Projection optical system and image projection device

Abstract

A projection optical system, in which a refractive optical system and a refractive reflective optical element are sequentially arranged from an image display surface side toward a projected surface side. The refractive optical system has a plurality of lens groups consisting of one or more lenses, and also includes a lens driving device for moving at least one of the lens groups in the direction of the optical axis. The refractive reflective optical element has: a reflective surface component having a reflective surface; and a refractive medium portion, which is closely arranged with the reflective surface component. The reflective surface component and the refractive medium portion constitute a single optical element joined at a boundary surface. The incident surface and the exit surface of an imaging light beam emitted from the refractive optical system are formed in the refractive medium portion. The reflective surface is a curved surface with refractive power. In the refractive optical system and the refractive reflective optical element, an intermediate image of one or more images displayed on the image display surface is formed. Between the incident surface and the reflective surface of the refractive reflective optical element, an intermediate image of one or more images displayed on the image display surface is formed.

Description

Technical Field

[0001] The invention relates to a projection optical system and an image projection device. Background Art

[0002] In optical devices such as image projection devices using a reflective projection optical system, such as cameras and projectors, further miniaturization is required, and miniaturization of reflecting mirrors has become a problem.

[0003] As a device for solving such a problem, a refractive reflective element having the properties of a lens having refractive power and a curved reflective mirror is known.

[0004] However, for such a refractive reflective element, generally speaking, since the reflecting surface of the curved reflector is aspherical, the lens side, that is, the incident surface and the exit surface side are composed of the same spherical surface, so the two surfaces become different manufacturing processes, which leads to a problem of increased costs.

[0005] In order to solve this problem, it is conceivable to use a single optical element in which a reflecting surface member having a reflecting surface and a refractive medium portion closely arranged with the reflecting surface member are joined at an interface (for example, see Patent Document 1).

[0006] However, in particular, in projection optical systems, it is preferred to be able to perform so-called focus adjustment, which is to change the focal length of the entire projection optical system while keeping the magnification unchanged. In such focus adjustment, there is a problem that it is difficult to design an optical system that also incorporates a refractive and reflective optical element having a refractive power.

[0007] <Prior Art Literature>

[0008] <Patent Documents>

[0009] Patent Document 1: Japanese Patent Application Publication No. 2020-042103 Summary of the invention

[0010] <Problems to be Solved by the Invention>

[0011] The present invention is made in view of the above problems, and its object is to provide a projection optical system using a refractive reflective element that can easily focus.

[0012] <Methods used to solve the problem>

[0013] In order to solve the above problems, the projection optical system of the present invention is to enlarge and project the image displayed on the image display surface of the image display element onto the projection surface as a projection image. The projection optical system is configured to sequentially configure a refractive optical system and a refractive reflective optical element from the image display surface side toward the projection surface side. The refractive optical system has a plurality of lens groups consisting of one or more lenses. The projection optical system includes a lens driving device that moves at least one lens group in the lens groups in the optical axis direction. The refractive reflective optical element has: a reflective surface component having a reflective surface; and a refractive medium portion that is closely configured with the reflective surface component. The reflective surface component and the refractive medium portion are configured as a single optical element joined at a boundary surface. The incident surface and the exit surface of the imaging light beam emitted from the refractive optical system are formed in the refractive medium portion. The reflective surface is a curved surface with refractive power. In the refractive optical system and the refractive reflective optical element, one or more intermediate images of the images displayed on the image display surface are imaged. Between the incident surface and the reflective surface of the refractive reflective optical element, one or more intermediate images of the images displayed on the image display surface are imaged.

[0014] <Effects of the Invention>

[0015] According to the present invention, it is possible to provide a projection optical system using a refractive reflective element that can be easily focused. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 FIG. 1 is a diagram showing an example of a configuration of an image projection device in an embodiment of the present invention.

[0017] Figure 2 It is a diagram showing an example of the configuration of a lens unit in the first embodiment of the present invention.

[0018] Figure 3 1 is a longitudinal aberration diagram in the first embodiment of the present invention.

[0019] Figure 4 2 is a diagram of lateral aberration in the first embodiment of the present invention.

[0020] Figure 5 It shows that Figure 2 This figure shows an example in which the lens position of the lens unit is changed to Pos1.

[0021] Figure 6 yes Figure 5 Diagram of longitudinal aberration in the illustrated embodiment.

[0022] Figure 7 yes Figure 5 Diagram of lateral aberration in the illustrated embodiment.

[0023] Figure 8 It shows that Figure 2 The figure shows an example in which the lens position of the lens unit is changed to Pos3.

[0024] Fig. 9 yes Figure 8 Diagram of longitudinal aberration in the illustrated embodiment.

