JP2006276884A - Eccentric prism optical system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an eccentric prism optical system in which the wide effective face of a first face located near the pupil of an eccentric prism and having a transmitting action and a reflecting action is a rotationally symmetric spherical face or a aspherical face. <P>SOLUTION: The eccentric prism 7 has three faces 3, 4, and 5. Each gap between the adjacent faces 3 to 5 is filled with a transparent medium, the refractive index of which is higher than 1. A positive lens 9 is disposed on the incident side of the first face 3. A light flux emitted from an object is passed through the pupil 1 of an optical system 10 along an optical axis 2, then made incident on the first face 3 of the eccentric prism 7 via the positive lens 9, and enters the prism 7. The light flux is reflected by the second face 4 in the direction of approaching the pupil 1, and then reflected again by the first face 3 in the direction of separating from the pupil 1. The reflected light ray is passed through the third face 5, reaches an image face 6, and forms an image. The first face 3 is a rotationally symmetric face such as a spherical face whereas the second face 4 is a rotationally asymmetric face. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a decentered prism optical system, and more particularly to a decentered prism optical system with good manufacturability that can be used in an eyepiece optical system or an imaging optical system.

Conventionally known decentered prism optical systems include those disclosed in Patent Document 1 and Patent Document 2. Further, there are those of Patent Documents 3 and 4 of the present applicant. In these cases, a rotationally asymmetric surface shape is used for a surface having a reflection effect.
JP-A-7-333551 JP-A-8-234137 Japanese Patent Laid-Open No. 8-320452 JP-A-8-313829

  However, in these prior arts, the first surface on the pupil side having transmission and reflection action is configured as a rotationally asymmetric surface, and at the same time, the second surface on the side far from the pupil having only the reflection action is also an anamorphic surface. It consists of a flick surface and a toric surface. For this reason, when measuring whether or not the shape according to the design value is made in manufacturing the optical system, the surface accuracy cannot be measured by a method such as an interferometer because it is rotationally asymmetric, It is necessary to measure with a three-dimensional coordinate measuring instrument. However, since the three-dimensional coordinate measuring instrument measures the coordinates of the points one by one, there are problems that the measurement accuracy is insufficient and that the measurement takes a very long time.

  In addition, it is shown in the above prior art that the third surface having only the transmission action is designed to be rotationally symmetric, but the surface having only this transmission action has a narrow effective area of the surface, and the entire optical system is correct. It is difficult to estimate whether the shape is produced based on only this surface. The first surface having the reflection and transmission functions closer to the pupil has a large effective area, so that it is convenient to use it as a reference when estimating whether there is distortion in the entire optical system. In particular, when plastic injection molding (molding) is performed, it is important to reduce changes in the shape of the entire optical system, and at least one of the effective surface (the light beam is transmitted or reflected in the entire area of the surface). Measuring a surface with a large area) and estimating the shape of the entire optical system is an effective means for mass production.

  The present invention has been made in view of such problems of the prior art, and its purpose is to rotate a surface having a wide effective range of the first surface having transmission and reflection on the side close to the pupil of the eccentric prism. An object of the present invention is to provide a decentered prism optical system composed of a symmetric spherical surface or aspherical surface.

The decentered prism optical system of the present invention that achieves the above object includes a decentered prism having a configuration in which at least three surfaces are arranged decentered from each other, and a space between the three surfaces is filled with a transparent medium having a refractive index of 1.3 or more. In a decentered prism optical system with
The decentered prism forms at least two of the three surfaces with reflective surfaces so as to perform internal reflection at least twice, and is reflected by the two reflective surfaces. The surface having the two reflecting actions is arranged at a position where the light rays do not intersect inside the decentered prism, and one of the two faces having the reflecting action has a shape of both in-plane and out-of-plane. It is formed of a rotationally asymmetric surface that does not have a rotational symmetry axis, and the shape of at least the effective surface of one of the other surfaces (the region where light flux is transmitted and / or reflected in the entire surface area) rotates within the effective surface. It consists of a rotationally symmetric surface with a symmetry axis,
A lens having positive refracting power is disposed on the incident side or the exit side of the decentered prism.

  In this case, the rotationally symmetric surface of the decentered prism is formed as a first surface having both a transmission function for entering or emitting a light beam passing through the decentered prism and a reflection function for bending the light beam inside the decentered prism. A rotationally asymmetric surface is formed as a second surface opposed to the first surface, and a third surface having a transmission function for emitting or entering a light beam passing through the eccentric prism is formed between the first surface and the second surface. The lens is disposed at a position substantially perpendicular to the facing direction, and at least the decentered prism includes a first surface, a second surface, and a third surface, and the lens is disposed on the incident side or the exit side of the first surface. Can be.

  At this time, the first surface of the decentered prism is formed so that the transmission and reflection of the first prism overlap at least in a part of the effective surface, and at least the transmission of the first surface within the effective surface. It can be configured such that the reflection effect in the region overlapping with the reflection effect is due to the total reflection effect.

  Hereinafter, the reason and action of the above configuration in the present invention will be described.

  First, the principle of the decentered prism optical system of the present invention will be described. In order to make the description easier to understand, the optical path diagram in the case where the decentered prism, which is the main part of the optical system of the present invention, is the simplest three-plane prism is illustrated in FIG. Will be described. In the case of FIG. 1, the surface arranged on the optical path of the eccentric prism 7 is composed of three surfaces 3, 4, and 5. In the decentering prism 7, a light beam emitted from an object (not shown) first passes through the pupil 1 of the decentering prism 7 and enters the first surface 3 of the decentering prism 7 having a transmission action and a reflection action. Then, the incident light beam is reflected in a direction approaching the pupil 1 by the second surface 4 which is a reflection surface having only a reflection effect on the side far from the pupil 1, and the transmission effect and reflection arranged closer to the pupil 1. The first surface 3 having the action is reflected again in the direction away from the pupil 1 this time. The reflected light beam is disposed at a position substantially perpendicular to the opposing direction of the first surface 3 and the second surface 4 (Z-axis direction in the figure) (Y-axis direction in the figure) and has only a transmission action. The light passes through the three surfaces 5 and reaches the image surface 6 to form an image. Reference numeral 2 denotes an optical axis.

  Thus, the surface numbers of the decentered prism 7 in the present invention are tracked in the order from the pupil 1 to the image surface 6 in principle.

  However, FIG. 1 is an exemplification, and the decentered prism 7 in the present invention may have four optical surfaces as shown in FIG. 2 or may have more than two reflections. FIG. 2A shows an eccentric prism 7 having four surfaces of the fourth surface 8 in addition to the first surface 3, the second surface 4, and the third surface 5, and the fourth surface 8 having a reflecting action is rotated. Although it may be a symmetric spherical surface or a rotationally symmetric aspherical surface, it is preferably composed of a rotationally asymmetric aspherical surface having only one anamorphic surface or symmetric surface. FIG. 2B shows an example in which the first surface 3 and the third surface 5 are used on the same surface.

  Now, among the at least three surfaces constituting such an eccentric prism, the first surface having the transmitting action and the reflecting action arranged on the pupil side is constituted by a rotationally symmetric face and has only the reflecting action far from the pupil. The second surface is preferably constituted by a rotationally asymmetric surface.

  This is because when the light beam that exits the object center, passes through the pupil center, and reaches the image plane center is the axial chief ray, the axial chief ray of the first surface that has transmission and reflection functions is reflected. This is because the refractive power (power) is weaker than the point at which the axial principal ray is reflected by the second surface having only the reflecting action. Therefore, basically, there is little decentration aberration caused by decentration on the first surface, and even if this surface is constituted by a rotationally symmetric surface, the decentration aberration can be corrected by another surface.

  Further, in the present invention, as shown by the broken line in FIG. 1, the decentering prism 7 has the above-described configuration, and the refractive lens system 9 is added to the object side of the decentering prism 7 so that an optical system with a wide angle of view is obtained. Can be configured. When the refractive lens system 9 is disposed between the object and the pupil 1, an optical system having a negative refractive power is disposed, and the principal ray from the object is reduced in the height of light incident on the eccentric prism 7, thereby decentering. The prism 7 can be reduced in size, and at the same time, an optical system with a wide angle of view can be configured.

  Further, by arranging a refractive lens system 9 having a positive refractive power between the pupil 1 and the decentered prism 7 (in the case shown in FIG. 1), the principal ray that has passed through the pupil 1 is converged and incident on the decentered prism 7. By doing so, it is possible to make the decentered prism 7 small and to construct an optical system with a wide angle of view.

  Further, in the present invention, when the refractive lens system 9 is disposed on the object side of the decentered prism 7, the refractive lens system 9 can also function as a cover glass, and there is no need to provide a separate cover glass. This is important in an optical system using the decentered prism 7 as described above. Since the decentering prism 7 is composed of an eccentric rotationally asymmetric surface and a rotationally symmetric surface, it is usually made of a relatively soft plastic with low hygroscopicity such as polyolefin resin (for example, “ZEONEX” manufactured by Nippon Zeon Co., Ltd.). In order to be manufactured, it is necessary to provide a cover glass especially in front of the incident side surface. Further, since the first surface 3 which is the incident side surface of the decentering prism 7 is often a total reflection surface, a coating cannot be provided on the surface, so a cover glass must be provided in front of the surface. . However, in the decentered prism optical system of the present invention to which the refractive lens system 9 is added, the cover glass can be omitted by making the refractive lens system 9 also function as the cover glass, so that the optical system can be lightened.

  A coordinate system used in the following description will be described.

  As shown in FIG. 1, an axial principal ray that passes through the center of the pupil 1 of the decentered prism optical system 10 and reaches the center of the image plane 6 (or an image display element when used as an eyepiece optical system) exits the pupil 1. Defined by a straight line (matching the optical axis 2 when used as an eyepiece optical system, the observer's visual axis) until it intersects the first surface of the decentered prism optical system 10 (the first surface of the refractive lens system 9). The Z axis is defined as the Z axis, the axis in the decentered plane of each surface constituting the decentered prism optical system 10 is defined as the Y axis, and the axis is orthogonal to the Z axis and orthogonal to the Y axis. Is the X axis. The center of pupil 1 is the origin of this coordinate system. The direction in which the axial principal ray reaches the image plane from the object point is the positive direction of the Z-axis, the direction in which the image plane 6 is positioned is the positive direction of the Y-axis, and the X-axis that constitutes the right-hand system with the Y-axis and Z-axis The direction of the axis is the positive direction of the X axis.

  In general, it is difficult to manufacture the decentered prism by polishing, and the eccentric prism is formed one by one by grinding, or by plastic injection molding or glass molding. At this time, it is necessary to confirm whether or not the surface of the decentered prism is formed in a predetermined shape. When each surface of the eccentric prism is composed of a three-dimensional rotationally asymmetric surface, a three-dimensional coordinate measuring instrument is generally used for measuring such a three-dimensional rotationally asymmetric surface shape. Not realistic.

  In the present invention, it is important that at least one of the at least three surfaces constituting the decentered prism is a rotationally symmetric surface. When configured with a rotationally symmetric surface, it is possible to easily measure the surface shape in a short time with a rotationally symmetric aspherical interferometer as shown in JP-A-8-21712.

  More preferably, a surface having a transmission effect and an internal reflection effect on the side close to the pupil that has the largest effective area and relatively large aberration deterioration is configured as a rotationally symmetric surface, so that the surface shape can be easily shortened. It has succeeded in constructing an eccentric prism that can be evaluated in time.

  Hereinafter, the decentered prism optical system of the present invention will be described as an imaging optical system. Of course, the object point and the image point can be used as an eyepiece optical system by arranging the object point and the image point in reverse (with the image display element on the image plane 6 in FIG. 1 and the pupil of the observer positioned on the pupil 1). Needless to say. Of course, an image display element can be arranged on the pupil 1 side, and an image of the image display element can be observed from the image plane 6 side.

