WO2023119790A1 - 光学系、画像投写装置および撮像装置 - Google Patents

光学系、画像投写装置および撮像装置 Download PDF

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Publication number
WO2023119790A1
WO2023119790A1 PCT/JP2022/037159 JP2022037159W WO2023119790A1 WO 2023119790 A1 WO2023119790 A1 WO 2023119790A1 JP 2022037159 W JP2022037159 W JP 2022037159W WO 2023119790 A1 WO2023119790 A1 WO 2023119790A1
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Prior art keywords
optical system
prism
optical
conjugate point
reduction
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Ceased
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PCT/JP2022/037159
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English (en)
French (fr)
Japanese (ja)
Inventor
恒夫 内田
聡 葛原
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Panasonic Intellectual Property Management Co Ltd
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Panasonic Intellectual Property Management Co Ltd
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Application filed by Panasonic Intellectual Property Management Co Ltd filed Critical Panasonic Intellectual Property Management Co Ltd
Priority to JP2023569075A priority Critical patent/JPWO2023119790A1/ja
Priority to EP22910516.8A priority patent/EP4455756A4/en
Priority to CN202280084369.8A priority patent/CN118435094A/zh
Publication of WO2023119790A1 publication Critical patent/WO2023119790A1/ja
Priority to US18/679,937 priority patent/US20240319485A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B13/00—Optical objectives specially designed for the purposes specified below
    • G02B13/16—Optical objectives specially designed for the purposes specified below for use in conjunction with image converters or intensifiers, or for use with projectors, e.g. objectives for projection TV
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B13/00—Optical objectives specially designed for the purposes specified below
    • G02B13/18—Optical objectives specially designed for the purposes specified below with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B17/00—Systems with reflecting surfaces, with or without refracting elements
    • G02B17/08—Catadioptric systems
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B17/00—Systems with reflecting surfaces, with or without refracting elements
    • G02B17/08—Catadioptric systems
    • G02B17/0804—Catadioptric systems using two curved mirrors
    • G02B17/0816—Catadioptric systems using two curved mirrors off-axis or unobscured systems in which not all of the mirrors share a common axis of rotational symmetry, e.g. at least one of the mirrors is warped, tilted or decentered with respect to the other elements
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B17/00—Systems with reflecting surfaces, with or without refracting elements
    • G02B17/08—Catadioptric systems
    • G02B17/0836—Catadioptric systems using more than three curved mirrors
    • G02B17/0848—Catadioptric systems using more than three curved mirrors off-axis or unobscured systems in which not all of the mirrors share a common axis of rotational symmetry, e.g. at least one of the mirrors is warped, tilted or decentered with respect to the other elements
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B21/00—Projectors or projection-type viewers; Accessories therefor
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B21/00—Projectors or projection-type viewers; Accessories therefor
    • G03B21/14—Details

Definitions

  • the present disclosure relates to an optical system using prisms.
  • the present disclosure also relates to an image projection device and an imaging device using such an optical system.
  • Patent Documents 1 to 4 disclose a projection optical system comprising a dioptric-reflecting optical element in which a transmission surface and a reflection surface are integrated, and mention that either the transmission surface or the reflection surface may be an aspherical surface. .
  • JP 2019-133061 A Japanese Patent Application Laid-Open No. 2020-020860 JP 2020-024377 A Japanese Patent Application Laid-Open No. 2020-042103
  • the present disclosure provides an optical system that is capable of short-focus, large-screen projection or imaging, and that can be miniaturized.
  • the present disclosure also provides an image projection device and an imaging device using such an imaging optical system.
  • One aspect of the present disclosure relates to an optical system that has a reduction conjugate point on the reduction side and an enlargement conjugate point on the enlargement side, and has an intermediate imaging position inside that is in a conjugate relationship with the reduction conjugate point and the enlargement conjugate point, respectively.
  • the optical system is provided on the magnification side and includes a prism made of a transparent medium, and a sub-optical system provided between the reduction conjugate point and the prism and having a plurality of optical elements and an aperture stop.
  • the prism has a first transmission surface positioned on the reduction side, a second transmission surface positioned on the expansion side, and at least one reflection surface positioned on the optical path between the first transmission surface and the second transmission surface.
  • the aperture stop is positioned between the reduction conjugate point and the intermediate imaging position.
  • the first reflecting surface closest to the first transmitting surface on the optical path in the prism has a concave shape facing the direction in which the light beam incident on the first reflecting surface is reflected.
  • the second transmission surface has a shape with a convex surface facing the enlargement side. Part or all of the intermediate image formed at the intermediate imaging position is positioned inside the medium of the prism.
  • the optical system satisfies the following formula (1).
  • TN average d-line refractive index of the positive lens included in the sub-optical system
  • NI number of intermediate images
  • PN d-line refractive index of the prism.
  • optical system having a reduction conjugate point on the reduction side and an expansion conjugate point on the expansion side, and having an intermediate imaging position inside that is in a conjugate relationship with the reduction conjugate point and the expansion conjugate point, respectively.
  • the optical system is provided on the magnification side and includes a prism made of a transparent medium, and a sub-optical system provided between the reduction conjugate point and the prism and having a plurality of optical elements and an aperture stop.
  • the prism has a first transmission surface positioned on the reduction side, a second transmission surface positioned on the expansion side, and at least one reflection surface positioned on the optical path between the first transmission surface and the second transmission surface.
  • the aperture stop is positioned between the reduction conjugate point and the intermediate imaging position.
  • the first reflecting surface closest to the first transmitting surface on the optical path in the prism has a concave shape facing the direction in which the light beam incident on the first reflecting surface is reflected.
  • the second transmission surface has a shape with a convex surface facing the enlargement side. Part or all of the intermediate image formed at the intermediate imaging position is positioned inside the medium of the prism.
  • the optical system satisfies the following formula (2). PN>1.60 (2) here, PN: d-line refractive index of the prism.
  • An image projection apparatus includes the optical system described above and an image forming element that generates an image to be projected onto a screen via the optical system.
  • An imaging device includes the optical system described above, and an imaging device that receives an optical image formed by the optical system and converts the optical image into an electrical image signal.
  • optical system According to the optical system according to the present disclosure, short-focus and large-screen projection or imaging is possible, and miniaturization of the optical system is achieved.
  • FIG. 1 is an overall configuration diagram of an optical system 1 according to the present embodiment
  • FIG. FIG. 2A is a layout diagram showing an optical system 1 according to a reference example.
  • FIG. 2(B) is an explanatory diagram showing how an image projection apparatus using the optical system 1 according to the reference example is used.
  • FIG. 3A is a Y sectional view showing an optical path through which a principal ray passes in the optical system 1 according to the reference example.
  • FIG. 3B is an X cross-sectional view of the optical system 1 viewed from above.
  • FIG. 4A is an explanatory diagram showing a position FLD1 closest to the optical system and a position FLD2 farthest from the optical system among the enlarged conjugate points in the optical system 1 according to the reference example.
  • FIG. 4B is a lateral aberration diagram of reference rays at positions FLD1 and FLD2 in the optical system 1 according to the reference example.
  • FIG. 4C is a lateral aberration diagram of the reference ray at the intermediate imaging position IM in the optical system 1 according to the reference example.
  • 5A is a layout diagram showing the optical system 1 according to the first embodiment.
  • FIG. 5B is an explanatory diagram showing a usage mode of the image projection apparatus using the optical system 1 according to the first embodiment.
  • 6A is an explanatory diagram showing a position FLD1 closest to the optical system and a position FLD2 farthest from the optical system among the enlarged conjugate points in the optical system 1 according to Example 1;
  • 6B is a lateral aberration diagram of the reference light beam at positions FLD1 and FLD2 in the optical system 1 according to Example 1.
  • FIG. 6C is a lateral aberration diagram of the reference ray at the intermediate imaging position IM in the optical system 1 according to Example 1.
  • FIG. 7A is a layout diagram showing an optical system 1 according to Example 2.
  • FIG. FIG. 7B is an explanatory diagram showing a usage mode of an image projection apparatus using the optical system 1 according to the second embodiment.
  • FIG. 8A is an explanatory diagram showing a position FLD1 closest to the optical system and a position FLD2 farthest from the optical system among the enlarged conjugate points in the optical system 1 according to Example 2;
  • 8B is a lateral aberration diagram of the reference light beam at positions FLD1 and FLD2 in the optical system 1 according to Example 2.
  • FIG. 8C is a lateral aberration diagram of the reference ray at the intermediate imaging position IM in the optical system 1 according to Example 2.
  • FIG. 9A is a layout diagram showing an optical system 1 according to Example 3.
  • FIG. 9B is an explanatory diagram showing how the image projection apparatus using the optical system 1 according to the third embodiment is used.
  • FIG. 10A is an explanatory diagram showing a position FLD1 closest to the optical system and a position FLD2 farthest from the optical system among the enlarged conjugate points in the optical system 1 according to Example 3;
  • 10B is a lateral aberration diagram of the reference light beam at positions FLD1 and FLD2 in the optical system 1 according to Example 3.
  • FIG. 10C is a lateral aberration diagram of the reference ray at the intermediate imaging position IM in the optical system 1 according to Example 3.
  • FIG. FIG. 11A is a layout diagram showing an optical system 1 according to Example 4;
  • FIG. 11B is an explanatory diagram showing how the image projection apparatus using the optical system 1 according to the fourth embodiment is used.
  • FIG. 12A is an explanatory diagram showing a position FLD1 closest to the optical system and a position FLD2 farthest from the optical system among the enlarged conjugate points in the optical system 1 according to Example 4;
  • 12B is a lateral aberration diagram of reference light rays at positions FLD1 and FLD2 in the optical system 1 according to Example 4.
  • FIG. 12C is a lateral aberration diagram of the reference ray at the intermediate imaging position IM in the optical system 1 according to Example 4.
  • FIG. 13A is a layout diagram showing an optical system 1 according to Example 5.
  • FIG. FIG. 13B is an explanatory diagram showing how the image projection apparatus using the optical system 1 according to the fifth embodiment is used.
  • FIG. 14A is a Y sectional view showing an optical path through which a principal ray passes in the optical system 1 according to Example 5.
  • FIG. 14B is an X sectional view of the optical system 1 viewed from above.
