JPH10260357A - Eccentric prism optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the eccentric prism optical system which has a wide surface formed of a spherical or aspherical surface of rotational symmetry in an effective area of a 1st surface providing transmitting operation and reflecting operation nearby the pupil of an eccentric prism. SOLUTION: The eccentric prism 7 consists of three surfaces 3, 4, and 5, which are filled with a transparent medium having a >=1 refractive index; and a positive lens 9 is arranged on the incidence side of the 1st surface 3. Light beam flux emitted by a body passes through the pupil 1 of an optical system 10 along the optical axis 2 and is made incident on the 1st surface 3 of the eccentric prism 7 to enter a prism 7, the incident light beam is reflected by the 2nd surface 4 toward the pupil 1 and then reflected again by the 1st surface 3 away from the pupil 1 this time, and the reflected light beam is transmitted through the 3rd surface 5 to reach an image plane 6, thereby forming an image. The 1st surface 3 is a rotationally symmetrical surface such as a spherical surface and the 2nd surface 4 is rotationally asymmetrical.

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 has as its object to widen the effective area of the first surface having a transmitting action and a reflecting action near the pupil of an eccentric prism. An object of the present invention is to provide a decentered prism optical system whose surface is constituted by a rotationally 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 an eccentric prism optical system including an eccentric prism configured to be embedded with three or more transparent media, the eccentric prism may be configured to perform at least two internal reflections on at least two of the three surfaces so as to perform internal reflection at least twice. The two reflecting surfaces are formed at positions such that the light reflected by the two reflecting surfaces does not intersect inside the eccentric prism while being formed by the surfaces having the reflecting effect, Of the two surfaces having a reflective action, 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 the other one surface (the entire surface) The area where the light flux is transmitted and / or reflected in the area) is constituted by a rotationally symmetric surface having a rotationally symmetric axis in the effective plane, and a positive refracting power is applied to the entrance side or the exit side of the eccentric prism. Have Lens is characterized in that is arranged.

In this case, the rotationally symmetric surface of the decentered prism is
The eccentric prism is formed as a first surface having both a transmitting function of entering or emitting a light beam passing therethrough and a reflecting function of bending the light beam inside the eccentric prism, and the rotationally asymmetric surface of the eccentric prism is disposed to face the first surface. The second
A third surface, which is formed as a surface and further has a transmissive function of emitting or entering a light beam passing through the eccentric prism, is disposed at a position substantially perpendicular to the facing direction of the first surface and the second surface, At least the eccentric prism has a configuration including a first surface, a second surface, and a third surface, and the lens can be arranged on the incident side or the exit side of the first surface.

At this time, the first surface of the eccentric prism is formed so that the transmission function and the reflection function thereof overlap in at least a part of the effective plane, and at least a part of the decentered prism in the effective plane is effective. The reflection function in the area where the transmission function and the reflection function overlap can be configured to be the total reflection function.

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,
An optical path diagram when the decentered prism, which is a main part of the optical system of the present invention, is a simplest three-sided prism 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 eccentric prism 7 includes three surfaces 3, 4, and 5. In the eccentric prism 7, a light beam emitted from an object (not shown) first passes through the pupil 1 of the eccentric prism 7,
First surface 3 of eccentric prism 7 having transmission and reflection functions
Incident on. Then, the incident light is reflected in a direction approaching the pupil 1 by a second surface 4 which is a reflection surface having only a reflection effect on a side farther from the pupil 1, and has a transmission effect and a reflection arranged closer to the pupil 1. The light is reflected again in the direction away from the pupil 1 by the first surface 3 having an effect. Then, the reflected light ray is arranged at a position substantially perpendicular to the direction (Z-axis direction in the drawing) facing the first surface 3 and the second surface 4 (Y-axis direction in the drawing), and has only a transmitting action. The light passes through the three surfaces 5 and reaches the image surface 6 to form an image. Note that reference numeral 2 is an optical axis. As described above, the surface number of the eccentric prism 7 in the present invention is tracked in the order from the pupil 1 to the image plane 6 in principle.

However, FIG. 1 is merely an example, and the decentered prism 7 of the present invention has an optical surface of 4 as shown in FIG.
It may have a surface, or may have more than two reflections. FIG. 2A shows an eccentric prism 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,
The fourth surface 8 having a reflecting action may be a rotationally symmetric spherical surface or a rotationally symmetric aspherical surface, but is preferably constituted by an anamorphic surface or a rotationally asymmetrical aspherical surface having only 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.

[0011] Among at least three surfaces constituting such an eccentric prism, the first surface having a transmissive action and a reflective action arranged on the pupil side is constituted by a rotationally symmetric face, and a reflective action far from the pupil is provided. It is preferable that the second surface having only the surface be 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.

Further, in the present invention, as shown by a broken line in FIG. 1, the decentered prism 7 has the above-described structure, and a refracting lens system 9 is added to the object side of the decentered prism 7 to obtain a wide angle of view. Optical system can be configured. When the refractive lens system 9 is arranged between the object and the pupil 1, an optical system having a negative refractive power is arranged to reduce the height of the principal ray from the object to be incident on the eccentric prism 7, thereby achieving decentering. The prism 7 can be reduced in size, and at the same time, an optical system having a wide angle of view can be configured.

Further, by disposing a refractive lens system 9 having a positive refractive power between the pupil 1 and the eccentric prism 7 (in the case shown in FIG. 1), the principal ray passing through the pupil 1 is converged to By being incident on the eccentric prism 7, the eccentric prism 7 can be reduced in size, and at the same time, an optical system with a wide angle of view can be configured.

Further, in the present invention, the eccentric prism 7
When the refractive lens system 9 is disposed on the object side of the lens, the function of the cover glass can also be used for the refractive lens system 9, and it is not necessary to separately provide a cover glass. This is important in an optical system using the eccentric prism 7 as described above. Since the eccentric prism 7 is constituted by an eccentric rotationally asymmetric surface and a rotationally symmetric surface, a polyolefin resin (for example, “ZEONE” manufactured by Nippon Zeon Co., Ltd.) is usually used.
X ") or the like, it is necessary to provide a cover glass in front of the surface on the incident side, and the first surface, which is the surface on the incident side of the eccentric prism 7, in particular. Since the surface 3 is often a total reflection surface, it is not possible to provide a coating on that surface, so a cover glass must be provided in front of that surface. In the optical system, the function of the cover glass can also be used for the refractive lens system 9 and the cover glass can be omitted, so that the optical system can be lightened.

