JPH10221602A - Eccentric prism optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an eccentric prism optical system constituting a surface with a wide effective area of a first surface having a transmissive action and a reflective action of a side close to a pupil with a rotation symmetric spherical surface or aspherical surface. SOLUTION: This optical system consists of three surfaces 3, 4, 5, and a transparent medium with a diffractive index of 1.3 or above is buried between these surfaces, and light flux outgoing from an object passes through the pupil 1 of the optical system 7 first along an optical axis 2, and is made incident on the first surface 3 to enter the optical system 7, and is reflected in the direction approaching the pupil 1 by a second surface 4, and is reflected in the direction receding from the pupil 1 by the first surface 3 this time, and its reflected light transmits through a third surface 5, and arrives at an image surface 6 to be image formed. The first surface 3 is constituted of a rotation symmetric surface such as an aspherical surface, etc., and the second surface 4 is constituted of a rotation asymmetric surface, and an angle α that the rotation central axis 12 of the rotation symmetric aspherical surface of the first surface 3 intersects with the optical axis 2 is decided within the range of 5 deg.<α<30 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an eccentric prism optical system, and more particularly to an eccentric prism optical system having good manufacturability which can be used for an eyepiece optical system or an imaging optical system.

[0002]

2. Description of the Related Art Conventionally known well-known decentered prism optical systems are disclosed in Japanese Patent Application Laid-Open Nos. 7-333551 and 8-2.
No. 34137. Further, Japanese Patent Application Laid-Open No.
JP-A-320452 and JP-A-8-313829. Each of these uses a rotationally asymmetric surface shape for a surface having a reflecting action.

[0003]

However, in these prior arts, the first surface on the pupil side having the transmission and reflection functions is constituted by a rotationally asymmetric surface, and the second surface on the side far from the pupil having only the reflection function is formed. Both are composed of rotationally asymmetric surfaces such as an anamorphic surface and a toric surface. For this reason, when measuring whether the shape according to the design value is made in manufacturing the optical system, the accuracy of the surface can not 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 device. However, since the three-dimensional coordinate measuring device measures the coordinates of points one by one, there are problems that the measurement accuracy is insufficient and the measurement takes a very long time.

It is disclosed in the above-mentioned prior art that the third surface having only the transmitting action is designed to be rotationally symmetric. However, the surface having only the transmitting action has a narrow effective area, and the optical system has a small area. It is difficult to estimate whether or not the whole is formed in the correct shape based on only this surface. Since the first surface having the reflection and transmission functions closer to the pupil has a large effective area, it is convenient to use it as a reference when estimating whether or not the entire optical system is distorted. In particular, when performing plastic injection molding (molding), it is important to reduce the change in the shape of the entire optical system.
Estimating the shape of the entire optical system by measuring a surface having a large effective surface (a region where a light flux transmits or reflects at least one of the entire region of the surface) is an effective means for mass production.

The present invention has been made in view of such problems of the prior art, and an object of the present invention is to rotate a surface having a wide effective area of a first surface having a transmitting action and a reflecting action near a pupil. An object of the present invention is to provide a decentered prism optical system constituted by a symmetric spherical or aspherical surface.

[0006]

The eccentric prism optical system according to the present invention, which achieves the above object, has at least three surfaces decentered from each other, and a refractive index between the three surfaces is 1.0.
In a decentered prism optical system configured to be filled with three or more transparent media, at least two of the three surfaces are reflected by a surface having a reflecting action so that the optical system performs internal reflection at least twice. The two surfaces having the two reflecting functions are arranged at positions where the light rays reflected by the two surfaces having the two reflecting effects are turned back inside the optical system. in,
The shape of one surface is formed by a rotationally asymmetric surface having no axis of rotational symmetry both in-plane and out-of-plane, and at least an effective surface of another surface (light flux is transmitted and / or reflected in the entire area of the surface). Is formed of a rotationally symmetric aspherical surface having a rotationally symmetric axis in an effective plane, and the symmetrical aspherical surface has a transmissive action of allowing a light beam passing through the optical system to enter or exit, and the inside of the optical system. Is formed as a first surface having both a reflection function of bending the light beam and the rotationally asymmetric surface is formed as a second surface arranged opposite to the first surface, and further emits or transmits a light beam passing through the optical system. A third surface having a transmissive function to be incident is disposed at a position substantially perpendicular to a direction in which the first surface and the second surface face each other, and the first surface is oriented in the direction of the second surface. It is configured in a shape with a convex surface, and the following It is characterized in that to satisfy the matter. 5 ° <α <30 ° (0-1) where α is the rotation center axis of the rotationally symmetric aspheric surface of the first surface that reaches the image plane center through the center of the pupil of the optical system. This is the angle at which the on-axis principal ray intersects with the straight line from the exit of the pupil to the intersection with the first surface (the inclination angle of the surface).

Another eccentric prism optical system according to the present invention has an eccentric structure in which at least three surfaces are arranged eccentric to 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 the prism optical system, the optical system forms at least two of the three surfaces by a surface having a reflective function so as to perform at least two internal reflections, and has the two reflective functions. The two surfaces having the reflecting action are arranged at positions where the light reflected by the surface is turned back inside the optical system. Among the two surfaces having the reflecting action, the shape of one face is in-plane and It is formed of a rotationally asymmetric surface having no rotationally symmetric axis both out of the plane, and the shape of at least an effective surface of another surface (a region through which light flux is transmitted and / or reflected in the entire surface) is an effective surface. Within the axis of rotational symmetry It is composed of rotationally symmetric spherical surface,
The symmetric spherical surface is formed as a first surface having both a transmitting function of causing a light beam passing through the optical system to enter or exit and a reflecting function of bending the light beam inside the optical system, and the rotationally asymmetric surface is the first surface. And a third surface having a transmissive action of emitting or entering a light beam passing through the optical system with respect to a direction in which the first surface and the second surface face each other. In a substantially vertical position, and the first surface is the second surface.
It is configured in a shape with a convex surface facing the direction of the surface, and satisfies the following conditions. 5 ° <α <30 ° (0-1) where α is a point at which the axial principal ray reaching the center of the image plane through the center of the pupil of the optical system is reflected by the first surface. The angle at which the central axis of rotation of the passing symmetric sphere intersects with the straight line from the center of the pupil of the optical system to the axial principal ray reaching the center of the image plane exiting the pupil and intersecting the first surface ( Angle of inclination of the surface).

In these decentered prism optical systems, the first surface is formed so that the transmission function and the reflection function overlap in at least a part of the effective surface, and at least the effective surface of the first surface. It is desirable that the reflection action in the area where the transmission action and the reflection action overlap in the inside is based on the total reflection action.

In the following, the reason and operation of the above-described configuration in the present invention will be described. First of all,
The principle of the decentered prism optical system of the present invention will be described. In explaining, to make the content more understandable,
The optical path diagram of the simplest three-sided prism in the present invention is illustrated in FIG. 1 and will be described with reference to FIG. In the case of FIG. 1, the surface arranged on the optical path of the decentered prism optical system 7 is:
It consists of three faces 3, 4, 5. This optical system 7
A light beam emitted from an object (not shown) first passes through the pupil 1 of the optical system 7 and enters the first surface 3 of the optical system 7 having a transmitting action and a reflecting action. Then, the incident light is reflected on the second surface 4, which is a reflection surface having only a reflection action on the side far from the pupil 1, by the pupil 1.
Is reflected again in the direction away from the pupil 1 this time by the first surface 3 having a transmitting action and a reflecting action arranged closer to the pupil 1. Then, the reflected light is directed in the direction in which the first surface 3 and the second surface 4 face each other (the Z-axis direction in the figure).
The light passes through the third surface 5 which is arranged at a position substantially in the vertical direction (Y-axis direction in the drawing) and has only a transmitting action, reaches the image plane 6, and forms an image. Note that reference numeral 2 is an optical axis. Thus, the surface number of the optical system in the present invention is, in principle, the pupil 1
The tracking is performed in the order from to the image plane 6.

However, FIG. 1 is an example, and the decentered prism optical system 7 of the present invention has four optical surfaces as shown in FIG.
It may have a surface, or may have more than two reflections. FIG. 2A shows an eccentric prism optical system 7 having four surfaces of a 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. May be a rotationally symmetric spherical surface or a rotationally symmetric aspherical surface, but is preferably formed of a rotationally asymmetrical aspherical surface having only one anamorphic surface or one symmetrical surface. FIG. 2B is an example in which the first surface 3 and the third surface 5 are shared by the same surface.

Now, of at least three surfaces constituting such an eccentric prism optical system, a first surface having a transmitting action and a reflecting action arranged on the pupil side is constituted by a rotationally symmetric face, and is far from the pupil. It is preferable that the second surface having only the reflection function is constituted by a rotationally asymmetric surface.

This is because, when a light ray that exits the center of the object, passes through the center of the pupil, and reaches the center of the image plane is defined as an axial principal ray,
The point at which the axial principal ray of the first surface having the transmitting and reflecting actions is reflected is because the refractive power is lower than the point at which the axial principal ray is reflected at the second face having only the reflecting action. For this reason, eccentric aberration generated by eccentricity on the first surface is basically small, and even if this surface is configured by a rotationally symmetric surface, eccentric aberration can be corrected by another surface.

The first surface 3 can be composed of a rotationally symmetric spherical surface or a rotationally symmetric aspheric surface. When the first surface 3 is composed of a rotationally symmetric aspheric surface, as shown in FIG. It is desirable that the following condition (0-1) be satisfied when the angle at which the optical axis 2 intersects with the rotation center axis 12 passing through 10 is satisfied in a well-balanced manner between eccentric aberration and chromatic aberration.