  • 15A is an explanatory diagram showing a position FLD1 closest to the optical system and a position FLD2 farthest from the optical system among the enlarged conjugate points in the optical system 1 according to Example 5.
  • FIG. 15B is a lateral aberration diagram of reference light rays at positions FLD1 and FLD2 in the optical system 1 according to Example 5.
  • FIG. 15C is a lateral aberration diagram of the reference ray at the intermediate imaging position IM in the optical system 1 according to Example 5.
  • FIG. 16A is a layout diagram showing an optical system 1 according to Example 6.
  • FIG. FIG. 16B is an explanatory diagram showing how the image projection apparatus using the optical system 1 according to the sixth embodiment is used.
  • FIG. 17A is an explanatory diagram showing a position FLD1 closest to the optical system and a position FLD2 farthest from the optical system among the enlarged conjugate points in the optical system 1 according to Example 6; 17B is a lateral aberration diagram of the reference light beam at positions FLD1 and FLD2 in the optical system 1 according to Example 6.
  • FIG. 17C is a lateral aberration diagram of the reference ray at the intermediate imaging position IM in the optical system 1 according to Example 6.
  • FIG. 18A is a layout diagram showing an optical system 1 according to Example 7.
  • FIG. 18B is an explanatory diagram showing how the image projection apparatus using the optical system 1 according to the seventh embodiment is used.
  • 19A is a layout diagram showing an optical system 1 according to Example 8.
  • FIG. 19B is an explanatory diagram showing a usage mode of an image projection apparatus using the optical system 1 according to the eighteenth embodiment.
  • 20A is a layout diagram showing an optical system 1 according to Example 9.
  • FIG. 20B is an explanatory diagram showing how the image projection apparatus using the optical system 1 according to the ninth embodiment is used.
  • FIG. 21A is a layout diagram showing the optical system 1 according to the tenth embodiment.
  • FIG. 21B is an explanatory diagram showing a usage mode of an image projection apparatus using the optical system 1 according to the tenth embodiment.
  • FIG. 23A is a cross-sectional view in the Y direction showing various examples of the stepped structure of the prism PM according to Examples 1 to 4; 23B is a cross-sectional view in the Y direction showing various examples of the stepped structure of the prism PM according to the fifth embodiment;
  • FIG. 24A to 24G are graphs showing shapes of rectangular regions and concentric circles at reduced conjugate points in Numerical Reference Example and Numerical Examples 1 to 6.
  • 25A to 25G are graphs showing distortion shapes at conjugate points on the enlargement side due to distortion aberration of optical systems according to Numerical Reference Example and Numerical Examples 1 to 6.
  • FIG. 24A to 24G are graphs showing shapes of rectangular regions and concentric circles at reduced conjugate points in Numerical Reference Example and Numerical Examples 1 to 6.
  • 25A to 25G are graphs showing distortion shapes at conjugate points on the enlargement side due to distortion aberration of optical systems according to Numerical Reference Example and Numerical Examples 1 to 6.
  • FIG. 26A is a graph showing the relationship between the refractive index of the prism PM and the optical total length.
  • FIG. 26B is a graph showing the relationship between the formula (1) and the optical total length; Block diagram showing an example of an image projection device according to the present disclosure Block diagram showing an example of an imaging device according to the present disclosure
  • the optical system is a projector (image projection system) that projects onto a screen image light of an original image SA obtained by spatially modulating incident light by an image forming device such as a liquid crystal or a DMD (digital micromirror device) based on an image signal.
  • an image forming device such as a liquid crystal or a DMD (digital micromirror device)
  • an image forming device such as a liquid crystal or a DMD (digital micromirror device)
  • the optical system according to the present disclosure can be used to arrange a screen (not shown) on the extension of the enlargement side, and to enlarge the original image SA on the image forming element arranged on the reduction side and project it on the screen.
  • the projection surface is not limited to the screen.
  • the projection surface includes walls, ceilings, floors, windows, etc. of houses, shops, and vehicles and aircraft used for means of transportation.
  • the optical system according to the present disclosure collects light emitted from an object positioned on an extension line on the enlargement side, and forms an optical image of the object on the imaging surface of the imaging device arranged on the reduction side. is also available.
  • Embodiment 1 An optical system according to Embodiment 1 of the present disclosure will be described below with reference to FIGS. 1 to 26.
  • FIG. 2A is a layout diagram showing an optical system 1 according to a reference example.
  • the optical system 1 has a reduction-side reduction conjugate point positioned on the left side of the drawing and an expansion-side expansion conjugate point positioned on the right side of the drawing.
  • the optical system 1 is provided on the enlargement side, a prism PM formed of a transparent medium, and a sub-optical system provided between the reduction conjugate point and the prism PM and having a plurality of optical elements L1 to L18 and an aperture stop ST. and
  • the image area at the reduced conjugate point is defined as a rectangular area having a longitudinal direction (X direction) and a transverse direction (Y direction), and has an imaging relationship that is optically conjugate with the image area at the enlarged conjugate point. .
  • the ray travels along the normal direction (Z direction) of this rectangular area.
  • This rectangular area has aspect ratios such as 3:2, 4:3, 16:9, 16:10, 256:135, for example, and corresponds to the image display area of the image forming element in the case of an image projection device. However, in the case of an image pickup device, it corresponds to the image pickup area of the image sensor.
  • an intermediate imaging position that is conjugate with the reduction conjugate point and the expansion conjugate point, respectively, is located inside the optical system 1.
  • This intermediate imaging position is shown as the Y-direction intermediate image IMy in FIG. 2A, but the X-direction intermediate image IMx is omitted.
  • the sub-optical system includes an optical element PA and lens elements L1 to L18 in order from the reduction side to the enlargement side.
  • the optical element PA represents an optical element such as a TIR (total internal reflection) prism, a prism for color separation and color synthesis, an optical filter, parallel plate glass, a crystal low-pass filter, an infrared cut filter, and the like.
  • a reduction-side end surface of the optical element PA is set at a reduction conjugate point, where the original image SA is placed (surface 1). For the surface numbers, refer to Numerical Examples to be described later.
  • the optical element PA has two parallel and flat transmission surfaces (surfaces 2 and 3).
  • Lens element L1 has a positive meniscus shape with a convex surface facing the reduction side (surfaces 4 and 5).
  • Lens element L2 has a negative meniscus shape with a convex surface facing the reduction side (surfaces 6 and 7).
  • Lens element L3 has a biconvex shape (surfaces 7, 8).
  • Lens element L4 has a negative meniscus shape with a convex surface facing the magnification side (surfaces 8 and 9).
  • Lens elements L2-L4 are cemented together to form a compound lens.
  • Lens element L5 has a biconvex shape (surfaces 10, 11).
  • Lens element L6 has a biconcave shape (surfaces 11, 12).
  • Lens elements L5 and L6 are cemented together to form a compound lens.
  • Lens element L7 has a negative meniscus shape with a convex surface facing the reduction side (surfaces 13, 14).
  • Lens element L8 has a biconvex shape (surfaces 14, 15).
  • Lens elements L7 and L8 are cemented together to form a compound lens.
  • the aperture stop ST defines the range through which the light beam passes through the optical system 1, and is positioned between the reduction conjugate point and the intermediate imaging position described above.
  • aperture stop ST is located between lens element L8 and lens element L9 (surface 16).
  • the lens element L9 has a biconvex shape (surfaces 17, 18).
  • Lens element L10 has a negative meniscus shape with a convex surface facing the magnification side (surfaces 18, 19).
  • Lens elements L9 and L10 are cemented together to form a compound lens.
  • Lens element L11 has a negative meniscus shape with a convex surface facing the magnification side (surfaces 20, 21).
  • the lens element L12 has a positive meniscus shape with a convex surface facing the magnification side (surfaces 21 and 22).
  • Lens elements L11 and L12 are cemented together to form a compound lens.
  • Lens element L13 has a biconvex shape (surfaces 23, 24).
  • Lens element L14 has a biconvex shape (surfaces 25, 26).
  • Lens element L15 has a biconcave shape (surfaces 27, 28).
  • Lens element L16 has a biconvex shape (surfaces 28, 29).
  • Lens elements L15 and L16 are cemented together to form a compound lens.
  • Lens element L17 has a negative meniscus shape with a convex surface facing the reduction side (surfaces 30, 31).
  • Lens element L18 has a positive meniscus shape with a convex surface facing the magnification side (surfaces 32, 33).
  • the prism PM can be made of a transparent medium such as glass or synthetic resin.
  • the prism PM has a first transmission surface T1 located on the reduction side, a second transmission surface T2 located on the expansion side, and two transmission surfaces located on the optical path between the first transmission surface T1 and the second transmission surface T2. It has a first reflecting surface R1 and a second reflecting surface R2.
  • the first transmission surface T1 has a free-form surface shape with a concave surface facing the reduction side (surface 34).
  • the first reflective surface R1 has a free-form surface shape (surface 35) in which the concave surface faces the direction in which the light rays incident on the first reflective surface R1 are reflected.
  • the second reflecting surface R2 has a planar shape (surface 36).
  • the second transmission surface T2 has a free-form surface shape with a convex surface facing the enlargement side (surface 37).
  • FIG. 2(B) is an explanatory diagram showing how an image projection apparatus using the optical system 1 according to the reference example is used.
  • An image projection apparatus including the optical system 1 is placed horizontally on a support base such as a table or on the floor.
  • a screen SR is placed vertically above the support at a relatively short horizontal distance, eg, 0.7 m.
  • the light emitted from the optical system 1 is projected obliquely forward and upward, realizing short-focus and large-screen projection. Therefore, a space for people to move can be formed in front of the screen SR, and the degree of freedom in installing the image projection apparatus can be increased.
  • FIG. 3(A) is a Y sectional view showing the optical path through which the principal ray passes in the optical system 1 according to the reference example
  • FIG. 3(B) is an X sectional view when the optical system 1 is viewed from above.
  • a chief ray is defined as "the ray that passes through the center of the aperture stop, or the ray that passes through the midpoint from either end of the aperture stop at any cross-section".
  • FIG. 3B shows the principal ray passing through the left end of the original image SA in the X direction and the principal ray passing through the right end of the original image SA in the X direction.
