JPH10282421A - Eccentric prism optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an eccentric prism optical system whose first surface of a wide effective area having transmitting or reflecting action in the side close to a pupil is composed of a rotary symmetric spherical or aspherical surface. SOLUTION: This system is composed of three surfaces 3, 4, 5, the intervals between the surfaces 3-5 are buried in a transparent medium whose refractive index is larger than 1, light emitted from an object is first passes through the pupil of the optical system 7, made incident on a first surface 3 having transmitting/reflecting action, entered in the optical system 7, the incident light is reflected in the direction approaching the pupil 4 by a second surface 4 of a reflection plane having only the reflecting action and being located in the farther side from the pupil 1, next, reflected again by the first surface 3 in the direction far from the pupil 1, the reflected light is transmitted through the third surface 5 having only transmitting action, reaches an image plane 6 and forms the image. The first surface 3 is composed of a rotary symmetric surface such as a spherical surface and the second surface 4 is composed of a rotary asymmetric surface.

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. While forming, the two reflective surfaces are arranged at positions where the light rays reflected by the two reflective surfaces do not intersect inside the optical system. Among the surfaces, the shape of one surface is formed by a rotationally asymmetric surface having no rotationally symmetric axis both in-plane and out-of-plane, and at least the effective surface of another surface (light flux is transmitted through the entire area of the surface). And / or the area of reflection) is constituted by a rotationally symmetric surface having a rotationally symmetric axis in the effective plane.

In this case, the rotationally symmetric surface is formed as a first surface having both a transmitting action for entering or emitting a light beam passing through the optical system and a reflecting action for bending the light beam inside the optical system. Is formed as a second surface opposed to the first surface, and further has a transmission function of emitting or entering a light beam passing through the optical system.
The surface is disposed at a position substantially perpendicular to the direction in which the first surface and the second surface face each other, and at least the eccentric prism optical system includes the first surface, the second surface, and the third surface. Can be.

In this case, 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 transmission function and the reflection function in the effective surface of the first surface are provided. It is desirable that the reflection action in the area overlapping with the reflection action 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.

Next, a coordinate system used in the following description will be described. As shown in FIG. 1, an axial principal ray that passes through the center of the pupil 1 of the decentered prism optical system 7 and reaches the center of the image plane 6 (image display element when used as an eyepiece optical system) exits the pupil 1. An axis defined by a straight line (coinciding with the optical axis 2; when used as an eyepiece optical system, becomes an observer's visual axis) until it intersects the first surface 3 of the eccentric prism optical system 7 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 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. Then, the direction in which the axial chief ray reaches the image plane from the object point is defined as the positive direction of the Z-axis.
Is defined as the positive direction of the Y axis, and the direction of the X axis forming the right hand system with the Y axis, the Z axis, and the positive direction of the X axis.

In general, it is difficult to manufacture an eccentric prism optical system by polishing, and it is necessary to form one by one 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.

[0016] More preferably, the effective area is widest,
An eccentric prism that can easily evaluate the finished shape of the surface shape in a short time by configuring the surface having the transmission function and the internal reflection function on the side close to the pupil where the aberration degradation is relatively large as a rotationally symmetric surface The 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 definition, 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, Y 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.

[0019]

That is, as described in Table 1 above, the on-axis 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:

The minute amount H (m
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.

When 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 power (power) Pxn, Pyn in the X and Y directions of the surface at the position where the axial principal ray passing through the center of the object point 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 for 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 action is a surface which is arranged eccentrically. If this surface is constituted by a rotationally symmetric surface, image distortion, astigmatism, coma and the like will be largely generated. 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 principal axis 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 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 will be too different. However, the curvature of the entire effective area of the second surface having the strongest refracting power in the optical system changes too much, and it becomes impossible to obtain a wide flat image over the entire angle of view or to observe an 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) from the viewpoint of 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 more preferable to satisfy the following condition: 0 <CxH <0.05 (H-2) from the viewpoint of aberration correction.

More preferably, 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.

Further, 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. 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.

It is more preferable that 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)

The conditions (A-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. Further, the present invention can be applied not only to a plane symmetric free-form surface but also to an anamorphic surface, that is, to any rotationally asymmetric surface shape having no rotational symmetry axis both inside and outside the surface. Further, the second surface having only the reflection function can be constituted by a toric surface.

