Optical system, imaging device, optical contact sensor, and image projection device

Abstract

An optical system (1) is provided with a plurality of lenses (30), and a prism (40) provided to the magnifying side of the plurality of lenses (30). The prism (40) has: a first transmitting surface (41) that is a freeform curved surface; a first reflecting surface (42); a second reflecting surface (43) that is a freeform curved surface; and a second transmitting surface (44) that is a freeform curved surface. A first rectangular area (10) along the reducing conjugate focus has an imaging relationship that is conjugate with a second rectangular area (20) along the magnifying conjugate focus, and does not intersect an optical axis (60) being the axis that goes through the centers of the most among the plurality of lenses (30). If a space is sectioned into a first space (71) and a second space (72) with a first plane (70) as the boundary, then all principal rays that pass through the first rectangular area (10) go through, in the first space (71), the first rectangular area (10), the first transmitting surface (41), and the first reflecting surface (42), and go through, in the second space (72), the second reflecting surface (43) and the second transmitting surface (44).

Description

[Technical Field]

[0001] This disclosure relates to an optical system, an imaging device, an optical contact sensor, and an image projection device. [Background technology]

[0002] Patent Document 1 discloses an optical system that enables projection or imaging of a large screen with a single focal length using a small prism. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-194115 [Overview of the project] [Problems that the invention aims to solve]

[0004] This disclosure provides a compact or low-profile optical system, as well as an imaging device, an optical contact sensor, and an image projection device equipped with the optical system. [Means for solving the problem]

[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 an expansion conjugate point on the expansion side, comprising a plurality of lenses and a prism provided on the expansion side of the plurality of lenses. The prism has a first transmission surface which is a free-form surface, a first reflection surface, a second reflection surface which is a free-form surface, and a second transmission surface which is a free-form surface provided on the reduction side of the first transmission surface. The first rectangular region at the reduction conjugate point has an imaging relationship which is conjugate to the second rectangular region at the expansion conjugate point, and does not intersect the optical axis which is the axis passing through the center of the most lenses among the plurality of lenses. When the space in which the optical system is arranged is divided into a first space and a second space with respect to a first plane, which is a virtual plane perpendicular to the first rectangular region and passing through the optical axis, and is parallel to the first side of the first rectangular region that has the shortest distance to the optical axis, all principal rays passing through the first rectangular region pass through the first rectangular region, the first transmitting surface and the first reflecting surface in the first space, and pass through the second reflecting surface and the second transmitting surface in the second space. When the space is divided into a third space and a fourth space with respect to a second plane, which is a virtual plane passing through the optical axis and perpendicular to the first plane, all principal rays passing through the first rectangular region pass through the second rectangular region and the first transmitting surface in the third space.

[0006] An optical system according to another aspect of the present disclosure is an optical system having a reduction conjugate point on the reduction side and an expansion conjugate point on the expansion side, comprising a plurality of lenses and a prism provided on the expansion side of the plurality of lenses. The first rectangular region at the reduction conjugate point has an imaging relationship that is conjugate to the second rectangular region at the expansion conjugate point and does not intersect the optical axis, which is the axis passing through the centers of the most of the plurality of lenses. The prism has a first reflective surface inclined at an angle greater than 40 degrees and less than 50 degrees with respect to the direction parallel to the first side of the first rectangular region that has the shortest distance to the optical axis, and a second reflective surface having positive power.

[0007] An optical system according to another aspect of the present disclosure is an optical system having a reduction conjugate point on the reduction side and an expansion conjugate point on the expansion side. The first rectangular region at the reduction conjugate point has an imaging relationship that is conjugate to the second rectangular region at the expansion conjugate point. The optical system allows principal rays to pass through a transparent body having a first surface including the second rectangular region and a second surface, passing through the first rectangular region, the second surface, and the second rectangular region in that order or in reverse order. The second surface is not parallel to the first surface.

[0008] An imaging device according to one aspect of the present disclosure comprises an optical system according to the above-described aspect and an image sensor that receives light passing through the optical system.

[0009] An optical contact sensor according to one aspect of the present disclosure comprises an imaging device according to the above-described aspect and a light source that irradiates light toward the second rectangular area, and detects contact with the second rectangular area.

[0010] An image projection apparatus according to one aspect of the present disclosure comprises an optical system according to the above-described aspect and an image forming element that projects an image onto a screen via the optical system. [Effects of the Invention]

[0011] According to this disclosure, it is possible to provide a compact or low-profile optical system, etc. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a schematic perspective view showing the configuration of the optical system according to the embodiment. [Figure 2] Figure 2 is a schematic perspective view illustrating the arrangement of the optical system according to the embodiment, using a first plane, which is a virtual plane. [Figure 3] Figure 3 is a schematic perspective view illustrating the arrangement of the optical system according to the embodiment, using a second plane, which is a virtual plane. [Figure 4] Figure 4 is a schematic perspective view illustrating the positional relationship between the reduced conjugate point and the enlarged conjugate point of the optical system according to the embodiment. [Figure 5] FIG. 5 is a plan view showing a first rectangular region at a reduced conjugate point of the optical system according to the embodiment. [Figure 6] FIG. 6 is a perspective view showing an example of a prism included in the optical system according to the embodiment. [Figure 7] FIG. 7 is a six-sided view of the prism shown in FIG. 6. [Figure 8] FIG. 8 is a schematic perspective view showing a light ray passing through the prism shown in FIG. 6. [Figure 9] FIG. 9 is a schematic perspective view showing an incident angle of light with respect to the first reflecting surface of the prism shown in FIG. 6. [Figure 10] FIG. 10 is a view showing an intermediate imaging position of the optical system according to the embodiment. [[ID=X]] [[ID=Y]] [Figure 11] FIG. 11 is a schematic perspective view schematically showing an image on a main surface of the optical system according to the embodiment. [Figure 12] FIG. 12 is a schematic perspective view showing a maximum angle of a principal ray passing through a second rectangular region at an enlarged conjugate point of the optical system according to the embodiment, and an angle at which the principal ray passes through a second surface of a transparent body. [Figure 13] FIG. 13 is a schematic perspective view showing a passing region of a principal ray on each of a first surface and a second surface of a transparent body according to the embodiment. [Figure 14] FIG. 14 is a schematic cross-sectional view showing an optical path length of a principal ray in a transparent body according to the embodiment. [Figure 15] FIG. 15 is a schematic plan view showing a principal ray incident on a first point closest to an optical axis among four sides of a first rectangular region at a reduced conjugate point of the optical system according to the embodiment. [Figure 16] FIG. 16 is a schematic side view showing an angle when the principal ray shown in FIG. 15 is incident on a second rectangular region at an enlarged conjugate point of the optical system according to the embodiment. [Figure 17] FIG. 17 is a schematic perspective view showing a modified example of a transparent body. [Figure 18] FIG. 18 is a plan view showing a principal ray passing through the optical system according to Example 1. [Figure 19]Figure 19 is a side view showing the principal ray passing through the optical system according to Example 5. [Figure 20] Figure 20 shows the MTF characteristics of the optical system according to Example 1. [Figure 21] Figure 21 shows the MTF characteristics of the optical system according to Example 2. [Figure 22] Figure 22 shows the MTF characteristics of the optical system according to Example 3. [Figure 23] Figure 23 shows the MTF characteristics of the optical system according to Example 4. [Figure 24] Figure 24 shows the MTF characteristics of the optical system according to Example 5. [Figure 25] Figure 25 is a block diagram showing an example of an imaging device equipped with an optical system according to an embodiment. [Figure 26] Figure 26 is a block diagram showing an example of an image projection device equipped with an optical system according to an embodiment. [Modes for carrying out the invention]

[0013] (Summary of this disclosure) 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 an expansion conjugate point on the expansion side, comprising a plurality of lenses and a prism provided on the expansion side of the plurality of lenses. The prism has a first transmission surface which is a free-form surface, a first reflection surface, a second reflection surface which is a free-form surface, and a second transmission surface which is a free-form surface provided on the reduction side of the first transmission surface. The first rectangular region at the reduction conjugate point has an imaging relationship which is conjugate to the second rectangular region at the expansion conjugate point, and does not intersect the optical axis which is the axis passing through the center of the most lenses among the plurality of lenses. When the space in which the optical system is arranged is divided into a first space and a second space with respect to a first plane, which is a virtual plane perpendicular to the first rectangular region and passing through the optical axis, and is parallel to the first side of the first rectangular region that has the shortest distance to the optical axis, all principal rays passing through the first rectangular region pass through the first rectangular region, the first transmitting surface and the first reflecting surface in the first space, and pass through the second reflecting surface and the second transmitting surface in the second space. When the space is divided into a third space and a fourth space with respect to a second plane, which is a virtual plane passing through the optical axis and perpendicular to the first plane, all principal rays passing through the first rectangular region pass through the second rectangular region and the first transmitting surface in the third space.

[0014] This allows for the inclusion of a prism with a free-form reflective surface and a transmissive surface, making it possible to achieve both a wide-angle view and a compact design for the optical system.

[0015] Furthermore, an optical system according to another aspect of the present disclosure is an optical system having a reduction conjugate point on the reduction side and an expansion conjugate point on the expansion side, comprising a plurality of lenses and a prism provided on the expansion side of the plurality of lenses. The first rectangular region at the reduction conjugate point has an imaging relationship that is conjugate to the second rectangular region at the expansion conjugate point, and does not intersect the optical axis, which is the axis passing through the center of the most lenses among the plurality of lenses. The prism has a first reflective surface inclined at an angle greater than 40 degrees and less than 50 degrees with respect to the direction parallel to the first side of the first rectangular region that has the shortest distance to the optical axis, and a second reflective surface having positive power.

[0016] This allows for the inclusion of a prism with a reflective surface tilted at an angle greater than 40 degrees but less than 50 degrees, thus enabling both a wider angle of view and a smaller size for the optical system.

[0017] Furthermore, for example, the prism further includes a first transmission surface which is a free-form surface, and a second transmission surface which is a free-form surface and is located on the side of the first transmission surface that is smaller than the first transmission surface. The optical system may allow the principal ray to pass through the first transmission surface, the first reflection surface, the second reflection surface, and the second transmission surface in this order or in the reverse order.

[0018] As a result, since the prism's transmission surface has a free-form shape, it is possible to achieve both a wide-angle and thin optical system. For example, a larger second rectangular region can be secured.

[0019] Furthermore, an optical system according to another aspect of the present disclosure is an optical system having a reduction conjugate point on the reduction side and an expansion conjugate point on the expansion side. The first rectangular region at the reduction conjugate point has an imaging relationship that is conjugate to the second rectangular region at the expansion conjugate point. The optical system allows principal rays to pass through the first rectangular region, the second surface, and the second rectangular region in that order or in reverse order to a transparent body having a first surface including the second rectangular region and a second surface. The second surface does not have to be parallel to the first surface. Also, for example, the second surface may share one side with the first surface.

[0020] This makes it possible to achieve both a wide-angle and thin optical system. When the optical system is used in an imaging device, reflections on the second surface can be reduced. For example, the occurrence of ghost images can be suppressed. Also, since the optical system is not located on the back side of the first surface of the transparent material, it is possible to avoid strong stress being applied to the optical system when a force is applied to the first surface by contact.

[0021] Furthermore, for example, an optical system according to one aspect of this disclosure may satisfy the following condition (a):

[0022] ωi<ωo···(a) Here, ωo: The maximum angle between the normal of the second rectangular region and the principal ray passing through the second rectangular region. ωi: The angle between the principal ray passing through the second rectangular region at the maximum angle and the normal to the second surface when the principal ray passes through the second surface. That is the case.

