Projection optical system and projector

Abstract

A projection optical system and a projector capable of projecting a projection image at a shortest projection distance. The projection optical system has a first optical system and a second optical system disposed on the magnification side of the first optical system. The first optical system has a first lens group having positive refractive power, a second lens group having negative refractive power disposed on the magnification side of the first lens group, and a light path deflecting element disposed between the first lens group and the second lens group. The second optical system has a reflecting member having a concave reflecting surface. The second lens group has three aspherical lenses. F is the focal length of the entire projection optical system, FNO is the F number of the projection optical system, Ymax is the maximum image height in the reduction side conjugate surface, and the following conditional expression (1) is satisfied: 0.25 < |F| × FNO / Ymax < 0.5 … (1).

Description

Technical Field

[0001] This invention relates to projection optical systems and projectors. Background Technology

[0002] Patent Document 1 describes a projector that magnifies a projected image displayed on an image display element and projects it onto a screen using a projection optical system. The projection optical system in this document comprises, from the reduction side to the magnification side, a first refractive optical system, a second refractive optical system, a reflective optical system, and an optical element. The first refractive optical system, the second refractive optical system, and the reflective optical system are arranged in a straight line. The reflective optical system consists of a mirror with a concave reflective surface. The optical element is a transparent parallel plate glass.

[0003] The first refractive optical system, the second refractive optical system, and the reflective optical system are housed within a housing. Optical elements are mounted at openings provided in the housing. Inside the housing, projected light from the image display element side passes through the first and second refractive optical systems and reaches the reflective optical system. The projected light reaching the reflective optical system is reflected back by a concave reflector towards the image display element side and reaches the screen via the opening. The screen is positioned perpendicular to the optical axis of the first refractive optical system.

[0004] In the projector described in this document, when projecting an image onto the screen at the shortest projection distance, the first refractive optical system is located directly below the screen. In other words, in the projector described in this document, when projecting an image onto the screen at the shortest projection distance, the image display element is located behind the screen, and the second refractive optical system and the reflective optical system are located in front of the screen. Therefore, when projecting an image onto the screen at the shortest projection distance, the projector is positioned directly below the screen, and a portion of the housing protrudes rearward beyond the screen.

[0005] Patent Document 1: Japanese Patent Application Publication No. 2018-5253

[0006] The screen is sometimes set along a wall that extends vertically from the ground. When projecting onto this screen, it is impossible for a portion of the projector to protrude behind the screen. Therefore, the projector of Patent Document 1 cannot project an image onto the screen at the shortest possible projection distance. Summary of the Invention

[0007] To address the aforementioned issues, the projection optical system of the present invention, which projects an image from a reduced-side conjugate surface onto a magnified-side conjugate surface, comprises: a first optical system; and a second optical system disposed on the magnified side of the first optical system. The second optical system has a reflecting component having a concave reflecting surface. The first optical system comprises: a first lens group having positive refractive power; a second lens group disposed on the magnified side of the first lens group having negative refractive power; and a deflecting element disposed between the first lens group and the second lens group. The second lens group comprises three aspherical lenses. F is the focal length of the entire projection optical system, FNO is the F-number of the projection optical system, and Ymax is the maximum image height in the reduced-side conjugate surface, satisfying the following condition (1):

[0008] .

[0009] Next, the projector of the present invention includes: a light modulation element disposed on the conjugate surface of the reduced side to modulate light emitted from the light source; and the above-described projection optical system that projects light modulated by the light modulation element. Attached Figure Description

[0010] Figure 1 This is a diagram showing a schematic structure of a projector having the projection optical system of the present invention.

[0011] Figure 2 It is a ray diagram of the projection optical system.

[0012] Figure 3 This is a ray diagram of the projection optical system of Example 1.

[0013] Figure 4 This is a diagram showing the lateral aberrations of the magnified image of the projected optical system at a reference distance.

[0014] Figure 5 This is a diagram showing the grid distortion of the magnified image of the projected optical system at a reference distance.

[0015] Figure 6 This is a ray diagram of the projection optical system in Example 2.

[0016] Figure 7 This is a diagram showing the lateral aberrations of the magnified image of the projected optical system at a reference distance.

[0017] Figure 8 This is a diagram showing the grid distortion of the magnified image of the projected optical system at a reference distance.

[0018] Figure 9 This is a light diagram of the projection optical system in Example 3.

[0019] Figure 10 This is a diagram showing the lateral aberrations of the magnified image of the projected optical system at a reference distance.

[0020] Figure 11 This is a diagram showing the grid distortion of the magnified image of the projected optical system at a reference distance.

[0021] Figure 12 This is a ray diagram of the projection optical system in Example 4.

[0022] Figure 13 This is a diagram showing the lateral aberrations of the magnified image of the projected optical system at a reference distance.

[0023] Figure 14 This is a diagram showing the grid distortion of the magnified image of the projected optical system at a reference distance.

[0024] Label Explanation

[0025] 1: Projector; 2: Image forming unit; 3, 3A, 3B, 3C, 3D: Projection optical system; 4: Control unit; 6: Image processing unit; 7: Display driving unit; 10: Light source; 11: Integrating lens; 12: Integrating lens; 13: Polarization conversion element; 14: Overlapping lens; 15: Dichroic mirror; 16: Reflecting mirror; 17R: Field lens; 17G: Field lens; 17B: Field lens; 18 (18B, 18R, 18G): LCD panel; 19: Cross-shaped dichroic prism; 21: Dichroic mirror; 22: Relay lens; 23: Reflector; 24: Relay lens; 25: Reflector; 30: Intermediate image; 31: First optical system; 32: Second optical system; 33: First lens group; 34: Second lens group; 35: Optical path deflection element; 36: Concave mirror; L1~L17: Lens; N1: First optical axis; N2: Second optical axis; M: Third optical axis; S: Screen. Detailed Implementation

[0026] Hereinafter, the projection optical system and projector according to embodiments of the present invention will be described with reference to the accompanying drawings.

[0027] (Projector)

[0028] Figure 1 This is a diagram showing a schematic structure of a projector having the projection optical system 3 of the present invention. (See diagram for reference.) Figure 1 As shown, the projector 1 includes: an image forming unit 2 that generates a projected image that is projected onto a screen S; a projection optical system 3 that magnifies the projected image and projects a magnified image onto the screen S; and a control unit 4 that controls the operation of the image forming unit 2.

[0029] (Image forming unit and control unit)

[0030] The image forming unit 2 includes a light source 10, a first integrating lens 11, a second integrating lens 12, a polarization conversion element 13, and a superimposed lens 14. The light source 10 is, for example, a high-pressure mercury lamp or a solid-state light source. The first integrating lens 11 and the second integrating lens 12 each have multiple lens elements arranged in an array. The first integrating lens 11 divides the light beam from the light source 10 into multiple segments. Each lens element of the first integrating lens 11 converges the light beam from the light source 10 to the vicinity of each lens element of the second integrating lens 12.