A coordinate system used in the following description will be described. As shown in FIG.
An axial principal ray that passes through the center of the pupil 1 and reaches the center of the image plane 6 (the image display element when used as an eyepiece optical system) exits the pupil 1 and the first surface of the eccentric prism optical system 10 (the refractive lens). An axis defined by a straight line (corresponding to the optical axis 2; when used as an eyepiece optical system, becomes an observer's visual axis) until it intersects the first surface of the system 9 is defined as a Z axis. An axis that is orthogonal and within the eccentric plane of each surface constituting the eccentric prism optical system 10 is defined as a Y axis, and an axis that is orthogonal to the Z axis and orthogonal to the Y axis is an X axis. The center of the pupil 1 is set as the origin of this coordinate system. The direction in which the on-axis principal ray reaches the image plane from the object point is the positive direction of the Z-axis, the direction in which the image plane 6 is located is the positive direction of the Y-axis, and the Y-axis and the Z-axis constitute a right-handed X. X direction of axis
The positive direction of the axis.

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

In the present invention, it is important that at least one of the at least three surfaces constituting the decentered prism is a rotationally symmetric surface. With a rotationally symmetric surface, the surface shape can be measured easily and in a short time by a rotationally symmetric aspherical interference measuring device as disclosed in JP-A-8-21712.

More preferably, the effective area is widest,
An eccentric prism that can easily evaluate the finished shape of a surface shape in a short time by configuring a surface having a transmission function and an internal reflection function on the side close to the pupil where the deterioration of aberration is relatively large as a rotationally symmetric surface. Has been successfully constructed.

Hereinafter, the decentered prism optical system of the present invention will be described as an image forming optical system. 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.
It is needless to say that the pupil of the observer can be positioned at the same time) and used as an eyepiece optical system. 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, 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.

[0022]

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

First, a second surface having only a reflecting action on the entire optical system of the present invention (hereinafter, the first surface, the second surface, etc. means the first surface, the second surface, etc. of the decentered prism unless otherwise specified. Is shown below. The second surface having only the reflection function of the present invention is eccentric, and its shape is a rotationally asymmetric surface shape having no rotationally symmetric axis both in-plane and out-of-plane. Since it is meaningless to derive the focal length, the focal length is defined as:

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

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

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

More preferably, it is important to satisfy the following condition: 1.0 <FA <1.1 (A-2)

Next, the refracting powers (powers) 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.

More preferably, 0.8 <| PxB | <1.2 (B-2) 0.8 <| PyC | <1.1 (C-2) Is preferably satisfied.

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

The second surface having only the reflecting function is a surface arranged eccentrically, and if this surface is constituted by a rotationally symmetric surface, large astigmatism, coma, etc., including image distortion, will occur. It is impossible to satisfactorily correct aberrations.
For this reason, it is important to form the second surface having only the reflection function as a rotationally asymmetric surface. However, if the second surface has a rotationally symmetric surface, astigmatism occurring on this surface increases, and It becomes impossible to correct in terms of Therefore, in order to correct these, 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. Aberration is well corrected, and it is possible to obtain an image without astigmatism or to observe an observation image even on the axis. 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 <1.05 (D-2)

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 E, it is important to satisfy the following condition: -0.05 <CyE <0.5 (E-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 eccentric prism optical system in which the first surface having the reflection function and the transmission function is constituted by a rotationally symmetric surface as in the present invention and the manufacturability of the eccentric prism is improved, it is necessary to correct this image distortion on another surface. Is the third one having only the transmission effect closest to the image.
Unless correction is performed on the surface, 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 more preferable to satisfy the following condition: 0 <CyE <0.3 (E-2) for aberration correction.

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

Next, a 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 CxF
It is important to satisfy the following condition: -0.01 <CxF <0.1 (F-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, the condition of -0.01 <CxF <0.05 (F-2) is satisfied from the viewpoint of aberration correction.

More preferably, -0.001 <CxF <0.03 (F-3) is satisfied from the viewpoint of aberration correction.

Next, when a straight line is displayed at the center of the screen,
The image distortion that is observed by bending upward and downward in a bow will be described. The following conditional expression relates to, for example, a bow-shaped rotationally asymmetric image distortion that is bowed and curved when a horizontal line is captured.

FIG. 18 (a) is a perspective view, and FIG.
As shown in the projection on the Z plane, the normal line n 'of the rotationally asymmetric surface at the point where the principal ray of the maximum angle of view in the X direction intersects the rotationally asymmetric surface A, and the axial principal ray are the rotationally asymmetric surface. Assuming that the angle between the normal line n of the rotationally asymmetric surface at the point intersecting with A in the YZ plane is DY, -0.1 <| DY | <5 (°) (G-1) It is important to satisfy the following conditions. If the lower limit of -0.1 of the above conditional expression is exceeded, bow-shaped image distortion cannot be corrected. If the upper limit of 5 is exceeded, bow-shaped image distortion will be overcorrected, and in either case, the image will be bowed. More preferably, it is preferable to satisfy the following condition: -0.05 <| DY | <1 (°) (G-2)

More preferably, the following condition is satisfied: 0 <| DY | <0.5 (°) (G-3)

Next, the focal length of a lens system having a positive refractive power disposed between the pupil and the decentered prism will be described. The following conditional expression is necessary for converging the light beam having a wide angle of view incident by the lens system having the positive refracting power and making the decentered prism compact. When the focal length of the lens system disposed between the pupil and the eccentric prism is F, and the focal length in the Y direction of the entire optical system between the eccentric prism and the lens system having a positive refractive power is Fy, 1 It is important to satisfy the following condition: 1 <F / Fy <10000 (H-1) If the lower limit of 1.1 to the above conditional expression is exceeded, the refractive power borne by the lens system becomes too large compared to the refractive power borne by the eccentric prism,
Aberrations, particularly field curvature, coma, and chromatic aberration, which occur in the lens system disposed between the pupil, which is a refracting optical system, and the decentered prism become too large, and good results cannot be obtained as aberration performance. On the other hand, when the value exceeds the upper limit of 10,000, the focal length of the refractive lens system becomes too long, the convergence of light rays of the refractive lens system becomes weak, and the eccentric prism becomes large or the angle of view cannot be made large. I will.

It is more preferable that the following condition is satisfied: 1.5 <F / Fy <10000 (H-2)

More preferably, it is preferable to satisfy the following condition: 2 <F / Fy <10000 (H-3).

More preferably, when 2 <F / Fy <3 (H-4), magnification chromatic aberration generated in the refractive lens system is increased. It is preferable to use them in combination.

