JP2003005074A - Reflection optical system, reflection type optical system and optical apparatus - Google Patents

Abstract

(57) [Problem] To be compact, it is possible to cross an optical path a plurality of times using three or more reflecting surfaces, and to easily emit a light beam from a region surrounded by these reflecting surfaces. Optical elements are desired. SOLUTION: In a reflection type optical element 11 having three or more reflection surfaces R2 to R4 for sequentially reflecting a light beam from an object, a path of a light ray reflected from each reflection surface from the center of the object surface and passing through the center of a pupil. Is defined as a reference axis ST, in a region surrounded by each reflecting surface, the reference axis intersects at least twice, the light flux forms an intermediate image (MI), and a pupil is formed in a plane including the reference axis. Is the maximum optical angle of the element, f is the focal length from the pupil to the intermediate image plane, and ea is the maximum optical effective diameter of this element.
<Ea>.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection type optical system suitable for an imaging optical system of an imaging optical device such as a video camera and a still camera and an observation optical system of an observation optical device such as a head mount display and a finder. The present invention relates to a reflective optical element used for the above.

[0002]

2. Description of the Related Art As a reflection type optical system as described above, there is one proposed in, for example, JP-A-08-292371. FIG. 8 of the present application shows an optical system proposed in the above publication.

In FIG. 1, a light beam from an object is
And enters the reflective optical element B1. The light beam incident on the reflective optical element B1 is refracted on the first surface R1 and is refracted on the second surface R1.
2, the third surface R3, the fourth surface R4, the fifth surface R5, and the sixth surface R6, the light is reflected, the seventh surface R7 is refracted, and the reflection optical element B1 is formed.
Inject.

The light beam from the object forms a primary image on the intermediate image forming surface near the second surface and forms a pupil near the fifth surface in the reflecting optical element B1. The luminous flux emitted from the reflection optical element B1 is reflected on an imaging surface (an imaging surface of an imaging medium such as a CCD) I
Finally, an image is formed on M.

In this reflection type optical system, by using a reflection optical element B1 integrally formed with a plurality of curved surfaces or flat reflection surfaces, it is possible to reduce the size of the entire reflection type optical system and to use a reflection mirror. The influence on the optical performance due to the mirror arrangement accuracy (assembly accuracy), which tends to be a problem in the reflection type optical system, is avoided.

Further, the stop S is disposed closest to the object side of the optical system, and at least one object image is formed in the reflection optical element B1.
By adopting a configuration in which the image is rotated, the effective diameter of the optical element is reduced even though it is a reflective optical element having a wide angle of view. Furthermore, by giving an appropriate refractive power to a plurality of reflecting surfaces constituting the optical element and eccentrically disposing each reflecting surface,
The optical path in the optical system is bent into a desired shape, thereby reducing the overall length of the optical system in a predetermined direction.

[0007] Such a non-coaxial optical system is called an off-axial optical system. That is, when considering a reference axis along a ray passing through the image center and the pupil center, the optical system is defined as an optical system including a curved surface (off-axial curved surface) whose surface normal at the intersection with the reference axis of the constituent surface is not on the reference axis. And
This is an optical system in which the reference axis has a bent shape.

In this off-axial optical system, the constituent surface is generally non-coaxial, and no vignetting occurs on the reflecting surface. Therefore, it is easy to construct an optical system using the reflecting surface. Also, JP-A-8-292372, JP-A-9-222
No. 561 and Japanese Patent Application Laid-Open No. 9-258105 disclose a variable power optical system using these optical elements.
Japanese Patent Publication No. 650 and the like propose a design method.

[0009]

Problems to be Solved by the Invention
In a reflection type optical system proposed in Japanese Patent Application Publication No. HEI 1 (1994), an intermediate image is formed internally to reduce the effective diameter of an optical surface of an optical element. For this reason, the optical path length inevitably increases, and the optical element tends to extend in the longitudinal direction.

[0010] In this optical element, since the degree of freedom of arrangement of the reflection surface is large, it is possible to reduce the length in a certain direction, but the overall volume is still large.

Further, if the optical paths are simply crossed as in the optical element proposed in Japanese Patent Application Laid-Open No. H11-0664734, the size of each reflecting surface is large, and the effective diameters of each are almost the same. It is. Furthermore, in order to make this optical element compact, it is necessary to configure the three or more reflecting surfaces so that their normals face each other, and to cross the optical path twice or more in a region surrounded by the plurality of reflecting surfaces. .

FIG. 9 is a schematic diagram of an optical element in which three reflecting surfaces having substantially the same effective diameter are arranged so that their surface normals face each other. The luminous flux from the object is reflected by the reflecting surfaces R1, R2, R
After the reflection at 3, the light beam must pass between the reflecting surfaces R1 and R2.

However, the space between the reflecting surfaces R1 and R2 is narrow, and the light beam does not pass. In order to pass the light flux, the reflecting surface R1,
It is necessary to increase the distance between R2 or reduce the size of the reflecting surface R2.

Since increasing the distance between the reflecting surfaces R1 and R2 is against the miniaturization of the optical element, it is necessary to reduce the size of the reflecting surface R2.

FIG. 10 shows a case where the size of the reflecting surface R2 is smaller than that of FIG. In this case, the reflection surface R
Since the interval between R1 and R2 is sufficiently large, the light beam reflected by the reflecting surface R3 can pass between the reflecting surfaces R1 and R2.

Therefore, in the present invention, the light path can be crossed a plurality of times using three or more reflecting surfaces while being compact, and the light beam can be easily emitted from the region surrounded by these reflecting surfaces. To be able to provide.

[0017]

According to the present invention, there is provided a reflective optical element having three or more reflecting surfaces for sequentially reflecting a light beam from an object. When the path of the light beam reflected by the reflecting surface and passing through the center of the pupil is set as a reference axis, in the region surrounded by each reflecting surface, the reference axis intersects at least twice and the light beam forms an intermediate image, In a plane including the reference axis, the maximum angle of view passing through the pupil is θ, the focal length from the pupil to the intermediate image plane is f, and the maximum optical effective diameter of this element is e.
When a is satisfied, the following condition is satisfied: 4.f · tan θ <ea (1)

This makes it possible to cross the optical path (reference axis) twice or more in a region surrounded by three or more reflection surfaces of the reflection type optical element, and to minimize the effective diameter of the optical system. The size of the effective diameter in the vicinity of the intermediate imaging position or the pupil imaging position, which becomes smaller, is about half of the maximum effective diameter, and the effective diameter of at least one of the three or more reflecting surfaces is maximized. It is possible to reduce the effective diameter to half or less.

Therefore, despite the fact that the optical path length is long to obtain an intermediate image, the optical element is a compact optical element, and can easily transmit a light beam from within the region surrounded by the reflection surface to between the reflection surfaces. It is possible to realize a reflective optical element that can emit light.

When the value exceeds the upper limit of the above expression (1), the minimum optical effective diameter in the plane including the reference axis becomes larger than half of the maximum optical effective diameter. As a result, each reflecting surface becomes large. For this reason, it becomes difficult to emit a light beam from the region surrounded by the reflection surfaces to the space between the reflection surfaces.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing the embodiments of the present invention, the way of representing the configuration of the optical system in each embodiment and the common items of the entire embodiment will be described. FIG.
FIG. 3 is an explanatory diagram of a coordinate system defining configuration data of an optical system in each embodiment of the present invention.