When the X-axis, Y-axis, and Z-axis are determined according to the above definition, the X-ray field angle is zero, the X-direction maximum field angle, and the Y positive direction maximum are among the principal rays that exit from the pupil position center and enter the image plane. The six principal rays (1) to (6) are determined as shown in the following Table-1 by the combination of the angle of view, the Y-direction angle of view zero, and the Y-direction maximum angle of view in the X-direction and Y-direction.
Table-1
┌────────┬───────┬───────┐
│ │Zero angle of view│Maximum field of view in X direction│
├────────┼───────┼───────┤
│Maximum angle of view in Y positive direction│ (1) │ (4) │
├────────┼───────┼───────┤
│Zero angle of view │ (2) │ (5) │
├────────┼───────┼───────┤
│Maximum angle of view in Y direction│ (3) │ (6) │
└────────┴┴───────┴───────┘.

  That is, as described in Table 1 above, the axial principal ray at the center of the screen is (2), the principal ray passing through the zero field angle in the X direction and the maximum field angle in the Y positive direction is (1), Principal ray passing through zero field angle, Y negative maximum direction angle (3), X ray maximum field angle, principal ray passing through Y positive direction maximum field angle (4), X direction maximum field angle, Y direction field angle The principal ray passing through zero is (5), and the principal ray passing through the maximum field angle in the X direction and the maximum field angle in the Y negative direction is (6). An area where these principal rays (1) to (6) intersect with each surface is defined as an effective area, and an expression for defining the shape of each surface in the effective area (an expression expressing the Z axis as the surface axis, or The principal rays (1) to (6) in the direction parallel to the Y axis corresponding to the eccentric direction of the surface of the surface of Z = f (X, Y) assuming that the surface is not decentered are surfaces The in-plane curvature including the normal of the surface at the position corresponding to is Cy1 to Cy6. Further, in-plane curvatures including the normal line of the surface in the X-axis direction orthogonal to the Y-axis are Cx1 to Cx6.

  First, a second surface having only a reflection effect on the entire optical system of the present invention (hereinafter, the first surface, the second surface, etc. mean the first surface, the second surface, etc. of the decentered prism unless otherwise specified). The conditional expression regarding the focal length is shown. Since the second surface having only the reflecting action of the present invention is eccentric, the shape of the surface is a rotationally asymmetric surface shape that does not have a rotationally symmetric axis both in and out of the surface. Since it is meaningless to derive the focal length, the focal length is defined as follows.

  A small amount H (mm) passes from the center of the object in parallel to the axial principal ray passing through the entrance pupil center of the optical system in the X-axis direction from the pupil center, and enters the optical system in parallel to the axial principal ray. A value obtained by dividing the NA of the emitted light (the value of the sin of the angle formed with the axial principal ray) when the light is traced by H is defined as the focal length Fx (mm) in the X direction of the entire optical system. In addition, an outgoing ray NA (sin of the angle formed with the axial principal ray) is obtained when a ray that passes through a point H (mm) in the Y direction from the center of the pupil and enters the optical system in parallel with the axial principal ray is traced. Is defined as the focal length Fy (mm) in the Y direction of the entire optical system.

When Fx / Fy is set to FA using Fx and Fy, 0.7 <FA <1.3 (A-1)
It is important to satisfy the following conditional expression.

  This condition is related to the aspect ratio of the image. When the lower limit of 0.7 is exceeded, the image in the X direction becomes small, and when a square is formed, the image becomes a vertically long image, exceeding the upper limit of 1.3. And it becomes a horizontally long image. Naturally, the value of FA is most preferably 1. However, in order to correct image distortion, it is important to correct in a well-balanced manner within the range of the conditional expression shifted from 1 in relation to the higher order coefficient of the surface.

More preferably,
1.0 <FA <1.1 (A-2)
It is important to satisfy the following conditions.

Next, refractive power (power) Pxn, Pyn in the X direction and Y direction of the surface at a position where the axial principal ray that passes through the center of the object and passes through the center of the pupil hits the second surface having only a reflection action, and the optical system The relationship between the refractive power (power) Px and Py, which is the reciprocal of the focal lengths Fx and Fy in the entire X direction and Y direction, is as follows: Pxn / Px is PxB, and Pyn / Py is PyC.
0.8 <| PxB | <1.3 (B-1)
0.8 <| PyC | <1.3 (C-1)
It is preferable to satisfy either of the following conditions.

  If the lower limit of 0.8 of these conditions is exceeded, the power of the second reflecting surface that has only a reflecting action in both the X and Y directions will be too small compared to the power of the entire optical system, Power is borne, which is not preferable in terms of aberration correction.

  If the upper limit of 1.3 is exceeded, the power of the reflecting surface of the second surface becomes too strong, and it becomes impossible to correct image distortion and curvature of field aberration generated on the second surface in a balanced manner. .

  More preferably, both the conditional expressions (B-1) and (C-1) are satisfied.

More preferably,
0.8 <| PxB | <1.2 (B-2)
0.8 <| PyC | <1.1 (C-2)
It is preferable to satisfy either of the following conditions.

Next, the conditions regarding the surface curvature at the position corresponding to the second surface having only a reflecting action will be described. This condition is necessary to reduce the astigmatism generated on the second surface, and the curvature Cx2 in the X direction including the normal line of the second surface at the position where the axial principal ray strikes and the X direction curvature Cx2 When the ratio Cx2 / Cy2 of the curvature Cy2 is CxyD,
0.8 <CxyD <1.2 (D-1)
It is important to satisfy the following conditions.

  The second surface having only the reflecting action is an eccentric surface, and if this surface is composed of a rotationally symmetric surface, image distortion, astigmatism, coma, etc. are greatly generated, so the aberration is excellent. It is impossible to correct it. For this reason, it is important to configure the second surface having only the reflecting action as a rotationally asymmetric surface. However, if the second surface is configured as a rotationally symmetric surface, the generation of astigmatism generated on this surface increases. It becomes impossible to correct in terms of Therefore, in order to correct these, a second surface having only a reflecting surface is formed by a surface having only one plane of symmetry, and each conditional expression (D-1) is satisfied for the first time. Aberration is corrected well, and it is possible to obtain an image without astigmatism on the axis or to observe an observation image. The lower limit of 0.8 and the upper limit of 1.2 are limits for preventing astigmatism from occurring greatly.

More preferably,
0.95 <CxyD <1.05 (D-2)
It is important to satisfy the following conditions.

Next, when the difference between the upper and lower effective areas of the curvature in the Y direction of the second surface, Cy1−Cy3 divided by Py is CyE,
-0.05 <CyE <0.5 (E-1)
It is important to satisfy the following conditions. This condition is necessary to satisfactorily correct the image distortion in the vertical direction above and below the image plane. If the lower limit of −0.05 is exceeded, the magnification at the bottom of the screen becomes smaller, and the upper limit of 0 is set. If it exceeds .5, the magnification in the Y (vertical) direction on the screen will be smaller than the other parts of the screen, and the image will be distorted. In particular, in the decentered prism optical system in which the first surface having reflection and transmission functions is configured as a rotationally symmetric surface as in the present invention and the manufacturability of the decentering prism is improved, this image distortion is corrected by other surfaces. Therefore, the basic image distortion cannot be corrected unless correction is performed on the third surface having only the transmission effect closest to the image. However, since the third surface having only its transmitting action mainly corrects the curvature of field, if the second surface having only the reflecting action does not satisfy this condition, the field curvature and image distortion of the entire optical system will be reduced. Cannot be corrected at the same time.

More preferably,
0 <CyE <0.3 (E-2)
It is preferable for aberration correction to satisfy the following condition.

More preferably,
0 <CyE <0.15 (E-3)
It is preferable for aberration correction to satisfy the following condition.

Next, when CxF is obtained by dividing the difference Cx1-Cx3 above and below the effective area of the curvature in the X direction of the second surface by Px,
-0.01 <CxF <0.1 (F-1)
It is important to satisfy the following conditions. This condition is also a condition necessary for satisfactorily correcting the image distortion in the left and right directions above and below the image plane. If the lower limit of −0.01 is exceeded, the magnification at the bottom of the screen becomes smaller, and the upper limit of 0. If it exceeds 1, the magnification in the X (left and right) direction on the screen becomes smaller than the other parts of the screen, and the image is distorted into a trapezoid.

More preferably,
-0.01 <CxF <0.05 (F-2)
It is preferable for aberration correction to satisfy the following condition.

More preferably,
-0.001 <CxF <0.03 (F-3)
It is preferable for aberration correction to satisfy the following condition.

  Next, image distortion observed by bending up and down like a bow when a straight line is displayed at the center of the screen will be described. The following conditional expression relates to a bow-like rotationally asymmetric image distortion that curves, for example, when a horizontal line is copied.

As shown in the perspective view of FIG. 18A and the projection onto the YZ plane of FIG. 18B, the rotational asymmetry at the point where the principal ray having the maximum field angle in the X direction intersects the rotationally asymmetric surface A. When the angle between the normal n ′ of the surface and the normal n of the rotationally asymmetric surface at the point where the axial principal ray intersects the rotationally asymmetric surface A is defined as DY,
−0.1 <| DY | <5 (°) (G-1)
It is important to satisfy the following conditions. If the lower limit of −0.1 of the above conditional expression is exceeded, bow-shaped image distortion cannot be corrected. When the upper limit of 5 is exceeded, bow-like image distortion becomes overcorrected, and in either case, the image is distorted like a bow. Furthermore, preferably,
−0.05 <| DY | <1 (°) (G-2)
It is preferable to satisfy the following conditions.

Furthermore, preferably,
0 <| DY | <0.5 (°) (G-3)
It is preferable to satisfy the following conditions.

Next, the focal length of a lens system having a positive refractive power disposed between the pupil and the eccentric prism will be described. The following conditional expression is necessary for converging a wide-angle light beam incident by the lens system having a positive refractive power and to make the decentered prism compact. When the focal length of the lens system disposed between the pupil and the decentered prism is F, and the focal length in the Y direction of the entire optical system of the decentered prism and the lens system having positive refractive power is Fy,
1.1 <F / Fy <10000 (H-1)
It is important to satisfy the following conditions. When the lower limit of 1.1 of the above conditional expression is exceeded, the refractive power borne by the lens system becomes too large compared to the refractive power borne by the decentered prism, and is disposed between the pupil which is a refractive optical system and the decentered prism. Aberrations generated in the lens system, particularly field curvature, coma aberration, and chromatic aberration, are so large that a good result as aberration performance cannot be obtained. If the upper limit of 10,000 is exceeded, the focal length of the refractive lens system becomes too long, the light beam converging action of the refractive lens system becomes weak, the decentered prism becomes large, and the angle of view cannot be increased. End up.

Furthermore, preferably,
1.5 <F / Fy <10000 (H-2)
It is preferable to satisfy the following conditions.

Furthermore, preferably,
2 <F / Fy <10000 (H-3)
It is preferable to satisfy the following conditions.

More preferably,
2 <F / Fy <3 (H-4)
In this case, since the chromatic aberration of magnification generated in the refractive lens system becomes large, it is preferable to use it together with the correcting means for chromatic aberration of magnification.

  With regard to the above conditions (A-1) to (G-3), the first surface having the reflecting action and the transmitting action of the eccentric prism is constituted by a rotationally symmetric surface, and the second face having only the reflecting action is defined as the second surface. It is preferable that both the in-plane and out-of-plane surfaces are configured by plane-symmetric free-form surfaces having no rotational symmetry axis and having only one symmetry plane. Furthermore, not only in a plane-symmetry free-form surface, but also in an anamorphic surface that does not have a rotationally symmetric axis both in and out of the plane, that is, rotation that does not have a rotationally symmetric axis both in and out of the plane. The present invention can be applied to any asymmetric surface shape.

  By the way, the eccentric prism may be made of glass, but when used as an image display device mounted on the head or face, it is desirable to make it from plastic from the viewpoint of weight reduction.