[0031] The polarization conversion element 13 converts the light from the second integrating lens 12 into linearly polarized light. The overlapping lens 14 overlaps the images of each lens element of the first integrating lens 11 on the display areas of the liquid crystal panels 18R, 18G, and 18B, which will be described later, via the second integrating lens 12.

[0032] Additionally, the image forming unit 2 includes a first dichroic mirror 15, a reflector 16, a field lens 17R, and a liquid crystal panel 18R. The first dichroic mirror 15 reflects the red light, which is part of the light incident from the overlapping lens 14, while allowing the G and B light, which are also part of the light incident from the overlapping lens 14, to pass through. The red light reflected by the first dichroic mirror 15 is incident on the liquid crystal panel 18R via the reflector 16 and the field lens 17R. The liquid crystal panel 18R is a light modulation element. The liquid crystal panel 18R modulates the red light according to the image signal, thereby forming a red projected image.

[0033] Furthermore, the image forming unit 2 includes a second dichroic mirror 21, a field lens 17G, and a liquid crystal panel 18G. The second dichroic mirror 21 reflects the G light, which is part of the light from the first dichroic mirror 15, and allows the B light, which is also part of the light from the first dichroic mirror 15, to pass through. The G light reflected by the second dichroic mirror 21 is incident on the liquid crystal panel 18G via the field lens 17G. The liquid crystal panel 18G is a light modulation element. The liquid crystal panel 18G modulates the G light according to the image signal, thereby forming a green projected image.

[0034] Additionally, the image forming unit 2 includes a relay lens 22, a reflector 23, a relay lens 24, a reflector 25, a field lens 17B, a liquid crystal panel 18B, and a cross-shaped dichroic prism 19. B-light, which has passed through the second dichroic mirror 21, is incident on the liquid crystal panel 18B via the relay lens 22, reflector 23, relay lens 24, reflector 25, and field lens 17B. The liquid crystal panel 18B is a light modulation element. The liquid crystal panel 18B modulates the B-light according to the image signal, thereby forming a blue projected image.

[0035] Liquid crystal panels 18R, 18G, and 18B surround the cross-shaped dichroic prism 19 from three directions. The cross-shaped dichroic prism 19 is a prism used for light synthesis, generating a projected image by synthesizing the light modulated by each of the liquid crystal panels 18R, 18G, and 18B.

[0036] The projection optical system 3 magnifies and projects the projection image synthesized by the cross dichroic prism 19 onto the screen S.

[0037] The control unit 4 includes: an image processing unit 6, which receives external image signals such as video signals; and a display driving unit 7, which drives the liquid crystal panel 18R, liquid crystal panel 18G, and liquid crystal panel 18B according to the image signals output from the image processing unit 6.

[0038] The image processing unit 6 converts the image signal input from the external device into image signals of various colors, including grayscale. The display driving unit 7 operates the liquid crystal panels 18R, 18G, and 18B according to the image signals of various colors output from the image processing unit 6. As a result, the image processing unit 6 displays the projected image corresponding to the image signal on the liquid crystal panels 18R, 18G, and 18B.

[0039] (Projection optical system)

[0040] Next, the projection optical system 3 will be described. Figure 2 This is a ray diagram of the projection optical system 3. Furthermore, in Figure 2 In this context, LCD panel 18R, LCD panel 18G, and LCD panel 18B are referred to as LCD panel 18. For example... Figure 2 As shown, a screen S is disposed on the magnification-side conjugate surface of the projection optical system 3. A liquid crystal panel 18 is disposed on the reduction-side conjugate surface of the projection optical system 3.

[0041] In the following explanation, for convenience, the three mutually perpendicular axes are designated as the X-axis, Y-axis, and Z-axis. Furthermore, the width direction of screen S, which serves as the conjugate surface for magnification, is designated as the X-axis, the vertical direction of screen S as the Y-axis, and the direction perpendicular to screen S as the Z-axis. Along the Y-axis, the top of screen S is designated as the Y1 direction, and the bottom of screen S as the Y2 direction. Along the Z-axis, the side of screen S located on is designated as the Z1 direction, and the opposite side as the Z2 direction.

[0042] The projection optical system 3 has a first optical system 31 and a second optical system 32. The first optical system 31 is located in the Z2 direction of the screen. The second optical system 32 is disposed in the Z2 direction of the first optical system 31. The first optical system 31 has a first lens group 33, a second lens group 34 disposed on the magnifying side of the first lens group 33, and a light path deflection element 35 disposed between the first lens group 33 and the second lens group 34. The first lens group 33 has positive refractive power, and the second lens group 34 has negative refractive power. The light path deflection element 35 bends the light path of the projection optical system 3 by 90° between the first lens group 33 and the second lens group 34.

[0043] The first lens group 33 is a refractive optical system. The first optical axis N1 of the first lens group 33 extends along the Y-axis. Each lens in the first lens group 33 has a plane of rotational symmetry centered on the first optical axis N1. The screen S is located in the Z1 direction of the first optical axis N1. The optical path deflection element 35 is a plane mirror. The second lens group 34 is a refractive optical system. The second lens group 34 is located in the Z2 direction of the first optical axis N1. The second optical axis N2 of the second lens group 34 extends along the Z-axis. Each lens L in the second lens group 34 has a plane of rotational symmetry centered on the second optical axis N2. The second lens group 34 has three aspherical lenses. In the second lens group 34, the lens L (the first lens) closest to the magnification side is made of glass.

[0044] The second optical system 32 is a concave mirror 36 (reflective component). The concave mirror 36 has a concave reflecting surface. The concave mirror 36 oriented its reflecting surface toward the Z1 direction. The third optical axis M of the concave mirror 36 is aligned with the second optical axis N2.

[0045] like Figure 2 As shown, the shrinking-side conjugate surface located along the Z-axis on the first optical axis is perpendicular to the magnifying-side conjugate surface. The liquid crystal panel 18, disposed on the shrinking-side conjugate surface, forms a projected image on the Z2 direction side of the first optical axis N1. Light from the liquid crystal panel 18 is deflected by 90° towards the Z2 direction by the light path deflection element 35 after passing through the first lens group 33. Light towards the Z2 direction is then reflected back towards the Z1 and Y1 directions by the concave mirror 36 after passing through the second lens group 34 and reaches the screen S. The screen S is located in the Y1 direction of the second optical axis N2.

[0046] Here, an intermediate image 30, conjugate to both the reduction-side and magnification-side conjugate surfaces, is imaged between the first optical system 31 and the second optical system 32. The intermediate image 30 is formed in the Y2 direction of the second optical axis N2. The intermediate image 30 is a conjugate image that is flipped vertically relative to the magnified image.

[0047] Hereinafter, embodiments 1 to 4 will be described as examples of the structure of the projection optical system 3 mounted on the projector 1.