5 ° <α <30 ° (0-1) Here, when α exceeds the lower limit of 5 °, the inclination of the first surface 3 with respect to the optical axis 2 becomes too small. The eccentric aberration generated on the surface 4 cannot be corrected completely, and the first
The surface 3 must be constituted by a rotationally asymmetric surface. Conversely, when α exceeds the upper limit of 30 °, the first
Since the inclination of the surface 3 with respect to the optical axis 2 becomes too large, a large chromatic dispersion occurs in a light beam transmitted (incident or emitted) through the first surface 3, thereby deteriorating the optical performance.

In the calculation of α, the rotation center axis 12 of the rotationally symmetric surface is taken along the YZ section of the center 10 (the section in FIG. 1).
The definition of the coordinate system will be described later. ) May be obtained by the normal from the tangent 11 in the parentheses. When the first surface 3 is constituted by a rotationally symmetric spherical surface, the center 10 exists innumerably on the first surface 3, and in this case, α is an axial main axis traveling on the optical axis 2. The point 13 at which the light ray is internally reflected by the first surface 3 is defined as the center 10, and the angle at which the rotation center axis 12 and the optical axis 2 passing through the point 13 intersect is α (α in the following embodiment is a condition (It is the same as α in (0-1).)

Further, the above α is desirably satisfying the following condition (0-2) in order to form a decentered prism optical system having better optical performance.

5 ° <α <25 ° (0-2) More preferably, the following condition (0-3) is satisfied. 10 ° <α <20 ° (0-3) Next, a coordinate system used in the following description will be described.

As shown in FIG. 1, an eccentric prism optical system 7
An axial principal ray passing through the center of the pupil 1 and reaching the center of the image plane 6 (image display element when used as an eyepiece optical system) exits the pupil 1 and intersects the first surface 3 of the eccentric prism optical system 7 (In the case of using as an eyepiece optical system, it becomes an observer's visual axis).
An axis perpendicular to the Z axis and within an eccentric plane of each surface constituting the eccentric prism optical system 7 is defined as a Y axis, and an axis orthogonal to the Z axis and orthogonal to the Y axis is defined as an X axis. . The center of the pupil 1 is set as the origin of this coordinate system. The direction in which the on-axis 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 located is the positive direction of the Y-axis, and the Y-axis and the Z-axis constitute a right-handed X The direction of the axis is defined as the positive direction of the X axis.

In general, it is difficult to manufacture the eccentric prism optical system by polishing, and it is necessary to form one surface at a time by grinding, or to manufacture by plastic injection molding or glass molding. At this time, it is necessary to confirm whether the surface of the decentered prism optical system is formed in a predetermined shape. A three-dimensional coordinate measuring device is generally used for measuring such a three-dimensional rotationally asymmetric shape, but it takes a long measurement time and is not practical.

In the present invention, it is important that at least one of the at least three surfaces constituting the decentered prism optical system be a rotationally symmetric surface.

More preferably, the effective area is widest,
By configuring the first surface 3 having a transmission function and an internal reflection function on the side close to the pupil where the aberration is relatively deteriorated as a rotationally symmetric surface, it is possible to easily evaluate the finished state of the surface shape in a short time. A successful decentered prism optical system has been successfully constructed.

The decentered prism optical system of the present invention will be described as an image forming optical system. It should be noted that, naturally, the object point and the image point are arranged in reverse (the image display element is arranged on the image plane 6 in FIG. 1 and the pupil of the observer is located on the pupil 1), and can be used as the eyepiece optical system. Needless to say. Of course, an image display element may be arranged on the pupil 1 side, and an image of this image display element may be observed from the image plane 6 side.

When the X-axis, Y-axis, and Z-axis are determined according to the above definitions, the center of the pupil position is emitted, and among the principal rays incident on the image plane, the angle of view in the X direction is zero, the maximum angle of view in the X direction, The maximum angle of view in the positive direction, the angle of view in the Y direction is zero, the maximum angle of view in the Y negative direction is the X direction,
Six principal rays are determined by the combination in the Y direction as shown in Table 1 below.

[0024]

That is, as described in Table 1 above, the axial principal ray at the center of the screen is defined as,
The principal ray passing through the Y positive direction maximum angle of view is defined as the X direction angle of view zero,
The principal ray passing through the Y negative direction maximum angle of view is converted into the X direction maximum angle of view,
The principal ray passing through the Y positive direction maximum angle of view is converted into the X direction maximum angle of view,
The principal ray passing through the zero angle of view in the Y direction is defined as the maximum angle of view in the X direction, Y
Let the principal ray pass through the maximum angle of view in the negative direction. An area in which these principal rays intersect each surface is defined as an effective area, and an expression defining the shape of each surface in the effective area (an expression expressing the Z axis as an axis of the surface, or an eccentricity of the surface Not as
Z = f (X, Y)) In-plane curvature including the normal of the surface at a position where each of the principal rays 〜 hits the surface in a direction parallel to the Y-axis corresponding to the eccentric direction of the surface. To Cy1
Let it be Cy6. In addition, curvatures in a plane including a normal to a plane in the X-axis direction orthogonal to the Y-axis are defined as Cx1 to Cx6.

First, a conditional expression relating to the focal length of the second surface having only a reflecting effect on the entire optical system of the present invention will be described. The second surface having only the reflection function of the present invention is eccentric, and its shape is a rotationally asymmetric surface shape having no rotationally symmetric axis both in-plane and out-of-plane. Since it is meaningless to derive the focal length, the focal length is defined as:

A minute amount H (m) in the X-axis direction from the center of the pupil in parallel with the axial principal ray passing from the center of the object point to the center of the entrance pupil of the optical system.
m), the NA of the emitted light (the value of the sin of the angle formed with the on-axis principal ray) when the ray incident on the optical system in parallel with the on-axis principal ray is traced by the above H. The value is defined as the focal length Fx (mm) in the X direction of the entire optical system. Also, the exit ray NA (the sin of the angle formed with the on-axis principal ray) when the ray passing through the point of H (mm) in the Y direction from the pupil center and entering the optical system in parallel with the on-axis principal ray is traced. Is defined as the focal length Fy (mm) of the entire optical system in the Y direction.

Assuming that Fx / Fy is FA using Fx and Fy, it is important to satisfy the following conditional expression: 0.7 <FA <1.3 (A-1).

This condition relates to the aspect ratio of the image.
If the lower limit of 0.7 is exceeded, the image in the X direction will be small, and if a square is formed, the image will be vertically long. If the upper limit of 1.3 is exceeded, the image will be horizontally long. Naturally, the FA value is most preferably 1. However, in order to correct the image distortion, it is important to perform the correction 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, it is important to satisfy the following condition: 0.8 <FA <1.2 (A-2)

Next, the refracting powers (powers) Pxn and Pyn in the X and Y directions of the surface at the position where the axial chief ray passing through the center of the pupil and passing through the center of the pupil hits the second surface having only the reflecting action.
And the focal lengths Fx and Fy in the X and Y directions of the entire optical system.
The relationship with the refraction power (power) Px, Py, which is the reciprocal of
When 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 one of the following conditions.

When the lower limit of 0.8 of these conditions is exceeded,
The power of the second reflecting surface, which has only a reflecting action in both the X and Y directions, is too small compared to the power of the entire optical system, causing the other surfaces to bear the power, which is not preferable for aberration correction. .

If the upper limit of 1.3 is exceeded, the second
The power of the reflecting surface of the surface becomes too strong, and it becomes impossible to correct the image distortion and the field curvature occurring on the second surface in a well-balanced manner. More preferably, conditional expression (B-
It is preferable that both 1) and (C-1) be satisfied.

Next, the condition of the surface curvature at the position corresponding to the second surface having only the reflecting action will be described. This condition is a condition necessary for reducing astigmatism generated on the second surface. The X-direction curvature Cx2 including the normal of the second surface and the Y-direction curvature Cx2 at the position where the axial principal ray falls. When the ratio Cx2 / Cy2 of the curvature Cy2 is CxyD, it is important to satisfy the following condition: 0.8 <CxyD <1.2 (D-1).

The second surface having only the reflecting function is a surface arranged eccentrically. If this surface is constituted by a rotationally symmetric surface, large astigmatism, coma, etc., including image distortion, occur. It is impossible to satisfactorily correct aberrations.
For this reason, it is important to form the second surface having only the reflection function as a rotationally asymmetric surface. However, if the second surface has a rotationally symmetric surface, astigmatism occurring on this surface increases, and It becomes impossible to correct in terms of Therefore, in order to correct them, a second surface having only a reflection function is constituted by a surface having only one symmetric surface, and the above condition (D-1) is satisfied. It is possible to obtain an image free of astigmatism and to observe an observation image even on the axis, in which aberration is well corrected. The lower limit of 0.8 and the upper limit of 1.2 are limits at which astigmatism does not significantly occur.

More preferably, it is important to satisfy the following condition: 0.95 <CxyD <1.1 (D-2)

More preferably, it is important to satisfy the following condition: 1 <CxyD <1.05 (D-3)

Next, since the second surface having only the reflecting action causes different aberrations at each image position, it is necessary to correct the aberrations by changing the shape of the reflecting surface. It depends slightly on the location of the reflecting surface, and it is important to satisfy the following conditional expression.

The second in which the axial chief ray has only a reflecting action
The curvature in the X direction at the time of reflection on the surface is Cx2, and the difference between the maximum principal ray of the angle of view, the curvature Cxn in the X direction (n is 1, 3 to 6) of the effective area where each surface 〜 hits each surface is Cxn-Cx2.
Divided by the power Px in the X direction of the entire optical system (Cxn
Of Cx2) / Px, the largest one is CxMaxE, the smallest one is CxMinE, and similarly the curvature Cyn in the Y direction.
The value obtained by dividing Cy2 by the power Py in the Y direction of the optical system (Cy
Among n-Cy2) / Py, the largest one is CyMaxF,
If the smallest one is CyMinF, −0.05 <CxMinE (1 / mm) (E-1) CxMaxE <0.05 (1 / mm) (E-1 ′) −0.1 <CyMinF (1 / mm) (F-1) CyMaxF <0.1 (1 / mm) (F-1 ′) Conditional expressions (E-1) and (E-1 ′) Or (F-
It is preferable to satisfy either one of (1) and (F-1 ′) for aberration correction.