In the embodiment of the present invention, the i-th surface is defined as the i-th surface along one ray (shown by a dashed line in FIG. 7 and referred to as a reference axis ray) traveling from the object side to the image plane. And

In FIG. 7, a first surface R1 is a stop, a second surface R2 is a refracting surface (incident surface) coaxial with the first surface, and a third surface R3 is a reflecting surface tilted with respect to the second surface R2. , The fourth surface R4 and the fifth surface R5 are shifted and tilted with respect to the respective front surfaces, the sixth surface R6 is shifted with respect to the fifth surface R5,
This is a tilted refraction surface (exit surface).

Each surface from the second surface R2 to the sixth surface R6 is formed on an optical element (reflection type optical element) made of one transparent body made of a medium such as glass or plastic.

Therefore, in the configuration of FIG. 7, the medium from the object surface (not shown) to the second surface R2 is air, the medium from the second surface R2 to the sixth surface R6 is a common medium such as glass or plastic, and the sixth surface. The medium from R6 to a final image plane (not shown) is composed of air.

Further, since the optical system of each embodiment of the present invention is an off-axial optical system, the surfaces constituting the optical system do not have a common optical axis. Therefore, in each embodiment, an absolute coordinate system having the origin at the center of the effective ray diameter of the first surface is set.

The center point of the effective beam diameter of the first surface is defined as the origin, and the path of a light beam (reference axis light beam) passing through the origin and the center of the final imaging plane is defined as the reference axis of the optical system. Further, the reference axis in each embodiment has a direction (direction). The direction is the direction in which the reference axis ray travels during imaging.

In each embodiment of the present invention, the reference axis serving as the reference of the optical system is set as described above. However, the method of determining the reference axis of the optical system depends on the optical design, the aggregation of aberrations, and the like. Alternatively, an axis that is convenient for expressing each surface configuration of the optical system may be used. However, in general, the path of a light ray passing through the center of the image plane and either the stop, the entrance pupil or the exit pupil, or the center of the first surface or the center of the last surface of the optical system is referred to as a reference axis serving as a reference of the optical system. Set to.

In the embodiment of the present invention, the reference axis passes through the first surface, that is, the center point of the effective beam diameter of the stop surface, and the light (reference axis light) reaching the center of the final imaging plane (pupil) is each The path refracted and reflected by the refracting surface and the reflecting surface is set as a reference axis. The order of each surface is set in the order in which the reference axis rays undergo refraction and reflection.

Therefore, the reference axis finally reaches the center of the image plane while changing its direction along the set order of each surface according to the law of refraction or reflection.

In each embodiment of the present invention, all the tilt surfaces constituting the optical system are basically tilted in the same plane. Therefore, each axis of the absolute coordinate system is determined as follows.

Z-axis: Reference axis passing through the origin toward the second surface R2 Y-axis: Straight X-axis passing through the origin and forming 90 ° counterclockwise with respect to the Z-axis in the tilt plane (in the paper of FIG. 7) : Straight line passing through the origin and perpendicular to each of the Z and Y axes (straight line perpendicular to the plane of FIG. 7).

Further, in order to express the surface shape of the i-th surface constituting the optical system, rather than expressing the shape of the surface in the absolute coordinate system, a local point having the point where the reference axis intersects with the i-th surface as the origin is used. It is easier to understand the shape by recognizing the shape by setting the coordinate system and expressing the surface shape of the surface in the local coordinate system. Therefore, when displaying the configuration data of each embodiment, the surface shape of the i-th surface is changed. Expressed in the local coordinate system.

The tilt angle of the i-th surface in the YZ plane is represented by an angle θi (unit: °) with the counterclockwise direction being positive with respect to the Z axis of the absolute coordinate system. Therefore, in each embodiment of the present invention, the origin of the local coordinates of each surface is on the YZ plane in FIG. Also, there is no eccentricity of the plane in the XZ and XY planes.

Further, the local coordinates (x, y,
The y and z axes of z) are Y relative to the absolute coordinate system (X, Y, Z).
It is inclined at an angle θi in the Z plane, and is specifically set as follows.

Z-axis: a straight line passing through the origin of local coordinates and forming an angle θi in the YZ plane in the YZ plane with respect to the Z direction of the absolute coordinate system. Y-axis: passing through the origin of local coordinates and YZ with respect to the z direction. A straight line x-axis that forms 90 ° counterclockwise in the plane: a straight line that passes through the origin of local coordinates and is perpendicular to the YZ plane.

Di is a scalar quantity representing the distance between the origin of the local coordinates on the i-th surface and the (i + 1) -th surface, and Ndi,
νdi is the refractive index and Abbe number of the medium between the i-th surface and the (i + 1) -th surface. In the numerical examples, a sectional view of an optical system and numerical data are shown. The spherical surface has a shape represented by the following equation:

[0038]

(Equation 1)

The optical system of each embodiment has at least three or more rotationally asymmetric aspherical surfaces, and the shape is represented by the following equation.

Z = C02y^Two+ C20x^Two+ C03y^Three+ C21x^Twoy + C04y^Four+ C22
x^Twoy^Two+ C40x^Four + C05y^Five+ C23x^Twoy^Three+ C41x^Foury + C06y⁶+ C24x^Twoy^Four+ C42x
^Foury^Two+ C60x⁶ Since the above surface equation has only even-order terms with respect to x,
The curved surface defined by the notation surface equation has the yz plane as the symmetric surface
The shape is plane-symmetric. If the following conditions are satisfied
In this case, the shape is symmetric with respect to the xz plane.

C03 = C21 = t = 0 Further, C02 = C20 C04 = C40 = C22 / 2 C06 = C60 = C24 / 3 = C
If 42/3 is satisfied, it indicates a rotationally symmetric shape. If the above conditions are not satisfied, the shape is non-rotationally symmetric.

In each embodiment of the present invention, the horizontal half angle of view uY is the maximum angle of view of the light beam incident on the refracting surface R1 in the YZ plane of FIG. 7, and the vertical half angle of view uX is X
This is the maximum angle of view of the light beam incident on the refraction surface R1 in the Z plane. The diameter of the stop is shown as the stop diameter. This is related to the brightness of the optical system.

In the case of showing a lateral aberration diagram of a numerical example,
The vertical angle of incidence and the horizontal angle of incidence on the refracting surface R1 are (0,
The horizontal aberration of the light beam having the incident angle of (uY), (0, 0), (0, -uY), (uX, uY), (uX, 0), (uX, -uY) is shown.

In the lateral aberration diagram, the horizontal axis represents the height of incidence on the pupil, and the vertical axis represents the amount of aberration. Also, in each embodiment, since each surface is basically a plane-symmetric shape with the yz plane as a symmetry plane, the plus and minus directions of the vertical angle of view are the same in the transverse aberration diagram. For simplicity, lateral aberration diagrams in the minus direction are omitted.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
FIG. 1 is a cross-sectional view in an YZ plane of an imaging (imaging) optical system using a reflective optical element according to an embodiment.