In the above description, the eccentric prism optical system 7 is telecentric on the image plane 6 side in FIG. 1, that is, the image of the pupil 1 by the eccentric prism optical system 7 (exit pupil, eyepiece optics). When used as a system, it is assumed that the position of the entrance pupil can be at infinity, but an image is formed at a finite position on the opposite side of the image plane 6 from the third surface 5 (image-side non-telecentric). ). In this case, when the eccentric prism optical system 7 is used particularly as an eyepiece optical system, a smaller LCD (liquid crystal display element) or the like can be used as an image display element arranged on the image plane 6. The reason is that pupil 1
Is located at a finite position on the opposite side of the third surface 5 of the image plane 6, the light exits from each point on the display surface of the image display element arranged on the image plane 6 and reaches the center of the pupil 1. The chief ray enters the third surface 5 of the eccentric prism optical system 7 while diverging, so that the size of the image display element itself can be reduced. Accordingly, the eccentric prism optical system 7 can be configured to be smaller, and the entire image display device using the eccentric prism optical system 7 as the eyepiece optical system can be reduced in size and wide in angle of view.

As described above, when the image side is non-telecentric, the decentered prism optical system 7 operates under the above condition (B
Instead of (-1) and (C-1), the following condition (K-1)
It is desirable to satisfy at least one of (L-2) to (L-2).

That is, the refracting powers (powers) Pxn, Py in the X and Y directions of the surface at the position where the axial principal ray passing through the center of the object point and passing through the center of the pupil hits the second surface having only the reflecting action.
n and focal lengths Fx and F in the X and Y directions of the entire optical system.
The relationship between refractive powers (powers) Px and Py, which are the reciprocals of y, is as follows: when Pxn / Px is PxB and Pyn / Py is PyC, 0.8 <| PxB | <5 (K-1) 0.8 <| PyC | <5 (L-1) It is preferable that one of the following conditions is satisfied.

If the upper limit of 5 to condition (L-1) is exceeded, the power in the Y direction of the first reflecting surface (second surface 4) becomes too strong as compared with the power of the entire system, and the image position Cannot be taken out of the prism optical system, and the image display element cannot be arranged. Conversely, if the lower limit of 0.8 is exceeded, the positive power of the surfaces other than the first reflecting surface becomes too strong, and the curvature of field generated on the first reflecting surface becomes excessively corrected, and the occurrence of chromatic aberration increases. Would.

When the value exceeds the upper limit of 5 to condition (K-1), the power in the X direction of the first reflecting surface (second surface 4) becomes too strong as compared with the power of the entire system. The surface curvature is excessively corrected, and other aberrations cannot be completely removed, which is not preferable for aberration correction. Conversely, if the lower limit of 0.8 is exceeded,
The optical system itself becomes large.

To further reduce the size, 1.2 <| PxB | <2.5 (K-2) 1.2 <| PyC | <2.5 (L-2) It is preferable to satisfy the formula.

When the value exceeds the upper limit of 2.5 of the condition (L-2), the curvature of field is excessively corrected, which is not preferable for aberration correction. If the lower limit of 1.2 is exceeded, the optical system will be large. When the value exceeds the upper limit of 2.5 of the above condition (K-2),
The field curvature is excessively corrected, which is not preferable for aberration correction. If the lower limit of 1.2 is exceeded, the optical system will be large.

Further, as described above, when the first surface having the reflection function and the transmission function is constituted by a rotationally symmetric aspherical surface, and the second surface having only the reflection function is constituted by an anamorphic surface or a toric surface. In particular, assuming that the inclination of the second reflection surface (first surface 3) with respect to the optical axis is α (corresponding to α in the embodiment described later), 5 ° <α <30 ° (M-1) It is desirable to satisfy the conditional expression in order to correct aberration.

When the lower limit of 5 ° to the above condition (M-1) is exceeded, the inclination of the second reflecting surface with respect to the optical axis becomes too small.
It becomes impossible to correct rotationally asymmetric aberration generated on the first reflecting surface. On the other hand, when the angle exceeds the upper limit of 30 °, the inclination of the second reflection surface with respect to the optical axis becomes too large, so that a large chromatic dispersion occurs when the light passes through the first surface, thereby deteriorating the optical performance.

