Optical system and image projection device

Abstract

An optical system according to the present disclosure has a reduction conjugate point on a reduction side and an enlargement conjugate point on an enlargement side. Said optical system comprises a first optical subsystem and a second optical subsystem disposed in that order from the enlargement side to the reduction side, with the first optical subsystem and the second optical subsystem each including a plurality of lenses. Defining an axis that passes through the center of the pluralities of lenses as an optical axis, a luminous flux incident on a first lens most on the reduction side of the second optical subsystem at a position closest to the optical axis as a first luminous flux, and a luminous flux incident on the first lens at a position furthest from the optical axis as a second luminous flux, a main light beam of the second luminous flux intersects with the optical axis at a first intersection point within the second optical subsystem and intersects with the optical axis at a second intersection point more on the enlargement side than the first optical subsystem.

Description

Optical system and image projection apparatus

[0001] The present disclosure relates to an optical system. The present disclosure also relates to an image projection apparatus using such an optical system.

[0002] Patent Document 1 discloses a projection optical system that includes, in order from the projection surface side, an aperture stop, a first lens having positive refractive power, a second lens having negative refractive power, a third lens having positive refractive power, a fourth lens having positive refractive power, and a polarization separation element.

[0003] Japanese Unexamined Patent Application Publication No. 2012-27420

[0004] The present disclosure provides an optical system capable of achieving a wider angle in an optical system for projecting light by passing the light through an aperture provided on the magnification side. The present disclosure also provides an image projection apparatus using such an optical system.

[0005] An optical system according to one aspect of the present disclosure is an optical system having a reduction conjugate point on the reduction side and a magnification conjugate point on the magnification side, the optical system comprising a first sub-optical system and a second sub-optical system arranged in order from the magnification side to the reduction side, each of the first sub-optical system and the second sub-optical system includes a plurality of lenses, an axis passing through centers of the plurality of lenses is defined as an optical axis, a light beam incident on a most reduction-side first lens of the second sub-optical system at a position closest to the optical axis is defined as a first light beam, and a light beam incident on the first lens at a position farthest from the optical axis is defined as a second light beam, a chief ray of the second light beam intersects the optical axis at a first intersection point in the second sub-optical system, and intersects the optical axis at a second intersection point located on the magnification side relative to the first sub-optical system.

[0006] Further, an image projection apparatus according to the present disclosure includes the above-described optical system, and an image forming element that generates an image to be projected onto a screen via the optical system.

[0007] According to the present disclosure, a wider angle can be achieved in an optical system for projecting light by passing the light through an aperture provided on the magnification side.

[0008] 3. 3. 4. 5. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 14. 15. 16. 17. 18. 17. 18. 19. 18. 19. 10. 18. 19

[0009] The embodiments will be described in detail below, with reference to the drawings as appropriate. However, unnecessarily detailed explanations may be omitted. For example, detailed explanations of already well-known matters or redundant explanations of substantially identical configurations may be omitted. This is to avoid the following explanation becoming unnecessarily verbose and to facilitate understanding for those skilled in the art.

[0010] The applicant provides the accompanying drawings and the following description so that a person skilled in the art can fully understand the disclosure, and not to limit the subject matter described in the claims.

[0011] Furthermore, in this specification, terms such as "first," "second," etc., are used solely for descriptive purposes and should not be understood as expressing or implying relative importance or ranking of technical features. Features designated as "first" and "second" express or imply that they include one or more such features.

[0012] The following describes various embodiments of the optical system according to this disclosure. In each embodiment, the case in which the optical system is used in a projector (an example of an image projection device) that projects image light of an original image, obtained by spatially modulating incident light with an image forming element such as a liquid crystal or a DMD (digital micromirror device) based on an image signal, onto a screen will be described. That is, the optical system according to this disclosure can be used to project an enlarged original image on an image forming element located on the reduction side onto a screen, by placing the screen on the extension of the enlargement side.

[0013] (Embodiment 1) Hereinafter, Embodiment 1 of the present disclosure will be described with reference to Figures 1 to 19.