If the lower limits of the conditional expressions (E-1) and (F-1) and the upper limits of (E-1 ') and (F-1') are exceeded, the curvatures of the surfaces in the effective area are greatly different. However, the curvature of the entire effective area of the second surface having the strongest refracting power in the optical system is greatly changed, and it is impossible to obtain a wide flat image over the entire angle of view or to observe the observation image. Would.

More preferably, -0.03 <CxMinE (1 / mm) (E-2) CxMaxE <0.015 (1 / mm) (E-2 ') -0.08 < CyMinF (1 / mm) (F-2) CyMaxF <0.07 (1 / mm) (F-2 ′) Satisfying all of the following conditional expressions requires that the angle of view exceeds 30 °. When it comes to importance. More preferably, it is preferable to satisfy both of the above conditional expressions at the same time.

Next, the difference between the upper and lower effective areas of the curvature of the second surface in the Y direction, that is, Cy1-Cy3 divided by Py, is Cy.
When G, it is important to satisfy the following condition: -0.05 <CyG <0.5 (G-1) This condition is a condition necessary for satisfactorily correcting image distortion in the vertical direction above and below the image plane. If the lower limit of -0.05 is exceeded, the magnification below the screen becomes small, and the upper limit of 0 is set. If it exceeds 0.5, the magnification in the Y (up / down) direction on the screen will be smaller than that of other parts of the screen, and the image will be distorted. Especially,
In the decentered prism optical system in which the first surface having the reflection function and the transmission function as the present invention has a rotationally symmetric surface and the manufacturability is improved, in order to correct this image distortion on another surface,
Unless the correction is made on the third surface having only the transmission function closest to the image, the above-described image distortion cannot be corrected basically. However, since the third surface having only the transmission function mainly corrects the field curvature, if the second surface having only the reflection function does not satisfy this condition, the field curvature and the image distortion as a whole of the optical system are caused. Cannot be corrected at the same time.

More preferably, it is preferable to satisfy the following condition: 0 <CyG <0.2 (G-2) for aberration correction.

More preferably, it is preferable to satisfy the following condition: 0 <CyG <0.15 (G-3) for aberration correction.

Next, the value obtained by dividing the difference Cx1-Cx3 between the upper and lower effective areas of the curvature in the X direction of the second surface by Px to CxH
It is important to satisfy the following condition: -0.01 <CxH <0.1 (H-1) This condition is also a condition necessary for satisfactorily correcting the image distortion in the horizontal direction above and below the image plane. If the lower limit of -0.01 is exceeded, the magnification below the screen becomes small, and the upper limit of 0. If it exceeds 1, the magnification in the X (left / right) direction on the screen becomes smaller than that of other parts of the screen, and the image is distorted into a trapezoid.

More preferably, it is preferable to satisfy the following condition: 0 <CxH <0.05 (H-2) from the viewpoint of aberration correction.

It is more preferable to satisfy the following condition: 0.01 <CxH <0.05 (H-3) for aberration correction.

Next, it is important that the third surface having only the transmission function, which is disposed to face the image plane, satisfies the following conditions. Coordinates defining a third surface having only a transmissive action (the Z axis is the axis of the surface, and the surface is Z = f (X, Y)
When the positive direction of the Y-axis of the coordinates in the form of () is taken in the direction approaching the pupil, the Y-direction curvature in the negative Y-axis direction is larger in the negative direction than the Y-direction curvature in the Y-axis positive direction. Is preferred.

When the curvature in the Y direction of the portion where the principal ray with the angle of view of the third surface passes through the third surface is Cy1, Cy3, the value obtained by dividing Cy1-Cy3 by Py is CyI.
In this case, it is preferable from the viewpoint of aberration correction that the following conditional expression is satisfied: 0 <CyI <5 (I-1)

In an optical system in which the decentered reflecting surface has the main power of the optical system as in the present invention, image distortion due to eccentricity occurs. However, correction of this image distortion does not greatly affect aberration. Is effective on the third surface. In the above conditional expression, when CyI exceeds the lower limit of 0, the curvature of the Y axis in the negative direction of the Y axis in the negative direction of the Y axis does not increase in the negative direction as compared with the curvature of the positive Y direction. It becomes impossible to balance and correct image distortion in the vertical direction of the screen generated on two surfaces. On the other hand, when the value exceeds the upper limit of 5, good results cannot be obtained for image distortion in the vertical direction, and image distortion due to eccentricity cannot be completely corrected.

More preferably, the following condition is satisfied: 0 <CyI <2 (I-2)

Next, when the positive direction of the Y-axis of the coordinates defining the third surface having only the transmissive action is taken in the direction approaching the pupil, Y
Preferably, the X-direction curvature in the negative Y-axis direction is greater in the negative direction than the X-direction curvature in the positive axis direction.

Further, when the curvature in the X direction of the portion where the principal ray with the angle of view of the third surface passes through the third surface is Cx1 and Cx3, the value obtained by dividing Cx1−Cx3 by Px is CxJ.
In this case, it is preferable from the viewpoint of aberration correction that the following conditional expression is satisfied: 0 <CxJ <1 (J-1)

In the above conditional expression, when CxJ exceeds the lower limit of 0, the curvature of the Y axis in the negative direction of the Y axis does not increase in the negative direction as compared with the curvature of the positive X direction. This makes it impossible to balance and correct trapezoidal image distortion generated on the second surface. If the upper limit of 1 is exceeded, similarly, good results cannot be obtained for trapezoidal image distortion, and it becomes impossible to correct image distortion due to eccentricity.

It is more preferable that the following condition is satisfied: 0 <CxJ <0.3 (J-2)

Now, from the above conditions (0-1) to (J-
Regarding 2), the first surface having the reflecting action and the transmitting action is constituted by a rotationally symmetric surface, and the second face having only the reflecting action is defined as having no rotationally symmetric axis both in-plane and out-of-plane. It is preferable to configure a plane symmetric free-form surface having only one. Furthermore, not only a plane-symmetric free-form surface but also an anamorphic surface having no rotational symmetry axis both in-plane and out-of-plane, that is, a rotation having no rotational symmetry axis in-plane and out-of-plane. The present invention can be applied to any case having an asymmetric surface shape.

[0057]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments 1 to 4 of the decentered prism optical system according to the present invention will be described below. In the configuration parameters of each embodiment to be described later, as shown in FIG. 1, a light ray passing from the center of the pupil 1 of the optical system 7 to the origin of the optical system and passing the optical axis 2 from the center of the object to the center of the pupil 1 (origin). The direction from the pupil 1 to the optical axis 2 is the Z-axis direction, the direction in the plane perpendicular to the Z-axis and passing through the center of the pupil 1 and where the light beam is bent by the optical system 7 is the Y-axis direction, the Y-axis direction, The direction orthogonal 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 7 is the positive direction of the Z axis, the direction from the optical axis 2 to the image plane 6 is the positive direction of the Y axis, The direction forming the right-handed system with these Y axis and Z axis is defined as the positive direction of the X axis. Note that the ray tracing is a direction in which the light enters the optical system 7 from the object side of the optical system 7 on the pupil 1 side.

For a surface having eccentricity, the eccentricity in the X-axis direction, the Y-axis direction, and the Z-axis direction from the center of the pupil 1 which is the origin of the optical system 7 at the top of the surface is determined. The inclination angles (α, β, and γ) of the central axis of the surface (the Z axis of the following equation (b) for the free-form surface) around the X, Y, and Z axes are given. ing. In this case, the positive α and β mean counterclockwise in the positive direction of each axis, and the positive γ means clockwise in the positive direction of the Z axis. In addition, the radius of curvature of the spherical surface, the spacing between the surfaces, the refractive index of the medium, and the Abbe number are given according to conventional methods.

The shape of the anamorphic surface 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 ] + {Rn} (1-Pn) X ² + (1 + P
n) Y ² ｝ ^{(n + 1)} Here, when n = 4 (fourth-order term) is considered as an example, when expanded, it can be expressed by the following equation (a).

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 (a) where Z is the amount of deviation from the tangent plane to the origin of the surface shape, Cx is the curvature in the X-axis direction, Cy is the curvature in the Y-axis direction, and Kx is X The axial conic coefficient, Ky is the Y-axial conic coefficient, Rn is the rotationally symmetric component of the aspherical term, and Pn is the rotationally asymmetrical component of the aspherical term. The X-axis curvature radius Rx, the Y-axis curvature radius Ry, and the curvatures Cx, Cy have a relationship of Rx = 1 / Cx, Ry = 1 / Cy.

The shape of the rotationally asymmetric surface is defined by the following equation. The Z axis of the definition formula is the axis of the rotationally asymmetric surface. Z = Σ _n Σ _m proviso C ^_nm X ⁿ Y _nm, ⁿ is 0~k of sigma _n is sigma, m of sigma _m is sigma is 0~n
Represents

When a plane-symmetric free-form surface (a rotationally asymmetric surface having only one plane of symmetry) is defined by an expression representing this rotationally asymmetric surface, when the symmetry caused by the plane of symmetry is determined in the X direction, , X to zero (eg, X
In order to determine the symmetry caused by the plane of symmetry in the Y direction, the odd-order term of Y may be set to 0 (for example, the coefficient of the Y-odd-order term may be set to 0).

Here, as an example, if k = 7 (seventh-order term), X
When a plane-symmetric free-form surface symmetrical in the direction is expressed in a form in which the above-described definition expression 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 ... (B) Then, the coefficients C ₄ , C ₆ , C _9.
(Examples described later). In the parameters of the configuration described later, a coefficient relating to an aspheric surface not described is 0.