  In addition, since this decentered prism is formed with a curved surface (non-planar surface) having a power on the internal reflection surface, rotationally asymmetric aberration occurs. The decentered prism optical system of the present invention corrects this aberration satisfactorily by devising the surface shape having the reflecting action of the decentered prism. However, if the refractive index of the medium changes due to the influence of changes in humidity, the aberration performance deteriorates.

Therefore, it is desirable to use a material having a small coefficient of water-absorption linear expansion (polyolefin resin: for example, “ZEONEX” manufactured by Nippon Zeon Co., Ltd.) as a material for the eccentric prism. Specifically, the water absorption rate α of the material is
0 <α <0.1 (%) (I-1)
It is desirable to satisfy. If the upper and lower limits of this conditional expression are exceeded, the aberration performance is deteriorated, which is not desirable.

  Further, such a material having a small coefficient of water absorption linear expansion is soft and easily damaged as compared with glass or the like. For this reason, for example, when used as an image display device mounted on the head or face, when the first surface of the decentered prism on the viewer's eyeball side is in contact with the outside world, it is necessary to cover the surface. However, it is desirable to use this first surface as a total reflection surface due to the characteristics of the decentered prism optical system of the present invention in order to prevent a decrease in the amount of light. However, when this first surface is coated, this total reflection action is achieved. It will collapse. Therefore, it is desirable to arrange a cover glass between the first surface and the observer's eyeball. In the present invention, the positive lens satisfies this need. In addition to the function of expanding the angle of view, the positive lens also functions as the cover glass described above, reducing the number of parts and reducing the weight. It has also helped.

  As is clear from the above description, according to the present invention, in the imaging optical system or the ocular optical system including the decentered prism capable of obtaining a clear image with a small distortion even at a wide angle of view, one effective of the decentered prism is effective. By constructing a surface having a wide area by a rotationally symmetric surface, it is possible to provide a decentered prism optical system that can be easily evaluated during manufacture.

  Examples 1 to 6 of the decentered prism optical system according to the present invention will be described below. In the configuration parameters of each embodiment described later, as shown in FIG. 1, the center of the pupil 1 of the decentered optical system 10 is the origin of the optical system, and the optical axis 2 passes from the object center to the center (origin) of the pupil 1. The direction in which the light beam is defined from the pupil 1 to the optical axis 2 is defined as the Z-axis direction, the direction perpendicular to the Z-axis and passing through the center of the pupil 1 and the light beam is bent by the optical system 10 is defined as the Y-axis direction. The direction perpendicular to the Z-axis and passing through the center of the pupil 1 is the X-axis direction, the direction from the pupil 1 toward the optical system 10 is the positive direction of the Z-axis, and the optical axis 2 to the image plane 6 side is the positive direction of the Y-axis. The direction constituting the Y-axis, Z-axis and the right-handed system is the positive direction of the X-axis. The ray tracing is performed in a direction in which the light enters the optical system 10 from the object side on the pupil 1 side of the optical system 10.

  For the surface to which the eccentricity is given, the amount of eccentricity in the X-axis direction, the Y-axis direction, and the Z-axis direction from the center of the pupil 1 that is the origin of the optical system 10 at the surface top position of the surface (x, y, z) and the tilt angle (α, β, γ, respectively) about the X axis, Y axis, and Z axis of the center axis of the surface (for the free-form surface, the Z axis in the following equation (a)) ) And are given. In this case, positive α and β means 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. In addition, the radius of curvature of the spherical surface, the surface interval, the refractive index of the medium, and the Abbe number are given in accordance with conventional methods.

  The shape of the rotationally asymmetric surface is defined by the following equation. The Z axis of the defining formula is the axis of the rotationally asymmetric surface.

Z = Σ _n Σ _m C _nm X ⁿ Y ^nm
However, Σ _n represents _n of Σ from 0 to k, and Σ _m represents _m of Σ from 0 to n.

  When a plane-symmetric free-form surface (a rotationally asymmetric surface having only one symmetric surface) is defined by an expression representing this rotationally asymmetric surface, the symmetry of X is obtained when the symmetry generated by the symmetric surface is obtained in the X direction. When the odd-order term is set to 0 (for example, the coefficient of the X-odd-order term is set to 0) and the symmetry caused by the symmetry plane is obtained in the Y direction, the odd-order term of Y is set to 0 (for example, the coefficient of the Y-odd-order term is set to 0). Do it).

  Here, as an example, when a plane-symmetric free-form surface symmetric in the X direction with k = 7 (seventh-order term) is expressed in a form in which the above definition is expanded, the following expression is obtained.

Z = C ₂
+ C ₃ Y + C ₄ X
+ C ₅ Y ² + C ₆ YX + C ₇ X ²
+ C ₈ Y ³ + C ₉ Y ² X + C ₁₀ YX ² + C ₁₁ X ³
+ C ₁₂ Y ⁴ + C ₁₃ Y ³ X + C ₁₄ Y ² X ² + C ₁₅ YX ³ + C ₁₆ X ⁴
+ C ₁₇ Y ⁵ + C ₁₈ Y ⁴ X + C ₁₉ Y ³ X ² + C ₂₀ Y ² X ³ + C ₂₁ YX ⁴
+ C ₂₂ X ⁵
+ C ₂₃ Y ⁶ + C ₂₄ Y ⁵ X + C ₂₅ Y ⁴ X ² + C ₂₆ Y ³ X ³ + C ₂₇ Y ² X ⁴
+ C ₂₈ YX ⁵ + C ₂₉ X ⁶
+ C ₃₀ Y ⁷ + C ₃₁ Y ⁶ X + C ₃₂ Y ⁵ X ² + C ₃₃ Y ⁴ X ³ + C ₃₄ Y ³ X ⁴
+ C ₃₅ Y ² X ⁵ + C ₃₆ YX ⁶ + C ₃₇ X ⁷
... (a)
The coefficients C ₄ , C ₆ , C ₉ ... Of the X odd-order terms are set to 0 (examples described later). It should be noted that in the parameters of the configuration described later, a coefficient relating to an aspheric surface not described is 0.

  Another defining formula for a plane-symmetric free-form surface is a Zernike polynomial. The shape of this surface is defined by the following formula (b). The Z axis of the defining formula becomes the axis of the Zernike polynomial.

X = R × cos (A)
Y = R × sin (A)
Z = D ₂
+ D ₃ Rcos (A) + D ₄ Rsin (A)
+ D ₅ R ² cos (2A) + D ₆ (R ² −1) + D ₇ R ² sin (2A)
+ D ₈ R ³ cos (3A) + D ₉ (3R ³ −2R) cos (A)
+ D ₁₀ (3R ³ -2R) sin (A) + D ₁₁ R ³ sin (3A)
^{_{+ D 12 R 4 cos (4A}} ) + D 13 (4R 4 -3R 2) cos (2A)
+ D ₁₄ (6R ⁴ -6R ² +1) + D ₁₅ (4R ⁴ -3R ² ) sin (2A)
+ D ₁₆ R ⁴ sin (4A) + D ₁₇ R ⁵ cos (5A)
+ D ₁₈ (5R ⁵ -4R ³ ) cos (3A)
+ D ₁₉ (10R ⁵ -12R ³ + 3R) cos (A)
+ D ₂₀ (10R ⁵ -12R ³ + 3R) sin (A)
^{_{+ D 21 (5R 5 -4R 3}} ) sin (3A) + D 22 R 5 sin (5A)
^{_{+ D 23 R 6 cos (6A}} ) + D 24 (6R 6 -5R 4) cos (4A)
+ D ₂₅ (15R ⁶ -20R ⁴ + 6R ² ) cos (2A)
+ D ₂₆ (20R ⁶ -30R ⁴ + 12R ² -1)
+ D ₂₇ (15R ⁶ -20R ⁴ + 6R ² ) sin (2A)
+ D ₂₈ (6R ⁶ -5R ⁴ ) sin (4A) + D ₂₉ R ⁶ sin (6A)
... (b)
In addition, in the above, it represented as a plane symmetrical to the X direction. However, _Dm (m is an integer greater than or equal to 2) is a coefficient.

As an expression example of other surfaces usable in the present invention, the above definition formula (Z = Σ _n Σ _m C _nm X ⁿ Y ^nm ) is a plane symmetrical to the X direction as in the formula (a), and k = In the case of representing the surface 7, it can be expanded as shown in the following equation (c).

Z = C ₂
+ C ₃ Y + C ₄ | X |
+ C ₅ Y ² + C ₆ Y | X | + C ₇ X ²
+ C ₈ Y ³ + C ₉ Y ² | X | + C ₁₀ YX ² + C ₁₁ | X ³ |
+ C ₁₂ Y ⁴ + C ₁₃ Y ³ | X | + C ₁₄ Y ² X ² + C ₁₅ Y | X ³ | + C ₁₆ X ⁴
+ C ₁₇ Y ⁵ + C ₁₈ Y ⁴ | X | + C ₁₉ Y ³ X ² + C ₂₀ Y ² | X ³ |
+ C ₂₁ YX ⁴ + C ₂₂ | X ⁵ |
+ C ₂₃ Y ⁶ + C ₂₄ Y ⁵ | X | + C ₂₅ Y ⁴ X ² + C ₂₆ Y ³ | X ³ |
+ C ₂₇ Y ² X ⁴ + C ₂₈ Y | X ⁵ | + C ₂₉ X ⁶
+ C ₃₀ Y ⁷ + C ₃₁ Y ⁶ | X | + C ₃₂ Y ⁵ X ² + C ₃₃ Y ⁴ | X ³ |
+ C ₃₄ Y ³ X ⁴ + C ₃₅ Y ² | X ⁵ | + C ₃₆ YX ⁶ + C ₃₇ | X ⁷ |
... (c)
Furthermore, the shape of the anamorphic surface that can be used in the present invention is defined by the following equation. A straight line passing through the origin of the surface shape and perpendicular to the optical surface is the axis of the anamorphic surface.

Z = (Cx · X ² + Cy · Y ² ) / [1+ {1- (1 + Kx) Cx ² · X ²
− (1 + Ky) Cy ² · Y ² } ^1/2 ]
+ ΣRn {(1-Pn) X ² + (1 + Pn) Y ² } ^{(n + 1)}
Here, when n = 4 (fourth order term) is considered as an example, it can be expressed by the following equation (d) when expanded.

Z = (Cx · X ² + Cy · Y ² ) / [1+ {1- (1 + Kx) Cx ² · X ²
− (1 + Ky) Cy ² · Y ² } ^1/2 ]
+ R1 {(1-P1) X ² + (1 + P1) Y ² } ²
+ R2 {(1-P2) X ² + (1 + P2) Y ² } ³
+ R3 {(1-P3) X ² + (1 + P3) Y ² } ⁴
+ R4 {(1-P4) X ² + (1 + P4) Y ² } ⁵
... (d)
Where Z is the amount of deviation from the tangential plane with respect to the origin of the surface shape, Cx is the X-axis direction curvature, Cy is the Y-axis direction curvature, Kx is the X-axis direction cone coefficient, Ky is the Y-axis direction cone coefficient, and Rn is an aspheric surface The term rotationally symmetric component, Pn, is an aspheric term rotationally asymmetric component. In addition, between the X-axis direction radius of curvature Rx, the Y-axis direction radius of curvature Ry and the curvatures Cx, Cy,
Rx = 1 / Cx, Ry = 1 / Cy
Are in a relationship.

  The shape of the rotationally symmetric aspheric surface is defined by the following equation. The Z axis of the defining formula is the axis of a rotationally symmetric aspherical surface.

Z = (Y ² / R) / [1+ {1-P (Y ² / R ² )} ^1/2 ]
+ A ₄ Y ⁴ + A ₆ Y ⁶ + A ₈ Y ⁸ + A ₁₀ Y ^10.
... (e)
However, Y is a direction perpendicular to Z, R is a paraxial radius of curvature, P is a conical coefficient, and A ₄ , A ₆ , A ₈ , and A ₁₀ are aspherical coefficients.