[0014] Figures 1, 9, 12, and 15 are arrangement diagrams showing the optical system 1 of Examples 1 to 4, respectively. In each figure, the image formation position on the magnification side (i.e., the magnification conjugate point) is located on the left, and the image formation position on the reduction side (i.e., the reduction conjugate point) is located on the right. Each figure shows the arrangement diagram of the optical system 1 as viewed from a direction perpendicular to the Y-Z plane (meridional plane), with the optical axis OA in the Z direction in the X-Y-Z Cartesian coordinate system. Figure 18 is an arrangement diagram showing the optical system 1 of Example 5. In Figure 18, the image formation position on the magnification side (i.e., the magnification conjugate point) is located on the upper side, and the image formation position on the reduction side (i.e., the reduction conjugate point) is located on the right. In Figure 18, the arrangement diagram of the optical system 1 as viewed from a direction perpendicular to the Y-Z plane (meridional plane), with the optical axis OA1 in the Y direction and the optical axis OA2 in the Z direction in the X-Y-Z Cartesian coordinate system.

[0015] In each figure, the straight line drawn on the smallest side represents the position of the original image S1, and the optical elements P1 to P3 are located on the enlarged side of the original image S1. Optical elements P1 to P3 represent optical elements such as TIR (total internal reflection) prisms, prisms for color separation and color synthesis, optical filters, parallel plate glass, quartz low-pass filters, and infrared cut filters. Optical elements P1 to P3 have two parallel and flat transmission surfaces.

[0016] The optical system 1 of Examples 1 to 5 is an optical system for projecting light through an aperture K1 provided on the magnification side. The optical system 1 comprises, in order from the magnification side to the reduction side, an aperture material A1, a first sub-optical system OP1, and a second sub-optical system OP2. Furthermore, the optical system 1 of Examples 1 to 5 has an intermediate imaging element MI inside that is conjugate to the magnification conjugate point on the magnification side and the reduction conjugate point on the reduction side.

[0017] In the optical systems 1 of Examples 1 to 5, examples in which the aperture material A1 is included as a component of the optical system 1 will be described, but the aperture material A1 does not necessarily have to be included as a component of the optical system 1.

[0018] The opening member A1 is a member provided with an opening K1. For example, the opening member A1 is a plate-shaped member, and the opening K1 is a hole that penetrates the plate-shaped member in the thickness direction. The opening K1 has a circular shape.

[0019] The first sub-optical system OP1 includes multiple lenses. The first sub-optical system OP1 is located on the reduction side of the aperture material A1 and on the expansion side of the intermediate imaging MI.

[0020] The second sub-optical system OP2 includes a plurality of lenses. In Example 5, the second sub-optical system OP2 includes a reflective optical element Mir between two of the plurality of lenses. The second sub-optical system OP2 is located on the reduced side of the first sub-optical system OP1 and on the reduced side of the intermediate imaging MI.

[0021] In the optical systems 1 of Examples 1 to 4, the optical axis OA is defined as the axis passing through the centers of the multiple lenses in the first sub-optical system OP1 and the second sub-optical system OP2. In the optical system 1 of Example 5, the optical axis OA1 is defined as the axis passing through the centers of the multiple lenses on the magnifying side of the reflective optical element Mir in the first sub-optical system OP1 and the second sub-optical system OP2, and the optical axis OA2 is defined as the axis passing through the centers of the multiple lenses on the reducing side of the reflective optical element Mir in the second sub-optical system OP2. The multiple lenses are rotationally symmetric with respect to optical axes OA, OA1, and OA2. Furthermore, the center of the aperture K1 of the aperture material A1 is located on the optical axis OA.

[0022] In optical system 1 of Examples 1 to 5, the light beam incident on the lens on the most reduced side of the second sub-optical system OP2 at the position closest to the optical axes OA and OA2 is defined as the first light beam, and the light beam incident on the lens on the most reduced side of the second sub-optical system OP2 at the position furthest from the optical axes OA and OA2 is defined as the second light beam. The principal ray of the second light beam intersects the optical axis OA at the first intersection within the second sub-optical system OP2, and intersects the optical axes OA and OA1 at the second intersection on the enlargement side of the first sub-optical system OP1.