[0023] This makes it possible to achieve both a wider angle and thinner optical system. When the optical system is used in an imaging device, reflections on the second surface can be reduced.

[0024] Furthermore, for example, an optical system according to one aspect of the present disclosure comprises a plurality of lenses, and the first rectangular region does not have to intersect the optical axis, which is the axis passing through the centers of the most of the plurality of lenses.

[0025] This ensures that the second rectangular region and the optical system do not overlap when viewed from the normal direction of the second rectangular region. Therefore, since the optical system is not located on the back side of the first surface of the transparent material, it is possible to avoid stress being applied to the optical system when a force is applied to the first surface by contact.

[0026] Furthermore, for example, an optical system according to one aspect of the present disclosure may satisfy the following condition (b) if the transparent body is included and the center line is defined as the line segment connecting the centers of the first side of the first rectangular region that has the shortest distance to the optical axis and the second side that is parallel to the first side.

[0027] 0.1 <H1o / H1i×Vi / Vo<0.4···(b) Here, H1i: The distance between two points on the second surface through which the principal rays that image at both ends of the first edge pass. Vi: The distance between two points on the second plane through which the principal rays that form images at both ends of the center line pass. H1o: The distance between two points on the first plane through which the principal rays that image at both ends of the first edge pass. Vo: The distance between two points on the first plane through which the principal rays that form images at both ends of the center line pass. That is the case.

[0028] This allows for a larger second rectangular region to be secured. When the optical system is used in an imaging device, sufficient light can be extracted from deep within the transparent material.

[0029] Furthermore, for example, an optical system according to one aspect of the present disclosure may satisfy the following condition (c) if, among the four sides of the first rectangular region, the first side having the shortest distance to the optical axis and the second side being parallel to the first side.

[0030] 0.1 <H1o / H1i×H2i / H2o<0.4···(c) Here, H1i: The distance between two points on the second surface through which the principal rays that image at both ends of the first edge pass. H2i: The distance between two points on the second plane through which the principal rays that image at both ends of the second edge pass. H1o: The distance between two points on the first plane through which the principal rays that image at both ends of the first edge pass. H2o: The distance between two points on the first surface through which the principal rays that image at both ends of the second edge pass. That is the case.

[0031] This allows for a larger second rectangular region to be secured. When the optical system is used in an imaging device, sufficient light can be extracted from deep within the transparent material.

[0032] Furthermore, for example, an optical system according to one aspect of the present disclosure may include a prism provided on the magnifying side of the plurality of lenses. The prism has a first free-form surface for transmission, a first reflective surface, a second reflective surface having positive power, and a second free-form surface for transmission provided on the reducing side of the first transmission. The optical system allows the principal ray to pass through the first transmission, the first reflective surface, the second reflective surface, and the second transmission in this order or in reverse order.

[0033] This allows for the inclusion of a prism with a free-form transmissive surface and a positively reflective surface, enabling both wide-angle and thin optical systems. For example, a larger second rectangular region can be secured.

[0034] Furthermore, for example, the first transmitting surface may cause the principal ray passing through the first point, which is the point closest to the optical axis on the first side of the first rectangular region that has the shortest distance to the optical axis, to diverge in a direction parallel to the optical axis and converge in a direction perpendicular to the optical axis.

[0035] This makes it possible to reduce the height of the optical system while suppressing distortion.

[0036] Furthermore, for example, the second transmitting surface may cause the principal ray passing through the first point, which is the point closest to the optical axis on the first side of the first rectangular region that has the shortest distance to the optical axis, to diverge in a direction parallel to the first side and converge in a direction perpendicular to the first side.

[0037] This makes it possible to reduce the height of the optical system while suppressing distortion.

[0038] Furthermore, for example, the converging effect of the second reflective surface on the principal ray passing through the first point, which is the point closest to the optical axis on the first side of the first rectangular region that has the shortest distance to the optical axis, may be greater in the direction parallel to the first side than in the direction perpendicular to the first side.

[0039] This makes it possible to reduce the height of the optical system.

[0040] Furthermore, for example, an optical system according to one aspect of the present disclosure has an intermediate imaging position that is conjugate to each of the reduction conjugate point and the expansion conjugate point, and the intermediate imaging position may be located between the second reflective surface and the second transmissive surface.

[0041] This allows for a shorter working distance.

[0042] Furthermore, for example, in an optical system according to one aspect of the present disclosure, if the point on the first side furthest from the second rectangular region is designated as the second point, the point on the first side closest to the second rectangular region is designated as the fourth point, the point on the second side of the first rectangular region that is parallel to the first side is designated as the third point, and the point on the second side closest to the second rectangular region is designated as the fifth point, then the following condition (d) may be satisfied.

[0043] i1 <i2<i3<i4···(d) Here, i1: The angle of incidence when the principal ray passing through the second point is incident on the first reflecting surface. i2: The angle of incidence when the principal ray passing through the third point is incident on the first reflecting surface. i3: The angle of incidence when the principal ray passing through the fourth point is incident on the first reflecting surface. i4: The angle of incidence when the principal ray passing through the fifth point is incident on the first reflecting surface. That is the case.

[0044] This makes it possible to reduce the height and size of the optical system.

[0045] Furthermore, for example, the angle of incidence when the principal ray passing through the fifth point is incident on the first reflecting surface may be greater than 65 degrees and less than 85 degrees.

[0046] This allows for reduced sensitivity to shape errors in the first reflecting surface and improved ease of manufacturing when the incident angle i4 is less than 85 degrees. Conversely, when the incident angle i4 is greater than 65 degrees, the prism can be miniaturized.

[0047] Furthermore, for example, an optical system according to one aspect of the present disclosure may include a transparent body having a first surface including the second rectangular region and a second surface. The optical system may allow principal rays to pass through the first rectangular region, the second surface, and the second rectangular region in that order or in the reverse order.

[0048] This allows the optical system to be used in an imaging device to capture images of objects that come into contact with the second surface of a transparent object, for example. In other words, the imaging device can be used as an optical contact sensor.

[0049] Furthermore, for example, the transparent body may comprise a first medium having the first surface, and a flat, plate-shaped second medium smaller than the first medium and having the second surface. The second surface may be in contact with air, and the surface of the second medium opposite to the second surface may be adjacent to a surface different from the first surface of the first medium.

[0050] This makes it possible to select the optimal material according to the function of each surface of the transparent object.

[0051] Furthermore, for example, an optical system according to one aspect of the present disclosure may satisfy the following condition (e):

[0052] n1 <n2···(e) Here, n1: Refractive index of the first medium n2: Refractive index of the second medium That is the case.

[0053] This allows for minimizing field curvature.

[0054] Furthermore, for example, the refractive index n2 of the second medium may be greater than 1.45.

[0055] This allows for minimizing field curvature.

[0056] Furthermore, for example, the refractive index n1 of the first medium may be greater than 1.3 and less than 1.5.

[0057] This allows for suppression of reflection losses at the interface between the first and second media when the refractive index n1 is greater than 1.3. A wider field of view can be secured when the refractive index n1 is less than 1.5.

[0058] Furthermore, for example, an optical system according to one aspect of this disclosure may satisfy the following condition (f).

[0059] E1 <E2···(f) Here, E1: Young's modulus of the first medium E2: Young's modulus of the second medium That is the case.

[0060] This allows for the suppression of deformation of the second medium even if the first medium deforms upon contact with the first surface. When the optical system is used in an imaging device, the shape of light emission on the second surface does not change, making it possible to capture changes in the shape of the first surface.

[0061] Furthermore, for example, the Young's modulus of the second medium may be greater than 400 MPa and less than 200,000 MPa.

[0062] As a result, when the optical system is used in an imaging device, the shape of light emission on the second surface does not change, making it possible to capture changes in the shape of the first surface.

[0063] Furthermore, for example, the Young's modulus of the first medium may be greater than 0.01 MPa and less than 3 MPa.

[0064] This allows the shape of the first surface to be easily altered. Therefore, when the optical system is used in an imaging device, the changes in the shape of the first surface can be captured.

[0065] Furthermore, for example, in an optical system according to one aspect of the present disclosure, if the first point is defined as the point closest to the optical axis on the first side of the first rectangular region that has the shortest distance to the optical axis, and the sixth point is defined as the point closest to the optical axis on the second side of the first rectangular region that is parallel to the first side, then the following condition (g) may be satisfied.

[0066] 5 <Lb / La<15···(g) Here, La: The optical path length of the principal ray passing through the first point within the transparent body. Lb: The optical path length of the principal ray passing through the sixth point within the transparent body. That is the case.

[0067] This makes it possible to enlarge the second rectangular region while simultaneously making the transparent material thinner.

[0068] Furthermore, for example, the angle between the principal ray passing through the second rectangular region at the maximum angle with respect to the normal of the second rectangular region and the normal of the second surface when the principal ray passing through the second surface also passes through the second surface may be less than 30 degrees.

[0069] This makes it possible to suppress reflections on the second surface.

[0070] Furthermore, for example, the angle between the plane containing the second surface and the plane containing the first surface may be greater than 45 degrees and less than 85 degrees.

[0071] This makes it possible to suppress the emission angle of light from the second surface when the optical system is used in an imaging device.

[0072] Furthermore, for example, the maximum angle of the principal ray passing through the second rectangular region may be greater than 65 degrees.

[0073] This makes it possible to enlarge the second rectangular region while simultaneously reducing the height of the optical system.

[0074] Furthermore, for example, an optical system according to one aspect of this disclosure may satisfy the following condition (h).

[0075] L1 <L2···(h) Here, L1: The length of the first side of the first rectangular region that has the shortest distance to the optical axis. L2: Length of the third side of the first rectangular region that is perpendicular to the first side. That is the case.

[0076] This allows the second rectangular region to be made elongated.

[0077] Furthermore, for example, an optical system according to one aspect of this disclosure may satisfy the following condition (i):

[0078] 0.1 <d / D<0.3···(i) Here, d: The shortest distance between the first rectangular region and the optical axis, which is the first side of the four regions that has the shortest distance to the optical axis. D: Length of the third side of the first rectangular region that is perpendicular to the first side. That is the case.

[0079] This enables miniaturization of the optical system. Furthermore, when the optical system is used in an imaging device, it prevents the emission angle from the second rectangular region from becoming too large, thereby suppressing a decrease in light intensity. Additionally, it prevents the prism and the second rectangular region from overlapping when viewed from the normal direction of the second rectangular region.

[0080] Furthermore, for example, in an optical system according to one aspect of the present disclosure, if the first point is defined as the point closest to the optical axis on the first side of the first rectangular region that has the shortest distance to the optical axis among the four sides of the first rectangular region, and the seventh point is defined as a point included in the second rectangular region that has an imaging relationship with the first point, then the following conditions (j1) and (j2) may be satisfied.

[0081] 5 <X / d<20···(j1) 5 <Y / d<20···(j2) Here, d: The shortest distance between the first rectangular region and the optical axis, which is the first side of the four regions that has the shortest distance to the optical axis. X: Distance between point 1 and point 7 along a direction parallel to the aforementioned side 1. Y: The distance between the first point and the seventh point along the direction perpendicular to each of the first side and the optical axis. That is the case.

[0082] This allows for miniaturization of the optical system while maintaining a large second rectangular region. For example, if X / d satisfies condition (j1), it is possible to achieve both a low profile optical system and suppression of peripheral light falloff. Also, if Y / d satisfies condition (j2), it is possible to achieve both miniaturization and wide-angle optical system.