Another definition of a plane-symmetric free-form surface is a Zernike polynomial. The shape of this surface is defined by the following equation (c). The Z axis of the definition formula is Zer
This is the axis of the Nike polynomial. X = R × cos (A) Y = R × sin (A) Z = D ₂ + D ₃ R cos (A) + D ₄ R sin (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) (c) In the above description, the plane is symmetric in the X direction. Here, D _m (m is an integer of 2 or more) is a coefficient.

As an expression example of another surface that can be used in the present invention, the above defined formula (Z = _{{n} m} C _nm X
ⁿ Y ^nm ), as in the case of equation (b),
In the case of representing a plane where k = 7, it can be expanded as in the following equation (d).

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 | (d) The shape of the rotationally symmetric aspherical surface is defined by the following equation. The Z axis in the definition formula is the axis of the 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) where Y is the direction perpendicular to Z, R is the paraxial radius of curvature, P is the conic coefficient, and A ₄ , A ₆ , A ₈ and A ₁₀ are the aspheric coefficients.

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

FIGS. 3 to 6 show Examples 1 to 4 respectively.
3 is a YZ sectional view including the optical axis 2 of the eccentric prism optical system 7 of FIG. The decentered prism optical system 7 of any of the embodiments has three surfaces 3, 4, and 5, as in the case of FIG. 1, and a transparent portion having a refractive index larger than 1 between the three surfaces 3 to 5. A light beam, which is buried in a medium and emitted from an object (not shown), first passes through a pupil 1 of an optical system 7 along an optical axis 2 and is incident on a first surface 3 having a transmitting action and a reflecting action. The incident light enters the system 7 and is reflected in a direction approaching the pupil 1 by the second surface 4, which is a reflecting surface having only a reflection function farther from the pupil 1, and then moves away from the pupil 1 by the first surface 3. Direction, the reflected light of which is reflected by a third surface 5 having only a transmissive action.
And reaches the image plane 6 to form an image. In Examples 1 to 3, the first surface 3 is a spherical surface eccentric with the concave surface facing the pupil 1 side, and in Example 4, the first surface 3 is eccentric with the concave surface facing the pupil 1 side. It is a rotationally symmetric aspheric surface defined by the above equation (e), and in each of the embodiments, the second surface 4 and the third surface 5 are composed of free-form surfaces defined by the above equation (b). . In addition, Examples 1 to 4 are
The horizontal angle of view is 37 °, the vertical angle of view is 27.6 °, and the pupil diameter is 4 mm. Hereinafter, the configuration parameters of Examples 1 to 4 will be described.

Example 1 Surface number Curvature radius Interval Eccentricity Refractive index Abbe number Object plane 面 ∞ 1 ∞ (pupil) 2 -167.559 Eccentricity (1) 1.4922 57.5 3 Free-form surface Eccentricity (2) 1.4922 57.5 4 -167.559 Eccentricity (1) 1.4922 57.5 5 Free-form surface Eccentricity (3) Image surface ∞ Eccentricity (4) Free-form surface C ₅ -8.2644 × 10 ^-3 C ₇ -8.9985 × 10 ^-3 C ₈ 3.7852 × 10 ^-5 C ₁₀ 1.3727 × 10 ^-5 C ₁₂ 3.4753 × 10 ^-8 C ₁₄ -3.2 511 × 10 ^-6 C ₁₆ -7.6369 × 10 ^-7 C ₁₇ 1.5767 × 10 ^-7 C ₁₉ -6.2172 × 10 ^-8 C ₂₁ 2.9 399 × 10 ^-8 C ₂₃ 5.8 293 × 10 ^{-9 _{C 25 4.0550 × 10 -9 C 27}} 1.7532 × 10 -9 C 29 -9.2932 × 10 -10 C 30 7.9948 × 10 -11 C 32 4.2710 × 10 -10 C 34 2.2002 × 10 -10 C 36 -1.1987 × 10 - ¹⁰ free-form surface C ₅ -2.4569 × 10 ^-2 C ₇ -9.2271 × 10 ^-3 C ₈ 1.8803 × 10 ^-3 C ₁₀ 9.0656 × 10 ^-4 C ₁₂ 5.3303 × 10 ^-5 C ₁₄ 1.8144 × 10 ^-4 C ₁₆ 8.6739 × 10 ^-6 C ₁₇ -1.1351 × 10 ^-5 C ₁₉ -1.6466 × 10 ^-5 C ₂₁ -9.3221 × 10 ^-7 XYZ Z α (°) β (°) γ (°) Eccentricity (1) 0.000 7.108 25.777 19.22 0.00
0.00 Eccentricity (2) 0.000 4.756 37.554 -8.06
0.00 0.00 Eccentricity (3) 0.000 19.525 30.305 86.90 0.00 0.00 Eccentricity (4) 0.000 23.309 33.150 61.64 0.00 0.00.

Example 2 Surface number Curvature radius Interval Eccentricity Refractive index Abbe number Object plane 数 ∞ 1 ∞ (pupil) 2 -109.365 Eccentricity (1) 1.4922 57.5 3 Free-form surface Eccentricity (2) 1.4922 57.5 4 -109.365 Eccentricity (1) 1.4922 57.5 5 Free-form surface Eccentricity (3) Image surface ∞ Eccentricity (4) Free-form surface C ₅ -1.0133 × 10 ^-2 C ₇ -1.0025 × 10 ^-2 C ₈ 5.6608 × 10 ^-5 C ₁₀ 2.5415 × 10 ^-5 C _{12 ^{-2.1481 × 10 -6 C 14 -3.4315 ×}} 10 -6 C 16 -1.3836 × 10 -6 C 17 -4.1483 × 10 -8 C 19 6.6703 × 10 -8 C 21 3.5615 × 10 -8 C 23 8.7397 × 10 - ^{_{9 C 25 -1.2505 × 10 -8 C}} 27 -4.5501 × 10 -10 C 29 2.6484 × 10 -10 C 30 -1.9631 × 10 -10 C 32 4.6259 × 10 -10 C 34 -4.9439 × 10 -12 C 36 - 1.1870 × 10 ^-10 Free-form surface C ₅ -1.6101 × 10 ^-2 C ₇ 8.9 510 × 10 ^-3 C ₈ -2.3326 × 10 ^-3 C ₁₀ -7.6454 × 10 ^-5 C ₁₂ -1.8499 × 10 ^-4 C ₁₄ -5.5035 × 10 ^-4 C ₁₆ 2.0491 × 10 ^-5 C ₁₉ -3.6151 × 10 ^-5 C ₂₁ 1.5782 × 10 ^-6 XYZ Zα (°) β (°) γ (°) Eccentricity (1) 0.000 7.977 25.617 14.61 0.00 0.00 Eccentricity (2) 0.000 -2.742 35.5 28 -19.28 0.00 0.00 Eccentricity (3) 0.000 19.605 22.719 93.54 0.00 0.00 Eccentricity (4) 0.000 22.522 33.564 58.60 0.00 0.00.

Example 3 Surface number Curvature radius Interval Eccentricity Refractive index Abbe number Object plane 面 ∞ 1 ∞ (pupil) 2 -131.243 Eccentricity (1) 1.4922 57.5 3 Free-form surface Eccentricity (2) 1.4922 57.5 4 -131.243 Eccentricity (1) 1.4922 57.5 5 Free-form surface Eccentricity (3) Image surface ∞ Eccentricity (4) Free-form surface C ₅ -8.9284 × 10 ^-3 C ₇ -9.2053 × 10 ^-3 C ₈ 3.8229 × 10 ^-5 C ₁₀ 4.2262 × 10 ^-5 C ₁₂ -7.2223 × 10 ^-7 C ₁₄ -1.3031 × 10 ^-6 C ₁₆ -1.9520 × 10 ^-6 C ₁₇ 1.1271 × 10 ^-7 C ₁₉ -3.6870 × 10 ^-8 C ₂₁ -1.1768 × 10 ^-7 C ₂₃ 1.6276 × 10 ^-9 C ₂₅ -6.7166 × 10 ^-9 C ₂₇ -7.7763 × 10 ^-9 C ₂₉ 3.4606 × 10 ^-9 C ₃₀ -2.4515 × 10 ^-10 C ₃₂ 2.9077 × 10 ^-10 C ₃₄ -1.8189 × 10 ^-10 C ₃₆ -1.8698 × 10 ^-10 free curved surface ^{_{C 5 -4.9779 × 10 -3 C 7}} -1.7671 × 10 -2 C 8 -7.3015 × 10 -4 C 10 2.7601 × 10 -3 C 12 -1.6689 × 10 -4 C 14 - _{^{3.4904 × 10 -4 C 16 2.3877 ×}} 10 -4 C 19 -2.6265 × 10 -5 C 21 -1.7550 × 10 -5 C 25 -4.7065 × 10 -7 C 27 3.7320 × 10 -6 C 29 -1.1090 × 10 - ⁶ C ₃₂ -1.0 260 × 10 ^-7 C ₃₄ 2.4355 × 10 ^-7 C ₃₆ 1. 6830 × 10 ^-7 XYZ α (°) β (°) γ (°) Eccentricity (1) 0.000 8.065 25.582 15.00 0.00 0.00 Eccentricity (2) 0.000 1.394 37.156 -13.88 0.00 0.00 Eccentricity (3) 0.000 20.169 24.811 92.24 0.00 0.00 Eccentricity (4) 0.000 23.024 33.868 57.68 0.00 0.00.