[0025] Fig.10 yes Figure 8 Diagram of lateral aberration in the illustrated embodiment.

[0026] Fig.11 It is a diagram showing a modification of the configuration of the lens unit of the present invention.

[0027] Fig.12 It is a diagram showing a second embodiment of the present invention.

[0028] Fig.13 yes Fig.12 Diagram of longitudinal aberration in the illustrated embodiment.

[0029] Fig.14 yes Fig.12 Diagram of lateral aberration in the illustrated embodiment.

[0030] Fig.15 It shows that Fig.12 This is a diagram showing a longitudinal aberration when the lens position of the lens unit is changed to Pos5.

[0031] Fig.16 It shows that Fig.12 This is a diagram showing a longitudinal aberration when the lens position of the lens unit is changed to Pos5.

[0032] Description of Reference Numerals

[0033] 10 Refractive optical system

[0034] 11. First movable lens group

[0035] 12 Second movable lens group

[0036] 13 Third movable lens group

[0037] 11A, 12A, 13A lens drive device

[0038] 20 Refractive-reflective optical elements (cemented lenses)

[0039] 20A Incident surface of refractive-reflective optical element

[0040] 20B Reflective Surface of Refractive-Reflective Optical Components

[0041] 20C Exit surface of refractive-reflective optical element

[0042] 21 Reflective surface parts

[0043] 22 Refractive medium section

[0044] 23 Boundary surface

[0045] 100 Image projection device

[0046] 102 Image display element

[0047] 104 Projection surface

[0048] 200 lens units

[0049] 300 lens units

[0050] LN1~LN17 Lenses that constitute the refractive optical system

[0051] Im1 Intermediate Image DETAILED DESCRIPTION

[0052] As one of the embodiments of the present invention, Figure 1 An example of the configuration of an image projection device is shown in FIG.

[0053] The image projection device 100 includes a light source 101 that emits a light beam L0 that becomes an imaging light beam, and an image display element 102 that displays an image to be projected on an image display surface and imparts image information to the transmitted light beam.

[0054] The image projection device 100 further includes: a lens unit 200 including a projection optical system for projecting an image onto a projection surface 104 as a projection surface; and a control unit for controlling the image display element 102 to display an image to be projected onto the projection surface 104.

[0055] The light source 101 uses a halogen lamp as a light source for emitting light, thereby emitting white light in substantially parallel. Here, a metal halide lamp, a high-pressure mercury lamp, or an LED can also be used as the light source.

[0056] Although light source 101 is a white light source, it can also be a monochromatic light source such as a plurality of laser light sources, a light source that combines light converted into wavelengths corresponding to one or more basic colors such as R, G, B, etc., or a light source that combines the converted light with the monochromatic light of the laser light source.

[0057] The image display element 102 is an image display device that transmits an incident light beam, modulates it spatially, and then emits it to provide image information. In this embodiment, it is a reflective spatial light modulation element such as a DMD (digital micromirror device). It should be noted that the image display element 102 can be a liquid crystal panel, or a device such as a self-luminous light emitting element array can be used. In addition, the image display element 102 can display an image input from an external device of a computer light, or it can display image data formed by a control unit configured inside the image projection device.

[0058] The configuration of the lens unit 200 will be described.

[0059] The optical axis of the incident light to the lens unit 200, i.e., the lens optical axis, is set as the Z axis. Figure 2 The axis parallel to the vertical direction of the paper is set as the Y axis, and the axis perpendicular to the Z axis and the Y axis is set as the X axis. It should be noted that for the directions of the X axis, Y axis, and Z axis, Figure 2 The directions of the arrows shown are respectively set as positive directions.

[0060] like Figure 2 As shown, the lens unit 200 has: a plurality of lenses LN1 to LN17, which are arranged on the Z axis to form a refractive optical system 10; and a bonding lens 20 as a refractive and reflective optical element, which is arranged on the downstream side of the lens LN17 in the Z direction and is used to project the imaging light beam toward the projection surface 104.

[0061] That is, in the present embodiment, the lens unit 200 constitutes a projection optical system in which "a refractive optical system and a refractive reflective optical element are arranged in sequence from the image display surface side toward the projection surface 104 side".

[0062] The refractive optical system 10 is a refractive optical system composed of a plurality of lenses LN1 to LN17. Alternatively, it may be a cemented lens in which two or more of these lenses are cemented to each other. In addition, in this embodiment, although a configuration using 17 lenses is described, the number of lenses constituting the refractive optical system 10 is not limited, and an appropriate number of lenses may be used according to various optical design conditions.