[0048] (Example 1)

[0049] Figure 3 This is a ray diagram of the projection optical system 3A of Embodiment 1. The projection optical system 3A has a first optical system 31 and a second optical system 32 disposed on the magnification side of the first optical system 31. The first optical system 31 has a first lens group 33, a second lens group 34 disposed on the magnification side of the first lens group 33, and a light path deflection element 35 disposed between the first lens group 33 and the second lens group 34.

[0050] The first lens group 33 has positive refractive power. The first lens group 33 has 10 lenses L1 to L10. Lenses L1 to L10 are arranged sequentially from the reduction side to the magnification side. In this example, lens L2 and lens L3 are a first joint lens L21. Lenses L4 and L5 are a second joint lens L22. Lenses L7 and L8 are a third joint lens L23. An aperture stop O is disposed between lens L8 and lens L9. Lenses L1 to L10 are made of glass. Lenses L1 and L6 are aspherical lenses with aspherical shapes on two surfaces.

[0051] The second lens group 34 has negative refractive power. The second lens group 34 has four lenses L11 to L14. Lenses L11 to L14 are arranged sequentially from the reduction side to the magnification side. In this example, lenses L11, L12, and L13 are aspherical lenses with aspherical shapes on two surfaces. Lenses L11, L12, and L13 are made of resin. Lens L14 (the first lens) is made of glass.

[0052] The optical path deflection element 35 is a plane mirror with a planar reflective surface. In this example, the optical path deflection element 35 does not have refractive power. The optical path deflection element 35 is tilted at 45° relative to the Y-axis and Z-axis.

[0053] The second optical system 32 has a concave mirror 36 with a concave reflective surface. The reflective surface of the concave mirror 36 has an aspherical shape. The third optical axis M of the concave mirror 36 is the designed optical axis. The concave mirror 36 is rotationally symmetrical with respect to the third optical axis M. Light from the first optical system 31 illuminates a region on the reflective surface of the concave mirror 36 that is further along the Y2 direction than the third optical axis M. The concave mirror 36 reflects the light from the first optical system 31 in the Z1 and Y1 directions and reaches the screen S.

[0054] The intermediate image 30 is formed between the second lens group 34 and the concave mirror 36.

[0055] Here, the projection optical system 3A can change the projection distance. When the projection distance is changed, the four lenses L11 to L14 of the second lens group 34 are moved along the second optical axis N2 to focus. During focusing, lenses L12, L13, and L14 move together.

[0056] With the focal length of the entire projection optical system 3A set to F, the F-number of the projection optical system 3A set to FNO, the maximum image height of the liquid crystal panel 18 in the shrinking side conjugate surface set to Ymax, the optical path length from the liquid crystal panel 18 in the shrinking side conjugate surface to the reflecting surface of the concave mirror 36 of the second optical system 32 set to TTL, the length of the first lens group 33 set to Dg1, the focal length of the reflecting surface of the concave mirror 36 of the second optical system 32 set to Fm, the focal length of the lens L14 in the second lens group 34 located at the closest magnification side set to FL1, and the radius of curvature of the surface of the lens L14 located at the closest magnification side in the second lens group 34 facing the shrinking side set to RL1S2, the data of the projection optical system 3A in Embodiment 1 are as follows. Furthermore, the optical path length TTL is the sum of the optical path length along the first optical axis N1 from the liquid crystal panel 18 in the shrinking side conjugate surface to the reflecting surface of the optical path deflection element 35, and the optical path length along the second optical axis N2 from the reflecting surface of the optical path deflection element 35 to the reflecting surface of the concave mirror 36. Additionally, the length Dg1 is the length along the first optical axis N1 from the surface of lens L1 facing the shrinking side to the surface of lens L10 facing the magnifying side.

[0057] |

[0058] The lens data for projection optical system 3A is as follows. Surface numbers are sequentially labeled from the reduction side to the magnification side. These labels correspond to the screen, lenses, dichroic prism, and LCD panel. Surface numbers not corresponding to the screen, lenses, dichroic prism, or LCD panel are fictitious. Surfaces marked with an asterisk (*) are aspherical. R is the radius of curvature. D is the on-axis spacing. nd is the refractive index. νd is the Abbe number. R and D are in mm. Variable spacing 1 is the distance between lenses L10 and L11. Variable spacing 2 is the distance between lenses L11 and L12. Variable spacing 3 is the distance between lens L14 and concave mirror 36. Variable spacing 4 is the distance between concave mirror 36 and screen S, i.e., the projection distance.

[0059]

[0060] In this example, the projection optical system 3A allows the projection distance to vary between a reference distance, a near distance (shorter than the reference distance), and a far distance (far greater than the reference distance). At the reference distance, the variable interval 4 is 342.29 mm. At the near distance, the variable interval 4 is 275.00 mm. At the far distance, the variable interval 4 is 442.61 mm. When the projection distance is varied from the reference distance, lens L11 of the second lens group 34 is moved to focus. This changes the variable interval 1. Furthermore, when the projection distance is varied, lenses L12, L13, and L14 of the second lens group 34 are moved together to focus. This changes the variable intervals 2 and 3. The relationship between variable intervals 1, 2, 3, and 4 is as follows.

[0061]

[0062] The aspherical coefficients are as follows.

[0063]

[0064]

[0065]

[0066] (Effects)

[0067] The projection optical system 3A in this example has a first optical system 31 and a second optical system 32 disposed on the magnifying side of the first optical system 31. The first optical system 31 has: a first lens group 33, which has positive refractive power; a second lens group 34, which is disposed on the magnifying side of the first lens group 33; and a light path deflection element 35, which is disposed between the first lens group 33 and the second lens group 34. The second optical system 32 has a concave mirror 36 with a concave reflecting surface. The second lens group 34 has negative refractive power. In addition, the second lens group 34 has three aspherical lenses. Assuming that the focal length of the entire projection optical system 3A is F, the F number of the projection optical system 3A is FNO, and the maximum image height in the conjugate plane on the reducing side is Ymax, the following conditional expression (1) is satisfied.

[0068]

[0069] In the projection optical system 3A of this example, the first optical system 31 has a light path deflection element 35 between the first lens group 33 and the second lens group 34. Therefore, the first optical system 31 can be bent between the first lens group 33 and the second lens group 34. Thus, compared to the case where the lenses of the first lens group 33 and the lenses of the second lens group 34 of the first optical system 31 are arranged along a linearly extending optical axis, the reduction-side conjugate surface can be positioned closer to the second optical system 32. Therefore, when a projected image is projected onto the screen S by the projector 1 having the projection optical system 3A of this example, the liquid crystal panel 18, which forms the projected image on the reduction-side conjugate surface, can be prevented from being located behind the screen S. Therefore, for example, even if the screen S is arranged along a wall extending vertically from the ground, it is possible to project onto the screen S by the projector 1.