[0061]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments 1 to 8 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 plane with eccentricity, the amount of eccentricity in the X-axis, Y-axis, and Z-axis directions 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 central axis of the plane (anamorphic plane, X toric plane,
For the Y toric surface, free-form surface, and rotationally symmetric aspheric surface, the following expressions (a), (b), (c),
The inclination angles (α, β, and γ) of the X axis, the Y axis, and the Z axis of equations (d) and (g), respectively, are given. 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 An axial conic coefficient, Ky is a Y-axial conic coefficient, Rn is an aspherical term rotationally symmetric component, and Pn is an aspherical term rotationally asymmetric component. 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 toric surface includes an X toric surface and a Y toric surface, each of which 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 toric surface. X toric surface, F (X) = Cx · X 2 / [1+ {1- (1 + K) Cx 2 · X 2} 1/2] + AX 4 + BX 6 + CX 8 + DX 10 ··· Z = F (X) + (1/2) Cy {Y ² + Z ² −F (X) ² } (b) The Y toric surface is expressed as follows: F (Y) = Cy · Y ² / [1+ ｛1− (1 + K) Cy ²・ Y ² ｝ ^1/2 ] + AY ⁴ + BY ⁶ + CY ⁸ + DY ¹⁰ ... Z = F (Y) + (１ ／) Cx ｛X ² + Z ² -F (Y) ² ｝ (c) Here, Z is the amount of deviation of the surface shape from the tangent plane to the origin, Cx is the curvature in the X-axis direction, Cy is the curvature in the Y-axis direction, K is the conic coefficient, and A, B, C, and D are the aspherical coefficients. Note that X
Axial radius of curvature Rx, Y-axis radius of curvature Ry and curvature C
x and Cy have a relationship of Rx = 1 / Cx, Ry = 1 / Cy.

The shape of a free-form surface that is a 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 free-form surface having only one symmetry surface) is defined by an expression representing this free-form surface, when the symmetry caused by the symmetry surface is determined in the X direction, X Is set to 0 (for example, the coefficient of the X odd order is set to 0) and the symmetry caused by the symmetry plane is obtained in the Y direction, the odd order of Y is set to 0 (for example, Y
The coefficient of the odd-order term may be set to 0).

Here, as an example, if k = 7 (7th 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 ... (D) And 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 (e). 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) (E) 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 expression (Z = _{{n} m} C _nm X
ⁿ Y ^nm ) in the plane symmetric to the X direction, as in the equation (d).
In the case of representing a plane where k = 7, it can be expanded as in the following equation (f).

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 | (f) The shape of the rotationally symmetric aspheric 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 ··· ··· ( g) where Y is a direction perpendicular to Z, R is a paraxial radius of curvature, P is a conic coefficient, and A ₄ , A ₆ , A ₈ , and A ₁₀ are aspherical 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.

Next, FIG. 3 to FIG.
8 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 is the same as that shown in FIG.
As in the case of, it consists of three faces 3, 4, 5;
A space between the three surfaces 3 to 5 is filled with a transparent medium having a refractive index larger than 1, and a light beam emitted from an object (not shown) first passes through the pupil 1 of the optical system 7 along the optical axis 2. Incident on the first surface 3 having a transmitting action and a reflecting action and entering the optical system 7, and the incident light is incident on the pupil 1 at a second face 4, which is a reflecting face having a reflecting action only on the side farther from the pupil 1. The light is reflected in the approaching direction, and is again reflected on the first surface 3 in the direction away from the pupil 1, and the reflected light is transmitted through the third surface 5 having only the transmitting action.
And reaches the image plane 6 to form an image.

In the first to third embodiments, the first surface 3 is a spherical surface eccentric with the concave surface facing the pupil 1 side. In the fourth embodiment, the first surface 3 has the concave surface facing the pupil 1 side. A rotationally symmetric aspherical surface defined by the above equation (g),
Further, in any of the first to fourth embodiments, the second surface 4 and the third surface 5 are formed by free-form surfaces defined by the above equation (d).

In the fifth embodiment, similar to the fourth embodiment,
The first surface 3 is eccentric with the concave surface facing the pupil 1 (g).
The second surface 4 and the third surface
The surface 5 is composed of a free-form surface defined by the above equation (d), but is non-telecentric on the image surface 6 side (other embodiments are telecentric), and the eyepiece optics of the image display device. When used as a system, the size of the LCD disposed on the image plane 6 is reduced, and accordingly, the eccentric prism optical system 7
Can be configured to be smaller.

In the sixth embodiment, the first surface 3 is a rotationally symmetric aspheric surface defined by the above equation (g), which is decentered with the concave surface facing the pupil 1 side, and the second surface 4 is the above (a ), And the third surface 5 is the anamorphic surface defined in (d) above.
It consists of a free-form surface defined by an equation.

In the seventh embodiment, the first surface 3 is a rotationally symmetric aspheric surface defined by the above equation (g), which is decentered with the concave surface facing the pupil 1 side, and the second surface 4 is the above (b) ), And the third surface 5 is a free-form surface defined by the above equation (d).

In the eighth embodiment, the first surface 3 is a rotationally symmetric aspheric surface defined by the above equation (g), which is decentered with the concave surface facing the pupil 1 side, and the second surface 4 is the (c) ), And the third surface 5 is a free-form surface defined by the above equation (d).

