753 8.232 9.325
24 6.887 8.206 5.404
26 98.083 98.236 97.901
27 -501.000 -406.898 -669.193

  FIG. 14 is a sectional view of the projection optical system 40 of the third embodiment. In Example 3, the first optical group 40a is composed of 13 lenses from the lens L1 (first lens) to the lens L13 (13th lens) counted from the reduction side, and the first optical group 40a is the most. A first lens group 41 having positive power on the reduction side and a negative power weaker than that of the first lens group 41 on the enlargement side, with a wide air space BD as a boundary. -2 lens group 42. The second optical group 40b is composed of a single concave aspherical mirror MR. Although the lens L13, the mirror MR, and the like are drawn as they are without being cut out in FIG. 14, in an actual optical system, at least the mirror MR is cut out from a circular shape, and other optical systems are also circular. The shape may be partially cut out.

  In FIG. 14, the projection optical system 40 enlarges and projects an image on the panel surface PI at a magnification corresponding to the distance to the screen. That is, in order from the reduction side, the lenses L1 to L9 constituting the lens group E1 of the 1-1st lens group 41, the lens L10 constituting the lens group E2, and the lens F1 of the 1-2nd lens group 42 are constituted. The lens L11, the lens L12 that constitutes the lens F2, and the lens L13 that constitutes the lens F3 have 13 lenses L1 to L13. For example, as in the case of changing from the wall surface projection to the floor surface projection, the magnification is changed by changing the projection position (the projection distance is changed). During such zooming, the first-first lens group 41 remains fixed, while the lenses F1 to F3 move. That is, the first-second lens group 42 performs focusing by moving the three lenses F1 to F3 independently of each other during zooming.

  The lenses L1 to L13 will be described in detail. The lens L1 as the first lens is a biconvex positive lens, the lens L2 as the second lens is a biconvex positive lens, and is a third lens. A certain lens L3 is a biconcave negative lens, the second lens and the third lens are cemented lenses, and the lens L4 that is the fourth lens is a biconvex positive lens, which is a fifth lens. The lens L5 is a biconcave negative lens, the fourth lens and the fifth lens are cemented lenses, and the lens L6 as the sixth lens is a positive lens having an aspheric surface on both sides and a convex surface on the reduction side. The lens L7, which is a meniscus lens, is a biconvex positive lens, and the lens L8, which is an eighth lens, is a negative meniscus lens having a convex surface on the enlargement side. Lens is close The lens L9, which is a ninth lens, is a negative meniscus lens having aspherical surfaces on both sides and a convex surface on the enlargement side, and the lens L10, which is a tenth lens positioned after the aperture stop ST, It is a biconvex positive lens. The lens L11 as the eleventh lens is a positive meniscus lens having a convex surface on the reduction side, and the lens L12 as the twelfth lens is a negative meniscus lens having a convex surface on the magnification side, and is a thirteenth lens. A certain lens L13 is a negative lens that is aspherical on both sides and has a biconcave shape near the optical axis. Among these, the lens L14 is a lens formed of resin. As described above, the second optical group 40b is composed of a single concave aspherical mirror.

  In the present embodiment, by including lenses (lenses L6 and L9) including a concave aspherical surface in the 1-1st lens group 41, the number of lenses is suppressed, and the total lens length and the mirror radius of the second optical group 40b are reduced. Is made smaller. Specifically, for example, compared with the first and second embodiments, the number of lenses is reduced by one, and the total lens length is reduced by about -5% and the mirror radius is reduced by about -8%. doing.

  FIG. 15A is a reduction aberration diagram (spherical aberration, astigmatism, distortion) of the projection optical system when the projection magnification is 125 times, and FIG. 15B is a diagram when the projection magnification is 101 times. FIG. 15C is a reduction side aberration diagram of the projection optical system, and FIG. 15C is a reduction side aberration diagram of the projection optical system when the projection magnification is 169 times. FIGS. 16A to 16E are lateral aberration diagrams of the projection optical system corresponding to FIG. 16A to 16E show lateral aberrations at image heights of 100%, 80%, 60%, 40%, and 15%, respectively. FIG. 16A corresponds to the case of the maximum field angle. Similarly, FIGS. 17A to 17E are lateral aberration diagrams of the projection optical system corresponding to FIG. 15B, and FIGS. 18A to 18E are FIGS. FIG. 6 is a lateral aberration diagram of the projection optical system corresponding to FIG.