  • Both principal rays pass through the sub-optical system, pass through the transmission surface T1, enter the interior of the prism PM, are then reflected by the reflection surface R1, and enter the area indicated by the dashed circle before reaching the reflection surface R2. cross each other at CRx.
  • FIG. 3A when viewed from the direction perpendicular to the Y cross section, some of the plurality of principal rays passing through the reduction conjugate point are on the optical path between the reflecting surface R1 and the transmitting surface T2.
  • FIG. 3B when viewed from the direction perpendicular to the X cross section, some of the plurality of principal rays passing through the reduction conjugate point pass through the reflecting surface R1.
  • the curvature shape of the free-form surface of the reflecting surface R1 is set so as to intersect with the surface T2 on the optical path.
  • FIG. 4A is an explanatory diagram showing a position FLD1 closest to the optical system and a position FLD2 farthest from the optical system among the enlarged conjugate points in the optical system 1 according to the reference example.
  • FIG. 4B is a lateral aberration diagram of reference rays at positions FLD1 and FLD2 in the optical system 1 according to the reference example.
  • FIG. 4C is a lateral aberration diagram of the reference ray at the intermediate imaging position IM that is conjugate with the reduction conjugate point of the sub-optical system in the optical system 1 according to the reference example. Note that FIG. 4C shows the imaging position in the air.
  • a solid line is a wavelength of 587.5600 nm
  • a dashed line is a wavelength of 656.2700 nm
  • a dashed line is a wavelength of 435.8300 nm.
  • FIG. 5A is a layout diagram showing the optical system 1 according to the first embodiment.
  • FIG. 7A is a layout diagram showing the optical system 1 according to the second embodiment.
  • the intermediate imaging positions that are conjugate with the reduced conjugate point and the enlarged conjugate point are shown as the Y-direction intermediate image IMy in the drawing.
  • the illustration of the X-direction intermediate image IMx is omitted.
  • the optical element PA has two parallel and flat transmission surfaces (surfaces 2 and 3).
  • Lens element L1 has a positive meniscus shape with a convex surface facing the reduction side (surfaces 4 and 5).
  • Lens element L2 has a negative meniscus shape with a convex surface facing the reduction side (surfaces 6 and 7).
  • Lens element L3 has a biconvex shape (surfaces 7, 8).
  • Lens element L4 has a negative meniscus shape with a convex surface facing the magnification side (surfaces 8 and 9).
  • Lens elements L2-L4 are cemented together to form a compound lens.
  • Lens element L5 has a biconvex shape (surfaces 10, 11).
  • Lens element L6 has a biconcave shape (surfaces 11, 12).
  • Lens elements L5 and L6 are cemented together to form a compound lens.
  • Lens element L7 has a negative meniscus shape with a convex surface facing the reduction side (surfaces 13, 14).
  • Lens element L8 has a biconvex shape (surfaces 14, 15).
  • Lens elements L7 and L8 are cemented together to form a compound lens.
  • the aperture stop ST defines the range through which the light beam passes through the optical system 1, and is positioned between the reduction conjugate point and the intermediate imaging position described above.
  • aperture stop ST is located between lens element L8 and lens element L9 (surface 16).
  • the lens element L9 has a biconvex shape (surfaces 17, 18).
  • Lens element L10 has a negative meniscus shape with a convex surface facing the magnification side (surfaces 18, 19).
  • Lens elements L9 and L10 are cemented together to form a compound lens.
  • Lens element L11 has a negative meniscus shape with a convex surface facing the magnification side (surfaces 20, 21).
  • the lens element L12 has a positive meniscus shape with a convex surface facing the magnification side (surfaces 21 and 22).
  • Lens elements L11 and L12 are cemented together to form a compound lens.
  • Lens element L13 has a biconvex shape (surfaces 23, 24).
  • Lens element L14 has a biconvex shape (surfaces 25, 26).
  • Lens element L15 has a biconcave shape (surfaces 27, 28).
  • Lens element L16 has a biconvex shape (surfaces 28, 29).
  • Lens elements L15 and L16 are cemented together to form a compound lens.
  • Lens element L17 has a negative meniscus shape with a convex surface facing the reduction side (surfaces 30, 31).
  • Lens element L18 has a positive meniscus shape with a convex surface facing the magnification side (surfaces 32, 33).
  • the prism PM can be made of a transparent medium such as glass or synthetic resin.
  • the prism PM has a first transmission surface T1 located on the reduction side, a second transmission surface T2 located on the expansion side, and two transmission surfaces located on the optical path between the first transmission surface T1 and the second transmission surface T2. It has a first reflecting surface R1 and a second reflecting surface R2.
  • the first transmission surface T1 has a free-form surface shape with a concave surface facing the reduction side (surface 34).
  • the first reflective surface R1 has a free-form surface shape (surface 35) in which the concave surface faces the direction in which the light rays incident on the first reflective surface R1 are reflected.
  • the second reflecting surface R2 has a planar shape (surface 36).
  • the second transmission surface T2 has a free-form surface shape with a convex surface facing the enlargement side (surface 37).
  • the prism PM integrates the first transmitting surface T1, the second transmitting surface T2, the first reflecting surface R1, and the second reflecting surface R2, it is possible to reduce assembly adjustment between optical components and reduce the number of optical components. can reduce costs from
  • the optical surfaces having the power of the prism PM for example, the first transmitting surface T1, the second transmitting surface T2, and the first reflecting surface R1, do not have a rotationally symmetrical axis. It is formed as a free curved surface of curvature.
  • the degree of freedom for satisfactorily correcting distortion is increased, and an effect of shortening the total length of the first sub-optical system can be expected.
  • the weight of the head portion of the optical system 1 can be reduced, the center of gravity of the optical system can be arranged in a well-balanced manner, and the structure of the connecting portion for holding the lens barrel of the optical system to the casing of the optical system can be simplified. .
  • FIG. 5(B) is an explanatory diagram showing how the image projection apparatus using the optical system 1 according to the first embodiment is used.
  • FIG. 7B is an explanatory diagram showing how an image projection apparatus using the optical system 1 according to the second embodiment is used.
  • An image projection apparatus including the optical system 1 is placed horizontally on a support base such as a table or on the floor.
  • a screen SR is placed vertically above the support at a relatively short horizontal distance, eg, 0.7 m.
  • the light emitted from the optical system 1 is projected obliquely forward and upward, realizing short-focus and large-screen projection. Therefore, a space for people to move can be formed in front of the screen SR, and the degree of freedom in installing the image projection apparatus can be increased.
  • FIGS. 6(A) and 8(A) are explanations showing a position FLD1 closest to the optical system and a position FLD2 farthest from the optical system among the enlarged conjugate points in the optical system 1 according to Examples 1 and 2. It is a diagram.
  • FIGS. 6B and 8B are lateral aberration diagrams of reference rays at positions FLD1 and FLD2 in the optical system 1 according to Examples 1 and 2.
  • FIG. 6C and 8C are lateral aberration diagrams of the reference ray at the intermediate imaging position IM conjugate with the reduction conjugate point of the sub-optical system in the optical system 1 according to Examples 1 and 2.
  • FIG. 6(C) and 8(C) show image formation positions in the air.
  • a solid line is a wavelength of 587.5600 nm
  • a dashed line is a wavelength of 656.2700 nm
  • a dashed line is a wavelength of 435.8300 nm.
  • FIG. 9A is a layout diagram showing an optical system 1 according to Example 3.
  • FIG. This optical system 1 has a configuration similar to that of the reference example and the first and second examples, but hereinafter, the explanation overlapping with the reference example and the first and second examples may be omitted.
  • the intermediate imaging positions that are conjugate with the reduced conjugate point and the enlarged conjugate point are shown as the Y-direction intermediate image IMy in the drawing.
  • the illustration of the X-direction intermediate image IMx is omitted.
  • the optical element PA has two parallel and flat transmission surfaces (surfaces 2 and 3).
  • Lens element L1 has a positive meniscus shape with a convex surface facing the reduction side (surfaces 4 and 5).
  • Lens element L2 has a negative meniscus shape with a convex surface facing the reduction side (surfaces 6 and 7).
  • Lens element L3 has a biconvex shape (surfaces 7, 8).
  • Lens element L4 has a negative meniscus shape with a convex surface facing the magnification side (surfaces 8 and 9).
  • Lens elements L2-L4 are cemented together to form a compound lens.
  • Lens element L5 has a biconvex shape (surfaces 10, 11).
  • Lens element L6 has a biconcave shape (surfaces 11, 12).
  • Lens elements L5 and L6 are cemented together to form a compound lens.
  • Lens element L7 has a negative meniscus shape with a convex surface facing the reduction side (surfaces 13, 14).
  • Lens element L8 has a biconvex shape (surfaces 14, 15).
  • Lens elements L7 and L8 are cemented together to form a compound lens.
  • the aperture stop ST defines the range through which the light beam passes through the optical system 1, and is positioned between the reduction conjugate point and the intermediate imaging position described above.
  • aperture stop ST is located between lens element L8 and lens element L9 (surface 16).
  • the lens element L9 has a biconvex shape (surfaces 17, 18).
  • Lens element L10 has a negative meniscus shape with a convex surface facing the magnification side (surfaces 19, 20).
  • the lens element L11 has a positive meniscus shape with a convex surface facing the magnification side (surfaces 20, 21).
  • Lens elements L10 and L11 are cemented together to form a compound lens.
  • Lens element L12 has a biconvex shape (surfaces 22, 23).
  • Lens element L13 has a biconvex shape (surfaces 24, 25).
  • Lens element L14 has a biconcave shape (surfaces 26, 27).
  • Lens element L15 has a biconvex shape (surfaces 27, 28).
  • Lens elements L14 and L15 are cemented together to form a compound lens.
  • Lens element L16 has a negative meniscus shape with a convex surface facing the reduction side (surfaces 29, 30).
  • the lens element L17 has a positive meniscus shape with a convex
  • the prism PM can be made of a transparent medium such as glass or synthetic resin.
  • the prism PM has a first transmission surface T1 located on the reduction side, a second transmission surface T2 located on the expansion side, and two transmission surfaces located on the optical path between the first transmission surface T1 and the second transmission surface T2. It has a first reflecting surface R1 and a second reflecting surface R2.