[0023] The first and second luminous beams are projected onto a screen or the like through the aperture K1 of the aperture material A1, which is located on the enlarged side of the first sub-optical system OP1.

[0024] Figures 2, 10, 13, 16, and 19 are explanatory diagrams showing the usage of the image projection device using the optical system 1 of Examples 1 to 5. The image projection device including the optical system 1 projects light onto a screen SC through an aperture K1 provided on the magnification side. The screen SC is installed at a relatively short horizontal distance from the aperture K1. The screen SC is a single plane located at the conjugate point on the magnification side. The light generated from the optical system 1 is projected forward, achieving short-focus and large-screen projection.

[0025] Figures 3, 11, 14, and 17 are transverse aberration diagrams for the optical systems 1 of Examples 1 to 4, respectively. Figure 11 is also a transverse aberration diagram for the optical system 1 of Example 5. In each figure, (A), (B), (C), (D), and (E) show the transverse aberration diagrams of the tangential (meridional) plane and sagittal plane at positions shifted from the center in the Y direction, respectively.

[0026] (Example 1) Figure 1 is a layout diagram showing the optical system 1 according to Example 1. The surface data for Example 1 is shown in the numerical example 1 described later.

[0027] In Example 1, the first sub-optical system OP1 includes a plurality of lenses L1 to L4.

[0028] In the first sub-optical system OP1, multiple lenses L1 to L4 are arranged in order from the magnification side to the reduction side. Lens L1 has a biconvex shape. Lens L2 has a negative meniscus shape with its convex surface facing the reduction side. Lens L3 has a positive meniscus shape with its convex surface facing the reduction side. Lens L4 has a biconvex shape.

[0029] The second sub-optical system OP2 includes multiple lenses L5 to L14 and an aperture ST.

[0030] In the second sub-optical system OP2, multiple lenses L5 to L14 are arranged in order from the magnification side to the reduction side. Lens L5 has a biconcave shape. Lens L6 has a positive meniscus shape with its convex surface facing the reduction side. Lens L7 has a biconvex shape. Lens L8 has a biconcave shape. Lens L9 has a negative meniscus shape with its convex surface facing the reduction side. Lens L10 has a positive meniscus shape with its convex surface facing the magnification side. Lens L11 has a biconvex shape. Lens L12 has a biconcave shape. Lens L13 has a biconvex shape. Lens L14 has a biconvex shape.

[0031] The aperture ST is located between lens L9 and lens L10.

[0032] The intermediate image formation MI is formed between lens L4 and lens L5.

[0033] The principal ray of the second luminous beam intersects the optical axis OA near the aperture ST in the second sub-optical system OP2, and intersects the optical axis OA on the magnified side of lens L1 in the first sub-optical system OP1.

[0034] (Example 2) Figure 9 is a layout diagram showing the optical system 1 according to Example 2. The surface data for Example 2 is shown in the numerical example 2 described later.

[0035] In Example 2, the first sub-optical system OP1 includes a plurality of lenses L1 to L5.

[0036] In the first sub-optical system OP1, multiple lenses L1 to L5 are arranged in order from the magnification side to the reduction side. Lens L1 has a biconvex shape. Lens L2 has a negative meniscus shape with its convex surface facing the reduction side. Lens L3 has a positive meniscus shape with its convex surface facing the reduction side. Lens L4 has a positive meniscus shape with its convex surface facing the reduction side. Lens L5 has a biconvex shape.

[0037] The second sub-optical system OP2 includes multiple lenses L6 to L16 and an aperture ST.

[0038] In the second sub-optical system OP2, multiple lenses L6 to L16 are arranged in order from the magnification side to the reduction side. Lens L6 has a biconcave shape. Lens L7 has a positive meniscus shape with its convex surface facing the reduction side. Lens L8 has a positive meniscus shape with its convex surface facing the reduction side. Lens L9 has a negative meniscus shape with its convex surface facing the reduction side. Lens L10 has a positive meniscus shape with its convex surface facing the reduction side. Lens L11 has a biconvex shape. Lens L12 has a negative meniscus shape with its convex surface facing the magnification side. Lens L13 has a biconvex shape. Lens L14 has a biconcave shape. Lens L15 has a biconvex shape. Lens L16 has a biconvex shape.