  In the configuration parameters described later, the term relating to the aspheric surface for which no data is described is zero. The refractive index is shown for the d-line (wavelength 587.56 nm). The unit of length is mm.

  Next, FIGS. 3 to 8 show YZ sectional views including the optical axis 2 of the decentered prism optical system 10 of Examples 1 to 6, respectively. Similarly to the case of FIG. 1, the decentering prism 7 of any of the embodiments includes three surfaces 3, 4, and 5, and a space between the three surfaces 3 to 5 is a transparent medium having a refractive index greater than 1. A bundle of light rays emitted from an object (not shown) first passes through the pupil 1 of the optical system 10 along the optical axis 2 and has a transmission function and a reflection function through the positive single lens 9 ′. The light enters the surface 3 and enters the decentered prism 7, and the incident light beam is reflected in a direction approaching the pupil 1 by the second surface 4, which is a reflective surface only having a reflection action far from the pupil 1, and this time, the first surface. 3 is reflected again in the direction away from the pupil 1, and the reflected light passes through the third surface 5 having only a transmission action and reaches the image surface 6 to form an image. In all of the embodiments, the positive single lens 9 ′ is a decentered plano-convex lens, and the decentering prism 7 has the decentered prism 7 facing the pupil 1 side in the first to second and fourth to sixth embodiments. In the third embodiment, the first surface 3 is a rotationally symmetric aspherical surface defined by the above-described equation (e) that is decentered with the concave surface facing the pupil 1 side. -5, the second surface 4 and the third surface 5 are free-form surfaces defined by the equation (a), and in Example 6, the second surface 4 is defined by the equation (a). The third surface is a spherical surface.

  In Example 1, the horizontal field angle is 38 °, the vertical field angle is 29.0 °, the image size is 14.4 × 10.7 mm, and the pupil diameter is 4 mm.

  In Examples 2 to 4, the horizontal field angle is 40 °, the vertical field angle is 30.5 °, the image size is 14.4 × 10.7 mm, and the pupil diameter is 4 mm.

  In Examples 5 to 6, the horizontal field angle is 48 °, the vertical field angle is 36.9 °, the image size is 21.1 × 15.8 mm, and the pupil diameter is 4 mm.

All the decentering prisms 7 of Examples 1 to 6 use “ZEONEX” manufactured by Nippon Zeon Co., Ltd. having a refractive index (n _d ) of 1.5254. The water absorption α of this “ZEONEX” is 0.01%.

The configuration parameters of Examples 1 to 6 are shown below.
Example 1
Surface number Curvature radius Interval Eccentric Refractive index Abbe number Object surface ∞ ∞
1 ∞
2 ∞ Eccentricity (1) 1.4922 57.5
3 -35.963 Eccentricity (2)
4 -196.457 Eccentricity (3) 1.5254 56.2
5 Free-form surface [1] Eccentricity (4) 1.5254 56.2
6 -196.457 Eccentricity (3) 1.5254 56.2
7 Free-form surface [2] Eccentricity (5)
Image plane ∞ Eccentricity (6)
Free curved surface [1]
C ₅ -7.2660 × 10 ^-3 C ₇ -7.4223 × 10 ^-3 C ₈ 3.3356 × 10 ^-5
C ₁₀ 1.2235 × 10 ^-5 C ₁₂ -3.9327 × 10 ^-7 C ₁₄ -1.2063 × 10 ^-6
C ₁₆ -7.1374 × 10 ^-7 C ₁₇ 1.3838 × 10 ^-7 C ₁₉ -2.1827 × 10 ^-8
C ₂₁ 2.9995 × 10 ^-8 C ₂₃ 9.7004 × 10 ^-10 C ₂₅ -1.7016 × 10 ^-9
C ₂₇ 2.5056 × 10 ^-9 C ₂₉ 2.1061 × 10 ^-10 C ₃₀ -4.1940 × 10 ^-10
C ₃₂ -2.1214 × 10 ^-10 C ₃₄ 8.2993 × 10 ^-10 C ₃₆ -3.3050 × 10 ^-10
Free curved surface [2]
C ₅ -1.2614 × 10 ^-2 C ₇ -6.8925 × 10 ^-4
Eccentricity (1)
x 0.000 y 0.000 z 23.000
α 8.00 β 0.00 γ 0.00
Eccentricity (2)
x 0.000 y 0.000 z 25.174
α 8.00 β 0.00 γ 0.00
Eccentricity (3)
x 0.000 y 6.745 z 24.085
α 17.36 β 0.00 γ 0.00
Eccentricity (4)
x 0.000 y 0.840 z 34.028
α -12.70 β 0.00 γ 0.00
Eccentricity (5)
x 0.000 y 16.738 z 28.656
α 75.93 β 0.00 γ 0.00
Eccentricity (6)
x 0.000 y 20.545 z 30.873
α 60.19 β 0.00 γ 0.00.

Example 2
Surface number Curvature radius Interval Eccentric Refractive index Abbe number Object surface ∞ ∞
1 ∞
2 ∞ Eccentricity (1) 1.4922 57.5
3 -27.659 Eccentricity (2)
4 -149.496 Eccentricity (3) 1.5254 56.2
5 Free-form surface [1] Eccentricity (4) 1.5254 56.2
6 -149.496 Eccentricity (3) 1.5254 56.2
7 Free-form surface [2] Eccentricity (5)
Image plane ∞ Eccentricity (6)
Free curved surface [1]
C ₅ -7.9104 × 10 ^-3 C ₇ -7.9974 × 10 ^-3 C ₈ 3.9130 × 10 ^-5
C ₁₀ 3.6289 × 10 ^-6 C ₁₂ -1.0272 × 10 ^-6 C ₁₄ -1.8685 × 10 ^-6
C ₁₆ -7.4081 × 10 ^-7 C ₁₇ 8.8993 × 10 ^-8 C ₁₉ -3.7196 × 10 ^-8
C ₂₁ 9.0376 × 10 ^-8 C ₂₃ 5.8432 × 10 ^-10 C ₂₅ -3.6056 × 10 ^-9
C ₂₇ 3.7493 × 10 ^-9 C ₂₉ -2.0178 × 10 ^-11 C ₃₀ -9.0053 × 10 ^-11
C ₃₂ -3.1608 × 10 ^-10 C ₃₄ 1.0947 × 10 ^-9 C ₃₆ -7.0993 × 10 ^-10
Free curved surface [2]
C ₅ -1.2946 × 10 ^-2 C ₇ 8.9577 × 10 ^-3
Eccentricity (1)
x 0.000 y 0.000 z 23.000
α 8.00 β 0.00 γ 0.00
Eccentricity (2)
x 0.000 y 0.000 z 25.544
α 8.00 β 0.00 γ 0.00
Eccentricity (3)
x 0.000 y 6.523 z 24.321
α 16.51 β 0.00 γ 0.00
Eccentricity (4)
x 0.000 y 0.714 z 33.213
α -14.19 β 0.00 γ 0.00
Eccentricity (5)
x 0.000 y 15.307 z 28.201
α 71.70 β 0.00 γ 0.00
Eccentricity (6)
x 0.000 y 18.987 z 30.056
α 62.17 β 0.00 γ 0.00.

Example 3
Surface number Curvature radius Interval Eccentric Refractive index Abbe number Object surface ∞ ∞
1 ∞
2 ∞ Eccentricity (1) 1.4922 57.5
3 -23.410 Eccentricity (2)
4 -143.048 Eccentricity (3) 1.5254 56.2
P 1
A ₄ -0.678231 × 10 ^-5
A ₆ -0.718263 × 10 ^-8
5 Free-form surface [1] Eccentricity (4) 1.5254 56.2
6 -143.048 Eccentricity (3) 1.5254 56.2
P 1
A ₄ -0.678231 × 10 ^-5
A ₆ -0.718263 × 10 ^-8
7 Free-form surface [2] Eccentricity (5)
Image plane ∞ Eccentricity (6)
Free curved surface [1]
C ₅ -7.6312 × 10 ^-3 C ₇ -7.7867 × 10 ^-3 C ₈ 6.8800 × 10 ^-5
C ₁₀ 4.9872 × 10 ^-5 C ₁₂ -3.5180 × 10 ^-6 C ₁₄ -6.5043 × 10 ^-6
C ₁₆ -2.2855 × 10 ^-6 C ₁₇ 2.8747 × 10 ^-7 C ₁₉ 2.2971 × 10 ^-7
C ₂₁ 1.4477 × 10 ^-7 C ₂₃ -1.3241 × 10 ^-9 C ₂₅ -1.3282 × 10 ^-8
C ₂₇ 2.8300 × 10 ^-9 C ₂₉ 2.0011 × 10 ^-10 C ₃₀ 1.8023 × 10 ^-10
C ₃₂ -4.8811 × 10 ^-10 C ₃₄ 1.3959 × 10 ^-9 C ₃₆ -5.2773 × 10 ^-10
Free curved surface [2]
C ₅ -3.0658 × 10 ^-2 C ₇ 2.3240 × 10 ^-3
Eccentricity (1)
x 0.000 y 0.000 z 23.000
α 8.00 β 0.00 γ 0.00
Eccentricity (2)
x 0.000 y 0.000 z 25.977
α 8.00 β 0.00 γ 0.00
Eccentricity (3)
x 0.000 y 7.704 z 25.746
α 7.07 β 0.00 γ 0.00
Eccentricity (4)
x 0.000 y 0.278 z 34.466
α -19.70 β 0.00 γ 0.00
Eccentricity (5)
x 0.000 y 15.617 z 31.379
α 58.30 β 0.00 γ 0.00
Eccentricity (6)
x 0.000 y 17.934 z 33.152
α 53.38 β 0.00 γ 0.00.

Example 4
Surface number Curvature radius Interval Eccentric Refractive index Abbe number Object surface ∞ ∞
1 ∞
2 ∞ Eccentricity (1) 1.4922 57.5
3 -41.999 Eccentricity (2)
4 -138.539 Eccentricity (3) 1.5254 56.2
5 Free-form surface [1] Eccentricity (4) 1.5254 56.2
6 -138.539 Eccentricity (3) 1.5254 56.2
7 Free-form surface [2] Eccentricity (5)
Image plane ∞ Eccentricity (6)
Free curved surface [1]
C ₅ -9.0433 × 10 ^-3 C ₇ -9.2347 × 10 ^-3 C ₈ 5.1854 × 10 ^-5
C ₁₀ 3.3087 × 10 ^-6 C ₁₂ 7.2992 × 10 ^-6 C ₁₄ 1.6139 × 10 ^-5
C ₁₆ 9.6910 × 10 ^-6 C ₁₇ -7.1365 × 10 ^-8 C ₁₉ 1.0603 × 10 ^-7
C ₂₁ 1.7643 × 10 ^-7 C ₂₃ -8.0046 × 10 ^-9 C ₂₅ -3.8685 × 10 ^-8
C ₂₇ -3.5814 × 10 ^-8 C ₂₉ -1.6736 × 10 ^-8 C ₃₀ 1.0570 × 10 ^-9
C ₃₂ -7.5238 × 10 ^-10 C ₃₄ 5.2872 × 10 ^-10 C ₃₆ -7.2607 × 10 ^-10
Free curved surface [2]
C ₅ -1.6343 × 10 ^-2 C ₇ 3.7710 × 10 ^-3
Eccentricity (1)
x 0.000 y 0.000 z 24.518
α 8.00 β 0.00 γ 0.00
Eccentricity (2)
x 0.000 y 0.000 z 27.440
α 8.00 β 0.00 γ 0.00
Eccentricity (3)
x 0.000 y 6.782 z 26.229
α 15.69 β 0.00 γ 0.00
Eccentricity (4)
x 0.000 y 0.699 z 35.260
α -14.78 β 0.00 γ 0.00
Eccentricity (5)
x 0.000 y 15.855 z 30.393
α 71.61 β 0.00 γ 0.00
Eccentricity (6)
x 0.000 y 19.082 z 32.107
α 63.24 β 0.00 γ 0.00.