[0063] The joint lens 20 has an incident surface 20A for the imaging beam L1 from the refractive optical system 10 to be incident, a reflecting surface 20B that functions as a concave reflecting mirror, and an emitting surface 20C for emitting the imaging beam L1 reflected by the reflecting surface 20B as a projection beam L2.

[0064] In the cemented lens 20 , the reflective surface member 21 and the refractive medium portion 22 are disposed closely to each other in the boundary surface 23 , and the reflective surface member 21 and the refractive medium portion 22 are integrally formed to constitute a “single optical element”.

[0065] The imaging light beam L1 emitted from the refractive optical system 10 enters the incident surface 20A of the cemented lens 20, is reflected by the reflecting surface 20B from the refractive medium portion 22 via the reflecting surface member 21, and then is emitted from the emitting surface 20C toward the projection surface 104 as the projection surface.

[0066] Here, among the incident surface 20A, the reflecting surface 20B, and the emitting surface 20C of the cemented lens 20, at least the reflecting surface 20B is a "curved surface having a refractive power", and at least one of the incident surface 20A and the emitting surface 20C may have a refractive power. It should be noted that when having a refractive power, it may be positive or negative. In addition, the shape of the surface having the refractive power may be a spherical shape such as a convex spherical surface or a concave spherical surface, or may be an aspherical shape, a deformed shape such as a cylindrical surface, or a free-form surface.

[0067] The image display surface of the image display element 102 and the projected image enlarged and projected on the projection surface 104 are in a conjugate relationship through the projection optical system. In addition, the projection optical system forms an "intermediate image" of the image displayed on the image display surface inside the cemented lens 20, in other words, at at least one position in the optical path from incident to the incident surface 20A to exiting at the exit surface 20C.

[0068] In addition, since at this time one or more intermediate images are formed inside the cemented lens 20, there is a case where an image is temporarily formed in the refractive optical system 10. Therefore, one or more intermediate images are formed in the entire projection optical system.

[0069] The reflective surface member 21 has a concave and aspherical reflective surface 20B on the inner side, which is arranged on the +Z direction side of the refractive medium portion 22. It should be noted that in this embodiment, although the boundary surface 23 with the refractive medium portion 22 is set to a surface parallel to the XY plane, it is not limited to this configuration.

[0070] The refractive medium portion 22 is made of an optical material such as glass or plastic. Figure 2 The lower part of the middle part is formed with an incident surface 20A, and the -Z direction side Figure 2 An exit surface 20C is formed in the upper part of the sphere, and the incident surface 20A and the exit surface 20C are formed on the same spherical surface.

[0071] The reflective surface component 21 and the refractive medium portion 22 are joined at the boundary surface 23, so that the joined lens 20 functions as a refractive reflective optical element whose surface on the -Z direction side is a spherical surface and whose surface on the +Z direction side is an aspherical surface. It should be noted that the "boundary surface" may also be referred to as the "joining surface" between the reflective surface component 21 and the refractive medium portion 22.

[0072] Generally speaking, optical elements are processed by lens grinding, molding with metal molds, and the like.

[0073] However, in the case of performing reflection and refraction simultaneously in this way, it is difficult because the thickness of the lens increases.

[0074] By forming the reflective surface member 21 and the refractive medium portion 22 integrally as in this embodiment, a refractive-reflective optical element that is easier to manufacture and less expensive can be manufactured.

[0075] However, if the two optical elements are simply joined together, there is a concern that foreign matter attached to the boundary surface 23 may deteriorate the optical performance.

[0076] Therefore, in this embodiment, Figure 2 As shown in the main optical path diagram, the intermediate image Im1 is formed inside the cemented lens 20, specifically, at least one between the incident surface 20A and the reflecting surface 20B of the cemented lens 20.

[0077] In this way, by arranging the intermediate image Im1 inside the cemented lens 20 , the influence of defects such as foreign matter that enters the boundary surface 23 can be suppressed.

[0078] In this embodiment, the projection optical system 10 is composed of a plurality of movable lens groups.

[0079] Specifically, it has a first movable lens group 11 composed of lens LN1, a second movable lens group 12 composed of lens LN11, and a third movable lens group 13 composed of lenses LN12 to LN15. These lens groups are driven integrally using a first cam 11a, a second cam 12a, and a third cam 13a, which are lens driving devices for moving them in the optical axis direction, i.e., the ±Z direction.

[0080] It should be noted that, in this embodiment, since the first cam 11a, the second cam 12a, and the third cam 13a can all be known lens driving devices, and their cam shapes can also be appropriately designed according to the size and weight of the lens, their description is omitted.

[0081] For the projection optical system 10 , it is preferred that the projection surface 104 can be freely set within a certain range in design, and it is required to project the image on the image display surface in a focused state on such projection surface 104 .