[0039] The aperture ST is located between lens L11 and lens L12.

[0040] The intermediate image formation MI is formed between lens L5 and lens L6.

[0041] The second luminous beam intersects the optical axis OA near the aperture ST in the second sub-optical system OP2, and intersects the optical axis OA on the magnification side of lens L1 in the first sub-optical system OP1.

[0042] (Example 3) Figure 12 is a layout diagram showing the optical system 1 according to Example 3. The surface data for Example 3 is shown in the numerical example 3 described later.

[0043] In Example 3, the first sub-optical system OP1 includes a plurality of lenses L1 to L4.

[0044] In the first sub-optical system OP1, a plurality of lenses L1 to L4 are arranged in order from the magnification side to the reduction side. The lens L1 has a biconvex shape. The lens L2 has a negative meniscus shape with a convex surface facing the reduction side. The lens L3 has a positive meniscus shape with a convex surface facing the reduction side. The lens L4 has a biconvex shape.

[0045] The second sub-optical system OP2 includes a plurality of lenses L5 to L14 and a stop ST.

[0046] In the second sub-optical system OP2, a plurality of lenses L5 to L14 are arranged in order from the magnification side to the reduction side. The lens L5 has a biconcave shape. The lens L6 has a positive meniscus shape with a convex surface facing the reduction side. The lens L7 has a biconvex shape. The lens L8 has a biconcave shape. The lens L9 has a negative meniscus shape with a convex surface facing the reduction side. The lens L10 has a positive meniscus shape with a convex surface facing the magnification side. The lens L11 has a biconvex shape. The lens L12 has a biconcave shape. The lens L13 has a biconvex shape. The lens L14 has a biconvex shape.

[0047] The stop ST is arranged between the lens L9 and the lens L10.

[0048] An intermediate image MI is formed between the lens L4 and the lens L5.

[0049] The second light beam intersects the optical axis OA near the stop ST in the second sub-optical system OP2, and intersects the optical axis OA on the magnification side relative to the lens L1 of the first sub-optical system OP1.

[0050] (Example 4) FIG. 15 is an arrangement diagram showing an optical system 1 according to Example 4. Note that surface data of Example 4 is shown in Numerical Example 4 described later.

[0051] In Example 4, the first sub-optical system OP1 includes a plurality of lenses L1 to L5.

[0052] In the first sub-optical system OP1, multiple lenses L1 to L5 are arranged in order from the magnification side to the reduction side. Lens L1 has a biconvex shape. Lens L2 has a negative meniscus shape with its convex surface facing the reduction side. Lens L3 has a positive meniscus shape with its convex surface facing the reduction side. Lens L4 has a positive meniscus shape with its convex surface facing the reduction side. Lens L5 has a biconvex shape.

[0053] The second sub-optical system OP2 includes multiple lenses L6 to L16 and an aperture ST.

[0054] In the second sub-optical system OP2, multiple lenses L6 to L16 are arranged in order from the magnification side to the reduction side. Lens L6 has a biconcave shape. Lens L7 has a positive meniscus shape with its convex surface facing the reduction side. Lens L8 has a positive meniscus shape with its convex surface facing the reduction side. Lens L9 has a negative meniscus shape with its convex surface facing the reduction side. Lens L10 has a positive meniscus shape with its convex surface facing the reduction side. Lens L11 has a biconvex shape. Lens L12 has a negative meniscus shape with its convex surface facing the magnification side. Lens L13 has a biconvex shape. Lens L14 has a biconcave shape. Lens L15 has a biconvex shape. Lens L16 has a biconvex shape.

[0055] The aperture ST is located between lens L11 and lens L12.

[0056] The intermediate image formation MI is formed between lens L5 and lens L6.

[0057] The second luminous beam intersects the optical axis OA near the aperture ST in the second sub-optical system OP2, and intersects the optical axis OA on the magnified side of the lens L1 of the first sub-optical system OP1. (Example 5) Figure 18 is a layout diagram showing the optical system 1 according to Example 5. The surface data for Example 5 is equivalent to that of the numerical Example 2 described later.