In FIG. 1, the reflection type optical element 11
This is an optical element having a surface refraction surface and three curved reflection surfaces, and is integrally formed of a transparent body such as glass. The optical element 11 includes, in the order of passage of light rays from the object, a refracting surface (incident surface) R1 having a refractive power, three reflecting surfaces of a concave reflecting surface R2, a concave reflecting surface R3, and a concave reflecting surface R4, and a refracting surface. A surface (exit surface) R5 is formed.

All the reflecting surfaces are surfaces symmetric only with respect to the YZ plane. A reference axis ray passing through the center of the object plane and the center of the stop S intersects at the intersection of the optical path leading to the planes R1 and R2 and the optical path leading to the planes R3 and R4, and intersects the optical path leading to the planes R2 and R3. They intersect at the intersection with the optical path leading to R4 to R5. By thus folding the optical path, the size of the optical element 11 is reduced.

Next, the image forming operation in the present embodiment will be described. The luminous flux from the object is incident on the entrance surface R1 of the optical element 11 after the amount of incident light is restricted by a stop (entrance pupil), then reflected by the reflection surfaces R2 and R3, temporarily forms an intermediate image, and then reflected by the reflection surface. The light is reflected by R4, exits from the exit surface R5, and re-images on the imaging surface (light receiving surface of an imaging element such as a CCD) I.

The object ray forms an intermediate image in a region MI between the reflecting surface R3 and the reflecting surface R4, and the pupil ray also forms an intermediate image between the reflecting surface R3 and the reflecting surface R4.

As described above, the optical element 11 has a desired optical performance due to the refractive power of the entrance / exit surface and the refractive power of the plurality of curved reflecting surfaces therein, and has a positive refractive power as a whole. It functions as a lens unit.

<Numerical Example 1> Next, a numerical example of the first embodiment will be described. This numerical example shows the case of a reflective imaging optical element having a vertical angle of view of 11.8 degrees and a horizontal angle of view of 20.8 degrees.

Vertical half angle of view 5.9 Horizontal half angle of view 10.4 Aperture diameter 6.00 i Yi Zi θi Di Ndi νdi 1 0.00 0.00 0.00 16.00 1 Aperture 2 0.00 16.00 0.00 14.00 1.52996 55.80 Refractive surface 3 0.00 30.00 16.00 14.00 1.52996 55.80 Reflective surface 4- 7.42 18.13 52.50 16.50 1.52996 55.80 Reflective surface 5.8.36 22.95 81.50 17.50 1.52996 55.80 Reflective surface 6 -9.14 22.95 90.00 0.45 1 Refractive surface 7 -9.59 22.95 90.00 1 Image surface 3.61773e-03 C20 = 2.04814e-02 C03 = -1.30274e-03 C21 = 2.22958e-04 C04 = 1.43421e-04 C22 = 3.10866e-05 C40 = 2.56738e-05 R3 surface C02 = -1.57440e-02 C20 = -1.53043e-02 C03 = 6.39788e-05 C21 = 1.57674e-04 C04 = 2.19551e-06 C22 = -7.64331e-06 C40 = 8.28243e-06 R4 side C02 = 8.10265e-03 C20 = 1.13348e -02 C03 = 7.12443e-04 C21 = 1.91520e-03 C04 = 8.29073e-05 C22 = 2.66582e-04 C40 = 1.02340e-04 R5 side C02 = -3.02067e-02 C20 = -2.82257e-02 C03 = 1.19392e-04 C21 = -1.32651e-04 C04 = -8.89720e-06 C22 = -3.87176e-05 C40 = -2.30547e-05 The lateral aberration diagram of the reflective optical element of this numerical example is shown. To show.

The maximum effective diameter ea of the reflective optical element 11
Is 11.23 mm in the YZ plane on the reflecting surface R2,
The minimum effective diameter is 3.07 mm on the reflecting surface R3. As described above, since the effective diameter at the reflecting surface R2 is small, the reflecting surface R2
It is possible to arrange the exit refraction surface R5 between the reflection surface R3 and the reflection surface R3. At this time, the size of the reflecting surface R3 is close to the size of the intermediate image forming surface.

Here, the size of the intermediate image plane (MI) formed in the vicinity of the reflecting surface R3 in the YZ plane is paraxially calculated.

In the optical surfaces R1-R3, Y-
Since the focal length on the Z plane is 9.4 mm and the maximum angle of view on the YZ plane is 11.8 °, the size of the intermediate image on the YZ plane is 2 × 9.4 × tan (11.8) = 1.968 mm.

The maximum effective diameter of the optical element 12 is the reflection surface R
2 and the size in the YZ plane is 11.23 mm. This is a size <4 · f · tanθ <ea... (1)> that is five times or more the effective diameter at the intermediate imaging position. If the focal length from the stop to the intermediate image plane is reduced, the size of the intermediate image plane can be suppressed, and the minimum effective diameter can be reduced. For this reason, it is possible to configure so that the normals of the reflection surfaces face each other, and to cross the optical path (reference axis) twice or more in a region surrounded by the plurality of reflection surfaces.

In the present embodiment, the prism-shaped reflective optical element 11 having an off-axial reflective surface as an internal reflective surface has been described. However, each reflective surface is constituted by a reflective mirror and is surrounded by these reflective mirrors. A reflective optical element in which the medium in the region is air may be used.

In this embodiment, an optical element having three reflecting surfaces has been described, but the number of reflecting surfaces is not limited to three. However, it is desirable that there be at least three or more sheets for aberration correction.

In this embodiment, an optical element having an off-axial reflective surface has been described. However, the reflective surface used in the reflective optical element of the present invention is not limited to this.

Further, an image forming optical system may be constituted by a plurality of optical elements including the reflection type optical element shown in the present embodiment, and a variable magnification optical system may be constituted by changing the relative positions of these optical elements. it can.

(Second Embodiment) FIG. 3 shows a second embodiment of the present invention.
1 is a cross-sectional view in an YZ plane of an imaging (imaging) optical system using a reflective optical element according to an embodiment.

In FIG. 3, the reflection type optical element 12
This is an optical element having a surface refraction surface and three curved reflection surfaces, and is integrally formed of a transparent body such as glass. The optical element 12 includes, in the order of passage of light rays from the object, a refracting surface (incident surface) R1 having a refractive power, three reflecting surfaces of a concave reflecting surface R2, a concave reflecting surface R3, and a concave reflecting surface R4, and a refracting surface. A surface (exit surface) R5 is formed.

All reflecting surfaces are surfaces symmetric only with respect to the YZ plane. A reference axis ray passing through the center of the object plane and the center of the stop S intersects at the intersection of the optical path leading to the planes R1 and R2 and the optical path leading to the planes R4 and R5, and intersects the optical path leading to the planes R2 and R3. They intersect at the intersection with the optical path leading to R4 to R5. By thus folding the optical path, the size of the optical element 11 is reduced.

Next, the image forming operation in this embodiment will be described. The luminous flux from the object is incident on the entrance surface R1 of the optical element 12 after being limited in the amount of incident light by the stop (entrance pupil), is then reflected by the reflection surface R2, temporarily forms an intermediate image, and is then reflected by the reflection surface R3. The light is reflected by R4, exits from the exit surface R5, and re-images on the imaging surface I.

The object ray forms an intermediate image in a region MI between the reflecting surface R2 and the reflecting surface R3, and the pupil ray forms an intermediate image between the reflecting surface R3 and the reflecting surface R4.