Example 4 Surface Number Curvature Radius Interval Eccentricity Refractive Index Abbe Number Object Surface ∞ ∞ 1 ∞ (pupil) 2 -121.590 (aspherical surface) Eccentricity (1) 1.4922 57.5 3 Free-form surface Eccentricity (2) 1.4922 57.5 4 -121.590 (aspherical) eccentric (1) 1.4922 57.5 5 free curved eccentric (3) image surface ∞ eccentricity (4) aspheric coefficient surface _{number: 2,4 P = 1 A 4 =} -0.47078 × 10 -5 A 6 = 0.91622 × 10 ^-8 A ₈ = 0.14049 × 10 ^-10 A ₁₀ = -0.31035 × 10 ^-13 Free-form surface C ₅ -9.8116 × 10 ^-3 C ₇ -9.9228 × 10 ^-3 C ₈ 3.0681 × 10 ^-5 C ₁₀ 4.5462 × 10 ^-5 C ₁₂ -3.8345 × 10 ^-6 C ₁₄ -4.1008 × 10 ^-6 C ₁₆ -4.6317 × 10 ^-6 C ₁₇ 2.1625 × 10 ^-7 C ₁₉ 1.6597 × 10 ^-7 C ₂₁ -1.6454 × 10 ^-7 C ₂₃ 1.0751 × 10 ^-8 C ₂₅ 4.0 250 × 10 ^-9 C ₂₇ 3.4501 × 10 ^-9 C ₂₉ 8.6 519 × 10 ^-9 C ₃₀ -5.3805 × 10 ^-10 C ₃₂ -1.0139 × 10 ^-9 C ₃₄ -5.5962 × 10 ^-10 C ₃₆ 2.7231 × 10 ^-10 Free-form surface C ₅ -4.7478 × 10 ^-2 C ₇ -1.8423 × 10 ^-2 C ₈ -5.2664 × 10 ^-3 C ₁₀ 5.1605 × 10 ^-4 C ₁₂ -2.4447 × 10 ^-4 C ₁₄ -5.4622 × 10 ^-4 C ₁₆ 4.748 2 × 10 ^-4 C ₁₉ -1.2 350 × 10 ^-4 C ₂₁ -2.0 224 × 10 ^-5 C ₂₅ -1.1895 × 10 ^-5 C ₂₇ 3.5 172 × 10 ^-7 C ₂₉ -2.4403 × 10 ^-6 C ₃₂ -3.8988 × 10 ^-7 C ₃₄ -1.1605 × 10 ^-8 C ₃₆ 2.3716 × 10 ^-7 XYZ α (°) β (°) γ (°) Eccentricity (1) 0.000 7.771 25.658 15.00 0.00 0.00 Eccentricity (2) 0.000 1.049 36.261- 14.93 0.00 0.00 Eccentricity (3) 0.000 19.049 21.405 98.38 0.00 0.00 Eccentricity (4) 0.000 22.022 33.091 59.19 0.00 0.00.

FIGS. 7 to 10 show aberration diagrams representing image distortions in the above-described first to fourth embodiments. In these aberration diagrams, the vertical axis represents the image height in the X direction, and the horizontal axis represents the image height in the Y direction. FIGS. 11 to 13 show spot diagrams showing the aberration correction state of the first embodiment. In these figures, among the four numbers on the left side of the spot diagram, the upper two numbers indicate coordinates (X, Y) of the center of the rectangular screen at (0.00, 0.00).
0.00), and the coordinates at the center of the right end are (0, 00, -1.0).
0), coordinates (X, Y) when the coordinates of the upper right corner are expressed as (1.00, -1.00) and the coordinates of the center of the upper end are expressed as (1.00, 0.00). Indicate the X component and the Y component (degree display) of the angle (angle of view) formed by the above-mentioned coordinate (X, Y) direction with respect to the optical axis (center of the screen).

Next, the conditional expressions (0)
-1) to (J-1) are shown.

The eccentric prism optical system of the present invention as described above can be used for an image display device. As an example, FIG. 14 shows a state in which the head-mounted image display device is mounted on the observer's head, and FIG. 15 is a cross-sectional view thereof. This configuration uses the decentered prism optical system of the present invention as the eyepiece optical system 100 as shown in FIG.
By preparing a pair consisting of 0 and the image display element 101 on the left and right, and supporting them at a distance of the eye 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.

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 the image display element 1 comprising a liquid crystal display element on the image plane corresponding to them.
01 is arranged. Then, as shown in FIG. 14, the display device main body 102 is provided with a temporal frame 103 as shown in the figure continuously on the left and right, so that the display device main body 102 can be held in front of the observer. .

The speaker 1 is provided on the temporal frame 103.
04 is provided so that stereophonic sound can be heard together with image observation. Thus, the speaker 1
Since the playback device 106 such as a portable video cassette is connected to the display device main body 102 having the video signal 04 via the video / audio transmission code 105, the observer can attach the playback device 106 to an arbitrary portion such as a belt as shown in the figure. , So that the user can enjoy video and audio. Reference numeral 107 in FIG.
This is an adjustment unit for adjusting the volume and the like. The display device body 10
2, electronic components such as a video processing circuit and an audio processing circuit are incorporated.

The cord 105 may have a jack at the tip so that it can be attached to an existing video deck or the like. Furthermore, it is connected to a tuner for TV radio wave reception,
It may be used for viewing, or may be connected to a computer to receive computer graphics images, message images from the computer, and the like. Also, in order to reject an obstructive code, an antenna may be connected to receive an external signal by radio waves.
Further, the decentered prism optical system of the present invention may be used in a head mounted image display device for one eye in which an eyepiece optical system is disposed in front of one of the left and right eyes.

The eccentric prism optical system of the present invention can also be used for a photographing optical device and an observation optical device. As an example, there is a use in a camera having a photographing optical system and a finder optical system as shown in FIG. First, as shown in the optical path diagram in FIG. 17, the decentered prism optical system of the present invention is formed as a rear group 153 of an objective lens 150 including a front group 151 and a rear group 153 with a pupil position (aperture or virtual diaphragm position) 152 interposed therebetween. Deploy. By doing so, the film 154, which can be arranged only perpendicularly to the optical axis Lb in the conventional photographing optical system, can be arranged obliquely 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 be used for an electronic camera. Next, FIG.
As shown in FIG. 8, 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 finder optical system. Is guided to the observer's eyeball 205 by the eyepiece 204. With this configuration, the height direction can be made lower than that of the conventional Porro prism, and compactness can be achieved. In the drawing, Le is the optical axis of the finder optical system.

Further, an objective lens of a rigid endoscope that transmits an image to an eyepiece using a relay lens, an objective lens of a flexible endoscope that transmits an image to the eyepiece using an optical fiber bundle, and a CCD. It can also be used for an objective lens of an electronic endoscope that receives an image. One example is shown in FIGS.
0 is shown. FIG. 19 shows a rigid endoscope (a so-called rigid endoscope).
FIG. 1 is an overall configuration diagram of an endoscope apparatus that uses an electronic device. An endoscope device 30 shown in FIG. 19 includes an endoscope 20 having an insertion section 22 in which an objective lens and an illumination optical system are provided, a camera 24, a monitor 25, and a light source device 27. Endoscope 20
As shown in FIG. 20, an objective lens 32 using an eccentric prism optical system 31 of the present invention and a light guide 33 for irradiating the visual field direction are incorporated in the distal end portion 21 of the insertion portion 22 as shown in FIG. . Following the objective lens 32, the insertion section 22 is provided with a relay lens system that is a transmission optical system for an image and a pupil. An eyepiece optical system (not shown) is arranged at the base 23 of the endoscope 20, and after the connection optical system,
It is possible to attach a camera 24 as an imaging means. 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 on the monitor 25 as an endoscope image so as to be observable to an observer. The light source device 27
Illuminates the viewing direction through the light guide cable 26, the base 23, the insertion section 22 and the tip 21.

The above-described decentered prism optical system of the present invention can be constituted, for example, as follows. [1] In an eccentric prism optical system having a configuration in which at least three surfaces are eccentrically arranged with respect to 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 optical system is at least twice. At least two of the three surfaces are formed as surfaces having a reflection effect so as to perform internal reflection of light, and light rays reflected by the two surfaces having a reflection effect are formed inside the optical system. Arrange the two surfaces having the above-mentioned reflective action at a position where it turns back,
Among the two surfaces having the reflecting action, the shape of one surface is formed as a rotationally asymmetric surface having no rotationally symmetric axis both in-plane and out-of-plane. The shape of the area where the light beam is transmitted and / or reflected in the entire area) is constituted by a rotationally symmetric aspherical surface having a rotationally symmetric axis in the effective plane, and the symmetrical aspherical surface transmits the light beam passing through the optical system. It is formed as a first surface having both a transmitting action for entering or emitting and a reflecting action for bending the light beam inside the optical system, and the rotationally asymmetric face is formed as a second face opposed to the first face, and further, A third surface having a transmission function of emitting or entering a light beam passing through the optical system is disposed at a position substantially perpendicular to a direction in which the first surface and the second surface face each other, and The first surface is in the direction of the second surface Configured shape with its surface, decentered prism optical system satisfies the following conditions. 5 ° <α <30 ° (0-1) where α is the rotation center axis of the rotationally symmetric aspheric surface of the first surface that reaches the image plane center through the center of the pupil of the optical system. This is the angle at which the on-axis principal ray intersects with the straight line from the exit of the pupil to the intersection with the first surface (the inclination angle of the surface).

[2] An eccentric prism optical system having a configuration in which at least three surfaces are arranged eccentrically to each other and a space between the three surfaces is filled with a transparent medium having a refractive index of 1.3 or more. At least two of the three surfaces are formed of reflective surfaces so as to perform at least two internal reflections, and the light reflected by the two reflective surfaces is reflected by the optical surface. The two surfaces having the reflecting action are arranged at such a position as to be turned back in the system. Among the two surfaces having the reflecting action, the shape of one face has a rotational symmetry axis both in-plane and out-of-plane. A rotationally asymmetric surface which is formed of no rotationally asymmetric surface and at least the effective surface of another surface (the region through which light flux is transmitted and / or reflected in the entire surface) has a rotational symmetry axis in the effective surface Consists of a spherical surface, front The first symmetrical spherical surface has both a transmitting function of causing a light beam passing through the optical system to enter or exit and a reflecting function of bending the light beam inside the optical system.
A third surface having a transmission function of emitting or entering a light beam passing through the optical system, wherein the rotationally asymmetric surface is formed as a second surface facing the first surface. The first surface is disposed at a position substantially perpendicular to the direction in which the first surface faces the second surface, and the first surface
The surface is configured in a shape with a convex surface facing the direction of the second surface,
An eccentric prism optical system characterized by satisfying the following conditions. 5 ° <α <30 ° (0-1) where α is a point at which the axial principal ray reaching the center of the image plane through the center of the pupil of the optical system is reflected by the first surface. The angle at which the central axis of rotation of the passing symmetric sphere intersects with the straight line from the center of the pupil of the optical system to the axial principal ray reaching the center of the image plane exiting the pupil and intersecting the first surface ( Angle of inclination of the surface).