[0058] In Example 5, the first sub-optical system OP1 includes a plurality of lenses L1 to L5.

[0059] In the first sub-optical system OP1, multiple lenses L1 to L5 are arranged in order from the magnification side to the reduction side. Lens L1 has a biconvex shape. Lens L2 has a negative meniscus shape with its convex surface facing the reduction side. Lens L3 has a positive meniscus shape with its convex surface facing the reduction side. Lens L4 has a positive meniscus shape with its convex surface facing the reduction side. Lens L5 has a biconvex shape.

[0060] The second sub-optical system OP2 includes multiple lenses L6 to L16 and a reflective optical element Mir.

[0061] In the second sub-optical system OP2, a plurality of lenses L6 to L8, a reflective optical element Mir, and a plurality of lenses L9 to L16 are arranged in order from the magnification side to the reduction side. Lens L6 has a biconcave shape. Lens L7 has a positive meniscus shape with its convex surface facing the reduction side. Lens L8 has a positive meniscus shape with its convex surface facing the reduction side. The reflective optical element Mir has a flat reflective surface and a reflective surface that bends light rays in the 90-degree direction. The reflective optical element Mir is, for example, a mirror. Lens L9 has a negative meniscus shape with its convex surface facing the reduction side. Lens L10 has a positive meniscus shape with its convex surface facing the reduction side. Lens L11 has a biconvex shape. Lens L12 has a negative meniscus shape with its convex surface facing the magnification side. Lens L13 has a biconvex shape. Lens L14 has a biconcave shape. Lens L15 has a biconvex shape. Lens L16 has a biconvex shape.

[0062] The aperture ST is located between lens L11 and lens L12.

[0063] The intermediate image formation MI is formed between lens L5 and lens L6.

[0064] The second luminous beam intersects the optical axis OA2 near the aperture ST in the second sub-optical system OP2, and intersects the optical axis OA1 on the magnification side of the lens L1 in the first sub-optical system OP1.

[0065] Thus, the optical system 1 according to this disclosure has the characteristic that, when the light beam incident on the lens on the most compact side of the second sub-optical system OP2 at the position closest to the optical axes OA and OA2 is defined as the first light beam, and the light beam incident on the lens on the most compact side of the second sub-optical system OP2 at the position furthest from the optical axes OA and OA2 is defined as the second light beam, the principal rays of the second light beam intersect with the optical axes OA and OA2 at a first intersection within the second sub-optical system OP2, and intersect with the optical axes OA and OA1 at a second intersection on the magnifying side of the first sub-optical system OP1. Due to this characteristic, the optical system for projecting light by passing it through an aperture K1 provided on the magnifying side can be widened. Furthermore, the dimensions of the aperture K1 can be reduced. That is, the optical system 1 according to this disclosure can achieve a wide angle while reducing the dimensions of the aperture K1. In addition, the optical system 1 according to this disclosure can also shorten the distance between the screen SC and the optical system 1, thus enabling miniaturization of the optical system 1.

[0066] Next, the conditions that the optical system 1 according to this disclosure can satisfy will be explained. Note that multiple conditions are defined for the optical system 1 according to each embodiment, and it is possible to satisfy all of these conditions, or to satisfy individual conditions to obtain the corresponding effects.

[0067] Referring to Figures 1, 9, 12, 15, and 18, in the optical system 1 of this disclosure, an intermediate imaging MI conjugate to the reduction conjugate point and the expansion conjugate point is formed between the first sub-optical system OP1 and the second sub-optical system OP2.

[0068] This configuration allows for wider angle of view and improved aberration correction.

[0069] In the optical system 1 of this disclosure, the image height at the intermediate imaging MI is greater than the image height at the reduced conjugate point.

[0070] This configuration allows for an even wider angle of view.

[0071] In the optical system 1 of this disclosure, the intermediate imaging MI is formed at a position closer to the lens on the widest side of the first sub-optical system OP1 than to the lens on the narrowest side of the second sub-optical system OP2.

[0072] This configuration allows for an even wider angle of view.

[0073] The optical system 1 according to this disclosure satisfies the following condition (1): 0.5 < f2 / f1 < 0.9 ... (1) where, f1: focal length of the first sub-optical system OP1 f2: focal length of the second sub-optical system OP2.