Now, from the above conditions (A-1) to (G-
Regarding 3), the first surface having the reflection function and the transmission function of the eccentric prism is constituted by a rotationally symmetric surface, and the second surface having only the reflection function has no rotationally symmetric axis both in-plane and out-of-plane. It is preferable to form a plane-symmetric free-form surface having only one plane of symmetry. Furthermore, not only a plane-symmetric free-form surface but also an anamorphic surface having no rotational symmetry axis both in-plane and out-of-plane, that is, a rotation having no rotational symmetry axis in-plane and out-of-plane. The present invention can be applied to any case having an asymmetric surface shape.

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

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

Therefore, as the material of the eccentric prism, it is desirable to use a material (polyolefin-based resin: for example, "ZEONEX" manufactured by Nippon Zeon Co., Ltd.) which is hardly affected by a change in humidity and has a small coefficient of linear expansion. Specifically, it is desirable that the water absorption rate α of the material satisfies the following condition: 0 <α <0.1 (%) (I-1). Exceeding the upper and lower limits of this conditional expression undesirably leads to deterioration of aberration performance.

Further, such a material having a low coefficient of linear expansion of water is soft and easily damaged as compared with glass or the like. Therefore, for example, when used as an image display device mounted on the head or face, when the first surface of the eccentric prism on the observer's eyeball side comes into contact with the outside world, it is necessary to apply a cover coating to that surface. But,
The first surface is desirably used as a total reflection surface in view of the characteristics of the decentered prism optical system of the present invention from the viewpoint of preventing a reduction in the amount of light. However, if the first surface is coated, the total reflection effect is lost. Will be lost. Therefore, it is desirable to arrange a cover glass between the first surface and the observer's eyeball. In the present invention, the positive lens satisfies this need. In addition to the action of expanding the angle of view, the positive lens also functions as the above-mentioned cover glass, reducing the number of parts and reducing the weight. It is also useful for

[0054]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments 1 to 6 of the decentered prism optical system according to the present invention will be described below. In the configuration parameters of each embodiment described later, as shown in FIG. 1, the center of the pupil 1 of the decentered optical system 10 is set as the origin of the optical system, and the optical axis 2 passes 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 defined as a ray, and the direction in the plane where the ray is bent by the optical system 10 is orthogonal to the Z axis and passes through the center of the pupil 1. , The direction passing through the center of the pupil 1 is defined as the X-axis direction, the direction from the pupil 1 toward the optical system 10 is defined as the positive direction of the Z-axis,
Is defined as the positive direction of the Y axis, and the direction forming the right-handed system with the Y axis, the 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 10 from the object side of the optical system 10 on the pupil 1 side.

Then, for a plane with eccentricity, the amount of eccentricity in the X-axis direction, Y-axis direction, and Z-axis direction from the center of the pupil 1 which is the origin of the optical system 10 at the top of the surface ( X, y, and z) and the inclination angles (α, respectively, of the central axes of the surfaces (for free-form surfaces, the Z-axis of the following equation (a)) about the X-axis, the Y-axis, and the Z-axis, respectively. β, γ) 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 rotationally asymmetric surface is defined by the following equation. The Z axis of the definition formula is the axis of the rotationally asymmetric surface. Z = Σ _n Σ _m proviso C ^_nm X ⁿ Y _nm, ⁿ is 0~k of sigma _n is sigma, m of sigma _m is sigma is 0~n
Represents

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

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

Z = C ₂ + C ₃ Y + C ₄ X + C ₅ Y ² + C ₆ YX + C ₇ X ² + C ₈ Y ³ + C ₉ Y ² X + C ₁₀ YX ² + C ₁₁ X ³ + C ₁₂ Y ⁴ + C ₁₃ Y ³ X + C ₁₄ Y ^{2 _{X 2 + C 15 YX 3 +}} C 16 X 4 + C 17 Y 5 + C 18 Y 4 X + C 19 Y 3 X 2 + C 20 Y 2 X 3 + C 21 YX 4 + C 22 X 5 + C 23 Y 6 + C 24 Y 5 X + C 25 Y 4 ^{_{X 2 + C 26 Y 3 X}} 3 + C 27 Y 2 X 4 + C 28 YX 5 + C 29 X 6 + C 30 Y 7 + C 31 Y 6 X + C 32 Y 5 X 2 + C 33 Y 4 X 3 + C 34 Y 3 X 4 + C 35 Y ² X ⁵ + C ₃₆ YX ⁶ + C ₃₇ X ⁷ ... (A) Then, the coefficients C ₄ , C ₆ , C _9.
(Examples described later). In the parameters of the configuration described later, a coefficient relating to an aspheric surface not described is 0.

Another definition of a plane-symmetric free-form surface is a Zernike polynomial. The shape of this surface is defined by the following equation (b). 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) (b) 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.

[0061] Examples represent other surfaces usable in the present invention, the above defined formula _{(Z = Σ n Σ m C} nm X
ⁿ Y ^nm ) in the same manner as in equation (a),
In the case of representing a surface where k = 7, it can be expanded as in the following equation (c).

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

Z = (Cx · X ² + Cy · Y ² ) / [1+
{1- (1 + Kx) Cx ² · X ² − (1 + Ky) Cy ²
・ Y ² ｝ ^1/2 ] + {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 (d).

Z = (Cx · X ² + Cy · Y ² ) / [1+ {1− (1 + Kx) Cx ² · X ² − (1 + Ky) Cy ² · Y ² ｝ ^1/2 ] + R1} (1-P1) ^{X 2 + (1 + P1)} Y 2} 2 + R2 {(1-P2) X 2 + (1 + P2) Y 2} 3 + R3 {(1-P3) X 2 + (1 + P3) Y 2} 4 + R4 {(1-P4 ) X ² + (1 + P4) Y ² ｝ ⁵ (d) where Z is the amount of deviation 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, 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 shape of the rotationally symmetric aspherical surface is defined by the following equation. The Z axis in the definition formula is the axis of the rotationally symmetric aspherical surface. ^{Z = (Y 2 / R)} / [1+ {1-P (Y 2 / R 2)} 1/2] + A 4 Y 4 + A 6 Y 6 + A 8 Y 8 + A 10 Y 10 ··· ··· ( e) where Y is the direction perpendicular to Z, R is the paraxial radius of curvature, P is the conic coefficient, and A ₄ , A ₆ , A ₈ and A ₁₀ are the aspheric coefficients.

