Transmissive optical element and optical system using same

The present invention relates to a transmission optical element and an optical system using the same, and particularly to an objective optical system or an imaging optical system for forming an image of an object having a large angle of view on a flat ring-shaped image plane.

Conventionally, a wide-angle optical system such as a fisheye lens has been used as a means for imaging a peripheral portion having a wide angle of view. However, in order to perform wide-angle imaging, the number of optical systems involved has increased, and it has been difficult to apply it to small optical devices, especially endoscopes and capsule endoscopes.

Conventionally, Patent Document 1 has proposed to widen the observation range by making the inner surface of the hemispherical transparent cover at the tip of the capsule endoscope a conical surface, but the principle is not clear. Further, Patent Document 2 proposes a capsule endoscope having a conical surface on the front surface of the transparent cover at the tip of the capsule endoscope. However, this transparent cover is not used to widen the angle of view.<patcit num="1"><text>Japanese Unexamined Patent Publication No. 2001-174713</text></patcit><patcit num="2"><text>U.S. Pat. No. 5,604,531</text></patcit>

<p> The present invention has been made in view of such a situation of the prior art, and an object of the present invention is to capture an image having a wide shooting angle of view with a simple configuration, particularly from a direction mainly perpendicular to the central axis. It is an object of the present invention to provide a transmission optical element which is small in size and whose aberration is well corrected, and an optical system using the same.</p>

<p> The transmission optical element of the present invention that achieves the above object has at least one transmission surface in a transmission optical element made of a transparent medium having two rotationally symmetric transmission surfaces around the central axis and having a refractive index of more than 1. Is characterized in that, in the vicinity where the central axis and the transparent surface intersect, the normal line of the transparent surface has a shape at an angle with the central axis.</p><p> Further, the optical system of the present invention is an imaging system that forms an image of an object around the central axis on an image plane of a plane orthogonal to the central axis, and has a front group that is rotationally symmetric around the central axis and a central axis. The front group comprises a rear group that is rotationally symmetric and has positive power around the central axis, and the front group includes at least a transmissive optical element composed of a transparent medium having two rotationally symmetric transmissive surfaces around the central axis and having a refractive index greater than 1. One of them is provided, and at least one of the transmission surfaces of the transmission optical element is characterized in that, in the vicinity of intersecting the central axis, the normal line of the transmission surface has a shape at an angle with the central axis. ..</p><p> In this case, it is desirable to have an opening coaxially arranged on the central axis between the transmission optical element and the rear group or in the rear group.</p><p> Further, it is desirable that all the transmission surfaces of the transmission optical element have a surface shape in which a concave surface is directed with respect to the opening.</p><p> Further, when a light ray passing through the opening center from the angle of view center in the direction along the central axis is used as the main light ray, the point where the main light ray hits the first transmission surface of the transmission optical element and the second transmission surface are mainly. When the angle formed by the tangents of the two surfaces at the point where the light beam hits is θ (°), it is desirable to satisfy the condition of 1 ° &lt;θ &lt;90 ° (1).</p><p> Further, it is desirable that at least the transmissive optical element on the most object side of the front group includes a light-shielding member that blocks light rays from the central axis.</p><p> Further, it is desirable that the rear group consists of a rotationally symmetric optical system concentric with the central axis.</p><p> Further, it is desirable that the rear group having the positive power corrects the chromatic aberration of magnification generated by the front group.</p><p> Further, it is desirable that a cylindrical or spherical 360 ° full-circle image is formed on a two-dimensional image sensor arranged on the image plane.</p><p> Further, the transmission surface having a shape in which the normal line forms an angle with the central axis in the vicinity of the intersection with the central axis is a rotationally symmetric shape formed by rotating an arbitrary curved curve having no symmetrical surface around the central axis. It is desirable to have.</p><p> Further, the transmission surface having a shape whose normal is at an angle with the central axis in the vicinity of the intersection with the central axis has a rotationally symmetric shape formed by rotating an arbitrary curved curve including an odd-order term around the central axis. It is desirable to have.</p><p> Further, the present invention also includes an optical system used as an optical system for projecting an image arranged on an image plane onto an object plane.</p>

<p> According to the above invention, a small transmission optical element capable of capturing and projecting a wide angle of view image with a simple configuration and satisfactorily correcting aberrations and an optical system using the same are obtained. be able to.</p>

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

FIG. 1 is a cross-sectional view taken along the central axis (rotational symmetry axis) 1 of the optical system of the first embodiment. The following description will be given as an imaging optical system that forms an image of an object surface 6 that is rotationally symmetric around the central axis 1 on an image plane 7 of a plane orthogonal to the central axis 1, but the optical path is reversed. It can also be used as a projection optical system that projects the image plane 7 onto the object plane 6.

First, the transmission optical element and the optical system of the present invention will be described with reference to Example 1 of FIG. The optical system of FIG. 1 is arranged on the image plane 7 side of the front group 3 and the front group 3 having at least one transmission optical element 2 having a rotationally symmetric shape around the central axis 1, and has normal rotational symmetry optics. It consists of a system, consisting of a rear group 4 that is rotationally symmetric and has positive power around the central axis 1, and an opening throttle 5 is arranged coaxially with the central axis 1 between the front group 3 and the rear group 4 or inside the rear group 4. Being done.

In this embodiment, one transmission optical element 2 which is a component of the front group 3 is centered on both the two transmission surfaces 21 and 22 in the cross section including the central axis 1 (the surface of FIG. 1) according to the present invention. An arbitrary curve is placed at a position away from the axis 1, and the curve is composed of an extended rotation free curved surface formed by rotating the curve around the central axis 1. Both transmission surfaces 21 and 22 are located in the vicinity of the central axis 1. The normal lines of the transparent surfaces 21 and 22 have a shape at an angle with the central axis 1. The extended free-form surface of rotation will be described later.

The transmission optical element 2 of the front group 3 has at least one transmission surface 21 and 22 composed of an extended free-rotating curved surface in this way, and has a normal of the transmission surfaces 21 and 22 in the vicinity of intersecting the central axis 1. Has a shape that makes an angle with the central axis 1. Therefore, in the cross section including the central axis 1 (meridional cross section), the light beam from the peripheral image is applied to the central axis 1 with respect to the central axis 1 in front of the rear group 4 (central axis). Convert to a light beam from an image (direction along 1). The rear group 4 acts as an optical system that projects the front image (real image or virtual image) whose angle of view is transformed by the front group 3 onto the image plane 7 as a ring-shaped image.

The transmission optical element 2 of the front group 3 as an angle-of-view conversion element for converting the angle of view has a substantially wedge-shaped shape in which the thickness of the meridional cross section increases from the central axis 1 toward the periphery around the central axis 1. It is important that the shape is obtained by rotating with. Since this wedge-shaped refraction action is arranged rotationally symmetrically with the central axis 1 as the center of rotation, it is possible to reasonably guide the light beam coming from the direction substantially orthogonal to the central axis 1 to the rear group 4.

On the other hand, in a conventional fisheye lens or the like, a similar strong negative meniscus-shaped lens is arranged on the first surface to obtain the same effect, but when the imaging performance on the central axis 1 is not particularly required, The shape of the surface does not have to be continuous in the vicinity of the central axis 1, and it is easier to obtain the refraction action in the periphery if the surface shape is discontinuous.

Therefore, in this embodiment, both the two transparent surfaces 21 and 22 are configured as discontinuous surfaces at one position on the central axis.

Further, by arranging an aperture diaphragm 5 coaxial with the central axis and an optical system (rear group 4) having positive power on the image side of the transmission optical element 2, only the luminous flux limited by the aperture diaphragm 5 is placed in the rear group 4. It is possible to capture or project a high-contrast image without incident matter.