Example 5
Surface number Curvature radius Interval Eccentric Refractive index Abbe number Object surface ∞ ∞
1 ∞
2 ∞ Eccentricity (1) 1.4922 57.5
3 -37.874 Eccentricity (2)
4 -373.356 Eccentricity (3) 1.5254 56.2
5 Free-form surface [1] Eccentricity (4) 1.5254 56.2
6 -373.356 Eccentricity (3) 1.5254 56.2
7 Free-form surface [2] Eccentricity (5)
Image plane ∞ Eccentricity (6)
Free curved surface [1]
C ₅ -5.3785 × 10 ^-3 C ₇ -5.4 185 × 10 ^-3 C ₈ 1.5217 × 10 ^-5
C ₁₀ 1.8262 × 10 ^-5 C ₁₂ 4.0012 × 10 ^-7 C ₁₄ 7.4712 × 10 ^-7
C ₁₆ 1.0251 × 10 ^-7 C ₁₇ 9.4919 × 10 ^-8 C ₁₉ 7.8271 × 10 ^-8
C ₂₁ 4.6068 × 10 ^-8 C ₂₃ -1.6579 × 10 ^-10 C ₂₅ 5.1498 × 10 ^-10
C ₂₇ -3.8477 × 10 ^-9 C ₂₉ -3.6899 × 10 ^-10 C ₃₀ -1.9081 × 10 ^-10
C ₃₂ 5.8686 × 10 ^-11 C ₃₄ -2.3984 × 10 ^-10 C ₃₆ -9.6057 × 10 ^-11
Free curved surface [2]
C ₅ -1.8133 × 10 ^-2 C ₇ -2.5601 × 10 ^-3 C ₁₀ -2.9938 × 10 ^-3
C ₁₄ 2.2287 × 10 ^-4 C ₁₉ -5.8022 × 10 ^-6 C ₂₁ 2.5677 × 10 ^-6
Eccentricity (1)
x 0.000 y 0.000 z 23.000
α 8.00 β 0.00 γ 0.00
Eccentricity (2)
x 0.000 y 0.000 z 25.777
α 8.00 β 0.00 γ 0.00
Eccentricity (3)
x 0.000 y 7.743 z 24.367
α 20.08 β 0.00 γ 0.00
Eccentricity (4)
x 0.000 y 1.861 z 37.783
α -9.45 β 0.00 γ 0.00
Eccentricity (5)
x 0.000 y 18.771 z 36.281
α 59.55 β 0.00 γ 0.00
Eccentricity (6)
x 0.000 y 24.346 z 31.737
α 57.60 β 0.00 γ 0.00.

Example 6
Surface number Curvature radius Interval Eccentric Refractive index Abbe number Object surface ∞ ∞
1 ∞
2 ∞ Eccentricity (1) 1.4922 57.5
3 -39.148 Eccentricity (2)
4 -339.060 Eccentricity (3) 1.5254 56.2
5 Free-form surface [1] Eccentricity (4) 1.5254 56.2
6 -339.060 Eccentricity (3) 1.5254 56.2
7 -128.561 Eccentricity (5)
Image plane ∞ Eccentricity (6)
Free curved surface [1]
C ₅ -5.7696 × 10 ^-3 C ₇ -5.7406 × 10 ^-3 C ₈ -3.5694 × 10 ^-6
C ₁₀ 4.7342 × 10 ^-6 C ₁₂ 4.5764 × 10 ^-7 C ₁₄ -6.5090 × 10 ^-7
C ₁₆ -9.7442 × 10 ^-8 C ₁₇ 1.4161 × 10 ^-7 C ₁₉ -1.9916 × 10 ^-8
C ₂₁ 4.6421 × 10 ^-8 C ₂₃ -3.4757 × 10 ^-9 C ₂₅ 3.9046 × 10 ^-10
C ₂₇ 8.9761 × 10 ^-10 C ₂₉ -6.0018 × 10 ^-10 C ₃₀ -3.5136 × 10 ^-10
C ₃₂ -5.3507 × 10 ^-11 C ₃₄ 2.8835 × 10 ^-10 C ₃₆ -2.0588 × 10 ^-10
Eccentricity (1)
x 0.000 y 0.000 z 23.000
α 8.00 β 0.00 γ 0.00
Eccentricity (2)
x 0.000 y 0.000 z 25.694
α 8.00 β 0.00 γ 0.00
Eccentricity (3)
x 0.000 y 5.987 z 25.006
α 21.21 β 0.00 γ 0.00
Eccentricity (4)
x 0.000 y 2.685 z 37.406
α -8.92 β 0.00 γ 0.00
Eccentricity (5)
x 0.000 y 18.085 z 41.200
α 74.27 β 0.00 γ 0.00
Eccentricity (6)
x 0.000 y 24.298 z 30.742
α 66.38 β 0.00 γ 0.00.

  FIG. 9 is an aberration diagram showing the image distortion in Example 1 described above. In this aberration diagram, the vertical axis represents the image height in the X direction, and the horizontal axis represents the image height in the Y direction. Further, a lateral aberration diagram of Example 1 is shown in FIG. In this lateral aberration diagram, the numbers shown in parentheses indicate (horizontal (X direction) field angle, vertical (Y direction) field angle), and indicate lateral aberration at that field angle.

  The parameter values relating to the conditional expressions (A-1) to (H-1) in Examples 1 to 6 of the present invention are shown below.

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6
(A-1) 1.03591 1.03451 1.04142 1.01647 1.02169 1.02889
(B-1) 0.96941 0.99303 0.93780 1.09170 0.81502 0.87536
(C-1) 0.91610 0.94946 0.88252 1.05176 0.79386 0.85141
(D-1) 1.02151 1.011 1.02038 1.02116 1.00486 0.99926
(E-1) 0.09459 0.10135 0.25116 0.10847 0.09464 0.07108
(F-1) 0.00650 -0.00009 0.04298 -0.00424 0.02633 0.00185
(G-1) 0.00114 0.00056 0.00578 0.00149 0.00234 0.00138
(H-1) 3.32809 2.79477 2.45676 4.37771 3.12714 3.20561
.

  The decentered prism optical system of the present invention as described above can be used for an image display device. As an example, FIG. 11 shows a state in which a head-mounted image display device is mounted on the observer's head, and FIG. 12 shows a cross-sectional view thereof. In this configuration, the decentered prism optical system of the present invention is used as an eyepiece optical system 100 as shown in FIG. 12, and a pair of the eyepiece optical system 100 and the image display element 101 is prepared on the left and right sides, and these are set as the eye radial distance. It is configured as a portable image display device 102 such as a stationary or head-mounted image display device that can be observed with both eyes by being supported only apart.

  That is, the display device main body 102 is provided with a pair of left and right eyepiece optical systems 100 as described above, and an image display element 101 made up of a liquid crystal display element is arranged on the image plane correspondingly. As shown in FIG. 11, the display device main body 102 is provided with a temporal frame 103 as shown in the drawing so as to be continuous from side to side so that the display device main body 102 can be held in front of the observer's eyes. .

  In addition, a speaker 104 is attached to the temporal frame 103 so that stereophonic sound can be heard along with image observation. In this way, the display device main body 102 having the speaker 104 is connected with a playback device 106 such as a portable video cassette via the audio / video transmission cord 105, so that the observer can attach the playback device 106 to the belt as shown in the figure. It can be held at an arbitrary position such as a place to enjoy video and audio. Reference numeral 107 in FIG. 11 denotes an adjustment unit such as a switch or a volume of the playback device 106. Note that electronic components such as video processing and audio processing circuits are built in the display device main body 102.

  The cord 105 may be attached to an existing video deck or the like with a jack at the tip. Further, it may be connected to a TV radio wave receiving tuner for TV viewing, or may be connected to a computer to receive computer graphics video, message video from the computer, or the like. In addition, in order to eliminate disturbing cords, an antenna may be connected and an external signal may be received by radio waves.

  Furthermore, the decentered prism optical system of the present invention may be used for a one-eye head-mounted image display device in which the eyepiece optical system is disposed in front of either the left or right eye.

  The decentered prism optical system of the present invention can also be used for a photographing optical device and an observation optical device. As an example, it can be applied to a camera having a photographing optical system and a viewfinder optical system as shown in FIG. First, as shown in the optical path diagram of FIG. 14, the decentered prism optical system of the present invention is used as the rear group 153 of the objective lens 150 including the front group 151 and the rear group 153 with the pupil position (stop or virtual stop position) 152 interposed therebetween. Deploy. By doing so, the film 154 that can only be arranged perpendicularly to the optical axis Lb in the conventional photographing optical system can be arranged obliquely with respect to the optical axis Lb, so that the degree of freedom of arrangement increases and the size can be reduced. If an electronic light receiving element such as a CCD is arranged instead of the film 154, it can also be used for an electronic camera. Next, as shown in FIG. 15, an eccentric prism optical system 201 and a roof prism 203 having a roof surface 202 are arranged as means for erecting an image formed by the objective lens group 200 of the viewfinder optical system, The upright image is guided to the observer's eyeball 205 by the eyepiece lens 204. With this configuration, the height direction can be made lower than that of a conventional Porro prism, and the size can be reduced. In the figure, Le is the optical axis of the finder optical system.

  In addition, the objective lens of a rigid endoscope that transmits an image to an eyepiece lens using a relay lens, the objective lens of a flexible endoscope that transmits an image to an eyepiece lens using a bundle of optical fibers, and the CCD receive the image. It can also be used as an objective lens for electronic endoscopes. An example is shown in FIGS. FIG. 16 is an overall configuration diagram of an endoscope apparatus using a rigid endoscope (so-called rigid endoscope). An endoscope apparatus 30 shown in FIG. 16 includes an endoscope 20 having an insertion portion 22 that houses an objective lens and an illumination optical system, a camera 24, a monitor 25, and a light source device 27. As shown in FIG. 17, the endoscope 20 has a decentered prism optical system 31 according to the present invention (however, a negative lens is disposed on the incident side of the decentered prism, as shown in FIG. 17). )) And a light guide 33 for illuminating the viewing direction thereof are incorporated. The insertion unit 22 is provided with a relay lens system, which is an image and pupil transmission optical system, following the objective lens 32. An eyepiece optical system (not shown) is arranged on the base 23 of the endoscope 20, and a camera 24 as an imaging unit can be attached after the connection optical system. Here, the base 23 and the camera 24 of the endoscope 20 are configured as an integral type or a detachable type. The subject imaged by the camera 24 is finally displayed as an endoscopic image on the monitor 25 so that it can be observed by an observer. The illumination light from the light source device 27 passes through the light guide cable 26 and illuminates the visual field direction through the base portion 23, the insertion portion 22, and the distal end portion 21.

  The decentered prism optical system of the present invention described above can be configured as follows, for example.

[1] In a decentered prism optical system including a decentered prism having a configuration in which at least three surfaces are arranged eccentrically with each other and a space between the three surfaces is filled with a transparent medium having a refractive index of 1.3 or more.
The decentered prism forms at least two of the three surfaces with reflective surfaces so as to perform internal reflection at least twice, and is reflected by the two reflective surfaces. The surface having the two reflecting actions is arranged at a position where the light rays do not intersect inside the decentered prism, and one of the two faces having the reflecting action has a shape of both in-plane and out-of-plane. It is formed of a rotationally asymmetric surface that does not have a rotational symmetry axis, and the shape of at least the effective surface of one of the other surfaces (the region where light flux is transmitted and / or reflected in the entire surface area) rotates within the effective surface. It consists of a rotationally symmetric surface with a symmetry axis,
A decentered prism optical system, wherein a lens having positive refracting power is disposed on the incident side or the exit side of the decentered prism.

