JP5030676B2 - Optical element, optical system including the same, and endoscope using the same - Google Patents

Description

  The present invention relates to an optical element, an optical system including the optical element, and an endoscope using the optical element, and in particular, has two optical paths, and includes an image on a rotational symmetry axis and two optical paths in a direction substantially orthogonal to the rotational symmetry axis. The present invention relates to an optical element to be combined and an imaging optical system or projection optical system that includes the optical element and has a function of forming an image as a circular and annular image on one imaging element.

Patent Document 1 discloses an imaging optical system in which a refractive optical system, a reflection optical system, and an imaging optical system are arranged and has two optical paths and can capture panoramic images and axial images. Similarly, there is Patent Document 2 as an endoscope having two optical paths. Further, there is Patent Document 3 as an endoscope that can observe all surrounding directions, and Patent Document 4 as a capsule endoscope that can observe all surrounding directions. Further, Patent Document 5 is an imaging apparatus capable of simultaneously imaging all surrounding directions and the front.
Special Table 2003-042743 US Patent Publication No. 2004-0254424 JP 60-42728 A JP 2001-174713 A JP 2002-341409 A

  However, the optical systems described in any of the patent documents cannot obtain an image with a small size and good resolution.

  The present invention has been made in view of such a situation in the prior art, and an object thereof is to display both an object point on the central axis and an omnidirectional image in a direction substantially orthogonal to the central axis with a simple configuration. It is an object to provide a small and inexpensive optical element capable of imaging on one imaging element at the same time, an optical system including the optical element, and an endoscope using the optical system.

An optical element of the present invention that achieves the above object comprises a transparent medium having a refractive index that is rotationally symmetric about a central axis and having a refractive index greater than 1. The transparent medium includes a first transmission surface and a central axis that is more central than the first transmission surface. A first reflecting surface disposed on the side, a second reflecting surface disposed on the opposite side of the image surface from the first reflecting surface, and a second transmitting surface disposed on the image surface side from the second reflecting surface; , a third transmission surface, anda fourth transmissive surface arranged on the image plane side of the third transmissive surface, the light beam incident on the transparent medium, and a direct view optical path to the side view optical path, In the order of forward ray tracing, the side viewing optical path enters the transparent medium through the first transmission surface, is reflected to the opposite side of the image surface by the first reflection surface, and is image side by the second reflection surface. A substantially Z-shaped optical path that is reflected from the transparent medium and exits from the transparent medium to the image plane side through the second transmission surface. Through the transmitting surface enters into the transparent medium, through the fourth transmitting surface constitutes a light path get outside the image plane side from the transparent medium, does not form an intermediate image at the direct view optical path and the side view optical path It is characterized by that.

  Further, the side viewing optical path is configured only on one side with respect to the central axis.

  Further, the second transmission surface is disposed in the vicinity of the central axis, the first reflection surface and the second reflection surface are disposed in the periphery thereof, and the first transmission surface is disposed in the outermost peripheral portion. And

  The first reflecting surface may be a surface having the same position and shape as the second transmitting surface.

  The first reflecting surface is a surface having the same position and shape as the fourth transmitting surface.

  The second reflecting surface is a surface having the same position and shape as the third transmitting surface.

  The first reflecting surface and the second reflecting surface have a total reflection function.

  The first transmission surface may be a cylindrical or conical surface.

  Further, at least one of the first reflecting surface and the second reflecting surface is composed of an extended rotation free-form surface formed by rotating an arbitrary-shaped line segment having no symmetry plane around the central axis. It is characterized by being.

  In addition, at least one of the surfaces of the transparent medium is formed of an extended rotation free-form surface that is formed by rotating an arbitrary-shaped line segment including an odd-numbered term around the central axis. .

  Furthermore, in the optical system including the optical element of the present invention, the direct-view optical path images or projects an object point near the central axis, and the side-view optical path images or projects an object point around the central axis. It is characterized by that.

  Further, the side viewing optical path and the direct viewing optical path share a part of the optical element, and a circular image of the direct viewing optical path and an annular image of the side viewing optical path on the outer periphery thereof are within the same plane. It is characterized by forming.

  The second reflecting surface may be disposed with a concave surface facing the opening.

  The first reflecting surface is disposed with a concave surface facing the opening.

When the outer shape of the optical element is D,
D <10mm
It satisfies the following condition.

When the outer shape of the image of the side viewing optical path is Dr,
D / Dr <2
It satisfies the following condition.

The first reflecting surface has a negative power, and the second reflecting surface has a positive power.

  Furthermore, an endoscope using the optical system is characterized.

  In the above optical system of the present invention, it is possible to obtain a compact optical system with good resolving power that can be observed in a different direction or projected an image in a different direction with a simple configuration and in which aberrations are well corrected.

  Hereinafter, an optical element of the present invention and an optical system including the optical element will be described based on examples.

  FIG. 3 is a cross-sectional view taken along the central axis (rotation symmetry axis) 2 of the optical system 1 of Example 1 described later. In the following description, the imaging optical system will be described. However, it can be used as a projection optical system with the optical path reversed.

  The optical system 1 according to the present invention includes a front group Gf having a negative power and rotational symmetry with respect to the central axis 2, an aperture S, and a rear group Gb having a positive power, and an intermediate image in the optical path. An optical system 1 that forms or projects an image without forming it.

  The optical system 1 according to the first embodiment includes a front group Gf that is rotationally symmetric about the central axis 2 and a rear group Gb that is rotationally symmetric about the central axis 2, and the first group Gf has a negative power. It is composed of a group G1 and a second group G2 which is an optical path synthesis optical system, and is composed of a third group G3 having a positive power as a rear group Gb on the back side of the aperture S, and a fourth group G4 having a positive power as a cemented lens. It is an optical system.

  In this embodiment, the second group G2 of the front group has a side viewing optical path A and a direct viewing optical path B, and the third group G3 and the fourth group G4 of the rear group Gb are aerial images synthesized by the second group G2. The image on the central axis 2 is formed in a circle around the center of the image by the direct-view optical path B, and the image of the different side-view optical path A is formed in an annular shape on the outer side. Have a work to do.

  The parallel flat plate arranged in the vicinity of the opening S acts as a filter F or the like. The plane parallel plate in the vicinity of the image plane 5 is a cover glass C of the image sensor.

  Also, by making the front group Gf negative and the rear group Gb positive, it becomes a so-called retrofocus type, which is particularly effective when a wide observation angle of view is desired with respect to the direct-view optical path B with respect to the object point on the central axis 2. It is.

  The optical element of the present invention is composed of a transparent medium L2 having a refractive index that is rotationally symmetric around the central axis 2 and greater than 1. The transparent medium L2 includes the first transmission surface 21 and the first transmission surface 21 on the central axis 2 side. The first reflecting surface 22 disposed on the first reflecting surface 22, the second reflecting surface 23 disposed on the opposite side of the image surface 5 with respect to the first reflecting surface 22, and the second reflecting surface 23 disposed on the image surface 5 side. The light beam incident on the transparent medium L2 has a second transmission surface 24, a third transmission surface 25, and a fourth transmission surface 26 disposed on the image plane 5 side of the third transmission surface 25. And the direct-view optical path B, and in the order of forward ray tracing, the side-view optical path A enters the transparent medium L2 through the first transmission surface 21, and is reflected by the first reflection surface 22 to the opposite side to the image surface 5. A substantially Z-shaped optical path is reflected from the second reflecting surface 23 toward the image surface 5 and passes through the second transmitting surface 24 to the outside from the transparent medium L2 toward the image surface 5. And direct view optical path B enters the third transmissive surface 25 through to the transparent medium L2, constituting the optical path get outside the image plane 5 side from the transparent medium L2 through the fourth transmissive surface 26.

  With this configuration, it is possible to make the incident angle of the side viewing optical path A to the first reflecting surface 22 and the second reflecting surface 23 relatively small, and it is possible to reduce the occurrence of decentration aberration generated on the reflecting surface. Become. In addition, the continuity of the image in the vicinity of the central axis 2 of the direct-view optical path B that captures the vicinity of the central axis 2 is maintained, and a smooth central image can be formed.

  Further, by configuring the side viewing optical path A only on one side of the central axis, the optical path in the optical element does not straddle the central axis 2, and the optical element can be made thin.

  In addition, the second transmission surface 24 is disposed in the vicinity of the central axis 2, the first reflection surface 22 and the second reflection surface 23 are disposed in the periphery thereof, and the first transmission surface 21 is disposed in the outermost periphery. The viewing optical path A is incident from a direction substantially perpendicular to the central axis 2 and can be configured to pass through the second transmission surface 24 after being reflected by the first reflection surface 22 and the second reflection surface 23, so that the first reflection is performed. It is possible to configure the surface 21 and the second reflecting surface 23 as inner reflecting surfaces. Further, by using an inner reflection surface, it is possible to reduce the occurrence of decentration aberrations.

  Further, the first reflective surface 22 and the second transmissive surface 24, the first reflective surface 22 and the fourth transmissive surface 26, and the second reflective surface 23 and the third transmissive surface 25 are configured at the same position and shape, respectively. This improves the manufacturing process. Since it is difficult to separate the light fluxes of the direct-view optical path B and the side-view optical path A on the surface on the aperture side, in particular, by making the first reflecting surface 22 and the second transmitting surface 24 in the same position and the same shape, It is possible to reduce the area that is not reflected.

  Further, since the first reflection surface 22 and the second reflection surface 23 have a total reflection function, it is not necessary to attach a reflection film, and the trial production becomes easy and the reflectance becomes 100%, so that a bright image can be taken.

  Further, the first transmission surface 21 is a cylindrical or conical surface, so that the optical element can be formed as a single unit, which is preferable in production.

  Further, at least one of the first reflecting surface 22 and the second reflecting surface 23 is constituted by an extended rotation free-form surface formed by rotating an arbitrary-shaped line segment having no symmetry plane around the central axis 2. By doing so, it becomes possible to correct the distortion around the angle of view.