[3] In the decentered prism optical system according to the above [1] or [2], the first surface is formed such that its transmission function and reflection function overlap in at least a part of the effective plane. A decentered prism optical system, wherein at least a reflection action in a region where the transmission action and the reflection action in the effective surface of the first surface overlap with each other is based on a total reflection action.

[4] In the decentered prism optical system according to the above [1] or [2], the rotationally symmetric surface of the first surface is formed by an aspheric surface or a spherical surface facing a convex surface in the direction of the second surface. An eccentric prism optical system characterized by:

[5] Any one of the above [1] to [4]
3. The decentered prism optical system according to claim 1, wherein said second surface is formed by an anamorphic surface.

[6] In the decentered prism optical system according to the above [5], the rotational symmetry of the rotational symmetry plane of the first surface is included in at least one symmetry plane among the two symmetry planes of the anamorphic surface. The decentered prism optical system, wherein the first surface and the second surface are arranged so that an axis is positioned.

[7] Any one of the above [1] to [4]
3. The decentered prism optical system according to claim 1, wherein the second surface is formed by a rotationally asymmetric surface having only one symmetric surface.

[8] In the decentered prism optical system according to the above [7], the rotation symmetry axis of the first surface is located within the symmetry plane of the rotation asymmetric surface having only one symmetry plane. The decentered prism optical system, wherein the first surface and the second surface are arranged as described above.

[0091]

[9] Any one of the above [1] to [8]
In the decentered prism optical system according to the item, a light beam enters from the third surface, the incident light beam passes through the inside of the optical system, is reflected by the first surface, and a light beam reflected by the first surface is The first surface, the second surface, and the third surface are arranged such that the light beam reflected by the second surface and the light beam reflected by the second surface exits from the first surface. A decentered prism optical system.

[10] The above

[9] In the eccentric prism optical system according to [9], the third surface is arranged at a position where a light beam from a means for displaying an image is incident, and the first surface is used for observing a light beam emitted from the first surface. An eccentric prism optical system which is arranged at a position where it is guided to a subject's eyeball and is used for an image observation device which enables an image formed by the light beam to be observed.

[11] In the eccentric prism optical system according to any one of [1] to [8], a light beam enters from the first surface, and the incident light beam is reflected by the second surface. The first surface such that 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 inside of the optical system and exits from the third surface. A decentered prism optical system, wherein the second surface and the third surface are arranged.

[12] In the eccentric prism optical system according to the above [11], the first surface is arranged at a position where a light beam from an object is incident, and the third surface is emitted from the third surface. An eccentric prism optical system, which is used for an image observing device which is arranged at a position where a light beam is guided to an observer's eyeball and enables observation of an image formed by the light beam.

[13] In the decentered prism optical system according to the above [11], the first surface is arranged at a position where a light beam from an object is incident, and the third surface is emitted from the third surface. An eccentric prism optical system, which is used for a photographing optical device which is arranged at a position where a light beam is guided to a means for receiving an object image and which can photograph an object image formed by the light beam.

[14] In the decentered prism optical system according to any one of the above [1] to [8], an axial principal ray passing through the center of a pupil of the decentered prism optical system and reaching the center of an image plane is formed. An axis defined by a straight line from the exit of the pupil to the intersection with the first surface is defined as a Z axis, and an axis perpendicular to the Z axis and within an eccentric plane of each surface constituting the eccentric prism optical system is defined as a Y axis. And an axis orthogonal to the Z axis and orthogonal to the Y axis is defined as an X axis, wherein the following condition is satisfied. 0.7 <FA <1.3 (A-1) However, the light passes through a point of a small amount H in the X-axis direction from the pupil center in parallel with the axial principal ray and in parallel with the axial principal ray. NA of an emitted light ray when a light ray incident on the optical system is traced.
The value obtained by dividing (the value of the sine of the angle formed by the on-axis principal ray) by the above H is defined as the focal length Fx of the entire optical system in the X direction. The value obtained by dividing the NA of the exit ray (the value of the sin of the angle formed with the axial principal ray) when the ray incident on the optical system in parallel with the principal ray by the ray tracing is divided by the H is used in the Y direction of the entire optical system. The focal length is defined as Fy, and Fx / Fy is defined as FA.

[15] The above [1] to [8], [1]
4] The decentered prism optical system according to any one of
An axis defined by a straight line from the center of the pupil of the eccentric prism optical system to the axial principal ray reaching the center of the image plane exiting the pupil and intersecting the first surface is defined as a Z axis. When an axis perpendicular to the axis and within the eccentric plane of each surface constituting the eccentric prism optical system is defined as a Y axis, and an axis orthogonal to the Z axis and orthogonal to the Y axis is defined as an X axis, the following conditions are satisfied. An eccentric prism optical system characterized by satisfying the following. 0.8 <| PxB | <1.3 (B-1) However, the light passes through a point of a small amount H in the X-axis direction from the pupil center in parallel with the on-axis principal ray, and NA of the exit ray when the ray incident on the optical system is traced in parallel
The value obtained by dividing (the value of the sine of the angle formed by the on-axis principal ray) by the above H is defined as the focal length Fx of the entire optical system in the X direction. The value obtained by dividing the NA of the exit ray (the value of the sin of the angle formed with the axial principal ray) when the ray incident on the optical system in parallel with the principal ray by the ray tracing is divided by the H is used in the Y direction of the entire optical system. The focal length Fy is defined as the refractive power (power) in the X and Y directions of the surface at the position where the axial principal ray hits the second surface, respectively, Px
n and Pyn, 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, and Pxn
/ Px is set to PxB.

[16] The above [1] to [8], [1]
4] The decentered prism optical system according to any one of
An axis defined by a straight line from the center of the pupil of the eccentric prism optical system to the axial principal ray reaching the center of the image plane exiting the pupil and intersecting the first surface is defined as a Z axis. When an axis perpendicular to the axis and within the eccentric plane of each surface constituting the eccentric prism optical system is defined as a Y axis, and an axis orthogonal to the Z axis and orthogonal to the Y axis is defined as an X axis, the following conditions are satisfied. An eccentric prism optical system characterized by satisfying the following. 0.8 <| PyC | <1.3 (C-1) However, the light passes through a point of a small amount H in the X-axis direction from the pupil center in parallel with the on-axis principal ray. NA of the exit ray when the ray incident on the optical system is traced in parallel
The value obtained by dividing (the value of the sine of the angle formed by the on-axis principal ray) by the above H is defined as the focal length Fx of the entire optical system in the X direction. The value obtained by dividing the NA of the exit ray (the value of the sin of the angle formed with the axial principal ray) when the ray incident on the optical system in parallel with the principal ray by the ray tracing is divided by the H is used in the Y direction of the entire optical system. The focal length Fy is defined as the refractive power (power) in the X and Y directions of the surface at the position where the axial principal ray hits the second surface, respectively, Px
n and Pyn, 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, and Pyn
/ Py is PyC.

[17] The above [1] to [8], [1]
The decentered prism optical system according to any one of [4] to [16], wherein an axial principal ray passing through the center of the pupil of the decentered prism optical system and reaching the center of the image plane exits the pupil and the first surface An axis defined by a straight line that intersects with the axis is defined as a Z-axis, an axis orthogonal to the Z-axis and within the eccentric plane of each surface constituting the eccentric prism optical system is defined as a Y-axis, and orthogonal to the Z-axis. And an axis orthogonal to the Y axis is defined as an X axis, wherein the following condition is satisfied. 0.8 <CxyD <1.2 (D-1) Here, the curvature Cx2 in the X direction including the normal of the surface at the position where the axial principal ray hits the second surface, and the curvature in the Y direction The ratio Cx2 / Cy2 to Cy2 is defined as CxyD.

[18] [1] to [8], [1]
In the decentered prism optical system according to any one of [4] to [17], an axial principal ray passing through the center of a pupil of the decentered prism optical system and reaching the center of an image plane exits the pupil, and the first surface An axis defined by a straight line that intersects with the axis is defined as a Z-axis, an axis orthogonal to the Z-axis and within the eccentric plane of each surface constituting the eccentric prism optical system is defined as a Y-axis, and orthogonal to the Z-axis. And an axis orthogonal to the Y axis is defined as an X axis, wherein the following condition is satisfied. −0.05 <CxMinE (1 / mm) (E-1) CxMaxE <0.05 (1 / mm) (E-1 ′) However, the pupil center is parallel to the axial principal ray. Of the exit ray when a ray passing through the point of the minute amount H in the X-axis direction and entering the optical system in parallel with the axial principal ray is traced.
The value obtained by dividing (the value of the sine of the angle formed by the on-axis principal ray) by the above H is defined as the focal length Fx of the entire optical system in the X direction. The value obtained by dividing the NA of the exit ray (the value of the sin of the angle formed with the axial principal ray) when the ray incident on the optical system in parallel with the principal ray by the ray tracing is divided by the H is used in the Y direction of the entire optical system. The focal length Fy is defined as the focal length Fx in the X direction and the focal length F in the Y direction.
The reciprocals of y are Px and Py, respectively, and a curvature Cx2 in the X direction and a curvature Cy2 in the Y direction including the normal to the second surface at the position where the axial principal ray hits the second surface, and the angle of view in the X direction A chief ray passing through the maximum Y positive direction view angle at zero, a chief ray passing through the Y negative direction maximum view angle at zero X direction view angle, a principal ray passing through the Y positive direction maximum view angle at the X direction maximum view angle, and the X direction maximum. Y at angle of view
A principal ray passing through the zero direction angle of view, a principal ray passing through the maximum negative angle of view in the X direction at the maximum angle of view in the X direction, and a curvature Cxn in the X direction and a curvature Cyn in the Y direction of the effective area corresponding to the second surface, (Cx
n-Cx2) / Px, the largest one is CxMaxE,
The smallest one is CxMinE, (Cyn-Cy2) / Py
Among them, the largest one is CyMaxF and the smallest one is CyM
inF.