As described above, the optical element 12 has a desired optical performance due to the refractive power of the entrance / exit surface and the refractive power of the plurality of curved reflecting surfaces therein, and has a positive refractive power as a whole. It functions as a lens unit.

<Numerical Example 2> Next, a numerical example of the second embodiment will be described. This numerical example is a reflective imaging optical element having a vertical angle of view of 11.8 degrees and a horizontal angle of view of 20.8 degrees.

Vertical half angle of view 5.9 Horizontal half angle of view 10.4 Aperture diameter 6.00 i Yi Zi θi Di Ndi νdi 1 0.00 0.00 0.00 16.00 1 Aperture 2 0.00 16.00 0.00 12.00 1.52996 55.80 Refractive surface 3 0.00 28.00 18.00 15.50 1.52996 55.80 Reflective surface 4- 9.11 15.46 6.00 12.00 1.52996 55.80 Reflective surface 5 -13.99 26.42 -47.00 21.00 1.52996 55.80 Reflective surface 6 5.74 19.24 -70.00 2.00 1 Refractive surface 7 7.62 18.56 -70.00 1 Image surface Spherical shape R 6 surface r 8 = -84.330 Aspherical shape R2 Surface C02 = -2.71021e-02 C20 = 6.76921e-02 C03 = 2.15031e-04 C21 = -2.33549e-03 C04 = 3.56830e-04 C22 = 1.51196e-04 C40 = 2.68286e-04 C05 = 1.68889e- 05 C23 = -5.05128e-06 C41 = -9.53078e-07 C06 = -1.35645e-06 C24 = -7.34311e-06 C42 = 2.08245e-06 C60 = 4.15800e-07 R3 surface C02 = -2.17579e-02 C20 = -2.27731e-02 C03 = -4.84383e-05 C21 = -4.87769e-04 C04 = 6.68097e-06 C22 = 2.19546e-06 C40 = 1.91012e-04 C05 = 7.20165e-07 C23 = 2.66806e- 06 C41 = 9.60883e-07 C06 = -2.78101e-08 C24 = -3.07563e-07 C42 = 4.74323e-07 C60 = 3.52092e-07 R4 side C02 = 3.38774e-03 C20 = 1.46028e-02 C03 = 8.17598 e-04 C21 = -1.664 93e-03 C04 = 7.50006e-05 C22 = -5.18047e-04 C40 = 7.24263e-05 C05 = -1.20598e-05 C23 = 1.37248e-04 C41 = 7.55779e-05 C06 = -1.17277e-05 C24 = 4.76966e-05 C42 = 1.99363e-05 C60 = 4.28483e-07 R5 surface C02 = -2.56915e-02 C20 = -1.94744e-02 C03 = -7.39799e-05 C21 = -2.26918e-04 C04 = 1.24364e -06 C22 = 6.76674e-06 C40 = 1.75672e-05 C05 = -4.85974e-08 C23 = 1.74836e-06 C41 = 1.76071e-06 C06 = -9.38861e-08 C24 = -4.16033e-07 C42 =- 2.23890e-07 C60 = -3.90073e-08 FIG. 4 shows a lateral aberration diagram of the reflective optical element of this numerical example.

The maximum effective diameter of the reflective optical element 12 is 12.48 mm on the YZ plane on the reflecting surface R2, and the minimum effective diameter is 3.21 mm on the reflecting surface R3. As described above, since the effective diameter on the reflecting surface R2 is small, it is possible to arrange the reflecting surface R4 between the reflecting surface R2 and the reflecting surface R3.
At this time, the size of the reflecting surface R3 is close to the size of the intermediate image forming surface.

Here, the size in the YZ plane of the intermediate imaging plane (MI) formed near the reflection surface R3 is calculated paraxially.

In the optical surfaces R1 to R3, Y-
Since the focal length on the Z plane is 7 mm and the maximum angle of view on the YZ plane is 11.8 °, the size of the intermediate image on the YZ plane is 2 × 7 × tan (11.8) = 1.462 mm. The maximum effective diameter of the optical element 12 is on the reflecting surface R2, and Y−
Since the size on the Z plane is 12.48 mm, the size <4 · f · tan θ <ea...
(1)> If the focal length from the stop to the intermediate image plane is reduced, the size of the intermediate image plane can be suppressed, and the minimum effective diameter can be reduced. For this reason, it is possible to configure so that the normals of the reflection surfaces face each other, and to cross the optical path (reference axis) twice or more in a portion surrounded by the plurality of reflection surfaces.

In this embodiment, the prism-shaped reflective optical element 11 having an off-axial reflective surface as an internal reflective surface has been described. However, each reflective surface is constituted by a reflective mirror and is surrounded by these reflective mirrors. A reflective optical element in which the medium in the region is air may be used.

In this embodiment, the optical element having three reflecting surfaces has been described. However, the number of reflecting surfaces is not limited to three. However, it is desirable that there be at least three or more sheets for aberration correction.

In this embodiment, an optical element having an off-axial reflective surface has been described. However, the reflective surface used in the reflective optical element of the present invention is not limited to this.

Further, an image forming optical system may be constituted by a plurality of optical elements including the reflection type optical element shown in the present embodiment, and a variable magnification optical system may be constituted by changing the relative positions of these optical elements. it can.

(Third Embodiment) FIG. 5 shows a case where the reflective optical element 11 described in the first embodiment is used as an observation optical system of a head mounted display (HMD). In this embodiment, D is an image display panel such as a liquid crystal, and E is an observer's eye. The image size is 4.27 × 2.53.

Next, the optical function of this embodiment will be described. The light beam from the image display panel D enters the refracting surface (incident surface in the present embodiment) R5 of the optical element 11, is then reflected by the reflecting surface R4, forms an intermediate image, and is then reflected by the reflecting surfaces R3 and R2. Then, the light exits from the exit surface R1 and enters the eye E of the observer.

The object ray forms an intermediate image in a region MI between the reflecting surfaces R4 and R3, and the pupil ray also forms an intermediate image between the reflecting surfaces R4 and R3. At this time, the pupil diameter is 6 mm, the eye point is 16 mm, the focal length of this optical element 11 is -11.7, and the principal point distance on the pupil side is 12 mm behind the pupil.

When an intermediate image is formed once in the optical system, the focal length has a negative value and has a converging effect. At this time, the principal point is located away from the optical system, and the eye point can be sufficiently maintained even if the focal length is short. In other words, the optical system having the intermediate image formed has an advantage that the optical design is not so difficult even if the image display panel D is small.

In this embodiment, even when an intermediate image is formed inside the optical element 11, the size of the intermediate image is reduced, and the optical path is folded so that the reference axis rays intersect at least twice. Accordingly, the optical element can be made compact, and the HMD can be made compact as a whole.

In this embodiment, the prism-shaped reflective optical element 11 having an off-axial reflective surface as an internal reflective surface has been described. However, each reflective surface is constituted by a reflective mirror and is surrounded by these reflective mirrors. A reflective optical element in which the medium in the region is air may be used.

In this embodiment, the optical element having three reflecting surfaces has been described. However, the number of reflecting surfaces is not limited to three. However, it is desirable that there be at least three or more sheets for aberration correction.