[0070] Furthermore, in the projection optical system 3A of this example, the second lens group 34 has three aspherical lenses. Therefore, it is possible to suppress the generation of aberrations in the conjugate surface on the magnification side.

[0071] Furthermore, the projection optical system 3A in this example satisfies condition (1), thus suppressing the enlargement of the projection optical system 3A. In addition, the projection optical system 3A in this example satisfies condition (1), thus suppressing the generation of aberrations and enabling the imaging of a bright magnified image on the magnified side conjugate surface.

[0072] That is, in this example,

[0073]

[0074] therefore,

[0075] |

[0076] Here, when the value of condition (1) is below the lower limit, the magnified image becomes brighter, but it is difficult to correct aberrations well. When the value of condition (1) exceeds the upper limit, aberrations can be corrected well, but the magnified image becomes darker and the projection optical system becomes larger.

[0077] Furthermore, in this example, the first optical system 31 has a light path deflection element 35 between the first lens group 33 and the second lens group 34, thus allowing the first optical system 31 to bend between the first lens group 33 and the second lens group 34. Therefore, the arrangement of the first lens group 33 and the second lens group 34 in the first optical system 31 has a degree of freedom. Thus, when light passing through the first optical system 31 from the conjugate surface side of the reduced side is reflected by the concave mirror 36 of the second optical system 32, interference between the reflected light and the lenses of the second lens group 34 can be avoided. Therefore, it is not necessary to provide a cutout portion in the lenses of the second lens group 34 to avoid interference with the light reflected by the concave mirror 36. Therefore, in this example, each lens of the second lens group 34 can have a plane of rotational symmetry centered on the second optical axis N2 of the second lens group 34. Furthermore, if each lens of the second lens group 34 has a plane of rotational symmetry centered on the second optical axis N2, the manufacture of each lens of the second lens group 34 becomes easier. Furthermore, the lenses of the second lens group 34 can be configured with high precision.

[0078] In addition, in this example, when the optical path length from the liquid crystal panel 18 in the conjugate surface of the reduced side to the reflective surface of the concave mirror 36 is TTL and the length of the first lens group 33 is Dg1, the following condition (2) is satisfied.

[0079]

[0080] That is, in this example,

[0081]

[0082] therefore,

[0083]

[0084] The projection optical system 3A satisfies condition (2), thus it can suppress the enlargement of the entire projection optical system 3A and suppress the aberrations of the magnified image. That is, when the value of condition (2) is below the lower limit, the projection optical system 3A can be miniaturized, but the lenses required to correct the aberrations of the magnified image cannot be adequately configured in the projection optical system 3A. As a result, it is difficult to suppress the aberrations of the magnified image. When the value of condition (2) exceeds the upper limit, the lenses required to correct the aberrations of the magnified image can be adequately configured in the projection optical system 3A, thus the aberrations of the magnified image can be well corrected, but the projection optical system 3A becomes enlarged. In addition, the length of the first lens group 33 is the distance on the optical axis from the reduction-side lens surface of the lens closest to the reduction side of each lens constituting the first lens group 33 to the magnification-side lens surface of the lens closest to the magnification side.

[0085] In this example, the first lens group 33 has an aspherical lens. Therefore, it is easier to correct various aberrations.

[0086] Next, the projection optical system 3A in this example forms an intermediate image 30 conjugate to both the reduction-side conjugate surface and the magnification-side conjugate surface between the first optical system 31 and the second optical system 32. Therefore, the projection optical system 3A has three aspherical lenses in the second lens group 34 near the intermediate image 30. This allows for the suppression of aberrations in the intermediate image 30, and thus facilitates the suppression of aberrations in the magnification-side conjugate surface.

[0087] Furthermore, in this example, the lens L14, located on the magnification side in the second lens group 34, is made of glass. Therefore, compared to the case where the lens L14 is made of resin, chromatic aberration is easier to correct.

[0088] Furthermore, in this example, the reflecting surface of the concave mirror 36 is an aspherical surface. Assuming the focal length of the reflecting surface of the concave mirror 36 is Fm, the following condition (3) is satisfied.

[0089]

[0090] That is, in this example,

[0091] |

[0092] therefore,

[0093]

[0094] In this example, the projection optical system 3A satisfies condition (3), therefore the refractive power of the reflecting surface of the concave mirror 36, which has the function of magnifying the projected intermediate image 30, is within an appropriate range. That is, when the value of condition (3) is below the lower limit, the projection distance can be shortened, but the aberrations generated by the reflecting surface of the concave mirror 36 increase, making it difficult to obtain a good magnified image.

[0095] In addition, in this example, if the focal length of the lens L14, which is closest to the magnification side in the second lens group 34, is FL1, the following condition (4) is satisfied.

[0096]

[0097] That is, in this example,

[0098]

[0099] therefore,

[0100]

[0101] The projection optical system 3A in this example satisfies condition (4), thus suppressing the enlargement of the entire projection optical system 3A and suppressing the generation of aberrations in the intermediate image 30 located on the magnification side of lens L14. That is, when the value of condition (4) is below the lower limit, the refractive power of lens L14 becomes too strong, making it difficult to correct aberrations in the intermediate image 30. When the value of condition (4) exceeds the upper limit, the refractive power of lens L14 becomes too weak. As a result, the refractive power of lenses L11 to L13 in the second lens group 34 increases, making it easier to generate aberrations.

[0102] Furthermore, in this example, if the radius of curvature of the lens surface facing the reduction side of the lens L14 located on the magnification side in the second lens group 34 is RL1S2, the following condition (5) is satisfied:

[0103] .

[0104] That is, in this example,

[0105]

[0106] therefore,

[0107]

[0108] The projection optical system 3A in this example satisfies condition (5), thus enabling the intermediate image 30 to be imaged in the appropriate position and obtaining a well-corrected magnified image. That is, when the value of condition (5) is below the lower limit, the intermediate image 30 is too close to the second lens group 34. In addition, when the value of condition (5) exceeds the upper limit, the intermediate image 30 is too close to the concave mirror 36. In these cases, there is a possibility that dust or dirt attached to the lens L14 and the concave mirror 36 may be imaged on the conjugate surface on the magnification side, but since condition (5) is satisfied, such a situation can be avoided.

[0109] Figure 4 This is a diagram showing the lateral aberration of the magnified image of a projection optical system 3A with a variable interval of 4 as the reference distance. Figure 5 This is a diagram showing the grid distortion of a magnified image of a projection optical system 3A with a variable interval of 4 as the reference distance. (See diagram for example.) Figure 4 and Figure 5 As shown, the projection optics system 3A in this example suppresses lateral aberrations and grid distortion in the magnified image.