  • the first transmission surface T1 has a free-form surface shape with a concave surface facing the reduction side (surface 33).
  • the first reflective surface R1 has a free-form surface shape (surface 34) in which the concave surface faces the direction in which the light rays incident on the first reflective surface R1 are reflected.
  • the second reflecting surface R2 has a planar shape (surface 35).
  • the second transmission surface T2 has a free-form surface shape with a convex surface facing the enlargement side (surface 36).
  • FIG. 9(B) is an explanatory diagram showing how an image projection apparatus using the optical system 1 according to the third embodiment is used.
  • An image projection apparatus including the optical system 1 is placed horizontally on a support base such as a table or on the floor.
  • a screen SR is placed vertically above the support at a relatively short horizontal distance, eg, 0.7 m.
  • the light emitted from the optical system 1 is projected obliquely forward and upward, realizing short-focus and large-screen projection. Therefore, a space for people to move can be formed in front of the screen SR, and the degree of freedom in installing the image projection apparatus can be increased.
  • FIG. 10A is an explanatory diagram showing a position FLD1 closest to the optical system and a position FLD2 farthest from the optical system among the enlarged conjugate points in the optical system 1 according to Example 3.
  • FIG. 10B is a lateral aberration diagram of reference rays at positions FLD1 and FLD2 in the optical system 1 according to Example 3.
  • FIG. 10C is a lateral aberration diagram of the reference ray at the intermediate imaging position IM that is conjugate with the reduction conjugate point of the sub-optical system in the optical system 1 according to Example 3.
  • FIG. Note that FIG. 10C shows the imaging position in the air.
  • a solid line is a wavelength of 587.5600 nm
  • a dashed line is a wavelength of 656.2700 nm
  • a dashed line is a wavelength of 435.8300 nm.
  • FIG. 11A is a layout diagram showing an optical system 1 according to Example 4.
  • FIG. This optical system 1 has the same configuration as that of the reference example and Examples 1 to 3, but the description overlapping with the reference example and Examples 1 to 3 may be omitted.
  • the intermediate imaging positions that are conjugate with the reduced conjugate point and the enlarged conjugate point are shown as the Y-direction intermediate image IMy in the drawing.
  • the illustration of the X-direction intermediate image IMx is omitted.
  • the optical element PA has two parallel and flat transmission surfaces (surfaces 2 and 3).
  • Lens element L1 has a positive meniscus shape with a convex surface facing the reduction side (surfaces 4 and 5).
  • Lens element L2 has a negative meniscus shape with a convex surface facing the reduction side (surfaces 6 and 7).
  • Lens element L3 has a biconvex shape (surfaces 7, 8).
  • Lens element L4 has a negative meniscus shape with a convex surface facing the magnification side (surfaces 8 and 9).
  • Lens elements L2-L4 are cemented together to form a compound lens.
  • Lens element L5 has a biconvex shape (surfaces 10, 11).
  • Lens element L6 has a biconcave shape (surfaces 11, 12).
  • Lens elements L5 and L6 are cemented together to form a compound lens.
  • Lens element L7 has a negative meniscus shape with a convex surface facing the reduction side (surfaces 13, 14).
  • Lens element L8 has a biconvex shape (surfaces 14, 15).
  • Lens elements L7 and L8 are cemented together to form a compound lens.
  • the aperture stop ST defines the range through which the light beam passes through the optical system 1, and is positioned between the reduction conjugate point and the intermediate imaging position described above.
  • aperture stop ST is located between lens element L8 and lens element L9 (surface 16).
  • the lens element L9 has a biconvex shape (surfaces 17, 18).
  • Lens element L10 has a negative meniscus shape with a convex surface facing the magnification side (surfaces 19, 20).
  • Lens element L11 has a biconvex shape (surfaces 21, 22).
  • Lens element L12 has a biconvex shape (surfaces 23, 24).
  • Lens element L13 has a biconcave shape (surfaces 25, 26).
  • Lens element L14 has a biconvex shape (surfaces 26, 27).
  • Lens elements L13 and L14 are cemented together to form a compound lens.
  • Lens element L15 has a negative meniscus shape with a convex surface facing the reduction side (surfaces 28, 29).
  • Lens element L16 has a positive meniscus shape with a convex surface facing the magnification side (surfaces 30, 31).
  • the prism PM can be made of a transparent medium such as glass or synthetic resin.
  • the prism PM has a first transmission surface T1 located on the reduction side, a second transmission surface T2 located on the expansion side, and two transmission surfaces located on the optical path between the first transmission surface T1 and the second transmission surface T2. It has a first reflecting surface R1 and a second reflecting surface R2.
  • the first transmission surface T1 has a free-form surface shape with a concave surface facing the reduction side (surface 32).
  • the first reflecting surface R1 has a free-form surface shape (surface 33) with a concave surface facing the direction in which the light rays incident on the first reflecting surface R1 are reflected.
  • the second reflecting surface R2 has a planar shape (surface 34).
  • the second transmission surface T2 has a free-form surface shape with a convex surface facing the enlargement side (surface 35).
  • FIG. 11(B) is an explanatory diagram showing how an image projection apparatus using the optical system 1 according to the fourth embodiment is used.
  • An image projection apparatus including the optical system 1 is placed horizontally on a support base such as a table or on the floor.
  • a screen SR is placed vertically above the support at a relatively short horizontal distance, eg, 0.7 m.
  • the light emitted from the optical system 1 is projected obliquely forward and upward, realizing short-focus and large-screen projection. Therefore, a space for people to move can be formed in front of the screen SR, and the degree of freedom in installing the image projection apparatus can be increased.
  • FIG. 12A is an explanatory diagram showing a position FLD1 closest to the optical system and a position FLD2 farthest from the optical system among the enlarged conjugate points in the optical system 1 according to Example 4.
  • FIG. 12B is a lateral aberration diagram of reference rays at positions FLD1 and FLD2 in the optical system 1 according to Example 4.
  • FIG. 12C is a lateral aberration diagram of the reference ray at the intermediate imaging position IM that is conjugate with the reduction conjugate point of the sub-optical system in the optical system 1 according to Example 4.
  • FIG. Note that FIG. 12C shows the imaging position in the air.
  • a solid line is a wavelength of 587.5600 nm
  • a dashed line is a wavelength of 656.2700 nm
  • a dashed line is a wavelength of 435.8300 nm.
  • FIG. 13A is a layout diagram showing an optical system 1 according to Example 5.
  • FIG. This optical system 1 has the same configuration as that of the reference example and Examples 1 to 4, but the description overlapping with the reference example and Examples 1 to 4 may be omitted.
  • intermediate imaging positions that are conjugate with the reduction conjugate point and the expansion conjugate point, respectively, and are shown as Y-direction intermediate images IMy in the drawing.
  • the illustration of the X-direction intermediate image IMx is omitted.
  • An intermediate image IMy formed at the first intermediate imaging position intersects the lens element L12 of the sub-optical system and is positioned between the lens elements L11 and L13. Part or all of the intermediate image IMy formed at the second intermediate imaging position is positioned inside the medium of the prism PM.
  • the first intermediate image-forming position is not limited to between the lens element L11 and the lens element L12. Further shortening is possible.
  • the number of intermediate imaging positions is the number of conjugate points between the contraction conjugate point and the expansion conjugate point on a specific ray. is the number of intermediate imagings.
  • the optical element PA has two parallel and flat transmission surfaces (surfaces 2 and 3).
  • Lens element L1 has a negative meniscus shape with a convex surface facing the magnification side (surfaces 4, 5).
  • Lens element L2 has a biconvex shape (faces 6, 7).
  • Lens element L3 has a biconvex shape (surfaces 8, 9).
  • Lens element L4 has a biconvex shape (surfaces 10, 11).
  • Lens element L5 has a biconcave shape (surfaces 11, 12). Lens elements L4 and L5 are cemented together to form a compound lens.
  • the aperture stop ST defines the range through which the light beam passes through the optical system 1, and is positioned between the reduction conjugate point and the intermediate imaging position described above, preferably between the second intermediate imaging position. be done.
  • aperture stop ST is located between lens element L5 and lens element L6 (surface 13).
  • Lens element L6 has a biconcave shape (surfaces 14, 15).
  • Lens element L7 has a biconvex shape (surfaces 15, 16).
  • Lens elements L6 and L7 are cemented together to form a compound lens.
  • Lens element L8 has a biconvex shape (surfaces 17, 18).
  • Lens element L9 has a biconvex shape (surfaces 19, 20).
  • Lens element L10 has a negative meniscus shape with a convex surface facing the magnification side (surfaces 21, 22).
  • the lens element L11 has a positive meniscus shape with a convex surface facing the reduction side (surfaces 23, 24).
  • Lens element L12 has a biconcave shape (surfaces 25, 26).
  • Lens element L13 has a biconvex shape (surfaces 27, 28).
  • Lens element L14 has a biconvex shape (surfaces 29, 30).
  • the lens element L15 has a positive meniscus shape with a convex surface facing the magnification side (surfaces 31, 32).
  • Lens element L16 has a negative meniscus shape with a convex surface facing the reduction side (surfaces 33, 34).
  • Lens element L17 has a biconcave shape (surfaces 34, 35). Lens elements L16 and L17 are cemented together to form a compound lens.
  • Lens element L18 has a biconvex shape (surfaces 36, 37).
  • Lens element L19 has a biconcave shape (surfaces 38, 39).
  • Lens element L20 has a biconvex shape (surfaces 40, 41).
  • Lens element L21 has a biconvex shape (surfaces 42, 43).
  • Lens element L22 has a negative meniscus shape with a convex surface facing the magnification side (surfaces 44, 45).
  • Lens element L23 has a biconvex shape (surfaces 46, 47).
  • Lens element L24 has a biconvex shape (surfaces 48, 49).
  • Lens element L25 has a biconcave shape (surfaces 50, 51).
  • the lens element L26 has a positive meniscus shape with a convex surface facing the reduction side (surfaces 52, 53).
  • Lens element L27 has a biconvex shape (surfaces 54, 55).
  • the prism PM has a first transmission surface T1 located on the reduction side, a second transmission surface T2 located on the expansion side, and two transmission surfaces located on the optical path between the first transmission surface T1 and the second transmission surface T2. It has a first reflecting surface R1 and a second reflecting surface R2.