In this embodiment, an optical element having an off-axial reflective surface has been described. However, the reflective surface used in the reflective optical element of the present invention is not limited to this.

Further, the observation optical system may be constituted by a plurality of optical elements including the reflection type optical element shown in the present embodiment.

(Fourth Embodiment) FIG. 6 shows a case where the reflection type optical element 11 described in the first embodiment is used as an eyepiece optical system constituting a finder optical system of a single-lens reflex camera. I have.

In the figure, P is a focus plate, M is a return mirror (quick return mirror), L is an image pickup optical system, I is an image pickup surface of the image pickup optical system L (light receiving surface of an image pickup device such as a CCD), and E is Is the human eye.

Next, the optical function of this embodiment will be described. The light beam from the object is subjected to an optical action by the imaging optical system L, is reflected by the turning mirror M, and forms an image on the focus plate P.

The light beam diffused on the focus plate P is incident on the incident surface R5 of the optical element 11, then is reflected by the surface R4 to form an image once, is then reflected by the surfaces R3 and R2, and is reflected from the exit surface R1. The light exits and enters the human eye E. The object ray forms an intermediate image in a region MI between the reflecting surface R4 and the reflecting surface R3,
The pupil ray also forms an intermediate image between the reflecting surfaces R4 and R3. The pupil diameter at this time is 6 mm, and the eye point is 16 mm.

Normally, a single-lens reflex camera uses a penta roof prism having a left-right reversal function. However, in the present embodiment, a roof surface is not required because an intermediate image is formed.

Further, similarly to the third embodiment, there is an advantage that the optical design does not become so difficult even if the size of the imaging element is reduced.

In the present embodiment, even if an intermediate image is formed inside the optical element 11, the size of the intermediate image is reduced and the optical path is folded so that the reference axis rays intersect at least twice. Accordingly, the optical element 11 can be made compact, and the eyepiece optical system can be made compact as a whole.

In the present embodiment, the prism-shaped reflective optical element 11 having an off-axial reflective surface as an internal reflective surface has been described. A reflective optical element in which the medium in the region is air may be used.

In the present embodiment, an optical element having three reflecting surfaces has been described, but the number of reflecting surfaces is not limited to three. However, it is desirable that there be at least three or more sheets for aberration correction.

In the present embodiment, an optical element having an off-axial reflecting surface has been described. However, the reflecting surface used in the reflective optical element of the present invention is not limited to this.

Further, the eyepiece optical system may be constituted by a plurality of optical elements including the reflection type optical element shown in the present embodiment.

[0096]

As described above, according to the present invention,
The optical path (reference axis) can intersect twice or more in a region surrounded by three or more reflection surfaces of the reflection type optical element, and the intermediate imaging position or the pupil where the effective diameter of the optical system becomes smallest. The size of the effective diameter in the vicinity of the imaging position is about half of the maximum effective diameter, and the size of the effective diameter of at least one of the three or more reflecting surfaces is less than half of the maximum effective diameter. Can be.

Therefore, despite the fact that the optical path length is increased to obtain an intermediate image, the optical element is a compact optical element and can easily transmit a light beam from within the area surrounded by the reflective surface to between the reflective surfaces. A reflective optical element that can emit light can be realized.

[Brief description of the drawings]

FIG. 1 illustrates a YZ image forming optical system according to a first embodiment of the present invention.
FIG. 3 is an optical sectional view in a plane.

FIG. 2 is a lateral aberration diagram of Numerical Example 1 of the first embodiment.

FIG. 3 illustrates a YZ image forming optical system according to a second embodiment of the present invention.
FIG. 3 is an optical sectional view in a plane.

FIG. 4 is a lateral aberration diagram of Numerical Example 2 of the second embodiment.

FIG. 5 shows a YZ view of an observation optical system according to a third embodiment of the present invention.
FIG. 3 is an optical sectional view in a plane.

FIG. 6 shows a YZ view of an observation optical system according to a fourth embodiment of the present invention.
FIG. 3 is an optical sectional view in a plane.

FIG. 7 is an explanatory diagram of a coordinate system in each embodiment of the present invention.

FIG. 8 is an optical cross-sectional view in the YZ plane of a conventional reflective optical element.

FIG. 9 is a schematic view of a reflection surface arrangement of a conventional reflection type optical element.

FIG. 10 is a schematic view of a reflection surface arrangement of a reflection type optical element of the present invention.

[Explanation of symbols]

11,12 reflective optical element S aperture MI Intermediate imaging plane (area where is formed) I Imaging surface D Image display panel E eyes P Focus board M folding mirror L Imaging optical system R refraction surface or reflection surface Di Surface spacing along the reference axis Ndi refractive index νdi Abbe number

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission Date] June 20, 2002 (2002.6.2
0)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

Patent application title: Reflective optical element, reflective optical system and optical equipment

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction contents]

The light beam from the object forms a primary image on the intermediate image forming surface near the second surface and forms a pupil near the fifth surface in the reflecting optical element B1. The luminous flux emitted from the reflection optical element B1 is reflected on an imaging surface (an imaging surface of an imaging medium such as a CCD) I
An image is finally formed on S.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction contents]

Therefore, in the present invention, the light path can be crossed a plurality of times using three or more reflecting surfaces while being compact, and the light beam can be easily emitted from the region surrounded by these reflecting surfaces. To provide a reflective optical element and a reflective optical system using the same .

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction contents]

[0017]

To achieve the above object, according to the solution to ## in the present invention, the reflected light optical element having three or more sides of the reflecting surface for sequentially reflecting the light beam from the object, each from the center of the object plane When the path of the light beam reflected by the reflecting surface and passing through the center of the pupil is set as a reference axis, in the region surrounded by each reflecting surface, the reference axis intersects at least twice and the light beam forms an intermediate image, In a plane including the reference axis, the maximum angle of view passing through the pupil is θ, the focal length from the pupil to the intermediate image plane is f, and the maximum optical effective diameter of this element is ea.
Then, 4 · f · tanθ <ea (1) is satisfied.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction contents]

[0018] Accordingly, the it is possible to cross the optical path (reference axis) more than once in the region surrounded by the three sides or more reflective surfaces of the reflected light optical element, the effective diameter of the optical system is most The size of the effective diameter in the vicinity of the intermediate imaging position or the pupil imaging position, which becomes smaller, is about half of the maximum effective diameter, and the effective diameter of at least one of the three or more reflecting surfaces is maximized. It is possible to reduce the effective diameter to half or less.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction contents]

Therefore, despite the fact that the optical path length is long to obtain an intermediate image, the optical element is a compact optical element, and can easily transmit a light beam from within the region surrounded by the reflection surface to between the reflection surfaces. reflection can be emitted
It is possible to realize an optical optical element.

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0022

[Correction method] Change

[Correction contents]

In the embodiment of the present invention, in the case of an imaging optical system,
Is the i-th surface along one light ray (shown by a dashed line in FIG. 7 and referred to as a reference axis light ray) traveling from the object side to the image plane. In the case of the observation optical system,
Contrary to the direction, along the optical path from the observer side to the observation target side
The i-th surface is defined as a first surface. Hereinafter, unless otherwise noted
The definition is explained based on the imaging optics,
The aperture plane is the pupil plane of the observation optical system, and the final image plane is the observation plane (object
Surface), the following description can be applied to the observation optical system.
You.