[0110] (Example 2)

[0111] Figure 6This is a ray diagram of the projection optical system 3B of Embodiment 2. The projection optical system 3B has a first optical system 31 and a second optical system 32 disposed on the magnification side of the first optical system 31. The first optical system 31 has a first lens group 33, a second lens group 34 disposed on the magnification side of the first lens group 33, and a light path deflection element 35 disposed between the first lens group 33 and the second lens group 34.

[0112] The first lens group 33 has positive refractive power. The first lens group 33 has 10 lenses L1 to L10. Lenses L1 to L10 are arranged sequentially from the reduction side to the magnification side. In this example, lens L2 and lens L3 are a first joint lens L21. Lenses L4 and L5 are a second joint lens L22. Lenses L7 and L8 are a third joint lens L23. An aperture stop O is disposed between lens L8 and lens L9. Lenses L1 to L10 are made of glass. Lenses L1 and L6 are aspherical lenses with aspherical shapes on two surfaces.

[0113] The second lens group 34 has negative refractive power. The second lens group 34 has six lenses L11 to L16. Lenses L11 to L16 are arranged sequentially from the reduction side to the magnification side. In this example, lenses L12 and L13 are combined to form a fourth combined lens L24. Lenses L11, L14, and L15 are aspherical lenses with aspherical shapes on two surfaces. Lenses L11, L14, and L15 are made of resin. Lenses L12, L13, and L16 (the first lens) are made of glass.

[0114] The optical path deflection element 35 is a plane mirror with a planar reflective surface. In this example, the optical path deflection element 35 does not have refractive power. The optical path deflection element 35 is tilted at 45° relative to the Y-axis and Z-axis.

[0115] The second optical system 32 has a concave mirror 36 with a concave reflective surface. The reflective surface of the concave mirror 36 has an aspherical shape. The third optical axis M of the concave mirror 36 is the designed optical axis. The concave mirror 36 is rotationally symmetrical with respect to the third optical axis M. Light from the first optical system 31 illuminates a region on the reflective surface of the concave mirror 36 that is further along the Y2 direction than the third optical axis M. The concave mirror 36 reflects the light from the first optical system 31 in the Z1 and Y2 directions and reaches the screen S.

[0116] The intermediate image 30 is formed between the second lens group 34 and the concave mirror 36.

[0117] Here, the projection optical system 3B can change the projection distance. When the projection distance is changed, the six lenses L11 to L16 of the second lens group 34 are moved along the second optical axis N2 to focus. During focusing, lenses L11, L12, and L13 move together, and lenses L14, L15, and L16 move together.

[0118] With the focal length of the entire projection optical system 3B set to F, the F-number of the projection optical system 3B set to FNO, the maximum image height of the liquid crystal panel 18 in the shrinking side conjugate surface set to Ymax, the optical path length from the liquid crystal panel 18 in the shrinking side conjugate surface to the reflecting surface of the concave mirror 36 of the second optical system 32 set to TTL, the length of the first lens group 33 set to Dg1, the focal length of the reflecting surface of the concave mirror 36 of the second optical system 32 set to Fm, the focal length of the lens L16 in the second lens group 34 located at the closest magnification side set to FL1, and the radius of curvature of the surface of the lens L16 located at the closest magnification side in the second lens group 34 facing the shrinking side set to RL1S2, the data of the projection optical system 3B of Embodiment 2 are as follows. Furthermore, the optical path length TTL is the sum of the optical path length along the first optical axis N1 from the liquid crystal panel 18 in the shrinking side conjugate surface to the reflecting surface of the optical path deflection element 35, and the optical path length along the second optical axis N2 from the reflecting surface of the optical path deflection element 35 to the reflecting surface of the concave mirror 36. Additionally, the length Dg1 is the length along the first optical axis N1 from the surface of lens L1 facing the shrinking side to the surface of lens L10 facing the magnifying side.

[0119]

[0120] The lens data for projection optical system 3B is as follows. Surface numbers are sequentially labeled from the reduction side to the magnification side. These labels correspond to the screen, lenses, dichroic prism, and LCD panel. Surface numbers not corresponding to the screen, lenses, dichroic prism, or LCD panel are fictitious. Surfaces marked with an asterisk (*) are aspherical. R is the radius of curvature. D is the on-axis spacing. nd is the refractive index. νd is the Abbe number. R and D are in mm. Variable spacing 1 is the distance between lenses L10 and L11. Variable spacing 2 is the distance between lenses L13 and L14. Variable spacing 3 is the distance between lens L16 and concave mirror 36. Variable spacing 4 is the distance between concave mirror 36 and screen S, i.e., the projection distance.

[0121]

[0122] In this example, the projection optical system 3B allows the projection distance to vary between a reference distance, a near distance (shorter than the reference distance), and a far distance (far greater than the reference distance). At the reference distance, the variable interval 4 is 425.30 mm. At the near distance, the variable interval 4 is 327.53 mm. At the far distance, the variable interval 4 is 503.56 mm. When the projection distance is varied from the reference distance, lenses L11, L12, and L13 of the second lens group 34 are moved together for focusing. This changes the variable interval 1. Furthermore, when the projection distance is varied, lenses L14, L15, and L16 of the second lens group 34 are moved together for focusing. This changes the variable intervals 2 and 3. The relationship between variable intervals 1, 2, 3, and 4 is as follows.

[0123]

[0124] The aspherical coefficients are as follows.

[0125]

[0126]

[0127]

[0128] Here, in this example, when the focal length of the entire projection optical system 3B is set to F, the F number of the projection optical system 3B is FNO, and the maximum image height in the conjugate plane on the reduced side is Ymax, the following condition (1) is satisfied.

[0129]

[0130] In this example,

[0131]

[0132] therefore,

[0133]

[0134] In addition, in this example, when the optical path length from the liquid crystal panel 18 in the conjugate surface of the reduced side to the reflective surface of the concave mirror 36 is set to TTL and the length of the first lens group 33 is Dg1, the following condition (2) is satisfied.

[0135]

[0136] In this example,

[0137]

[0138] therefore,

[0139]

[0140] In addition, in this example, when the focal length of the reflecting surface of the concave mirror 36 is Fm, the following condition (3) is satisfied.

[0141]

[0142] In this example,

[0143]

[0144] therefore,

[0145]

[0146] In addition, in this example, when the focal length of the lens L16 located on the magnification side in the second lens group 34 is FL1, the following condition (4) is satisfied.

[0147]

[0148] In this example,

[0149]

[0150] therefore,

[0151]

[0152] Furthermore, in this example, when the radius of curvature of the surface of the lens L16, which is located closest to the magnification side in the second lens group 34, facing the reduction side is RL1S2, the following condition (5) is satisfied:

[0153] .