More preferably, in order to reduce the occurrence of coma aberration, it is important to configure the two transmission surfaces 21 and 22 of the transmission optical element 2 in a surface shape in which the concave surface faces the aperture diaphragm 5.

More preferably, as shown in FIG. 4, the region of the transmission surfaces 21 and 22 near the central axis 1 is an image in one direction of the central axis by forming discontinuous optical surfaces such as parallel surfaces 23 and 24. It is possible to form an image on the image plane 7 and take an image.

More preferably, when the light ray passing from the center of the angle of view to the center of the aperture aperture 5 is the main light ray 10, the point where the main light ray 10 hits the first transmission surface 21 of the transmission optical element 2 on the most object side and the second transmission surface. When the angle formed by the tangents of the two surfaces at the point where the main ray 10 hits 22 is θ (°), it is preferable to satisfy the condition of 1 ° &lt;θ &lt;90 ° ··· (1).

If it exceeds the lower limit of 1 ° in the above conditional expression (1), the amount of conversion of the angle of view in the transmission optical element 2 becomes small, and a wide peripheral visual field cannot be obtained. On the other hand, if the upper limit of 90 ° is exceeded, the amount of conversion of the angle of view becomes too large, the occurrence of chromatic aberration becomes large, and it becomes impossible to correct in other aspects.

More preferably, when such a large conversion angle is required, it is preferable to use two or more sets of transmission optical elements based on the present invention.

More preferably, it is preferable to satisfy the condition of 10 ° &lt;θ &lt;60 ° ... (1-1).

The values of θ in Examples 1 to 7 described later are as follows.

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 θ 44.60 ° 45.79 ° 58.62 ° 34.215 ° 33.667 ° 30.962 ° 25.8923 ° More preferably, the rear group 4 with positive power By configuring the optical system concentrically with the central axis 1 and rotationally symmetric, the transmission optical element 2 can be used as an attachment optical system of a general optical system.

More preferably, since the transmission optical element 2 has a strong wedge action, it is desirable to use a glass material having a small dispersion, but a glass having a small dispersion (a large Abbe number) has a relatively low refractive index and aberration. The chromatic aberration generated by the transmission optical element 2 becomes large due to the correction. In such a case, it is possible to increase the resolving power by correcting the chromatic aberration generated in the transmission optical element 2 in the rear group 4. Further, since the chromatic aberration mainly generated in the transmission optical element 2 is the chromatic aberration of magnification, in the case of the imaging optical system, the size of the electronically captured image is corrected, and in the case of the projection optical system, it is on the display element. By correcting the size of the image in advance for each color, it is possible to obtain an image with high resolution with little chromatic aberration as a whole.

More preferably, in this embodiment, the wedge effect is obtained by the rotationally symmetric surface shape, but the wedge effect is not limited to this, and has the effect of bending light rays (electromagnetic waves) such as HOE, DOE, inhomogeneous medium, and Fresnel lens. It can be realized on a transmissive surface, in which case it is important to set the refraction action discontinuously near the central axis 1, and on a surface that has the action of converting the angle formed by the incident light beam and the central axis 1 from large to small. Any aspect is possible if there is.

Further, it is composed of such a transmission optical element 2, an aperture diaphragm 5 arranged coaxially with the central axis 1, and a rear group 4 having a coaxial positive power and having a condensing action.

More preferably, the transmission surfaces 21 and 22 of the transmission optical element 2 have different powers in the sagittal cross section (the cross section orthogonal to the meridional cross section and including the main ray 10) and the meridional cross section, so that astigmatism occurs. .. The generated astigmatism is rotationally symmetric astigmatism, but it is not a straightforward astigmatism that occurs in a rotationally symmetric system. Therefore, it is desirable to arrange an aspherical surface having an action of correcting this astigmatism in the vicinity of the image plane 7.

More preferably, as the surface for correcting astigmatism, an extended free-form surface with different powers in the sagittal cross section and the meridional cross section is arranged near the image plane.

Further, the transmission surfaces 21 and 22 of the transmission optical element 2 use a rotationally symmetric surface shape formed by rotating an arbitrary curved curve having no symmetrical surface around the central axis 1, so that the peripheral portion of the angle of view is used. It is possible to correct the distortion of.

Further, it is desirable that at least the transmissive optical element 2 on the most object side of the front group 3 is provided with a light-shielding member that blocks light rays from the central axis 1. Since the imaging light from the object surface 6 is not incident on the vicinity of the central axis 1 of the transmission optical element 2, by blocking this position with a light-shielding member, unnecessary light such as flare light can be incident on the optical system. Can be prevented.

More preferably, this curve is a curve having an arbitrary shape including odd-order terms. This odd-numbered term makes it possible to give a shape that is vertically asymmetric with respect to the center of the angle of view, which is preferable in terms of aberration correction.

Hereinafter, Examples 1 to 7 of the optical system of the present invention will be described in more detail. The constituent parameters of these optical systems will be described later. The constituent parameters of these examples are based on the results of forward ray tracing from the object surface 6 through the front group 3 and the rear group 4 to the image plane 7, as shown in FIG. 1, for example.

The coordinate system is a point (Examples 1 and 2) in which the point where the main ray 10 intersects the object plane 6 is projected onto the axis of rotational symmetry (central axis) 1 in the forward ray tracking, for example, as shown in FIG. The origin of the eccentric optical plane of the eccentric optical system is the point (Examples 3 to 7) where the point where the main ray 10 intersects the first transmission plane 21 of the transmission optical element 2 is projected onto the axis of rotational symmetry (central axis) 1. Let the direction away from the image plane 7 of the axis of rotational symmetry (central axis) 1 be the positive direction of the Y axis, and the inside of the paper surface of FIG. 1 be the YZ plane. Then, the direction on the page of FIG. 1 opposite to the object side currently considered is the Z-axis positive direction, and the Y-axis and the Z-axis and the axes constituting the right-hand Cartesian coordinate system are the X-axis positive directions.

Regarding the eccentric surface, the amount of eccentricity from the center of the origin of the above optical system in the coordinate system in which the surface is defined (X, Y, Z in the X-axis direction, Y-axis direction, and Z-axis direction, respectively) and the optical system The tilt angles (α, β, γ (°)) of the coordinate system that defines each surface centered on each of the X-axis, Y-axis, and Z-axis of the coordinate system defined at the origin are given. In that case, the positive of α and β means counterclockwise with respect to the positive direction of each axis, and the positive of γ means clockwise with respect to the positive direction of the Z axis. The method of rotating α, β, and γ of the central axis of a surface is to rotate the coordinate system that defines each surface by α counterclockwise around the X axis of the coordinate system defined at the origin of the optical system. Then, β-rotate counterclockwise around the Y-axis of the new rotated coordinate system, and then γ-rotate clockwise around the Z-axis of the new rotated coordinate system. Is.

Further, among the optical working surfaces constituting the optical system of each embodiment, when a specific surface and a surface following it form a coaxial optical system, a surface spacing is given, and the radius of curvature of the surface, The refractive index and Abbe number of the medium are given according to the conventional method.

The item related to the aspherical surface for which no data is described in the constituent parameters described later is 0. The refractive index and 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 represented by the amount of eccentricity from the origin of the optical system.

The extended free-form surface of rotation is a plane of rotational symmetry given by the following definition.

First, the following curve (b) passing through the origin on the YZ coordinate plane is determined.

Z = (Y²/ RY) / [1+ {1- (C₁+1) Y²/ RY²}^{1 /2}]

C₂Y + C₃Y²+ C₄Y³+ C₅Y⁴+ C₆Y⁵+ C₇Y⁶ + + C₂₁Y²⁰+ + C_{n + 1}Yⁿ+ ······························································································································································· (b) Next, a curve F (Y) is determined by rotating this curve (b) by an angle θ (°) with the counterclockwise direction facing the positive direction of the X axis. This curve F (Y) also passes through the origin on the YZ coordinate plane.