[0083] Furthermore, for example, an optical system according to one aspect of this disclosure may satisfy the following condition (j3).

[0084] 10 <Z / d<30···(j3) Here, Z: The distance between the first point and the seventh point along a direction parallel to the optical axis. That is the case.

[0085] This makes it possible to achieve both miniaturization of the optical system and suppression of the increase in chromatic aberration.

[0086] Furthermore, for example, in an optical system according to one aspect of the present disclosure, if the first point is defined as the point closest to the optical axis on the first side of the first rectangular region that has the shortest distance to the optical axis among the four sides of the first rectangular region, and the seventh point is defined as a point included in the second rectangular region that has an imaging relationship with the first point, then the following condition (k) may be satisfied.

[0087] 0.1 < θo / θi < 0.3 ···(k) Here, θi: The width of the incident or exit angle made by the principal ray passing through the first point in a plane that passes through the first edge and is parallel to both the first edge and the optical axis. θo: The width of the angle formed when the principal rays that form θi pass through the seventh point. That is the case.

[0088] This makes it possible to enlarge the second rectangular region while miniaturizing the optical system.

[0089] Furthermore, for example, among the plurality of lenses, the lens closest to the first rectangular region may have a D-cut on the side that does not include the optical axis in a direction perpendicular to the first side.

[0090] This makes it possible to reduce the height of the optical system.

[0091] Furthermore, for example, the angle between the plane containing the second rectangular region and the plane containing the first rectangular region may be greater than 85 degrees and less than 95 degrees.

[0092] This makes it possible to reduce the height of the optical system.

[0093] Furthermore, an imaging device according to one aspect of the present disclosure comprises an optical system according to the above-described aspect and an image sensor that receives light passing through the optical system.

[0094] This allows us to achieve the same effect as the optical system described above.

[0095] Furthermore, an optical contact sensor according to one aspect of the present disclosure comprises an imaging device according to the above-described aspect and a light source that irradiates light toward the second rectangular area, and detects contact with the second rectangular area.

[0096] This allows us to achieve the same effect as the optical system described above.

[0097] Furthermore, an image projection apparatus according to one aspect of the present disclosure comprises an optical system according to the above-described aspect and an image forming element that projects an image onto a screen via the optical system.

[0098] This allows us to achieve the same effect as the optical system described above.

[0099] The embodiments will be described in detail below with reference to the drawings.

[0100] The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, arrangement and connection configurations of components, steps, and the order of steps shown in the following embodiments are examples only and are not intended to limit this disclosure. Furthermore, any components in the following embodiments that are not described in an independent claim will be described as optional components.

[0101] Furthermore, each figure is a schematic diagram and not necessarily a strictly accurate representation. Therefore, for example, the scale may not necessarily match in each figure. Also, in each figure, substantially identical components are given the same reference numerals, and redundant explanations are omitted or simplified.

[0102] Furthermore, in this specification, terms indicating relationships between elements such as parallel or perpendicular, terms indicating the shape of elements such as rectangles, and numerical ranges do not represent only strict meanings, but also include substantially equivalent ranges, such as differences of a few percent.

[0103] Furthermore, in this specification and the drawings, the x, y, and z axes represent the three axes of a three-dimensional Cartesian coordinate system. In each embodiment, the x and y axes are parallel to two orthogonal sides of the first rectangular region. The z axis direction is the normal direction of the first rectangular region.

[0104] Note that the x-axis direction is the height direction of the optical system. In other words, in this specification, "low profile" means shortening the height in the x-axis direction. Also, in this specification, "miniaturization" means shortening the length in the direction along at least one of the x-axis, y-axis, and z-axis.

[0105] Furthermore, in this specification, "a light ray passes through a surface" means that a light ray is incident on a surface and is reflected or transmitted. That is, "a light ray passes through a reflective surface" means that a light ray is incident on a reflective surface and is reflected by that surface. The reflection is specular reflection on a microscopic surface. "A light ray passes through a transmissive surface" means that a light ray is incident on a transmissive surface and is transmitted through that surface. During transmission, the light ray is refracted according to the difference in refractive index.

[0106] Furthermore, in this specification, ordinal numbers such as "first," "second," etc., do not mean the number or order of components unless otherwise specified, but are used to avoid confusion and to distinguish similar components.

[0107] (Embodiment) [overview] First, an overview of the optical system according to this embodiment will be described using Figure 1. Figure 1 is a schematic perspective view showing the configuration of the optical system 1 according to this embodiment.

[0108] The optical system 1 shown in Figure 1 has a reduction conjugate point on the reduction side and an expansion conjugate point on the expansion side. The reduction conjugate point is the imaging position on the reduction side of the optical system 1 and is defined as the first rectangular region 10. The expansion conjugate point is the imaging position on the expansion side of the optical system 1 and is defined as the second rectangular region 20. The first rectangular region 10 has an imaging relationship that is conjugate to the second rectangular region 20. Note that the second rectangular region 20 may not be a perfect rectangle due to distortion.

[0109] When optical system 1 is used in an imaging device, the first rectangular region 10 becomes the region where the imaging surface is located, and the second rectangular region 20 becomes the region where the object surface is located. When optical system 1 is used in an image projection device, the first rectangular region 10 becomes the image display region where the image from the projection source is formed, and the second rectangular region 20 becomes the region where the projection surface, such as a screen, is located. The optical relationship between the first rectangular region 10 and the second rectangular region 20 will be explained in detail later.

[0110] In the following explanation, we will mainly use the case where optical system 1 is used in an imaging device as an example. In this case, optical system 1 guides the light emitted from the second rectangular region 20 on the magnification side to the first rectangular region 10 on the reduction side. When optical system 1 is used in an image projection device, the direction of light propagation is reversed. Also, the relationship between the angle of incidence and the angle of emission (or reflection) with respect to a predetermined surface is reversed.

[0111] As shown in Figure 1, the optical system 1 comprises a plurality of lenses 30, a prism 40, and a transparent body 50. The plurality of lenses 30, the prism 40, and the transparent body 50 are arranged in this order from the reducing side to the expanding side of the optical system 1.

[0112] Each of the multiple lenses 30 has a predetermined lens surface on at least one of its reducing and magnifying sides. For example, each lens 30 is a biconvex lens, a plano-convex lens, a convex meniscus lens, a biconcave lens, a plano-concave lens, or a concave meniscus lens. The lens surface may also be an aspherical lens having a free-form surface. The multiple lenses 30 include lenses with rotationally symmetrical shapes.

[0113] Although not shown in Figure 1, the optical system 1 also includes an aperture diaphragm. The aperture diaphragm is positioned between the multiple lenses 30 and is an optical element that defines the range through which the light beam passes through the optical system 1. The light ray passing through the center of the aperture diaphragm is the principal ray.

[0114] The prism 40 is positioned on the magnifying side of the multiple lenses 30. The prism 40 has a first transmissive surface 41, a first reflective surface 42, a second reflective surface 43, and a second transmissive surface 44. In this embodiment, the first transmissive surface 41, the second reflective surface 43, and the second transmissive surface 44 are each free-form surfaces. The first reflective surface 42 is a flat surface.

[0115] The prism 40 is formed using a transparent medium such as glass or resin. The first transmitting surface 41, the first reflecting surface 42, the second reflecting surface 43, and the second transmitting surface 44 are each part of the outer surface of the prism 40. A specific example of the configuration of the prism 40 will be described later.

[0116] The transparent body 50 has a first surface 51 containing a second rectangular region 20, and a second surface 52. The second surface 52 is the surface through which the principal ray passing through the first surface 51 passes. The first surface 51 and the second surface 52 are both planar. In this embodiment, the second surface 52 is not parallel to the first surface 51. Specifically, the second surface 52 shares one side with the first surface 51. Also, the second surface 52 is inclined at a predetermined angle with respect to the first surface 51.

[0117] The transparent body 50 is formed using a transparent medium such as glass or resin. Note that the optical system 1 does not necessarily have to include the transparent body 50.

[0118] Figure 1 illustrates the optical axis 60 and the reference axis 61 perpendicular to the optical axis 60. The optical axis 60 and the reference axis 61 are both hypothetical straight lines extending in one direction. The optical axis 60 is the axis that passes through the center of the most lenses among the multiple lenses 30. The reference axis 61 is the axis that is perpendicular to the optical axis 60 and is also perpendicular to the first side 11 of the first rectangular region 10, which has the shortest distance to the optical axis 60 among the four sides.

[0119] The arrangement of each component of the optical system 1 is determined based on a virtual plane passing through the optical axis 60 and / or the reference axis 61. The arrangement of the optical system 1 will be explained below using Figures 2 and 3.

[0120] Figure 2 is a schematic perspective view illustrating the arrangement of the optical system 1 according to this embodiment using a virtual plane, the first plane 70. The first plane 70 shown in Figure 2 is a virtual plane perpendicular to the first rectangular region 10 and passing through the optical axis 60, and is parallel to the first side 11 of the first rectangular region 10. The first plane 70 is the xz plane.

[0121] As shown in Figure 2, the space in which the optical system 1 is located can be divided into a first space 71 and a second space 72, with the first plane 70 as the boundary. The first space 71 is the space on the negative side of the y-axis, and the second space 72 is the space on the positive side of the y-axis.

[0122] In this embodiment, all principal rays passing through the first rectangular region 10 pass through the first rectangular region 10, the first transmissive surface 41, and the first reflective surface 42 in the first space 71. In other words, the first rectangular region 10, the first transmissive surface 41, and the first reflective surface 42 are substantially located almost entirely within the first space 71.

[0123] Furthermore, all principal rays passing through the first rectangular region 10 pass through the second reflective surface 43 and the second transmissive surface 44 in the second space 72. In other words, the second reflective surface 43 and the second transmissive surface 44 are substantially located almost entirely within the second space 72.

[0124] Thus, the prism 40 is positioned across the first space 71 and the second space 72. Similarly, the multiple lenses 30 are also positioned across the first space 71 and the second space 72. At least a portion of the second rectangular region 20 and the second surface 52 of the transparent body 50 are positioned in the first space 71. In Figure 2, the surfaces positioned in the first space 71 are shaded with dots. The contours of the surfaces positioned in the second space 72 are represented by dashed lines (excluding the contour of the second rectangular region 20).

[0125] Figure 3 is a schematic perspective view illustrating the arrangement of the optical system 1 according to this embodiment using a virtual plane, the second plane 80. The second plane 80 shown in Figure 3 is a virtual plane that passes through the optical axis 60 and is perpendicular to the first plane 70. The second plane 80 includes the optical axis 60 and the reference axis 61. The second plane 80 is the yz plane.

[0126] As shown in Figure 3, the space in which the optical system 1 is located can be divided into a third space 81 and a fourth space 82, with the second plane 80 as the boundary. The third space 81 is the space on the negative side of the x-axis, and the fourth space 82 is the space on the positive side of the x-axis.

[0127] In this embodiment, all principal rays passing through the first rectangular region 10 pass through the second rectangular region 20 and the first transmissive surface 41 in the third space 81. In other words, substantially the entire area of ​​each surface of the second rectangular region 20 and the first transmissive surface 41 is located in the third space 81.