[0154] In this example,

[0155]

[0156] therefore,

[0157]

[0158] (Effects)

[0159] The projection optical system 3B in this example can achieve the same effect as the projection optical system 3A in Example 1. Figure 7 This is a diagram showing the lateral aberration of the magnified image of a projection optical system 3B with a variable interval of 4 as the reference distance. Figure 8 This is a diagram showing the grid distortion of a magnified image of a projection optical system 3B with a variable interval of 4 as the reference distance. (See diagram for example.) Figure 7 and Figure 8 As shown, the projection optics system 3B in this example suppresses lateral aberrations and grid distortion in the magnified image.

[0160] (Example 3)

[0161] Figure 9 This is a ray diagram of the projection optical system 3C of Embodiment 3. The projection optical system 3C has a first optical system 31 and a second optical system 32 disposed on the magnification side of the first optical system 31. The first optical system 31 has a first lens group 33, a second lens group 34 disposed on the magnification side of the first lens group 33, and a light path deflection element 35 disposed between the first lens group 33 and the second lens group 34.

[0162] The first lens group 33 has positive refractive power. The first lens group 33 has 11 lenses L1 to L11. Lenses L1 to L11 are arranged sequentially from the reduction side to the magnification side. In this example, lenses L3 and L4 are a first joint lens L21. Lenses L5 and L6 are a second joint lens L22. Lenses L8 and L9 are a third joint lens L23. An aperture stop O is disposed between lens L9 and lens L10. Lenses L1 to L11 are made of glass. Lens L7 is an aspherical lens with aspherical shapes on both surfaces.

[0163] The second lens group 34 has negative refractive power. The second lens group 34 has six lenses L12 to L17. Lenses L12 to L17 are arranged sequentially from the reduction side to the magnification side. In this example, lenses L13 and L14 are combined to form a fourth combined lens L24. Lenses L12, L15, and L16 are aspherical lenses with aspherical shapes on two surfaces. Lenses L12, L15, and L16 are made of resin. Lenses L13, L14, and L17 (the first lens) are made of glass.

[0164] The optical path deflection element 35 is a plane mirror with a planar reflective surface. In this example, the optical path deflection element 35 does not have refractive power. The optical path deflection element 35 is tilted at 45° relative to the Y-axis and Z-axis.

[0165] The second optical system 32 has a concave mirror 36 with a concave reflective surface. The reflective surface of the concave mirror 36 has an aspherical shape. The third optical axis M of the concave mirror 36 is the designed optical axis. The concave mirror 36 is rotationally symmetrical with respect to the third optical axis M. Light from the first optical system 31 illuminates a region on the reflective surface of the concave mirror 36 that is further along the Y2 direction than the third optical axis M. The concave mirror 36 reflects the light from the first optical system 31 in the Z1 and Y2 directions and reaches the screen S.

[0166] The intermediate image 30 is formed between the second lens group 34 and the concave mirror 36.

[0167] Here, the projection optical system 3C can change the projection distance. When the projection distance is changed, the six lenses L12 to L17 of the second lens group 34 are moved along the second optical axis N2 to focus. During focusing, lenses L13 to L17 move together.

[0168] With the focal length of the entire projection optical system 3C set to F, the F-number of the projection optical system 3C set to FNO, the maximum image height of the liquid crystal panel 18 in the shrinking side conjugate surface set to Ymax, the optical path length from the liquid crystal panel 18 in the shrinking side conjugate surface to the reflecting surface of the concave mirror 36 of the second optical system 32 set to TTL, the length of the first lens group 33 set to Dg1, the focal length of the reflecting surface of the concave mirror 36 of the second optical system 32 set to Fm, the focal length of the lens L17 in the second lens group 34 located at the closest magnification side set to FL1, and the radius of curvature of the surface of the lens L17 located at the closest magnification side in the second lens group 34 facing the shrinking side set to RL1S2, the data of the projection optical system 3C in Embodiment 3 are as follows. Furthermore, the optical path length TTL is the sum of the optical path length along the first optical axis N1 from the liquid crystal panel 18 in the shrinking side conjugate surface to the reflecting surface of the optical path deflection element 35, and the optical path length along the second optical axis N2 from the reflecting surface of the optical path deflection element 35 to the reflecting surface of the concave mirror 36. Additionally, the length Dg1 is the length along the first optical axis N1 from the surface of lens L1 facing the shrinking side to the surface of lens L11 facing the magnifying side.

[0169]

[0170] The lens data for the 3C projection optical system is as follows. Surface numbers are sequentially labeled from the reduction side to the magnification side. These labels correspond to the screen, lens, dichroic prism, and LCD panel. Surface numbers not corresponding to the screen, lens, dichroic prism, or LCD panel are fictitious. Surfaces marked with an asterisk (*) are aspherical. R is the radius of curvature. D is the on-axis spacing. nd is the refractive index. νd is the Abbe number. R and D are in mm. Variable spacing 1 is the distance between lens L11 and lens L12. Variable spacing 2 is the distance between lens L12 and lens L13. Variable spacing 3 is the distance between lens L17 and concave mirror 36. Variable spacing 4 is the distance between concave mirror 36 and screen S, i.e., the projection distance.

[0171]

[0172]

[0173] In this example, the projection optical system 3C allows the projection distance to vary between a reference distance, a near distance (shorter than the reference distance), and a far distance (far greater than the reference distance). At the reference distance, the variable interval 4 is 411.80 mm. At the near distance, the variable interval 4 is 336.50 mm. At the far distance, the variable interval 4 is 599.54 mm. When the projection distance is varied from the reference distance, lens L12 of the second lens group 34 is moved for focusing. This changes the variable interval 1. Furthermore, when the projection distance is varied, lenses L13 to L17 of the second lens group 34 are moved together for focusing. This changes the variable interval 2 and variable interval 3. The relationship between variable interval 1, variable interval 2, variable interval 3, and variable interval 4 is as follows.

[0174]

[0175] The aspherical coefficients are as follows.

[0176]

[0177]

[0178] The above table shows the lens, dichroic prism, and LCD panel.

[0179] Here, in this example, when the focal length of the entire projection optical system 3C is F, the F number of the projection optical system 3C is FNO, and the maximum image height in the conjugate plane on the reduced side is Ymax, the following condition (1) is satisfied.

[0180]

[0181] In this example,

[0182]

[0183] therefore,

[0184]

[0185] In addition, in this example, when the optical path length from the liquid crystal panel 18 in the conjugate surface of the reduced side to the reflective surface of the concave mirror 36 is TTL and the length of the first lens group 33 is Dg1, the following condition (2) is satisfied.

[0186]

[0187] In this example,

[0188]

[0189] therefore,

[0190]

[0191] In addition, in this example, when the focal length of the reflecting surface of the concave mirror 36 is Fm, the following condition (3) is satisfied.

[0192]

[0193] In this example,

[0194]

[0195] therefore,

[0196]

[0197] In addition, in this example, when the focal length of the lens L17 located on the magnification side in the second lens group 34 is FL1, the following condition (4) is satisfied.