  • the first transmission surface T1 has a free-form surface shape with a concave surface facing the reduction side (surface 56).
  • the first reflective surface R1 has a free-form surface shape (surface 57) with a concave surface facing the direction in which the light rays incident on the first reflective surface R1 are reflected.
  • the second reflecting surface R2 has a planar shape (surface 58).
  • the second transmission surface T2 has a free-form surface shape with a convex surface facing the enlargement side (surface 59).
  • FIG. 13(B) is an explanatory diagram showing how an image projection apparatus using the optical system 1 according to the fifth embodiment is used.
  • An image projection apparatus including the optical system 1 is placed horizontally on a support base such as a table or on the floor.
  • a screen SR is placed horizontally forward at a relatively short horizontal distance, eg, 0.2 m, from the support.
  • the light emitted from the optical system 1 is projected obliquely forward and downward, realizing short-focus and large-screen projection. Therefore, a space for people to move can be formed in front of the screen SR, and the degree of freedom in installing the image projection apparatus can be increased.
  • the screen SR and the image projection device can be arranged substantially parallel, short-focus and large-screen projection can be realized even in a place where the space for arranging the screen SR and the image projection device is narrow.
  • FIG. 14A is a Y sectional view showing the optical path through which the principal ray passes in the optical system 1 according to Example 5, and FIG. 14B is an X sectional view when the optical system 1 is viewed from above. is.
  • Both principal rays pass through the sub-optical system, pass through the transmission surface T1, enter the interior of the prism PM, are then reflected by the reflection surface R1, and enter the area indicated by the dashed circle before reaching the reflection surface R2. cross each other at CRy.
  • FIG. 14(B) shows a principal ray passing through the left end of the original image SA in the X direction and a principal ray passing through the right end of the original image SA in the X direction.
  • Both principal rays pass through the sub-optical system, pass through the transmission surface T1, enter the interior of the prism PM, are then reflected by the reflection surface R1, and enter the area indicated by the dashed circle before reaching the reflection surface R2. cross each other at CRx.
  • FIG. 14A when viewed from the direction perpendicular to the Y cross section, some of the plurality of principal rays passing through the reduction conjugate point are on the optical path between the reflecting surface R1 and the transmitting surface T2.
  • FIG. 14(B) when viewed from the direction perpendicular to the X cross section, some of the plurality of principal rays passing through the reduction conjugate point pass through the reflecting surface R1.
  • the curvature shape of the free-form surface of the reflecting surface R1 is set so as to intersect with the surface T2 on the optical path.
  • FIG. 15(A) is an explanatory diagram showing a position FLD1 closest to the optical system and a position FLD2 farthest from the optical system among the enlarged conjugate points in the optical system 1 according to Example 5.
  • FIG. FIG. 15B is a lateral aberration diagram of reference rays at positions FLD1 and FLD2 in the optical system 1 according to Example 5.
  • FIG. 15C is a lateral aberration diagram of the reference ray at the second intermediate imaging position IM in the optical system 1 according to Example 5.
  • FIG. Note that FIG. 15C shows the imaging position in the air.
  • a solid line is a wavelength of 587.5600 nm
  • a dashed line is a wavelength of 656.2700 nm
  • a dashed line is a wavelength of 435.8300 nm.
  • FIG. 16A is a layout diagram showing an optical system 1 according to Example 6.
  • FIG. This optical system 1 has the same configuration as that of the reference example and Examples 1 to 5, but the description overlapping with the reference example and Examples 1 to 5 may be omitted.
  • the intermediate imaging positions that are conjugate with the reduced conjugate point and the enlarged conjugate point are shown as the Y-direction intermediate image IMy in the drawing.
  • the illustration of the X-direction intermediate image IMx is omitted.
  • Example 6 a portion of the intermediate image IMy is formed between the first transmitting surface T1 and the first reflecting surface R1, and the remaining portion of the intermediate image IMy is formed between the sub-optical system and the prism PM.
  • the optical element PA has two parallel and flat transmission surfaces (surfaces 2 and 3).
  • Lens element L1 has a positive meniscus shape with a convex surface facing the reduction side (surfaces 4 and 5).
  • Lens element L2 has a negative meniscus shape with a convex surface facing the reduction side (surfaces 6 and 7).
  • Lens element L3 has a biconvex shape (surfaces 7, 8).
  • Lens element L4 has a negative meniscus shape with a convex surface facing the magnification side (surfaces 8 and 9).
  • Lens elements L2-L4 are cemented together to form a compound lens.
  • Lens element L5 has a biconcave shape (surfaces 10, 11).
  • Lens element L6 has a biconvex shape (surfaces 11, 12).
  • Lens elements L5 and L6 are cemented together to form a compound lens.
  • the aperture stop ST defines the range through which the light beam passes through the optical system 1, and is positioned between the reduction conjugate point and the intermediate imaging position described above.
  • aperture stop ST is located between lens element L6 and lens element L7 (surface 13).
  • the lens element L7 has a biconvex shape (surfaces 14, 15).
  • Lens element L8 has a negative meniscus shape with a convex surface facing the magnification side (surfaces 16, 17).
  • Lens element L9 has a biconvex shape (surfaces 18, 19).
  • Lens element L10 has a biconvex shape (surfaces 20, 21).
  • Lens element L11 has a biconcave shape (surfaces 21, 22).
  • Lens elements L10 and L11 are cemented together to form a compound lens.
  • Lens element L12 has a negative meniscus shape with a convex surface facing the reduction side (surfaces 23, 24).
  • Lens element L13 has a biconvex shape (surfaces 25, 26).
  • the prism PM can be made of a transparent medium such as glass or synthetic resin.
  • the prism PM has a first transmission surface T1 located on the reduction side, a second transmission surface T2 located on the expansion side, and two transmission surfaces located on the optical path between the first transmission surface T1 and the second transmission surface T2. It has a first reflecting surface R1 and a second reflecting surface R2.
  • the first transmission surface T1 has a free-form surface shape with a concave surface facing the reduction side (surface 27).
  • the first reflecting surface R1 has a free-form surface shape (surface 28) with a concave surface facing the direction in which the light rays incident on the first reflecting surface R1 are reflected.
  • the second reflecting surface R2 has a planar shape (surface 29).
  • the second transmission surface T2 has a free-form surface shape with a convex surface facing the enlargement side (surface 30).
  • FIG. 16(B) is an explanatory diagram showing how an image projection apparatus using the optical system 1 according to Example 6 is used.
  • An image projection apparatus including the optical system 1 is placed horizontally on a support base such as a table or on the floor.
  • a screen SR is placed horizontally forward at a relatively short horizontal distance, eg, 0.2 m, from the support.
  • the light emitted from the optical system 1 is projected obliquely forward and downward, realizing short-focus and large-screen projection. Therefore, a space for people to move can be formed in front of the screen SR, and the degree of freedom in installing the image projection apparatus can be increased.
  • the screen SR and the image projection device can be arranged substantially parallel, short-focus and large-screen projection can be realized even in a place where the space for arranging the screen SR and the image projection device is narrow.
  • FIG. 17A is an explanatory diagram showing a position FLD1 closest to the optical system and a position FLD2 farthest from the optical system among the enlarged conjugate points in the optical system 1 according to Example 6.
  • FIG. 17B is a lateral aberration diagram of reference rays at positions FLD1 and FLD2 in the optical system 1 according to Example 6.
  • FIG. 17C is a lateral aberration diagram of the reference ray at the intermediate imaging position IM that is conjugate with the reduction conjugate point of the sub-optical system in the optical system 1 according to Example 6.
  • FIG. Note that FIG. 17C shows the imaging position in the air.
  • a solid line is a wavelength of 587.5600 nm
  • a dashed line is a wavelength of 656.2700 nm
  • a dashed line is a wavelength of 435.8300 nm.
  • FIG. 18A is a layout diagram showing an optical system 1 according to Example 7.
  • FIG. This optical system 1 has an optical design similar to that of Examples 1 to 4, but a plane mirror MR1 is interposed between the lens elements to bend the reference optical axis A at right angles within the YZ plane.
  • FIG. 18(B) is an explanatory diagram showing how an image projection apparatus using the optical system 1 according to the seventh embodiment is used.
  • An image projection apparatus including the optical system 1 is placed horizontally on a support base such as a table or on the floor.
  • a screen SR is placed parallel to the ZX plane at a relatively short horizontal distance, eg, 0.6 m, from the support.
  • the light emitted from the optical system 1 is projected obliquely to achieve short-focus and large-screen projection.
  • FIG. 19A is a layout diagram showing an optical system 1 according to Example 8.
  • FIG. This optical system 1 has an optical design similar to that of Examples 1 to 4, but a plane mirror MR2 is interposed between the lens elements to bend the reference optical axis A at right angles in the ZX plane.
  • FIG. 19(B) is an explanatory diagram showing how an image projection apparatus using the optical system 1 according to the eighteenth embodiment is used.
  • An image projection apparatus including the optical system 1 is placed horizontally on a support base such as a table or on the floor.
  • a screen SR is placed parallel to the YZ plane at a relatively short horizontal distance, eg, 0.6 m, from the support. The light emitted from the optical system 1 is projected obliquely to achieve short-focus and large-screen projection.
  • FIG. 20A is a layout diagram showing the optical system 1 according to the ninth embodiment.
  • FIG. 21A is a layout diagram showing the optical system 1 according to the tenth embodiment.
  • These optical systems 1 have optical designs similar to those of Examples 1 to 4, but the prism PM has a first transmission surface T1 located on the reduction side, a second transmission surface T2 located on the enlargement side, and a second transmission surface T2 located on the enlargement side. It has one first reflecting surface R1 positioned on the optical path between the first transmitting surface T1 and the second transmitting surface T2.
  • the first transmission surface T1 has a free-form surface shape with a concave surface facing the reduction side.
  • the first reflective surface R1 has a free-form surface shape with a concave surface directed in a direction in which light rays incident on the first reflective surface R1 are reflected.
  • the second transmission surface T2 has a free-form surface shape with a convex surface facing the enlargement side.
  • FIG. 20(B) is an explanatory diagram showing how the image projection apparatus using the optical system 1 according to the ninth embodiment is used.