[0128] The first reflective surface 42, the second reflective surface 43, and the second transmissive surface 44 are arranged in only the third space 81, only the fourth space 82, or spanning both the third space 81 and the fourth space 82. The multiple lenses 30 and the first rectangular region 10 are arranged spanning both the third space 81 and the fourth space 82. At least a portion of the second surface 52 of the transparent body 50 is located in the third space 81. In Figure 3, the surfaces located in the third space 81 are shaded with dots, and their outlines are represented by dashed lines.

[0129] [First rectangular region and second rectangular region] Next, the correspondence between the first rectangular region 10 at the reduced conjugate point of the optical system 1 and the second rectangular region 20 at the enlarged conjugate point will be explained using Figures 4 and 5, with appropriate reference to Figure 1.

[0130] Figure 4 is a schematic perspective view illustrating the positional relationship between the reduced conjugate point and the expanded conjugate point of the optical system 1 according to this embodiment. As shown in Figure 4, the first rectangular region 10 at the reduced conjugate point does not intersect the optical axis 60. That is, the first rectangular region 10 is located at a predetermined distance from the optical axis 60 in one direction.

[0131] The first rectangular region 10 and the second rectangular region 20 have an imaging relationship. For example, the aspect ratio of the first rectangular region 10 and the aspect ratio of the second rectangular region 20 are equal. The aspect ratio is the ratio of the lengths of the short side to the long side of each rectangular region. The enlarged second rectangular region 20 has a larger area than the reduced first rectangular region 10. Note that the second rectangular region 20 may not be a perfect rectangle due to distortion.

[0132] The angle between the plane containing the second rectangular region 20 and the plane containing the first rectangular region 10 is greater than 85 degrees and less than 95 degrees. Specifically, the second rectangular region 20 and the first rectangular region 10 are perpendicular. In this embodiment, the plane formed by the first rectangular region 10 is defined as the xy-plane. In this case, the second rectangular region 20 is parallel to the yz-plane.

[0133] Figure 4 shows a seventh point 201 located in the second rectangular region 20, which has an imaging relationship with the first point 101 on the first side 11 of the first rectangular region 10. When the optical system 1 is used as an imaging device, the principal ray emitted from the seventh point 201 passes through the prism 40 and the multiple lenses 30 and is imaged onto the first point 101.

[0134] Similarly, Figure 1 shows the second point 102, third point 103, fourth point 104, fifth point 105, and sixth point 106 included in the first rectangular region 10, and the eighth point 202, ninth point 203, tenth point 204, eleventh point 205, and twelfth point 206 included in the second rectangular region 20. The second point 102 and the eighth point 202 have an imaging relationship. The third point 103 and the ninth point 203 have an imaging relationship. The fourth point 104 and the tenth point 204 have an imaging relationship. The fifth point 105 and the eleventh point 205 have an imaging relationship. The sixth point 106 and the twelfth point 206 have an imaging relationship.

[0135] Figure 5 is a plan view showing the first rectangular region 10 at the reduced conjugate point of the optical system 1 according to the embodiment. As shown in Figure 5, the plan view shape of the first rectangular region 10 is a rectangle that is elongated in the y-axis direction. The first rectangular region 10 has a first side 11, a second side 12, a third side 13, and a fourth side 14.

[0136] The first side 11 is the side of the first rectangular region 10 that has the shortest distance to the optical axis 60 among the four sides. The first point 101 shown in Figure 5 is the point on the first side 11 that is closest to the optical axis 60. In other words, the first point 101 is the foot of the perpendicular to the optical axis 60 on the first side 11. For example, the first point 101 is the midpoint of the first side 11. In the xy-plane, the line connecting the first point 101 and the optical axis 60 is the reference axis 61.

[0137] The second side 12 is parallel to the first side 11. The sixth point 106 shown in Figure 5 is the point on the second side 12 closest to the optical axis 60. For example, the sixth point 106 is the midpoint of the second side 12. The sixth point 106 is the intersection of the second side 12 and the reference axis 61.

[0138] The third side 13 is the side that is further from the second rectangular region 20 among the two sides that are perpendicular to the first side 11 and the second side 12. The fourth side 14 is the side that is closer to the second rectangular region 20 among the two sides that are perpendicular to the first side 11 and the second side 12.

[0139] The second point 102 is the point furthest from the second rectangular region 20 on the first side 11. The second point 102 is the endpoint of the first side 11 and the intersection of the first side 11 and the third side 13.

[0140] The third point 103 is the point furthest from the second rectangular region 20 on the second side 12. The third point 103 is the endpoint of the second side 12 and the intersection of the second side 12 and the third side 13.

[0141] The fourth point 104 is the point closest to the second rectangular region 20 on the first side 11. The fourth point 104 is an endpoint of the first side 11 and the intersection of the first side 11 and the fourth side 14.

[0142] The fifth point 105 is the point closest to the second rectangular region 20 on the second side 12. The fifth point 105 is an endpoint of the second side 12 and the intersection of the second side 12 and the fourth side 14.

[0143] Here, as shown in Figure 5, we define the length of the first side 11 (= the length of the second side 12) as L1. Also, we define the length of the third side 13 (= the length of the fourth side 14) as L2 or D. In this case, the following condition (h) is satisfied.

[0144] L1 <L2···(h)

[0145] The aspect ratio of the first rectangular region 10 is, for example, the ratio of L2 to L1. L2:L1 can be, for example, 3:2, 4:3, 16:9, 256:135, etc., but is not particularly limited.

[0146] Furthermore, the shortest distance between the first point 101 and the optical axis 60 is defined as d. d corresponds to the amount of decentering from the optical axis 60 of the first rectangular region 10. In this case, the shortest distance d is shorter than the length D of the longer side of the first rectangular region 10. The following condition (i) is satisfied.

[0147] 0.1 <d / D<0.3···(i)

[0148] By having a d / D ratio less than 0.3, the size of the optical system 1 can be suppressed. If the optical system 1 is used in an imaging device, and d / D is too large, the emission angle from the second rectangular region 20 will become too large, which may lead to a decrease in light intensity. In this embodiment, by having a d / D ratio less than 0.3, the decrease in light intensity can be suppressed. Also, by having a d / D ratio greater than 0.1, it is possible to avoid the prism 40 and the second rectangular region 20 overlapping when viewed from the normal direction of the second rectangular region 20.

[0149] The positional relationship between the first rectangular region 10 and the second rectangular region 20 can be expressed based on the positional relationship between the first point 101 and the seventh point 201 shown in Figure 4. Specifically, the optical system 1 according to this embodiment satisfies the following conditions (j1) and (j2).

[0150] 5 <X / d<20···(j1) 5 <Y / d<20···(j2)

[0151] Here, X is the distance between the first point 101 and the seventh point 201 along the direction parallel to the first side 11 (i.e., the x-axis direction). Y is the distance between the first point 101 and the seventh point 201 along the direction perpendicular to the first side 11 and the optical axis 60, respectively (i.e., the y-axis direction). Note that d is the decentering amount shown in Figure 5.

[0152] A value of X / d greater than 5 can suppress the decrease in light intensity in the peripheral areas (e.g., on the edges of a rectangular region). Furthermore, a value of X / d less than 20 allows for a lower profile optical system 1. Preferably, X / d may also be less than 15.

[0153] Furthermore, a Y / d greater than 5 allows for easy widening of the field of view. Also, a Y / d less than 20 allows for miniaturization of the optical system 1. Preferably, Y / d may be less than 15.

[0154] Furthermore, optical system 1 also satisfies condition (j3).

[0155] 10 <Z / d<30···(j3)

[0156] Here, Z is the distance between the first point 101 and the seventh point 201 along the direction parallel to the optical axis 60 (i.e., the z-axis direction).

[0157] A Z / d value greater than 10 can suppress the increase in lateral chromatic aberration. Furthermore, a Z / d value less than 30 allows for miniaturization of the optical system 1. Preferably, Z / d may be less than 25.

[0158] [prism] Next, the specific configuration of prism 40 will be explained using Figures 6, 7, 8, and 9.

[0159] Figure 6 is a perspective view showing an example of a prism 40 included in the optical system 1 according to this embodiment. Figure 7 is a six-view drawing of the prism 40 shown in Figure 6. Specifically, (a) is a front view, (b) is a left side view, (c) is a right side view, (d) is a rear view, (e) is a top view, and (f) is a bottom view. Here, the view of the prism 40 from the first rectangular region 10 along the optical axis 60 is considered the front. Specifically, the negative side of the z axis is considered the front, the positive side of the x axis is considered upward, the negative side of the x axis is considered downward, the positive side of the y axis is considered to the right, and the negative side of the y axis is considered to the left.

[0160] Figure 8 is a schematic perspective view showing light rays passing through the prism 40 shown in Figure 6. Figure 9 is a schematic perspective view showing the angle of incidence of light with respect to the first reflective surface 42 of the prism 40 shown in Figure 6.

[0161] As described above, the prism 40 has a first transmission surface 41, a first reflecting surface 42, a second reflecting surface 43, and a second transmission surface 44. Specifically, a portion of the outer surface of the prism 40 functions as the first transmission surface 41, the first reflecting surface 42, the second reflecting surface 43, and the second transmission surface 44.

[0162] In this embodiment, as shown in Figures 8 and 9, the optical system 1 allows the principal ray to pass through the first transmission surface 41, the first reflection surface 42, the second reflection surface 43, and the second transmission surface 44 (which are not shown in Figure 9) in this order or in the reverse order. When the optical system 1 is used in an imaging device, the principal ray passes through the first transmission surface 41, the first reflection surface 42, the second reflection surface 43, and the second transmission surface 44 in that order. When the optical system 1 is used in an image projection device, the principal ray passes through the second transmission surface 44, the second reflection surface 43, the first reflection surface 42, and the first transmission surface 41 in that order.

[0163] The first transmission surface 41 faces the negative side of the x-axis, as shown in Figures 6 and 7(b), (c), and (f). When the optical system 1 is used as an imaging device, the first transmission surface 41 functions as the incident surface for the principal rays to the prism 40. When the optical system 1 is used as an image projection device, the first transmission surface 41 functions as the exit surface for the principal rays from the prism 40.

[0164] When the optical system 1 is used in an imaging device, the first transmission surface 41 causes the principal ray passing through the first point 101 to diverge in a direction parallel to the optical axis 60 (i.e., in the z-axis direction) and converge in a direction perpendicular to the optical axis 60. This suppresses distortion, enables miniaturization of the prism 40, and allows for a lower profile optical system 1.

[0165] The first reflective surface 42 faces the positive x-axis and the positive y-axis, as shown in Figures 6 and 7(a), (b), (c), and (e). The first reflective surface 42 causes total internal reflection of the principal ray due to the refractive index difference between the prism 40 and air. As shown in Figure 8, the first reflective surface 42 reflects the light that has passed through the first transmissive surface 41 toward the second reflective surface 43. Alternatively, it reflects the light reflected by the second reflective surface 43 toward the first transmissive surface 41.

[0166] In this embodiment, the first reflective surface 42 is a plane. The first reflective surface 42 is inclined at an angle greater than 40 degrees and less than 50 degrees with respect to the direction parallel to the first side 11 of the first rectangular region 10 (i.e., the x-axis direction). The angle θ shown in Figure 7(b) is the inclination angle of the first reflective surface 42 with respect to the x-axis. The angle θ is, for example, 45 degrees.