  In addition, at least one of the surfaces of the transparent medium L2 is formed of an extended rotation free-form surface that is formed by rotating an arbitrary-shaped line segment including an odd-order term around the central axis 2. It is possible to give a vertically asymmetric shape with respect to the corner center, which is preferable in terms of aberration correction.

  Further, the optical system includes a front group Gf, a rear group Gb disposed on the image plane 5 side of the front group Gf, and an opening S disposed between the front group Gf and the rear group Gb. The direct-view optical path B captures or projects an object point near the central axis 2, and the side-view optical path A captures or projects an object point around the central axis 2. Image continuity is obtained, a clear image can be obtained, the direct-view optical path B and the side-view optical path A can be configured not to intersect, and the incident angle on the reflecting surface can be reduced. . Further, if the optical element is disposed around the opening S, the images of the direct-view optical path B and the side-view optical path A overlap each other. In addition, if it is arranged on the image plane 5 side with respect to the opening S, the number of optical elements that can be used for image formation decreases, and a clear image cannot be formed. By disposing on the object side from the opening S, it is possible to separate the image area formed by the direct-view optical path B and the side-view optical path A, and at the same time, the number of optical elements that can be shared by both optical paths is increased and a clear image can be formed. .

  The side-view optical path A and the direct-view optical path B share part of the optical elements, and form a circular image of the direct-view optical path B and an annular image of the outer side-view optical path A in the same plane. By doing so, it is possible to make the optical system compact, and it is possible to pick up both images with a single image sensor and to focus on the image at the same time.

  Moreover, since the 1st reflective surface 22 or the 2nd reflective surface 23 is arrange | positioned with the concave surface facing the opening S side, the light beam coming from the direction substantially orthogonal to the central axis 2 is reflected in the central axis 2 direction. It is preferable for synthesizing the side viewing optical path A and the direct viewing optical path B. Moreover, it becomes possible to arrange strong negative power on the object side, so-called telephoto power arrangement, and a wide angle of view can be obtained.

  Further, since the first reflecting surface 22 and the second reflecting surface 23 are arranged with the concave surface facing the opening S, the power arrangement on the reflecting surface becomes negative and becomes a telephoto type power arrangement, and the angle of view is widened. I can take it. Further, the occurrence of coma aberration in the side viewing optical path A is preferably reduced.

  Further, since the image in the side viewing optical path A does not form an intermediate image in the optical path, the entire length of the optical system can be shortened, which greatly contributes to the miniaturization of the optical system.

More preferably, when the outer shape of the optical element is D, D <10 mm (1)
It is preferable to satisfy the following conditions.

  In particular, when used as an imaging system for an endoscope, satisfying the above conditional expression is preferable in terms of reducing the burden on the subject.

More preferably, when the outer shape of the image of the reflected light path is Dr,
D / Dr <2 (2)
It is preferable to satisfy the following conditions.

  When the upper limit is exceeded, the imaging area becomes too small with respect to the entire outer shape of the optical system 1, and it becomes impossible to shoot a good image due to noise of the imaging element or the like.

  Examples 1 to 5 of the optical system according to the present invention will be described below. The configuration parameters of these optical systems will be described later.

  In the forward ray tracking, for example, as shown in FIG. 1, the coordinate system uses, as the origin O of the decentered optical surface, a point where the extension of the central principal ray from the side-viewing object surface 3 toward the first surface intersects the central axis 2; A direction perpendicular to the central axis 2 opposite to the central axis 2 with respect to the side-viewing object plane 3 is defined as a Y-axis positive direction, and a plane in FIG. 1 is defined as a YZ plane. The direction on the image plane 5 side in FIG. 1 is the Z axis positive direction, and the Y axis, the Z axis, and the axis constituting the right-handed orthogonal coordinate system are the X axis positive direction. Reference numeral 4 denotes a direct-view object surface.

  For the decentered surface, the decentering amount from the origin O of the optical system 1 of the coordinate system in which the surface is defined (X-axis direction, Y-axis direction, and Z-axis direction are X, Y, and Z, respectively), and the optical system 1 The inclination angles (α, β, γ (°), respectively) of the coordinate system defining the respective planes centered on the X axis, the Y axis, and the Z axis of the coordinate system defined by the origin O are given. . In this case, positive α and β mean counterclockwise rotation with respect to the positive direction of each axis, and positive γ means clockwise rotation with respect to the positive direction of the Z axis. Note that the α, β, and γ rotations of the central axis of the surface are performed by rotating the coordinate system defining each surface counterclockwise around the X axis of the coordinate system defined at the origin of the optical system. Then rotate it around the Y axis of the new rotated coordinate system by β and then rotate it around the Z axis of another rotated new coordinate system by γ. It is.

  Further, among the optical action surfaces constituting the optical system of each embodiment, when a specific surface and a subsequent surface constitute a coaxial optical system, a surface interval is given, in addition, the curvature radius of the surface, The refractive index and Abbe number of the medium are given according to conventional methods.

  In addition, a term relating to an aspheric surface for which no data is described in the constituent parameters described later is zero. The refractive index and the Abbe number are shown for the d-line (wavelength 587.56 nm). The unit of length is mm. As described above, the eccentricity of each surface is expressed by the amount of eccentricity from the reference surface.

  The aspheric surface is a rotationally symmetric aspheric surface given by the following definition.

^{Z = (Y 2 / R)} / [1+ {1- (1 + k) Y 2 / R 2} 1/2]
+ AY ⁴ + bY ⁶ + cY ⁸ + dY ¹⁰ +...
... (a)
However, Z is taken as an axis, and Y is taken in a direction perpendicular to the axis. Here, R is a paraxial radius of curvature, k is a conic constant, a, b, c, d,... Are fourth-order, sixth-order, eighth-order, and tenth-order aspherical coefficients, respectively. The Z axis of this defining formula is the axis of a rotationally symmetric aspherical surface.

  The extended rotation free-form surface is a rotationally symmetric surface given by the following definition.

  First, as shown in FIG. 2, the following curve (b) passing through the origin on the YZ coordinate plane is determined.

^{Z = (Y 2 / RY)} / [1+ {1- (C 1 +1) Y 2 / RY 2} 1/2]
+ C ₂ Y + C ₃ Y ² + C ₄ Y ³ + C ₅ Y ⁴ + C ₆ Y ⁵ + C ₇ Y ⁶
+ ··· + C ₂₁ Y ²⁰ + ··· + C _{n + 1} Y ⁿ + ····
... (b)
Next, a curve F (Y) obtained by rotating the curve (b) in the positive direction of the X-axis and turning it counterclockwise to be positive is determined. This curve F (Y) also passes through the origin on the YZ coordinate plane.

  The curve F (Y) is translated in the Y positive direction by a distance R (Y negative direction if negative), and then the rotationally symmetric surface is rotated by rotating the translated curve around the Z axis. Let it be a free-form surface.

  As a result, the extended rotation free-form surface becomes a free-form surface (free-form curve) in the YZ plane and a circle with a radius | R | in the XY plane.

  From this definition, the Z-axis becomes the axis of the extended rotation free-form surface (rotation symmetry axis).

Where RY is the radius of curvature of the spherical term in the YZ section, C ₁ is the conic constant, C ₂ , C ₃ , C ₄ , C ₅ . Aspheric coefficient.

A conical surface having an axis parallel to the Y axis as a central axis is given as one of the extended rotation free-form surfaces, and RY = ∞, C ₁ , C ₂ , C ₃ , C ₄ , C ₅ ,. , Θ = (conical surface inclination angle), R = (radius of bottom surface in XZ plane).

  In addition, a term relating to an aspheric surface for which no data is described in the constituent parameters described later is zero. The refractive index and the Abbe number are shown for the d-line (wavelength 587.56 nm). The unit of length is mm. As described above, the eccentricity of each surface is expressed by the amount of eccentricity from the reference surface.

  A cross-sectional view taken along the central axis 2 of the optical system 1 of Example 1 is shown in FIG. Further, FIG. 4 shows a lateral aberration diagram of the side viewing optical path of the entire optical system of this embodiment, and FIG. 5 shows a lateral aberration diagram of the direct viewing optical path. In this lateral aberration diagram, the angle shown at the center indicates (horizontal field angle, vertical field angle), and the lateral aberrations in the Y direction (meridional direction) and X direction (sagittal direction) at that field angle. Show. Note that a negative field angle means a clockwise angle in the Y-axis positive direction for the horizontal field angle, and a clockwise angle in the X-axis positive direction for the vertical field angle. same as below.

  In this embodiment, the transmission surface and the reflection surface of a transparent medium having a refractive index larger than 1 that is concentric with the central axis 2 of the optical system 1 are all different surfaces without being commonly used in the side-view optical path. This is an example.

  The optical system 1 is arranged coaxially on the central axis 2 between the front group Gf and the rear group Gb, and the front group Gf rotationally symmetric about the central axis 2, the rear group Gb rotationally symmetric about the central axis 2. The front group Gf includes the first group G1 and the second group G2, and the rear group Gb includes the third group G3, the fourth group G4, and the fifth group G5.

  The first group G1 includes a plano-concave negative lens L1 having a concave surface directed toward the image plane 5 side. The plano-concave negative lens L1 has a direct-view first transmission surface 11 having an infinite curvature radius and a direct-view second transmission surface 12 disposed on the image plane 5 side of the direct-view first transmission surface 11.

  The second group G2 is made of a transparent medium L2 having a rotational symmetry around the central axis 2 and a refractive index larger than 1, and is an optical path combining optical system that combines the side-view optical path A and the direct-view optical path B. The transparent medium L2 is opposed to the side-viewing object surface 3 and is disposed on the outer side, and is formed inside the cylindrical side-view first transmission surface 21 parallel to the central axis 2 and the transparent medium L2. Formed on the side of the central axis 2 from the transmission surface 21 and made of a toric surface and having a negative power, the side-view first reflection surface 22 and the inside of the transparent medium L2, the image surface from the side-view first reflection surface 22 5 is disposed on the opposite side to 5, is composed of a toric surface, and has a second side reflecting surface 23 having a positive power, and is disposed closer to the image plane 5 than the second side reflecting surface 23 and is composed of a spherical surface and has a negative power It has the 2nd permeation | transmission surface 24 with side view. Further, a direct-view third transmission surface 25 made of a spherical surface and having negative power, and a direct-view fourth transmission surface 26 made of a spherical surface and having a negative power disposed on the image plane 5 side from the direct-view third transmission surface 25. Have. The side view second transmission surface 24 and the direct view fourth transmission surface 26 are the same surface.