[Procedure amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0023

[Correction method] Change

[Correction contents]

[0023] In FIG. 7, plane 0 R 0 is squeezed, the first surface R 1 is plane 0 and a refracting surface coaxial (incident surface), the second surface R 2 tilted with respect to the first surface R 1 The reflected surface, the third surface R 3 and the fourth surface R 4 are shifted with respect to each front surface, the tilted reflecting surface, the fifth surface R 5 is shifted with respect to the fourth surface R 4 ,
This is a tilted refraction surface (exit surface).

[Procedure amendment 9]

[Document name to be amended] Statement

[Correction target item name] 0024

[Correction method] Change

[Correction contents]

[0024] Each of the surface from the first surface R 1 to the fifth surface R 5 is constructed on a glass, an optical element comprising a single transparent body composed of a medium such as plastic (reflected light optical element) .

[Procedure amendment 10]

[Document name to be amended] Statement

[Correction target item name] 0025

[Correction method] Change

[Correction contents]

[0025] Thus, in the configuration of FIG. 7, the medium is air from the object plane (not shown) to the first surface R 1, the glass from the first surface R 1 to the fifth surface R 5, common medium such as plastic, the medium to the final image plane (not shown) from the fifth surface R 5 is constituted by air.

[Procedure amendment 11]

[Document name to be amended] Statement

[Correction target item name] 0027

[Correction method] Change

[Correction contents]

The center point of the effective beam diameter of the zeroth surface R0 is defined as the origin, and the path of a light beam (reference axis light beam) passing through the origin and the center of the final imaging plane is defined as the reference axis of the optical system. . Further, the reference axis in each embodiment has a direction (direction). The direction is the direction in which the reference axis ray travels during imaging. (However, in the case of the observation optical system,
In the direction opposite to the traveling direction. )

[Procedure amendment 12]

[Document name to be amended] Statement

[Correction target item name] 0028

[Correction method] Change

[Correction contents]

In each embodiment of the present invention, the reference axis serving as the reference of the optical system is set as described above. However, the method of determining the reference axis of the optical system depends on the optical design, the aggregation of aberrations, and the like. Alternatively, an axis that is convenient for expressing each surface configuration of the optical system may be used. However, in general, the path of a light beam passing through the center of the image plane and either the stop, the entrance pupil or the exit pupil, or the center of the most incident side surface or the final surface of the optical system is referred to as a reference axis serving as a reference of the optical system. Set to.

[Procedure amendment 13]

[Document name to be amended] Statement

[Correction target item name] 0029

[Correction method] Change

[Correction contents]

In the embodiment of the present invention, the reference axis passes through the first surface, that is, the center point of the effective beam diameter of the stop surface, and the light beam (reference axis light beam) reaching the center of the final image forming surface is reflected on each refraction surface and the reference surface. The path refracted and reflected by the reflection surface is set as a reference axis. The order of each surface is set in the order in which the reference axis rays undergo refraction and reflection.

[Procedure amendment 14]

[Document name to be amended] Statement

[Correction target item name] 0036

[Correction method] Change

[Correction contents]

Z-axis: a straight line passing through the origin of the local coordinate system and forming an angle θi in the YZ plane in the counterclockwise direction with respect to the Z direction of the absolute coordinate system y-axis: passing through the origin of the local coordinate system and forming the z- axis on the YZ plane X-axis: 90 ° in the counterclockwise direction within the line: a straight line passing through the origin of local coordinates and perpendicular to the YZ plane.

[Procedure amendment 15]

[Document name to be amended] Statement

[Correction target item name] 0042

[Correction method] Change

[Correction contents]

In each embodiment of the present invention, the horizontal half angle of view uY is the half value of the maximum angle of view of the light beam incident on the refracting surface R1 in the YZ plane of FIG.
Is the half value of the maximum angle of view of the light beam incident on the refraction surface R1 in the XZ plane. The diameter of the stop is shown as the stop diameter. This is related to the brightness of the optical system.

[Procedure amendment 16]

[Document name to be amended] Statement

[Correction target item name] 0045

[Correction method] Change

[Correction contents]

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
Shows a cross-sectional view in the YZ plane of the imaging (image pickup) optical system using reflected light optical element which is an embodiment.

[Procedure amendment 17]

[Document name to be amended] Statement

[Correction target item name] 0046

[Correction method] Change

[Correction contents]

[0046] In FIG. 1, reflected light optical element 11 is an optical element having a curved reflecting surface of the refracting surface and the third surface of the second surface, are integrally formed of a transparent material such as glass. The optical element 11 includes, in the order of passage of light rays from the object, a refracting surface (incident surface) R1 having a refractive power, three reflecting surfaces of a concave reflecting surface R2, a concave reflecting surface R3, and a concave reflecting surface R4, and a refracting surface. A surface (exit surface) R5 is formed.

[Procedure amendment 18]

[Document name to be amended] Statement

[Correction target item name] 0047

[Correction method] Change

[Correction contents]

All the reflecting surfaces are surfaces symmetric only with respect to the YZ plane. The center of the object plane and the center of the pupil (aperture S) (or
Is the reference axis ray passing through the center of the pupil and the center of the image plane).
At the intersection of the optical path leading to R2 and the optical path leading to the planes R3-R4, and the optical path leading to the planes R2-R3 and the plane R4-
They intersect at the intersection with the optical path leading to R5. By thus folding the optical path, the optical element 1
1 is downsized.

[Procedure amendment 19]

[Document name to be amended] Statement

[Correction target item name] 0048

[Correction method] Change

[Correction contents]

Next, the image forming operation in the present embodiment will be described. The luminous flux from the object is incident on the entrance surface R1 of the optical element 11 after the amount of incident light is restricted by the stop (entrance pupil) S , then reflected by the reflection surfaces R2 and R3, temporarily forms an intermediate image, and then reflected. The light is reflected by the surface R4, exits from the exit surface R5, and is re-imaged on the imaging surface (light receiving surface of an imaging element such as a CCD) I.

[Procedure amendment 20]

[Document name to be amended] Statement

[Correction target item name] 0052

[Correction method] Change

[Correction contents]

Vertical half angle of view 5.9 Horizontal half angle of view 10.4 Diameter 6.00 i Yi Zi θi Di Ndi νdi 0 0.00 0.00 0.00 16.00 1 Aperture 1 0.00 16.00 0.00 14.00 1.52996 55.80 Refraction surface 2 0.00 30.00 16.00 14.00 1.52996 55.80 Reflection surface 3- 7.42 18.13 52.50 16.50 1.52996 55.80 Reflective surface 4 8.36 22.95 81.50 17.50 1.52996 55.80 Reflective surface 5 -9.14 22.95 90.00 0.45 1 Refractive surface 6 -9.59 22.95 90.00 1 Image surface spherical shape R 5 surface r 5 = ∞ Aspheric surface R 1 surface C02 = -3.61773e-03 C20 = 2.04814e-02 C03 = -1.30274e-03 C21 = 2.22958e-04 C04 = 1.43421e-04 C22 = 3.10866e-05 C40 = 2.56738e-05 R 2 side C02 = -1.57440 e-02 C20 = -1.53043e-02 C03 = 6.39788e-05 C21 = 1.57674e-04 C04 = 2.19551e-06 C22 = -7.64331e-06 C40 = 8.28243e-06 R 3 side C02 = 8.10265e-03 C20 = 1.13348e-02 C03 = 7.12443e-04 C21 = 1.91520e-03 C04 = 8.29073e-05 C22 = 2.66582e-04 C40 = 1.02340e-04 R 4 side C02 = -3.02067e-02 C20 = -2.82257 e-02 C03 = 1.19392e-04 C21 = -1.32651e-04 C04 = -8.89720e-06 C22 = -3.87176e-05 C40 = -2.30547e-05 Transverse aberration diagram of the reflective optical element of this numerical example Is shown in FIG.