[0074] This configuration allows for a wider angle of view while miniaturizing the optical system 1.

[0075] The optical system 1 according to this disclosure satisfies the following condition (2): 1.0 < D1 / f < 2.6 ... (2) where, D1: diameter of the image circle of the optical system 1, and f: focal length of the optical system 1.

[0076] Now, with reference to Figure 4, we will explain the image circle IS.

[0077] The image circle IS is a circle centered on the optical axis OA, drawn by the second luminous beam, which is the luminous beam furthest from the optical axis OA at the conjugate point on the reduction side. Image forming elements DM1, such as liquid crystal or DMD, are arranged to fit within the image circle IS.

[0078] Condition (2) specifies the ratio of the focal length f1 of the entire optical system 1 to the diameter D1 of the image circle IS. By satisfying condition (2), it is possible to achieve both wide-angle and optical performance.

[0079] Referring to Figures 1, 9, 12, 15, and 18, in the optical system 1 of the present disclosure, the first sub-optical system OP1 has at least three positive lenses and one negative lens, and one or more of the three positive lenses and one negative lens are aspherical lenses.

[0080] This configuration allows for a wider angle of view while maintaining optical performance.

[0081] Referring to Figures 1, 9, 12, 15, and 18, in the optical system 1 of this disclosure, the second sub-optical system OP2 has an aperture ST, and the first light beam and the second light beam intersect at the position of the aperture ST.

[0082] With this configuration, stray light can be cut off by the aperture ST at the point where the first and second light beams intersect.

[0083] In the optical system 1 according to this disclosure, the region where the light beam is distributed at the second intersection on the enlarged side of the first sub-optical system OP1 is smaller than the aperture region of the aperture ST.

[0084] Here, with reference to Figures 5 and 6, the region where the luminous beam is distributed at the second intersection will be described. Figure 5 shows the ray coordinates of the image forming element in Example 1. Figure 6 shows the footprint of each ray at the second intersection where aperture K1 is located, that is, the range of light beam reach (luminous beam distribution region) BA in the cross section cut in the X-Y plane at the second intersection. Also, in Figure 6, the aperture region of aperture ST is shown by a dashed line for reference. The footprints shown in Figure 6 were obtained using the image forming element in Figure 5.

[0085] As shown in Figure 6, when viewed from the direction of the optical axis OA (Z-axis direction), the luminous flux distribution region BA at the second intersection is smaller than the aperture region of the aperture ST.

[0086] This configuration allows for a wider angle while simultaneously reducing the aperture K1.

[0087] Referring to Figures 2, 10, 13, 16, and 19, the optical system 1 according to this disclosure satisfies the following condition (3): 30 ≤ θ1 < 51 ... (3) where θ1 is the angle between the principal ray of the second luminous beam and the optical axis OA at the second intersection.

[0088] This configuration allows for a wider angle of view.

[0089] Referring to Figures 1, 9, 12, 15, and 18, the optical system 1 of the present disclosure is positioned on the enlarged side of the first sub-optical system OP1 and comprises an aperture member A1 having an aperture K1, the aperture K1 being located on the optical axis OA.

[0090] This configuration allows for a wider angle while simultaneously reducing the aperture K1.

[0091] Referring to Figures 1, 9, 12, 15, and 18, in the optical system 1 of this disclosure, the aperture material A1 is positioned at the second intersection.

[0092] This configuration allows the opening K1 to be made even smaller.

[0093] The optical system 1 of this disclosure satisfies the following condition (4): D2 ≤ DL1 / 3 ... (4) where, D2: Maximum dimension of aperture K1 of aperture material A1 DL1: The effective lens diameter of the lens with the largest effective lens diameter among the multiple lenses of the first sub-optical system OP1 and the second sub-optical system OP2.

[0094] Here, the maximum dimensions of the aperture K1 will be explained with reference to Figures 7 and 8. Figure 7 shows an example of a circular aperture K1, and Figure 8 shows an example of an elongated aperture K1. In Figures 7 and 8, the effective diameter of the lens with the largest effective diameter among the lenses of the first sub-optical system OP1 and the second sub-optical system OP2 is indicated by a dashed line.