Example 4
The lens surface data of Example 4 is shown in Table 10 below. In particular, in this embodiment, in the 1-1st lens group 41, a negative lens (lens L9) having an aspheric shape on at least one surface is disposed in the vicinity of the aperture stop ST, that is, the lenses L1 to L13. Among them, the lens closest to the aperture stop ST (lens L9) is a negative lens having an aspheric shape on at least one surface, so that the numerical aperture NA is 0.3 or more (that is, F number is about 1.6). It has become a bright thing.
[Table 10]
f 3.702
ω 72.9 °
NA 0.313

RD Nd Vd
OBJ Infinity 8.700
1 Infinity 26.840 1.51633 64.14
2 Infinity 0.000
3 40.85 7.059 1.61800 63.39
4 -94.234 0.200
5 32.165 7.172 1.49700 81.54
6 -95.69 1.200 1.80518 25.42
7 67.147 0.200
8 23.795 11.500 1.48749 70.24
9 -18.166 1.200 1.83400 37.16
10 391.997 0.100
* 11 29.489 5.020 1.58913 61.15
* 12 -73.538 0.100
13 117.61 6.626 1.76182 26.52
14 -13 1.100 1.90366 31.31
15 37.701 2.393
16 -36.192 1.200 1.80610 40.88
* 17 -129.646 0.500
STO Infinity 2.370
19 64.407 1.200 1.83400 37.16
20 22.576 5.861 1.68893 31.07
21 -25.412 Variable interval
22 55.01 7.500 1.48749 70.24
23 -152.86 12.859
24 -29.36 2.000 1.80518 25.42
25 -53.839 Variable interval
* 26 -33.925 3.080 1.53116 56.04
* 27 91.042 Variable interval
* 28 -56.001 Variable interval
IMG Infinity

Table 11 below shows the aspheric coefficients of the lens surfaces of Example 4.
[Table 11]
Aspheric coefficient
K A04 A06 A08 A10
A12 A14
11 -1.0598 -4.2376E-05 2.8896E-08 5.7752E-10 3.0657E-12
0.0000E + 00 0.0000E + 00
12 -1.0000 -6.3509E-05 4.1609E-08 6.7459E-10 3.0208E-13
0.0000E + 00 0.0000E + 00
17 8.1203 3.5595E-05 -4.1043E-08 -2.7722E-10 0.0000E + 00
0.0000E + 00 0.0000E + 00
26 -6.1895 1.3952E-06 3.0684E-08 -6.2666E-11 7.2508E-14
-3.2444E-17 0.0000E + 00
27 0.0000 -1.7496E-05 3.6163E-08 -6.7128E-11 9.0633E-14
-6.4769E-17 2.3354E-20
28 -2.5709 -9.8518E-07 1.7178E-10 -4.3004E-14 7.5901E-18
-8.8414E-22 4.2007E-26

Table 12 below shows the values of the variable intervals 21, 25, 27, and 28 in Table 10 at a projection magnification of 125 times, a projection magnification of 101 times, and a projection magnification of 169 times.
[Table 12]
Variable interval
125x 101x 169x
21 24.812 24.026 25.590
25 4.000 4.462 3.530
27 115.208 115.533 114.900
28 -501.000 -408.081 -666.083

  FIG. 19 is a sectional view of the projection optical system 40 of the fourth embodiment. In Example 4, the first optical group 40a is composed of 14 lenses from the lens L1 (first lens) to the lens L14 (14th lens) counted from the reduction side, and the first optical group 40a is the most. A first lens group 41 having positive power on the reduction side and a negative power weaker than that of the first lens group 41 on the enlargement side, with a wide air space BD as a boundary. -2 lens group 42. The second optical group 40b is composed of a single concave aspherical mirror MR. In FIG. 19, the lens L12, the mirror MR, and the like are drawn as they are without being cut out, but in an actual optical system, at least the mirror MR is cut from a circular shape, and other optical systems are also circular. The shape may be partially cut out.