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

Next, FIGS. 3 to 8 show Examples 1 to 6, respectively.
3 is a YZ sectional view including the optical axis 2 of the eccentric prism optical system 10 of FIG. The eccentric prism 7 of any of the embodiments includes three surfaces 3, 4, and 5, as in the case of FIG.
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) is
First, the light passes through the pupil 1 of the optical system 10 through the positive single lens 9 ′, enters the first surface 3 having a transmissive action and a reflective action, and enters the decentered prism 7. Surface 4 which is a reflecting surface having only a reflecting action on the side farther from
Is reflected in the direction approaching the pupil 1, and this time the pupil 1
The reflected light is reflected again in a direction away from, and the reflected light passes through the third surface 5 having only a transmitting action, reaches the image surface 6, and forms an image. In all the embodiments, the positive single lens 9 'is a decentered plano-convex lens, and the decentered prism 7
In Examples 1-2, 4-6, the first surface 3 is the pupil 1
In the third embodiment, the first surface 3 is a rotationally symmetric aspheric surface defined by the above-described formula (e), which is decentered with the concave surface facing the pupil 1 side. In the first to fifth embodiments, the second surface 4 and the third surface 5 are composed of free-form surfaces defined by the above-described formula (a), and in the sixth embodiment, the second surface 4 is ), And the third surface is a spherical surface.

In the first embodiment, the horizontal angle of view is 38 °, the vertical angle of view is 29.0 °, the image size is 14.4 × 10.7 mm,
The pupil diameter is 4 mm. Examples 2 to 4 have a horizontal angle of view of 40 °,
Vertical angle of view 30.5 °, image size 14.4 × 10.7m
m, pupil diameter 4 mm. In the fifth and sixth embodiments, the horizontal angle of view 48
°, vertical angle of view 36.9 °, image size 21.1 × 15.
8 mm, pupil diameter 4 mm.

[0069] Incidentally, decentered prism 7 all the refractive index of Example 1 to 6 (n _d) 1.5254 of KK Nippon Zeon "ZEO
The water absorption α of this “ZEONEX” is 0.01%.

Hereinafter, the structural parameters of the above-described first to sixth embodiments will be described. Example 1 Surface number Curvature radius Spacing Eccentricity Refractive index Abbe number Object plane ∞ ∞ 1 ∞ 2 ∞ Eccentricity (1) 1.4922 57.5 3 -35.963 Eccentricity (2) 4 -196.457 Eccentricity (3) 1.5254 56.2 5 Free-form surface [1] Eccentricity (4) 1.5254 56.2 6 -196.457 Eccentricity (3) 1.5254 56.2 7 Free-form surface [2] Eccentricity (5) Image surface ∞ Eccentricity (6) Free-form surface [1] C ₅ -7.2660 × 10 ^-3 C ₇ -7.4223 × 10 ^{_{-3 C 8 3.3356 × 10 -5 C}} 10 1.2235 × 10 -5 C 12 -3.9327 × 10 -7 C 14 -1.2063 × 10 -6 C 16 -7.1374 × 10 -7 C 17 1.3838 × 10 -7 C 19 - 2.1827 × 10 ^-8 C ₂₁ 2.9995 × 10 ^-8 C ₂₃ 9.7004 × 10 ^-10 C ₂₅ -1.7016 × 10 ^-9 C ₂₇ 2.5056 × 10 ^-9 C ₂₉ 2.1061 × 10 ^-10 C ₃₀ -4.1940 × 10 ^-10 C ₃₂ -2.1214 × 10 ^-10 C ₃₄ 8.2993 × 10 ^-10 C ₃₆ -3.3050 × 10 ^-10 Free-form surface [2] C ₅ -1.2614 × 10 ^-2 C ₇ -6.8925 × 10 ^-4 Eccentricity (1) x 0.000 y 0.000 z 23.000 α 8.00 β 0.00 γ 0.00 Eccentricity (2) x 0.000 y 0.000 z 25.174 α 8.00 β 0.00 γ 0.00 Eccentricity (3) x 0.000 y 6.745 z 24.085 α 17.36 β 0.00 γ 0.00 Eccentricity (4) x 0.000 y 0. 840 z 34.028 α -12.70 β 0.00 γ 0.00 eccentricity (5) x 0.000 y 16.738 z 28.656 α 75.93 β 0.00 γ 0.00 eccentricity (6) x 0.000 y 20.545 z 30.873 α 60.19 β 0.00 γ 0.00.

Example 2 Surface Number Curvature Radius Interval Eccentricity Refractive Index Abbe Number Object Surface ∞ ∞ 1 ∞ 2 ∞ Eccentricity (1) 1.4922 57.5 3 -27.659 Eccentricity (2) 4 -149.496 Eccentricity (3) 1.5254 56.2 5 Free-form surface [ 1] eccentricity (4) 1.5254 56.2 6 -149.496 eccentric (3) 1.5254 56.2 7 the free curved surface [2] eccentricity (5) image surface ∞ eccentricity (6) free curved surface _{[1] C 5 -7.9104 × 10} -3 C 7 - 7.9974 × 10 ^-3 C ₈ 3.9 130 × 10 ^-5 C ₁₀ 3.6 289 × 10 ^-6 C ₁₂ -1.0272 × 10 ^-6 C ₁₄ -1.8685 × 10 ^-6 C ₁₆ -7.4081 × 10 ^-7 C ₁₇ 8.8993 × 10 ^-8 C ₁₉ -3.7196 × 10 ^-8 C ₂₁ 9.0376 × 10 ^-8 C ₂₃ 5.8432 × 10 ^-10 C ₂₅ -3.6056 × 10 ^-9 C ₂₇ 3.7493 × 10 ^-9 C ₂₉ -2.0178 × 10 ^-11 C ₃₀ -9.0053 × 10 ^-11 C ₃₂ -3.1608 × 10 ^-10 C ₃₄ 1.0947 × 10 ^-9 C ₃₆ -7.0993 × 10 ^-10 Free-form surface [2] C ₅ -1.2946 × 10 ^-2 C ₇ 8.9577 × 10 ^-3 Eccentricity (1) x 0.000 y 0.000 z 23.000 α 8.00 β 0.00 γ 0.00 Eccentricity (2) x 0.000 y 0.000 z 25.544 α 8.00 β 0.00 γ 0.00 Eccentricity (3) x 0.000 y 6.523 z 24.321 α 16.51 β 0.00 γ 0.00 Eccentricity (4) x 0.000 0.714 z 33.213 α -14.19 β 0.00 γ 0.00 eccentricity (5) x 0.000 y 15.307 z 28.201 α 71.70 β 0.00 γ 0.00 eccentricity (6) x 0.000 y 18.987 z 30.056 α 62.17 β 0.00 γ 0.00.