  The third group G3 includes a positive meniscus lens L3 having a convex surface directed toward the image surface 5 side, and a common first transmission surface 31 and a common second transmission surface disposed closer to the image surface 5 than the common first transmission surface 31. 32.

  The fourth group G4 is composed of a cemented lens of a negative meniscus lens L4 and a biconvex positive lens L5 having a concave surface directed toward the image surface side, and a common third transmission surface 41 and a common third transmission surface 41 closer to the image surface 5 side. The joint surface 45 is disposed, and the common fourth transmission surface 51 is disposed closer to the image surface 5 than the joint surface 45.

  The fifth group G5 includes a cemented lens of a biconvex positive lens L6 and a biconcave negative lens L7, a common fifth transmission surface 61, and a cemented surface 67 disposed on the image plane 5 side from the common fifth transmission surface 61. The common sixth transmission surface 71 is disposed closer to the image plane 5 than the bonding surface 67.

  The optical system 1 forms a side viewing optical path A and a direct viewing optical path B. In the side viewing optical path A, the light beam incident from the side viewing object surface 3 on the side of the optical system 1 passes through the second group G2 and the rear group Gb in the front group Gf in order, and passes through the image plane 5 perpendicular to the central axis 2. An image is formed in an annular shape outside the center axis 2. In the direct-view optical path B, the light beam incident from the direct-view object surface 4 in the vicinity of the central axis 2 of the optical system 1 passes through the front group Gf and the rear group Gb in this order, and the central axis 2 of the image plane 5 perpendicular to the central axis 2. An image is formed in a circle in the vicinity.

  The light beam incident from the side of the optical system 1 as the side-viewing optical path A enters the transparent medium L2 of the second group G2 of the front group Gf via the side-view first transmission surface 21, and is side-viewed on the central axis 2 side. A substantially Z-shape that is reflected by the first reflecting surface 22 to the opposite side of the image surface 5, reflected by the second-viewing second reflecting surface 23 to the image-surface 5 side, and exits from the transparent medium L 2 through the second-viewing second transmitting surface 24. Shaped optical path.

  Thereafter, the central axis 2 is sandwiched between the front group Gf and the rear group Gb through the aperture 5 that is coaxially disposed on the central axis 2 and forms a stop, and is inserted into the positive meniscus lens L3 of the third group G3 of the rear group Gb. On the opposite side, it enters through the common first transmission surface 31, exits from the common second transmission surface 32, and is a common third transmission surface in the cemented lens of the negative meniscus lens L4 and the biconvex positive lens L5 of the fourth group G4. 41, through the cemented surface 45 and out of the common fourth transmissive surface 42, into the cemented lens of the biconvex positive lens L6 and the biconcave negative lens L7 of the fifth group G5. Through the joint surface 67, exits from the common sixth transmission surface 71, and forms an image at a predetermined radial position away from the central axis 2 of the image plane 5.

  Further, the light beam incident on the optical system 1 as the direct-view optical path B enters the transparent medium L1 of the first group G1 of the front group Gf through the direct-view first transmission surface 11 and is closer to the image plane 5 side than the direct-view first transmission surface 11. Through the direct-view second transmission surface 12, which exits from the transparent medium L 1, enters the transparent medium L 2 of the second group G 2 through the direct-view third transmission surface 25, and enters the image plane from the direct-view first transmission surface 11. It goes out of the transparent medium L2 through the direct-view fourth transmission surface 26 arranged on the side 5.

  Thereafter, a common first transmission surface 31 is provided in the positive meniscus lens L3 of the third group G3 of the rear group Gb through an opening 5 that is disposed coaxially with the central axis 2 between the front group Gf and the rear group Gb and forms a stop. Through the common second transmission surface 32, enters the cemented lens of the negative meniscus lens L4 and the biconvex positive lens L5 of the fourth group G4 through the common third transmission surface 41, and enters the cemented surface 45. Then, the light exits from the common fourth transmission surface 42, enters the cemented lens of the biconvex positive lens L6 and the biconcave negative lens L7 of the fifth group G5 via the common fifth transmission surface 61, and passes through the cemented surface 67. Then, the light exits from the common sixth transmission surface 71 and forms an image on the central axis 2 of the image surface 5.

The specification of this Example 1 is
Angle of view (side view) 60 ° to 120 °
Angle of view (direct view) 0 ° -60 °
Entrance pupil diameter (side view) φ0.10mm
(Direct view) φ0.42mm
Image size (side view) φ3.80 to φ4.96
(Direct view) φ2.88
A sectional view taken along the central axis 2 of the optical system 1 of Example 2 is shown in FIG. Also, FIG. 7 shows a lateral aberration diagram of the side viewing optical path of the entire optical system of this example, and FIG. 8 shows a lateral aberration diagram of the direct viewing optical path. In this lateral aberration diagram, the angle shown at the center indicates (horizontal field angle, vertical field angle), and the lateral aberrations in the Y direction (meridional direction) and X direction (sagittal direction) at that field angle. Show. Note that a negative field angle means a clockwise angle in the Y-axis positive direction for the horizontal field angle, and a clockwise angle in the X-axis positive direction for the vertical field angle. same as below.

  In this embodiment, the side-view first reflection surface 22 and the side-view first reflection surface 22 of the side-view optical path A among the transmission surface and the reflection surface of the transparent medium having a refractive index larger than 1 concentric with the central axis 2 of the optical system 1 are side-viewed. This is an example in which the second transmission surface 24, the side-view second reflection surface 23 of the side-view optical path A, and the direct-view third transmission surface 25 of the direct-view optical path B are configured in the same position and shape.

  The optical system 1 is arranged coaxially on the central axis 2 between the front group Gf and the rear group Gb, and the front group Gf rotationally symmetric about the central axis 2, the rear group Gb rotationally symmetric about the central axis 2. The front group Gf includes the first group G1 and the second group G2, and the rear group Gb includes the third group G3 and the fourth group G4.

  The first group G1 includes a plano-concave negative lens L1 having a concave surface directed toward the image plane 5 side. The plano-concave negative lens L1 has a direct-view first transmission surface 11 having an infinite curvature radius and a direct-view second transmission surface 12 disposed on the image plane 5 side of the direct-view first transmission surface 11.

  The second group G2 is made of a transparent medium L2 having a rotational symmetry around the central axis 2 and a refractive index larger than 1, and is an optical path combining optical system that combines the side-view optical path A and the direct-view optical path B. The transparent medium L2 is opposed to the side-viewing object surface 3 and is disposed on the outer side, and is formed inside the cylindrical side-view first transmission surface 21 parallel to the central axis 2 and the transparent medium L2. Formed on the side of the central axis 2 from the transmission surface 21 and made of an aspherical surface, has a negative first power reflecting surface 22 having a negative power, and is formed inside the transparent medium L2, and is imaged from the first reflecting surface 22 in the side view. 5 is disposed on the opposite side to 5 and has a spherical surface, and has a positive side power second reflection surface 23, and is disposed on the image plane 5 side of the side view second reflection surface 23, and is aspheric and has a negative power. It has the 2nd permeation | transmission surface 24 with side view. Further, a direct-view third transmission surface 25 made of a spherical surface and having negative power, and a direct-view fourth transmission surface 26 made of a spherical surface and having a negative power disposed on the image plane 5 side from the direct-view third transmission surface 25. Have. The side-view first reflection surface 22 and the side-view second transmission surface 24 are the same surface, and the side-view second reflection surface 23 and the direct-view third transmission surface 25 are the same surface.

  The third group G3 includes a positive meniscus lens L3 having a convex surface directed toward the image surface 5 side, and a common first transmission surface 31 and a common second transmission surface disposed closer to the image surface 5 than the common first transmission surface 31. 32.

  The fourth group G4 is composed of a cemented lens of a negative meniscus lens L4 and a biconvex positive lens L5 having a concave surface directed toward the image surface side, and a common third transmission surface 41 and a common third transmission surface 41 closer to the image surface 5 side. The joint surface 45 is disposed, and the common fourth transmission surface 51 is disposed closer to the image surface 5 than the joint surface 45.

  The optical system 1 forms a side viewing optical path A and a direct viewing optical path B. In the side viewing optical path A, the light beam incident from the side viewing object surface 3 on the side of the optical system 1 passes through the second group G2 and the rear group Gb in the front group Gf in order, and passes through the image plane 5 perpendicular to the central axis 2. An image is formed in an annular shape outside the center axis 2. In the direct-view optical path B, the light beam incident from the direct-view object surface 4 in the vicinity of the central axis 2 of the optical system 1 passes through the front group Gf and the rear group Gb in this order, and the central axis 2 of the image plane 5 perpendicular to the central axis 2. An image is formed in a circle in the vicinity.

  The light beam incident from the side of the optical system 1 as the side-viewing optical path A enters the transparent medium L2 of the second group G2 of the front group Gf via the side-view first transmission surface 21, and is side-viewed on the central axis 2 side. A substantially Z-shape that is reflected by the first reflecting surface 22 to the opposite side of the image surface 5, reflected by the second-viewing second reflecting surface 23 to the image-surface 5 side, and exits from the transparent medium L 2 through the second-viewing second transmitting surface 24. Shaped optical path.

  Thereafter, the central axis 2 is sandwiched between the front group Gf and the rear group Gb through the aperture 5 that is coaxially disposed on the central axis 2 and forms a stop, and is inserted into the positive meniscus lens L3 of the third group G3 of the rear group Gb. Enters through the common first transmission surface 31 on the opposite side, exits from the common second transmission surface 32, enters the negative meniscus lens L4 of the fourth group G4 through the common third transmission surface 41, and enters the bonding surface 45. Then, the light exits from the common fourth transmission surface 51 of the biconvex positive lens L5 and forms an image at a predetermined position in the radial direction away from the central axis 2 of the image surface 5.