The curve F (Y) is translated in the Z positive direction by a distance R (Z negative direction when negative), and then the parallel movement curve is rotated around the Y axis to extend the rotation symmetry plane. It is a free curved line.

As a result, the extended rotating free surface becomes a free surface (free curve) in the YZ plane and a circle with radius | R | in the XZ plane.

From this definition, the Y-axis is the axis of the extended free-form surface (rotational symmetry axis).

Where RY is the radius of curvature of the spherical term in the YZ cross section, C₁Is a conical constant, C₂, C₃, C₄, C₅... are the aspherical coefficients of the 1st, 2nd, 3rd, 4th ... respectively.

Then, in the optical system of the present invention, it is desirable that at least one transmission surface of the front group 3 is such an extended free-form surface of rotation. By giving at least one transparent surface such a surface shape, it is possible to give a strong wedge action to the front group 3 in the meridional cross section, and it is possible to shoot or project a wide angle of view image. become able to.

FIG. 1 shows a cross-sectional view taken along the central axis (rotational symmetry axis) 1 of the optical system of the first embodiment.

The optical system of this embodiment is arranged on the image plane 7 side of the front group 3 and the front group 3 composed of a transmission optical element 2 made of a transparent medium that is rotationally symmetric around the central axis 1 and has a refractive index greater than 1. , Consists of a lens system consisting of two elements in two groups, consisting of a rear group 4 that is rotationally symmetric and has positive power around the central axis 1, and an aperture aperture 5 between the front group 3 and the rear group 4 is the central axis 1. The first transmission surface 21 of the transmission optical element 2 is arranged coaxially, and the first transmission surface 21 of the transmission optical element 2 rotates the central axis 1 along a curve consisting of an arc having a center at a position away from the central axis 1 in a cross section including the central axis 1. It is formed from a pointed extended free-rotating curved surface obtained by rotating it as an axis of symmetry, and the second transmission surface 22 is also rotationally symmetric with respect to the central axis 1 as a curve consisting of an arc having a center at a position away from the central axis 1. It is formed from a pointed extended free-rotating curved surface obtained by rotating it as an axis, and both the first transmission surface 21 and the second transmission surface 22 have a surface shape with a concave surface facing the opening aperture 5. Each of the transparent surfaces 21 and 22 has a shape such that the normal of the transparent surfaces 21 and 22 forms an angle with the central axis 1 in the vicinity where the central axis 1 and the transparent surfaces 21 and 22 intersect. The cross section including the axis 1 has a substantially wedge-shaped shape in which the thickness of the meridional cross section increases from the central axis 1 toward the periphery.

Then, in this embodiment, the object surface 6 is composed of an outer cylindrical surface 11 and an inner cylindrical surface 12 concentric with the central axis 1, and the outer cylindrical surface 11 of the transparent cylindrical body 8 for protecting the optical system of this embodiment. Is consistent with.

The rear group 4 is composed of a plano-convex regular lens L1 and a convex flat lens L2, and the aperture diaphragm 5 is arranged immediately before the plano-convex normal lens L1. The image plane 7 of this optical system coincides with the back surface of the parallel flat plate 9.

In this embodiment, the transparent cylinder 8 and the parallel flat plate 9 may be omitted.

With such a configuration, an image of an object with a wide angle of view of ± 4 mm on a cylindrical object surface 6 is a lens system of a transmission optical element 2 and an aperture 5 and a rear group 4 that are rotationally symmetric around the central axis 1. Then, a ring-shaped image is formed on the planar image plane 7 perpendicular to the central axis 1.

The specifications of Example 1 are object height ± 4 mm, numerical aperture (NA) 0.1, and image size φ0.26 to φ1.64 mm.

FIG. 2 shows the lateral aberration of the optical system of this embodiment. In this lateral aberration diagram, the number shown in the center indicates the relative object height, and indicates the lateral aberration in the Y direction (meridional direction) and the X direction (sagittal direction) at the object height. Hereinafter, the same applies to Example 2.

Further, FIG. 3 shows the relationship between the object height (mm) and the image height (mm) in the meridional cross section of this embodiment. In the figure, the linear straight line shows the case where the object height and the image height are in a linear relationship. Hereinafter, the same applies to Example 2.

FIG. 5 shows a cross-sectional view taken along the central axis (rotational symmetry axis) 1 of the optical system of the second embodiment.

The optical system of this embodiment is basically the same as that of the first embodiment, but is an optical system in which a hole 13 is provided in the center of the transmission optical element 2 and rotates around the central axis 1. It consists of a front group 3 consisting of a transparent optical element 2 made of a transparent medium having a symmetry and a refractive index of more than 1, and a lens system consisting of two elements in two groups arranged on the image plane 7 side of the front group 3 and having a central axis 1. It consists of a rear group 4 that is rotationally symmetric and has positive power around, and an aperture aperture 5 is arranged coaxially with the central axis 1 between the front group 3 and the rear group 4, and the second transmission optical element 2. 1 The transparent surface 21 has a pointed shape that can be freely rotated in a cross section including the central axis 1 by rotating a curve consisting of an arc having a center at a position away from the central axis 1 with the central axis 1 as the axis of rotational symmetry. An extended free rotation curved surface with a pointed shape obtained by rotating a curved surface formed from a curved surface and the second transparent surface 22 also having an arc having a center at a position away from the central axis 1 with the central axis 1 as the axis of rotational symmetry. Both the first transmission surface 21 and the second transmission surface 22 have a surface shape with a concave surface facing the opening aperture 5. Each of the transparent surfaces 21 and 22 has a shape such that the normal of the transparent surfaces 21 and 22 forms an angle with the central axis 1 in the vicinity where the central axis 1 and the transparent surfaces 21 and 22 intersect. The cross section including the axis 1 has a substantially wedge-shaped shape in which the thickness of the meridional cross section increases from the central axis 1 toward the periphery. Further, the transmission surface 21 and the transmission surface 22 intersect in the vicinity of the central axis 1, and a hole 13 centered on the central axis 1 is formed in the center.

Then, in this embodiment, the object surface 6 is composed of an outer cylindrical surface 11 and an inner cylindrical surface 12 concentric with the central axis 1, and the outer cylindrical surface 11 of the transparent cylindrical body 8 for protecting the optical system of this embodiment. Is consistent with.

The rear group 4 is composed of a plano-convex regular lens L1 and a convex flat lens L2, and the aperture diaphragm 5 is arranged immediately before the plano-convex normal lens L1. The image plane 7 of this optical system coincides with the back surface of the parallel flat plate 9.

In this embodiment, the transparent cylinder 8 and the parallel flat plate 9 may be omitted.

With such a configuration, the image of an object with a wide angle of view of ± 2 mm on the cylindrical object surface 6 is a transmission optical element 2 that is rotationally symmetric around the central axis 1, a lens system with an aperture of 5, and a lens system of the rear group 4. Then, a ring-shaped image is formed on the planar image plane 7 perpendicular to the central axis 1.

The specifications of Example 2 are object height ± 2.00 mm, numerical aperture (NA) 0.01, and image size φ0.45 to φ1.26 mm.

FIG. 6 shows the same lateral aberration as that of FIG. 2 of the optical system of this embodiment.

Further, FIG. 7 shows the relationship between the object height (mm) and the image height (mm) in the meridional cross section of this embodiment.

In this embodiment, the second transmission surface 22 of the transmission optical element 2 is arranged parallel to the central axis 1 and has a shape symmetrical with respect to a plane orthogonal to the central axis 1.