[0198]

[0199] In this example,

[0200]

[0201] therefore,

[0202]

[0203] Furthermore, in this example, when the radius of curvature of the surface of the lens L17, which is located closest to the magnification side in the second lens group 34, facing the reduction side is set to RL1S2, the following condition (5) is satisfied:

[0204] .

[0205] In this example,

[0206]

[0207] therefore,

[0208]

[0209] (Effects)

[0210] The projection optical system 3C in this example can achieve the same effect as the projection optical system 3A in Example 1. Figure 10 This is a diagram showing the lateral aberration of the magnified image of a projection optical system 3C with a variable interval of 4 as the reference distance. Figure 11 This is a diagram showing the grid distortion of a magnified image of a projection optical system 3C with a variable interval of 4 as the reference distance. (See diagram for example.) Figure 10 and Figure 11 As shown, the projection optics system 3C in this example suppresses lateral aberrations and grid distortion in the magnified image.

[0211] (Example 4)

[0212] Figure 12 This is a ray diagram of the projection optical system 3D of Embodiment 4. The projection optical system 3D has a first optical system 31 and a second optical system 32 disposed on the magnification side of the first optical system 31. The first optical system 31 has a first lens group 33, a second lens group 34 disposed on the magnification side of the first lens group 33, and a light path deflection element 35 disposed between the first lens group 33 and the second lens group 34.

[0213] The first lens group 33 has positive refractive power. The first lens group 33 has 11 lenses L1 to L11. Lenses L1 to L11 are arranged sequentially from the reduction side to the magnification side. In this example, lenses L3 and L4 are a first joint lens L21. Lenses L5 and L6 are a second joint lens L22. Lenses L8 and L9 are a third joint lens L23. An aperture stop O is disposed between lens L9 and lens L10. Lenses L1 to L11 are made of glass. Lens L7 is an aspherical lens with aspherical shapes on both surfaces.

[0214] The second lens group 34 has negative refractive power. The second lens group 34 has six lenses L12 to L17. Lenses L12 to L17 are arranged sequentially from the reduction side to the magnification side. In this example, lenses L13 and L14 are combined to form a fourth combined lens L24. Lenses L12, L15, and L16 are aspherical lenses with aspherical shapes on two surfaces. Lenses L12, L15, and L16 are made of resin. Lenses L13, L14, and L17 (the first lens) are made of glass.

[0215] The optical path deflection element 35 is a plane mirror with a planar reflective surface. In this example, the optical path deflection element 35 does not have refractive power. The optical path deflection element 35 is tilted at 45° relative to the Y-axis and Z-axis.

[0216] The second optical system 32 has a concave mirror 36 with a concave reflective surface. The reflective surface of the concave mirror 36 has an aspherical shape. The third optical axis M of the concave mirror 36 is the designed optical axis. The concave mirror 36 is rotationally symmetrical with respect to the third optical axis M. Light from the first optical system 31 illuminates a region on the reflective surface of the concave mirror 36 that is further along the Y2 direction than the third optical axis M. The concave mirror 36 reflects the light from the first optical system 31 in the Z1 and Y2 directions and reaches the screen S.

[0217] The intermediate image 30 is formed between the second lens group 34 and the concave mirror 36.

[0218] Here, the projection optical system 3D can change the projection distance. When the projection distance is changed, the six lenses L12 to L17 of the second lens group 34 are moved along the second optical axis N2 to focus. During focusing, lenses L13 to L17 move together.

[0219] Furthermore, the projection optical system 3D can zoom the magnified image. Zooming is achieved by moving the two lenses L10 and L11 of the first lens group 33 along the first optical axis N1. In this example, the magnified image becomes 1.04 times through zooming.

[0220] With the focal length of the entire projection optical system 3D set to F, the F-number of the projection optical system 3D set to FNO, the maximum image height of the liquid crystal panel 18 in the shrinking side conjugate surface set to Ymax, the optical path length from the liquid crystal panel 18 in the shrinking side conjugate surface to the reflecting surface of the concave mirror 36 of the second optical system 32 set to TTL, the length of the first lens group 33 set to Dg1, the focal length of the reflecting surface of the concave mirror 36 of the second optical system 32 set to Fm, the focal length of the lens L17 in the second lens group 34 located at the closest magnification side set to FL1, and the radius of curvature of the surface of the lens L17 in the second lens group 34 located at the closest magnification side facing the shrinking side set to RL1S2, the data of the projection optical system 3D in Embodiment 4 are as follows. Furthermore, the optical path length TTL is the sum of the optical path length along the first optical axis N1 from the liquid crystal panel 18 in the shrinking side conjugate surface to the reflecting surface of the optical path deflection element 35, and the optical path length along the second optical axis N2 from the reflecting surface of the optical path deflection element 35 to the reflecting surface of the concave mirror 36. Additionally, the length Dg1 is the length along the first optical axis N1 from the surface of lens L1 facing the shrinking side to the surface of lens L11 facing the magnifying side.

[0221]

[0222] The lens data for the 3D projection optical system is as follows. Surface numbers are sequentially labeled from the reduced side to the magnified side. The labels correspond to the screen, lenses, dichroic prism, and LCD panel. Surface numbers not corresponding to the screen, lenses, dichroic prism, or LCD panel are fictitious. Surfaces marked with an asterisk (*) are aspherical. R is the radius of curvature. D is the on-axis spacing. nd is the refractive index. νd is the Abbe number. R and D are in mm. Variable spacing 1 is the distance between the aperture stop O and lens L10. Variable spacing 2 is the distance between lens L10 and lens L11. Variable spacing 3 is the distance between lens L11 and the optical path deflection element 35. Variable spacing 4 is the distance between the optical path deflection element 35 and lens L12. Variable spacing 5 is the distance between lens L12 and lens L13. Variable spacing 6 is the distance between lens L17 and concave mirror 36. Variable spacing 7 is the distance between concave mirror 36 and screen S, i.e., the projection distance.

[0223]

[0224]

[0225] In this example, the projection optical system 3D allows the projection distance to vary between a reference distance, a near distance (shorter than the reference distance), and a far distance (far greater than the reference distance). At the reference distance, the variable interval 7 is 411.80 mm. At the near distance, the variable interval 7 is 336.30 mm. At the far distance, the variable interval 7 is 6000.83 mm. When the projection distance is varied from the reference distance, lens L12 of the second lens group 34 is moved to focus. This changes the variable interval 4. Furthermore, when the projection distance is varied, lenses L13 to L17 of the second lens group 34 are moved together to focus. This changes the variable intervals 5 and 6. The relationship between variable interval 1, variable interval 2, variable interval 3, variable interval 4, variable interval 5, variable interval 6, and variable interval 7 is as follows.

[0226]

[0227] Furthermore, the variable intervals 1, 2, 3, 4, 5, 6, and 7 when zooming are performed are as follows. When zooming, lens L10 of the first lens group 33 is moved. This changes the variable interval 1. Also, when zooming, lens L11 of the first lens group 33 is moved. This changes the variable intervals 2 and 3. Only the case where the variable interval 7 is set to 432.39 mm as the reference distance is shown.