[19] The above [1] to [8], [1]
In the decentered prism optical system according to any one of [4] to [17], an axial principal ray passing through the center of a pupil of the decentered prism optical system and reaching the center of an image plane exits the pupil, and the first surface An axis defined by a straight line that intersects with the axis is defined as a Z-axis, an axis orthogonal to the Z-axis and within the eccentric plane of each surface constituting the eccentric prism optical system is defined as a Y-axis, and orthogonal to the Z-axis. And an axis orthogonal to the Y axis is defined as an X axis, wherein the following condition is satisfied. −0.1 <CyMinF (1 / mm) (F-1) CyMaxF <0.05 (1 / mm) (F-1 ′) However, the pupil center is parallel to the axial principal ray. Of the exit ray when a ray passing through the point of the minute amount H in the X-axis direction and entering the optical system in parallel with the axial principal ray is traced.
The value obtained by dividing (the value of the sine of the angle formed by the on-axis principal ray) by the above H is defined as the focal length Fx of the entire optical system in the X direction. The value obtained by dividing the NA of the exit ray (the value of the sin of the angle formed with the axial principal ray) when the ray incident on the optical system in parallel with the principal ray by the ray tracing is divided by the H is used in the Y direction of the entire optical system. The focal length Fy is defined as the focal length Fx in the X direction and the focal length F in the Y direction.
The reciprocals of y are Px and Py, respectively, and a curvature Cx2 in the X direction and a curvature Cy2 in the Y direction including the normal to the second surface at the position where the axial principal ray hits the second surface, and the angle of view in the X direction A chief ray passing through the maximum Y positive direction view angle at zero, a chief ray passing through the Y negative direction maximum view angle at zero X direction view angle, a principal ray passing through the Y positive direction maximum view angle at the X direction maximum view angle, and the X direction maximum. Y at angle of view
A principal ray passing through the zero direction angle of view, a principal ray passing through the maximum negative angle of view in the X direction at the maximum angle of view in the X direction, and a curvature Cxn in the X direction and a curvature Cyn in the Y direction of the effective area corresponding to the second surface, (Cx
n-Cx2) / Px, the largest one is CxMaxE,
The smallest one is CxMinE, (Cyn-Cy2) / Py
Among them, the largest one is CyMaxF and the smallest one is CyM
inF.

[20] The above [1] to [8], [1]
In the eccentric prism optical system according to any one of [4] to [19], an axial principal ray passing through the center of a pupil of the eccentric prism optical system and reaching the center of an image plane exits the pupil, and the first surface An axis defined by a straight line that intersects with the axis is defined as a Z-axis, an axis orthogonal to the Z-axis and within the eccentric plane of each surface constituting the eccentric prism optical system is defined as a Y-axis, and orthogonal to the Z-axis. And an axis orthogonal to the Y axis is defined as an X axis, wherein the following condition is satisfied. −0.05 <CyG <0.5 (G-1) However, the light passes through a point of a small amount H in the X-axis direction from the center of the pupil in parallel with the axial principal ray, and is parallel to the axial principal ray. The NA of the exit ray when the ray incident on the optical system is traced
The value obtained by dividing (the value of the sine of the angle formed by the on-axis principal ray) by the above H is defined as the focal length Fx of the entire optical system in the X direction. The value obtained by dividing the NA of the exit ray (the value of the sin of the angle formed with the axial principal ray) when the ray incident on the optical system in parallel with the principal ray by the ray tracing is divided by the H is used in the Y direction of the entire optical system. The focal length Fy is defined as the focal length Fx in the X direction and the focal length F in the Y direction.
Let Px and Py be the reciprocals of y, respectively, the curvature Cy1 in the Y direction of the effective area where the principal ray passing through the maximum field angle in the positive Y direction at the angle of view in the X direction and the second surface, and Y at the field angle of zero in the X direction. The difference Cy1-Cy3 from the curvature Cy3 in the Y direction of the effective area where the principal ray passing through the maximum angle of view in the negative direction hits the second surface is defined as P
The value obtained by dividing by y is CyG.

[21] The above [1] to [8], [1]
4] In the eccentric prism optical system according to any one of [20], an axial principal ray passing through the center of the pupil of the eccentric prism optical system and reaching the center of the image plane exits the pupil and the first surface. An axis defined by a straight line that intersects with the axis is defined as a Z-axis, an axis orthogonal to the Z-axis and within the eccentric plane of each surface constituting the eccentric prism optical system is defined as a Y-axis, and orthogonal to the Z-axis. And an axis orthogonal to the Y axis is defined as an X axis, wherein the following condition is satisfied. −0.01 <CxH <0.1 (H-1) However, the light passes through a point of a small amount H in the X-axis direction from the pupil center in parallel with the axial principal ray, and is parallel to the axial principal ray. The NA of the exit ray when the ray incident on the optical system is traced
The value obtained by dividing (the value of the sine of the angle formed by the on-axis principal ray) by the above H is defined as the focal length Fx of the entire optical system in the X direction. The value obtained by dividing the NA of the exit ray (the value of the sin of the angle formed with the axial principal ray) when the ray incident on the optical system in parallel with the principal ray by the ray tracing is divided by the H is used in the Y direction of the entire optical system. The focal length Fy is defined as the focal length Fx in the X direction and the focal length F in the Y direction.
The reciprocals of y are Px and Py, respectively. The curvature Cx1 in the X direction of the effective area where the principal ray passing through the maximum field angle in the Y positive direction at the angle of view in the X direction is zero and the Y angle at the field angle in the X direction is zero. The difference Cx1-Cx3 between the effective area where the principal ray passing through the maximum angle of view in the negative direction hits the second surface and the curvature Cx3 in the X direction is defined as P
The value obtained by dividing x is CxH.

[22] The above [1] to [8], [1]
[4] In the decentered prism optical system according to any one of [21] to [21], an axial principal ray passing through the center of the pupil of the decentered prism optical system and reaching the center of the image plane exits the pupil, and the first surface An axis defined by a straight line that intersects with the axis is defined as a Z-axis, an axis orthogonal to the Z-axis and within the eccentric plane of each surface constituting the eccentric prism optical system is defined as a Y-axis, and orthogonal to the Z-axis. And an axis orthogonal to the Y axis is defined as an X axis, wherein the following condition is satisfied. 0 <CyI <5 (I-1) However, the light passes through a point of a minute amount H in the X-axis direction from the pupil center in parallel with the axial principal ray, and enters the optical system in parallel with the axial principal ray. NA of exit ray when ray tracing the incident ray
The value obtained by dividing (the value of the sine of the angle formed by the on-axis principal ray) by the above H is defined as the focal length Fx of the entire optical system in the X direction. The value obtained by dividing the NA of the exit ray (the value of the sin of the angle formed with the axial principal ray) when the ray incident on the optical system in parallel with the principal ray by the ray tracing is divided by the H is used in the Y direction of the entire optical system. The focal length Fy is defined as the focal length Fx in the X direction and the focal length F in the Y direction.
Let Px and Py be the reciprocals of y, respectively, the curvature Cy1 in the Y direction of the effective area in which the principal ray passing through the maximum field angle in the positive Y direction at the angle of view in the X direction and the third surface, and Y at the angle of view in the X direction are zero. The difference Cy1-Cy3 from the curvature Cy3 in the Y direction of the effective area where the principal ray passing through the maximum angle of view in the negative direction hits the third surface is defined as P
The value obtained by dividing y is referred to as CyI.

[23] [1] to [8], [1]
4] In the eccentric prism optical system according to any one of [22], an axial principal ray passing through the center of the pupil of the eccentric prism optical system and reaching the center of the image plane exits the pupil, and the first surface An axis defined by a straight line that intersects with the axis is defined as a Z-axis, an axis orthogonal to the Z-axis and within the eccentric plane of each surface constituting the eccentric prism optical system is defined as a Y-axis, and orthogonal to the Z-axis. And an axis orthogonal to the Y axis is defined as an X axis, wherein the following condition is satisfied. 0 <CxJ <1 (J-1) However, the light passes through a point of a small amount H in the X-axis direction from the pupil center in parallel with the axial principal ray, and passes through the optical system in parallel with the axial principal ray. NA of exit ray when ray tracing the incident ray
The value obtained by dividing (the value of the sine of the angle formed by the on-axis principal ray) by the above H is defined as the focal length Fx of the entire optical system in the X direction. The value obtained by dividing the NA of the exit ray (the value of the sin of the angle formed with the axial principal ray) when the ray incident on the optical system in parallel with the principal ray by the ray tracing is divided by the H is used in the Y direction of the entire optical system. The focal length Fy is defined as the focal length Fx in the X direction and the focal length F in the Y direction.
Let Px and Py be the reciprocals of y, respectively, the curvature Cx1 in the X direction of the effective area where the principal ray passing through the maximum field angle in the Y positive direction at the angle of view in the X direction is zero and the angle of view in the X direction is zero. The difference Cx1-Cx3 from the curvature Cx3 in the X direction of the effective area in which the principal ray passing through the maximum angle of view in the negative direction hits the third surface is represented by P
The value divided by x is defined as CxJ.