When the image display device is configured as an eyepiece optical system, the LCD disposed on the image plane 6 is the same as that of the first embodiment.
~ 4,6 ~ 8 are 0.7 inch type 14.4mm length and width
X10.7 mm screen, and Example 5 had a screen size of 0.1 mm.
A 55-inch screen with a vertical and horizontal 11.2 mm × 8.3 mm screen is used.
Is horizontal view angle 37 °, vertical view angle 27.6 °, pupil diameter 4mm
In Examples 5 to 8, the horizontal angle of view was 35 ° and the vertical angle of view was 2
6.6 °, pupil diameter 4 mm. The following Examples 1 to
8 shows the configuration parameters of FIG.

Example 1 Surface number Curvature radius Interval Eccentricity Refractive index Abbe number Object plane 数 ∞ 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 plane ∞ 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 Zα (°) β (°) γ (°) Eccentricity (1) 0.000 7.108 25.777 19.22 0.00 0.00 Eccentricity (2) 0.0 00 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 面 ∞ 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. 528 -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 Surface ∞ ∞ 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 surface) Eccentricity (1) 1.4922 57.5 5 Free-form surface Eccentricity (3) Image surface 偏 Eccentricity (4) Aspherical surface 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 -1.0 139 × 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 4.7482 _{^{× 10 -4 C 19 -1.2350 × 10}} -4 C 21 -2.0224 × 10 -5 C 25 -1.1895 × 10 -5 C 27 3.5172 × 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.

Example 5 Surface Number Curvature Radius Interval Eccentricity Refractive Index Abbe Number Object Surface ∞ -1000.00 1 ∞ (pupil) 2 -72.86 (aspherical surface) Eccentricity (1) 1.5254 56.2 3 Free-form surface Eccentricity (2) 1.5254 56.2 4- 72.86 (Aspherical surface) Eccentricity (1) 1.5254 56.2 5 Free-form surface Eccentricity (3) Image surface ∞ Eccentricity (4) Aspherical surface coefficient Surface number: 2,4 P = 1 A ₄ = 7.3202 × 10 ^-6 A ₆ = -4.5848 × 10 ^-8 A ₈ = 1.2150 × 10 ^-10 A ₁₀ = -1.1619 × 10 ^-13 Free-form surface C ₅ -1.2157 × 10 ^-2 C ₇ -1.2440 × 10 ^-2 C ₈ 7.1548 × 10 ^-5 C ₁₀ 2.6433 × 10 ^-5 C ₁₂ -6.0201 × 10 ^-7 C ₁₄ -2.9464 × 10 ^-6 C ₁₆ -1.8443 × 10 ^-6 C ₁₇ 1.0037 × 10 ^-7 C ₁₉ 2.5993 × 10 ^-7 C ₂₁ 9.7975 × 10 ^-8 Free-form surface C ₅ -4.1183 × 10 ^-2 C ₇ -2.1928 × 10 ^-3 C ₁₂ -1.0567 × 10 ^-4 C ₁ 1.4766 × 10 ^-5 XYZ α (°) β (°) γ (°) Eccentricity (1) 0.00 7.45 27.79 14.47 0.00 0.00 Eccentricity (2) 0.00 0.43 37.36 -16.58 0.00 0.00 Eccentricity (3) 0.00 17.08 32.25 69.19 0.00 0.00 Eccentricity (4) 0.00 19.49 33.47 61.09 0.00 0.00.

Example 6 Surface Number Curvature Radius Interval Eccentricity Refractive Index Abbe Number Object Surface ∞ -1000.00 1 ∞ (pupil) 2 -135.92 (aspheric) Eccentricity (1) 1.5254 56.2 3 Rx -53.99 Eccentricity (2) 1.5254 56.2 Ry -54.82 (anamorphic surface) 4 -135.92 (aspherical) eccentric (1) 1.5254 56.2 5 free curved eccentric (3) image surface ∞ eccentricity (4) aspheric coefficient surface number: 2,4 P = 1 A ₄ = 3.0229 × 10 ^-6 A ₆ = -2.0717 × 10 ^-9 Anamorphic surface Kx = 0 Ky = 0 R1 = 4.7325 × 10 ^-8 R2 = 8.6594 × 10 ^-10 P1 = 0 P2 = 0 Free-form surface C ₅ -1.8749 × 10 ^-3 C ₇ 9.1597 × 10 ^-3 C ₈ 8.2909 × 10 ^-4 C ₁₀ -8.4394 × 10 ^-5 C ₁₂ 5.2728 × 10 ^-5 C ₁₄ -1.6639 × 10 ^-5 C ₁₆ -3.2691 × 10 ^-5 X YZ α (°) β (°) γ (°) Eccentricity (1) 0.00 8.04 27.45 21.43 0.00 0.00 Eccentricity (2) 0.00 1.00 39.30 -12.15 0.00 0.00 Eccentricity (3) 0.00 18.33 30.49 91.46 0.00 0.00 Eccentricity (4) 0.00 23.20 32.92 68.80 0.00 0.00.