  • An image projection apparatus including the optical system 1 is placed horizontally on a support base such as a table or on the floor.
  • a screen SR is installed vertically upwards at a relatively short horizontal distance, eg, 0.8 m, rearward from the support.
  • the light emitted from the optical system 1 is projected obliquely upward to the rear, realizing short-focus and large-screen projection.
  • FIG. 21(B) is an explanatory diagram showing how an image projection apparatus using the optical system 1 according to the tenth embodiment is used.
  • An image projection apparatus including the optical system 1 is placed horizontally on a support base such as a table or on the floor.
  • a screen SR is placed vertically upwards at a relatively short horizontal distance, eg, 0.6 m, rearward from the support.
  • the light emitted from the optical system 1 is projected obliquely upward to the rear, realizing short-focus and large-screen projection. Therefore, short-focus and large-screen projection is realized while suppressing the size of the image projection apparatus in the height direction.
  • the sub-optical systems included in Examples 1 to 10 each include three or more convex lenses between the aperture stop and the reduction conjugate point and between the aperture stop and the intermediate imaging position. ing.
  • the image forming element is arranged on the reduction conjugate point side, the light from the image forming element is uniformly guided to the sub optical system.
  • the prism PM by making the enlarged conjugate point side of the sub-optical system a substantially telecentric optical system, the spread of light rays incident on the prism PM is suppressed, and the size of the prism PM is reduced. has the effect of making the
  • the optical element having the power that is arranged closest to the reduction conjugate point in the sub-optical system does not spread the light rays on the reduction conjugate point side, the approximately telecentric effect can be enhanced by arranging a positive lens.
  • the second reflecting surface of the prism PM included in Examples 1 to 8 is not limited to a flat surface, and may be configured by a reflecting surface having a curvature.
  • a reflecting surface having a curvature it is possible to increase the degree of freedom in the direction of the magnified conjugate point and to maintain good shape accuracy of the reflecting surface during processing of the prism PM.
  • the convex surface or the concave surface may be directed in the direction in which light rays enter the second reflecting surface.
  • the optical surface of the second reflecting surface may be a rotationally symmetrical spherical surface, an aspherical surface, or a rotationally asymmetrical free-form surface.
  • Examples 1 to 8 have the second reflecting surface, and the convex surfaces of the first reflecting surface and the second transmitting surface are both arranged toward the enlarged conjugate point side.
  • the luminous flux distribution (footprint) of the optical surface arranged on the enlargement side of the intermediate imaging position in the prism PM is the reference ray OAr imaged at the position closest to the optical system among the enlargement conjugate points on the screen SR.
  • the luminous flux size is distributed so as to be the smallest. This is done by increasing the size of the luminous flux in proportion to the distance between the luminous flux passing through the prism PM and the conjugate point on the enlargement side, matching the imaging magnification of each luminous flux, and maintaining good distortion on the enlargement and reduction sides. can be done.
  • each luminous flux distribution of the optical surface arranged on the enlargement side of the intermediate image forming position in the prism PM into a substantially elliptical shape having a major axis in the azimuth projected onto the XY plane in the direction in which each luminous flux travels.
  • the magnification in the X direction and the Y direction on the enlarged conjugate point side of each luminous flux are matched to obtain the effect of being able to satisfactorily correct the distortion.
  • Prism PM forms a reflecting surface on a part of a lens element or the like having a free-form optical surface, and has at least one reflecting surface located on the optical path between the first transmitting surface and the second transmitting surface.
  • the prism PM forms a reflecting surface on a part of a lens element or the like having a decentered, rotationally symmetrical spherical surface or an aspherical optical surface, and is positioned at least on the optical path between the first transmission surface and the second transmission surface.
  • the prism PM forms a reflecting surface on a part of a lens element or the like having a decentered free-form optical surface, and has at least one reflecting surface positioned on the optical path between the first transmitting surface and the second transmitting surface.
  • the prism PM can also have a configuration in which the coordinate origin of each optical surface is arranged on an extension line of the reference optical axis A, and the same effect as that of the prism PM can be obtained.
  • the prism PM has a positive power because an intermediate image is formed inside and has a conjugate point on the enlargement side of the intermediate image. Also, since the sub-optical system has a reduction-side conjugate point on the reduction side of the intermediate image formed in the prism PM, it has positive power. Since both the prism PM and the sub-optical system have positive power, it is possible to maintain a small size and high optical performance. Furthermore, since the prism PM has a positive power, it becomes possible for some of the plurality of principal rays passing through the reduction conjugate point to intersect on the optical path between the first reflecting surface and the second transmitting surface, A high effect can be expected for distortion correction at the conjugate point on the expansion side or the conjugate point on the reduction side.
  • the optical system according to the present embodiment has a reduction conjugate point CP1 on the reduction side and an enlargement conjugate point CP2 on the enlargement side, and an intermediate imaging position IM having a conjugate relationship with the reduction conjugate point CP1 and the enlargement conjugate point CP2, respectively.
  • An optical system having inside, a prism PM provided on the enlargement side and formed of a transparent medium; a sub optical system OS provided between the reduction conjugate point CP1 and the prism PM and having a plurality of optical elements and an aperture stop ST;
  • the prism PM is positioned on a first transmission surface T1 located on the reduction side, a second transmission surface T2 located on the expansion side, and an optical path between the first transmission surface T1 and the second transmission surface T2.
  • the aperture stop ST is positioned between the reduction conjugate point CP1 and the intermediate imaging position IM;
  • the first reflecting surface R1 closest to the first transmitting surface T1 on the optical path in the prism PM has a concave shape facing the direction in which the light beam incident on the first reflecting surface R1 is reflected,
  • the second transmission surface T2 has a shape with a convex surface facing the enlargement side, part or all of the intermediate image formed at the intermediate imaging position IM is positioned inside the medium of the prism PM;
  • the optical system may satisfy the following formula (1).
  • TN average d-line refractive index of the positive lens included in the sub-optical system
  • NI number of intermediate images
  • PN d-line refractive index of the prism.
  • the optical system may satisfy the following formula (1a). 0.44 ⁇ (TN-((NI-1)/8))/PN 2 ⁇ 0.63 (1a)
  • FIG. 1 is an overall configuration diagram of an optical system 1 according to this embodiment.
  • the optical system 1 includes a sub-optical system OS and a prism PM.
  • the sub-optical system OS has a plurality of optical elements and an aperture stop ST.
  • the sub-optical system OS generally includes a positive lens with positive optical power (indicated by dots in the figure), a negative lens with negative optical power (no dots), and an optical element with zero optical power.
  • Prism PM has a first transmission surface T1, a second transmission surface T2, and at least one reflection surface (for example, two reflection surfaces R1 and R2).
  • the reduction conjugate point CP1 on the reduction side, the expansion conjugate point CP2 on the expansion side, and the intermediate imaging position IM are in a conjugate relationship with each other.
  • an original image SA formed by an image forming device such as a liquid crystal or DMD is provided at the reduced conjugate point CP1
  • a screen SR is provided at the enlarged conjugate point CP2.
  • a solid-state imaging device is provided at the reduction conjugate point CP1, and images an object positioned at the expansion conjugate point CP2.
  • Equation (1) expressing these relationships, while maintaining the optical performance of the optical system,
  • the distance to the expansion conjugate point CP2 can be shortened, the optical total length from the reduction conjugate point CP1 to the prism PM can be reduced, and especially the occurrence of chromatic aberration can be suppressed.
  • the refractive index of the prism PM it is possible to achieve miniaturization of the prism PM. If the upper limit of formula (1) is exceeded, the size of the prism PM for correcting the curvature of field of the intermediate image formed by the sub optical system OS at the intermediate imaging position IM will increase, resulting in an increase in the overall optical length. . Moreover, if the total optical length is maintained, distortion occurs, making it difficult to maintain good optical performance. If the lower limit of formula (1) is not reached, it becomes difficult to correct lateral chromatic aberration, and high optical performance cannot be maintained.
  • the optical system according to the present embodiment has a reduction conjugate point CP1 on the reduction side and an enlargement conjugate point CP2 on the enlargement side, and an intermediate imaging position IM having a conjugate relationship with the reduction conjugate point CP1 and the enlargement conjugate point CP2, respectively.
  • An optical system having inside, a prism PM provided on the enlargement side and formed of a transparent medium; a sub optical system OS provided between the reduction conjugate point CP1 and the prism PM and having a plurality of optical elements and an aperture stop ST;
  • the prism PM is positioned on a first transmission surface T1 located on the reduction side, a second transmission surface T2 located on the expansion side, and an optical path between the first transmission surface T1 and the second transmission surface T2.
  • the aperture stop ST is positioned between the reduction conjugate point CP1 and the intermediate imaging position IM;
  • the first reflecting surface R1 closest to the first transmitting surface T1 on the optical path in the prism PM has a concave shape facing the direction in which the light beam incident on the first reflecting surface R1 is reflected,
  • the second transmission surface T2 has a shape with a convex surface facing the enlargement side, part or all of the intermediate image formed at the intermediate imaging position IM is positioned inside the medium of the prism PM;
  • the optical system may satisfy the following formula (2). PN>1.60 (2)
  • the upper limit of the d-line refractive index PN of the prism is preferably PN ⁇ 2.00 so as not to excessively increase the chromatic dispersion. Further, by setting the upper limit of the d-line refractive index PN of the prism to PN ⁇ 1.90, a further effect of suppressing chromatic dispersion can be expected.
  • the prism PM according to the embodiment of the present disclosure includes a free-form surface that does not have a rotationally symmetrical axis.
  • a similar effect can be obtained when the optical surface is configured with an optical surface having a similar shape.
  • the coordinate origins forming the rotationally symmetrical optical surfaces forming the prism PM may be decentered from each other, or the coordinate origins of the optical surfaces forming the prism PM may be placed on an extension line of the reference optical axis A. You can place it.
  • each optical surface of the prism PM is a rotationally asymmetric free-form surface, or if the coordinate origin forming each optical surface is decentered, a further effect can be obtained.
  • the size of the prism PM is reduced up to a factor of Nd′/(Nd′+ ⁇ Nd) at maximum. expected to be effective.