[2] In the decentered prism optical system according to [1], the rotationally symmetric surface of the decentered prism bends the light beam inside the decentered prism and a transmission action that causes the light beam that passes through the decentered prism to enter or exit. The rotationally asymmetric surface of the decentered prism is formed as a second surface that is disposed opposite to the first surface, and a light beam that passes through the decentered prism is emitted or incident. A third surface having a transmitting action is disposed at a position substantially perpendicular to a facing direction of the first surface and the second surface, and at least the eccentric prism includes the first surface and the second surface. A configuration including the third surface,
The decentered prism optical system according to claim 1, wherein the lens is disposed on an incident side or an exit side of the first surface.

    [3] In the decentered prism optical system according to the above [2], the first surface of the decentered prism is formed so that its transmission and reflection functions overlap at least in a part of the effective plane. In addition, the decentered prism optical system is configured so that at least the reflection action in the region where the transmission action and the reflection action in the effective surface of the first surface overlap is based on the total reflection action.

    [4] The decentered prism optical system according to [2] or [3], wherein the rotationally symmetric surface of the first surface of the decentered prism is formed of a rotationally symmetric aspherical surface. system.

    [5] The decentered prism optical system according to any one of [2] to [4], wherein the second surface of the decentered prism is an anamorphic surface. Optical system.

    [6] In the decentered prism optical system according to [5] above, the rotational symmetry axis of the rotational symmetry surface of the first surface is located within at least one symmetry surface among the two symmetry surfaces of the anamorphic surface. Thus, the decentered prism optical system, wherein the first surface and the second surface are arranged.

    [7] In the decentered prism optical system according to any one of [2] to [4], the second surface of the decentered prism is formed of a rotationally asymmetric surface having only one symmetric surface. A decentered prism optical system.

    [8] In the decentered prism optical system according to [7], the rotationally symmetric axis of the rotationally symmetric surface of the first surface is positioned within the symmetric surface of the rotationally asymmetric surface having only one symmetric surface. A decentered prism optical system, wherein the first surface and the second surface are disposed.

    [9] In the decentered prism optical system according to any one of [2] to [8], a light beam is incident from the third surface of the decentered prism, and the incident light beam passes through the inside of the optical system. The first light beam is reflected by the first surface, the light beam reflected by the first surface is reflected by the second surface, and the light beam reflected by the second surface is emitted from the first surface. A decentered prism optical system comprising: a surface, the second surface, and the third surface.

    [10] In the decentered prism optical system according to [9] above, the third surface of the decentered prism is disposed at a position where a light beam from means for displaying an image is incident, and the first surface is the first surface. The light beam emitted from the surface is arranged at a position where it is guided to the observer's eyeball through the lens having the positive refractive power, and is used for an image observation apparatus that allows an image formed by the light beam to be observed. A decentered prism optical system.

    [11] In the decentered prism optical system according to any one of [2] to [8] above, a light beam is incident on the decentered prism from the first surface via the lens having the positive refractive power, The incident light beam is reflected by the second surface, the light beam reflected by the second surface is reflected by the first surface, and the light beam reflected by the first surface passes through the optical system and passes through the optical system. The decentered prism optical system, wherein the first surface, the second surface, and the third surface are arranged so as to emit from a third surface.

    [12] In the decentered prism optical system according to [11], the first surface is disposed at a position where a light beam from an object enters through the lens having the positive refractive power, and the third surface is A decentered prism optical system, which is disposed in a position where a light beam emitted from the third surface is guided to an observer's eyeball and is used for an image observation apparatus capable of observing an image formed by the light beam. system.

    [13] In the decentered prism optical system according to [11], the first surface is disposed at a position where a light beam from an object enters through the lens having the positive refractive power, and the third surface is It is disposed at a position where a light beam emitted from the third surface is guided to a means for receiving an object image, and is used for a photographing optical apparatus that can photograph an object image formed by the light beam. Decentered prism optical system.

    [14] The decentered prism optical system according to any one of [2] to [8], wherein an axial principal ray that passes through the center of the pupil of the decentered prism optical system and reaches the center of the image plane exits the pupil. An axis defined by a straight line extending to the first surface of the lens having positive refracting power is defined as a Z axis, and is in the decentered plane of each surface that is orthogonal to the Z axis and constitutes the decentered prism optical system. A decentered prism optical system satisfying the following condition when an axis is defined as a Y-axis, and an axis perpendicular to the Z-axis and perpendicular to the Y-axis is defined as an X-axis:

0.7 <FA <1.3 (A-1)
However, the NA of the emitted light when a ray traced in parallel with the axial principal ray passes through a small amount H in the X-axis direction from the center of the pupil and enters the optical system in parallel with the axial principal ray. A value obtained by dividing (the value of the sin of the angle formed with the axial principal ray) by the above H is the focal length Fx in the X direction of the entire optical system, and passes through the point H in the Y direction from the center of the pupil. The value obtained by dividing the NA (the value of the sin of the angle formed with the axial principal ray) of the outgoing ray when tracing the ray incident on the optical system in parallel with the principal ray by the H in the Y direction of the entire optical system. The focal length is defined as Fy, and Fx / Fy is FA.

    [15] The decentered prism optical system according to any one of [2] to [8] and [14], wherein the axial principal ray passes through the center of the pupil of the decentered prism optical system and reaches the center of the image plane. A surface defined by a straight line extending from the pupil to the first surface of the lens having positive refractive power is defined as a Z axis, and each surface that is orthogonal to the Z axis and constitutes the decentered prism optical system The decentered prism optical system satisfies the following condition when an axis in the decentered plane is defined as the Y axis, and an axis perpendicular to the Z axis and perpendicular to the Y axis is defined as the X axis.

0.8 <| PxB | <1.3 (B-1)
However, the NA of the emitted light when a ray traced in parallel with the axial principal ray passes through a small amount H in the X-axis direction from the center of the pupil and enters the optical system in parallel with the axial principal ray. A value obtained by dividing (the value of the sin of the angle formed with the axial principal ray) by the above H is the focal length Fx in the X direction of the entire optical system, and passes through the point H in the Y direction from the center of the pupil. The value obtained by dividing the NA (the value of the sin of the angle formed with the axial principal ray) of the outgoing ray when tracing the ray incident on the optical system in parallel with the principal ray by the H in the Y direction of the entire optical system. It is defined as a focal length Fy, and the refractive power (power) in the X direction and Y direction of the surface at the position where the axial principal ray hits the second surface is Pxn and Pyn, respectively, and the focal lengths Fx and Y in the X direction The reciprocals of the focal length Fy in the direction are Px and Py, respectively, and Pxn / Px is PxB. .

    [16] The decentered prism optical system according to any one of [2] to [8] and [14] above, wherein the axial principal ray reaches the center of the image plane through the center of the pupil of the decentered prism optical system. A surface defined by a straight line extending from the pupil to the first surface of the lens having positive refractive power is defined as a Z axis, and each surface that is orthogonal to the Z axis and constitutes the decentered prism optical system The decentered prism optical system satisfies the following condition when an axis in the decentered plane is defined as the Y axis, and an axis perpendicular to the Z axis and perpendicular to the Y axis is defined as the X axis.

0.8 <| PyC | <1.3 (C-1)
However, the NA of the emitted light when a ray traced in parallel with the axial principal ray passes through a small amount H in the X-axis direction from the center of the pupil and enters the optical system in parallel with the axial principal ray. A value obtained by dividing (the value of the sin of the angle formed with the axial principal ray) by the above H is the focal length Fx in the X direction of the entire optical system, and passes through the point H in the Y direction from the center of the pupil. The value obtained by dividing the NA (the value of the sin of the angle formed with the axial principal ray) of the outgoing ray when tracing the ray incident on the optical system in parallel with the principal ray by the H in the Y direction of the entire optical system. It is defined as a focal length Fy, and the refractive power (power) in the X direction and Y direction of the surface at the position where the axial principal ray hits the second surface is Pxn and Pyn, respectively, and the focal lengths Fx and Y in the X direction The reciprocals of the focal length Fy in the direction are Px and Py, respectively, and Pyn / Py is PyC. .

    [17] In the decentered prism optical system according to any one of [2] to [8] and [14] to [16], the decentered prism optical system passes through the center of the pupil and reaches the center of the image plane. An axis defined by a straight line from the axial principal ray exiting the pupil and intersecting the first surface of the lens having the positive refractive power is defined as a Z axis, and the decentered prism optical system is orthogonal to the Z axis. An eccentric prism characterized by satisfying the following conditions when an axis within the eccentric surface of each surface constituting the surface is defined as a Y-axis, and an axis perpendicular to the Z-axis and orthogonal to the Y-axis is defined as an X-axis Optical system.

0.8 <CxyD <1.2 (D-1)
However, the ratio Cx2 / Cy2 between the curvature Cx2 in the X direction and the curvature Cy2 in the Y direction including the normal of the surface at the position where the axial principal ray hits the second surface is CxyD.

    [18] In the decentered prism optical system according to any one of [2] to [8] and [14] to [17], the decentered prism optical system passes through the center of the pupil and reaches the center of the image plane. An axis defined by a straight line from the axial principal ray exiting the pupil and intersecting the first surface of the lens having the positive refractive power is defined as a Z axis, and the decentered prism optical system is orthogonal to the Z axis. An eccentric prism characterized by satisfying the following conditions when an axis within the eccentric surface of each surface constituting the surface is defined as a Y-axis, and an axis perpendicular to the Z-axis and orthogonal to the Y-axis is defined as an X-axis Optical system.

-0.05 <CyE <0.5 (E-1)
However, the NA of the emitted light when a ray traced in parallel with the axial principal ray passes through a small amount H in the X-axis direction from the center of the pupil and enters the optical system in parallel with the axial principal ray. A value obtained by dividing (the value of the sin of the angle formed with the axial principal ray) by the above H is the focal length Fx in the X direction of the entire optical system, and passes through the point H in the Y direction from the center of the pupil. The value obtained by dividing the NA (the value of the sin of the angle formed with the axial principal ray) of the outgoing ray when tracing the ray incident on the optical system in parallel with the principal ray by the H in the Y direction of the entire optical system. The focal length Fy is defined, and the reciprocals of the focal length Fx in the X direction and the focal length Fy in the Y direction are Px and Py, respectively. The Y-direction curvature Cy1 of the effective area that hits the surface and the Y-direction maximum field angle with zero X-direction field angle What principal ray is divided by the difference Cy1-Cy3 the curvature Cy3 in the Y direction of the effective region corresponding to the second surface by said Py and CYE.

    [19] In the decentered prism optical system according to any one of [2] to [8] and [14] to [18], the decentered prism optical system passes through the center of the pupil and reaches the center of the image plane. An axis defined by a straight line from the axial principal ray exiting the pupil and intersecting the first surface of the lens having the positive refractive power is defined as a Z axis, and the decentered prism optical system is orthogonal to the Z axis. An eccentric prism characterized by satisfying the following conditions when an axis within the eccentric surface of each surface constituting the surface is defined as a Y-axis, and an axis perpendicular to the Z-axis and orthogonal to the Y-axis is defined as an X-axis Optical system.

-0.01 <CxF <0.1 (F-1)
However, the NA of the emitted light when a ray traced in parallel with the axial principal ray passes through a small amount H in the X-axis direction from the center of the pupil and enters the optical system in parallel with the axial principal ray. A value obtained by dividing (the value of the sin of the angle formed with the axial principal ray) by the above H is the focal length Fx in the X direction of the entire optical system, and passes through the point H in the Y direction from the center of the pupil. The value obtained by dividing the NA (the value of the sin of the angle formed with the axial principal ray) of the outgoing ray when tracing the ray incident on the optical system in parallel with the principal ray by the H in the Y direction of the entire optical system. The focal length Fy is defined, and the reciprocals of the focal length Fx in the X direction and the focal length Fy in the Y direction are Px and Py, respectively. The X-direction curvature Cx1 of the effective area that hits the surface and the Y-direction maximum field angle with zero X-direction field angle What principal ray is divided by the difference Cx1-Cx3 the X-direction curvature Cx3 effective region corresponding to the second surface in the Px and CxF.

