JP2001133688A - Finder optical system and optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a real-image type finder optical system which is made small-sized as a whole and enables a user to satisfactorily observe a finder image. SOLUTION: In this finder optical system, where an object image formed by an objective lens system is observed through an image inversion means by an eyepiece, the image inversion means is provided with a first prism, which has an incidence surface 11 and a transmission surface 12 arranged at an acute angle to the incidence surface 11, a second prism, a reflection member which reflects luminous flux from an exit surface 23 of the second prism to the eyepiece side, and at least one asymmetrical surface of revolution. The second prism is comprised of an incidence surface 21, which has the surface apex arranged a minute gap apart from the transmission surface 12 and on which a luminous flux from the transmission surface 12 is made incident, a reflection surface 22 which reflects luminous flux from the incidence surface 21 toward the incidence surface 21, a total reflection surface 21a, which totally reflects a luminous flux from the reflection surface 22 and is provided in a part of the incidence surface 21, and the exit surface 23 which emits a luminous flux from the total reflection surface 21a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a finder optical system and an optical apparatus, and more particularly to a viewfinder optical system and an optical apparatus, and more particularly to a viewfinder image (object image) of an inverted real image formed by an objective lens using an image inverting group appropriately set. The present invention relates to a finder optical system and an optical device suitable for an optical device such as a video camera and a digital camera which are observed as a finder image.

[0002]

2. Description of the Related Art Conventionally, a real image formed on a primary image forming surface by an objective lens in a finder system of an optical device such as a photographic camera or a video camera is used as an erect image, and the erect image is observed through an eyepiece. Various such real-image type finder optical systems have been proposed. The real image type finder optical system is easily used in cameras with a zoom lens recently because the size of the entire optical system can be easily reduced as compared with the virtual image type finder optical system.

[0003] A real image type finder system using a Porro prism for an upright positive image is formed by the outer shape of the Porro prism.
Some of them protrude in the vertical and horizontal directions of the optical device, and the entire finder system tends to become larger.

In order to shorten the entire length of the lens of the finder optical system with the miniaturization and thinning of the camera as a whole, the present applicant discloses a primary image forming an object image by an objective lens in Japanese Patent Application Laid-Open No. 6-167739. FIG. 9 proposes a small finder optical system in which an optical path up to a surface is bent by a reflection surface to form a primary imaging surface inside an image inversion group.
FIG. 2 is a sectional view of a main part showing a conventional example using a prism for bending an optical path to a primary imaging surface and a roof prism. In FIG. 9, OL denotes an objective lens, P denotes a prism for erect erect image, and includes a first prism P1 and a second prism (dach prism) P2.

[0005] S is a field frame for limiting the field of view of the finder, and the exit surface 13 of the first prism P1 and the second prism P
The two incident surfaces 21 are provided in a narrow space facing each other.
The finder image of the inverted real image by the objective lens OL is formed near the field frame S via the first prism P1.

Reference numeral EL denotes an eyepiece, which converts a finder image of an inverted real image formed near the field frame S into a second prism P.
The image is observed as a viewfinder image of an erect erect image via 2.

In order to increase the viewing angle in this viewfinder optical system, the prism must be increased, and the thickness of the camera tends to be increased. Also,
The focal length fe of the eyepiece in the viewfinder optical system
Corresponds to the length from the imaging position to the eyepiece. Then, assuming that the focal length of the objective lens is fo, the finder magnification r is r = fo / fe. Increasing the prism lengthens the optical path from the imaging position to the eyepiece.

That is, the focal length fe of the eyepiece EL increases and the finder magnification decreases, making it difficult to observe a good finder image.

An image inverting group which is small in size and can increase the viewing angle and the finder magnification is disclosed in, for example, Japanese Patent Application Laid-Open No. 8-1794.
No. 00 and Japanese Patent Application Laid-Open No. 10-206933 propose a finder optical system in which two prisms are arranged with an air gap at very small intervals.