  In FIG. 19, the projection optical system 40 enlarges and projects an image on the panel surface PI at a magnification according to the distance to the screen. That is, in order from the reduction side, the lenses L1 to L9 constituting the lens group E1 of the 1-1st lens group 41, the lenses L10 and L11 constituting the lens group E2, and the lens F1 of the 1-2nd lens group 42 are arranged. It has 14 lenses L1 to L14, which are a lens L12 constituting the lens, a lens L113 constituting the lens F2, and a lens L14 constituting the lens F3. For example, as in the case of changing from the wall surface projection to the floor surface projection, the magnification is changed by changing the projection position (the projection distance is changed). During such zooming, the first-first lens group 41 remains fixed, while the lenses F1 to F3 move. Here, the first-second lens group 42 performs focusing by moving the lenses F1 and F2 together and moving the lens F3 independently of the lenses F1 and F2 during zooming.

  The lenses L1 to L14 will be described in detail. In the 1-1st lens group 41, the lens L1 as the first lens is a biconvex positive lens, and the lens L2 as the second lens is biconvex. The lens L3 that is the third lens is a biconcave negative lens, the second lens and the third lens are cemented lenses, and the lens L4 that is the fourth lens is biconvex. The lens L5 that is a positive lens and the fifth lens is a biconcave negative lens, the fourth lens and the fifth lens are cemented lenses, and the lens L6 that is the sixth lens has aspheric surfaces on both sides. The lens L7, which is a biconvex positive lens that is applied, is a biconvex positive lens, and the lens L8, which is an eighth lens, is a biconcave negative lens. The lens and the eighth lens are cemented lenses The lens L9, which is the ninth lens, is a negative meniscus lens having a convex surface with an aspheric surface on the enlargement side, and the lens L10, which is the tenth lens located at the rear stage of the aperture stop ST, is convex on the reduction side. The lens L11 as the eleventh lens is a biconvex positive lens, and the tenth lens and the eleventh lens are cemented lenses. In the first-second lens group 42, the lens L12, which is the twelfth lens, is a biconvex positive lens (that is, a positive lens having a convex surface on at least the reduction side), and the lens L13, which is the thirteenth lens, The lens L14, which is a negative meniscus lens having a convex surface on the magnifying side and is the fourteenth lens, is a negative lens that is aspherical on both surfaces and has a biconcave shape near the optical axis. Among these, the lens L14 is a lens formed of resin. As described above, the second optical group 40b is composed of a single concave aspherical mirror.

  In the present embodiment, in the first-first lens group 41, a negative lens (lens L9) including an aspheric shape on at least one surface (enlargement side surface) is disposed in the vicinity of the aperture stop ST. It is possible to satisfactorily correct the curvature of field and astigmatism characteristics in a wide zoom range, and to maintain a stable performance, while the numerical aperture NA is 0.3 or more (that is, F number 1.6). It is bright.

  20A is a reduction aberration diagram (spherical aberration, astigmatism, distortion) of the projection optical system when the projection magnification is 125 times, and FIG. 20B is a diagram when the projection magnification is 100 times. FIG. 20C is a reduction side aberration diagram of the projection optical system, and FIG. 20C is a reduction side aberration diagram of the projection optical system when the projection magnification is 169 times. FIGS. 21A to 21E are lateral aberration diagrams of the projection optical system corresponding to FIG. 21A to 21E show lateral aberrations at image heights of 100%, 80%, 60%, 40%, and 15%, respectively. FIG. 21A corresponds to the case of the maximum field angle. Similarly, FIGS. 22 (A) to 22 (E) are lateral aberration diagrams of the projection optical system corresponding to FIG. 20 (B), and FIGS. 23 (A) to 23 (E) are FIGS. FIG. 6 is a lateral aberration diagram of the projection optical system corresponding to FIG.

(Summary of Examples)
In any of the embodiments, the resin aspherical lens in the first-second lens group 42 which is the focus lens group is a lens F3 (with a half field angle of 70 degrees or more at the wide angle end. The first-second lens group 42 as a whole has a simple configuration constituted by three lenses of positive, negative, and negative lenses F1 to F3. In this case, the mechanism for moving the lenses F1 to F3 can also be made relatively simple. In addition, the entire projection optical system 40 has a small lens configuration with 13 to 14 lenses.