FIG. 8 shows a cross-sectional view of a modified example of the second embodiment. Two optical systems of this embodiment are arranged symmetrically with respect to a plane orthogonal to the central axis 1, and at that time, the transmission optical element 2 of one optical system and the transmission optical element 2'of the other optical system are arranged. It is configured as one common transmission optical element 20, and the rear groups 4, 4'and image planes 7, 7'are arranged above and below the direction along the central axis 1 of the transmission optical element 20, and is a common transparent cylinder. This is an example of forming an image of object surfaces 6 and 6'positioning in parallel vertically on the outer cylindrical surface of the body 8 on the respective image surfaces 7 and 7', and a wide object surface can be imaged at the same time. This is an example of

FIG. 9 shows a cross-sectional view of another modified example of the second embodiment. In this embodiment, a plane mirror 14 orthogonal to the central axis 1 is arranged between the front group 3 and the rear group 4 of the optical system of this embodiment so that the optical path is folded back, and the inside of the hole 13 is in the center of the transmission optical element 2. This is an example in which the rear group 4 and the image plane 7 are arranged in the rear group 4 to make the overall dimensions smaller.

FIG. 10 shows a cross-sectional view taken along the central axis (rotational symmetry axis) 1 of the optical system of the third embodiment.

In the optical system of this embodiment, the first transmission surface 21 of the transmission optical element 2 is composed of a convex spherical surface having a center on the central axis 1, and only the second transmission surface 22 has a curve having a higher-order term as the central axis 1. It is an optical system composed of a pointed extended free-rotating curved surface obtained by rotating the rear group 4 as an axis of rotational symmetry, and the rear group 4 having a lens configuration of 4 elements in 2 groups, and is rotationally symmetric around the central axis 1. The front group 3 consists of a transmission optical element 2 made of a transparent medium having a refractive index greater than 1, and the lens system is arranged on the image plane 7 side of the front group 3 and consists of 4 elements in 2 groups. It consists of a rear group 4 that is rotationally symmetric and has positive power around it, and an aperture aperture 5 is arranged coaxially with the central axis 1 between the front group 3 and the rear group 4, and is the first transmission optical element 2. The transmission surface 21 is formed by a spherical surface having a center on the central axis 1 and having a convex surface oriented in the positive direction of the Y axis, and the second transmission surface 22 is a curve formed by adding the cubic and quaternary terms of Y to the spherical term. Is formed from a pointed extended free-rotating curved surface obtained by rotating with the central axis 1 as the axis of rotational symmetry, and both the first transmission surface 21 and the second transmission surface 22 have concave surfaces facing the opening aperture 5. It has a shape. The second transmission surface 22 has a shape such that the normal line of the transmission surface 22 forms an angle with the central axis 1 in the vicinity of the intersection with the central axis 1, and the transmission optics in the cross section including the central axis 1 The element 2 has a substantially wedge-shaped shape in which the thickness of the meridional cross section increases from the central axis 1 toward the periphery.

Then, in this embodiment, the object surface 6 is set to infinity in the -Z axis direction.

The rear group 4 consists of a junction lens of a plano-concave negative lens L1 and a biconvex positive lens L2, and a junction lens of a biconvex positive lens L3 and a concave flat negative lens L4. Is located in. The image plane 7 of this optical system coincides with the back surface of the parallel flat plate 9. In this embodiment, the parallel flat plate 9 may be omitted.

With such a configuration, an image of an object with a wide angle of view of 65 ° at infinity can be combined with a transmission optical element 2 that is rotationally symmetric around the central axis 1, an aperture 5 and a lens system of the rear group 4. Then, an image is formed in a ring band shape on a planar image plane 7 perpendicular to the central axis 1.

The specifications of Example 3 are an angle of view range of 65 ° (center angle of view of 32.5 °), an entrance pupil diameter of 0.16 mm, and an image size of φ0.20 to φ0.91 mm.

FIG. 11 shows the lateral aberration of the optical system of this embodiment. In this transverse aberration diagram, the angle shown in the center indicates the angle of view measured from the plane orthogonal to the central axis 1, and the lateral aberrations in the Y direction (meridional direction) and the X direction (sagittal direction) at that angle of view are shown. Shown. Hereinafter, the same applies to Examples 4 to 7.

Further, FIG. 12 shows the relationship between the angle of view (°) and the image height (mm) in the meridional cross section of this example. In the figure, the linear straight line shows the case where the angle of view and the image height are in a linear relationship. Hereinafter, the same applies to Examples 4 to 7.

In this embodiment, by introducing another optical surface and an optical system in the region near the central axis 1 of the transmission surfaces 21 and 22, an image in one direction of the central axis is also imaged on the image plane 7 and captured. It becomes possible to capture an image with a wider angle of view.

FIG. 13 shows a cross-sectional view taken along the central axis (rotational symmetry axis) 1 of the optical system of the fourth embodiment.

The optical system of this embodiment has two transmissive optical elements 2 made of a transparent medium having a refractive index of more than 1 as the front group 3.₁、2₂It is an optical system that uses. Transmission optical element 2₁1st transparent surface 21₁, 2nd transparent surface 22₁, Transmission optical element 2₂1st transparent surface 21₂, 2nd transparent surface 22₂Is composed of an extended rotation free curved surface obtained by rotating a curve of only spherical terms having no higher-order terms with the central axis 1 as the axis of rotational symmetry, that is, a toric surface having the central axis 1 as the axis of rotational symmetry. .. Transparent surface 21₁、22₁、21₂、22₂All have a shape in which the convex surface faces the object side in the cross section including the central axis 1 at the position where the main ray 10 is incident. In addition, the rear group 4, which is arranged on the image plane 7 side of the front group 3 and is rotationally symmetric around the central axis 1 and has positive power, has a lens configuration of 7 elements in 4 groups. An aperture stop 5 is arranged coaxially with the central axis 1 between the front group 3 and the rear group 4.

And the transparent surface 21 of the front group 3₁、22₁、21₂、22₂Are all transparent surfaces 21 in the vicinity of the intersection with the central axis 1.₁、22₁、21₂、22₂Is shaped so that the normal line of is angled with the central axis 1, and in the cross section including the central axis 1, the transmission optical element 2₁、2₂Has a substantially wedge-shaped shape in which the thickness of the meridional cross section increases from the central axis 1 toward the periphery.

Then, in this embodiment, the object surface 6 is set to infinity in the -Z axis direction.

The rear group 4 includes a junction lens of a biconcave negative lens L1 and a biconvex positive lens L2, a junction lens of a positive meniscus lens L3 with a concave surface facing the object side, and a negative meniscus lens L4 with a concave surface facing the object side. It consists of a biconvex positive lens L5, a negative meniscus lens L6 with a convex surface facing the object side, and a junction lens of a biconvex positive lens L7, and the aperture aperture 5 is arranged immediately before the biconcave negative lens L1. The image plane 7 of this optical system coincides with the back surface of the parallel flat plate 9. In this embodiment, the parallel flat plate 9 may be omitted.

With this configuration, an image of an object with a wide angle of view of 90 ° at infinity passes through a front group 3, an aperture 5, and a rear group 4, which are rotationally symmetric around the central axis 1, and then the central axis. A ring-shaped image is formed on the planar image plane 7 perpendicular to 1.

The specifications of Example 4 are an angle of view range of 90 ° (center angle of view of 0 °), an entrance pupil diameter of 0.131 mm, and an image size of φ0.204 to φ1.989 mm.

FIG. 14 shows the lateral aberration of the optical system of this embodiment.

Further, FIG. 15 shows the relationship between the angle of view (°) and the image height (mm) in the meridional cross section of this example.

In this embodiment, the transmissive optical element 2 on the object side₁By arranging a light-shielding member 26 that blocks light rays from the vicinity of the central axis 1 in the region near the central axis 1, unnecessary light emitted from the vicinity of the central axis 1 enters the optical system to generate flare and the like. Can be prevented.

FIG. 16 shows a cross-sectional view taken along the central axis (rotational symmetry axis) 1 of the optical system of Example 5.