[0167] As shown in Figure 9, the angles at which the principal rays are incident on the first reflective surface 42 are defined as i1, i2, i3, and i4. The angle of incidence is the angle between the ray and the normal to the surface, for example, the angle between the principal rays and the normal to the first reflective surface 42. Specifically, the angle of incidence i1 is the angle at which the principal rays passing through the second point 102 and the eighth point 202 are incident on the first reflective surface 42. The angle of incidence i2 is the angle at which the principal rays passing through the third point 103 and the ninth point 203 are incident on the first reflective surface 42. The angle of incidence i3 is the angle at which the principal rays passing through the fourth point 104 and the tenth point 204 are incident on the first reflective surface 42. The angle of incidence i4 is the angle at which the principal rays passing through the fifth point 105 and the eleventh point 205 are incident on the first reflective surface 42.

[0168] In this case, the first reflective surface 42 satisfies the following condition (d):

[0169] i1 <i2<i3<i4···(d)

[0170] In other words, for all principal rays passing through the first rectangular region 10, the angle of incidence of a principal ray with respect to the first reflecting surface 42 increases as it moves further away from the second rectangular region 20 along the x-axis and further away along the y-axis (closer to the optical axis 60). Therefore, the angle of incidence i1 of the principal ray passing through the second point 102, which is the point furthest from the second rectangular region 20 along the x and y axes respectively, is the smallest. Also, the angle of incidence i4 of the principal ray passing through the fifth point 105, which is the point closest to the second rectangular region 20 along the x and y axes respectively, is the largest. This makes it possible to reduce the height and size of the optical system 1.

[0171] The incident angle i4 is, for example, greater than 65 degrees and less than 85 degrees. A smaller incident angle i4 than 85 degrees suppresses the occurrence of aberrations when shape errors occur in the first reflective surface 42, thereby improving ease of manufacturing. A larger incident angle i4 than 65 degrees allows for miniaturization of the prism 40. Preferably, the incident angle i4 may be greater than 70 degrees. Also, the incident angle i4 may be less than 82 degrees.

[0172] The second reflective surface 43 faces the positive side of the z-axis, as shown in Figures 6 and 7(b), (c), (d), (e), and (f). The second reflective surface 43 causes total internal reflection of the principal ray due to the refractive index difference between the prism 40 and air. As shown in Figure 8, the second reflective surface 43 reflects the light reflected by the first reflective surface 42 toward the second transmissive surface 44. Alternatively, it reflects the light that has passed through the second transmissive surface 44 toward the first reflective surface 42.

[0173] The second reflecting surface 43 has positive power. Specifically, the converging effect of the second reflecting surface 43 on the principal ray passing through the first point 101 is greater in the direction parallel to the first side 11 (i.e., the x-axis direction) than in the direction perpendicular to the first side 11 (specifically, the y-axis direction). This makes it possible to miniaturize the prism 40 and reduce the height of the optical system 1.

[0174] The second transmission surface 44 faces the negative side of the z-axis, as shown in Figures 6 and 7(a), (e), and (f). The second transmission surface 44 is located on the smaller side than the first transmission surface 41. When the optical system 1 is used as an imaging device, the second transmission surface 44 functions as the exit surface for the principal rays from the prism 40. When the optical system 1 is used as an image projection device, the second transmission surface 44 functions as the incident surface for the principal rays to the prism 40.

[0175] When the optical system 1 is used in an imaging device, the second transmission surface 44 causes the principal ray passing through the first point 101 to diverge in a direction parallel to the first side 11 (i.e., in the x-axis direction) and converge in a direction perpendicular to the first side 11 (specifically, in the y-axis direction). This suppresses distortion, enables miniaturization of the prism 40, and allows for a lower profile optical system 1.

[0176] In this embodiment, the optical system 1 has an intermediate imaging position that is conjugate to both the reduced conjugate point and the enlarged conjugate point. As shown in Figure 10, the intermediate imaging position 90 is located between the second reflective surface 43 and the second transmissive surface 44. Figure 10 is a diagram showing the intermediate imaging position 90 of the optical system 1 according to this embodiment. This makes it possible to shorten the working distance.

[0177] Figure 11 is a schematic perspective view illustrating the images on the main surfaces of the optical system 1 according to this embodiment. In Figure 11, three arrows are shown on each surface, represented by solid, dashed, and dotted lines. For example, within the first rectangular region 10, a solid arrow is shown extending along the first side 11 from the second point 102 to the fourth point 104. Similarly, a dotted arrow is shown extending along the second side 12 from the third point 103 to the fifth point 105. Furthermore, a dashed arrow is shown extending from the center of the dotted arrow towards the center of the solid arrow.

[0178] On each surface, arrows of the same line type schematically represent the same image. For example, focusing on a solid arrow, a broken line (not shown) tracing the tip of the solid arrow from the second rectangular region 20 to the first rectangular region 10 corresponds to the schematic optical path of the principal ray. In this embodiment, the principal ray passes through the second rectangular region 20, the second surface 52 of the transparent body 50, the first transmitting surface 41, the first reflecting surface 42, the second reflecting surface 43, the second transmitting surface 44, the multiple lenses 30, and the first rectangular region 10 in this order or in the reverse order.

[0179] In this embodiment, the first transmissive surface 41, the second reflective surface 43, and the second transmissive surface 44 are each free-form surfaces. Specific examples of the shapes of each surface will be illustrated later.

[0180] [Transparent object] Next, the specific configuration of the transparent body 50 will be explained using Figures 12, 13, and 14, with appropriate reference to Figure 1.

[0181] Figure 12 is a schematic perspective view showing the maximum angle ωo of the principal ray passing through the second rectangular region 20 of the optical system 1 according to this embodiment, and the angle ωi of the principal ray passing through the second surface 52 of the transparent body 50. Figure 13 is a schematic perspective view showing the passage regions of the principal ray on the first surface 51 and the second surface 52 of the transparent body 50 according to this embodiment. Figure 14 is a schematic cross-sectional view showing the optical path length of the principal ray within the transparent body 50 according to this embodiment.

[0182] As shown in Figures 12 to 14, the transparent body 50 has a first surface 51 containing the second rectangular region 20 and a second surface 52. The transparent body 50 has a flattened shape, for example, with the first surface 51 and the surface opposite the first surface 51 as its main surfaces.

[0183] In this embodiment, as shown in Figure 12, the principal ray passing through the second rectangular region 20 also passes through the second surface 52. That is, the first transmitting surface 41 of the prism 40 is positioned to face the second surface 52. For example, when viewed from the direction normal to the second rectangular region 20, the first transmitting surface 41 is positioned so as not to overlap the second rectangular region 20 with the first surface 51 of the transparent body 50.

[0184] Figure 12 shows the principal ray 91 that passes through the second rectangular region 20 and has the maximum angle of incidence (or exit angle) with respect to the second rectangular region 20, represented by a solid line. The maximum angle ωo in Figure 12 is the maximum angle of the principal ray passing through the second rectangular region 20, that is, the maximum angle of incidence (or exit angle) of the principal ray 91 with respect to the second rectangular region 20. Angle ωi is the angle at which the principal ray 91 passes through the second surface 52. Specifically, angle ωi is the exit angle of the principal ray 91 from the second rectangular region 20 with respect to the second surface 52, or the angle of incidence of the principal ray 91 incident on the second rectangular region 20 with respect to the second surface 52.

[0185] In this case, the optical system 1 according to this embodiment satisfies the following condition (a).

[0186] ωi<ωo···(a)

[0187] This makes it possible to achieve both a wider angle and a thinner optical system 1. When the optical system 1 is used in an imaging device, reflections on the second surface 52 can be reduced.

[0188] The maximum angle ωo is, for example, greater than 65 degrees. This makes it possible to reduce the height of the optical system 1 while increasing the size of the second rectangular region 20. Preferably, the maximum angle ωo may be greater than 70 degrees.

[0189] The angle ωi is, for example, less than 30 degrees. This suppresses reflection at the second surface 52. Preferably, the angle ωi may be less than 20 degrees.

[0190] In Figure 13, the principal ray passing through the second rectangular region 20 represents the region 22 passing through the second surface 52, which is shown as a dotted shade. The shape of region 22 is trapezoidal. Also in Figure 13, lengths H1o, H2o, and Vo related to the second rectangular region 20 are represented by double-headed arrows. Lengths H1i, H2i, and Vi related to region 22 are also represented by double-headed arrows.

[0191] Length H1o is the distance between two points on the first surface 51 through which the principal rays that image at both ends of the first side 11 of the first rectangular region 10 pass. The ends of the first side 11 are the second point 102 and the fourth point 104, respectively, as shown in Figure 5. Length H1o is the distance between the eighth point 202 and the tenth point 204 of the second rectangular region 20, which correspond to the second point 102 and the fourth point 104, respectively.

[0192] Length H2o is the distance between two points on the first surface 51 through which the principal rays that image at both ends of the second side 12 of the first rectangular region 10 pass. The ends of the second side 12 are the third point 103 and the fifth point 105, respectively, as shown in Figure 5. Length H2o is the distance between the ninth point 203 and the eleventh point 205 of the second rectangular region 20, which correspond to the third point 103 and the fifth point 105, respectively.

[0193] Length Vo is the distance between two points on the first surface 51 through which the principal rays that image at each end of the center line segment connecting the centers of the first side 11 and the second side 12 of the first rectangular region 10 pass. As shown in Figure 5, the center of the first side 11 is the first point 101, and the center of the second side 12 is the sixth point 106.

[0194] Length H1i is the distance between two points on the second surface 52 through which the principal rays that image at both ends of the first side 11 of the first rectangular region 10 pass.

[0195] H2i is the distance between two points on the second surface 52 through which the principal rays that image at both ends of the second side 12 of the first rectangular region 10 pass.

[0196] Length Vi is the distance between two points on the second surface 52 through which the principal rays that image at each end of the line segment connecting the centers of the first side 11 and the second side 12 of the first rectangular region 10 pass.

[0197] As described above, when lengths H1o, H2o, Vo, H1i, H2i, and Vi are defined, the optical system 1 according to this embodiment satisfies the following condition (b1).

[0198] H1o / H1i × Vi / Vo > 0.1 ···(b1)

[0199] This allows for a larger second rectangular region 20 to be secured. When the optical system 1 is used as an imaging device, sufficient light can be extracted from the back of the transparent body 50.

[0200] Furthermore, optical system 1 may satisfy the following condition (b2).

[0201] H1o / H1i × Vi / Vo < 0.4 ···(b2)

[0202] This makes it possible to reduce the height of the transparent body 50. Preferably, the following conditions (b3) or (b4) may also be met.

[0203] H1o / H1i × Vi / Vo > 0.15 ···(b3) H1o / H1i × Vi / Vo < 0.3 ···(b4)

[0204] Furthermore, optical system 1 satisfies the following condition (c1).

[0205] H1o / H1i×H2i / H2o>0.1···(c1)

[0206] This allows for a larger second rectangular region 20 to be secured. When the optical system 1 is used as an imaging device, sufficient light can be extracted from the back of the transparent body 50.

[0207] Furthermore, optical system 1 may satisfy the following condition (c2).

[0208] H1o / H1i×H2i / H2o<0.4···(c2)

[0209] This makes it possible to reduce the height of the transparent body 50. Preferably, the following conditions (c3) or (c4) may also be met.

[0210] H1o / H1i×H2i / H2o>0.15···(c3) H1o / H1i×H2i / H2o<0.35 (c4)

[0211] Figure 14 shows the principal ray 92 passing through the first point 101 of the first rectangular region 10 and the seventh point 201 of the second rectangular region 20, and the principal ray 93 passing through the sixth point 106 of the first rectangular region 10 and the twelfth point 206 of the second rectangular region 20. Here, the optical path length of the principal ray 92 within the transparent body 50 is defined as La. The optical path length of the principal ray 93 within the transparent body 50 is defined as Lb. In this case, the following condition (g) is satisfied.