[0082] Generally speaking, in such a projection optical system 10 , it is preferable to have a configuration that enables so-called focal length adjustment (focusing) after the position of the projection surface 104 is determined.

[0083] In this embodiment, the focal length can be adjusted by making the first cam 11a, the second cam 12a, and the third cam 13a function as a lens driving device for moving the first movable lens group 11, the second movable lens group 12, and the third movable lens group 13 in the optical axis direction, i.e., the ±Z direction.

[0084] In the focal length adjustment, the adjustment is performed as follows: the positions of the image display surface and the projection surface 104 do not change, and the image displayed on the image display surface is formed on the projection surface 104 by changing the focus of the entire projection optical system 10.

[0085] That is, when the focal length is adjusted, in principle, it is required that the angle of the main light emitted from the image display surface, which is emitted from the emission surface 20C toward the screen, does not change.

[0086] In this way, the angle variation of the light emitted from the emission surface 20C to the projection surface 104 is suppressed, which is equivalent to that the height of the principal light does not change before and after the movement of the first movable lens group 11, the second movable lens group 12, and the third lens group 13. According to such a configuration, since the position of the projection surface 104 does not change, the ratio of the size of the image projected on the projection surface 104 to the image display element 102 should not change. That is, the magnification variation during the focal length adjustment can be suppressed to a low level.

[0087] Next, numerical examples are shown together with specific optical system data in such a lens unit 200.

[0088] like Figure 2 As shown, the refractive optical system 10 in the numerical example is composed of 17 lenses LN1 to LN17 arranged in order from the object side to the image side. The four lenses LN3 to LN6 are cemented, and an aperture stop S is arranged between the lens LN8 and the lens LN9.

[0089] The cemented lens 20 is a "biconvex lens shape", the incident surface 20A and the outgoing surface 20C are the same lens surface, and the reflective surface 20B is formed by using a reflective film formed by vapor deposition on the lens surface as a "reflective surface member".

[0090] In addition, in the numerical embodiment, an "oblique beam" is used as the imaging beam L1. Figure 2As shown, the image displayed on the image display element 102 is displaced in the +Y direction relative to the lens optical axis of the projection optical system. The oblique light beam as the imaging light beam L1 forms an intermediate image Im1 as an inverted image inside the refractive medium portion 22 under the positive refractive power of the incident surface 20A of the refractive optical system 10 and the cemented lens 20.

[0091] Taking the intermediate image Im1 as the object, under the effect of the positive refractive power of the reflection surface 20B and the emission surface 20C, the projection image is enlarged and projected toward the projection surface 104. It should be noted that, for the following embodiments, the illustration of the projection surface 104 is omitted.

[0092] It should be noted that the lens located on the image side of the aperture stop can be set to a shape in which the unused lens portion is cut off (for example, a shape like a D-cut lens) in a manner not to "block" the imaging light beam L1 reflected by the reflection surface 20B.

[0093] The projection optical system of the first embodiment assumes the following manner: an image displayed on the image display surface of the image display element 102 having an image display surface with pixels: 1920×1080 and a pitch: 7.56 μm is enlarged and projected onto a projection surface 104 having a diagonal length of 106.7 inches.

[0094] When the surface number S0 is set as the projection surface 104 as a screen for enlarged projection, and the surface number Si is set as the image display surface of the image display element 102 , the S0 surface and the Si surface are optically conjugated to each other through the projection optical system 10 .

[0095] That is, for example, when the surface interval D of the S0 plane is -554.813, the image projection device 100 is in a "focused" state with respect to the projection plane 104 located -554.813 mm in front. The ratio of the size of the projection plane 104 to the size of the image display element 102 is displayed as a "magnification".

[0096] In addition, the state where the actual position of the projection plane 104 is different from the position of the S0 plane is a "focus shift" state. The adjustment of changing the focus shift state so that the distance from the image projection device 100 to the projection plane 104 is consistent with the distance to the S0 plane in the lens system of the projection optical system 10 by using the lens driving device to move the first movable lens group 11, the second movable lens group 12, and the third movable lens group 13 in the ±Z direction by a predetermined amount is called "focal length adjustment" (focusing).

[0097] In this way, if actual application is considered, although the image projection device 100 of this embodiment has the effect of "the magnification does not change before and after the focal length is adjusted", when considered as a projection optical system 10, since the focal distance is equivalent to a change through this movement, the magnification of the projection surface 104 relative to the image display element 102 changes when taking the respective positions of Pos1, Pos2, and Pos3 described later.

[0098] For the * surface shown in Table 1, the aspheric surface shown in Mathematical Formula 1 is used, and the aspheric surface coefficients are shown in Table 2.