The optical system of this embodiment has two transmissive optical elements 2 made of a transparent medium having a refractive index of more than 1 as the front group 3.₁、2₂It is an optical system that uses. Transmission optical element 2₁1st transparent surface 21₁, 2nd transparent surface 22₁, Transmission optical element 2₂1st transparent surface 21₂, 2nd transparent surface 22₂Is composed of an extended rotation free curved surface obtained by rotating a curve of only spherical terms having no higher-order terms with the central axis 1 as the axis of rotational symmetry, that is, a toric surface having the central axis 1 as the axis of rotational symmetry. .. Transparent surface 21₁、22₁、21₂、22₂All have a shape in which the convex surface faces the object side in the cross section including the central axis 1 at the position where the main ray 10 is incident. In addition, the rear group 4, which is arranged on the image plane 7 side of the front group 3 and is rotationally symmetric around the central axis 1 and has positive power, has a lens configuration of 9 elements in 6 groups. Then, the aperture diaphragm 5 is arranged coaxially with the central axis 1 inside the rear group 4.

And the transparent surface 21 of the front group 3₁、22₁、21₂、22₂Are all transparent surfaces 21 in the vicinity of the intersection with the central axis 1.₁、22₁、21₂、22₂Is shaped so that the normal line of is angled with the central axis 1, and in the cross section including the central axis 1, the transmission optical element 2₁、2₂Has a substantially wedge-shaped shape in which the thickness of the meridional cross section increases from the central axis 1 toward the periphery.

Then, in this embodiment, the object surface 6 is set to infinity in the -Z axis direction.

The rear group 4 includes a negative meniscus lens L1 with a convex surface facing the object side, an aperture aperture 5, a junction lens of a biconcave negative lens L2 and a biconvex positive lens L3, and a positive meniscus lens L4 with a concave surface facing the object side. It consists of a junction lens with a negative meniscus lens L5 with a concave surface facing the object side, a biconvex positive lens L6, a junction lens between a biconvex positive lens L7 and a biconvex negative lens L8, and a biconvex positive lens L9. .. The image plane 7 of this optical system coincides with the back surface of the parallel flat plate 9. In this embodiment, the parallel flat plate 9 may be omitted.

With this configuration, an image of an object with a wide angle of view of 90 ° at infinity passes through a front group 3 and a rear group 4 that are rotationally symmetric around the central axis 1 and is perpendicular to the central axis 1. A ring-shaped image is formed on the flat image plane 7.

The specifications of Example 5 are an angle of view range of 90 ° (center angle of view of 0 °), an entrance pupil diameter of 0.080 mm, and an image size of φ0.241 to φ2.024 mm.

FIG. 17 shows the lateral aberration of the optical system of this embodiment.

Further, FIG. 18 shows the relationship between the angle of view (°) and the image height (mm) in the meridional cross section of this example.

In this embodiment, the transmissive optical element 2 on the object side₁By arranging a light-shielding member 26 that blocks light rays from the vicinity of the central axis 1 in the region near the central axis 1, unnecessary light emitted from the vicinity of the central axis 1 enters the optical system to generate flare and the like. Can be prevented.

FIG. 19 shows a cross-sectional view taken along the central axis (rotational symmetry axis) 1 of the optical system of the sixth embodiment.

The optical system of this embodiment has two transmissive optical elements 2 made of a transparent medium having a refractive index of more than 1 as the front group 3.₁、2₂It is an optical system that uses. Transmission optical element 2₁1st transparent surface 21₁, 2nd transparent surface 22₁, Transmission optical element 2₂1st transparent surface 21₂, 2nd transparent surface 22₂Each is composed of an extended free-to-rotate curved surface obtained by rotating a curve formed by adding a conical constant and a cubic term of Y to a spherical term with the central axis 1 as the axis of rotational symmetry. Transparent surface 21₁、22₁、21₂、22₂All have a shape in which the convex surface faces the object side in the cross section including the central axis 1 at the position where the main ray 10 is incident. In addition, the rear group 4, which is arranged on the image plane 7 side of the front group 3 and is rotationally symmetric around the central axis 1 and has positive power, has a lens configuration of 10 elements in 6 groups. Then, the aperture diaphragm 5 is arranged coaxially with the central axis 1 inside the rear group 4.

And the transparent surface 21 of the front group 3₁、22₁、21₂、22₂Are all transparent surfaces 21 in the vicinity of the intersection with the central axis 1.₁、22₁、21₂、22₂Is shaped so that the normal line of is angled with the central axis 1, and in the cross section including the central axis 1, the transmission optical element 2₁、2₂Has a substantially wedge-shaped shape in which the thickness of the meridional cross section increases from the central axis 1 toward the periphery.

Then, in this embodiment, the object surface 6 is set to infinity in the -Z axis direction.

The rear group 4 has a negative meniscus lens L1 with a convex surface facing the object side, an aperture aperture 5, a junction lens of a biconcave negative lens L2 and a biconvex positive lens L3, and a biconvex positive lens L4 and a concave surface on the object side. A junction lens with a negative meniscus lens L5, a biconvex positive lens L6, a biconvex positive lens L7, and a negative meniscus lens L8 with a concave surface facing the object side, and a negative lens with a concave surface facing the image side. It consists of a junction lens of a meniscus lens L9 and a positive meniscus lens L10 with a concave surface facing the image side. The image plane 7 of this optical system coincides with the back surface of the parallel flat plate 9. In this embodiment, the parallel flat plate 9 may be omitted.

With this configuration, an image of an object with a wide angle of view of 90 ° at infinity passes through a front group 3 and a rear group 4 that are rotationally symmetric around the central axis 1 and is perpendicular to the central axis 1. A ring-shaped image is formed on the flat image plane 7.

The specifications of Example 6 are an angle of view range of 90 ° (center angle of view of 0 °), an entrance pupil diameter of 0.097 mm, and an image size of φ0.156 to φ2.009 mm.

FIG. 20 shows the lateral aberration of the optical system of this embodiment.

Further, FIG. 21 shows the relationship between the angle of view (°) and the image height (mm) in the meridional cross section of this example.

In this embodiment, the transmissive optical element 2 on the object side₁By arranging a light-shielding member 26 that blocks light rays from the vicinity of the central axis 1 in the region near the central axis 1, unnecessary light emitted from the vicinity of the central axis 1 enters the optical system to generate flare and the like. Can be prevented.

In this embodiment, the transparent surface 21 is an extended rotation free curved surface obtained by rotating a curve obtained by adding a conical constant and a cubic term of Y to a spherical term with the central axis 1 as the axis of rotational symmetry.₁、22₁、21₂、22₂It is used for. In particular, the third-order term of Y is a term that shows an asymmetrical shape in the vertical direction with respect to the central main ray main ray 10, and it is possible to obtain a favorable result in correcting image distortion.

FIG. 22 shows a cross-sectional view taken along the central axis (rotational symmetry axis) 1 of the optical system of the seventh embodiment.

The optical system of this embodiment has two transmissive optical elements 2 made of a transparent medium having a refractive index of more than 1 as the front group 3.₁、2₂It is an optical system that uses. Transmission optical element 2₁1st transparent surface 21₁, 2nd transparent surface 22₁, Transmission optical element 2₂1st transparent surface 21₂, 2nd transparent surface 22₂Is composed of an extended rotation free curved surface obtained by rotating a curve of only spherical terms having no higher-order terms with the central axis 1 as the axis of rotational symmetry, that is, a toric surface having the central axis 1 as the axis of rotational symmetry. .. Transparent surface 21₁、22₁、22₂All have a shape in which the convex surface faces the object side in the cross section including the central axis 1 at the position where the main ray 10 is incident. Also, the transparent surface 21₂It has a shape with a concave surface facing the object side in the cross section including the central axis 1 at the position where the main ray 10 is incident. In addition, the rear group 4, which is arranged on the image plane 7 side of the front group 3 and is rotationally symmetric around the central axis 1 and has positive power, has a lens configuration of 9 elements in 6 groups. Then, the aperture diaphragm 5 is arranged coaxially with the central axis 1 inside the rear group 4.