  Further, the light beam incident on the optical system 1 as the direct-view optical path B enters the transparent medium L1 of the first group G1 of the front group Gf through the direct-view first transmission surface 11 and is closer to the image plane 5 side than the direct-view first transmission surface 11. Through the direct-view second transmission surface 12, which exits from the transparent medium L 1, enters the transparent medium L 2 of the second group G 2 through the direct-view third transmission surface 25, and enters the image plane from the direct-view first transmission surface 11. It goes out of the transparent medium L2 through the direct-view fourth transmission surface 26 arranged on the side 5.

  Thereafter, a common first transmission surface 31 is provided in the positive meniscus lens L3 of the third group G3 of the rear group Gb through an opening 5 that is disposed coaxially with the central axis 2 between the front group Gf and the rear group Gb and forms a stop. Through the common second transmission surface 32, enters the negative meniscus lens L4 of the fourth group G4 through the common third transmission surface 41, passes through the cementing surface 45, and is common to the biconvex positive lens L5. The light exits from the fourth transmission surface 51 and forms an image on the central axis 2 of the image surface 5.

The specification of Example 2 is
Angle of view (side view) 60 ° to 120 °
Angle of view (direct view) 0 ° -60 °
Entrance pupil diameter (side view) φ0.13mm
(Direct view) φ0.68mm
Image size (side view) φ3.87 to φ4.90
(Direct view) φ2.83
A sectional view taken along the central axis 2 of the optical system 1 of Example 3 is shown in FIG. Further, FIG. 10 shows a lateral aberration diagram of the side viewing optical path of the entire optical system of this example, and FIG. 11 shows a lateral aberration diagram of the direct viewing optical path. In this lateral aberration diagram, the angle shown at the center indicates (horizontal field angle, vertical field angle), and the lateral aberrations in the Y direction (meridional direction) and X direction (sagittal direction) at that field angle. Show. Note that a negative field angle means a clockwise angle in the Y-axis positive direction for the horizontal field angle, and a clockwise angle in the X-axis positive direction for the vertical field angle. same as below.

  In this embodiment, the side-view first reflection surface 22 and the side-view first reflection surface 22 of the side-view optical path A among the transmission surface and the reflection surface of the transparent medium having a refractive index larger than 1 concentric with the central axis 2 of the optical system 1 are side-viewed. The second transmission surface 24 and the direct-view fourth transmission surface 26 of the direct-view optical path B, and the side-view second reflection surface 23 of the side-view optical path A and the direct-view third transmission surface 25 of the direct-view optical path B are configured in the same position and shape. It is an example.

  The optical system 1 is arranged coaxially on the central axis 2 between the front group Gf and the rear group Gb, and the front group Gf rotationally symmetric about the central axis 2, the rear group Gb rotationally symmetric about the central axis 2. The front group Gf includes the first group G1 and the second group G2, and the rear group Gb includes the third group G3 and the fourth group G4.

  The first group G1 includes a negative meniscus lens L1 having a concave surface facing the image surface side. The negative meniscus lens L1 has a direct-view first transmission surface 11 and a direct-view second transmission surface 12 arranged on the image plane 5 side with respect to the direct-view first transmission surface 11.

  The second group G2 includes a transparent medium L2 having a refractive index greater than 1 and a biconcave negative lens L3 around the central axis 2, and a light path composition for combining the side view light path A and the direct view light path B. It is an optical system.

  The transparent medium L2 is opposed to the side-viewing object surface 3 and is disposed on the outer side, and is formed inside the cylindrical side-view first transmission surface 21 parallel to the central axis 2 and the transparent medium L2. Formed on the side of the central axis 2 from the transmission surface 21 and made of an aspherical surface, has a negative first power reflecting surface 22 having a negative power, and is formed inside the transparent medium L2, and is imaged from the first reflecting surface 22 in the side view. 5 is disposed on the opposite side to 5 and has a spherical surface, and has a positive side power second reflection surface 23, and is disposed on the image plane 5 side of the side view second reflection surface 23, and is aspheric and has a negative power. It has the 2nd permeation | transmission surface 24 with side view. Further, a direct-view third transmission surface 25 made of a spherical surface and having negative power, and a direct-view fourth transmission surface 26 made of a spherical surface and having a negative power disposed on the image plane 5 side from the direct-view third transmission surface 25. Have. The side-view first reflection surface 22 and the side-view second transmission surface 24 are the same surface.

  The biconcave negative lens L3 is a spherical surface, and is negative with a side-view third transmission surface 31 having negative power, a side-view fourth transmission surface 32 having negative power, and a direct-view fifth transmission surface 33 having negative power. And a direct-view sixth transmission surface 34 having the following power. The side-view third transmission surface 31 and the direct-view fifth transmission surface 33 are the same surface, and the side-view fourth transmission surface 32 and the direct-view sixth transmission surface 34 are the same surface.

  The third group G3 includes a cemented lens of a negative meniscus lens L4 having a convex surface facing the image surface 5 and a positive meniscus lens L5 having a convex surface facing the image surface 5, and has a common first transmission surface 41 and a common first lens. It has a joint surface 45 disposed on the image surface 5 side from the transmission surface 41 and a common second transmission surface 51 disposed on the image surface 5 side from the joint surface 45.

  The fourth group G4 includes a cemented lens of a negative meniscus lens L6 and a biconvex positive lens L7 having a concave surface directed toward the image plane side. The fourth third group G4 is closer to the image plane 5 side than the common third transmission plane 61 and the common third transmission plane 61. It has a joint surface 67 to be disposed and a common fourth transmission surface 71 disposed on the image surface 5 side from the joint surface 67.

  The optical system 1 forms a side viewing optical path A and a direct viewing optical path B. In the side viewing optical path A, the light beam incident from the side viewing object surface 3 on the side of the optical system 1 passes through the second group G2 and the rear group Gb in the front group Gf in order, and passes through the image plane 5 perpendicular to the central axis 2. An image is formed in an annular shape outside the center axis 2. In the direct-view optical path B, the light beam incident from the direct-view object surface 4 in the vicinity of the central axis 2 of the optical system 1 passes through the front group Gf and the rear group Gb in this order, and the central axis 2 of the image plane 5 perpendicular to the central axis 2. An image is formed in a circle in the vicinity.

The light beam incident from the side of the optical system 1 as the side-viewing optical path A enters the transparent medium L2 of the second group G2 of the front group Gf via the side-view first transmission surface 21, and is side-viewed on the central axis 2 side. A substantially Z-shape that is reflected by the first reflecting surface 22 to the opposite side of the image surface 5, reflected by the second-viewing second reflecting surface 23 to the image-surface 5 side, and exits from the transparent medium L 2 through the second-viewing second transmitting surface 24. Shaped optical path. Then, it enters the transparent medium L3 from the third transmission surface 31 as viewed from the side, and exits from the transparent medium L3 via the fourth transmission surface 32 as viewed from the side. Thereafter, it is coaxial with the central axis 2 between the front group Gf and the rear group Gb. And a common first transmission surface 41 on the opposite side across the central axis 2 in the cemented lens of the negative meniscus lens L4 and the positive meniscus lens L5 of the third group G3 of the rear group Gb. Through the cemented surface 45 and out of the common second transmissive surface 51, and through the common third transmissive surface 61 in the cemented lens of the negative meniscus lens L6 and the biconvex positive lens L7 of the fourth group G4. Enters, passes through the joint surface 67, exits from the common fourth transmission surface 71, and forms an image at a predetermined radial position away from the central axis 2 of the image surface 5.

  Further, the light beam incident on the optical system 1 as the direct-view optical path B enters the transparent medium L1 of the first group G1 of the front group Gf through the direct-view first transmission surface 11 and is closer to the image plane 5 side than the direct-view first transmission surface 11. Through the direct-view second transmission surface 12, which exits from the transparent medium L 1, enters the transparent medium L 2 of the second group G 2 through the direct-view third transmission surface 25, and enters the image plane from the direct-view first transmission surface 11. Goes out of the transparent medium L2 through the direct-view fourth transmission surface 26 disposed on the side 5, enters the transparent medium L 3 through the direct-view fifth transmission surface 33, and is closer to the image plane 5 side than the direct-view fifth transmission surface 33. It goes out of the transparent medium L3 through the arranged direct view sixth transmission surface 34.

  After that, a cemented lens of the negative meniscus lens L4 and the positive meniscus lens L5 of the third group G3 of the rear group Gb passes through an aperture 5 that is arranged coaxially with the central axis 2 between the front group Gf and the rear group Gb and forms a stop. Enters through the common first transmission surface 41, passes through the cementing surface 45, exits from the common second transmission surface 51, and enters the cemented lens of the negative meniscus lens L6 and the biconvex positive lens L7 of the fourth group G4. The light enters through the common third transmission surface 61, passes through the joint surface 67, exits from the common fourth transmission surface 71, and forms an image on the central axis 2 of the image surface 5.

The specification of this Example 3 is
Angle of view (side view) 60 ° to 120 °
Angle of view (direct view) 0 ° -60 °
Entrance pupil diameter (side view) φ0.09mm
(Direct view) φ0.49mm
Image size (side view) φ3.78 to φ4.94
(Direct view) φ2.96
A sectional view taken along the central axis 2 of the optical system 1 of Example 4 is shown in FIG. Further, FIG. 13 shows a lateral aberration diagram of the side viewing optical path of the entire optical system of this example, and FIG. 14 shows a lateral aberration diagram of the direct viewing optical path. In this lateral aberration diagram, the angle shown at the center indicates (horizontal field angle, vertical field angle), and the lateral aberrations in the Y direction (meridional direction) and X direction (sagittal direction) at that field angle. Show. Note that a negative field angle means a clockwise angle in the Y-axis positive direction for the horizontal field angle, and a clockwise angle in the X-axis positive direction for the vertical field angle. same as below.