Example 3 Surface Number Curvature Radius Interval Eccentricity Refractive Index Abbe Number Object Surface ∞ ∞ 1 ∞ 2 ∞ Eccentricity (1) 1.4922 57.5 3 -23.410 Eccentricity (2) 4 -143.048 Eccentricity (3) 1.5254 56.2 P 1 A ₄ -0.678231 × 10 ^-5 A ₆ -0.718263 × 10 ^-8 5 Free-form surface [1] Eccentricity (4) 1.5254 56.2 6 -143.048 Eccentricity (3) 1.5254 56.2 P 1 A ₄ -0.678231 × 10 ^-5 A ₆ -0.718263 × 10 ^-8 7 Free-form surface [2] Eccentricity (5) Image surface 偏 Eccentricity (6) Free-form surface [1] C ₅ -7.6312 × 10 ^-3 C ₇ -7.7867 × 10 ^-3 C ₈ 6.8800 × 10 ^-5 C ₁₀ 4.9872 × 10 ^-5 C ₁₂ -3.5 180 × 10 ^-6 C ₁₄ -6.5043 × 10 ^-6 C ₁₆ -2.2855 × 10 ^-6 C ₁₇ 2.8747 × 10 ^-7 C ₁₉ 2.2971 × 10 ^-7 C ₂₁ 1.4477 × 10 ^-7 C ₂₃ -1.3241 × 10 ^-9 C ₂₅ -1.3282 × 10 ^-8 C ₂₇ 2.8 300 × 10 ^-9 C ₂₉ 2.0011 × 10 ^-10 C ₃₀ 1.8023 × 10 ^-10 C ₃₂ -4.8811 × 10 ^-10 C ₃₄ 1.3959 × 10 ^-9 C ₃₆ -5.2773 × 10 ^-10 Free-form surface [2] C ₅ -3.0658 × 10 ^-2 C ₇ 2.3240 × 10 ^-3 Eccentricity (1) x 0.000 y 0.000 z 23.000 α 8.00 β 0.00 γ 0.00 Eccentricity (2) x 0.000 y 0.000 z 25.977 α 8.00 β 0.00 γ 0.00 Eccentricity (3) x 0.000 y 7.704 z 25.746 α 7.07 β 0.00 γ 0.00 Eccentricity (4) x 0.000 y 0.278 z 34.466 α -19.70 β 0.00 γ 0.00 Eccentricity (5) x 0.000 y 15.617 z 31.379 α 58.30 β 0.00 γ 0.00 Eccentricity (6) x 0.000 y 17.934 z 33.152 α 53.38 β 0.00 γ 0.00.

Example 4 Surface Number Curvature Radius Interval Eccentricity Refractive Index Abbe Number Object Surface ∞ ∞ 1 ∞ 2 ∞ Eccentricity (1) 1.4922 57.5 3 -41.999 Eccentricity (2) 4 -138.539 Eccentricity (3) 1.5254 56.2 5 Free-form surface [ 1] eccentricity (4) 1.5254 56.2 6 -138.539 eccentric (3) 1.5254 56.2 7 the free curved surface [2] eccentricity (5) image surface ∞ eccentricity (6) free curved surface _{[1] C 5 -9.0433 × 10} -3 C 7 - 9.2347 × 10 ^-3 C ₈ 5.1854 × 10 ^-5 C ₁₀ 3.3087 × 10 ^-6 C ₁₂ 7.2992 × 10 ^-6 C ₁₄ 1.6 139 × 10 ^-5 C ₁₆ 9.6 910 × 10 ^-6 C ₁₇ -7.1365 × 10 ^-8 C _{19 ^{1.0603 × 10 -7 C 21 1.7643 ×}} 10 -7 C 23 -8.0046 × 10 -9 C 25 -3.8685 × 10 -8 C 27 -3.5814 × 10 -8 C 29 -1.6736 × 10 -8 C 30 1.0570 × 10 - ⁹ C ₃₂ -7.5238 × 10 ^-10 C ₃₄ 5.2872 × 10 ^-10 C ₃₆ -7.2607 × 10 ^-10 Free-form surface [2] C ₅ -1.6343 × 10 ^-2 C ₇ 3.7710 × 10 ^-3 Eccentricity (1) x 0.000 y 0.000 z 24.518 α 8.00 β 0.00 γ 0.00 Eccentricity (2) x 0.000 y 0.000 z 27.440 α 8.00 β 0.00 γ 0.00 Eccentricity (3) x 0.000 y 6.782 z 26.229 α 15.69 β 0.00 γ 0.00 Eccentricity (4) x 0.000 y 0 . 699 z 35.260 α -14.78 β 0.00 γ 0.00 Eccentricity (5) x 0.000 y 15.855 z 30.393 α 71.61 β 0.00 γ 0.00 Eccentricity (6) x 0.000 y 19.082 z 32.107 α 63.24 β 0.00 γ 0.00.

Example 5 Surface Number Curvature Radius Interval Eccentricity Refractive Index Abbe Number Object Surface ∞ ∞ 1 ∞ 2 ∞ Eccentricity (1) 1.4922 57.5 3 -37.874 Eccentricity (2) 4 -373.356 Eccentricity (3) 1.5254 56.2 5 Free-form surface [ 1] eccentricity (4) 1.5254 56.2 6 -373.356 eccentric (3) 1.5254 56.2 7 the free curved surface [2] eccentricity (5) image surface ∞ eccentricity (6) free curved surface _{[1] C 5 -5.3785 × 10} -3 C 7 - 5.4185 × 10 ^-3 C ₈ 1.5217 × 10 ^-5 C ₁₀ 1.8 262 × 10 ^-5 C ₁₂ 4.0012 × 10 ^-7 C ₁₄ 7.4712 × 10 ^-7 C ₁₆ 1.0251 × 10 ^-7 C ₁₇ 9.4919 × 10 ^-8 C ₁₉ 7.8271 × 10 ^-8 C ₂₁ 4.6068 × 10 ^-8 C ₂₃ -1.6579 × 10 ^-10 C ₂₅ 5.1498 × 10 ^-10 C ₂₇ -3.8477 × 10 ^-9 C ₂₉ -3.6899 × 10 ^-10 C ₃₀ -1.9081 × 10 ^-10 C ₃₂ 5.8686 × 10 ^-11 C ₃₄ -2.3984 × 10 ^-10 C ₃₆ -9.6057 × 10 ^-11 Free-form surface [2] C ₅ -1.8133 × 10 ^-2 C ₇ -2.5601 × 10 ^-3 C ₁₀ -2.9938 × 10 ^-3 C ₁₄ 2.2287 × 10 ^-4 C ₁₉ -5.8022 × 10 ^-6 C ₂₁ 2.5677 × 10 ^-6 Eccentricity (1) x 0.000 y 0.000 z 23.000 α 8.00 β 0.00 γ 0.00 Eccentricity (2) x 0.000 y 0.000 z 25.777 α 8.00 β 0.00 γ 0.00 Heart (3) x 0.000 y 7.743 z 24.367 α 20.08 β 0.00 γ 0.00 Eccentricity (4) x 0.000 y 1.861 z 37.783 α -9.45 β 0.00 γ 0.00 Eccentricity (5) x 0.000 y 18.771 z 36.281 α 59.55 β 0.00 γ 0.00 Eccentricity (6) x 0.000 y 24.346 z 31.737 α 57.60 β 0.00 γ 0.00.