And the transparent surface 21 of the front group 3₁、22₁、21₂、22₂Are all transparent surfaces 21 in the vicinity of the intersection with the central axis 1.₁、22₁、21₂、22₂Is shaped so that the normal line of is angled with the central axis 1, and in the cross section including the central axis 1, the transmission optical element 2₁、2₂Has a substantially wedge-shaped shape in which the thickness of the meridional cross section increases from the central axis 1 toward the periphery.

Then, in this embodiment, the object surface 6 is set to infinity in the -Z axis direction.

The rear group 4 has a negative meniscus lens L1 with a convex surface facing the object side, an aperture aperture 5, a junction lens of a biconcave negative lens L2 and a biconvex positive lens L3, and a biconvex positive lens L4 and a concave surface on the object side. A junction lens with a negative meniscus lens L5, a biconvex positive lens L6, a junction lens between a biconvex positive lens L7 and a negative meniscus lens L8 with a concave surface facing the object side, and a curve with only a double-sided cospherical term. It consists of an extended free-rotating curved surface obtained by rotating the central axis 1 as the axis of rotational symmetry, that is, a positive power lens L9 composed of a toric surface having the central axis 1 as the axis of rotational symmetry. The image plane 7 of this optical system coincides with the back surface of the parallel flat plate 9. In this embodiment, the parallel flat plate 9 may be omitted.

With this configuration, an image of an object with a wide angle of view of 90 ° at infinity passes through a front group 3 and a rear group 4 that are rotationally symmetric around the central axis 1 and is perpendicular to the central axis 1. A ring-shaped image is formed on the flat image plane 7.

The specifications of Example 7 are an angle of view range of 90 ° (center angle of view of 0 °), an entrance pupil diameter of 0.083 mm, and an image size of φ0.293 to φ2.041 mm.

FIG. 23 shows the lateral aberration of the optical system of this embodiment.

Further, FIG. 24 shows the relationship between the angle of view (°) and the image height (mm) in the meridional cross section of this example.

In this embodiment, the transmissive optical element 2 on the object side₁By arranging a light-shielding member 26 that blocks light rays from the vicinity of the central axis 1 in the region near the central axis 1, unnecessary light emitted from the vicinity of the central axis 1 enters the optical system to generate flare and the like. Can be prevented.

In this embodiment, the extended free-form surface of rotation is also arranged in the rear group 4, and astigmatism can be corrected in particular.

The object points in Examples 3 to 7 above are at infinity, but it goes without saying that an image can be taken for a closer object point by shifting the position of the image plane 7 in one direction of the central axis.

The configuration parameters of Examples 1 to 7 are shown below. In the table below, "ERFS" indicates an extended free-form surface.

Example 1 Plane number Curvature radius Face spacing Eccentricity Refractive index Abbe number Object surface ERFS [1] Eccentricity (1) 1 ERFS [1] Eccentricity (1) 1.5163 64.1 2 ERFS [2] Eccentricity (2) 3 ERFS [3] Eccentricity (3) 1.5163 64.1 4 ERFS [4] Eccentricity (4) 5 (Aperture) 0.03 Eccentricity (5) 5 0.90 1.7880 47.3 6 -1.00 0.10 7 1.70 0.62 1.7880 47.3 8 0.35 9 0.40 1.5163 64.1 9 0.00 Image plane ERFS [1] RY θ 0.00 R -5.50 ERFS [2] RY θ 0.00 R -4.50 ERFS [3] RY 12.22 θ -64.66 R- 2.01 ERFS [4] RY 5.23 θ -20.06 R -0.70 Eccentricity (1) X 0.00 Y 0.00 Z 0.00 α 0.00 β 0.00 γ 0.00 Eccentricity (2) X 0.00 Y 0.00 Z 0.00 α 0.00 β 0.00 γ 0.00 Eccentricity (3) X 0.00 Y -2.41 Z 0.00 α 0.00 β 0.00 γ 0.00 Eccentricity (4) X 0.00 Y -3.85 Z 0.00 α 0.00 β 0.00 γ 0.00 Eccentricity (5) X 0.00 Y -5.34 Z 0.00 α -90.00 β 0.00 γ 0.00 ..

Example 2 Plane number Curvature radius Face spacing Eccentricity Refractive index Abbe number Object surface ERFS [1] 1 ERFS [1] Eccentricity (1) 1.5163 64.1 2 ERFS [2] Eccentricity (2) 3 ERFS [3] Eccentricity (3) 1.5163 64.1 4 ERFS [4] Eccentricity (4) 5 (Aperture) 0.03 Eccentricity (5) 6 0.90 1.7880 47.3 7 -1.00 0.10 8 1.70 0.62 1.7880 47.3 9 0.29 10 0.40 1.5163 64.1 Image plane ERFS [1] RY θ 0.00 R -5.50 ERFS [2] RY θ 0.00 R -4.50 ERFS [3] RY 5.41 θ -45.79 R -3.17 ERFS [2 ] RY 19.38 θ 0.00 R -1.29 Eccentricity (1) X 0.00 Y 0.00 Z 0.00 α 0.00 β 0.00 γ 0.00 Eccentricity (2) X 0.00 Y 0.00 Z 0.00 α 0.00 β 0.00 γ 0.00 Eccentricity (3) X 0.00 Y -1.13 Z 0.00 α 0.00 β 0.00 γ 0.00 Eccentricity (4) X 0.00 Y -2.48 Z 0.00 α 0.00 β 0.00 γ 0.00 Eccentricity (5) X 0.00 Y -4.95 Z 0.00 α -90.00 β 0.00 γ 0.00.

Example 3 Plane number Curvature radius Face spacing Eccentricity Refractive index Abbe number Object surface Eccentricity (1) 1 7.91 Eccentricity (2) 1.5163 64.1 2 ERFS [1] Eccentricity (3) 3 (Aperture) 0.03 Eccentricity (4) 4 0.30 1.8052 25.4 5 0.99 0.60 1.4875 70.4 6 -0.69 0.10 7 1.04 0.80 1.7440 44.9 8 -0.84 0.30 1.8052 25.4 9 0.16 10 0.40 1.5163 64.1 11 0.00 Image plane ERFS [1] RY 1.40 θ -20.82 R -0.73 C₄ 9.5407 ×10^-2C₅ -1.6486 ×10^-2 Eccentricity (1) X 0.00 Y 0.00 Z - α 0.00 β 0.00 γ 0.00 Eccentricity (2) X 0.00 Y 0.16 Z 0.00 α -90.00 β 0.00 γ 0.00 Eccentricity (3) X 0.00 Y -1.06 Z 0.00 α 0.00 β 0.00 γ 0.00 Eccentricity (4) X 0.00 Y -3.05 Z 0.00 α -90.00 β 0.00 γ 0.00.