  In this embodiment, the side-view first reflection surface 22 and the side-view first reflection surface 22 of the side-view optical path A among the transmission surface and the reflection surface of the transparent medium having a refractive index larger than 1 concentric with the central axis 2 of the optical system 1 are side-viewed. The second transmission surface 24 and the direct-view fourth transmission surface 26 of the direct-view optical path B, and the side-view second reflection surface 23 of the side-view optical path A and the direct-view third transmission surface 25 of the direct-view optical path B are configured in the same position and shape. It is an example.

  The optical system 1 is arranged coaxially on the central axis 2 between the front group Gf and the rear group Gb, and the front group Gf rotationally symmetric about the central axis 2, the rear group Gb rotationally symmetric about the central axis 2. The front group Gf includes the first group G1 and the second group G2, and the rear group Gb includes the third group G3 and the fourth group G4.

  The first group G1 includes a negative meniscus lens L1 having a concave surface on the image surface side and a negative meniscus lens L2 having a convex surface on the image surface 5 side. The negative meniscus lens L1 has a direct-view first transmission surface 11 and a direct-view second transmission surface 12 arranged on the image plane 5 side with respect to the direct-view first transmission surface 11. The negative meniscus lens L <b> 2 has a direct-view third transmission surface 21 and a direct-view fourth transmission surface 22 disposed on the image plane 5 side with respect to the direct-view third transmission surface 21.

  The second group G2 includes a transparent medium L3 having a rotationally symmetric refractive index greater than 1 around the central axis 2 and a biconcave negative lens L4, and combines the optical path A for side viewing and the optical path B for direct viewing. It is an optical system.

  The transparent medium L3 is opposed to the side-viewing object surface 3 and is disposed outside and is formed inside the cylindrical side-view first transmission surface 31 parallel to the central axis 2 and the transparent medium L3. Formed on the side of the central axis 2 from the transmission surface 31 and made of an aspherical surface, has a negative first power reflecting surface 32 having a negative power, and is formed inside the transparent medium L3. 5 is arranged on the opposite side to 5 and is formed of a spherical surface and has a positive side power second reflection surface 33, and is disposed on the image surface 5 side of the side view second reflection surface 33 and is formed of an aspheric surface and has a negative power. The side transmission second transmission surface 34 having Further, a direct-view fifth transmission surface 35 made of a spherical surface and having a negative power, and a direct-view sixth transmission surface 36 made of a spherical surface and having a negative power are arranged on the image plane 5 side of the direct-view fifth transmission surface 35. Have. The side-view first reflection surface 32, the side-view second transmission surface 34, and the direct-view sixth transmission surface 36 are the same surface, and the side-view second reflection surface 33 and the direct-view fifth transmission surface 35 are the same surface.

  The biconcave negative lens L4 is formed of a spherical surface, is negative with a side-view third transmission surface 41 with negative power, a side-view fourth transmission surface 42 with negative power, and a direct-view fifth transmission surface 43 with negative power. And a direct-view sixth transmission surface 44 having the following power. The side-view third transmission surface 41 and the direct-view fifth transmission surface 43 are the same surface, and the side-view fourth transmission surface 42 and the direct-view sixth transmission surface 44 are the same surface.

  The third group G3 includes a cemented lens of a biconcave negative lens L5 and a biconvex positive lens L6, a common first transmission surface 51, and a cemented surface 56 disposed on the image plane 5 side from the common first transmission surface 51. The common second transmission surface 61 is disposed on the image plane 5 side with respect to the bonding surface 56.

  The fourth group G4 includes a cemented lens of a negative meniscus lens L7 and a biconvex positive lens L8 having a concave surface directed toward the image surface side. The fourth group G4 has a common third transmission surface 71 and a common third transmission surface 71 closer to the image surface 5 side. It has a joint surface 78 to be disposed and a common fourth transmission surface 81 disposed on the image surface 5 side with respect to the joint surface 78.

  The optical system 1 forms a side viewing optical path A and a direct viewing optical path B. In the side viewing optical path A, the light beam incident from the side viewing object surface 3 on the side of the optical system 1 passes through the second group G2 and the rear group Gb in the front group Gf in order, and passes through the image plane 5 perpendicular to the central axis 2. An image is formed in an annular shape outside the center axis 2. In the direct-view optical path B, the light beam incident from the direct-view object surface 4 in the vicinity of the central axis 2 of the optical system 1 passes through the front group Gf and the rear group Gb in this order, and the central axis 2 of the image plane 5 perpendicular to the central axis 2. An image is formed in a circle in the vicinity.

A light beam incident from the side of the optical system 1 as the side-view optical path A enters the transparent medium L3 of the second group G2 of the front group Gf via the side-view first transmission surface 31, and is side-viewed on the central axis 2 side. A substantially Z-shape that is reflected from the first reflecting surface 32 to the opposite side of the image surface 5, reflected from the second viewing surface 33 by the side view to the image surface 5 side, and exits from the transparent medium L <b> 2 through the second viewing surface 34. Shaped optical path. Then, the light enters the transparent medium L4 from the third transmission surface 41 in the side view, and exits from the transparent medium L3 through the fourth transmission surface 42 in the side view. Thereafter, it is coaxial with the central axis 2 between the front group Gf and the rear group Gb. And a common first transmission on the opposite side with the central axis 2 in the cemented lens of the biconvex negative lens L5 and the biconvex positive lens L6 of the third group G3 of the rear group Gb. It enters through the surface 51, passes through the cemented surface 56, exits from the common second transmissive surface 61, and is a common third transmissive surface 71 in the cemented lens of the negative meniscus lens L7 and the biconvex positive lens L8 of the fourth group G4. Through the joint surface 78, exits from the common fourth transmission surface 81, and forms an image at a predetermined radial position away from the central axis 2 of the image surface 5.

  Further, the light beam incident on the optical system 1 as the direct-view optical path B enters the transparent medium L1 of the first group G1 of the front group Gf through the direct-view first transmission surface 11 and is closer to the image plane 5 side than the direct-view first transmission surface 11. Through the direct-view second transmission surface 12, which exits from the transparent medium L 1, enters the transparent medium L 2 of the second group G 2 through the direct-view third transmission surface 25, and enters the image plane from the direct-view first transmission surface 11. Goes out of the transparent medium L2 through the direct-view fourth transmission surface 26 disposed on the side 5, enters the transparent medium L 3 through the direct-view fifth transmission surface 33, and is closer to the image plane 5 side than the direct-view fifth transmission surface 33. It goes out of the transparent medium L3 through the arranged direct-view sixth transmission surface 34, enters the transparent medium L4 through the direct-view seventh transmission surface 43, and is arranged on the image plane 5 side from the direct-view seventh transmission surface 43. It goes out of the transparent medium L4 through the direct-view eighth transmission surface 44.

  After that, through the opening 5 which is coaxially arranged on the central axis 2 between the front group Gf and the rear group Gb and forms a diaphragm, the biconcave negative lens L5 and the biconvex positive lens L6 of the third group G3 of the rear group Gb The cemented lens enters the cemented lens through the common first transmitting surface 51, exits from the common second transmitting surface 61 through the cemented surface 56, and is a cemented lens of the negative meniscus lens L7 and the biconvex positive lens L8 of the fourth group G4. It enters through the common third transmission surface 71, passes through the joint surface 78, exits from the common fourth transmission surface 81, and forms an image on the central axis 2 of the image plane 5.

The specification of this Example 4 is
Angle of view (side view) 60 ° to 120 °
Angle of view (direct view) 0 ° -60 °
Entrance pupil diameter (side view) φ0.11mm
(Direct view) φ0.46mm
Image size (side view) φ3.77 to φ4.94
(Direct view) φ2.97
A sectional view taken along the central axis 2 of the optical system 1 of Example 5 is shown in FIG. Further, FIG. 16 shows a lateral aberration diagram of the side viewing optical path of the entire optical system of this example, and FIG. 17 shows a lateral aberration diagram of the direct viewing optical path. In this lateral aberration diagram, the angle shown at the center indicates (horizontal field angle, vertical field angle), and the lateral aberrations in the Y direction (meridional direction) and X direction (sagittal direction) at that field angle. Show. Note that a negative field angle means a clockwise angle in the Y-axis positive direction for the horizontal field angle, and a clockwise angle in the X-axis positive direction for the vertical field angle. same as below.

  In this embodiment, the side-view first reflection surface 22 and the side-view first reflection surface 22 of the side-view optical path A among the transmission surface and the reflection surface of the transparent medium having a refractive index larger than 1 concentric with the central axis 2 of the optical system 1 are side-viewed. The second transmission surface 24 and the direct-view fourth transmission surface 26 of the direct-view optical path B, and the side-view second reflection surface 23 of the side-view optical path A and the direct-view third transmission surface 25 of the direct-view optical path B are configured in the same position and shape. It is the example comprised as an attachment optical system attached to the front-end | tip of the existing optical system. In the figure, an arrow indicates an ideal lens.

  The optical system 1 includes a front group Gf that is rotationally symmetric about a central axis 2, a rear group Gb that includes an ideal lens, and an aperture 5 that is coaxially disposed on the central axis 2 between the front group Gf and the rear group Gb. The front group Gf includes a first group G1 and a second group G2, and the rear group Gb includes an ideal lens L0.

  The first group G1 includes a negative meniscus lens L1 having a convex surface directed toward the object plane side. The first group G1 is disposed on the image plane 5 side of the direct-view first transmission surface 11 and the direct-view first transmission surface 11, and has direct power having negative power. A second transmission surface 12 is provided.

  The second group G2 includes a transparent medium L2 having a rotational symmetry about the central axis 2 and a refractive index larger than 1, and a negative meniscus lens L3 having a convex surface directed toward the image plane 5 side. This is an optical path synthesis optical system that synthesizes the optical path B.