    [20] In the decentered prism optical system according to any one of [2] to [8] and [14] to [19], the decentered prism optical system passes through the center of the pupil and reaches the center of the image plane. An axis defined by a straight line from the axial principal ray exiting the pupil and intersecting the first surface of the lens having the positive refractive power is defined as a Z axis, and the decentered prism optical system is orthogonal to the Z axis. An eccentric prism characterized by satisfying the following conditions when an axis within the eccentric surface of each surface constituting the surface is defined as a Y-axis, and an axis perpendicular to the Z-axis and orthogonal to the Y-axis is defined as an X-axis Optical system.

−0.1 <| DY | <5 (°) (G-1)
However, the normal of the surface at the point where the principal ray having the maximum angle of view in the X direction intersects the second surface and the normal of the surface at the point where the axial principal ray intersects the second surface are Y Let DY be the angle formed in the -Z plane.

    [21] In the decentered prism optical system described in any one of [2] to [8] and [14] to [20], the decentered prism optical system passes through the center of the pupil and reaches the center of the image plane. An axis defined by a straight line from the axial principal ray exiting the pupil and intersecting the first surface of the lens having the positive refractive power is defined as a Z axis, and the decentered prism optical system is orthogonal to the Z axis. An eccentric prism characterized by satisfying the following conditions when an axis within the eccentric surface of each surface constituting the surface is defined as a Y-axis, and an axis perpendicular to the Z-axis and orthogonal to the Y-axis is defined as an X-axis Optical system.

1.1 <F / Fy <10000 (H-1)
However, the focal length of the lens having positive refracting power is F, passing through a point of a minute amount H in the Y-axis direction from the center of the pupil in parallel with the axial principal ray, and parallel to the axial principal ray. A value obtained by dividing the NA (the value of the sin of the angle formed with the axial principal ray) when the ray incident on the ray is divided by H is the focal length Fy in the Y direction of the entire optical system.

    [22] The decentered prism optical system according to any one of [1] to [21], wherein the transparent medium of the decentered prism is made of a material having a low water absorption coefficient. .

[23] In the decentered prism optical system according to [22], the water absorption α of the transparent medium is
0 <α <0.1 (%) (I-1)
An eccentric prism optical system characterized by satisfying

    [24] The decentered prism optical system according to [22] or [23], wherein the transparent medium is made of a polyolefin resin.

    [25] The decentered prism optical system according to any one of [22] to [24], wherein the lens having positive refractive power enlarges the action and the angle of view for preventing the decentered prism from being damaged. A decentered prism optical system characterized in that it is formed so as to have a function of

FIG. 5 is an optical path diagram in the case where the decentered prism, which is the main part of the decentered prism optical system of the present invention, is the simplest three-surface configuration prism. FIG. 6 is an optical path diagram for illustrating another configuration of a decentered prism that can be used in the optical system of the present invention. It is sectional drawing of the decentered prism optical system of Example 1 of this invention. It is sectional drawing of the decentered prism optical system of Example 2 of this invention. It is sectional drawing of the decentered prism optical system of Example 3 of this invention. It is sectional drawing of the decentered prism optical system of Example 4 of this invention. It is sectional drawing of the decentered prism optical system of Example 5 of this invention. It is sectional drawing of the decentered prism optical system of Example 6 of this invention. 3 is an aberration diagram illustrating image distortion in Example 1. FIG. FIG. 3 is a lateral aberration diagram of Example 1. It is a figure which shows the state which mounted | wore the observer's head with the head-mounted image display apparatus using the eccentric prism optical system of this invention. It is sectional drawing of the head vicinity of FIG. It is a perspective view which shows the structure of the camera using the decentered prism optical system of this invention. It is an optical path diagram of a photographing optical system using the decentered prism optical system of the present invention. It is an optical path diagram of a finder optical system using the decentered prism optical system of the present invention. 1 is an overall configuration diagram of an endoscope apparatus. FIG. It is sectional drawing of the front-end | tip part of the rigid type | mold endoscope using the eccentric prism optical system of this invention. It is a figure for demonstrating the parameter DY used in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Pupil 2 ... Optical axis 3 ... Decentered prism 1st surface 4 ... Decentered prism 2nd surface 5 ... Decentered prism 3rd surface 6 ... Image surface 7 ... Decentered prism 8 ... Decentered prism 4th surface 9 ... Refraction Lens system 9 '... Positive single lens 10 ... Eccentric prism optical system 20 ... Endoscope 21 ... End part 22 ... Insertion part 23 ... Base part 24 ... Camera 25 ... Monitor 26 ... Light guide cable 27 ... Light source device 30 ... Endoscope Device 31 ... Decentered prism optical system 32 ... Objective lens 33 ... Light guide 100 ... Eyepiece optical system 101 ... Image display element 102 ... Image display device (display device body)
DESCRIPTION OF SYMBOLS 103 ... Temporal frame 104 ... Speaker 105 ... Audiovisual transmission code 106 ... Playback apparatus 107 ... Adjustment part 150 ... Objective lens 151 ... Front group 152 ... Pupil position 153 ... Rear group 154 ... Film 200 ... Objective lens group 201 ... Eccentric prism Optical system 202 ... roof surface 203 ... roof prism 204 ... eyepiece 205 ... observer eye La ... optical axis Lb of viewfinder optical system ... optical axis of photographing optical system

Claims (10)