  The present invention is not limited to the above embodiments or examples, and can be implemented in various modes without departing from the scope of the invention.

  For example, in each embodiment, one or more lenses having substantially no power can be added before, after, or between the lenses constituting each lens group.

  The target of enlargement projection by the projection optical system 40 is not limited to a liquid crystal panel, and an image formed by a light modulation element such as a digital micromirror device having a micromirror as a pixel is enlarged and projected by the projection optical system 40. be able to.

  2 ... projector, 11, 12 ... integrator lens, 13 ... polarization conversion element, 14 ... superimposing lens, 15 ... dichroic mirror, 16 ... reflection mirror, 17G, 17R, 17B ... field lens, 18G, 18R, 18B ... liquid crystal panel, DESCRIPTION OF SYMBOLS 19 ... Cross dichroic prism, 21 ... Dichroic mirror, 22 ... Relay lens, 23 ... Reflection mirror, 40 ... Projection optical system, 40a ... 1st optical group, 40b ... 2nd optical group, 41 ... Lens group, 42 ... Lens group 50 ... Optical system part 70 ... Half angle of view 80 ... Circuit device 81 ... Image processing part 81,82,83 ... Circuit part 82 ... Display drive part 83 ... Lens drive part 88 ... Main control part A1 Direction, AC Actuator, BD Air spacing E1, E2 Lens F1 ... lens (F1 lens), F2 ... lens (F2 lens), F3 ... lens (F3 lens), L1-L14 ... lens, MR ... concave aspherical mirror, OA ... optical axis, PI ... panel surface, PR ... prism

Claims (13)

A projection optical system comprising, in order from the reduction side, a first optical group composed of a plurality of lenses and having a positive power, and a second optical group including one reflecting surface having a concave aspherical shape,
The first optical group is fixed at the time of focusing due to zooming with the widest air interval as a boundary, and the first lens group having a positive power and at the time of focusing accompanying zooming The first and second lens units that move and have negative power as a whole,
The first-second lens group includes, in order from the reduction side, an F1 lens including one positive lens having a convex surface on the reduction side, and an F2 lens including one negative meniscus lens having a convex surface on the expansion side. A projection optical system comprising three lenses including an F3 lens composed of one negative lens.   2. The first lens group according to claim 1, wherein the first-first lens group includes a positive lens having an aperture stop inside the first-first lens group and having a convex aspheric surface on the reduction side of the aperture stop. The projection optical system described.   The 1-1st lens group includes an aperture stop inside the 1-1st lens group, and a lens group having a positive power including at least one positive lens on the enlargement side of the aperture stop. The projection optical system according to claim 1, comprising:   The first-first lens group has an aperture stop inside the first-first lens group. The first lens group includes two positive lenses, a positive lens, and a negative lens closer to the reduction side than the aperture stop. The projection optical system according to claim 1, comprising one cemented lens and a second cemented lens composed of a positive lens and a negative lens.   The 1-1 lens group includes an aperture stop inside the 1-1 lens group, and a negative lens having an aspheric shape on at least one surface is disposed in the vicinity of the aperture stop. Item 4. The projection optical system according to Item 1. The F1 lens, the F2 lens, and the F3 lens are divided into at least two lens groups,
The projection optical system according to any one of claims 1 to 5, wherein the at least two lens groups move respectively during focusing accompanying zooming.   The projection optical system according to any one of claims 1 to 6, wherein the F3 lens is a double-sided aspheric lens made of resin.   The projection optical system according to claim 1, wherein the F3 lens has a concave shape on the reduction side in the vicinity of the optical axis.   The projection optical system according to claim 1, wherein the numerical aperture on the object side is 0.3 or more.   The projection optical system according to claim 1, wherein the reduction side is substantially telecentric.   The projection optical system according to any one of claims 1 to 10, wherein all of the elements constituting the first optical group and the second optical group are rotationally symmetric systems.   The projection optical system according to any one of claims 1 to 11, wherein a zooming range is 1.5 times or more. A light modulation element that modulates light from a light source to form image light;
A projector provided with the projection optical system according to any one of claims 1 to 12 which projects the image light from the light modulation element.

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