  The transparent medium L2 is opposed to the side-viewing object surface 3 and is disposed on the outer side, and is formed inside the cylindrical side-view first transmission surface 21 parallel to the central axis 2 and the transparent medium L2. Formed on the side of the central axis 2 from the transmission surface 21 and made of an aspherical surface, has a negative first power reflecting surface 22 having a negative power, and is formed inside the transparent medium L2, and is imaged from the first reflecting surface 22 in the side view. 5 is arranged on the opposite side to 5 and is made of an aspherical surface, and has a second-side reflecting surface 23 having a positive power, and is arranged closer to the image plane 5 than the second-side reflecting surface 23 is made of an aspherical surface. A side-transmitting second transmission surface 24 having power is provided. Further, a direct-view third transmission surface 25 made of an aspheric surface and having negative power, and a direct-view fourth transmission surface arranged on the image plane 5 side of the direct-view third transmission surface 25 and made of an aspheric surface and having negative power. 26. The side-view first reflection surface 22, the side-view second transmission surface 24, and the direct-view fourth transmission surface 26 are the same surface, and the side-view second reflection surface 23 and the direct-view third transmission surface 25 are the same surface.

  The negative meniscus lens L3 includes a side-view third transmission surface 31, a side-view fourth transmission surface 32, a direct-view fifth transmission surface 33, and a direct-view sixth transmission surface 34. The side-view third transmission surface 31 and the direct-view fifth transmission surface 33 are the same surface, and the side-view fourth transmission surface 32 and the direct-view sixth transmission surface 34 are the same surface.

  The rear group Gb is an ideal lens L0.

  The optical system 1 forms a side viewing optical path A and a direct viewing optical path B. In the side viewing optical path A, the light beam incident from the side viewing object surface 3 on the side of the optical system 1 passes through the second group G2 and the rear group Gb in the front group Gf in order, and passes through the image plane 5 perpendicular to the central axis 2. An image is formed in an annular shape outside the center axis 2. In the direct-view optical path B, the light beam incident from the direct-view object surface 4 in the vicinity of the central axis 2 of the optical system 1 passes through the front group Gf and the rear group Gb in this order, and the central axis 2 of the image plane 5 perpendicular to the central axis 2. An image is formed in a circle in the vicinity.

The light beam incident from the side of the optical system 1 as the side-viewing optical path A enters the transparent medium L2 of the second group G2 of the front group Gf via the side-view first transmission surface 21, and is side-viewed on the central axis 2 side. A substantially Z-shape that is reflected by the first reflecting surface 22 to the opposite side of the image surface 5, reflected by the second-viewing second reflecting surface 23 to the image-surface 5 side, and exits from the transparent medium L 2 through the second-viewing second transmitting surface 24. Shaped optical path. Then, it enters the transparent medium L3 from the third transmission surface 31 as viewed from the side, and exits from the transparent medium L3 via the fourth transmission surface 32 as viewed from the side. Thereafter, it is coaxial with the central axis 2 between the front group Gf and the rear group Gb. The image is formed at a predetermined position in the radial direction away from the central axis 2 of the image plane 5 through the ideal lens L0 of the rear group Gb through the aperture 5 that is disposed in the aperture and forms the stop.

  Further, the light beam incident on the optical system 1 as the direct-view optical path B enters the transparent medium L1 of the first group G1 of the front group Gf through the direct-view first transmission surface 11 and is closer to the image plane 5 side than the direct-view first transmission surface 11. Through the direct-view second transmission surface 12, which exits from the transparent medium L 1, enters the transparent medium L 2 of the second group G 2 through the direct-view third transmission surface 25, and enters the image plane from the direct-view first transmission surface 11. Goes out of the transparent medium L2 through the direct-view fourth transmission surface 26 disposed on the side 5, enters the transparent medium L 3 through the direct-view fifth transmission surface 33, and is closer to the image plane 5 side than the direct-view fifth transmission surface 33. It goes out of the transparent medium L3 through the arranged direct view sixth transmission surface 34.

  Thereafter, an image is formed on the central axis 2 of the image plane 5 through an aperture 5 which is disposed coaxially with the central axis 2 between the front group Gf and the rear group Gb and forms a stop, and through the ideal lens L0 of the rear group Gb. To do.

The specification of this Example 5 is
Angle of view (side view) 60 ° to 120 °
Angle of view (direct view) 0 ° -60 °
Entrance pupil diameter (side view) φ0.08mm
(Direct view) φ0.37mm
Image size (side view) φ3.74 to φ4.99
(Direct view) φ2.86
The configuration parameters of Examples 1 to 5 are shown below. In the table below, “ASS” indicates an aspherical surface, “ERFS” indicates an extended rotation free-form surface, and “RE” indicates a reflecting surface.

Example 1
Side-viewing optical path number of curvature radius Surface spacing Eccentricity Refractive index Abbe number Object surface ∞ ∞ Eccentricity (1)
1 ERFS [1] Eccentricity (2) 1.8348 42.7
2 ERFS [2] (RE) Eccentricity (3) 1.8348 42.7
3 ERFS [3] (RE) Eccentricity (4) 1.8348 42.7
4 ERFS [4] Eccentricity (5)
5 ∞ (diaphragm) 0.20 Eccentricity (6)
6 -0.89 0.80 1.7440 44.8
7 -1.26 0.10
8 6.06 0.50 1.7502 33.2
9 3.02 1.60 1.5174 67.3
10 -3.73 0.10
11 3.78 2.20 1.4875 70.4
12 -2.99 0.50 1.7508 32.4
13 56.93 5.13
14 ∞ 0.40 1.5163 64.1
15 ∞ 0.10
Image plane ∞
ERFS [1]
RY ∞
θ 90.00
R -3.00
ERFS [2]
RY 2.56
θ 31.22
R -2.33
ERFS [3]
RY 4.88
θ 2.88
R -1.71
ERFS [4]
RY 1.75
θ 40.71
R -1.14
Eccentricity (1)
X 0.00 Y 0.00 Z 0.00
α 90.00 β 0.00 γ 0.00
Eccentric [2]
X 0.00 Y 0.00 Z -0.03
α 0.00 β 0.00 γ 0.00
Eccentric [3]
X 0.00 Y 0.00 Z -0.04
α 0.00 β 0.00 γ 0.00
Eccentric [4]
X 0.00 Y 0.00 Z -1.22
α 0.00 β 0.00 γ 0.00
Eccentric [5]
X 0.00 Y 0.00 Z -0.38
α 0.00 β 0.00 γ 0.00
Eccentric [6]
X 0.00 Y 0.00 Z 1.77
α 0.00 β 0.00 γ 0.00
Direct-view optical path number Curvature radius Surface spacing Eccentricity Refractive index Abbe number Object surface ∞ ∞
1 ∞ 0.60 1.5163 64.1
2 1.50 1.76
3 ERFS [5] Eccentricity (7) 1.8348 42.7
4 ERFS [4] Eccentricity (5)
5 ∞ (diaphragm) 0.20 Eccentricity (6)
6 -0.89 0.80 1.7440 44.8
7 -1.26 0.10
8 6.06 0.50 1.7502 33.2
9 3.02 1.60 1.5174 67.3
10 -3.73 0.10
11 3.78 2.20 1.4875 70.4
12 -2.99 0.50 1.7508 32.4
13 56.93 5.13
14 ∞ 0.40 1.5163 64.1
15 ∞ 0.10
Image plane ∞
ERFS [5]
RY 5.00
θ 5.04
R -0.44
ERFS [4]
RY 1.75
θ 40.71
R -1.14
Eccentricity (7)
X 0.00 Y 0.00 Z -1.33
α 0.00 β 0.00 γ 0.00
Eccentricity (5)
X 0.00 Y 0.00 Z -0.38
α 0.00 β 0.00 γ 0.00
Eccentricity (6)
X 0.00 Y 0.00 Z 1.77
α 0.00 β 0.00 γ 0.00.

Example 2
Side-viewing optical path surface number of curvature radius Surface spacing Eccentric refractive index Abbe number Side-viewing optical path surface number Curvature radius Surface spacing Eccentricity Refractive index Abbe number Object surface ∞ ∞ Eccentricity (1)
1 ERFS [1] Eccentricity (2) 1.8348 42.7
2 ASS [1] (RE) Eccentricity (3) 1.8348 42.7
3 11.26 (RE) Eccentricity (4) 1.8348 42.7
4 ASS [1] Eccentricity (3)
5 ∞ (aperture) 0.10 Eccentricity (5)
6 -1.59 2.00 1.7292 54.7
7 -2.02 0.10
8 4.80 1.00 1.8467 23.8
9 2.52 2.50 1.7440 44.8
10 -12.02 3.62
11 ∞ 0.40 1.5163 64.1
12 ∞ 0.10
Image plane ∞ 0.00
ERFS [1]
RY ∞
θ 90.00
R -3.00
ASS [1]
R 3.25
k -7.5002e-1
Eccentricity (1)
X 0.00 Y 0.00 Z 0.00
α 90.00 β 0.00 γ 0.00
Eccentric [2]
X 0.00 Y 0.00 Z -0.03
α 0.00 β 0.00 γ 0.00
Eccentric [3]
X 0.00 Y 0.00 Z -0.91
α 0.00 β 0.00 γ 0.00
Eccentric [4]
X 0.00 Y 0.00 Z -1.73
α 0.00 β 0.00 γ 0.00
Eccentric [5]
X 0.00 Y 0.00 Z 0.55
α 0.00 β 0.00 γ 0.00
Direct-view optical path number Curvature radius Surface spacing Eccentricity Refractive index Abbe number Object surface ∞ ∞
1 ∞ 0.80 1.7292 54.7
2 4.61 3.57
3 11.26 Eccentricity (4) 1.8348 42.7
4 3.25 Eccentricity (3)
5 ∞ (aperture) 0.10 Eccentricity (5)
6 -1.59 2.00 1.7292 54.7
7 -2.02 0.10
8 4.80 1.00 1.8467 23.8
9 2.52 2.50 1.7440 44.8
10 -12.02 3.62
11 ∞ 0.40 1.5163 64.1
12 ∞ 0.10
Image plane ∞ 0.00
Eccentric [4]
X 0.00 Y 0.00 Z -1.73
α 0.00 β 0.00 γ 0.00
Eccentric [3]
X 0.00 Y 0.00 Z -0.91
α 0.00 β 0.00 γ 0.00
Eccentric [5]
X 0.00 Y 0.00 Z 0.55
α 0.00 β 0.00 γ 0.00.