[0095] In the example shown in Figure 7, the opening K1 is circular in shape with a center C1. Therefore, the maximum dimension D2 of the opening K1 is equal to the diameter of the opening K1.

[0096] In the example shown in Figure 8, the opening K1 is an elongated hole with a center C1. Therefore, the maximum dimension D2 of the opening K1 is the longitudinal dimension of the opening K1. The longitudinal dimension is the length of the longest straight line drawn through the center C1 within the opening K1.

[0097] The shape of the opening K1 is not limited to the examples described above, and may be any shape, such as a rectangular shape, a polygonal shape, or an elliptical shape.

[0098] (Numerical Example 1) For the optical system of Numerical Example 1 (corresponding to Example 1), the surface data is shown in Table 1, and the aspherical shape data of the lens is shown in Table 2.

[0099]

[0100]

[0101] (Numerical Example 2) For the optical system of Numerical Example 2 (corresponding to Examples 2 and 5), the surface data is shown in Table 3, and the aspherical data of the lenses is shown in Table 4. Although not shown in the surface data in Table 3, in Example 5, a reflective optical element Mir with a flat reflective surface is placed between lens L8 and lens L9.

[0102]

[0103]

[0104] (Numerical Example 3) For the optical system of Numerical Example 3 (corresponding to Example 3), the surface data is shown in Table 5, and the aspherical shape data of the lens is shown in Table 6.

[0105]

[0106]

[0107] (Numerical Example 4) For the optical system of Numerical Example 4 (corresponding to Example 4), the surface data is shown in Table 7, and the aspherical shape data of the lens is shown in Table 8.

[0108]

[0109]

[0110] Table 9 shows the conditions in optical system 1 for numerical examples 1 to 4 (corresponding to examples 1 to 4).

[0111]

[0112] (Embodiment 2) Hereinafter, Embodiment 2 of the present disclosure will be described with reference to Figure 20. Figure 20 is a block diagram showing an example of an image projection device according to the present disclosure. The image projection device 100 includes the optical system 1 disclosed in Embodiment 1, an image forming element 101, a light source 102, a control unit 110, etc. The image forming element 101 is composed of liquid crystal, DMD, etc., and generates an image to be projected onto the screen SC via the optical system 1. The light source 102 is composed of an LED (light-emitting diode), a laser, etc., and supplies light to the image forming element 101. The control unit 110 is composed of a CPU or MPU, etc., and controls the entire device and each component. The optical system 1 may be configured as an interchangeable lens that can be detachably attached to the image projection device 100. In this case, the device obtained by removing the optical system 1 from the image projection device 100 is an example of the main device.

[0113] The image projection device 100 described above can achieve both wide-angle projection and miniaturization using the optical system 1 according to Embodiment 1.

[0114] (Embodiment 3) Hereinafter, Embodiment 3 of the present disclosure will be described with reference to Figure 21. Figure 21 is a block diagram showing an example of an imaging device according to the present disclosure. The imaging device 200 includes the optical system 1 disclosed in Embodiment 1, an image sensor 201, a control unit 210, etc. The image sensor 201 is composed of a CCD (charge-coupled device) image sensor, a CMOS image sensor, etc., and receives the optical image of an object OBJ formed by the optical system 1 and converts it into an electrical image signal. The control unit 110 is composed of a CPU or MPU, etc., and controls the entire device and each component. The optical system 1 may be configured as an interchangeable lens that can be detachably attached to the imaging device 200. In this case, the device obtained by removing the optical system 1 from the imaging device 200 is an example of the main device.

[0115] The imaging device 200 described above can achieve both wide-angle and miniaturization using the optical system 1 according to Embodiment 1.

[0116] As described above, embodiments have been explained as part of the technical disclosure in this disclosure. For this purpose, accompanying drawings and a detailed description have been provided.

[0117] Therefore, the components described in the attached drawings and detailed descriptions may include not only components essential for solving the problem, but also components that are not essential for solving the problem, provided that they illustrate the technology described above. For this reason, the mere presence of such non-essential components in the attached drawings or detailed descriptions should not be immediately assumed to mean that these non-essential components are essential.