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

FIG. 9 is an aberration diagram showing image distortion of the first embodiment. In this aberration diagram, the vertical axis represents the image height in the X direction, and the horizontal axis represents the image height in the Y direction. FIG. 1 is a lateral aberration diagram of the first embodiment.
0 is shown. In this lateral aberration diagram, 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.

Hereinafter, parameter values relating to the conditional expressions (A-1) to (H-1) in Examples 1 to 6 of the present invention will be shown. Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 (A-1) 1.03591 1.03451 1.04142 1.01647 1.02169 1.02889 (B-1) 0.96941 0.99303 0.93780 1.09170 0.81502 0.87536 (C-1) 0.91610 0.94946 0.88252 1.05176 0.79386 0.85141 (D-1) 1.02151 1.011 1.02038 1.02116 1.00486 0.99926 (E-1) 0.09459 0.10135 0.25116 0.10847 0.09464 0.07108 (F-1) 0.00650 -0.00009 0.04298 -0.00424 0.02633 0.00185 (G-1) 0.00114 0.00056 0.00578 0.00149 0.00234 0.00138 (H- 1) 3.38092 2.779477 2.45676
4.37771 3.112714 3.20561.

The eccentric prism optical system of the present invention as described above can be used for an image display device. As an example, FIG. 11 shows a state in which the head-mounted image display device is mounted on the observer's head, and FIG. 12 is a cross-sectional view thereof. This configuration uses the decentered prism optical system of the present invention as the eyepiece optical system 100 as shown in FIG.
By preparing a pair consisting of 0 and the image display element 101 on the left and right, and supporting them at a distance of the eye distance,
It is configured as a portable image display device 102 such as a stationary or head mounted image display device that can be observed with both eyes.

That is, the display device main body 102 is provided with a pair of right and left 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. 11, the display device main body 102 is provided with a temporal frame 103 as shown in FIG. 11 so that the display device main body 102 can be held in front of the observer. .

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

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

Further, the eccentric prism optical system of the present invention can 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. 14, the decentered prism optical system of the present invention is provided 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. 5, an eccentric prism optical system 201 and a roof prism 203 having a roof surface 202 are arranged as means for erecting an image formed by the objective lens group 200 of the finder optical system. Is guided to the observer's eyeball 205 by the eyepiece 204. With this configuration, the height direction can be made lower than that of the conventional Porro prism, and compactness can be achieved. In the drawing, Le is the optical axis of the finder optical system.

Further, an objective lens of a rigid endoscope that transmits an image to an eyepiece using a relay lens, an objective lens of a flexible endoscope that transmits an image to the eyepiece using an optical fiber bundle, and a CCD. It can also be used for an objective lens of an electronic endoscope that receives an image. One example is shown in FIGS.
FIG. FIG. 16 shows a rigid endoscope (a so-called rigid endoscope).
FIG. 1 is an overall configuration diagram of an endoscope apparatus that uses an electronic device. An endoscope device 30 shown in FIG. 16 includes an endoscope 20 having an insertion section 22 in which an objective lens and an illumination optical system are provided, a camera 24, a monitor 25, and a light source device 27. Endoscope 20
As shown in FIG. 17, an eccentric prism optical system 31 according to the present invention (a negative lens is arranged on the incident side of the eccentric prism) is used at the distal end 21 of the insertion portion 22 as shown in FIG. An objective lens 32 and a light guide 33 for irradiating the visual field direction are incorporated. In the insertion portion 22,
Subsequent to the objective lens 32, a relay lens system, which is an optical system for transmitting an image or a pupil, is provided. An eyepiece optical system (not shown) is disposed on the base 23 of the endoscope 20, and a camera 24 as an imaging unit can be attached after the connection optical system. Here, the base 23 and the camera 24 of the endoscope 20 are configured as an integral type or a detachable type. The subject imaged by the camera 24 is finally displayed on the monitor 25 as an endoscope image so as to be observable to an observer. The illumination light from the light source device 27 is
To illuminate the viewing direction through the base 23, the insertion part 22, and the tip part 21.

The above-described decentered prism optical system of the present invention can be constituted, for example, as follows. [1] An eccentric prism optical system including an eccentric prism 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 prism forms at least two of the three surfaces with a reflective surface so as to perform at least two internal reflections, and the light reflected by the two reflective surfaces. Are arranged such that they do not intersect inside the eccentric prism, and the two surfaces having the reflecting action are rotationally symmetric both in-plane and out-of-plane. It is formed of a rotationally asymmetric surface having no axis, and the shape of at least the effective surface of the other surface (the region through which the light beam is transmitted and / or reflected in the entire surface) has a rotationally symmetric axis within the effective surface. Rotation with An eccentric prism optical system comprising a symmetrical surface, and a lens having a positive refracting power disposed on an entrance side or an exit side of the eccentric prism.

[2] In the decentered prism optical system according to the above [1], the rotationally symmetric surface of the decentered prism is
Formed as a first surface having both a transmissive function of entering or emitting a light beam passing through the eccentric prism and a reflecting function of bending the light beam inside the eccentric prism,
The rotationally asymmetric surface of the eccentric prism is formed as a second surface opposed to the first surface, and a third surface having a transmitting function of emitting or entering a light beam passing through the eccentric prism is the third surface. The eccentric prism is disposed at a position substantially perpendicular to a direction in which one surface and the second surface oppose each other, and at least the eccentric prism includes the first surface, the second surface, and the third surface, 2. The decentered prism optical system according to claim 1, wherein a lens is disposed on an incident side or an exit side of said first surface.

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

[4] The eccentric prism optical system according to the above [2] or [3], wherein
A decentered prism optical system, wherein the rotationally symmetric 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 the second surface of the decentered prism is formed by an anamorphic surface.