[0099] In the numerical example shown in Table 1, the projection distance is "-554.813 mm" shown in the surface number S0, and the projection magnification is "162.7 times".

[0100] In the optical system data shown below, the "surface number" is represented by a number counted from the magnification side toward the reduction side, the projection surface is set as the screen surface as "S0", and the image display surface is set as "Si".

[0101] “R” represents the curvature radius of each surface of the aperture stop S including the color synthesis prism P (the aspherical surface has the paraxial curvature radius).

[0102] "D" represents the facet spacing above the optical axis.

[0103] “Nd” and “Vd” represent the refractive index and Abbe number of the material of each lens at the d-line.

[0104] The “effective diameter” means the optically effective diameter of each surface. The unit of a quantity having a length dimension is “mm” unless otherwise specified.

[0105] Radius of curvature: The surface marked with (※) in the R column is an "aspherical surface".

[0106] The aspheric surface is expressed by the well-known formula below: the aspheric quantity: Z, the height from the optical axis: r, the cone constant: k, and the aspheric coefficients of even orders from 2nd to 20th: A, B,..., G, H, J.

[0107] (Mathematical formula 1)

[0108]

[0109] The optical system data of the embodiment are shown in Table 1. It should be noted that, for the parts indicated by △ in Table 1, the values ​​of the respective positions in Table 3 are variable as described later, and the embodiments shown in Pos1, Pos2, and Pos3 respectively show the situations after the first movable lens group 11, the second movable lens group 12, and the third movable lens group 13 are moved.

[0110] (Table 1)

[0111] Face number R D nd vd Effective diameter S0 -554.813 (Δ) S1 -45.764 -30.828 1.51633 64.1 73.193 S2 -14.172 1.51633 64.1 30.252 S3 31.328(※) 14172 1.51633 64.1 48.655 S4 30.828 1.51633 64.1 48.481 S5 -45.764 1.044 54.296 S6 -105.243(※) 7.000 1.50900 56.0 54.450 S7 -92.983(※) 1.500 59.651 S8 -72.529 9.203 1.59270 35.4 60.195 S9 -46.774 2.654(Δ) 62.350 S10 -42.167(※) 4.981 1.50900 56.0 60.567 S11 55.595(※) 12.375 59.955 S12 -58.422 2.800 1.59270 35.4 58.706 S13 116.180 4.819 60.192 STO -641.831 13.933 1.51860 69.9 60.267 S15 -44.200 7.953 61.132 S16 -17.644(※) 6.518 1.50900 56.0 58.951 S17 -19.419(※) 10.923(Δ) 56.391 S18 -169.292 4.647 1.72000 46.0 50.950 S19 -64.281 25.800(Δ) 50.923 S20 -88.110 1.600 1.62041 60.3 27.394 S21 56.168 1.500 26.064 S22 28.930 5.216 1.77047 29.7 25.430 S23 -1255.067 11.603 24.478 S24 3.000 15.250 S25 1.033 13.806 S26 -23.884 0.900 1.85150 40.8 13.812 S27 52.862 0.200 15.175 S28 22.940 4.784 1.58913 61.1 17.578 S29 -42.768 0.300 18.409 S30 28.385 0.950 1.80610 33.3 19.600 S31 15.744 10.385 1.51860 69.9 19.289 S32 -13.370 1.800 1.83400 37.2 19.702 S33 22.262 7.621 1.51860 69.9 24.188 S34 -47.419 0.716 26.440 S35 48.397(※) 11.437 1.51633 64.1 33.093 S36 -27.888(※) 0.642(Δ) 35.224 S37 -73.679 4.263 1.86966 20.0 36.200 S38 -35554 9.460(Δ) 36.774 S39 3.000 32.804 S40 25.000 1.51680 64.2 31.981 S41 2.000 27.494 S42 3.000 1.50999 63.6 26.948 S43 0.450 26.400 Si 0.000

[0112] "Aspherical data"

[0113] Table 2 shows the aspherical surface data.

[0114] In the data of aspherical surfaces, for example, "2.507680E-11" means "2.507680×10 -11 ”.

[0115] As shown in "Table 1", the incident surface (S28) and the exit surface (S30) of the reflective-refractive optical element are the same surface and are "convex spherical surfaces", and the reflecting surface (S29) is an "aspherical surface that is rotationally symmetric with respect to the optical axis".