[Procedure amendment 21]

[Document name to be amended] Statement

[Correction target item name] 0053

[Correction method] Change

[Correction contents]

[0053] The maximum effective diameter ea of the reflected light optical element 11
Is 11.23 mm in the YZ plane on the reflecting surface R2,
The minimum effective diameter is 3.07 mm on the reflecting surface R3. As described above, since the effective diameter at the reflecting surface R2 is small, the reflecting surface R2
It is possible to arrange the exit refraction surface R5 between the reflection surface R3 and the reflection surface R3. At this time, the size of the reflecting surface R3 is close to the size of the intermediate image forming surface.

[Procedure amendment 22]

[Document name to be amended] Statement

[Correction target item name] 0055

[Correction method] Change

[Correction contents]

From the pupil (aperture S) to the intermediate image plane MI,
In three optical surfaces R1-R3, YZ
Since the focal length on the plane is 9.4 mm and the maximum angle of view on the YZ plane is 11.8 °, the size of the intermediate image on the YZ plane is 2 × 9.4 × tan (11.8) = 1.968 mm.

[Procedure amendment 23]

[Document name to be amended] Statement

[Correction target item name] 0056

[Correction method] Change

[Correction contents]

The maximum effective diameter of the optical element 12 is the reflection surface R
2 and the size in the YZ plane is 11.23 mm. This satisfies becomes 5 times or more the size of the effective diameter at the intermediate image position 4 · f · tanθ <ea ... (1). This
If the focal length from the pupil to the intermediate image plane is shortened so as to satisfy the conditional expression (1) as described below , the size of the intermediate image plane can be suppressed, and the minimum effective diameter can be reduced. . For this reason, it is configured so that the normals of the reflection surface face each other,
Optical path (reference axis) in the area surrounded by the multiple reflecting surfaces
Can be crossed twice or more.

[Procedure amendment 24]

[Document name to be amended] Statement

[Correction target item name] 0057

[Correction method] Change

[Correction contents]

[0057] In the present embodiment has described the prismatic reflected light optical element 11 having an off-axial reflecting surface as an internal reflection surface, each reflecting surface a reflecting mirror, surrounded by these reflecting mirrors the medium in the region may be used reflected light optical element was air.

[Procedure amendment 25]

[Document name to be amended] Statement

[Correction target item name] 0059

[Correction method] Change

[Correction contents]

In this embodiment, an optical element having an off-axial reflecting surface has been described.
The reflection surface used for the projection optical element is not limited to this.

[Amendment 26]

[Document name to be amended] Statement

[Correction target item name] 0060

[Correction method] Change

[Correction contents]

[0060] Further, a plurality of optical elements including a reflected light optical element shown in this embodiment constitutes an imaging optical system, also configure the variable magnification optical system by changing the relative position of these optical elements it can.

[Amendment 27]

[Document name to be amended] Statement

[Correction target item name] 0061

[Correction method] Change

[Correction contents]

(Second Embodiment) FIG. 3 shows a second embodiment of the present invention.
Shows a cross-sectional view in the YZ plane of the imaging (image pickup) optical system using reflected light optical element which is an embodiment.

[Amendment 28]

[Document name to be amended] Statement

[Correction target item name] 0063

[Correction method] Change

[Correction contents]

All reflecting surfaces are surfaces symmetric only with respect to the YZ plane. Center of object plane and center of pupil ( aperture S )
The reference axis ray passing through (or the center of the pupil and the center of the image plane) is
The optical path leading to surfaces R2 and R3 intersects at the intersection of the optical path leading to surfaces R1 and R2 and the optical path leading to surfaces R4 and R5.
It intersects at the intersection with the optical path leading to R5. By thus folding the optical path, the size of the optical element 11 is reduced.

[Procedure amendment 29]

[Document name to be amended] Statement

[Correction target item name]

[Correction method] Change

[Correction contents]

Vertical half angle of view 5.9 Horizontal half angle of view 10.4 Diameter 6.00 i Yi Zi θi Di Ndi νdi 0 0.00 0.00 0.00 16.00 1 Aperture 1 0.00 16.00 0.00 12.00 1.52996 55.80 Refraction surface 2 0.00 28.00 18.00 15.50 1.52996 55.80 Reflection surface 3- 9.11 15.46 6.00 12.00 1.52996 55.80 Reflective surface 4 -13.99 26.42 -47.00 21.00 1.52996 55.80 Reflective surface 5 5.74 19.24 -70.00 2.00 1 Refractive surface 6 7.62 18.56 -70.00 1 Image surface spherical shape R 5 surface r 5 = -84.330 Aspherical shape R One side C02 = -2.71021e-02 C20 = 6.76921e-02 C03 = 2.15031e-04 C21 = -2.33549e-03 C04 = 3.56830e-04 C22 = 1.51196e-04 C40 = 2.68286e-04 C05 = 1.68889e -05 C23 = -5.05128e-06 C41 = -9.53078e-07 C06 = -1.35645e-06 C24 = -7.34311e-06 C42 = 2.08245e-06 C60 = 4.15800e-07 R 2 side C02 = -2.17579e -02 C20 = -2.27731e-02 C03 = -4.84383e-05 C21 = -4.87769e-04 C04 = 6.68097e-06 C22 = 2.19546e-06 C40 = 1.91012e-04 C05 = 7.20165e-07 C23 = 2.66806 e-06 C41 = 9.60883e-07 C06 = -2.78101e-08 C24 = -3.07563e-07 C42 = 4.74323e-07 C60 = 3.52092e-07 R 3 side C02 = 3.38774e-03 C20 = 1.46028e-02 C03 = 8.17598e-04 C21 = -1.66493e-03 C04 = 7.50006e -05 C22 = -5.18047e-04 C40 = 7.24263e-05 C05 = -1.20598e-05 C23 = 1.37248e-04 C41 = 7.55779e-05 C06 = -1.17277e-05 C24 = 4.76966e-05 C42 = 1.99363 e-05 C60 = 4.28483e-07 R 4 side C02 = -2.56915e-02 C20 = -1.94744e-02 C03 = -7.39799e-05 C21 = -2.26918e-04 C04 = 1.24364e-06 C22 = 6.76674e -06 C40 = 1.75672e-05 C05 = -4.85974e-08 C23 = 1.74836e-06 C41 = 1.76071e-06 C06 = -9.38861e-08 C24 = -4.16033e-07 C42 = -2.23890e-07 C60 = lateral aberration of the reflected light optical element of -3.90073e-08 present numerical example shown in FIG.