In a decentered prism optical system comprising a decentered prism having a configuration in which at least three surfaces are arranged eccentrically with each other and a space between the three surfaces is filled with a transparent medium having a refractive index of 1.3 or more.
The decentered prism is formed of at least two of the three surfaces with a reflecting surface so as to perform at least two internal reflections and is reflected by the two reflecting surfaces. A surface having the two reflecting actions at a position where the light beam does not intersect inside the decentered prism,
Of the two surfaces having the reflective action, the shape of one surface is formed by a rotationally asymmetric surface that does not have a rotationally symmetric axis both in and out of the surface, and the other surface has at least a predetermined effective surface. Prepared,
When an effective surface is a region where light flux is transmitted and / or reflected in the entire region of the other one surface, the predetermined effective surface is a rotationally symmetric surface having a rotational symmetry axis in the effective surface. Configured,
In a decentered prism optical system in which a lens having positive refractive power is disposed on the incident side or the exit side of the decentered prism,
An axis defined by a straight line extending from the center of the pupil of the decentered prism optical system and reaching the center of the image plane until the axial principal ray exits the pupil and intersects the first surface of the lens having the positive refractive power. Is defined as the Z axis, and the axis within the decentered surface of each surface constituting the decentered prism optical system is defined as the Y axis, and the axis perpendicular to the Z axis and orthogonal to the Y axis is defined as the X axis. A decentered prism optical system that satisfies the following conditions when defined as:
0.7 <FA <1.3 (A-1)
However, the NA of the emitted light when a ray traced in parallel with the axial principal ray passes through a small amount H in the X-axis direction from the center of the pupil and enters the optical system in parallel with the axial principal ray. A value obtained by dividing (the value of the sin of the angle formed with the axial principal ray) by the above H is the focal length Fx in the X direction of the entire optical system, and passes through the point H in the Y direction from the center of the pupil. The value obtained by dividing the NA (the value of the sin of the angle formed with the axial principal ray) of the outgoing ray when tracing the ray incident on the optical system in parallel with the principal ray by the H in the Y direction of the entire optical system. The focal length is defined as Fy, and Fx / Fy is FA. In a decentered prism optical system comprising a decentered prism having a configuration in which at least three surfaces are arranged eccentrically with each other and a space between the three surfaces is filled with a transparent medium having a refractive index of 1.3 or more.
The decentered prism is formed of at least two of the three surfaces with a reflecting surface so as to perform at least two internal reflections and is reflected by the two reflecting surfaces. A surface having the two reflecting actions at a position where the light beam does not intersect inside the decentered prism,
Of the two surfaces having the reflective action, the shape of one surface is formed by a rotationally asymmetric surface that does not have a rotationally symmetric axis both in and out of the surface, and the other surface has at least a predetermined effective surface. Prepared,
When an effective surface is a region where light flux is transmitted and / or reflected in the entire region of the other one surface, the predetermined effective surface is a rotationally symmetric surface having a rotational symmetry axis in the effective surface. Configured,
In a decentered prism optical system in which a lens having positive refractive power is disposed on the incident side or the exit side of the decentered prism,
An axis defined by a straight line extending from the center of the pupil of the decentered prism optical system and reaching the center of the image plane until the axial principal ray exits the pupil and intersects the first surface of the lens having the positive refractive power. Is defined as the Z axis, and the axis within the decentered surface of each surface constituting the decentered prism optical system is defined as the Y axis, and the axis perpendicular to the Z axis and orthogonal to the Y axis is defined as the X axis. A decentered prism optical system that satisfies the following conditions when defined as:
0.8 <| PxB | <1.3 (B-1)
However, the NA of the emitted light when a ray traced in parallel with the axial principal ray passes through a small amount H in the X-axis direction from the center of the pupil and enters the optical system in parallel with the axial principal ray. A value obtained by dividing (the value of the sin of the angle formed with the axial principal ray) by the above H is the focal length Fx in the X direction of the entire optical system, and passes through the point H in the Y direction from the center of the pupil. The value obtained by dividing the NA (the value of the sin of the angle formed with the axial principal ray) of the outgoing ray when tracing the ray incident on the optical system in parallel with the principal ray by the H in the Y direction of the entire optical system. It is defined as a focal length Fy, and the refractive power (power) in the X direction and Y direction of the surface at the position where the axial principal ray hits the second surface is Pxn and Pyn, respectively, and the focal lengths Fx and Y in the X direction The reciprocals of the focal length Fy in the direction are Px and Py, respectively, and Pxn / Px is PxB. . In a decentered prism optical system comprising a decentered prism having a configuration in which at least three surfaces are arranged eccentrically with each other and a space between the three surfaces is filled with a transparent medium having a refractive index of 1.3 or more.
The decentered prism is formed of at least two of the three surfaces with a reflecting surface so as to perform at least two internal reflections and is reflected by the two reflecting surfaces. A surface having the two reflecting actions at a position where the light beam does not intersect inside the decentered prism,
Of the two surfaces having the reflective action, the shape of one surface is formed by a rotationally asymmetric surface that does not have a rotationally symmetric axis both in and out of the surface, and the other surface has at least a predetermined effective surface. Prepared,
When an effective surface is a region where light flux is transmitted and / or reflected in the entire region of the other one surface, the predetermined effective surface is a rotationally symmetric surface having a rotational symmetry axis in the effective surface. Configured,
In a decentered prism optical system in which a lens having positive refractive power is disposed on the incident side or the exit side of the decentered prism,
An axis defined by a straight line extending from the center of the pupil of the decentered prism optical system and reaching the center of the image plane until the axial principal ray exits the pupil and intersects the first surface of the lens having the positive refractive power. Is defined as the Z axis, and the axis within the decentered surface of each surface constituting the decentered prism optical system is defined as the Y axis, and the axis perpendicular to the Z axis and orthogonal to the Y axis is defined as the X axis. A decentered prism optical system that satisfies the following conditions when defined as:
0.8 <| PyC | <1.3 (C-1)
However, the NA of the emitted light when a ray traced in parallel with the axial principal ray passes through a small amount H in the X-axis direction from the center of the pupil and enters the optical system in parallel with the axial principal ray. A value obtained by dividing (the value of the sin of the angle formed with the axial principal ray) by the above H is the focal length Fx in the X direction of the entire optical system, and passes through the point H in the Y direction from the center of the pupil. The value obtained by dividing the NA (the value of the sin of the angle formed with the axial principal ray) of the outgoing ray when tracing the ray incident on the optical system in parallel with the principal ray by the H in the Y direction of the entire optical system. It is defined as a focal length Fy, and the refractive power (power) in the X direction and Y direction of the surface at the position where the axial principal ray hits the second surface is Pxn and Pyn, respectively, and the focal lengths Fx and Y in the X direction The reciprocals of the focal length Fy in the direction are Px and Py, respectively, and Pyn / Py is PyC. . In a decentered prism optical system comprising a decentered prism having a configuration in which at least three surfaces are arranged eccentrically with each other and a space between the three surfaces is filled with a transparent medium having a refractive index of 1.3 or more.
The decentered prism is formed of at least two of the three surfaces with a reflecting surface so as to perform at least two internal reflections and is reflected by the two reflecting surfaces. A surface having the two reflecting actions at a position where the light beam does not intersect inside the decentered prism,
Of the two surfaces having the reflective action, the shape of one surface is formed by a rotationally asymmetric surface that does not have a rotationally symmetric axis both in and out of the surface, and the other surface has at least a predetermined effective surface. Prepared,
When an effective surface is a region where light flux is transmitted and / or reflected in the entire region of the other one surface, the predetermined effective surface is a rotationally symmetric surface having a rotational symmetry axis in the effective surface. Configured,
In a decentered prism optical system in which a lens having positive refractive power is disposed on the incident side or the exit side of the decentered prism,
An axis defined by a straight line extending from the center of the pupil of the decentered prism optical system and reaching the center of the image plane until the axial principal ray exits the pupil and intersects the first surface of the lens having the positive refractive power. Is defined as the Z axis, and the axis within the decentered surface of each surface constituting the decentered prism optical system is defined as the Y axis, and the axis perpendicular to the Z axis and orthogonal to the Y axis is defined as the X axis. A decentered prism optical system that satisfies the following condition when defined as:
0.8 <CxyD <1.2 (D-1)
However, the ratio Cx2 / Cy2 between the curvature Cx2 in the X direction and the curvature Cy2 in the Y direction including the normal of the surface at the position where the axial principal ray hits the second surface is CxyD. In a decentered prism optical system comprising a decentered prism having a configuration in which at least three surfaces are arranged eccentrically with each other and a space between the three surfaces is filled with a transparent medium having a refractive index of 1.3 or more.
The decentered prism is formed of at least two of the three surfaces with a reflecting surface so as to perform at least two internal reflections and is reflected by the two reflecting surfaces. A surface having the two reflecting actions at a position where the light beam does not intersect inside the decentered prism,
Of the two surfaces having the reflective action, the shape of one surface is formed by a rotationally asymmetric surface that does not have a rotationally symmetric axis both in and out of the surface, and the other surface has at least a predetermined effective surface. Prepared,
When an effective surface is a region where light flux is transmitted and / or reflected in the entire region of the other one surface, the predetermined effective surface is a rotationally symmetric surface having a rotational symmetry axis in the effective surface. Configured,
In a decentered prism optical system in which a lens having positive refractive power is disposed on the incident side or the exit side of the decentered prism,
An axis defined by a straight line extending from the center of the pupil of the decentered prism optical system and reaching the center of the image plane until the axial principal ray exits the pupil and intersects the first surface of the lens having the positive refractive power. Is defined as the Z axis, and the axis within the decentered surface of each surface constituting the decentered prism optical system is defined as the Y axis, and the axis perpendicular to the Z axis and orthogonal to the Y axis is defined as the X axis. A decentered prism optical system that satisfies the following condition when defined as:
-0.05 <CyE <0.5 (E-1)
However, the NA of the emitted light when a ray traced in parallel with the axial principal ray passes through a small amount H in the X-axis direction from the center of the pupil and enters the optical system in parallel with the axial principal ray. A value obtained by dividing (the value of the sin of the angle formed with the axial principal ray) by the above H is the focal length Fx in the X direction of the entire optical system, and passes through the point H in the Y direction from the center of the pupil. The value obtained by dividing the NA (the value of the sin of the angle formed with the axial principal ray) of the outgoing ray when tracing the ray incident on the optical system in parallel with the principal ray by the H in the Y direction of the entire optical system. The focal length Fy is defined, and the reciprocals of the focal length Fx in the X direction and the focal length Fy in the Y direction are Px and Py, respectively. The Y-direction curvature Cy1 of the effective area that hits the surface and the Y-direction maximum field angle with zero X-direction field angle What principal ray is divided by the difference Cy1-Cy3 the curvature Cy3 in the Y direction of the effective region corresponding to the second surface by said Py and CYE. In a decentered prism optical system comprising a decentered prism having a configuration in which at least three surfaces are arranged eccentrically with each other and a space between the three surfaces is filled with a transparent medium having a refractive index of 1.3 or more.
The decentered prism is formed of at least two of the three surfaces with a reflecting surface so as to perform at least two internal reflections and is reflected by the two reflecting surfaces. A surface having the two reflecting actions at a position where the light beam does not intersect inside the decentered prism,
Of the two surfaces having the reflective action, the shape of one surface is formed by a rotationally asymmetric surface that does not have a rotationally symmetric axis both in and out of the surface, and the other surface has at least a predetermined effective surface. Prepared,
When an effective surface is a region where light flux is transmitted and / or reflected in the entire region of the other one surface, the predetermined effective surface is a rotationally symmetric surface having a rotational symmetry axis in the effective surface. Configured,
In a decentered prism optical system in which a lens having positive refractive power is disposed on the incident side or the exit side of the decentered prism,
An axis defined by a straight line extending from the center of the pupil of the decentered prism optical system and reaching the center of the image plane until the axial principal ray exits the pupil and intersects the first surface of the lens having the positive refractive power. Is defined as the Z axis, and the axis within the decentered surface of each surface constituting the decentered prism optical system is defined as the Y axis, and the axis perpendicular to the Z axis and orthogonal to the Y axis is defined as the X axis. A decentered prism optical system that satisfies the following condition when defined as:
-0.01 <CxF <0.1 (F-1)
However, the NA of the emitted light when a ray traced in parallel with the axial principal ray passes through a small amount H in the X-axis direction from the center of the pupil and enters the optical system in parallel with the axial principal ray. A value obtained by dividing (the value of the sin of the angle formed with the axial principal ray) by the above H is the focal length Fx in the X direction of the entire optical system, and passes through the point H in the Y direction from the center of the pupil. The value obtained by dividing the NA (the value of the sin of the angle formed with the axial principal ray) of the outgoing ray when tracing the ray incident on the optical system in parallel with the principal ray by the H in the Y direction of the entire optical system. The focal length Fy is defined, and the reciprocals of the focal length Fx in the X direction and the focal length Fy in the Y direction are Px and Py, respectively. The X-direction curvature Cx1 of the effective area that hits the surface and the Y-direction maximum field angle with zero X-direction field angle What principal ray is divided by the difference Cx1-Cx3 the X-direction curvature Cx3 effective region corresponding to the second surface in the Px and CxF. In a decentered prism optical system comprising a decentered prism having a configuration in which at least three surfaces are arranged eccentrically with each other and a space between the three surfaces is filled with a transparent medium having a refractive index of 1.3 or more.
The decentered prism is formed of at least two of the three surfaces with a reflecting surface so as to perform at least two internal reflections and is reflected by the two reflecting surfaces. A surface having the two reflecting actions at a position where the light beam does not intersect inside the decentered prism,
Of the two surfaces having the reflective action, the shape of one surface is formed by a rotationally asymmetric surface that does not have a rotationally symmetric axis both in and out of the surface, and the other surface has at least a predetermined effective surface. Prepared,
When an effective surface is a region where light flux is transmitted and / or reflected in the entire region of the other one surface, the predetermined effective surface is a rotationally symmetric surface having a rotational symmetry axis in the effective surface. Configured,
In a decentered prism optical system in which a lens having positive refractive power is disposed on the incident side or the exit side of the decentered prism,
An axis defined by a straight line extending from the center of the pupil of the decentered prism optical system and reaching the center of the image plane until the axial principal ray exits the pupil and intersects the first surface of the lens having the positive refractive power. Is defined as the Z axis, and the axis within the decentered surface of each surface constituting the decentered prism optical system is defined as the Y axis, and the axis perpendicular to the Z axis and orthogonal to the Y axis is defined as the X axis. A decentered prism optical system that satisfies the following condition when defined as:
−0.1 <| DY | <5 (°) (G-1)
However, the normal of the surface at the point where the principal ray having the maximum angle of view in the X direction intersects the second surface and the normal of the surface at the point where the axial principal ray intersects the second surface are Y Let DY be the angle formed in the -Z plane. In a decentered prism optical system comprising a decentered prism having a configuration in which at least three surfaces are arranged eccentrically with each other and a space between the three surfaces is filled with a transparent medium having a refractive index of 1.3 or more.
The decentered prism is formed of at least two of the three surfaces with a reflecting surface so as to perform at least two internal reflections and is reflected by the two reflecting surfaces. A surface having the two reflecting actions at a position where the light beam does not intersect inside the decentered prism,
Of the two surfaces having the reflective action, the shape of one surface is formed by a rotationally asymmetric surface that does not have a rotationally symmetric axis both in and out of the surface, and the other surface has at least a predetermined effective surface. Prepared,
When an effective surface is a region where light flux is transmitted and / or reflected in the entire region of the other one surface, the predetermined effective surface is a rotationally symmetric surface having a rotational symmetry axis in the effective surface. Configured,
In a decentered prism optical system in which a lens having positive refractive power is disposed on the incident side or the exit side of the decentered prism,
An axis defined by a straight line extending from the center of the pupil of the decentered prism optical system and reaching the center of the image plane until the axial principal ray exits the pupil and intersects the first surface of the lens having the positive refractive power. Is defined as the Z axis, and the axis within the decentered surface of each surface constituting the decentered prism optical system is defined as the Y axis, and the axis perpendicular to the Z axis and orthogonal to the Y axis is defined as the X axis. A decentered prism optical system that satisfies the following condition when defined as:
1.1 <F / Fy <10000 (H-1)
However, the focal length of the lens having positive refracting power is F, passing through a point of a minute amount H in the Y-axis direction from the center of the pupil in parallel with the axial principal ray, and parallel to the axial principal ray. A value obtained by dividing the NA (the value of the sin of the angle formed with the axial principal ray) when the ray incident on the ray is divided by H is the focal length Fy in the Y direction of the entire optical system. In a decentered prism optical system comprising a decentered prism having a configuration in which at least three surfaces are arranged eccentrically with each other and a space between the three surfaces is filled with a transparent medium having a refractive index of 1.3 or more.
The decentered prism is formed of at least two of the three surfaces with a reflecting surface so as to perform at least two internal reflections and is reflected by the two reflecting surfaces. A surface having the two reflecting actions at a position where the light beam does not intersect inside the decentered prism,
Of the two surfaces having the reflective action, the shape of one surface is formed by a rotationally asymmetric surface that does not have a rotationally symmetric axis both in and out of the surface, and the other surface has at least a predetermined effective surface. Prepared,
When an effective surface is a region where light flux is transmitted and / or reflected in the entire region of the other one surface, the predetermined effective surface is a rotationally symmetric surface having a rotational symmetry axis in the effective surface. Configured,
In a decentered prism optical system in which a lens having positive refractive power is disposed on the incident side or the exit side of the decentered prism,
The decentered prism optical system, wherein the transparent medium of the decentered prism is made of a material having a small coefficient of water absorption linear expansion. In a decentered prism optical system comprising a decentered prism having a configuration in which at least three surfaces are arranged eccentrically with each other and a space between the three surfaces is filled with a transparent medium having a refractive index of 1.3 or more.
The decentered prism is formed of at least two of the three surfaces with a reflecting surface so as to perform at least two internal reflections and is reflected by the two reflecting surfaces. A surface having the two reflecting actions at a position where the light beam does not intersect inside the decentered prism,
Of the two surfaces having the reflective action, the shape of one surface is formed by a rotationally asymmetric surface that does not have a rotationally symmetric axis both in and out of the surface, and the other surface has at least a predetermined effective surface. Prepared,
When an effective surface is a region where light flux is transmitted and / or reflected in the entire region of the other one surface, the predetermined effective surface is a rotationally symmetric surface having a rotational symmetry axis in the effective surface. Configured,
An optical apparatus having a decentered prism optical system in which a lens having positive refractive power is disposed on the incident side or the exit side of the decentered prism.

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