[0116] (Table 2)

[0117] (※) Aspheric coefficient of aspheric surface

[0118] S3 S6 S7 S10 S11 S16 S17 S35 S36 RDY 31.328 -105.243 -92.983 -42.167 55.595 -17.644 -19.419 48.397 -27.888 K -0.331349 9.542763 3.108759 -20.649338 0.88504 -1.137379 -0.641497 -10.304368 -0.810486 A -9.140098E-06 -2.856348E-05 -1.069279E-05 2.782538E-05 -4.427746E-06 -2.132331E-05 -2.106591E-06 3.190367E-08 7.302933E-06 B 9.921973E-09 3.189144E-08 2.566219E-08 -2.987491E-08 8.282329E-09 7.904902E-08 3.826316E-08 8.901912E-09 4.298194E-10 C -2.507680E-11 1.017939E-11 -2.085236E-11 2.382361E-11 -4.894987E-11 -5.125389E-11 -1.005569E-11 -1.656343E-11 -1.031644E-12 D 3.051300E-14 -3.364949E-14 9.736959E-17 -1.773010E-14 6.531992E-14 -3.788105E-14 1.566651E-14 -1.432963E-14 1.560188E-14 E 6.576752E-18 -1.086330E-17 3.316313E-18 2.223998E-18 -4.013319E-17 6.390679E-17 -4.224711E-17 5.434224E-16 -6.07644E-17 F -7.391163E-20 4.363750E-20 1.483475E-21 2.540891E-21 1.070782E-20 -2.185024E-20 3.117732E-20 -2.113616E-18 6.56919E-19 G 8.50221E-23 -1.27907E-23 0 0 0 0 0 1.94357E-21 1.62178E-21 H -3.21951E-26 0 0 0 0 0 0 0 0 J 0 0 0 0 0 0 0 0 0

[0119] exist Figure 3 as well as Figure 4 2 and 3 show aberration diagrams of the embodiment.

[0120] Figure 3 This is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion. Figure 4 This is a diagram showing lateral aberration of coma.

[0121] In the astigmatism diagram, the "thick lines" are associated with the "meridional rays" and the "thin lines" are associated with the "sagittal rays". Figure 3 , Figure 4 It is clear that aberrations are well corrected and the projection optical system of the embodiment has high performance.

[0122] in addition, Figure 5 The first movable lens group 11, the second movable lens group 12, and the third movable lens group 13 are shown in FIG. Figure 2 FIG. 1 shows the ray diagram of Pos1 after Pos2 is moved.

[0123] The position Pos1 of the lens group assumes a mode of enlarging and projecting the image displayed on the image display element 102 on the projection plane 104 having a diagonal length of 305.9 inches.

[0124] At this time, as shown in Table 3, the interval -1632.778 mm of S0 in Pos1 actually represents the projection distance, and the image on the image display surface is projected onto the projection surface 104 at a magnification of 466.6.

[0125] exist Figure 6 as well as Figure 7 The aberration diagram at this time is shown in .

[0126] Figure 6 This is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion. Figure 7 This is a diagram showing lateral aberration of coma.

[0127] (Table 3)

[0128] S0 S9 S17 S19 S36 S38 Pos.1 -1632.777 2.000 12.021 25.357 0.753 9.350 Pos.2 -554.813 2.654 10.923 25.800 0.642 9.460 Pos.3 -306.169 3.405 9.544 26.428 0.500 9.603

[0129] in addition, Figure 8 The first movable lens group 11, the second movable lens group 12, and the third movable lens group 13 are shown in FIG. Figure 2 The figure shows the ray diagram of Pos3 after Pos2 is moved.

[0130] The position Pos3 of the lens group assumes a mode of enlarging and projecting the image displayed on the image display element 102 on the projection plane 104 having a diagonal length of 60.7 inches.

[0131] At this time, as shown in Table 3, the interval -306.169 mm of S0 in Pos3 substantially represents the projection distance, and the image on the image display surface is projected onto the projection surface 104 at a magnification of 92.6.

[0132] exist Fig. 9 as well as Fig.10 The aberration diagram at this time is shown in .

[0133] Fig. 9 This is a longitudinal aberration diagram of spherical aberration, astigmatism, and distortion. Fig.10 This is a diagram showing lateral aberration of coma.

[0134] In this way, by setting Pos2 as the reference position and moving each lens group to the respective positions of Pos1 and Pos3, the projection distance can be changed between -306.169 and -1632.778 mm, the focal length can be adjusted, and an enlarged projection of 60.7 inches to 305.9 inches can be performed.

[0135] However, when the position of each lens group is changed to Pos1 to Pos3 using the lens driving device for the focus adjustment, if the angle of the main light from the exit surface 20C of the cemented lens 20 toward the projection surface 104 of the maximum object height 12.5 mm in the image display element 102 changes, the position of the image on the projection surface 104 changes. In this case, the positional relationship between the screen and the image projection device 100 needs to be adjusted every time the focus adjustment is performed.