Example 7 Surface Number Curvature Radius Interval Eccentricity Refractive Index Abbe Number Object Surface ∞ -1000.00 1 ∞ (pupil) 2 -114.15 (aspheric) Eccentricity (1) 1.5254 56.2 3 Rx -50.16 Eccentricity (2) 1.5254 56.2 Ry -51.55 (X toric surface) 4 -114.15 (aspherical) eccentric (1) 1.5254 56.2 5 free curved eccentric (3) image surface ∞ eccentricity (4) aspheric coefficient surface _{number: 2,4 P = 1 A 4 =} 3.5141 _{^{× 10 -6 A 6 = -2.6064 ×}} 10 -9 X toric surface K = 0 A = 3.0895 × 10 -6 B = -8.2732 × 10 -9 free curved surface ^{_{C 5 -2.0345 × 10 -3 C 7}} 1.0406 × 10 - ² C ₈ 1.4416 × 10 ^-3 C ₁₀ -3.0693 × 10 ^-5 C ₁₂ 3.7247 × 10 ^-5 C ₁₄ -1.5925 × 10 ^-6 C ₁₆ -4.7704 × 10 ^-5 XYZ α (°) β (°) γ (°) Eccentricity (1) 0.00 8.22 27.43 19.91 0.00 0.00 Eccentricity (2) 0.00 0.86 38.81 -13.66 0.00 0.00 Eccentricity (3) 0.00 17.87 30.43 88.91 0.00 0.00 Eccentricity (4) 0.00 22.24 32.58 70.07 0.00 0.00.

Example 8 Surface Number Curvature Radius Interval Eccentricity Refractive Index Abbe Number Object Surface ∞ -1000.00 1 ∞ (pupil) 2 -180.53 (aspheric) Eccentricity (1) 1.5254 56.2 3 Rx -57.08 Eccentricity (2) 1.5254 56.2 Ry -60.96 (Y toric surface) 4 -180.53 (aspherical) eccentric (1) 1.5254 56.2 5 free curved eccentric (3) image surface ∞ eccentricity (4) aspheric coefficient surface _{number: 2,4 P = 1 A 4 =} 1.1219 _{^{× 10 -6 A 6 = -4.6751 ×}} 10 -10 Y toric surface K = 0 A = -3.7067 × 10 -6 B = 8.2099 × 10 -9 free curved surface ^{_{C 5 -2.3428 × 10 -2 C 7}} 7.0092 × 10 - ³ C ₈ 1.1904 × 10 ^-3 C ₁₀ 7.4712 × 10 ^-5 C ₁₂ 3.3526 × 10 ^-4 C ₁₄ 4.6065 × 10 ^-5 C ₁₆ -2.4730 × 10 ^-5 XYZ α (°) β (°) γ ( °) Eccentricity (1) 0.00 8.16 27.28 25.23 0.00 0.00 Eccentricity (2) 0.00 1.35 40.47 -9.67 0.00 0.00 Eccentricity (3) 0.00 19.09 29.65 96.11 0.00 0.00 Eccentricity (4) 0.00 23.55 31.50 74.19 0.00 0.00.

FIGS. 11 to 18 show aberration diagrams representing image distortions in the above-described Examples 1 to 8, respectively. 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. Also,
19 to 21 show spot diagrams representing 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). 22 to 24 show lateral aberration diagrams of the fifth embodiment. In these lateral aberration diagrams, the numbers in parentheses indicate (horizontal (X direction) angle of view, vertical (Y direction) angle of view), and indicate the lateral aberration at that angle of view.

Next, the conditional expressions (A)
-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. 25 shows a state in which the head-mounted image display device is mounted on the observer's head, and FIG. 26 is a cross-sectional view thereof. In this configuration, the decentered prism optical system of the present invention is used as an eyepiece optical system 100 as shown in FIG.
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. 25, 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. 25 denotes a switch of the playback device 106,
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. 28, 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. 9, 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 for transmitting an image to an eyepiece using a relay lens, an objective lens of a flexible endoscope for transmitting 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.
It is shown in FIG. FIG. 30 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 apparatus 30 shown in FIG. 30 includes an endoscope 20 having an insertion section 22 that houses an objective lens and an illumination optical system, a camera 24, a monitor 25, and a light source device 27. Endoscope 20
As shown in FIG. 31, 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. . 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 of surfaces having a reflective action so that the internal reflection of the light is performed, and light rays reflected by the two surfaces having a reflective action are reflected inside the optical system. The two surfaces having the reflecting action are arranged at positions where they do not intersect, and among the two surfaces having the reflecting action, the shape of one face has no rotational symmetry axis both in-plane and out-of-plane. The shape of at least the effective surface of the other one surface (the area where the light beam is transmitted and / or reflected in the entire surface) formed of the asymmetric surface is a rotationally symmetric surface having an axis of rotational symmetry in the effective surface. It is characterized by comprising Decentered prism optical system.