[0118] Furthermore, since the embodiments described above are for illustrative purposes of the technology described herein, various modifications, substitutions, additions, omissions, etc., can be made within the scope of the claims or their equivalents.

[0119] This disclosure is applicable to image projection devices such as projectors and head-up displays, and imaging devices such as digital still cameras, digital video cameras, surveillance cameras in surveillance systems, webcams, and in-vehicle cameras. In particular, this disclosure is applicable to the optical systems of projectors, digital still camera systems, and digital video camera systems.

[0120] 1 Optical system 100 Image projection device 101 Image forming element 102 Light source 110 Control unit L1-L16 Lens A1 Aperture material BA Light beam distribution area C1 Center D1 Diameter D2 Maximum dimension DL1 Effective lens diameter K1 Aperture MI Intermediate imaging OA, OA1, OA2 Optical axis OP1 First sub-optical system OP2 Second sub-optical system IS Image circle P1-P3 Optical element ST Aperture S1 Original image SC Screen

Claims

1. An optical system having a reduction conjugate point on the reduction side and an expansion conjugate point on the expansion side, comprising a first sub-optical system and a second sub-optical system arranged sequentially from the expansion side to the reduction side, wherein each of the first sub-optical system and the second sub-optical system includes a plurality of lenses, and the axis passing through the centers of the plurality of lenses is defined as the optical axis, and the light beam incident on the first lens on the most reduction side of the second sub-optical system at the position closest to the optical axis is defined as the first light beam, and the light beam incident on the first lens at the position furthest from the optical axis is defined as the second light beam, wherein the principal ray of the second light beam intersects the optical axis at a first intersection in the second sub-optical system and intersects the optical axis at a second intersection on the expansion side of the first sub-optical system.

2. The optical system according to claim 1, wherein an intermediate image conjugate to the reduced conjugate point and the enlarged conjugate point is formed between the first sub-optical system and the second sub-optical system.

3. The optical system according to claim 2, wherein the image height at the intermediate image formation is greater than the image height at the reduced conjugate point.

4. The optical system according to claim 2, wherein the intermediate image is formed at a position closer to the second lens on the most magnified side of the first sub-optical system than to the first lens of the second sub-optical system.

5. The optical system according to claim 2, satisfying the following condition (1): 0.5 < f2 / f1 < 0.9 ... (1) where, f1: focal length of the first sub-optical system f2: focal length of the second sub-optical system.

6. The optical system according to claim 2, satisfying the following condition (2): 1.1 < D1 / f < 2.6 ... (2) where, D1: diameter of the image circle of the optical system f: focal length of the optical system.

7. The optical system according to claim 1, wherein the first sub-optical system has at least three positive lenses and one negative lens, and one or more of the three positive lenses and the one negative lens are aspherical lenses.

8. The optical system according to claim 1, wherein the second sub-optical system has an aperture, and the first light beam and the second light beam intersect at the position of the aperture.

9. The optical system according to claim 8, wherein the region in which the light beam is distributed at the second intersection is smaller than the aperture region of the diaphragm.

10. The optical system according to claim 1, satisfying the following condition (3): 30 ≤ θ1 < 51 ... (3) where, θ1: the angle between the principal ray of the second luminous beam and the optical axis at the second intersection.

11. The optical system according to claim 1, further comprising an aperture member positioned on the magnified side of the first sub-optical system and having an aperture, wherein the aperture is located on the optical axis.

12. The optical system according to claim 11, wherein the aperture material is arranged at the second intersection.

13. The optical system according to claim 11, satisfying the following condition (4): D2 ≤ DL1 / 3 ... (4) where, D2: the maximum dimension of the aperture of the aperture material DL1: the effective lens diameter of the lens with the largest effective lens diameter among the plurality of lenses of the first sub-optical system and the second sub-optical system.

14. An image projection device comprising: an optical system according to any one of claims 1 to 13; and an image forming element that generates an image to be projected onto a screen via the optical system.

15. An imaging device comprising: an optical system according to any one of claims 1 to 13; and an image sensor that receives an optical image formed by the optical system and converts it into an electrical image signal.

Images