[0212] 5 <Lb / La<15···(g)

[0213] This makes it possible to enlarge the second rectangular region 20 while simultaneously making the transparent body 50 thinner. In other words, it is possible to extract light from the back of the transparent body 50 with sufficient light intensity, or to deliver sufficient light intensity to the back of the transparent body 50.

[0214] Note that the incident angle width or exit angle width of the principal ray 92 differs depending on whether it is incident on or exits the first point 101 or the seventh point 201. Below, we will explain using Figures 15 and 16, with the example of the optical system 1 utilizing an imaging device.

[0215] Figure 15 is a schematic plan view showing the principal ray 92 incident on the first point 101, which is the closest to the optical axis 60 among the four sides of the first rectangular region 10 at the reduced conjugate point of the optical system 1 according to this embodiment. The incident angle θi shown in Figure 15 is the width of the incident angle formed by the principal ray 92 incident on the first point 101 in a plane that passes through the first side 11 and is parallel to both the first side 11 and the optical axis 60.

[0216] In Figure 15, a translucent flat plate cover member is placed between the lens 30 and the first rectangular region 10, but this member does not have a lens function.

[0217] Figure 16 is a schematic cross-sectional view showing the angle when the principal ray 92 shown in Figure 15 is incident on the second rectangular region 20 at the enlarged conjugate point of the optical system 1 according to this embodiment. The angle θo shown in Figure 16 is the angle made when the principal ray 92 that forms the incident angle θi is emitted from the seventh point 201.

[0218] In this case, the angle θo is smaller than the angle of incidence θi. Specifically, the optical system 1 according to this embodiment satisfies the following condition (k).

[0219] 0.1 < θo / θi < 0.3 ···(k)

[0220] This makes it possible to enlarge the second rectangular region 20 while miniaturizing the optical system 1.

[0221] In this embodiment, as shown in Figure 16, the second surface 52 is inclined with respect to the first surface 51. The inclination angle φ is greater than 45 degrees and less than 85 degrees. The inclination of the second surface 52 suppresses the angle of light emission from the second surface 52 when the optical system 1 is used in an imaging device.

[0222] The transparent body 50 is formed using, for example, a homogeneous transparent material, but is not limited thereto. The transparent body 50 may be formed using multiple different materials. Below, variations of the transparent body that can be used instead of the transparent body 50 will be described with reference to Figure 17.

[0223] Figure 17 is a schematic perspective view showing a modified example of a transparent body. The transparent body 350 shown in Figure 17 comprises a first medium 351 having a first surface 51 and a flat second medium 352 having a second surface 52. The second surface 52 is in contact with air.

[0224] The first medium 351 is the main body of the transparent body 350 and has a flat shape with a first surface 51 and the surface opposite to the first surface 51 as its main surfaces. The first medium 351 is formed using a resin material such as silicone or urethane.

[0225] The second medium 352 is in contact with the first medium 351. Specifically, the surface of the second medium 352 opposite to the second surface 52 is in contact with the first medium 351. The second medium 352 is, for example, a cover glass, but is not limited to this. The second medium 352 may also be a transparent resin plate.

[0226] The first medium 351 and the second medium 352 are each formed using materials that are transparent to visible light. The first medium 351 and the second medium 352 have different refractive indices. Here, the refractive index of the first medium 351 is defined as n1, and the refractive index of the second medium 352 is defined as n2. In this case, the transparent body 350 satisfies the following condition (e).

[0227] n1 <n2···(e)

[0228] For example, the refractive index n2 is greater than 1.45. This helps to suppress field curvature. Also, the refractive index n1 is greater than 1.3 and less than 1.5. Having a refractive index n1 greater than 1.3 helps to suppress reflection loss at the interface between the first medium 351 and the second medium 352. Furthermore, having a refractive index n2 less than 1.5 allows for a larger field of view.

[0229] In this modified example, the first medium 351 is flexible. Specifically, the first medium 351 is formed from a material that is soft enough to be easily deformed by hand. The second medium 352 is harder than the first medium 351.

[0230] Here, we define the Young's modulus of the first medium 351 as E1 and the Young's modulus of the second medium 352 as E2. In this case, the transparent body 350 satisfies the following condition (f).

[0231] E1 <E2···(f)

[0232] For example, the Young's modulus E1 is greater than 0.01 MPa and less than 3 MPa. This allows the shape of the first medium 351 to be easily changed. For example, the first medium 351 deforms when touched by a person or when it comes into contact with another object. When the optical system 1 is used as an imaging device, the deformation of the first surface 51 and the second rectangular region 20 allows for the capture of these shape changes.

[0233] Furthermore, for example, the Young's modulus E2 is greater than 400 MPa and less than 200,000 MPa (200 GPa). This suppresses the change in shape of the second medium 352 even when the first medium 351 is deformed. The second surface 52 of the second medium 352 functions as the light emission surface from the transparent body 350 when the optical system 1 is used as an imaging device. Since the shape of this emission surface can be kept constant without changing, the change in shape of the first surface 51 can be captured. When the optical system 1 is used as an image projection device, the second surface 52 functions as the light incidence surface to the transparent body 350, so the projected image can be stabilized.

[0234] [Examples] Below, we will describe specific examples 1 to 5 of the optical system 1 described above.

[0235] Figure 18 is a plan view showing the principal rays passing through the optical system according to Example 1. Similarly, the principal rays passing through the optical systems according to Example 2 and Example 3 are represented in plan views equivalent to those in Figure 18. In all three optical systems according to Example 1, Example 2, and Example 3, similar to optical system 1 shown in Figure 1, the second rectangular region 20 is positioned so that it does not overlap with the optical axis 60 when viewed from the front.

[0236] Figure 19 is a side view showing the principal ray passing through the optical system according to Example 5. In the optical system according to Example 5, when the second rectangular region 20 is viewed from the front, the second rectangular region 20 and the first rectangular region 10 are positioned so that they overlap with the optical axis 60. That is, they are arranged in a line from the first rectangular region 10 to the second rectangular region 20 along the direction in which the optical axis 60 extends. The optical system according to Example 4 is the same as that according to Example 5.

[0237] As shown in Figure 18, among the multiple lenses 30, the lens 31 closest to the first rectangular region 10 may be a D-cut lens. Specifically, the lens 31 may have a D-cut on the side that does not include the optical axis 60 in a direction perpendicular to the first side 11. For example, the lens 31 has a plane parallel to the yz plane on the positive x-axis side. This enables miniaturization of the optical system. In Figure 18, a translucent flat plate cover member is placed between the lens 31 and the first rectangular region 10, but this member does not have a lens function. This cover member is the same as the one shown in Figure 15.

[0238] The following describes specific numerical examples for each of Examples 1 to 5.

[0239] In the tables below, the unit of length is "mm". The unit of field of view is "degrees". In each embodiment, each of the multiple surfaces that affect the light rays is assigned a surface number. The surface numbers are assigned in ascending order from the magnification side (second rectangular region 20) to the reduction side (first rectangular region 10). In each embodiment, the surface type, Y radius of curvature (radius of curvature in the y-axis direction), conic coefficient, surface spacing, nd (refractive index for the d line), vd (Abbe number for the d line), and eccentricity data are shown. The eccentricity data shows the displacement amounts X, Y, Z of the symmetric surface relative to the previous surface of the optical system, and the normal directions α, β, and γ of the symmetric surface relative to the previous surface.

[0240] In each embodiment, it is assumed that the optical system is used in an imaging device. That is, in each table, "object" refers to the object surface, i.e., the second rectangular region 20. "Image" refers to the imaging surface, i.e., the first rectangular region 10.

[0241] The freeform surface shape is defined by the following equation, using a local Cartesian coordinate system (x,y,z) with the vertices of the surface as the origin.

[0242]

number

[0243] Here, z is the amount of sag of a plane parallel to the z-axis. r is the radial distance, i.e., the square root of (x

[0249] , 2 + y 2 ). c is the curvature at the vertex of the surface. k is the conic coefficient. C j is the coefficient of the monomial x m y n .

[0244] Hereinafter, the coefficients of the i-th term of x and the j-th term of y in the polynomial representing the free-form surface shape are arranged vertically for x i from i = 0 to i = 10, and horizontally for y j from j = 0 to j = 10, and are represented using a table (for example, Table 3, etc.). Specifically, the intersection of each row and each column represents the coefficient of the corresponding term. For example, the numerical value corresponding to the intersection of the row of "x 2 " and the column of "y" is the coefficient of x 2 y.

[0245] (Example 1) Table 1 shows the data of the main surfaces of the optical system according to Example 1.

[0246] [Table 1]

[0247] The aperture diameter is 0.55 mm. Table 2 shows the minimum and maximum values of the size of the image formed in the first rectangular region 10.

[0248] [Table 2]

[0249] The optical system according to Example 1 includes, as a plurality of lenses 30, a first lens, a second lens, a third lens, a fourth lens, and a fifth lens in this order from the magnifying side to the reducing side. An aperture is disposed between the third lens and the fourth lens. Also, in the optical system according to Example 1, a cover glass is disposed between the fifth lens and the reduction conjugate point.

[0250] In Example 1, the shape of the first lens is biconcave. The shape of the second lens is biconvex. The shape of the third lens is biconvex. The shape of the fourth lens is a negative meniscus shape that is convex toward the first rectangular region 10. The shape of the fifth lens is biconvex.

[0251] As shown in Table 1, in Example 1, surface 4 is the first transmission surface 41. Surface 6 is the first reflection surface 42. Surface 10 is the second reflection surface 43. Surface 13 is the second transmission surface 44. Surface 14 is the first surface of the first lens. Surface 15 is the second surface of the first lens. Surface 16 is the first surface of the second lens. Surface 17 is the second surface of the second lens. Surface 18 is the first surface of the third lens. Surface 19 is the second surface of the third lens. Surface 20 is the aperture. Surface 21 is the first surface of the fourth lens. Surface 22 is the second surface of the fourth lens. Surface 23 is the first surface of the fifth lens. Surface 24 is the second surface of the fifth lens. Surface 25 is the first surface of the cover glass. Surface 26 is the second surface of the cover glass.

[0252] Surfaces 1, 2, 3, 5, 7, 8, 9, 11, and 12 are hypothetical surfaces used to set eccentricity and / or spacing. Furthermore, in each lens and cover glass, the first and second surfaces are opposite each other, with one functioning as the light incidence surface and the other as the light emission surface.

[0253] The shape data for faces 4, 10, and 13, which have freeform shapes, are shown in Tables 3, 4, and 5, respectively. In each table, terms that do not have a combination are crossed out. Also, since there are no terms where the exponent of y is 5 or greater and the exponent of x is 6 or greater, the tables for these terms are not shown. The same applies to the other tables.

[0254] [Table 3]

[0255] [Table 4]

[0256] [Table 5]

[0257] (Example 2) Data of the main surfaces of the optical system according to Example 2 are shown in Table 6.

[0258] [Table 6]

[0259] The aperture diameter is 0.6 mm. Table 7 shows the minimum and maximum values of the size of the image formed in the first rectangular region 10.

[0260] [Table 7]

[0261] The optical system according to Example 2 includes, as a plurality of lenses 30, a first lens, a second lens, a third lens, a fourth lens, and a fifth lens in this order from the magnifying side to the reducing side. An aperture is disposed between the third lens and the fourth lens.