[2] In the decentered prism optical system according to the above [1], the rotationally symmetric surface has 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. It is formed as a first surface having both functions, and the rotationally asymmetric surface is formed as a second surface disposed opposite to the first surface, and further has a transmission function of emitting or entering a light beam passing through the optical system. A third surface is arranged at a position substantially perpendicular to a direction in which the first surface and the second surface face each other, and at least the eccentric prism optical system includes the first surface, the second surface, and the third surface. And a decentered prism optical system having a configuration including a surface.

[3] In the decentered prism optical system according to the above [2], the first surface is formed such that the transmission function and the reflection function thereof overlap in at least a part of the effective surface. The decentered prism optical system is 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 overlaps is a total reflection action.

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

[5] Any one of the above [2] 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], when the inclination of the first surface with respect to the optical axis is α, the following condition is satisfied: 5 ° <α <30 ° (M-1) An eccentric prism optical system characterized by satisfying the following.

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

[8] Any one of the above [2] 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.

[0106]

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

[10] From the above [2]

[9] In the eccentric prism optical system according to any one of [9], a light beam enters from the third surface, and the incident light beam passes through the inside of the optical system, is reflected by the first surface, and is reflected by the first surface. The first surface, the second surface, and the third surface are configured such that the light beam reflected by the surface is reflected by the second surface, and the light beam reflected by the second surface is emitted from the first surface. An eccentric prism optical system characterized by the fact that is disposed.

[11] In the eccentric prism optical system according to the above [10], the third surface is arranged at a position where a light beam from the means for displaying an image is incident, and the third surface is arranged at the first surface.
The eccentricity is characterized in that the surface is arranged at a position where a light beam emitted from the first surface is guided to an observer's eyeball, and is used for an image observation device that enables observation of an image formed by the light beam. Prism optics.

[12] From the above [2]

[9] In the eccentric prism optical system according to any one of [9], the light beam enters from the first surface, the incident light beam is reflected by the second surface, and the light beam reflected by the second surface is the light beam. The first surface, the second surface, and the third surface are arranged such that a light beam reflected by the first surface and reflected by the first surface passes through the optical system and exits from the third surface. An eccentric prism optical system characterized by the fact that is disposed.

[13] In the eccentric prism optical system according to the above [12], 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 observation 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.

[14] In the eccentric prism optical system according to the above [12], the first surface is arranged at a position where a light beam from an object enters, 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 is capable of photographing an object image formed by the light beam.

[15] From the above [2]

[9] In the eccentric prism optical system according to any one of [9], 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 intersects the first surface. An axis defined by a straight line up to is defined as a Z axis, an axis orthogonal to the Z axis and within an eccentric plane of each surface constituting the eccentric prism optical system is defined as a Y axis, orthogonal to the Z axis and Y An eccentric prism optical system which satisfies the following condition when an axis orthogonal to the axis is defined as an X axis. 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.

[16] From the above [2]

[9], [1
5] In the decentered prism optical system according to any one of [5],
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 in the eccentric plane of each surface constituting the eccentric prism optical system is defined as the Y axis, and an axis orthogonal to the Z axis and orthogonal to the Y axis is defined as the 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.

[17] From the above [2]

[9], [1
5] In the decentered prism optical system according to any one of [16], the center of the pupil of the decentered prism optical system is passed,
An axis defined by a straight line from the on-axis principal ray reaching the center of the image plane to exiting the pupil and intersecting the first surface is defined as a Z-axis. An eccentric prism optical system characterized by satisfying the following conditions when an axis in an eccentric plane of each surface 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. . 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.

[18] From the above [2]

[9], [1
5] In the decentered prism optical system according to any one of [5],
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 the axis in the eccentric plane of each surface constituting the eccentric prism optical system is defined as the Y axis, and the axis orthogonal to the Z axis and orthogonal to the Y axis is defined as the X axis, A decentered prism optical system which is configured as a non-telecentric optical system on the surface side and satisfies the following conditions. 0.8 <| PxB | <5 (K-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 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 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.