[0136] Therefore, in this embodiment, the performance of each lens is determined in such a way that the change in the height of the main light of the projection optical system 10 is suppressed within a prescribed range when the lens driving device moves the first movable lens group 11, the second movable lens group 12, and the third movable lens group 13 respectively.

[0137] In other words, in this embodiment, the performance of each lens is determined so that the angle of the outgoing light beam is suppressed within a predetermined range before and after the movement for focal length adjustment.

[0138] Specifically, the ray angles of the principal ray at the maximum object height of 12.5 mm on the image display element 102 side in this embodiment from the exit surface 20C of the cemented lens 20 toward the projection surface 104 are Pos1: 74.2259 degrees, Pos2: 74.2532 degrees, and Pos3: 74.2652 degrees. That is, the angular variation of the ray angle projected onto the screen is suppressed to within the range of -0.0273 to 0.012 degrees, and the magnification variation is suppressed to within -0.18 to 0.08%.

[0139] In this way, by suppressing the magnification change before and after the movement of the lens group when adjusting the focal length to within 0.5%, the focal length adjustment can be performed smoothly.

[0140] In addition, Figure 2 In the embodiment of the present invention, for the cemented lens 20 used as the refracting-reflecting optical element, although the boundary surface 23 between the refracting medium portion 22 and the reflecting surface member 21 is described as a flat surface, the present invention is not limited to this configuration. Fig.11 As shown, the boundary surface 23 may also be a curved surface.

[0141] It should be noted that when the boundary surface 23 is set as a curved surface, it is preferably configured so that the position where the intermediate image Im1 is formed is located at a position that does not overlap with the boundary surface 23, and the positions where the main light rays in the imaging beam L1 are concentrated are all arranged inside the refractive medium portion 22 in the cemented lens 20.

[0142] With this configuration, since the intermediate image Im1 does not extend across the boundary surface 23 , the refracting reflective element can be manufactured more easily and at a low cost.

[0143] In this way, by arranging the interface 23 of the cemented lens 20 and the intermediate image Im1 so as not to overlap each other, the influence of dirt, foreign matter, and the like on the interface 23 can be further reduced.

[0144] In addition, through this structure, the refractive power of the boundary surface 23 can also be considered and adjusted. In addition, according to the shape of the boundary surface 23, the shape of the refractive medium part 22 and the shape of the reflective surface component 21 can be considered, thereby achieving further miniaturization of the cemented lens 20 and making it easier and cheaper to manufacture the cemented lens 20.

[0145] As a second embodiment of the present invention, Fig.12 2 shows the lens unit 300. In addition, about the structure of the lens unit 300 which is the same as that of the already described 1st Example, the same code|symbol is attached|subjected, and description is abbreviate|omitted suitably.

[0146] The lens unit 300 is Figure 2 The lens configuration of Pos2 in the projection optical system 10 shown is used as a reference to reduce the number of movable lens groups.

[0147] In this embodiment, as shown in Table 4, among the lens groups that operate, only the third lens group 13 other than the first movable lens group 11 and the second lens group 12 in the first numerical example operates, and the positions of the surface numbers S9 and S17 are changed.

[0148] (Table 4)

[0149] S0 S9 S17 Pos.4 -604.813 2.576 11.001 Pos.2 -554.813 2.654 10.923 Pos.5 -504.813 2.749 10.828

[0150] Regarding Pos2 shown in Table 4, it is the same optical performance as Pos2 in the first numerical example, and repeated description is omitted.

[0151] The position indicated by Pos4 in Table 4 assumes a method of enlarging and projecting the image displayed on the image display element 102 on the projection surface 104 having a diagonal length of 115.9 inches.

[0152] As shown in Table 4, the interval of S0, -604.813 mm, represents the actual projection distance, and is projected onto the projection surface 104 at an image magnification of 176.8 times.

[0153] In addition, Fig.13 The longitudinal aberration diagram in this positional relationship is shown in Fig.14 The horizontal image is shown in

[0154] In addition, Table 4 also describes the respective configurations in Pos5 after the second movable lens group 12 and the third movable lens group 13 are moved from Pos2.

[0155] The position Pos5 of the lens group assumes a mode of enlarging and projecting the image displayed on the image display element 102 on the projection plane 104 having a diagonal length of 97.5 inches.

[0156] At this time, as shown in Table 4, the interval -504.813 mm of S0 in Pos5 represents the actual projection distance, and the image on the image display surface is projected onto the projection surface 104 at a magnification of 148.7.

[0157] exist Fig.15 as well as Fig.16 The aberration diagram at this time is shown in .

[0158] Fig.15 and Fig.13 The same is the longitudinal aberration diagram of spherical aberration, astigmatism, and distortion. Fig.16 and Fig.14 The same is true for lateral aberration diagrams showing coma.