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

[7] Any one of the above [2] to [4]
3. The decentered prism optical system according to claim 1, wherein the second surface of the decentered prism is formed of a rotationally asymmetric surface having only one symmetric surface.

[8] In the decentered prism optical system according to the above [7], the rotationally symmetric axis of the first surface is located within 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 as described above.

[0092]

[9] Any one of the above [2] to [8]
3. The eccentric prism optical system according to claim 1, wherein a light beam enters from the third surface of the eccentric prism, 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 arranged such that the reflected light beam 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:

[10] The above

[9] In the eccentric prism optical system according to [9], the third surface of the eccentric prism is arranged at a position where a light beam from a unit for displaying an image is incident, and the first surface is emitted from the first surface. The light beam is arranged at a position where it is guided to the observer's eyeball through the lens having the positive refractive power, and is used for an image observation device that enables observation of an image formed by the light beam. Decentered prism optical system.

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

[12] In the eccentric prism optical system according to the above [11], the first surface is arranged at a position where a light beam from an object enters through the lens having the positive refractive power, and The three surfaces are arranged at positions where the light beam emitted from the third surface is guided to the observer's eyeball, and are used for an image observation device that enables an image formed by the light beam to be observed. Eccentric prism optical system.

[13] In the eccentric prism optical system according to the above [11], the first surface is disposed at a position where a light beam from an object enters through the lens having the positive refracting power, and The three surfaces are arranged at positions where a light beam emitted from the third surface is guided to a means for receiving an object image, and are used for a photographing optical device capable of photographing an object image formed by the light beam. An eccentric prism optical system characterized by the following.

[14] In the decentered prism optical system according to any one of the above [2] to [8], an axial chief ray passing through the center of a pupil of the decentered prism optical system and reaching the center of an image plane is formed. An axis defined by a straight line extending from the pupil and intersecting the first surface of the lens having the positive refracting power is defined as a Z axis, and each of the surfaces orthogonal to the Z axis and constituting the eccentric prism optical system is defined as an axis. An eccentric prism optical system characterized by satisfying the following condition when an axis in the eccentric plane 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. 0.7 <FA <1.3 (A-1) However, the light passes through a point of a small amount H in the X-axis direction from the pupil center in parallel with the axial principal ray and in parallel with the axial principal ray. NA of an emitted light ray when a light ray incident on the optical system is traced.
The value obtained by dividing (the value of the sine of the angle formed by the on-axis principal ray) by the above H is defined as the focal length Fx of the entire optical system in the X direction. The value obtained by dividing the NA of the exit ray (the value of the sin of the angle formed with the axial principal ray) when the ray incident on the optical system in parallel with the principal ray by the ray tracing is divided by the H is used in the Y direction of the entire optical system. The focal length is defined as Fy, and Fx / Fy is defined as FA.

[15] [2] to [8], [1]
4] The decentered prism optical system according to any one of
An axis defined by a straight line passing through the center of the pupil of the decentered prism optical system and reaching the center of the image plane until the axial principal ray exits the pupil and intersects the first surface of the lens having positive refractive power. 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 an axis orthogonal to the Z axis and orthogonal to the Y axis is defined as an X axis. A decentered prism optical system which satisfies the following condition when defined. 0.8 <| PxB | <1.3 (B-1) However, the light passes through a point of a small amount H in the X-axis direction from the pupil center in parallel with the on-axis principal ray, and NA of the exit ray when the ray incident on the optical system is traced in parallel
The value obtained by dividing (the value of the sine of the angle formed by the on-axis principal ray) by the above H is defined as the focal length Fx of the entire optical system in the X direction. The value obtained by dividing the NA of the exit ray (the value of the sin of the angle formed with the axial principal ray) when the ray incident on the optical system in parallel with the principal ray by the ray tracing is divided by the H is used in the Y direction of the entire optical system. The focal length Fy is defined as the refractive power (power) in the X and Y directions of the surface at the position where the axial principal ray hits the second surface, respectively, Px
n and Pyn, and the reciprocals of the focal length Fx in the X direction and the focal length Fy in the Y direction are Px and Py, respectively, and Pxn
/ Px is set to PxB.

[16] [2] to [8], [1]
4] The decentered prism optical system according to any one of
An axis defined by a straight line passing through the center of the pupil of the decentered prism optical system and reaching the center of the image plane until the axial principal ray exits the pupil and intersects the first surface of the lens having positive refractive power. 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 an axis orthogonal to the Z axis and orthogonal to the Y axis is defined as an X axis. A decentered prism optical system which satisfies the following condition when defined. 0.8 <| PyC | <1.3 (C-1) However, the light passes through a point of a small amount H in the X-axis direction from the pupil center in parallel with the on-axis principal ray. NA of the exit ray when the ray incident on the optical system is traced in parallel
The value obtained by dividing (the value of the sine of the angle formed by the on-axis principal ray) by the above H is defined as the focal length Fx of the entire optical system in the X direction. The value obtained by dividing the NA of the exit ray (the value of the sin of the angle formed with the axial principal ray) when the ray incident on the optical system in parallel with the principal ray by the ray tracing is divided by the H is used in the Y direction of the entire optical system. The focal length Fy is defined as the refractive power (power) in the X and Y directions of the surface at the position where the axial principal ray hits the second surface, respectively, Px
n and Pyn, and the reciprocals of the focal length Fx in the X direction and the focal length Fy in the Y direction are Px and Py, respectively, and Pyn
/ Py is PyC.

[17] [2] to [8], [1]
The decentered prism optical system according to any one of [4] to [16], wherein an axial principal ray that passes through the center of the pupil of the decentered prism optical system and reaches the center of the image plane exits the pupil, and the positive refraction occurs. An axis defined by a straight line that intersects the first surface of the lens having power 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 perpendicular to the Z axis and orthogonal to the Y axis is defined as an X axis, wherein the following condition is satisfied. 0.8 <CxyD <1.2 (D-1) Here, the curvature Cx2 in the X direction including the normal of the surface at the position where the axial principal ray hits the second surface, and the curvature in the Y direction The ratio Cx2 / Cy2 to Cy2 is defined as CxyD.

[18] [2] to [8], [1]
In the eccentric prism optical system according to any one of [4] to [17], an on-axis 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 is positively refracted. An axis defined by a straight line that intersects the first surface of the lens having power 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 perpendicular to the Z axis and orthogonal to the Y axis is defined as an X axis, wherein the following condition is satisfied. −0.05 <CyE <0.5 (E-1) However, the light passes through a point of minute 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.
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 CyE.