[19] From the above [2]

[9], [1
5] In the eccentric prism optical system according to any one of [18], the eccentric prism optical system passes through the center of a pupil of the eccentric prism optical system,
An axis defined by a straight line from the on-axis principal ray reaching the center of the image plane to exiting the pupil and intersecting the first surface is defined as a Z axis, and is orthogonal to the Z axis and constitutes the eccentric prism optical system. When the axis in the eccentric plane of each surface is defined as the Y axis, and the axis orthogonal to the Z axis and the axis orthogonal to the Y axis is defined as the X axis, the third surface side is configured as a non-telecentric optical system,
An eccentric prism optical system characterized by satisfying the following conditions. 0.8 <| PyC | <5 (L-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 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.

[20] From the above [2]

[9], [1
5] In the eccentric prism optical system according to any one of [19], 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. An eccentric prism optical system characterized by satisfying the following condition when an axis orthogonal to the Y axis is defined as an X axis. 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.

[21] From the above [2]

[9], [1
5] In the decentered prism optical system according to any one of [20] to [20], 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. An eccentric prism optical system characterized by satisfying the following condition when an axis orthogonal to the Y axis is defined as an X axis. −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.

[22] From the above [2]

[9], [1
5] In the decentered prism optical system according to any one of [20] to [20], 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. An eccentric prism optical system characterized by satisfying the following condition when an axis orthogonal to the Y axis is defined as an X axis. −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.

[23] From the above [2]

[9], [1
5] In the decentered prism optical system according to any one of [22], 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. An eccentric prism optical system characterized by satisfying the following condition when an axis orthogonal to the Y axis is defined as an X axis. −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.

[24] From the above [2]

[9], [1
5] In the eccentric prism optical system according to any one of [23], 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. An eccentric prism optical system characterized by satisfying the following condition when an axis orthogonal to the Y axis is defined as an X axis. −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.

[25] From the above [2]

[9], [1
5] In the decentered prism optical system according to any one of the items [24] to [24], 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. An eccentric prism optical system characterized by satisfying the following condition when an axis orthogonal to the Y axis is defined as an X axis. 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.

[26] From the above [2]

[9], [1
5] In the decentered prism optical system according to any one of the items [25] to [25], 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. An eccentric prism optical system characterized by satisfying the following condition when an axis orthogonal to the Y axis is defined as an X axis. 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.

[27] An eccentric prism optical system 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 as 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 positions where they do not intersect inside the system, and among the two surfaces having the reflecting action,
The shape of one surface is formed as a toric surface, and the shape of at least the effective surface of the other surface (the region through which light is transmitted and / or reflected in the entire area of the surface) has an axis of rotational symmetry in the effective surface. It is constituted by a rotationally symmetric surface, and the rotationally symmetric surface serves 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. The toric surface is formed as a second surface facing the first surface, and the third surface having a transmission function of emitting or entering a light beam passing through the optical system is the first surface. And at least the eccentric prism optical system is configured to include the first surface, the second surface, and the third surface. Feature Heart prism optical system.

[28] In the eccentric prism optical system according to the above [27], the first surface is formed such that the transmission function and the reflection function thereof overlap in at least a part of the effective plane. The decentered prism optical system is 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 overlaps is a total reflection action.

[29] The decentered prism optical system according to the above [27] or [28], wherein the rotationally symmetric surface of the first surface is formed by a rotationally symmetric aspherical surface. .

[30] The eccentric prism optical system according to any one of [27] to [29], wherein the third
A light beam enters from the surface, the incident light beam passes through the inside of the optical system and is reflected on the first surface, and the light beam reflected on the first surface is reflected on the second surface, and the second surface So that the light beam reflected by the light exits from the first surface.
A decentered prism optical system, wherein a surface, the second surface, and the third surface are arranged.

[31] In the eccentric prism optical system according to the above [30], the third surface is disposed at a position where a light beam from a means for displaying an image is incident, and the third surface is arranged at the first surface.
The eccentricity is characterized in that the surface is arranged at a position where a light beam emitted from the first surface is guided to an observer's eyeball, and is used for an image observation device that enables observation of an image formed by the light beam. Prism optics.

[32] The eccentric prism optical system according to any one of [27] to [29], wherein the first
A light beam enters from a surface, the incident light beam is reflected by the second surface, a light beam reflected by the second surface is reflected by the first surface, and a light beam reflected by the first surface is reflected by the optical surface. The first surface so as to pass through the inside of the system and exit from the third surface.
A decentered prism optical system, wherein a surface, the second surface, and the third surface are arranged.

[33] In the decentered prism optical system according to the above [32], 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.