  • Nd′ the refractive index of the prism PM
  • ⁇ Nd the refractive index of the prism PM
  • a maximum size reduction effect of about 6% can be expected for the prism PM while maintaining the optical performance and the projection distance.
  • the reduced conjugate point CP1 has an imaging relationship in a rectangular area having a longitudinal direction and a lateral direction,
  • a plane including a position where the principal ray passing through the center of the longitudinal direction of the rectangular region is reflected by the first reflecting surface is defined as a Y section, a section perpendicular to the Y section is defined as an X section, and a section perpendicular to the Y section is defined as a plane perpendicular to the Y section.
  • the curvature shape of the first reflecting surface R1 may be set so as to.
  • a plurality of principal rays intersect on the optical path between the reflecting surface R1 of the prism PM and the second transmitting surface T2 for both the Y section and the X section. Therefore, the total optical length can be shortened while keeping the size of the prism PM arranged on the enlargement side including the reflecting surface small. Furthermore, in the wide imaging range of the enlarged conjugate point CP2, good optical performance including distortion can be maintained, and the projection range can be expanded. Also, the distance between the enlarged conjugate point CP2 and the optical system can be shortened.
  • the optical system according to this embodiment may satisfy the following formula (3). 0.05 ⁇ (LP/YI)/((
  • the optical system according to this embodiment may satisfy the following formula (3a). 0.08 ⁇ (LP/YI)/((
  • FIG. 22 is an explanatory diagram showing definitions of various rays between the optical system 1 and the optical surface at the expansion conjugate point.
  • the marginal rays LRa and LRb are defined as rays forming an image at the edge of the expansion conjugate point CP2 closest to the optical system.
  • Equation (3) expressing these relationships, distortion can be reduced in a wide imaging range of the enlarged conjugate point CP2. Good optical performance can be maintained, and the projection range can be expanded. Also, the distance between the enlarged conjugate point CP2 and the optical system can be shortened. If the upper limit of formula (3) is exceeded, the distortion will be excessively corrected, making it difficult to maintain good optical performance. If the lower limit of expression (3) is not reached, distortion and curvature of field will occur, making it difficult to shorten the total optical length, and the imaging range with good optical performance will be narrowed at the expansion conjugate point CP2.
  • the optical system according to this embodiment may satisfy the following formula (4). ⁇ 0.0100 ⁇ Tp/YI ⁇ 0.0020 (4) here, Tp: Petzval sum of the sub optical system OS.
  • optical system according to this embodiment may satisfy the following formula (4a). ⁇ 0.0090 ⁇ Tp/YI ⁇ 0.0030 (4a)
  • Equation (4) expressing these relationships, optical performance including distortion can be achieved in a wide imaging range of the enlarged conjugate point CP2. It can be maintained well, and the projection range can be expanded. Also, the distance between the enlarged conjugate point CP2 and the optical system can be shortened. If the upper limit of formula (4) is exceeded or if the lower limit of formula (4) is not reached, field curvature occurs in the peripheral portion, making it difficult to maintain good optical performance.
  • the Petzval sum Tp is calculated by taking the optical element surface closest to the reduction side of the sub optical system OS as 1, each optical element surface i, and the optical element surface closest to the enlargement side m as the refractive index of the optical element surface i on the reduction side. It is represented by the following formula (Fa), where n i ⁇ 1 is the refractive index on the enlargement side and n i is the refractive index.
  • the optical system according to this embodiment may satisfy the following formula (5). 0.50 ⁇ XMM/YMM ⁇ 1.50 (5) here, XMM: X-direction imaging magnification at the intermediate imaging position IM for the reduced conjugate point CP1 YMM: Y-direction imaging magnification at the intermediate imaging position IM for the reduced conjugate point CP1.
  • the optical system according to this embodiment may satisfy the following formula (5a). 0.65 ⁇ XMM/YMM ⁇ 1.65 (5a)
  • Equation (5) expressing these relationships, optical performance including distortion can be obtained in a wide imaging range of the enlarged conjugate point CP2. It can be maintained well, and the projection range can be expanded. Also, the distance between the enlarged conjugate point CP2 and the optical system can be shortened. If the upper limit of formula (5) is exceeded or if the lower limit of formula (5) is not reached, astigmatism occurs at the expansion conjugate point CP2, making it difficult to maintain good optical performance.
  • XMM and YMM are conditional expressions at an intermediate imaging position in air, they may be converted values in consideration of the refractive index of the prism PM.
  • the optical system according to this embodiment may satisfy the following formula (6). 45 ⁇ Tv ⁇ 65 (6) here, T ⁇ : the average Abbe number of the positive lenses included in the sub optical system OS.
  • the optical system according to this embodiment may satisfy the following formula (6a). 47.5 ⁇ Tv ⁇ 62.5 (6a)
  • the reduction conjugate point CP1 to the expansion conjugate point CP2 can be shortened, the optical total length from the reduction conjugate point CP1 to the prism PM can be reduced, and especially the occurrence of chromatic aberration can be suppressed.
  • the size of the prism PM can be reduced. If the upper limit of formula (6) is exceeded, the occurrence of chromatic aberration can be suppressed, but the total optical length increases. If the lower limit of the formula (6) is not reached, the total optical length can be shortened, but correction of chromatic aberration becomes difficult, and good optical performance cannot be obtained.
  • the optical system according to this embodiment may satisfy the following formula (7). 0.70 ⁇ (PN/TN) ⁇ (Tv/Pv) ⁇ 1.90 (7) here, P ⁇ : Abbe number of the prism PM T ⁇ : Average Abbe number of the positive lenses included in the sub optical system OS.
  • the optical system according to this embodiment may satisfy the following formula (7a). 0.80 ⁇ (PN/TN) ⁇ (Tv/Pv) ⁇ 1.80 (7a)
  • the optical system according to this embodiment may satisfy the following formula (8). 1.55 ⁇ TN ⁇ 1.75 (8)
  • the overall optical length can be reduced while maintaining the optical performance of the optical system, and in particular, the occurrence of chromatic aberration can be suppressed. can. Also, miniaturization of the prism PM can be achieved. If the upper limit of formula (8) is exceeded, the total optical length can be shortened, but it becomes difficult to correct chromatic aberration, and good optical performance cannot be obtained. If the lower limit of expression (8) is not reached, the occurrence of chromatic aberration can be suppressed, but the total optical length becomes long.
  • the optical system according to this embodiment may satisfy the following formula (9). 35 ⁇ Pv ⁇ 65 (9) here, Pv: Abbe number of the prism.
  • the optical system according to this embodiment may satisfy the following formula (9a). 37.5 ⁇ Pv ⁇ 62.5 (9a)
  • the overall optical length can be reduced while maintaining the optical performance of the optical system, and in particular, the occurrence of chromatic aberration can be suppressed. can. Also, miniaturization of the prism PM can be achieved. If the upper limit of formula (9) is exceeded, the occurrence of chromatic aberration can be suppressed, but the total optical length becomes long. If the lower limit of formula (9) is not reached, the total optical length can be shortened, but it becomes difficult to correct chromatic aberration, and good optical performance cannot be obtained.
  • the optical system according to this embodiment may satisfy the following formula (10). 45 ⁇ Tv ⁇ 65 (10) here, T ⁇ : the average Abbe number of the positive lenses included in the sub optical system OS.
  • the optical system according to this embodiment may satisfy the following formula (10a). 47.5 ⁇ Tv ⁇ 62.5 (10a)
  • the overall optical length can be reduced while maintaining the optical performance of the optical system, and in particular, the occurrence of chromatic aberration can be suppressed. can.
  • the size of the prism PM can be reduced. If the upper limit of formula (10) is exceeded, the occurrence of chromatic aberration can be suppressed, but the total optical length increases. If the lower limit of formula (10) is not reached, the total optical length can be shortened, but it becomes difficult to correct chromatic aberration, and good optical performance cannot be obtained.
  • At least one of the first transmission surface T1, the second transmission surface T2, and the at least one reflection surface R1, R2 of the prism PM may include a rotationally asymmetric surface. good.
  • the total optical length can be shortened while keeping the size of the prism PM arranged on the enlargement side including the reflecting surface small. Furthermore, in the wide imaging range of the enlarged conjugate point CP2, good optical performance including distortion can be maintained, and the projection range can be expanded. Also, the distance between the enlarged conjugate point CP2 and the optical system can be shortened.
  • the prism PM may be a prism body integrally molded with a single refractive index material, or may include the prism body and a coating.
  • the intermediate image positioned inside the medium of the prism PM is located between the first transmission surface T1 and the first reflection surface R1 closest to the first transmission surface T1. may be present only.
  • the total optical length can be shortened while keeping the size of the prism PM arranged on the enlargement side including the reflecting surface small. Furthermore, in the wide imaging range of the enlarged conjugate point CP2, good optical performance including distortion can be maintained, and the projection range can be expanded. Also, the distance between the enlarged conjugate point CP2 and the optical system can be shortened.
  • the sub optical system OS includes a plurality of rotationally symmetrical lens elements, When an axis passing through at least two centers of the rotationally symmetrical lens elements is defined as a reference optical axis A, the first transmission surface T1, the second transmission surface T2 and the at least one reflection surfaces R1 and R2 of the prism PM At least one optical surface of the optical surface group consisting of is connected on a concentric circle centered on the intersection of the reference optical axis A and the reduced conjugate point of the rectangular area in a plane perpendicular to the reference optical axis A
  • the maximum angle ⁇ max and the minimum angle ⁇ min of the angles at which the principal ray of rays having an image relation are incident on the optical surface and the normal to the surface may be formed so as to satisfy the following formula (11). 0.014° ⁇
  • the total optical length can be shortened while keeping the size of the prism PM arranged on the enlargement side including the reflecting surface small. Furthermore, in the wide imaging range of the enlargement-side role point CP2, good optical performance including distortion can be maintained, and the projection range can be expanded. Also, the distance between the enlarged conjugate point CP2 and the optical system can be shortened. If the upper limit of formula (11) is exceeded, light rays are incident on the reflecting surface at an acute angle, so that the area of the light beam becomes large and the shape accuracy of the optical surface is greatly affected.
  • the sub optical system OS includes a plurality of rotationally symmetrical lens elements, Assuming that an axis passing through at least two centers of the rotationally symmetrical lens element is a reference optical axis A, a principal ray of light rays is located between the reference optical axis A and the rectangular area in a plane perpendicular to the reference optical axis A.