[24] At least three surfaces are arranged eccentrically to each other, and a space between them is filled with a transparent medium having a refractive index of 1.3 or more, and a light beam emitted from the image surface is received to form an exit pupil. In the decentered prism optical system, the first optical system is formed of a rotationally symmetric surface having at least a transmission function of emitting a light beam incident on the optical system and a reflection function of bending the light beam inside the optical system. A second surface formed of a rotationally asymmetric surface that is disposed to face the first surface and that has a function of entering the optical system and reflecting a light beam inside the optical system toward the first surface; A third surface arranged so that the surface faces the image surface, and having a function of causing a light beam emitted from the image surface to enter the inside of the optical system, wherein the third surface is the first surface And the second
It is arranged at a position substantially perpendicular to the direction facing the surface,
The first surface has a shape with a convex surface directed in the direction of the second surface, and at least a light beam incident from the third surface passes through the inside of the optical system, is reflected by the first surface, and The light beam reflected by one surface passes through the inside of the optical system and is reflected by the second surface, and the light beam reflected by the second surface is directed from the first surface facing the second surface to the exit pupil. The first surface, the second surface, and the third surface are arranged as surfaces constituting the optical system so that the light is emitted. The axial chief ray passing through the center of the image plane of the system and reaching the center of the exit pupil is the first principal ray.
With a straight line extending from the exit pupil in a direction along the straight line extending from the exit pupil to entering the exit pupil, the distance from the exit pupil to the first surface in the direction along the straight line is closer to the image plane than to the image plane. The decentered prism optical system, wherein the first surface is arranged to be inclined with respect to the straight line so as to be smaller than the opposite side.

[25] At least three planes are arranged eccentrically to each other, and a space between them is filled with a transparent medium having a refractive index of 1.3 or more, and a light beam incident from a pupil plane is received to form an image plane. In the decentered prism optical system, at least the optical system is disposed so that a surface thereof faces the pupil plane, and has a transmission function of causing a light flux emitted from the pupil plane to enter the interior of the optical system, and a transmission function of A first surface formed of a rotationally symmetric surface having a reflection function of bending the light beam, and a light beam incident on the optical system disposed opposite to the first surface and directed to the first surface inside the optical system; A second surface formed of a rotationally asymmetric surface having an action of reflecting
A third surface disposed at a position substantially perpendicular to a direction in which the first surface and the second surface face each other, and having a transmission function of emitting a light beam incident on the optical system toward the image surface; The first surface has a shape with a convex surface facing in the direction of the second surface, and at least a light beam incident from the first surface is reflected by a second surface facing the first surface, and The light beam reflected by the two surfaces is reflected by the first surface facing the second surface, and the light beam reflected by the first surface passes through the inside of the optical system and is directed from the third surface to the image surface. The first surface, the second surface, and the third surface are arranged as surfaces constituting the optical system, and further, in the YZ cross-section, which is a turning direction of light rays, An axial principal ray passing through the center of the pupil plane of the optical system and reaching the center of the image plane exits the pupil plane and intersects the first surface. The distance from the pupil plane to the first surface in a direction along the straight line until the image plane side is smaller than the opposite side to the image plane. An eccentric prism optical system, wherein one surface is arranged to be inclined with respect to the straight line.

[0108]

As is apparent from the above description, according to the present invention, the present invention can be used in an imaging optical system or an eye optical system capable of obtaining an image with a clear and less distortion even at a wide angle of view.
A wide surface of one effective area is constituted by a rotationally symmetric surface,
An eccentric prism optical system that can be easily evaluated at the time of manufacture can be provided.

[Brief description of the drawings]

FIG. 1 is an optical path diagram when a decentered prism optical system according to the present invention has a three-plane configuration.

FIG. 2 is an optical path diagram illustrating another configuration of the decentered prism optical system of the present invention.

FIG. 3 is a cross-sectional view of the decentered prism optical system according to the first embodiment of the present invention.

FIG. 4 is a sectional view of an eccentric prism optical system according to a second embodiment of the present invention.

FIG. 5 is a sectional view of an eccentric prism optical system according to a third embodiment of the present invention.

FIG. 6 is a sectional view of an eccentric prism optical system according to a fourth embodiment of the present invention.

FIG. 7 is an aberration diagram illustrating image distortion of the first embodiment.

FIG. 8 is an aberration diagram illustrating image distortion of the second embodiment.

FIG. 9 is an aberration diagram illustrating image distortion of the third embodiment.

FIG. 10 is an aberration diagram illustrating image distortion of the fourth embodiment.

FIG. 11 is a partial diagram of a spot diagram showing an aberration correction state according to the first embodiment.

FIG. 12 is another partial diagram of the spot diagram showing the aberration correction state in the first embodiment.

FIG. 13 is a diagram of the remaining part of the spot diagram representing the aberration correction state of the first embodiment.

FIG. 14 is a diagram showing a state in which a head-mounted image display device using the eccentric prism optical system of the present invention is mounted on the observer's head.

15 is a sectional view of the vicinity of the head in FIG.

FIG. 16 is a perspective view showing a configuration of a camera using the decentered prism optical system of the present invention.

FIG. 17 is an optical path diagram of a photographing optical system using the decentered prism optical system of the present invention.

FIG. 18 is an optical path diagram of a finder optical system using the decentered prism optical system of the present invention.

FIG. 19 is an overall configuration diagram of the endoscope apparatus.

FIG. 20 is a sectional view of a distal end portion of a rigid endoscope using the eccentric prism optical system of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Pupil 2 ... Optical axis 3 ... 1st surface 4 ... 2nd surface 5 ... 3rd surface 6 ... Image surface 7 ... Eccentric prism optical system 8 ... 4th subject 10 ... Center of rotationally symmetric aspherical surface (top surface) 11 ... Tangent line 12 ... Rotation center axis 13 ... Point where the axial chief ray is internally reflected 20 ... Endoscope 21 ... Tip 22 ... Insertion part 23 ... Base 24 ... Camera 25 ... Monitor 26 ... Light guide cable 27 ... Light source device 30 ... Endoscope device 31 ... Eccentric prism optical system 32 ... Objective lens 33 ... Light guide 100 ... Eyepiece optical system 101 ... Image display element 102 ... Image display device (display device main body) 103 ... Temporal frame 104 ... Speaker 105 ... Video Voice transmission code 106 playback device 107 adjustment unit 150 objective lens 151 front group 152 pupil position 153 rear group 154 film 200 objective lens group 201 eccentric prism Manabu system 202 ... roof surface 203 ... roof prism 204 ... eyepiece 205 ... observer's eyeball La ... optical axis Lb ... optical axis of the imaging optical system of the finder optical system

Claims (3)

[Claims] 1. An eccentric prism optical system 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.
The optical system performs at least two internal reflections,
At least two of the three surfaces are formed by reflecting surfaces, and the two light reflecting surfaces by the two reflecting surfaces are folded back inside the optical system. Two reflective surfaces are arranged, and among the two surfaces having the reflective effect, the shape of one surface is formed by a rotationally asymmetric surface having no rotationally symmetric axis both in-plane and out-of-plane. The shape of at least an effective surface of one surface (a region through which light flux is transmitted and / or reflected in the entire surface) is a rotationally symmetric aspheric surface having an axis of rotational symmetry in the effective surface, and the symmetric aspheric surface Is formed as a first surface having both a transmission function of causing a light beam passing through the optical system to enter or exit and a reflection function of bending the light beam inside the optical system, and the rotationally asymmetric surface is disposed to face the first surface. 2nd surface And a third surface having a transmissive function of emitting or entering a light beam passing through the optical system is located at a position substantially perpendicular to the opposing direction of the first surface and the second surface. A decentered prism optical system which is arranged and has a configuration in which the first surface has a convex surface facing the direction of the second surface, and satisfies the following conditions. 5 ° <α <30 ° (0-1) where α is the rotation center axis of the rotationally symmetric aspheric surface of the first surface that reaches the image plane center through the center of the pupil of the optical system. This is the angle at which the on-axis principal ray intersects with the straight line from the exit of the pupil to the intersection with the first surface (the inclination angle of the surface). 2. A decentered prism optical system 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.
The optical system performs at least two internal reflections,
At least two of the three surfaces are formed by reflecting surfaces, and the two light reflecting surfaces by the two reflecting surfaces are folded back inside the optical system. Two reflective surfaces are arranged, and among the two surfaces having the reflective effect, the shape of one surface is formed by a rotationally asymmetric surface having no rotationally symmetric axis both in-plane and out-of-plane. The shape of at least an effective surface of one surface (a region where a light beam transmits and / or reflects in the entire surface) is constituted by a rotationally symmetric spherical surface having a rotationally symmetric axis in the effective surface, and the symmetrical spherical surface is: The first surface is formed as a first surface having both a transmissive function of allowing a light beam passing through the optical system to enter or exit and a reflective function of bending the light beam inside the optical system, and the rotationally asymmetric surface is disposed to face the first surface. As the second side A third surface, which is formed and has a transmission function of emitting or entering a light beam passing through the optical system, is disposed at a position substantially perpendicular to a direction in which the first surface and the second surface face each other. A decentered prism optical system, wherein the first surface has a shape with a convex surface facing the direction of the second surface, and satisfies the following conditions. 5 ° <α <30 ° (0-1) where α is a point at which the axial principal ray reaching the center of the image plane through the center of the pupil of the optical system is reflected by the first surface. The angle at which the central axis of rotation of the passing symmetric sphere intersects with the straight line from the center of the pupil of the optical system to the axial principal ray reaching the center of the image plane exiting the pupil and intersecting the first surface ( Angle of inclination of the surface). 3. The decentered prism optical system according to claim 1, wherein the first surface is formed such that the transmission function and the reflection function overlap in at least a part of the effective plane. An eccentric prism optical system characterized in that at least a reflection action in a region where the transmission action and the reflection action in the effective surface of the first surface overlap with each other is based on a total reflection action.