Example 4 Plane number Curvature radius Face spacing Eccentricity Refractive index Abbe number Object surface Eccentricity (1) 1 ERFS [1] Eccentricity (2) 1.8830 40.7 2 ERFS [2] Eccentricity (3) 3 ERFS [3] Eccentricity (4) 1.8830 40.7 4 ERFS [4] Eccentricity (5) 5 (Aperture) 0.030 Eccentricity (6) 6 -2.779 0.200 1.6146 46.4 7 0.819 0.600 1.6234 59.7 8 -0.795 0.151 9 -7.419 0.800 1.6968 49.1 10 -0.802 0.300 1.8467 23.8 11 -3.004 0.050 12 3.700 0.800 1.4970 81.5 13 -3.058 0.050 14 2.429 0.300 1.8467 23.8 15 1.200 1.000 1.6414 56.5 16 -14.857 0.321 17 0.400 1.5163 64.1 18 0.000 Image plane ERFS [1] RY 2.812θ -62.791R -1.758 ERFS [2] RY 1.786θ -28.577R -1.002 ERFS [3] RY 2.136θ -70.230R -0.450 ERFS [4] RY 0.559θ -43.461R -0.302 Eccentricity (1) X 0.000 Y 0.000 Z - α 0.000 β 0.000 γ 0.000 Eccentricity (2) X 0.000 Y 0.000 Z 0.000 α 0.000 β 0.000 γ 0.000 Eccentricity (3) X 0.000 Y -0.524 Z 0.000 α 0.000 β 0.000 γ 0.000 Eccentricity (4) X 0.000 Y -0.991 Z 0.000 α 0.000 β 0.000 γ 0.000 Eccentricity (5) X 0.000 Y -1.200 Z 0.000 α 0.000 β 0.000 γ 0.000 Eccentricity (6) X 0.000 Y -1.858 Z 0.000 α -90.000 β 0.000 γ 0.000.

5 (Aperture) 0.030 Eccentricity (6) 6 -2.779 0.200 1.6146 46.4 7 0.819 0.600 1.6234 59.7 Example 5 Surface number Curvature radius Surface spacing Eccentricity Refractive index Abbe number Object surface Eccentricity (1) 1 ERFS [1] Eccentricity (2) ) 1.8830 40.7 2 ERFS [2] Eccentricity (3) 3 ERFS [3] Eccentricity (4) 1.8830 40.7 4 ERFS [4] Eccentricity (5) 5 5.234 0.103 Eccentricity (6) 1.4880 70.3 6 0.400 0.206 7 (Aperture) 0.100 8 -5.004 0.200 1.6302 47.6 9 1.206 0.600 1.6212 40.8 10 -0.757 0.290 11 -22.554 0.800 1.7050 47.8 12 -0.917 0.300 1.8467 23.8 13 -2.538 0.050 14 12.200 0.600 1.5011 63.1 15 -2.750 0.050 16 2.492 1.000 1.5966 60.8 17 -1.261 0.300 1.8467 23.8 18 1.982 0.267 19 1.838 1.000 1.4877 70.3 20 -2.787 0.100 21 0.400 1.5163 64.1 22 0.000 Image plane ERFS [1] RY 2.948θ -60.333R -1.843 ERFS [2] RY 2.061θ -26.667R -1.041 ERFS [3] RY 1.684θ -71.813R -0.501 ERFS [4] RY 0.432θ -45.199R -0.315 Eccentricity (1) X 0.000 Y 0.000 Z - α 0.000 β 0.000 γ 0.000 Eccentricity (2) X 0.000 Y 0.000 Z 0.000 α 0.000 β 0.000 γ 0.000 Eccentricity (3) X 0.000 Y -0.536 Z 0.000 α 0.000 β 0.000 γ 0.000 Eccentricity (4) X 0.000 Y -0.951 Z 0.000 α 0.000 β 0.000 γ 0.000 Eccentricity (5) X 0.000 Y -1.213 Z 0.000 α 0.000 β 0.000 γ 0.000 Eccentricity (6) X 0.000 Y -1.600 Z 0.000 α -90.000 β 0.000 γ 0.000.

Example 6 Plane number Curvature radius Face spacing Eccentricity Refractive index Abbe number Object surface Eccentricity (1) 1 ERFS [1] Eccentricity (2) 1.8830 40.7 2 ERFS [2] Eccentricity (3) 3 ERFS [3] Eccentricity (4) 1.8830 40.7 4 ERFS [4] Eccentricity (5) 5 2.908 0.200 Eccentricity (6) 1.5163 64.1 6 0.387 0.200 7 (Aperture) 0.100 8 -4.520 0.200 1.6764 31.7 9 1.391 0.600 1.6436 37.5 10 -0.759 0.635 11 8.819 0.800 1.7412 45.0 12 -1.073 0.300 1.8467 23.8 13 -5.075 0.050 14 62.541 0.600 1.4970 81.5 15 -5.306 0.050 16 4.493 1.000 1.6750 51.6 17 -1.426 0.300 1.8467 23.8 18 -10.502 0.103 19 4.823 0.300 1.6014 40.1 20 1.121 1.200 1.6183 60.3 21 426.799 0.130 22 0.400 1.5163 64.1 23 0.000 Image plane ERFS [1] RY 2.889θ -60.517R -2.023C₁ -1.8603 ×10^-2C₄ -2.3444 ×10^-3 ERFS [2] RY 1.581θ -29.554R -1.084C₁ -2.9790 ×10^-1C₄ -7.2760 ×10^-2 ERFS [3] RY 1.565θ -72.421R -0.525C₁ -8.1208 ×10^-1C₄ -1.2750 ×10^-3 ERFS [4] RY 0.490θ -45.951R -0.361C₁ 2.5646 ×10^-2C₄ -2.7849 ×10^-1 Eccentricity (1) X 0.000 Y 0.000 Z - α 0.000 β 0.000 γ 0.000 Eccentricity (2) X 0.000 Y 0.000 Z 0.000 α 0.000 β 0.000 γ 0.000 Eccentricity (3) X 0.000 Y -0.611 Z 0.000 α 0.000 β 0.000 γ 0.000 Eccentricity (4) X 0.000 Y -1.021 Z 0.000 α 0.000 β 0.000 γ 0.000 Eccentricity (5) X 0.000 Y -1.247 Z 0.000 α 0.000 β 0.000 γ 0.000 Eccentricity (6) X 0.000 Y -1.627 Z 0.000 α -90.000 β 0.000 γ 0.000.

Example 4 Plane number Curvature radius Face spacing Eccentricity Refractive index Abbe number Object surface Eccentricity (1) 1 ERFS [1] Eccentricity (2) 1.8830 40.7 2 ERFS [2] Eccentricity (3) 3 ERFS [3] Eccentricity (4) 1.8830 40.7 4 ERFS [4] Eccentricity (5) 5 3.542 0.326 Eccentricity (6) 1.5025 62.2 6 0.368 0.159 7 (Aperture) 0.100 8-1.448 0.200 1.6824 36.7 9 1.657 0.600 1.6709 34.6 10 -0.723 0.655 11 31.831 0.900 1.6758 49.9 12 -1.046 0.300 1.8467 23.8 13 -4.841 0.050 14 32.179 0.800 1.4878 70.2 15 -1.998 0.050 16 3.189 0.900 1.4955 65.7 17 -2.104 0.300 1.8467 23.8 18 -26.406 * 0.676 19 ERFS [5] Eccentricity (7) 1.6426 37.1 20 ERFS [6] Eccentricity (8) 21 0.400 1.5163 64.1 22 0.000 Image plane (*) 18 The surface spacing of 0.676 is the surface spacing of 18 and 21 ERFS [1] RY 3.636θ -61.252R. -1.960 ERFS [2] RY 3.583θ -35.359R -1.305 ERFS [3] RY -8.819θ -43.922R -0.759 ERFS [4] RY 0.929θ -20.488R -0.512 ERFS [5] RY 3.544θ -100.214R 0.737 ERFS [6] RY 1.293θ --89.033R 0.676 Eccentricity (1) X 0.000 Y 0.000 Z - α 0.000 β 0.000 γ 0.000 Eccentricity (2) X 0.000 Y 0.000 Z 0.000 α 0.000 β 0.000 γ 0.000 Eccentricity (3) X 0.000 Y -0.435 Z 0.000 α 0.000 β 0.000 γ 0.000 Eccentricity (4) X 0.000 Y -0.776 Z 0.000 α 0.000 β 0.000 γ 0.000 Eccentricity (5) X 0.000 Y -0.966 Z 0.000 α 0.000 β 0.000 γ 0.000 Eccentricity (6) X 0.000 Y -1.345 Z 0.000 α -90.000 β 0.000 γ 0.000 Eccentricity (7) X 0.000 Y -7.368 Z 0.000 α 0.000 β 0.000 γ 0.000 Eccentricity (8) X 0.000 Y -8.209 Z 0.000 α 0.000 β 0.000 γ 0.000 ..