[34] In the eccentric prism optical system according to the above [32], 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.

[35] In the decentered prism optical system according to any one of the above [27] to [29], 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 can be used. 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.

[36] From the above [27] to [29],
[35] In the eccentric prism optical system according to any one of [35], when the inclination of the first surface with respect to the optical axis is α, the following condition is satisfied: 5 ° <α <30 ° (M-1) An eccentric prism optical system characterized in that:

[0134]

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 a sectional view of an eccentric prism optical system according to a fifth embodiment of the present invention.

FIG. 8 is a sectional view of an eccentric prism optical system according to a sixth embodiment of the present invention.

FIG. 9 is a sectional view of an eccentric prism optical system according to a seventh embodiment of the present invention.

FIG. 10 is a sectional view of an eccentric prism optical system according to an eighth embodiment of the present invention.

FIG. 11 is an aberration diagram illustrating image distortion of the first embodiment.

FIG. 12 is an aberration diagram illustrating image distortion of the second embodiment.

FIG. 13 is an aberration diagram illustrating image distortion of the third embodiment.

FIG. 14 is an aberration diagram illustrating image distortion of the fourth embodiment.

FIG. 15 is an aberration diagram illustrating image distortion of the fifth embodiment.

FIG. 16 is an aberration diagram illustrating image distortion of the sixth embodiment.

FIG. 17 is an aberration diagram illustrating image distortion of the seventh embodiment.

FIG. 18 is an aberration diagram illustrating image distortion of the eighth embodiment.

FIG. 19 is a partial view of a spot diagram showing an aberration correction state according to the first embodiment.

FIG. 20 is another partial diagram of the spot diagram showing the aberration correction state in the first embodiment.

FIG. 21 is a diagram of the remaining portion of the spot diagram showing the aberration correction state of the first embodiment.

FIG. 22 is a partial view of a lateral aberration diagram showing an aberration correction state in Example 5.

FIG. 23 is another partial diagram of a lateral aberration diagram showing an aberration correction state in Example 5.

FIG. 24 is a diagram of the remaining part of the lateral aberration diagram showing the aberration correction state in the fifth embodiment.

FIG. 25 is a diagram showing a state in which the head-mounted image display device using the eccentric prism optical system of the present invention is mounted on the observer's head.

26 is a sectional view of the vicinity of the head in FIG. 25.

FIG. 27 is a perspective view showing a configuration of a camera using the decentered prism optical system of the present invention.

FIG. 28 is an optical path diagram of a photographing optical system using the decentered prism optical system of the present invention.

FIG. 29 is an optical path diagram of a finder optical system using the decentered prism optical system of the present invention.

FIG. 30 is an overall configuration diagram of the endoscope apparatus.

FIG. 31 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 ... Subject 4 surfaces 20 ... Endoscope 21 ... Tip 22 ... Insertion part Reference Signs List 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 / audio transmission code 106 reproducing device 107 adjusting unit 150 objective lens 151 front group 152 pupil position 153 rear group 154 film 200 ... Objective lens group 201 ... Eccentric prism optical system 202 ... Dach surface 203 ... Dach prism 204 ... Eyepiece lens 205 ... Observer eye La ... Finder Optical axis Lb ... the optical axis of the photographing optical system of the 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 surfaces having a reflection effect, and the light is reflected by the two surfaces having a reflection effect at a position where they do not intersect inside the optical system. Two surfaces having a reflecting action are arranged, and among the two faces having the reflecting action, the shape of one face is formed by a rotationally asymmetric face having no rotationally symmetric axis both in-plane and out-of-plane. The shape of at least an effective surface of one of the surfaces (a region through which light flux is transmitted and / or reflected in the entire surface) is constituted by a rotationally symmetric surface having an axis of rotational symmetry in the effective surface. Decentered prism optical system. 2. The eccentric prism optical system according to claim 1, wherein said rotationally symmetric surface has a transmission function of causing a light beam passing through said optical system to enter or exit, and a reflection function of bending said light beam inside said optical system. And the rotation-asymmetric surface is formed as a second surface opposed to the first surface, and further has a transmission function of emitting or entering a light beam passing through the optical system. A surface is disposed at a position substantially perpendicular to a direction in which the first surface and the second surface are opposed to each other, and at least the eccentric prism optical system includes the first surface, the second surface, and the third surface. A decentered prism optical system characterized by comprising: 3. The decentered prism optical system according to claim 2, wherein the first surface is formed such that the transmission function and the reflection function thereof overlap in at least a part of the effective plane. An eccentric prism optical system, wherein a reflection action in a region where a transmission action and a reflection action in the effective surface of the first surface overlaps is a total reflection action.