[19] The above [2] to [8], [1]
In the eccentric prism optical system according to any one of [4] to [18], an axial principal ray which passes through the center of the pupil of the eccentric prism optical system and reaches the center of the image plane exits the pupil, and the positive refraction occurs. An axis defined by a straight line that intersects the first surface of the lens having power 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 perpendicular to the Z axis and orthogonal to the Y axis is defined as an X axis, wherein the following condition is satisfied. -0.01 <CxF <0.1 (F-1) However, the light passes through a point of minute 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 by x is defined as CxF.

[20] [2] to [8], [1]
In the eccentric prism optical system according to any one of [4] to [19], an axial chief 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 is positively refracted. An axis defined by a straight line that intersects the first surface of the lens having power 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 perpendicular to the Z axis and orthogonal to the Y axis is defined as an X axis, wherein the following condition is satisfied. −0.1 <| DY | <5 (°) (G-1) where the normal to the plane at the point where the principal ray having the maximum angle of view in the X direction intersects the second plane and the axis The angle between the point at which the upper principal ray intersects the second surface and the normal to that surface in the YZ plane is DY.

[21] [2] to [8], [1]
In the eccentric prism optical system according to any one of 4) to [20], an axial principal ray that passes through the center of the pupil of the eccentric prism optical system and reaches the center of the image plane exits the pupil and the positive refraction. An axis defined by a straight line that intersects the first surface of the lens having power 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 perpendicular to the Z axis and orthogonal to the Y axis is defined as an X axis, wherein the following condition is satisfied. 1.1 <F / Fy <10000 (H-1) where F is the focal length of the lens having a positive refractive power, and is a small amount in the Y-axis direction from the pupil center in parallel with the axial principal ray. The NA of the exit ray (the value of the sin of the angle formed with the axial principal ray) when the ray passing through the point H and entering the optical system parallel to the axial principal ray was traced was divided by the H. Let the value be the focal length Fy of the entire optical system in the Y direction.

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

[23] The decentered prism optical system according to the above [22], wherein the water absorption α of the transparent medium satisfies the following condition: 0 <α <0.1 (%) (I-1) Decentered prism optical system.

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

[25] In the eccentric prism optical system according to any one of the above [22] to [24], the lens having the positive refracting power has an effect of preventing the eccentric prism from being damaged. An eccentric prism optical system characterized by being formed so as to have a function of expanding an angle.

[0109]

As is apparent from the above description, according to the present invention, in an imaging optical system or an eyepiece optical system including an eccentric prism which can obtain an image with a clear and less distortion even at a wide angle of view, By configuring a wide surface of one effective area of the prism with a rotationally symmetric surface, it is possible to provide an eccentric prism optical system that can be easily evaluated at the time of manufacturing.

[Brief description of the drawings]

FIG. 1 is an optical path diagram in a case where an eccentric prism which is a main part of an eccentric prism optical system of the present invention is a simplest three-sided prism.

FIG. 2 is an optical path diagram illustrating another configuration of a decentered prism that can be used in the 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 an aberration diagram illustrating image distortion of the first embodiment.

FIG. 10 is a lateral aberration diagram of the first embodiment.

FIG. 11 is a diagram showing a state in which a head-mounted image display device using the eccentric prism optical system of the present invention is mounted on an observer's head.

FIG. 12 is a sectional view of the vicinity of the head in FIG. 11;

FIG. 13 is a perspective view showing a configuration of a camera using the decentered prism optical system of the present invention.

FIG. 14 is an optical path diagram of a photographing optical system using the decentered prism optical system of the present invention.

FIG. 15 is an optical path diagram of a finder optical system using the decentered prism optical system of the present invention.

FIG. 16 is an overall configuration diagram of the endoscope apparatus.

FIG. 17 is a sectional view of a distal end portion of a rigid endoscope using the eccentric prism optical system of the present invention.

FIG. 18 is a diagram for explaining a parameter DY used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Pupil 2 ... Optical axis 3 ... First surface of eccentric prism 4 ... Second surface of eccentric prism 5 ... Third surface of eccentric prism 6 ... Image plane 7 ... Eccentric prism 8 ... Fourth surface of eccentric prism 9 ... Refraction Lens system 9 '... Positive single lens 10 ... Eccentric prism optical system 20 ... Endoscope 21 ... Tip 22 ... Insertion section 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 ... Reproduction device 107... Adjustment unit 150... Objective lens 151... Front group 152 pupil position 153. Eccentric prism optical system 202 ... roof surface 203 ... roof prism 204 ... eyepiece 205 ... eyeball of observer La ... optical axis of viewfinder optical system Lb ... optical axis of photographing optical system

Claims (3)

[Claims] 1. An eccentric prism optical system comprising an eccentric prism having at least three surfaces decentered from each other and having a configuration in which the three surfaces are filled with a transparent medium having a refractive index of 1.3 or more. The eccentric prism forms at least two of the three surfaces with reflective surfaces so as to perform at least two internal reflections, and is reflected by the two reflective surfaces. The two surfaces having the reflecting action are arranged at positions where the rays do not intersect inside the eccentric prism. Of the two surfaces having the reflecting action, the shape of one face is in-plane and out-of-plane. It is formed of a rotationally asymmetric surface having no axis of rotational symmetry, and the shape of at least the effective surface of the other surface (the region through which light flux is transmitted and / or reflected in the entire surface) rotates within the effective surface. Has symmetry axis That are composed of rotationally symmetric surface, decentered prism optical system, wherein a lens having a positive refractive power to the incident side or exit side of the decentered prism is disposed. 2. The eccentric prism optical system according to claim 1, wherein the rotationally symmetric surface of the eccentric prism has a transmission function of causing a light beam passing through the eccentric prism to enter or exit, and the light beam inside the eccentric prism. The eccentric prism is formed as a first surface having a reflecting function to bend, and the rotationally asymmetric surface of the eccentric prism is formed as a second surface opposed to the first surface, and further emits a light beam passing through the eccentric prism. A third surface having a transmissive function to be incident is disposed at a position substantially perpendicular to a direction in which the first surface and the second surface are opposed to each other, and at least the eccentric prism includes the first surface and the second surface. 2. The eccentric prism according to claim 1, wherein the lens is disposed on an entrance side or an exit side of the first surface. 3. Optical system. 3. An eccentric prism optical system according to claim 2, wherein said first surface of said eccentric prism is formed such that its transmission and reflection overlap in at least a part of the effective plane. An eccentric prism optical system, wherein at least a reflection action in a region where the transmission action and the reflection action in the effective surface of the first surface overlap each other is based on a total reflection action.