[0262] In Example 2, the shape of the first lens is a negative meniscus shape convex toward the first rectangular region 10. The shape of the second lens is a biconvex shape. The shape of the third lens is a biconvex shape. The shape of the fourth lens is a biconcave shape. The shape of the fifth lens is a biconvex shape.

[0263] As shown in Table 6, in Example 2, surface 4 is the first transmission surface 41. Surface 6 is the first reflection surface 42. Surface 10 is the second reflection surface 43. Surface 13 is the second transmission surface 44. Surface 14 is the first surface of the first lens. Surface 15 is the second surface of the first lens. Surface 16 is the first surface of the second lens. Surface 17 is the second surface of the second lens. Surface 18 is the first surface of the third lens. Surface 19 is the second surface of the third lens. Surface 20 is the aperture. Surface 21 is the first surface of the fourth lens. Surface 22 is the second surface of the fourth lens. Surface 23 is the first surface of the fifth lens. Surface 24 is the second surface of the fifth lens. Note that surfaces 1, 2, 3, 5, 7, 8, 9, 11, 12, and 25 are virtual surfaces used to set eccentricity and / or spacing.

[0264] Of these, the shape data for faces 4, 10, and 13, which have freeform surface shapes, are shown in Tables 8, 9, and 10, respectively.

[0265] [Table 8]

[0266] [Table 9]

[0267] [Table 10]

[0268] (Example 3) Table 11 shows the data for the main surfaces of the optical system in Example 3.

[0269] [Table 11]

[0270] The aperture diameter is 0.6 mm. Table 12 shows the minimum and maximum sizes of the image formed in the first rectangular region 10.

[0271] [Table 12]

[0272] The optical system according to Embodiment 3 includes a plurality of lenses 30, arranged in the order of a first lens, a second lens, a third lens, a fourth lens, and a fifth lens, from the magnification side to the reduction side. An aperture is positioned between the third lens and the fourth lens.

[0273] In Example 3, the shape of the first lens is a negative meniscus shape that is convex toward the first rectangular region 10. The shape of the second lens is a biconvex shape. The shape of the third lens is a biconvex shape. The shape of the fourth lens is a negative meniscus shape that is convex toward the first rectangular region 10. The shape of the fifth lens is a biconvex shape.

[0274] As shown in Table 11, in Example 3, surface 4 is the first transmission surface 41. Surface 6 is the first reflection surface 42. Surface 10 is the second reflection surface 43. Surface 13 is the second transmission surface 44. Surface 14 is the first surface of the first lens. Surface 15 is the second surface of the first lens. Surface 16 is the first surface of the second lens. Surface 17 is the second surface of the second lens. Surface 18 is the first surface of the third lens. Surface 19 is the second surface of the third lens. Surface 20 is the aperture. Surface 21 is the first surface of the fourth lens. Surface 22 is the second surface of the fourth lens. Surface 23 is the first surface of the fifth lens. Surface 24 is the second surface of the fifth lens. Note that surfaces 1, 2, 3, 5, 7, 8, 9, 11, 12, and 25 are virtual surfaces used to set eccentricity and / or spacing.

[0275] Of these, the shape data for faces 4, 10, and 13, which have freeform surface shapes, are shown in Tables 13, 14, and 15, respectively.

[0276] [Table 13]

[0277] [Table 14]

[0278] [Table 15]

[0279] (Example 4) Table 16 shows the data for the main surfaces of the optical system in Example 4.

[0280] [Table 16]

[0281] The aperture diameter is 0.65 mm. Table 17 shows the minimum and maximum sizes of the image formed in the first rectangular region 10.

[0282] [Table 17]

[0283] The optical system according to Embodiment 4 includes a plurality of lenses 30, arranged in the order of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens, from the magnification side to the reduction side. An aperture is positioned between the third lens and the fourth lens. A reflective mirror is positioned between the fourth lens and the fifth lens.

[0284] In Example 4, the shape of the first lens is biconcave. The shape of the second lens is biconvex. The shape of the third lens is biconvex. The shape of the fourth lens is a negative meniscus shape that is convex toward the first rectangular region 10. The shape of the fifth lens is a negative meniscus shape that is convex toward the first rectangular region 10. The shape of the sixth lens is a positive meniscus shape that is convex toward the first rectangular region 10.

[0285] As shown in Table 16, in Example 4, surface 4 is the first transmissive surface 41. Surface 6 is the first reflective surface 42. Surface 10 is the second reflective surface 43. Surface 13 is the second transmissive surface 44. Surface 14 is the first surface of the first lens. Surface 15 is the second surface of the first lens. Surface 16 is the first surface of the second lens. Surface 17 is the second surface of the second lens. Surface 18 is the first surface of the third lens. Surface 19 is the second surface of the third lens. Surface 20 is the aperture. Surface 21 is the first surface of the fourth lens. Surface 22 is the second surface of the fourth lens. Surface 27 is the first surface of the fifth lens. Surface 28 is the second surface of the fifth lens. Surface 29 is the first surface of the sixth lens. Surface 30 is the second surface of the sixth lens. Note that surfaces 1, 2, 3, 5, 7, 8, 9, 11, 12, 23, 24, 25, and 26 are virtual surfaces used to set eccentricity and / or spacing.

[0286] Of these, the shape data for faces 4, 10, and 13, which have freeform surface shapes, are shown in Tables 18, 19, and 20, respectively.

[0287] [Table 18]

[0288] [Table 19]

[0289] [Table 20]

[0290] (Example 5) Table 21 shows the data for the main surfaces of the optical system according to Example 5.

[0291] [Table 21]

[0292] The aperture diameter is 1.04 mm. The minimum and maximum sizes of the image formed in the first rectangular region 10 are shown in Table 22.

[0293] [Table 22]

[0294] The optical system according to Embodiment 5 includes a plurality of lenses 30, arranged in the order of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens, from the magnification side to the reduction side. An aperture is positioned between the fourth lens and the fifth lens.

[0295] In Example 5, the shape of the first lens is biconcave. The shape of the second lens is a positive meniscus shape that is convex toward the first rectangular region 10. The shape of the third lens is a positive meniscus shape that is convex toward the first rectangular region 10. The shape of the fourth lens is biconvex. The shape of the fifth lens is biconcave. The shape of the sixth lens is biconvex. The shape of the seventh lens is biconvex.

[0296] As shown in Table 21, in Example 5, surface 10 is the second reflective surface 43. Surface 13 is the second transmissive surface 44. Surface 14 is the first surface of the first lens. Surface 15 is the second surface of the first lens. Surface 16 is the first surface of the second lens. Surface 17 is the second surface of the second lens. Surface 18 is the first surface of the third lens. Surface 19 is the second surface of the third lens. Surface 20 is the first surface of the fourth lens. Surface 21 is the second surface of the fourth lens. Surface 22 is the aperture. Surface 23 is the first surface of the fifth lens. Surface 24 is the second surface of the fifth lens. Surface 25 is the first surface of the sixth lens. Surface 26 is the second surface of the sixth lens. Surface 27 is the first surface of the seventh lens. Surface 28 is the second surface of the seventh lens. Note that surfaces 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, and 29 are virtual surfaces used to set eccentricity and / or spacing.

[0297] Of these, the shape data for surfaces 10 and 13, which have a freeform surface shape, are shown in Tables 23 and 24, respectively. In other words, in this embodiment, there are only two surfaces with a freeform surface shape.

[0298] [Table 23]

[0299] [Table 24]

[0300] In this embodiment, as shown in Table 21, surfaces 27 and 28 are aspherical. Surfaces 27 and 28 are either the incident or exit surface of one of the multiple lenses 30, respectively. The shape data of surfaces 27 and 28, which have an aspherical shape, are shown in Table 25.

[0301] [Table 25]

[0302] The shape of an aspherical surface is defined by the following equation.

[0303]

number

[0304] Here, z is the sag of the plane parallel to the z-axis. r is the radial distance, i.e., (x 2 +y 2 It is the square root of ). c is the curvature at the vertex of the face. k is the conic coefficient. A, B, C, and D are the coefficients of the 4th, 6th, 8th, and 10th orders of r, respectively.

[0305] (Various parameters) Table 26 shows the various parameters of the optical systems according to Examples 1 to 5. These parameters are related to conditions (a) to (k) described in the embodiments. Note that Young's moduli E1 and E2 related to condition (f) are omitted because they do not affect the optical characteristics.

[0306] [Table 26]

[0307] (MTF characteristics) Here, the MTF (Modulation Transfer Function) characteristics of the optical systems according to Examples 1 to 5 will be explained.

[0308] Figures 20 to 24 show the MTF (Modulation Transfer Function) characteristics of the optical systems according to Examples 1 to 5, respectively. In each figure, the horizontal axis represents the amount of defocus (unit: mm), and the vertical axis represents the contrast ratio. The dashed lines in the figures represent the MTF characteristics in the x-axis direction. The solid lines represent the MTF characteristics in the y-axis direction. The MTF characteristics were obtained at a spatial frequency of 60 lines / 1 mm. In each figure, four types of graphs (f1, f2, f3, f4) for each image height are shown for both the x-axis and y-axis directions. The image height is represented by the position within the first rectangular region 10. The specific values ​​of f1 to f4 are shown in Table 27.

[0309] [Table 27]

[0310] Here, f1 is the position closest to the optical axis 60 of the first rectangular region 10, i.e., the first point 101. The first rectangular region 10 is shown with an x-coordinate in the range of -0.758 to +0.758 and a y-coordinate in the range of 0 to -0.2688. Since there is a symmetrical relationship between the negative and positive directions of the x-axis, only the case where the x-coordinate is in the positive range is shown.

[0311] In each embodiment, the MTF characteristics shown in each figure indicate that the difference in contrast ratio peaks for each image height is small. In other words, the optical system in each embodiment exhibits reduced field curvature.

[0312] [Imaging device] Next, we will describe specific application examples of the optical system 1 according to the above-described embodiment. First, we will describe an imaging device equipped with the optical system 1 using Figure 25. Figure 25 is a block diagram showing an example of an imaging device 400 equipped with the optical system 1 according to this embodiment.

[0313] The imaging device 400 shown in Figure 25 photographs the subject 401. The imaging device 400 comprises an optical system 1, a control unit 410, and an image sensor 420.

[0314] The control unit 410 controls the entire imaging device 400 and its various components, such as the image sensor 420. The control unit 410 is, for example, a CPU (Central Processing Unit) or a microprocessor. The control unit 410 includes one or more memories and input / output ports. For example, the control unit 410 includes, for example, a non-volatile memory on which a control program is stored, and a volatile memory which is the execution area for the program.

[0315] The image sensor 420 is a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor, etc. The imaging surface of the image sensor 420 is positioned in the first rectangular region 10. The image sensor 420 receives light incident on the first rectangular region 10 via the optical system 1 and converts it into an electrical image signal.

[0316] As a result, as described above, the optical system 1 is miniaturized, which also makes it possible to miniaturize the imaging device 400.

[0317] The imaging device 400 is used as a contact sensor, tactile sensor, fingerprint sensor, or sensing camera to detect contact between the subject 401 and the transparent body 50 of the optical system 1. By applying this, the imaging device 400 can also be applied to a robotic hand.

[0318] Alternatively, the imaging device 400 is not limited to contact-type imaging and can be used as a road surface sensor for detecting road surface conditions, etc. For example, the imaging device 400 can be used in autonomous vehicles. In this case, the optical system 1 of the imaging device 400 does not need to include a transparent body 50.