In Examples 1 and 2 above, surfaces obtained by rotating a curve composed of an arc around the central axis 1 are used for the first transmission surface 21 and the second transmission surface 22 of the transmission optical element 2. Similar to the second transparent surface 22 of Example 3, an extended free-rotating curved surface obtained by rotating an arcuate curve having a higher-order term around the central axis 1 may be used, and further, it may be replaced with an arbitrary curved surface. Is also easy. Similarly, in Examples 4, 5 and 7, the transmission optical element 2₁、2₂A surface obtained by rotating a curve composed of an arc around the central axis 1 was used for each of the two transmission surfaces of the above, and the transmission optical element 2 of Example 6 was used.₁、2₂Similarly, an extended free-form surface for rotation obtained by rotating an arcuate curve having a higher-order term around the central axis 1 may be used, and it is also easy to replace it with an arbitrary curved surface.

Further, in the optical system of the present invention, one Y toric lens (a lens whose lens surface is composed of a toric surface whose central axis 1 is the axis of rotational symmetry) is added to the object side of the front group 3, and this lens is also the central axis. It can be configured with a plane that is rotationally symmetric with respect to 1. This lens is a lens that does not have concentric power in the sagittal direction, and by having a negative power in the meridional cross section, it is possible to take a larger angle of view in the meridional cross section.

More preferably, this lens is composed of a negative meniscus lens having a convex surface facing the object side in the meridional cross section, so that the occurrence of image distortion can be minimized and good aberration correction can be performed.

Further, by arranging not only one meniscus negative lens but also two or three meniscus lenses on the object side of the optical system of the present invention, it is possible to further reduce the occurrence of image distortion.

Further, the transmission optical elements 2 and 2 of the present invention₁、2₂Can be used as it is to capture or project an image with a 360 ° omnidirectional angle of view, but the transmissive optical element 2 is cut along the cross section including the central axis 1 to make one-half or one-third. By setting the magnification to two-thirds, images with an angle of view of 180 °, 120 °, 240 °, etc. around the central axis 1 may be taken or projected.

Hereinafter, an example of using the wide angle-of-view photography optical system 41 will be described as an application example of the optical system of the present invention. FIG. 25 is a diagram for showing an example in which the wide angle-of-view imaging optical system 41 according to the present invention is used as the imaging optical system at the tip of the endoscope, and FIG. 25 (a) is a diagram showing the tip 41 of the rigid endoscope 51. This is an example in which the wide-angle-of-view photography optical system 41 according to the present invention is attached to an image of a wide-angle-of-view image in all directions of 360 °. Figure 25 (b) shows the schematic configuration of the tip. In this example, an optical system in which two optical systems of Example 2 are arranged using the common transmission optical element 20 of FIG. 8 is used, and the entire 360 ° is covered by the cover of the tip 41 of the rigid endoscope 51. A window 25 is provided over the circumference, and an object around the window 25 is imaged by an image pickup element arranged on image planes 7 and 7'. Further, in FIG. 25 (c), the wide angle-of-view imaging optical system 41 according to the present invention is similarly attached to the tip of the flexible electron endoscope 52, and the image captured by the display device 53 is subjected to image processing to distort the image. This is an example of correcting and displaying.

FIG. 26 is a diagram for showing an example in which the wide angle-of-view imaging optical system 41 according to the present invention is used as the imaging optical system of the capsule endoscope 54, and is closely attached to the transparent cylindrical body 8 on the side surface of the capsule endoscope 54. A 360 ° omnidirectional wide-angle image of the intestinal wall or the like is imaged and observed by this wide-angle photography optical system 41. In this example, an optical system in which two optical systems of Example 2 are arranged using the common transmission optical element 20 of FIG. 8 is used, and the transparent cylindrical body 8 is transparent on the side surface of the capsule endoscope 54. It constitutes the cover.

<figref num="1">It is sectional drawing taken along the central axis of the optical system of Example 1 of this invention.</figref><figref num="2">It is a lateral aberration diagram of the optical system of Example 1.</figref><figref num="3">It is a figure which shows the relationship between the object height and the image height in the meridional cross section of Example 1.</figref><figref num="4">It is sectional drawing which shows the modification of the transmission optical element of Example 1. FIG.</figref><figref num="5">It is sectional drawing taken along the central axis of the optical system of Example 2 of this invention.</figref><figref num="6">It is a lateral aberration diagram of the optical system of Example 2.</figref><figref num="7">It is a figure which shows the relationship between the object height and the image height in the meridional cross section of Example 2.</figref><figref num="8">It is sectional drawing of the modification of Example 2. FIG.</figref><figref num="9">It is sectional drawing of another modification of Example 2. FIG.</figref><figref num="10">It is sectional drawing taken along the central axis of the optical system of Example 3 of this invention.</figref><figref num="11">It is a lateral aberration diagram of the optical system of Example 3.</figref><figref num="12">It is a figure which shows the relationship between the angle of view and the image height in the meridional cross section of Example 3.</figref><figref num="13">It is sectional drawing taken along the central axis of the optical system of Example 4 of this invention.</figref><figref num="14">It is a lateral aberration diagram of the optical system of Example 4.</figref><figref num="15">It is a figure which shows the relationship between the angle of view and the image height in the meridional cross section of Example 4.</figref><figref num="16">It is sectional drawing taken along the central axis of the optical system of Example 5 of this invention.</figref><figref num="17">It is a lateral aberration diagram of the optical system of Example 5.</figref><figref num="18">It is a figure which shows the relationship between the angle of view and the image height in the meridional cross section of Example 5.</figref><figref num="19">It is sectional drawing taken along the central axis of the optical system of Example 6 of this invention.</figref><figref num="20">It is a lateral aberration diagram of the optical system of Example 6.</figref><figref num="21">It is a figure which shows the relationship between the angle of view and the image height in the meridional cross section of Example 6.</figref><figref num="22">It is sectional drawing taken along the central axis of the optical system of Example 7 of this invention.</figref><figref num="23">It is a lateral aberration diagram of the optical system of Example 7.</figref><figref num="24">It is a figure which shows the relationship between the angle of view and the image height in the meridional cross section of Example 7.</figref><figref num="25">It is a figure for demonstrating the example which used the wide angle-of-view photography optical system by this invention as the photography optical system of the tip of an endoscope.</figref><figref num="26">It is a figure for demonstrating the example which used the wide angle-of-view photography optical system by this invention as the imaging optical system of a capsule endoscope.</figref>

Code description

1 ... Central axis (rotational symmetry axis) 2, 2', 2₁、2₂... Transmission optical element 3 ... Front group 4, 4'... Rear group 5 ... Aperture aperture 6, 6'... Object surface 7, 7'... Image surface 8 ... Transparent Cylindrical body 9 ... Parallel flat plate 10 ... Main ray 11 ... Outer cylindrical surface 12 ... Inner cylindrical surface 13 ... Hole 20 ... Transmitting optical elements 21, 22, 21₁、22₁、21₂、22₂... Transparent surface 23, 24 ... Parallel surface 25 ... Window 26 ... Shading member 41 ... Wide angle of view optics (tip of rigid endoscope) 51 ... Hard endoscope 52 ... Flexible Electronic Endoscope 53 ... Display 54 ... Capsule Endoscope L1, L2, L3, L4, L5, L6, L7, L8, L9, L10 ... Lens