Example 3
Side-viewing optical path number of curvature radius Surface spacing Eccentricity Refractive index Abbe number Object surface ∞ ∞ Eccentricity (1)
1 ERFS [1] Eccentricity (2) 1.5163 64.1
2 ASS [1] (RE) Eccentricity (3) 1.5163 64.1
3 15.47 (RE) Eccentricity (4) 1.5163 64.1
4 ASS [1] Eccentricity (3)
5 -8.96 0.55 Eccentricity (5) 1.4875 70.4
6 0.88 0.50
7 ∞ (Aperture) 0.50
8 -3.52 0.50 1.7552 27.6
9 -25.30 1.50 1.7440 44.8
10 -2.04 0.10
11 9.45 1.00 1.8467 23.8
12 2.95 2.50 1.6204 60.3
13 -5.81 8.41
14 ∞ 0.40 1.5163 64.1
15 ∞ 0.10
Image plane ∞
ERFS [1]
RY ∞
θ 90.00
R -3.00
ASS [1]
R 4.01
k -3.0163e-1
Eccentricity (1)
X 0.00 Y -5.00 Z 0.00
α 90.00 β 0.00 γ 0.00
Eccentric [2]
X 0.00 Y 0.00 Z -0.03
α 0.00 β 0.00 γ 0.00
Eccentric [3]
X 0.00 Y 0.00 Z -0.78
α 0.00 β 0.00 γ 0.00
Eccentric [4]
X 0.00 Y 0.00 Z -1.37
α 0.00 β 0.00 γ 0.00
Eccentric [5]
X 0.00 Y 0.00 Z 0.16
α 0.00 β 0.00 γ 0.00
Direct-view optical path number Curvature radius Surface spacing Eccentricity Refractive index Abbe number Object surface ∞ ∞
1 8.69 0.80 1.5163 64.1
2 1.65 2.86
3 15.47 Eccentricity (4) 1.8348 42.7
4 4.01 Eccentricity (3)
5 -8.96 0.55 Eccentricity (5) 1.4875 70.4
6 0.88 0.50
7 ∞ (Aperture) 0.50
8 -3.52 0.50 1.7552 27.6
9 -25.30 1.50 1.7440 44.8
10 -2.04 0.10
11 9.45 1.00 1.8467 23.8
12 2.95 2.50 1.6204 60.3
13 -5.81 8.41
14 ∞ 0.40 1.5163 64.1
15 ∞ 0.10
Image plane ∞
Eccentric [4]
X 0.00 Y 0.00 Z -1.37
α 0.00 β 0.00 γ 0.00
Eccentric [3]
X 0.00 Y 0.00 Z -0.78
α 0.00 β 0.00 γ 0.00
Eccentric [5]
X 0.00 Y 0.00 Z 0.16
α 0.00 β 0.00 γ 0.00.

Example 4
Side-viewing optical path number of curvature radius Surface spacing Eccentricity Refractive index Abbe number Object surface ∞ ∞ Eccentricity (1)
1 ERFS [1] Eccentricity (2) 1.5163 64.1
2 ASS [1] (RE) Eccentricity (3) 1.5163 64.1
3 14.19 (RE) Eccentricity (4) 1.5163 64.1
4 ASS [1] Eccentricity (3)
5 -3.01 0.55 Eccentricity (5) 1.4875 70.4
6 1.10 0.50
7 ∞ (Aperture) 0.50
8 -4.75 0.50 1.7209 29.1
9 43.27 1.50 1.7440 44.8
10 -2.26 0.10
11 16.57 1.00 1.8467 23.8
12 3.66 2.50 1.6204 60.3
13 -4.87 9.25
14 ∞ 0.40 1.5163 64.1
15 ∞ 0.10
Image plane ∞
ERFS [1]
RY ∞
θ 90.00
R -4.00
ASS [1]
R 4.40
k -7.3106e-1
Eccentricity (1)
X 0.00 Y 0.00 Z 0.00
α 90.00 β 0.00 γ 0.00
Eccentric [2]
X 0.00 Y 0.00 Z -0.02
α 0.00 β 0.00 γ 0.00
Eccentric [3]
X 0.00 Y 0.00 Z -1.12
α 0.00 β 0.00 γ 0.00
Eccentric [4]
X 0.00 Y 0.00 Z -2.28
α 0.00 β 0.00 γ 0.00
Eccentric [5]
X 0.00 Y 0.00 Z 0.06
α 0.00 β 0.00 γ 0.00
Direct-view optical path number Curvature radius Surface spacing Eccentricity Refractive index Abbe number Object surface ∞ ∞
1 9.42 0.80 1.5163 64.1
2 2.13 2.35
3 -4.29 0.80 1.5163 64.1
4 -3.86 2.38
5 14.19 0.00 Eccentricity (5) 1.8348 42.7
6 ASS [1] 0.00 Eccentricity (4)
7 -3.01 0.55 Eccentricity (6) 1.4875 70.4
8 1.10 0.50
9 ∞ (Aperture) 0.50
10 -4.75 0.50 1.7209 29.1
11 43.27 1.50 1.7440 44.8
12 -2.26 0.10
13 16.57 1.00 1.8467 23.8
14 3.66 2.50 1.6204 60.3
15 -4.87 9.25
16 ∞ 0.40 1.5163 64.1
17 ∞ 0.10
Image plane ∞
ASS [1]
R 4.40
k -7.3106e-1
Eccentric [4]
X 0.00 Y 0.00 Z -2.28
α 0.00 β 0.00 γ 0.00
Eccentric [3]
X 0.00 Y 0.00 Z -1.12
α 0.00 β 0.00 γ 0.00
Eccentric [5]
X 0.00 Y 0.00 Z 0.06
α 0.00 β 0.00 γ 0.00.

Example 5
Side-viewing optical path number of curvature radius Surface spacing Eccentricity Refractive index Abbe number Object surface ∞ ∞ Eccentricity (1)
1 ERFS [1] Eccentricity (2) 1.5163 64.1
2 ASS [1] (RE) Eccentricity (3) 1.5163 64.1
3 ASS [2] (RE) Eccentricity (4) 1.5163 64.1
4 ASS [1] Eccentricity (3)
5 -3.66 0.55 Eccentricity (5) 1.7440 44.8
6 -2.96 0.50
7 ∞ (Aperture) 3.00
8 Ideal lens 3.58
Image plane ∞
ERFS [1]
RY ∞
θ 90.00
R -4.00
ASS [1]
R 5.11
k 1.3753e + 0
ASS [2]
R 13.09
k 0.0000
Eccentric [1]
X 0.00 Y -5.00 Z 0.00
α 90.00 β 0.00 γ 0.00
Eccentric [2]
X 0.00 Y -4.00 Z -0.04
α 90.00 β 0.00 γ 0.00
Eccentric [3]
X 0.00 Y 0.00 Z -0.87
α 0.00 β 0.00 γ 0.00
Eccentric [4]
X 0.00 Y 0.00 Z -1.64
α 0.00 β 0.00 γ 0.00
Eccentric [5]
X 0.00 Y 0.00 Z 1.17
α 0.00 β 0.00 γ 0.00
Direct-view optical path number Curvature radius Surface spacing Eccentricity Refractive index Abbe number Object surface ∞ ∞
1 205.85 0.80 1.5163 64.1
2 2.32 2.30
3 ASS [2] (RE) Eccentricity (4) 1.5163 64.1
4 ASS [1] Eccentricity (3)
5 -3.66 0.55 Eccentricity (5) 1.7440 44.8
6 -2.96 0.50
7 ∞ (Aperture) 3.00
8 Ideal lens 3.58
Image plane ∞
ASS [1]
R 5.11
k 1.3753e + 0
ASS [2]
R 13.09
k 0.0000
Eccentric [3]
X 0.00 Y 0.00 Z -0.87
α 0.00 β 0.00 γ 0.00
Eccentric [5]
X 0.00 Y 0.00 Z 1.17
α 0.00 β 0.00 γ 0.00.

  Further, when the outer shape of the optical element is D and the outer shape of the image of the reflected light path is Dr, the following is obtained.

Example 1 Example 2 Example 3 Example 4 Example 5
D 6.00 6.00 6.00 8.00 8.00
Dr 4.96 4.90 4.94 4.94 4.99
D / Dr 1.21 1.22 1.21 1.62 1.60.

  In the above embodiment, the transmission surface and the reflection surface of a transparent medium having a refractive index larger than 1 concentric with the central axis 2 of the optical system 1 are designed as extended rotation free-form surfaces. When the rotational free-form surface is orthogonal to the rotationally symmetric surface and does not use a higher-order term, the configuration is equivalent to a spherical surface.

  In addition, the reflecting surface and the refracting surface of the front group 10 are each designed with an extended rotation free-form surface formed by rotating a line segment of an arbitrary shape around the rotational symmetry axis 1 and having no surface top on the rotational symmetry axis 1. However, each may be replaced with an arbitrary curved surface.

  In addition, the optical system of the present invention uses an equation that includes an odd-order term in an expression that defines a line segment of an arbitrary shape that forms a rotationally symmetric surface, so that the inclination of the image plane 5 caused by decentering or back projection of the stop The pupil aberration is corrected.

  Further, by using the transparent medium rotationally symmetric around the central axis 2 constituting the front group 10 of the present invention as it is, it is possible to shoot or project an image having an angle of view of 360 ° in all directions. By cutting the cross section including the central axis 2 to make it half, one third, two thirds, etc., the angle of view around the central axis 2 is 180 °, 120 °, 240 °, etc. May be taken or projected.

  The optical system of the present invention has been described above as an imaging or observation optical system that obtains an image having 360 ° omnidirectional (all circumference) angles of view including the zenith with the central axis (rotation symmetry axis) 1 in the vertical direction. The present invention is not limited to the photographing optical system and the observation optical system, but can also be used as a projection optical system that projects an image on a 360 ° omnidirectional (all circumference) angle of view including the zenith with the optical path reversed. The endoscope can also be used as an all-round observation optical system of an in-tube observation apparatus.