  • the maximum optical path length difference ⁇ Lmax of the optical path through which the principal ray passes through the interior of the prism PM is given by the following using the radius r of the concentric circles: Equation (12) may be satisfied. 0.001 ⁇ Lmax/r ⁇ 0.100 (12)
  • the total optical length can be shortened while keeping the size of the prism PM arranged on the enlargement side including the reflecting surface small. Furthermore, in the wide imaging range of the enlargement-side role point CP2, good optical performance including distortion can be maintained, and the projection range can be expanded. Also, the distance between the enlarged conjugate point CP2 and the optical system can be shortened. If the upper limit of formula (12) is exceeded, the distortion will be excessively corrected, making it difficult to maintain good optical performance. If the lower limit of formula (12) is exceeded, it becomes impossible to utilize an optical surface having different curvatures in the X direction and the Y direction perpendicular to the reference optical axis A, making it difficult to shorten the total optical length. The good imaging range of the image becomes narrower.
  • the maximum optical path length Lmax of the optical path through which the principal ray passes through the interior of the prism PM may satisfy the following formula (13) using the radius r of the concentric circles. 2 ⁇ Lmax/r ⁇ 30 (13)
  • the total optical length can be shortened while keeping the size of the prism PM arranged on the enlargement side including the reflecting surface small. Furthermore, in the wide imaging range of the enlargement-side role point CP2, good optical performance including distortion can be maintained, and the projection range can be expanded. Also, the distance between the enlarged conjugate point CP2 and the optical system can be shortened. If the upper limit of expression (13) is exceeded, it becomes difficult to miniaturize the optical system arranged on the enlargement side. In particular, when the effective diameter of the second transmission surface T2 is increased, the molding time is lengthened, resulting in an increase in cost. If the lower limit of formula (13) is not reached, it will be difficult to form an optical surface necessary to keep good optical performance including distortion.
  • a flat portion perpendicular to the reference optical axis A may be provided on a part of the outer peripheral portion of the prism PM.
  • FIG. 23(A) is a cross-sectional view in the Y direction showing various examples of the stepped structure of the prism PM according to Examples 1-4.
  • FIG. 23B is a cross-sectional view in the Y direction showing various examples of the stepped structure of the prism PM according to the fifth embodiment.
  • Various lens elements and various prisms that make up the optical system 1 are generally attached inside a lens barrel (not shown) using adhesives, metal fittings, and the like. At that time, a highly accurate mounting structure is required in order to faithfully reproduce the various dimensions of the optical design.
  • a part of the outer periphery of the prism PM is provided with, for example, an end face PMa that serves as a mounting reference.
  • Such an end face PMa can be formed so as to be a plane portion perpendicular to the reference optical axis A.
  • the lens barrel is provided with a plane portion corresponding to the shape of the end face PMa.
  • a protective film made of a dielectric, glass, polymer, or the like may be applied to the second transmission surface T2 of the prism PM according to Examples 1 to 10. With such a configuration, the second transmission surface T2 exposed to the outside can be protected from scratches and stains. Also, in order to protect the second transmission surface T2 of the prism PM, a transparent cover may be provided on the enlarged side of the second transmission surface T2. The transparent cover may be formed with a surface having optical power, or may be formed with a surface having no optical power.
  • the optical system according to the present embodiment has a reduction conjugate point on the reduction side and an enlargement conjugate point on the enlargement side, and has an intermediate imaging position that is conjugate with the reduction conjugate point and the enlargement conjugate point, respectively.
  • the optical system may satisfy the following formula (14). 0.80 ⁇ TN/PN ⁇ 1.01 (14)
  • the optical performance of the optical system is maintained while the expansion conjugate from the reduction conjugate point CP1 to the expansion conjugate
  • the distance to the point CP2 can be shortened, the total optical length from the reduction conjugate point CP1 to the prism PM can be reduced, and especially the occurrence of chromatic aberration can be suppressed.
  • the refractive index of the prism PM it is possible to achieve miniaturization of the prism PM.
  • the size of the prism PM for correcting the curvature of field of the intermediate image formed by the sub optical system OS at the intermediate imaging position IM will increase, resulting in an increase in the overall optical length. Moreover, if the total optical length is maintained, distortion occurs, making it difficult to maintain good optical performance. If the lower limit of formula (14) is not reached, it becomes difficult to correct lateral chromatic aberration, and high optical performance cannot be maintained.
  • the optical system according to this embodiment may satisfy the following formula (14a). 0.83 ⁇ TN/PN ⁇ 1.01 (14a)
  • z amount of sag on the surface parallel to the z-axis
  • c curvature at surface vertex
  • k conic coefficient
  • a to H 4th to 18th order coefficients of r.
  • the free-form surface shape is defined by a local Cartesian coordinate system (x, y, z) whose origin is the vertex of the surface. are defined by the following equations (Fc) and (Fd) using
  • z amount of sag on the surface parallel to the z-axis
  • c curvature at the surface vertex
  • k conic coefficient
  • C j coefficient of the monomial x m y n .
  • i-th order term of x and the j-th order term of y which are free-form surface coefficients in polynomials, are described as x**i*y**j.
  • X**2*Y indicates the free-form surface coefficients of the second-order terms of x and the first-order terms of y in a polynomial.
  • Table 1 shows the lens data
  • Table 2 shows the aspheric surface shape data of the lens
  • Table 3 shows the free curved surface shape data of the prism.
  • Tables 22 to 28 below show corresponding values of each conditional expression (1) to (4) in Numerical Reference Example and Numerical Examples 1 to 6, respectively.
  • the size of the prism can be reduced, and short-focus and large-screen projection or imaging becomes possible.
  • K-PSFn202 21.5
  • P-PSFn214P 24.1
  • FIGS. 24A to 24G are graphs showing the shapes of rectangular regions and concentric circles at reduced conjugate points in Numerical Reference Example and Numerical Examples 1 to 6.
  • FIG. 24A to 24G are graphs showing the shapes of rectangular regions and concentric circles at reduced conjugate points in Numerical Reference Example and Numerical Examples 1 to 6.
  • FIGS. 25A to 25G are graphs showing the distortion shapes at the conjugate points on the enlargement side due to the distortion aberration of the optical systems according to Numerical Reference Example and Numerical Examples 1 to 6.
  • FIG. 26(A) is a graph showing the relationship between the refractive index of the prism PM and the optical total length from the reduction conjugate point to the prism PM in the optical system 1.
  • FIG. 26B is a graph showing the relationship between the formula (1) and the total optical length.
  • the numerical reference example and numerical examples 1 to 4 in which the basic configuration of the optical system 1 is similar, are compared.
  • the optical surfaces forming the prism PM according to the embodiment of the present disclosure are arranged decentered from each other.
  • the coordinate origin of the optical surface forming the first transmission surface is located on the extension line of the reference optical axis A of the first transmission surface T1.
  • the coordinate origin forming each optical surface is not located on the extension line of the reference optical axis A.
  • Each optical surface of the reference example and Examples 1 to 4 and 6 has a coordinate origin on the extension line of the reference optical axis A in the YZ cross section, and the first reflection surface R1 is located below the extended line of the reference optical axis A, and the second reflecting surface R2 and the second transmitting surface T2 are located above the reference optical axis A.
  • each optical surface in Example 5 has a coordinate origin on the extension line of the reference optical axis A, the first reflecting surface R1, the second reflecting surface R2, and the second reflecting surface R2.
  • the transmission surface T2 is positioned below the reference optical axis A.
  • the optical surface of the first transmission surface T1 does not need to position the coordinate origin on the extension line of the reference optical axis A, and may be positioned decentered above or below the reference optical axis A,
  • the coordinate origin of each optical surface may be positioned on an extension line of the reference optical axis A.
  • each optical surface forming the prism PM is formed of a rotationally asymmetric free-form surface, the coordinate origin of each optical surface is decentered, thereby further enhancing the effect of shortening the projection distance and miniaturization.
  • the prism PM according to the embodiment of the present disclosure has a symmetrical shape only with respect to the YZ section.
  • FIG. 27 is a block diagram showing an example of an image projection device according to the present disclosure.
  • the image projection apparatus 100 includes the optical system 1 disclosed in the first embodiment, an image forming element 101, a light source 102, a control section 110, and the like.
  • the image forming element 101 is composed of liquid crystal, DMD, etc., and generates an image to be projected onto the screen SR via the optical system 1 .
  • a light source 102 is composed of an LED (light emitting diode), a laser, or the like, and supplies light to the image forming element 101 .
  • the control unit 110 is composed of a CPU, an MPU, or the like, and controls the entire apparatus and each component.
  • the optical system 1 may be configured as an interchangeable lens that can be detachably attached to the image projection device 100 or may be configured as a built-in lens integrated with the image projection device 100 .
  • the image projection apparatus 100 described above is capable of short-focus, large-screen projection with a compact apparatus.
  • FIG. 28 is a block diagram illustrating an example of an imaging device according to the present disclosure.
  • the imaging device 200 includes the optical system 1 disclosed in the first embodiment, an imaging device 201, a control unit 210, and the like.
  • the imaging device 201 is composed of a CCD (charge-coupled device) image sensor, a CMOS image sensor, or the like, receives an optical image of an object OBJ formed by the optical system 1, and converts it into an electrical image signal.
  • the control unit 110 is composed of a CPU, an MPU, or the like, and controls the entire apparatus and each component.
  • the optical system 1 may be configured as an interchangeable lens that can be detachably attached to the imaging device 200 , or may be configured as a built-in lens integrated with the imaging device 200 .
  • the imaging apparatus 200 described above is capable of short-focus, large-screen imaging with a compact device.
  • the present disclosure is applicable to image projection devices such as projectors and head-up displays, and imaging devices such as digital still cameras, digital video cameras, surveillance cameras in surveillance systems, web cameras, and vehicle-mounted cameras.
  • imaging devices such as digital still cameras, digital video cameras, surveillance cameras in surveillance systems, web cameras, and vehicle-mounted cameras.
  • the present disclosure is applicable to optical systems that require high image quality, such as projectors, digital still camera systems, and digital video camera systems.

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