[0228]

[0229] The aspherical coefficients are as follows.

[0230]

[0231]

[0232]

[0233] Here, in this example, when the focal length of the entire projection optical system 3D is F, the F number of the projection optical system 3D is FNO, and the maximum image height in the conjugate plane on the reduced side is Ymax, the following condition (1) is satisfied.

[0234]

[0235] In this example,

[0236]

[0237] therefore,

[0238]

[0239] In addition, in this example, when the optical path length from the liquid crystal panel 18 in the conjugate surface of the reduced side to the reflective surface of the concave mirror 36 is set to TTL and the length of the first lens group 33 is Dg1, the following condition (2) is satisfied.

[0240]

[0241] In this example,

[0242]

[0243] therefore,

[0244]

[0245] In addition, in this example, when the focal length of the reflecting surface of the concave mirror 36 is Fm, the following condition (3) is satisfied.

[0246]

[0247] In this example,

[0248]

[0249] therefore,

[0250]

[0251] In addition, in this example, when the focal length of the lens L17 located on the magnification side in the second lens group 34 is FL1, the following condition (4) is satisfied.

[0252]

[0253] In this example,

[0254]

[0255] therefore,

[0256]

[0257] Furthermore, in this example, when the radius of curvature of the surface of the lens L17, which is located closest to the magnification side in the second lens group 34, facing the reduction side is set to RL1S2, the following condition (5) is satisfied:

[0258] .

[0259] In this example,

[0260]

[0261] therefore,

[0262]

[0263] (Effects)

[0264] The projection optical system 3D in this example can achieve the same effect as the projection optical system 3A in Example 1. Figure 13 This is a diagram showing the lateral aberrations of a magnified 3D image of a projection optical system with a variable interval of 7 as the reference distance. Figure 14 This is a diagram showing the mesh distortion of a magnified 3D image of a projection optical system with a variable interval of 7 as the reference distance. (See diagram for example.) Figure 13 and Figure 14 As shown, the projection optics system in this example 3D suppresses lateral aberrations and grid distortion in the magnified image.

[0265] (Other embodiments)

[0266] In the above embodiment, the optical path deflection element 35 bends the optical path of the projection optical system by 90° between the first lens group 33 and the second lens group 34, but is not limited to this. For example, the bending angle can also be 45° or 120°. As long as the optical path between the first lens group 33 and the second lens group 34 can be bent by the optical path deflection element 35, compared with the case where the lenses of the first lens group and the lenses of the second lens group of the first optical system are arranged along a straight optical axis, the reduction-side conjugate surface can be placed on the side closer to the second optical system.

Claims

1. A projection optical system, characterized in that, Project the image of the reduced-side conjugate surface onto the magnified-side conjugate surface. The projection optical system has: First optical system; and The second optical system is configured on the magnification side of the first optical system. The first optical system comprises: a first lens group having positive refractive power; and a second lens group disposed on the magnifying side of the first lens group having negative refractive power. And an optical path deflection element, which is disposed between the first lens group and the second lens group. The second optical system has a reflective component with a concave reflective surface. The second lens group has three aspherical lenses. F is the focal length of the entire projection optical system, FNO is the F-number of the projection optical system, and Ymax is the maximum image height in the conjugate plane on the reduced side, satisfying the following condition (1): ， An intermediate image is formed between the first optical system and the second optical system. This intermediate image is conjugate with both the reduction-side conjugate surface and the magnification-side conjugate surface. The reflecting surface is aspherical. Fm is the focal length of the reflecting surface, satisfying the following condition (3): 。 2. A projection optical system, characterized in that, Project the image of the reduced-side conjugate surface onto the magnified-side conjugate surface. The projection optical system has: First optical system; and The second optical system is configured on the magnification side of the first optical system. The first optical system comprises: a first lens group having positive refractive power; and a second lens group disposed on the magnifying side of the first lens group having negative refractive power. And an optical path deflection element, which is disposed between the first lens group and the second lens group. The second optical system has a reflective component with a concave reflective surface. The second lens group has three aspherical lenses. F is the focal length of the entire projection optical system, FNO is the F-number of the projection optical system, and Ymax is the maximum image height in the conjugate plane on the reduced side, satisfying the following condition (1): ， An intermediate image is formed between the first optical system and the second optical system. This intermediate image is conjugate with both the reduction-side conjugate surface and the magnification-side conjugate surface. FL1 is the focal length of the first lens in the second lens group located on the magnification side, satisfying the following condition (4): 。 3. A projection optical system, characterized in that, Project the image of the reduced-side conjugate surface onto the magnified-side conjugate surface. The projection optical system has: First optical system; and The second optical system is configured on the magnification side of the first optical system. The first optical system comprises: a first lens group having positive refractive power; and a second lens group disposed on the magnifying side of the first lens group having negative refractive power. And an optical path deflection element, which is disposed between the first lens group and the second lens group. The second optical system has a reflective component with a concave reflective surface. The second lens group has three aspherical lenses. F is the focal length of the entire projection optical system, FNO is the F-number of the projection optical system, and Ymax is the maximum image height in the conjugate plane on the reduced side, satisfying the following condition (1): ， An intermediate image is formed between the first optical system and the second optical system. This intermediate image is conjugate with both the reduction-side conjugate surface and the magnification-side conjugate surface. RL1S2 is the radius of curvature of the surface of the first lens, which is located closest to the magnification side in the second lens group, facing the reduction side, and satisfies the following condition (5): 。 4. The projection optical system according to any one of claims 1 to 3, characterized in that, The three aspherical lenses of the second lens group each have a rotational symmetry plane centered on the optical axis of the second lens group.

5. The projection optical system according to any one of claims 1 to 3, characterized in that, TTL is the optical path length from the conjugate surface on the reduced side to the reflecting surface, and Dg1 is the length of the first lens group, satisfying the following condition (2): 。 6. The projection optical system according to any one of claims 1 to 3, characterized in that, The first lens group has an aspherical lens.

7. The projection optical system according to any one of claims 1 to 3, characterized in that, The first lens in the second lens group, located on the side closest to the magnification, is made of glass.

8. The projection optical system according to claim 2 or 3, characterized in that, The reflecting surface is aspherical. Fm is the focal length of the reflecting surface, satisfying the following condition (3): 。 9. The projection optical system according to claim 3, characterized in that, FL1 is the focal length of the first lens in the second lens group located on the magnification side, satisfying the following condition (4): 。 10. A projector, characterized in that, The projector has: An optical modulation element, disposed on the conjugate surface of the reduced side, modulates the light emitted from the light source; as well as The projection optical system according to any one of claims 1 to 9, wherein the projection optical system projects light modulated by the light modulation element.

Images