[Procedure amendment 30]

[Document name to be amended] Statement

[Correction target item name]

[Correction method] Change

[Correction contents]

[0069] In 12.48mm in this maximum effective diameter of the reflected light optical element 12 is Y-Z plane on the reflecting surface R2, the minimum effective diameter is 3.21mm on the reflective surface R3. As described above, since the effective diameter on the reflecting surface R2 is small, it is possible to arrange the reflecting surface R4 between the reflecting surface R2 and the reflecting surface R3. At this time, the size of the reflecting surface R3 is close to the size of the intermediate image forming surface.

[Procedure amendment 31]

[Document name to be amended] Statement

[Correction target item name] 0071

[Correction method] Change

[Correction contents]

From the pupil (aperture S) to the intermediate image plane MI,
In two optical surfaces to Wachi surface R1~R 2, Y-Z
Since the focal length on the plane is 7 mm and the maximum angle of view on the YZ plane is 11.8 °, the size of the intermediate image on the YZ plane is 2 × 7 × tan (11.8) = 1.462 mm. The maximum effective diameter of the optical element 12 is on the reflecting surface R2, and is YZ.
Since the size in the plane is 12.48 mm,
8.5 times or more , 4 ・ f ・ tanθ <ea
Satisfies (1) . Thus, conditional expression (1) is satisfied.
If the focal length from the pupil to the intermediate image plane is reduced, the size of the intermediate image plane can be suppressed, and the minimum effective diameter can be reduced. For this reason, it is possible to configure so that the normals of the reflection surfaces face each other, and to cross the optical path (reference axis) twice or more in a portion surrounded by the plurality of reflection surfaces.

[Procedure amendment 32]

[Document name to be amended] Statement

[Correction target item name] 0072

[Correction method] Change

[Correction contents]

[0072] In the present embodiment has described the prismatic reflected light optical element 12 having an off-axial reflecting surface as an internal reflection surface, each reflecting surface a reflecting mirror, surrounded by these reflecting mirrors A reflective optical element in which the medium in the region is air may be used.

[Procedure amendment 33]

[Document name to be amended] Statement

[Correction target item name] 0081

[Correction method] Change

[Correction contents]

[0081] In the present embodiment has described the prismatic reflected light optical element 11 having an off-axial reflecting surface as an internal reflection surface, each reflecting surface a reflecting mirror, surrounded by these reflecting mirrors A reflective optical element in which the medium in the region is air may be used.

[Procedure amendment 34]

[Document name to be amended] Statement

[Correction target item name] 0083

[Correction method] Change

[Correction contents]

In this embodiment, an optical element having an off-axial reflecting surface has been described.
The reflection surface used for the projection optical element is not limited to this.

[Procedure amendment 35]

[Document name to be amended] Statement

[Correction target item name]

[Correction method] Change

[Correction contents]

[0084] Further, it may be configured observation optical system by the plurality of optical elements including a reflected light optical element shown in this embodiment.

[Procedure amendment 36]

[Document name to be amended] Statement

[Correction target item name] 0085

[Correction method] Change

[Correction contents]

[0085] The Fourth Embodiment FIG. 6, shows the case of using the reflected light optical element 11 described in the first embodiment as an ocular optical system constituting a finder optical system of a single-lens reflex camera I have.

[Procedure amendment 37]

[Document name to be amended] Statement

[Correction target item name] 0092

[Correction method] Change

[Correction contents]

[0092] In the present embodiment has described the prismatic reflected light optical element 11 having an off-axial reflecting surface as an internal reflection surface, each reflecting surface a reflecting mirror, surrounded by these reflecting mirrors the medium in the region may be used reflected light optical element was air.

[Procedure amendment 38]

[Document name to be amended] Statement

[Correction target item name]

[Correction method] Change

[Correction contents]

In this embodiment, the optical element having the off-axial reflecting surface has been described.
The reflection surface used for the projection optical element is not limited to this.

[Procedure amendment 39]

[Document name to be amended] Statement

[Correction target item name] 0095

[Correction method] Change

[Correction contents]

[0095] Further, it may be configured eyepiece optical system by a plurality of optical elements including a reflected light optical element shown in this embodiment.

[Procedure amendment 40]

[Document name to be amended] Statement

[Correction target item name] 0096

[Correction method] Change

[Correction contents]

[0096]

As described above, according to the present invention,
It is possible to cross the optical path (reference axis) more than once in the region surrounded by the three sides or more reflective surfaces of the reflected light optical element, most small intermediate imaging position or pupil effective diameter of the optical system The size of the effective diameter in the vicinity of the imaging position is about half of the maximum effective diameter, and the size of the effective diameter of at least one of the three or more reflecting surfaces is less than half of the maximum effective diameter. Can be.

[Procedure amendment 41]

[Document name to be amended] Statement

[Correction target item name] 0097

[Correction method] Change

[Correction contents]

Therefore, despite the fact that the optical path length is increased to obtain an intermediate image, the optical element is a compact optical element, and can easily transmit a light beam from within the region surrounded by the reflection surface to between the reflection surfaces. reflection can be emitted
It is possible to realize an optical optical element.

[Procedure amendment 42]

[Document name to be amended] Drawing

[Correction target item name] Fig. 7

[Correction method] Change

[Correction contents]

FIG. 7

[Procedure amendment 43]

[Document name to be amended] Drawing

[Correction target item name] Fig. 8

[Correction method] Change

[Correction contents]

FIG. 8

Claims (9)

[Claims] 1. A reflection type optical element having three or more reflection surfaces for sequentially reflecting a light beam from an object, wherein a path of a light ray reflected from each of the reflection surfaces from the center of an object surface and passing through the center of a pupil is provided. When the reference axis is defined as a reference axis, the reference axis intersects at least twice in a region surrounded by the reflection surfaces, the light flux forms an intermediate image, and passes through a pupil in a plane including the reference axis. Assuming that the maximum angle of view is θ, the focal length from the pupil to the intermediate image plane is f, and the maximum optical effective diameter of this element is ea, 4 · f · tan θ <ea is satisfied. Reflective optical element. 2. The reflective optical element according to claim 1, wherein each of the reflecting surfaces has a curvature. 3. The reflective optical element according to claim 1, wherein the reflective optical element has a finite focal length. 4. The reflective optical element according to claim 1, wherein each of the reflecting surfaces has a shape having only one symmetric surface. 5. A refracting surface on which a light beam from an object is incident;
5. The method according to claim 1, wherein an inner reflecting surface as each of the reflecting surfaces and a refracting surface for emitting a light beam sequentially reflected by the reflecting surfaces are integrally formed on one transparent body. The reflective optical element according to any one of the above. 6. A reflection comprising the reflection optical element according to claim 1 and functioning as an imaging optical system for imaging a light beam from an object emitted from the reflection optical element. Optical system. 7. An observation optical system including the reflection optical element according to claim 1 and guiding image light emitted from an image display element that modulates light to an observer's eye by the reflection optical element. A reflective optical system that functions. 8. An eyepiece optical system that includes the reflective optical element according to claim 1 and guides an object image formed by an objective optical system to an observer's eye by the reflective optical element. A reflective optical system characterized by the following. 9. An optical apparatus comprising the reflection type optical system according to claim 6. Description: