Illumination optical system and image projection device

Abstract

To enable the same kind of lens array to be used even if a direction of a light modulation element changes.SOLUTION: An illumination optical system comprises a lens array 1 that emits light irradiated from a light source toward a light modulation element, and a holding section 2 that holds the lens array. The lens array includes an optical function region 11 and has a rectangular outer shape in plan view, and a center position of the optical function region when the lens array is held in a first state is equal to a center position of the optical function region when the lens array is held in a second state rotated by 90 degrees with respect to the first state within a plane including the optical function region.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an illumination optical system and an image projection device. [Background technology]

[0002] 2. Description of the Related Art Conventionally, an illumination optical system having a lens array that outputs light emitted from a light source toward a light modulation element has been disclosed (see, for example, Patent Document 1). Summary of the Invention [Problem to be solved by the invention]

[0003] However, in the configuration of Patent Document 1, using different types of lens arrays depending on the change in the orientation of the light modulation element may reduce the development efficiency of the illumination optical system or increase the cost of the illumination optical system.

[0004] An object of the present invention is to enable the use of the same type of lens array even if the orientation of the light modulation element is changed. [Means for solving the problem]

[0005] An illumination optical system according to one aspect of the present invention includes a lens array that outputs light emitted from a light source toward a light modulation element, and a holder that holds the lens array, the lens array including an optical function region and having a planar view of rectangular shape and the center position of the optical function area when the lens array is held in a first state is equal to the center position of the optical function area when the lens array is held in a second state rotated 90 degrees from the first state within a plane including the optical function area. Effect of the Invention

[0006] According to the present invention, the same type of lens array can be used even if the orientation of the light modulation element is changed. [Brief description of the drawings]

[0007] [Figure 1] 1(a) is a diagram of an example of the configuration of an image projection device according to an embodiment, in which FIG. 1(a) is a diagram of the overall configuration, FIG. 1(b) is a diagram of a fly's eye lens viewed from the direction of arrow 20 in FIG. 1(a), and FIG. 1(c) is a diagram of a light modulation element viewed from the direction of arrow 30 in FIG. 1(a). [Diagram 2] 2A and 2B are diagrams showing an example of abutment of a fly-eye lens against a holder according to the first embodiment, in which FIG. 2A shows a 0 degree state and FIG. 2B shows a 90 degree state. [Diagram 3] 3(a) and 3(b) are diagrams showing the operation of the illumination optical system according to the first embodiment, in which FIG. 3(a) is a diagram showing the overall configuration, FIG. 3(b) is a diagram showing the fly's eye lens as viewed from the direction of arrow 20 in FIG. 3(a), and FIG. 3(c) is a diagram showing the light modulation element as viewed from the direction of arrow 30 in FIG. 3(a). [Figure 4] 4A and 4B are diagrams of a fly's eye lens according to a first modified example, where FIG. 4A is a diagram of the 0 degree state and FIG. 4B is a diagram of the 90 degree state. [Diagram 5] 5A and 5B are diagrams of a fly's eye lens according to a second modified example, where FIG. 5A is a diagram of the 0 degree state and FIG. 5B is a diagram of the 90 degree state. [Figure 6] 6A and 6B are diagrams of a fly's eye lens according to a third modified example, where FIG. 6A is a diagram of the lens in a 0 degree state, and FIG. 6B is a diagram of the lens in a 90 degree state. [Figure 7] 7A and 7B are diagrams of a fly's eye lens according to a fourth modified example, where FIG. 7A is a diagram of a 0 degree state and FIG. 7B is a diagram of a 90 degree state. [Figure 8] 8A and 8B are diagrams showing an example of abutment of a fly-eye lens against a holder according to a second embodiment, where FIG. 8A is a diagram showing a 0 degree state, and FIG. 8B is a diagram showing a 90 degree state. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In each drawing, the same components are denoted by the same reference numerals, and duplicated explanations will be omitted as appropriate.

[0009] Furthermore, the embodiments shown below are examples of an illumination optical system and an image projection device for embodying the technical concept of the present invention, and the present invention is not limited to the embodiments shown below. The dimensions, materials, shapes, relative positions, etc. of the components described below are intended to be illustrative, and are not intended to limit the scope of the present invention, unless otherwise specified. Furthermore, the sizes and positional relationships of the components shown in the drawings may be exaggerated to clarify the explanation.

[0010] In the figures shown below, directions may be indicated by the X-axis, Y-axis, and Z-axis, but the X-direction along the X-axis indicates a predetermined direction in an array plane in which lenses are arranged in a lens array of an illumination optical system according to an embodiment, the Y-direction along the Y-axis indicates a direction perpendicular to the predetermined direction in the array plane, and the Z-direction along the Z-axis indicates a direction perpendicular to the array plane.

[0011] Additionally, the X direction in which the arrow points is denoted as the +X direction and the opposite direction of the +X direction is denoted as the -X direction, the Y direction in which the arrow points is denoted as the +Y direction and the opposite direction of the +Y direction is denoted as the -Y direction, the Z direction in which the arrow points is denoted as the +Z direction and the opposite direction of the +Z direction is denoted as the -Z direction. However, this does not limit the orientation when the illumination optical system is in use, and the orientation of the illumination optical system is arbitrary.

[0012] The illumination optical system according to the embodiment includes a lens array that emits light irradiated from a light source toward a light modulation element, and a holder that holds the lens array. Such an illumination optical system is an optical system used in an image projection device such as a projector or a head-up display mounted on a vehicle. The light modulation element is an element that modulates incident light and emits it, and specifically includes a DMD (Digital Micromirror Device) or the like.

[0013] For example, when the orientation of a light modulation element having a substantially rectangular shape in a plan view is changed by 90 degrees in response to a model change of an image projection device, preparing a different type of lens array in accordance with the change may result in a decrease in development efficiency of the illumination optical system and an increase in cost. Note that when the orientation of the light modulation element is changed by 90 degrees, it refers to a case where the orientation of the light modulation element is changed from a 0 degree state to a 90 degree rotated state within the plane when the light modulation element is viewed in a plan view.

[0014] In the embodiment, the lens array includes an optical function area and has a rectangular outer shape in a plan view, and the center position of the optical function area when the lens array is held in a first state is equal to the center position of the optical function area when the lens array is held in a second state rotated 90 degrees from the first state in a plane including the optical function area. This makes it possible to use the same type of lens array even if the orientation of the light modulation element used in the illumination optical system changes, and suppresses a decrease in development efficiency and an increase in cost of the illumination optical system.

[0015] Here, the optical function area refers to an area in a lens array where a desired optical function of the lens array can be obtained. For example, an area in a lens array where a plurality of lenses are arranged corresponds to the optical function area.

[0016] Also, the angle does not have to be exactly 90 degrees, it can be approximately 90 degrees. This "approximate" means that a deviation that is generally considered to be an error is acceptable. An example of a deviation that is generally considered to be an error is a deviation within the normal tolerance for angle dimensions according to JIS B0405.

[0017] Similarly, the central positions of the lens arrays are not required to be exactly the same, but may be approximately equal. Note that the meaning of "approximately" in the embodiments is the same even when it is used in a manner other than approximately 90 degrees or approximately equal.

[0018] Hereinafter, the embodiment will be described by taking an image projection device having an illumination optical system according to the embodiment as an example.

[0019] [Embodiment] (Configuration example of image projection device 10) First, the configuration of an image projection device 10 according to an embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram showing an example of the configuration of the image projection device 10. Fig. 1(a) is a diagram showing the overall configuration, Fig. 1(b) is a diagram showing a fly-eye lens 1 included in the image projection device 10 as viewed from the direction of an arrow 20 in Fig. 1(a), and Fig. 1(c) is a diagram showing a light modulation element 7 included in the image projection device 10 as viewed from the direction of an arrow 30 in Fig. 1(a).

[0020] The image projection device 10 is a front projection type projector that projects an image onto a screen. Examples of such image projection devices 10 include projectors used for presentations and head-up displays (HUDs) mounted on automobiles, motorcycles, airplanes, and the like.

[0021] As shown in FIG. 1, the image projection device 10 includes a fly's eye lens 1, a holding portion 2, a first field lens 3, a folding mirror 4, a second field lens 5, a total reflection prism 6, a light modulation element 7, and a projection optical system 8.

[0022] Illumination light Lr indicated by a white arrow in Fig. 1 is an example of light irradiated from a light source. A fly-eye lens 1, a first field lens 3, and a folding mirror 4, which are arranged successively at a distance from the upstream side in the propagation direction of the illumination light Lr, guide the illumination light Lr to a light modulation element 7 via a second field lens 5 and a total reflection prism 6. Of these, the fly-eye lens 1 and the holder 2 constitute an illumination optical system 50.

[0023] The fly-eye lens 1 has a first fly-eye lens 1A and a second fly-eye lens 1B. Each of the first fly-eye lens 1A and the second fly-eye lens 1B is an example of a lens array that emits the illumination light Lr emitted from a light source toward the light modulation element 7. Note that the first fly-eye lens 1A and the second fly-eye lens 1B have the same configuration except for the arrangement position and orientation, and therefore will be collectively referred to as the fly-eye lens 1 below unless otherwise distinguished.

[0024] As shown in Fig. 1(b), the fly's eye lens 1 is a plate-like member including an optical function region 11 and having a substantially rectangular outer shape in a planar view. A plurality of lenses 111 are arranged in a two-dimensional array in the optical function region 11. In the example shown in Fig. 1(b), the plurality of lenses 111 are arranged in a two-dimensional array in the XY plane.

[0025] The lenses 111 each have a generally rectangular outer shape with the longitudinal direction along the Y axis in a plan view, and have a convex spherical or aspherical shape protruding toward the Z direction. The lenses 111 all have the same shape, but are not limited to this and may have different shapes.

[0026] The first fly-eye lens 1A and the second fly-eye lens 1B are preferably installed so that their convex surfaces face opposite each other. In other words, the lens 111 in the first fly-eye lens 1A is preferably installed so that its convex surface protrudes in the -Z direction, and the lens 111 in the second fly-eye lens 1B is preferably installed so that its convex surface protrudes in the +Z direction.

[0027] The fly-eye lens 1 includes the abutment surface 12 as an end surface. Here, the end surface refers to a surface included in the outer circumferential surface that intersects with the surface on which the lenses 111 of the fly-eye lens 1 are arranged.

[0028] The abutting surface refers to a surface that abuts against an abutted surface to position the fly-eye lens 1. The abutting surface 12 is a surface that has higher flatness and higher precision of the perpendicularity between the abutting surfaces compared to end faces other than the abutting surface 12.

[0029] The abutted surface refers to a surface that is provided on the holding part 2 that holds the fly-eye lens 1 and serves as a reference surface for positioning the fly-eye lens 1 by abutting the abutting surface.

[0030] The abutment surface 12 includes a first abutment surface 12a, a second abutment surface 12b substantially perpendicular to the first abutment surface 12a, and a third abutment surface 12c substantially perpendicular to the first abutment surface 12a. More specifically, of the four end surfaces constituting the outer shape, the first end surface includes the first abutment surface 12a, the second end surface includes the second abutment surface 12b, and the third end surface includes the third abutment surface 12c.

[0031] The optical function area center 15 is the center position of the optical function area 11 .

[0032] Such a fly-eye lens 1 is manufactured by molding a resin material that is optically transparent to the wavelengths included in the irradiated light Lr. However, the present invention is not limited to this, and the fly-eye lens 1 may be manufactured using a glass material or the like that is optically transparent to the wavelengths included in the irradiated light Lr.

[0033] The holding unit 2 is a box-shaped member that holds the fly-eye lens 1. The holding unit 2 has an abutted surface on its inner surface against which the abutting surface 12 of the fly-eye lens 1 abuts. With the abutted surface of the holding unit 2 abutting against the abutting surface 12 and the fly-eye lens 1 positioned, the holding unit 2 fixes and holds the fly-eye lens 1 by bonding with an adhesive, fitting, or the like.

[0034] The material of the holder 2 is not particularly limited, and the holder 2 can be made of a material including, for example, a resin material or a metal material. Note that, although Fig. 1 illustrates a configuration in which the holder 2 holds only the fly-eye lens 1, the present invention is not limited to this. The holder 2 may also be configured to integrally hold other members such as the first field lens 3 and the folding mirror 4.

[0035] The total reflection prism 6 is preferably configured as a prism having two or more surfaces, and in this embodiment, is configured as a total reflection triangular prism unit (a so-called TIR prism unit).

[0036] In the above configuration, the total reflection prism 6 causes the illumination light Lr guided via the illumination optical system 50 to be incident on the light modulation element 7 as the incident light Li.

[0037] The light modulation element 7 modulates the incident light Li based on image data. The light modulation element 7 is configured with a DMD having a substantially rectangular mirror surface composed of multiple micromirrors, and processes and reflects the light into an image based on the image data by driving each micromirror in a time-division manner based on the input image data.

[0038] As shown in Fig. 1(c), the light modulation element 7 includes a light modulation region 71, and has a generally rectangular outer shape with its elongated direction along the Y-axis direction in a plan view. A plurality of micromirrors are arranged in a two-dimensional array within the light modulation region 71. In the example shown in Fig. 1(c), the plurality of micromirrors are arranged in a two-dimensional array within the YZ plane.

[0039] The outer shape of the light modulation region 71 is approximately similar to that of each lens 111 in the fly-eye lens 1. The illumination light Lr is a plurality of light beams transmitted through each of the plurality of lenses 111, and the plurality of light beams having an approximately rectangular cross-sectional shape corresponding to the outer shape of each lens 111 are irradiated onto the light modulation region 71 in a superimposed manner.

[0040] The light modulation element 7 reflects the incident light Li by driving each micromirror in a time-division manner, and emits a first outgoing light Lo and a second outgoing light toward the total reflection prism 6.

[0041] The total reflection prism 6 reflects a first outgoing light Lo emitted from the light modulation element 7 in a first direction, and transmits a second outgoing light Lo emitted from the light modulation element 7 in a second direction.

[0042] The first outgoing light Lo reflected by the total reflection prism 6 is guided to the projection optical system 8 as ON light that forms an image based on image data. On the other hand, the second outgoing light emitted in the second direction is treated as OFF light that does not form an image, and is prevented from being re-reflected by being incident on, for example, a mechanical grain or a light absorption band.

[0043] The projection optical system 8 projects the first outgoing light Lo as projection light Lp onto a screen to form an image (an image based on input image data). The screen is configured with a multi-layer array (MLA) or the like.

[0044] [First embodiment] (Example of the fly-eye lens 1 hitting the holding part 2) Next, the abutment of the fly-eye lens 1 in the illumination optical system 50 according to the first embodiment with the holder 2 will be described with reference to Fig. 2. Fig. 2 is a diagram showing an example of the abutment of the fly-eye lens 1 with the holder 2. Fig. 2 is a diagram showing the fly-eye lens 1 in Fig. 1(a) as viewed from the direction of arrow 20, with Fig. 2(a) showing the 0 degree state and Fig. 2(b) showing the 90 degree state.

[0045] 2 are provided on the holding part 2, and are reference surfaces against which the abutting surface 12 of the fly-eye lens 1 abuts, for positioning the fly-eye lens 1. The biasing member P is a member that applies a biasing force in the +Y direction for abutment. Note that the force for abutting in the -X direction is applied by gravity.

[0046] 2(a), the first abutting surface 12a abuts against the first abutted surface 21a, and the second abutting surface 12b abuts against the second abutted surface 21b. In this state, the fly-eye lens 1 is fixed to the holding part 2. Here, the first abutting surface 12a is an example of a predetermined abutting surface.

[0047] The position of the optical function area center 15 in FIG. 2(a) is at a distance Y1 from the first abutted surface 21a in the Y-axis direction, and at a distance X1 from the second abutted surface 21b in the X-axis direction.

[0048] 2(b) shows a state in which the fly-eye lens 1 is rotated 90 degrees clockwise in the XY plane with respect to the state in FIG. 2(a). The XY plane in this case corresponds to the plane including the optical function area 11.

[0049] 2(b), the first abutting surface 12a abuts against the second abutted surface 21b, and the third abutting surface 12c abuts against the first abutted surface 21a. In this state, the fly-eye lens 1 is fixed to the holder 2.

[0050] The position of the optical function area center 15 in FIG. 2(b) is at a distance Y2 from the first abutted surface 21a in the Y-axis direction, and at a distance X2 from the second abutted surface 21b in the X-axis direction.

[0051] In this embodiment, the illumination optical system 50 is configured so that the distance Y1 is approximately equal to the distance Y2, and the distance X1 is approximately equal to the distance X2. In other words, the position of the optical function area center 15 when the fly-eye lens 1 is held in the first state is approximately equal to the position of the optical function area center 15 when the fly-eye lens 1 is held in a second state rotated 90 degrees with respect to the first state within a plane including the optical function area 11.

[0052] Here, the 0 degree state (hereinafter referred to as the 0 degree state) before the fly-eye lens 1 is rotated 90 degrees as shown in FIG. 2(a) is an example of the first state, and the 90 degree state (hereinafter referred to as the 90 degree state) after the fly-eye lens 1 is rotated 90 degrees as shown in FIG. 2(b) is an example of the second state.

[0053] (Function and effect of the illumination optical system 50) Next, the function and effect of the illumination optical system 50 will be described.

[0054] Here, Fig. 3 is a diagram for explaining the operation of the illumination optical system 50. Fig. 3(a) is a diagram showing the overall configuration of the image projection device 10a, Fig. 3(b) is a diagram showing the fly-eye lens 1 in Fig. 3(a) as viewed from the direction of the arrow 20, and Fig. 3(c) is a diagram showing the light modulation element 7a in Fig. 3(a) as viewed from the direction of the arrow 30.

[0055] The image projection device 10a differs from the light modulation element 7 of the image projection device 10 in that the longitudinal direction of the light modulation element 7a is rotated by 90 degrees within the plane (YZ plane) that includes the light modulation region 71a.

[0056] As described above, in this embodiment, the irradiation light Lr is a plurality of light beams that have passed through each of the plurality of lenses 111, and the plurality of light beams having an approximately rectangular cross-sectional shape of each lens 111 are irradiated onto the light modulation region 71a in a superimposed manner.

[0057] If the longitudinal direction of the light modulation element 7a changes, the longitudinal directions of the multiple light beams from the multiple lenses 111 and the light modulation element 7a will no longer match, and the light modulation region 71a of the light modulation element 7a will no longer be properly illuminated by the illumination light Lr.

[0058] Therefore, in order to align the lenses included in the fly-eye lens of the image projection device 10a with the longitudinal direction of the light modulation element 7a, it is preferable that the lenses have an approximately rectangular outer shape with their longitudinal direction along the X-axis when viewed in a plan view, as shown in Figure 3(b).

[0059] However, if a fly-eye lens whose longitudinal direction is oriented along the X-axis direction is prepared separately from the fly-eye lens 1, it will be necessary to redesign the fly-eye lens and to manufacture a new mold for molding the fly-eye lens, which may result in a decrease in development efficiency of the illumination optical system and an increase in costs.

[0060] Therefore, in this embodiment, the fly-eye lens 1 (lens array) includes an optical function area 11 and has a rectangular outer shape in a planar view. In addition, the position of the optical function area center 15 when the fly-eye lens 1 is held in the 0 degree state (first state) is substantially equal to the position of the optical function area center 15 when the fly-eye lens 1 is held in the 90 degree state (second state).

[0061] In this embodiment, the fly-eye lens 1 includes a first abutting surface 12a (predetermined abutting surface) on an end surface. The holding part 2 has an abutted surface 21 against which the abutting surface can abut, and the abutted surface 21 includes a first abutted surface 21a and a second abutted surface 21b perpendicular to the first abutted surface 21a.

[0062] The position of the optical function area center 15 when the first abutting surface 12a is held in abutted state against the first abutted surface 21a is approximately equal to the position of the optical function area center 15 when the first abutting surface 12a is held in abutted state against the second abutted surface 21b.

[0063] In this embodiment, the fly-eye lens 1 includes an abutting surface 12 on an end surface. The holding part 2 has an abutted surface 21 against which the abutting surface 12 can abut. The abutting surface 12 includes a first abutting surface 12a, a second abutting surface 12b perpendicular to the first abutting surface 12a, and a third abutting surface 12c perpendicular to the first abutting surface 12a. The abutted surface 21 includes a first abutted surface 21a and a second abutted surface 21b perpendicular to the first abutted surface 21a.

[0064] In the 0 degree state, the first abutting surface 12a abuts against the first abutted surface 21a, and the second abutting surface 12b abuts against the second abutted surface 21b. In the 90 degree state, the third abutting surface 12c abuts against the first abutted surface 21a, and the first abutting surface 12a abuts against the second abutted surface 21b.

[0065] In this way, even when the light modulation element 7 is changed to a light modulation element 7a whose longitudinal direction is rotated by 90 degrees in the YZ plane, the same type of fly-eye lens 1 can be used by rotating the fly-eye lens 1 by 90 degrees in the XY plane and fixing it to the holder 2. In other words, the same type of fly-eye lens 1 can be used even if the orientation of the light modulation element changes.

[0066] As a result, it is possible to eliminate the need to redesign the fly-eye lens or to manufacture a new mold for molding the fly-eye lens, and thus it is possible to suppress a decrease in development efficiency of the illumination optical system 50 and an increase in costs.

[0067] In the above embodiment, the function of making the position of the optical function area center 15 approximately the same before and after the 90-degree rotation of the fly-eye lens 1 has been described, but various specific configurations for realizing this function are conceivable. These configurations will be described below as modified examples. In the following drawings, the same components as those described in the above embodiment are given the same part numbers, and duplicated descriptions will be omitted as appropriate.

[0068] (First Modification) First, Fig. 4 is a diagram showing a fly-eye lens 1a according to a first modified example of an illumination optical system 50a, Fig. 4(a) shows the 0 degree state, and Fig. 4(b) shows the 90 degree state.

[0069] The fly-eye lens 1a has an outer shape that is square in plan view, and the position of the outer shape center 25 of the fly-eye lens 1a is approximately equal to the position of the optical function area center 15. As a result, the fly-eye lens 1a satisfies the condition of the following formula (1). H / 2+a=V / 2+b (1)

[0070] In addition, in equation (1), V represents the length of the optical function region 11 in a direction parallel to the first abutting surface 12a, a represents the shortest distance from the first abutting surface 12a to the optical function region 11, H represents the length of the optical function region 11 in a direction parallel to the second abutting surface 12b, and b represents the shortest distance from the second abutting surface 12b to the optical function region 11.

[0071] By satisfying formula (1), the position of the optical function area center 15 becomes substantially equal in the 0 degree state and the 90 degree state. As a result, the configuration of the illumination optical system 50a can obtain the same effect as the illumination optical system 50. Note that it is sufficient that the left and right sides of formula (1) are substantially equal.

[0072] (Second Modification) Next, Fig. 5 is a diagram showing a fly-eye lens 1b according to a second modified example of an illumination optical system 50b, Fig. 5(a) shows the 0 degree state, and Fig. 5(b) shows the 90 degree state.

[0073] In the fly-eye lens 1b, the outer shape of the optical function region 11 is square, and the position of the outer center 25 does not coincide with the position of the optical function region center 15. The outer shape of the fly-eye lens 1b may be either square or rectangular.

[0074] With such a fly-eye lens 1b, by satisfying the condition of the above formula (1), the position of the optical function area center 15 becomes substantially equal in the 0 degree state and the 90 degree state. As a result, the configuration of the illumination optical system 50b can provide the same effects as the illumination optical system 50.

[0075] (Third Modification) Next, Fig. 6 is a diagram showing a fly-eye lens 1c according to a third modified example of an illumination optical system 50c, Fig. 6(a) shows the 0 degree state, and Fig. 6(b) shows the 90 degree state.

[0076] The fly-eye lens 1c has a square outer shape and a rectangular outer shape of the optical function area 11. The position of the outer center 25 of the fly-eye lens 1c substantially coincides with the position of the center 15 of the optical function area.

[0077] With such a fly-eye lens 1c, by satisfying the condition of the above formula (1), the position of the optical function area center 15 becomes substantially equal in the 0 degree state and the 90 degree state. As a result, the configuration of the illumination optical system 50c can provide the same effects as the illumination optical system 50.

[0078] (Fourth Modification) Next, Fig. 7 is a diagram showing a fly-eye lens 1d according to a fourth modified example of an illumination optical system 50d, Fig. 7(a) shows the 0 degree state, and Fig. 7(b) shows the 90 degree state.

[0079] In the fly-eye lens 1d, the outer shape of the optical function region 11 is rectangular, and the position of the outer center 25 does not coincide with the position of the optical function region center 15. The outer shape of the fly-eye lens 1d may be either square or rectangular.

[0080] With such a fly-eye lens 1d, by satisfying the condition of the above formula (1), the position of the optical function area center 15 becomes substantially equal in the 0 degree state and the 90 degree state. As a result, the configuration of the illumination optical system 50d can provide the same effects as the illumination optical system 50.

[0081] Here, when the outer shape of the fly-eye lens is rectangular, the distance between the fly-eye lens and the biasing member P changes between the 0 degree state and the 90 degree state, and the biasing force may change.

[0082] Therefore, from the viewpoint of minimizing the difference in conditions and structure between the 0 degree state and the 90 degree state, it is preferable that the outer shape of the fly-eye lens is square. On the other hand, from the viewpoint of minimizing the size of the fly-eye lens or reducing the amount of material used for the fly-eye lens to reduce costs, it is preferable that the outer shape of the fly-eye lens is rectangular.

[0083] [Second embodiment] Next, an illumination optical system 50e according to a second embodiment will be described.

[0084] 8A and 8B are diagrams showing an example of abutment of a fly-eye lens 1e of an illumination optical system 50e against a holder 2e, where Fig. 8(a) shows the 0 degree state and Fig. 8(b) shows the 90 degree state.

[0085] 8, the fly-eye lens 1e includes an abutting surface 12e on an end surface, and the holding part 2e has an abutted surface 21e against which the abutting surface 12e can abut. The abutting surface 12e includes a first abutting surface 12a and a second abutting surface 12b perpendicular to the first abutting surface 12a.

[0086] The abutted surface 21e includes a first abutted surface 21a, a second abutted surface 21b perpendicular to the first abutted surface 21a, and a third abutted surface 21c perpendicular to the second abutted surface 21b.

[0087] That is, the fly's eye lens 1e has two abutting surfaces, and the holding portion 2e has three abutted surfaces.

[0088] In the 0 degree state, the first abutting surface 12a abuts against the first abutted surface 21a, and the second abutting surface 12b abuts against the second abutted surface 21b. In the 90 degree state, the first abutting surface 12a abuts against the second abutted surface 21b, and the second abutting surface 12b abuts against the third abutted surface 21c.

[0089] Moreover, the intermediate position W between the first abutted surface 21a and the third abutted surface 21c is substantially equal to the position of the center 15 of the optical function area.

[0090] Furthermore, the fly-eye lens 1e satisfies the following expressions (2) to (5). V / 2+D=H / 2+B (2) H / 2+B=V / 2+D (3) A+E=B (4) D=C+E (5)

[0091] Here, V represents the length of the optical function region 11 in a direction parallel to the first abutting surface 12a, B represents the shortest distance from the first abutting surface 12a to the optical function region 11, and H represents the length of the optical function region 11 in a direction parallel to the second abutting surface 12b. D represents the shortest distance from the second abutting surface 12b to the optical function region 11, A represents the shortest distance from the end face of the fly-eye lens 1e opposite to the first abutting surface 12a to the optical function region 11, and C represents the shortest distance from the end face of the fly-eye lens 1e opposite to the second abutting surface 12b to the optical function region 11. E represents the distance from the end face of the fly-eye lens 1e opposite to the first abutting surface 12a to the third abutted surface 21c.

[0092] In this way, even in the configuration of the illumination optical system 50e in which the fly-eye lens 1e has two abutment surfaces and the holding portion 2e has three abutted surfaces, it is possible to obtain the same effects as the illumination optical system 50 of the first embodiment.

[0093] That is, even if the light modulation element 7 is changed to a light modulation element 7a whose longitudinal direction is rotated 90 degrees in the YZ plane, the same type of fly-eye lens 1e can be used by rotating the fly-eye lens 1e 90 degrees in the XY plane and fixing it to the holder 2e. In other words, the same type of fly-eye lens 1e can be used even if the orientation of the light modulation element changes.

[0094] As a result, it is possible to eliminate the need to redesign the fly-eye lens or to manufacture a new mold for molding the fly-eye lens, and it is possible to suppress a decrease in development efficiency and an increase in costs for the illumination optical system 50e.

[0095] Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes are possible within the scope of the gist of the embodiments of the present invention described in the claims.