[0159] As described above, with Pos2 as a reference, each lens group can be moved to the respective positions of Pos4 and Pos5 through a lens moving group, namely the third lens moving group 13, so that the projection distance can be changed to -504.813 to -604.813 mm, the focal length can be adjusted, and an enlarged projection of 97.5 inches to 115.9 inches can be performed.

[0160] In the present embodiment as well, the performance of each lens is determined so that when the lens driving device moves the third movable lens group 13 , the change in the height of the principal ray of the projection optical system 10 is suppressed within a predetermined range.

[0161] In other words, in the present embodiment, the performance of each lens is determined so that the angle of the outgoing light beam is suppressed within a predetermined range before and after the movement for focal length adjustment.

[0162] Specifically, the ray angles of the principal ray at the maximum object height of 12.5 mm on the image display element 102 side in this embodiment from the exit surface 20C of the cemented lens 20 toward the projection surface 104 are Pos4: 74.2414 degrees, Pos2: 74.2532 degrees, and Pos5: 74.2677 degrees. That is, the angular variation of the ray angle projected onto the screen is suppressed to within the range of -0.0118 to 0.0145 degrees, and the magnification variation is suppressed to within -0.08 to 0.10%.

[0163] In this way, by suppressing the magnification variation of the entire lens unit 300 before and after the movement of the lens group when adjusting the focal length to within 0.5%, the focal length adjustment can be performed smoothly.

[0164] Although preferred embodiments of the invention have been described above, the invention is not limited to the above-mentioned specific embodiments, and various modifications / changes are possible within the scope of the gist of the invention described in the claims unless otherwise specified in the above description.

[0165] For example, although the refractive reflective optical element is a "single optical element", "single" is in terms of form. Although the above description is made of a case where the refractive medium portion is a single structure, the structure of the refractive medium portion is not limited to this. For example, it can be a composite structure of two or more different optical media, such as a joint lens method. If the refractive medium portion is composed of multiple optical media, the parameters for adjusting the performance of the projection optical system increase, and the design of the projection optical system becomes easier.

[0166] The effects described in the embodiments of the present invention are merely examples of favorable effects produced by the invention, and the effects based on the invention are not limited to “the effects described in the embodiments”.

Claims

1. A projection optical system that enlarges and projects an image displayed on an image display surface of an image display element onto a projection surface as a projection image. The projection optical system is composed of a refractive optical system and a refractive reflective optical element arranged in sequence from the image display surface side toward the projection surface side. The refractive optical system is composed of a first movable lens group, a second movable lens group and a third movable lens group arranged in sequence from the image display surface side toward the projection surface side. The first movable lens group, the second movable lens group and the third movable lens group are respectively composed of one or more lenses. An aperture stop is provided between the first movable lens group and the second movable lens group. The projection optical system includes a lens driving device for moving the first movable lens group, the second movable lens group and the third movable lens group in the direction of the optical axis. The refractive reflective optical element comprises: a reflective surface component having a reflective surface; and a refractive medium portion, which is closely arranged with the reflective surface component, the reflective surface component and the refractive medium portion constitute a single optical element joined at a boundary surface, the incident surface and the exit surface of the imaging light beam emitted from the refractive optical system are formed on the refractive medium portion, the reflective surface is a curved surface with refractive power, In the refractive optical system and the refractive-reflective optical element, an intermediate image of at least one image displayed on the image display surface is formed. between the incident surface and the reflective surface of the refractive-reflective optical element, forming one or more intermediate images of the image displayed on the image display surface; The projection optical system is configured so that when the focal length is adjusted by the lens driving device, a change in magnification before and after the movement of the movable lens group of the refractive optical system is suppressed to within 0.5%.

2. The projection optical system according to claim 1, wherein: The above-mentioned boundary surface is a plane.

3. The projection optical system according to claim 1, wherein: The above boundary surface is a curved surface.

4. The projection optical system according to any one of claims 1 to 3, wherein: The intermediate image is formed at a position that does not overlap with the boundary surface.

5. The projection optical system according to any one of claims 1 to 3, wherein: The refractive optical system is composed of 17 lenses LN1 to LN17 arranged in sequence from the image display surface side toward the projection surface side. The first movable lens group is composed of lens LN1, the second movable lens group is composed of lens LN11, and the third movable lens group is composed of lens LN12, lens LN13, lens LN14 and lens LN15. The aperture stop is disposed between the lens LN8 and the lens LN9 between the first movable lens group and the second movable lens group.

6. An image projection device, comprising: The projection optical system according to any one of claims 1 to 5; Light source; and An image display element displays an image on an image display surface.

Images