[0319] [Image projection device] Next, an image projection device equipped with the optical system 1 will be described using Figure 26. Figure 26 is a block diagram showing an example of an image projection device 500 equipped with the optical system 1 according to this embodiment.

[0320] The image projection device 500 shown in Figure 26 projects an image (or video) onto a screen 501. The image projection device 500 comprises an optical system 1, a control unit 510, a light source 520, and an image forming element 530.

[0321] The control unit 510 controls the entire image projection device 500, as well as its various components, such as the light source 520 and the image forming element 530. The control unit 510 is, for example, a CPU or microprocessor. The control unit 510 includes one or more memories and input / output ports. For example, the control unit 510 includes, for example, a non-volatile memory on which a control program is stored, and a volatile memory which is the execution area for the program.

[0322] The light source 520 includes a solid-state light-emitting element such as an LED (Light Emitting Device) or a laser element. The light source 520 includes, for example, a phosphor and generates and outputs desired visible light (e.g., RGB).

[0323] The image forming element 530 includes an optical component such as a liquid crystal or a DMD (Digital Mirror Device). For example, the image forming element 530 is a DLP (Digital Light Processing) substrate equipped with a DMD. The image forming element 530 generates an image (or video) using visible light from the light source 520. The image forming surface of the image forming element 530 is positioned in the first rectangular region 10. The image forming element 530 directs the light emitted from the first rectangular region 10 toward the screen 501 via the optical system 1.

[0324] As a result, as described above, the optical system 1 is miniaturized, which also makes it possible to miniaturize the image projection device 500.

[0325] The image projection device 500 is, for example, a projector, but is not limited thereto. For example, the image projection device 500 may be a transparent display device that projects onto a window glass as a display surface, or a head-up display, etc.

[0326] (Other embodiments) Although optical systems, imaging devices, and image projection devices relating to one or more embodiments have been described above based on embodiments, this disclosure is not limited to these embodiments. Without departing from the spirit of this disclosure, various modifications to these embodiments that a person skilled in the art could conceive, as well as configurations constructed by combining components from different embodiments, are also included within the scope of this disclosure.

[0327] For example, in the above embodiment, the first reflective surface 42 does not have to be a plane. For example, the first reflective surface 42 may have a free-form shape.

[0328] Furthermore, for example, the first rectangular region 10 and the second rectangular region 20 may each be squares. Also, the first rectangular region 10 and the second rectangular region 20 do not have to be rectangles in the strict sense, the lengths of the two opposite sides may be different, and they do not have to be parallel. In this case, the difference in length may be, for example, a few percent of the side length. Also, the angle between the two sides may be in the range of about ±5 degrees. Also, each side does not have to be a straight line, but may be curved. If the side is curved, the amount of deviation from the straight line connecting the two vertices is, for example, within a few tens of percent of the distance between the two vertices. Also, the second rectangular region 20 does not have to be a perfect plane, but may be concave or convex. If the second rectangular region 20 is not a plane, the amount of deviation from the plane is, for example, within a few percent of the length of the line segment (for example, diagonal or side) connecting the two vertices of the second rectangular region 20.

[0329] Furthermore, as shown in Example 5, for example, the first transmission surface of the prism does not have to be a free-form surface. Also, the placement of the main surface of the optical system 1 in either the first space 71 or the second space 72 may be appropriately adjusted by providing additional reflective surfaces, etc. Similarly, the placement of the main surface of the optical system 1 in either the third space 81 or the fourth space 82 may be appropriately adjusted by providing additional reflective surfaces, etc.

[0330] Furthermore, for example, the optical system 1 may have, instead of the prism 40, a transparent member having a first transmission surface 41, a reflective mirror having a first reflective surface 42, a reflective mirror having a second reflective surface 43, and a transparent member having a second transmission surface 44. In other words, each surface may be composed of individual optical components rather than being made up of an integrated prism.

[0331] Furthermore, each of the above embodiments may be modified, replaced, added, or omitted in various ways within the scope of the claims or equivalent thereof. [Industrial applicability]

[0332] This disclosure can be used as a small or low-profile optical system, for example, in imaging devices and image projection devices. [Explanation of Symbols]

[0333] 1 Optical system 10. First rectangular region (imaging plane) 11. First side 12. Second side 13 Third side 14. Fourth side 20 Second rectangular area (object plane) 22 areas 30, 31 lenses 40 prisms 41 1st transmission surface 42 1st reflective surface 43 Second reflective surface 44 2nd transmission surface 50, 350 transparent body 51 Page 1 52 2nd page 60 Optical axis 61 Reference axis 70 1st plane 71 1st space 72 Second space 80 2nd plane 81 Third space 82 4th space 90 Intermediate imaging position 91, 92, 93 Main rays 101 1st point 102 Second point 103 3rd point 104 4th point 105 5th point 106 6th point 201 7th point 202 8th point 203 9th point 204 10th point 205 11th point 206 12th point 351 First medium 352 Second medium 400 Imaging device 401 Subject 410, 510 Control Unit 420 image sensors 500 Image Projection Device 501 screens 520 light source 530 Image forming elements

Claims

1. An optical system having a reduction conjugate point on the reduction side and an expansion conjugate point on the expansion side, Multiple lenses, The system comprises a prism provided on the magnifying side of the aforementioned plurality of lenses, The prism mentioned above is The first transparent surface is a free-form surface, The first reflective surface and The second reflective surface is a free-form surface, It has a second transparent surface, which is a free-form surface shape, located on the reduced side of the first transparent surface, The first rectangular region at the contracted conjugate point is, The imaging relationship is conjugate to the second rectangular region at the aforementioned enlarged conjugate point, The optical axis, which is the axis passing through the center of the most numerous lenses among the aforementioned multiple lenses, does not intersect with the optical axis. When the space in which the optical system is arranged is divided into a first space and a second space with a first plane as the boundary, which is a virtual plane perpendicular to the first rectangular region and passing through the optical axis, and which is parallel to the first side of the first rectangular region that has the shortest distance to the optical axis, All principal rays passing through the first rectangular region pass through the first rectangular region, the first transmissive surface and the first reflective surface in the first space, and pass through the second reflective surface and the second transmissive surface in the second space. When the space is divided into a third space and a fourth space with a second plane, which is a virtual plane passing through the optical axis and perpendicular to the first plane, All principal rays passing through the first rectangular region pass through the second rectangular region and the first transmissive surface in the third space. optical system.

2. The first transmissive surface causes the principal ray passing through the first point, which is the point closest to the optical axis on the first side of the first rectangular region that has the shortest distance to the optical axis, to diverge in a direction parallel to the optical axis and converge in a direction perpendicular to the optical axis. The optical system according to claim 1.

3. The second transmissive surface causes the principal ray passing through the first point, which is the point closest to the optical axis on the first side of the first rectangular region that has the shortest distance to the optical axis, to diverge in a direction parallel to the first side and converge in a direction perpendicular to the first side. The optical system according to claim 1 or 2.

4. The converging effect of the second reflective surface on the principal ray passing through the first point, which is the point closest to the optical axis on the first side of the first rectangular region that has the shortest distance to the optical axis, is greater in the direction parallel to the first side than in the direction perpendicular to the first side. The optical system according to any one of claims 1 to 3.

5. Having an intermediate imaging position that is conjugate to each of the aforementioned reduction conjugate point and the aforementioned expansion conjugate point, The aforementioned intermediate imaging position is located between the second reflective surface and the second transmissive surface. The optical system according to any one of claims 1 to 4.

6. The optical system according to any one of claims 1 to 5, wherein the following condition (d) is satisfied when the point on the first side furthest from the second rectangular region is designated as the second point, the point on the first side closest to the second rectangular region is designated as the fourth point, the point on the second side parallel to the first side of the first rectangular region furthest from the second rectangular region is designated as the third point, and the point on the second side closest to the second rectangular region is designated as the fifth point. i1<i2<i3<i4...(d) Here, i1: The angle of incidence when the principal ray passing through the second point is incident on the first reflecting surface. i2: The angle of incidence when the principal ray passing through the third point is incident on the first reflecting surface. i3: The angle of incidence when the principal ray passing through the fourth point is incident on the first reflecting surface. i4: The angle of incidence when the principal ray passing through the fifth point is incident on the first reflecting surface. That is the case.

7. A transparent body comprising a first surface including the second rectangular region and a second surface, The optical system allows principal rays to pass through the first rectangular region, the second surface, and the second rectangular region in that order or in the reverse order. The optical system according to claim 1.

8. The transparent body is A first medium having the first surface, A second medium is smaller than the first medium and is a flat plate having the second surface, The second surface is in contact with the air, The second medium has a surface opposite to the second surface adjacent to a surface different from the first surface of the first medium. The optical system according to claim 7.

9. The optical system according to claim 7, wherein the first point is the point closest to the optical axis on the first side of the first rectangular region that has the shortest distance to the optical axis, and the sixth point is the point closest to the optical axis on the second side of the first rectangular region that is parallel to the first side, and the following condition (g) is satisfied. 5<Lb / La<15...(g) Here, La: Optical path length of the principal ray passing through the first point within the transparent body. Lb: The optical path length of the principal ray passing through the sixth point within the transparent body. That is the case.

10. When a principal ray passing through the second rectangular region at the maximum angle with respect to the normal of the second rectangular region passes through the second surface, the angle between the principal ray and the normal of the second surface is less than 30 degrees. The optical system according to any one of claims 7 to 9.

11. The angle between the plane containing the second plane and the plane containing the first plane is greater than 45 degrees and less than 85 degrees. The optical system according to any one of claims 7 to 10.

12. The maximum angle of the principal ray passing through the second rectangular region is greater than 65 degrees. The optical system according to any one of claims 1 to 11.

13. The optical system according to any one of claims 1 to 7 and 9, satisfying the following condition (h). L1<L2...(h) Here, L1: The length of the first side of the first rectangular region that has the shortest distance to the optical axis among the four sides of the first rectangular region. L2: The length of the third side of the first rectangular region that is perpendicular to the first side. That is the case.

14. An optical system according to any one of claims 1 to 7, 9, and 13, satisfying the following condition (i): 0.1<d / D<0.3...(i) Here, d: The shortest distance between the first rectangular region and the optical axis, which is the first side of the four regions that has the shortest distance to the optical axis. D: The length of the third side of the first rectangular region that is perpendicular to the first side. That is the case.

15. The optical system according to any one of claims 1 to 7, 9, 13, and 14, wherein the first point closest to the optical axis is on the first side of the first rectangular region that has the shortest distance to the optical axis, and the seventh point is a point included in the second rectangular region that has an imaging relationship with the first point, and the following conditions (j1) and (j2) are satisfied. 5<X / d<20...(j1) 5<Y / d<20...(j2) Here, d: The shortest distance between the first rectangular region and the optical axis, which is the first side of the four regions that has the shortest distance to the optical axis. X: The distance between the first point and the seventh point along the direction parallel to the first side. Y: The distance between the first point and the seventh point along the direction perpendicular to the first side and the optical axis, respectively. That is the case.

16. An optical system according to any one of claims 1 to 15, The system comprises an image sensor that receives light passing through the optical system, Imaging device.

17. The imaging device according to claim 16, A light source that irradiates light toward the second rectangular region, and a device that detects contact with the second rectangular region, Optical contact sensor.

18. An optical system according to any one of claims 1 to 15, The system comprises an image forming element that projects an image onto a screen via the aforementioned optical system, Image projection device.

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