[0096] Furthermore, all numbers such as ordinal numbers and quantities used in the description of the embodiments are merely examples for specifically explaining the technology of the present invention, and the present invention is not limited to the exemplified numbers. [Explanation of symbols]

[0097] 1 Fly-eye lens (an example of a lens array) 1A First fly-eye lens 1B 2nd fly-eye lens 2 Holding part 3 First field lens 4 Folding Mirror 5 Second field lens 6 Total Reflection Prism 7 Light Modulation Element 71 Light Modulation Region 8 Projection optical system 10 Image projection device 11 Optical functional area 111 Lens 12 Abutment surface 12a First abutment surface (an example of a predetermined abutment surface) 12b Second abutment surface 12c 3rd abutment surface 15 Focus on optical function area 21 Abutting surface 21a 1st abutted surface 21b Second abutted surface 21c 3rd abutted surface 25 Fly-eye lens outline center 50 Illumination optical system P biasing member [Prior art documents] [Patent documents]

[0098] [Patent Document 1] JP 2020-187161 A

Claims

1. a lens array that outputs light emitted from a light source toward a light modulation element; a holder for holding the lens array; the lens array includes an optical function area and has a rectangular outer shape in a plan view; An illumination optical system characterized in that the center position of the optical function area when the lens array is held in a first state is equal to the center position of the optical function area when the lens array is held in a second state rotated 90 degrees from the first state within a plane including the optical function area.

2. The lens array includes a predetermined abutment surface on an end surface, The holding portion has an abutted surface against which the predetermined abutting surface can abut, The abutted surface includes a first abutted surface and a second abutted surface perpendicular to the first abutted surface, 2. The illumination optical system according to claim 1, wherein a center position of the optical function area when the specified abutment surface is held in abutted state against the first abutted surface is equal to a center position of the optical function area when the specified abutment surface is held in abutted state against the second abutted surface.

3. The lens array includes an abutment surface at an end surface, The holding portion has an abutted surface against which the abutting surface can abut, The abutment surface includes a first abutment surface, a second abutment surface perpendicular to the first abutment surface, and a third abutment surface perpendicular to the first abutment surface, The abutted surface includes a first abutted surface and a second abutted surface perpendicular to the first abutted surface, In the first state, the first abutting surface abuts against the first abutted surface, and the second abutting surface abuts against the second abutted surface, 3. The illumination optical system according to claim 1, wherein, in the second state, the third abutting surface abuts against the first abutted surface, and the first abutting surface abuts against the second abutted surface.

4. The lens array includes an abutment surface at an end surface, The holding portion has an abutted surface against which the abutting surface can abut, The abutment surface includes a first abutment surface and a second abutment surface perpendicular to the first abutment surface, the abutted surface includes a first abutted surface, a second abutted surface perpendicular to the first abutted surface, and a third abutted surface perpendicular to the second abutted surface, In the first state, the first abutting surface abuts against the first abutted surface, and the second abutting surface abuts against the second abutted surface, 3. The illumination optical system according to claim 1, wherein, in the second state, the first abutting surface abuts against the second abutted surface, and the second abutting surface abuts against the third abutted surface.

5. 5. The illumination optical system according to claim 4, wherein an intermediate position between the first abutted surface and the third abutted surface is equal to a center position of the optically functional area.

6. The optical function area has a rectangular shape in a plan view, The lens array includes an abutment surface at an end surface, The abutment surface includes a first abutment surface and a second abutment surface perpendicular to the first abutment surface, 6. The illumination optical system according to claim 1, wherein the lens array satisfies the following formula (1): H / 2+a=V / 2+b... (1) (V represents the length of the optical function area in a direction parallel to the first abutment surface, a represents the shortest distance from the first abutment surface to the optical function area, H represents the length of the optical function area in a direction parallel to the second abutment surface, and b represents the shortest distance from the second abutment surface to the optical function area.)

7. The optical function area has a rectangular shape in a plan view, 6. The illumination optical system according to claim 4, wherein the lens array satisfies the following expressions (2) to (5): V / 2+D=H / 2+B... (2) H / 2+B=V / 2+D... (3) A+E=B... (4) D=C+E... (5) (V represents the length of the optical function region in a direction parallel to the first abutment surface, B represents the shortest distance from the first abutment surface to the optical function region, H represents the length of the optical function region in a direction parallel to the second abutment surface, D represents the shortest distance from the second abutment surface to the optical function region, A represents the shortest distance from an end face of the lens array opposite to the first abutment surface to the optical function region, C represents the shortest distance from an end face of the lens array opposite to the second abutment surface to the optical function region, and E represents the distance from an end face of the lens array opposite to the first abutment surface to the third abutted surface.)

8. 8. An image projection device comprising an illumination optical system according to claim 1.

Images