  FIG. 18 shows an arrangement example of the image and the image sensor of the present embodiment. FIG. 18A shows an example in which an image sensor with a screen ratio of 16: 9 is used. When an image in the vertical direction is not used, it is preferable to match the size of the image sensor 50 with the left and right positions of the image A1 in the side viewing optical path A. FIG. 18B is an example in which the image sensor 50 having a screen ratio of 4: 3 is used, and the size of the image sensor 50 is matched with the image B1 in the direct-view optical path B, and is the same as FIG. Shows the case where the image in the vertical direction is not used. FIG. 18C shows an example in which the image sensor 50 having a screen ratio of 4: 3 is used, and the size of the image sensor 50 is matched with the image A1 in the side viewing optical path A. Thus, when arranged, both the image A1 of the side viewing optical path A and the image B1 of the direct viewing optical path B can be captured.

  Hereinafter, as an application example of the optical system 1 of the present invention, a usage example of the photographing optical system 101 or the projection optical system 102 will be described. FIG. 19 is a diagram for illustrating an example in which the photographing optical system 101 according to the present invention is used as the photographing optical system at the distal end of the endoscope. FIG. 19A illustrates the present invention at the distal end 101 of the rigid endoscope 110. This is an example of imaging and observing 360 ° omnidirectional images by attaching the photographing optical system. FIG. 19B shows a schematic configuration of the tip. Around the entrance surface 21 of the front group Gf of the panoramic imaging optical system 101 according to the present invention, a flare stop 107 including a casing having an opening 106 extending in a slit shape in the circumferential direction is arranged so that flare light is incident thereon. It is preventing. FIG. 19C shows a panoramic imaging optical system 101 according to the present invention attached to the tip of the soft electronic endoscope 113 in the same manner, and the image captured on the display device 114 is subjected to image processing to correct distortion. This is an example of displaying.

  FIG. 20 shows an example in which the photographing optical system 101 according to the present invention is attached to the capsule endoscope 120 and images of 360 ° omnidirectional images are taken and observed. The aperture 106 extending in a slit shape in the circumferential direction around the side-view first transmission surface 21 of the front group Gf second group in the side-view optical path A of the photographing optical system 101 according to the present invention, and the front group in the direct-view optical path B A flare stop 107 is formed in a casing or the like having a circular opening 106 in front of the first-view first transmitting surface 11 of the first group of Gf to prevent the flare light from entering.

  As shown in FIGS. 19 and 20, by using the photographing optical system 101 for an endoscope, an image behind the photographing optical system 101 can be picked up and observed, and various parts are picked up and observed from angles different from the conventional ones. can do.

  FIG. 21 (a) shows an image obtained by attaching a photographic optical system 101 according to the present invention as a photographic optical system in front of an automobile 130, and performing image processing on an image photographed through each photographic optical system 101 on a display device in a vehicle. FIG. 21B is a diagram showing an example in which distortion is corrected and simultaneously displayed, and FIG. 21B shows a photographing optical system 101 according to the present invention as a photographing optical system at each corner of the automobile 130 or the top of the pole of the head portion. It is a figure which shows the example which attached the plurality and displayed the image image | photographed through each imaging | photography optical system 101 on the display apparatus in a vehicle, performing image processing and correct | amending distortion simultaneously. In this case, as shown in FIG. 18A, it is preferable to match the size of the image sensor 50 to the left and right positions of the image A1 in the side viewing optical path A, because the left and right images can be captured widely.

  Further, FIG. 22 uses the projection optical system 102 according to the present invention as the projection optical system of the projection device 140, displays a panoramic image on a display element arranged on the image plane 5, and 360 ° in all directions through the projection optical system 102. This is an example in which a 360 ° omnidirectional image is projected and displayed on the arranged screen 141.

  Further, FIG. 23 shows that the photographing apparatus 151 using the photographing optical system 101 according to the present invention is attached to the outside of the building 150, and the projection apparatus 151 using the photographing optical system 101 according to the present invention is disposed indoors. It connects so that the imaged image may be sent to the projection device 140 via the electric wire 152. In such an arrangement, a 360 ° omnidirectional outdoor subject O is photographed by the photographing device 151 via the photographing optical system 101, and the video signal is sent to the projection device 140 via the electric wire 152 and disposed on the image plane. In this example, the image is displayed on the display element, and the image O ′ of the subject O is projected and displayed on an indoor wall surface or the like through the projection optical system 102.

It is a figure for demonstrating the coordinate system of the optical system of this invention. It is a figure which shows the principle of an extended rotation free-form surface. It is sectional drawing taken along the central axis of the optical system of Example 1 of this invention. FIG. 3 is a diagram illustrating lateral aberrations of the entire optical system in a side view optical path according to the first exemplary embodiment. FIG. 3 is a diagram illustrating lateral aberrations of the entire optical system in a direct-view optical path according to Example 1. It is sectional drawing taken along the central axis of the optical system of Example 2 of this invention. 6 is a lateral aberration diagram of the whole optical system in a side viewing optical path according to Example 2. FIG. 6 is a lateral aberration diagram of the entire optical system in a direct-view optical path according to Example 2. FIG. It is sectional drawing taken along the central axis of the optical system of Example 3 of this invention. 10 is a lateral aberration diagram of the whole optical system in a side viewing optical path according to Example 3. FIG. FIG. 10 is a transverse aberration diagram for the whole optical system in the direct-view optical path according to Example 3. It is sectional drawing taken along the central axis of the optical system of Example 4 of this invention. FIG. 10 is a lateral aberration diagram of the whole optical system in the side viewing optical path according to Example 4. FIG. 10 is a transverse aberration diagram for the whole optical system in the direct-view optical path according to Example 4. It is sectional drawing taken along the central axis of the optical system of Example 5 of this invention. FIG. 10 is a transverse aberration diagram for the whole optical system in the side viewing optical path according to Example 5. 10 is a transverse aberration diagram for the whole optical system in the direct-view optical path according to Example 5. FIG. It is a figure which shows the example of arrangement | positioning of the image of the optical system of this invention, and an image pick-up element. It is a figure which shows the example which used the optical system of this invention as an imaging | photography optical system of the endoscope front-end | tip. It is a figure which shows the example which used the optical system of this invention as the imaging | photography optical system of a capsule endoscope. It is a figure which shows the example which used the optical system of this invention as the imaging | photography optical system of a motor vehicle. It is a figure which shows the example which used the optical system of this invention as a projection optical system of a projection apparatus. It is a figure which shows the example which used the optical system of this invention as an imaging | photography optical system which image | photographs a to-be-photographed object.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Optical system central axis 2 ... Central axis 3 ... Side view object surface 4 ... Direct view object surface 5 ... Image surface

Claims (18)

Consisting of a transparent medium having a refractive index rotationally symmetric around the central axis greater than 1.
The transparent medium includes a first transmission surface, a first reflection surface disposed closer to a central axis than the first transmission surface, and a second reflection surface disposed on the opposite side of the image surface from the first reflection surface. , and a second transmitting surface located on an image plane side of the second reflecting surface, a third transmissive surface and a fourth transmissive surface arranged from the image plane side and the third transmissive surface, the,
The light beam incident on the transparent medium has a side viewing optical path and a direct viewing optical path, and in the order of forward ray tracing,
The side viewing optical path enters the transparent medium through the first transmission surface, is reflected by the first reflection surface to the side opposite to the image surface, is reflected by the second reflection surface to the image surface side, and Constituting a substantially Z-shaped optical path going out from the transparent medium to the image plane side through two transmission surfaces;
The direct-view optical path constitutes an optical path that enters the transparent medium through the third transmission surface and exits from the transparent medium to the image plane side through the fourth transmission surface ;
An optical element that does not form an intermediate image in the direct-view optical path and the side-view optical path .   The optical element according to claim 1, wherein the side viewing optical path is configured only on one side with respect to the central axis.   The second transmission surface is disposed in the vicinity of the central axis, the first reflection surface and the second reflection surface are disposed in the periphery thereof, and the first transmission surface is disposed in the outermost peripheral portion. The optical element according to claim 1.   4. The optical element according to claim 1, wherein the first reflection surface is a surface having the same position and the same shape as the second transmission surface. 5.   5. The optical element according to claim 1, wherein the first reflection surface is a surface having the same position and the same shape as the fourth transmission surface.   6. The optical element according to claim 1, wherein the second reflecting surface is a surface having the same position and the same shape as the third transmitting surface.   The optical element according to claim 1, wherein the first reflection surface and the second reflection surface have a total reflection function.   The optical element according to claim 1, wherein the first transmission surface is a cylindrical or conical surface.   At least one of the first reflecting surface and the second reflecting surface is formed of an extended rotation free-form surface formed by rotating an arbitrary-shaped line segment having no symmetry plane around the central axis. The optical element according to any one of claims 1 to 8, wherein:   The at least one surface among the surfaces of the transparent medium is configured by an extended rotation free-form surface formed by rotating an arbitrary-shaped line segment including an odd-numbered term around a central axis. The optical element according to claim 1.   A front group, a rear group disposed closer to the image plane than the front group, and an aperture disposed between the front group and the rear group, and the optical element is disposed in the front group, 11. The direct-view optical path images or projects an object point near the central axis, and the side-view optical path images or projects an object point around the central axis. An optical system comprising the optical element described in 1.   The side-view optical path and the direct-view optical path share a part of the optical element to form a circular image of the direct-view optical path and an annular image of the side-view optical path on the outer periphery thereof in the same plane. The optical system according to claim 11.   The optical system according to claim 11, wherein the second reflecting surface is disposed with a concave surface facing the opening side.   The optical system according to claim 11, wherein the first reflecting surface is disposed with a concave surface facing the opening. When the outer shape of the optical element is D ,
D <10mm
Optical system according to any one of claims 11 to 14, characterized by satisfying the following condition. When the outer shape of the image of the side viewing optical path is Dr,
D / Dr <2
Optical system according to any one of claims 11 to 15, characterized by satisfying the following condition. The optical system according to claim 1, wherein the first reflecting surface has a negative power, and the second reflecting surface has a positive power.   An endoscope using the optical system according to any one of claims 11 to 17.

Images