[0010]

Problems to be Solved by the Invention
In the finder optical system proposed in Japanese Patent Application Laid-Open No. 400-104, and Japanese Patent Application Laid-Open No. 10-206933, the entrance surface 21 of the second prism is decentered with respect to the optical axis of the objective lens or the eyepiece, and is used for both transmission and reflection. They are arranged substantially in parallel with the transmission surface 12 of the first prism P1 with a small air gap. For this reason, the optical path differs depending on the angle of the light beam entering the prism and the place where the light beam passes through the prism, and there is a problem that eccentric aberrations such as astigmatism and coma occur.

According to the present invention, when observing an object image formed by an objective lens system (objective optical system) as an erect erect image using an image inverting group by an eyepiece, the configuration of the image inverting group is appropriately set. While miniaturizing the entire optical system,
It is an object of the present invention to provide a real image type finder optical system and an optical device that enable good finder image observation.

In addition, the present invention suppresses aberrations generated at the air gap between the first prism and the second prism used as an image inverting group, and enables a good finder image to be observed with a high magnification and a wide angle of view. It is an object of the present invention to provide a possible small real-image type finder optical system.

In addition, according to the present invention, when an object image formed via an objective lens group is observed as an erect erect image using an image inverting group by an eyepiece lens group, a good viewfinder image can be observed over the entire visual field. It is an object of the present invention to provide a viewfinder optical system that can be used and an optical device using the same.

[0014]

According to a first aspect of the present invention, there is provided an objective lens group, an image inverting group in which an object image formed through the objective lens group is an erect image, In a finder optical system having an eyepiece group for observing a standing image, the image inverting group includes a first transparent body and a second transparent body that only transmits light, and is disposed at an interval. At least one surface of the body and the second transparent body,
It is characterized by a rotationally asymmetric surface.

According to a second aspect of the present invention, in the finder optical system according to the first aspect, at least one of the opposing surfaces of the first transparent body and the second transparent body is a rotationally asymmetric surface.

According to a third aspect of the present invention, in the finder optical system according to the first or second aspect, the first transparent body has a surface having only a reflection function and a surface having both a reflection function and a transmission function with respect to light rays. And characterized in that:

According to a fourth aspect, in the finder optical system according to any one of the first to third aspects, the image inverting group is
A second transparent body having a second incident surface for transmitting a light beam from the objective lens group, and a transmitting surface disposed at an acute angle to the second incident surface; A first incident surface on which the light beam enters, a reflecting surface for reflecting the light beam from the first incident surface to the first incident surface side, and a part of the first incident surface for totally reflecting the light beam from the reflecting surface. A total reflection surface,
It is characterized by having a first transparent body composed of an emission surface for emitting a light beam from the total reflection surface, and a reflecting member for reflecting the light beam from the emission surface to the eyepiece lens group side.

According to a fifth aspect, in the finder optical system according to any one of the first to third aspects, the image inversion group includes:
A second transparent member having a reflecting member for reflecting the light beam from the objective lens group at least once, a second incident surface for transmitting the light beam from the reflecting member, and a transmitting surface disposed at an acute angle to the second incident surface; A body, a first incident surface, which is disposed at an interval from the transmitting surface, and on which a light beam from the transmitting surface is incident; a reflecting surface, which reflects the light beam from the first incident surface to the first incident surface side; A first transparent body including a total reflection surface provided on a part of the first incident surface for totally reflecting the light beam and an emission surface for emitting the light beam from the total reflection surface.

According to a sixth aspect, in the finder optical system according to the fourth or fifth aspect, the transmission surface is a rotationally asymmetric surface.

According to a seventh aspect, in the finder optical system according to any one of the first to third aspects, the image inversion group is
A first incident surface that transmits the light beam from the objective lens group, a total reflection surface that totally reflects the light beam from the first incident surface, a reflection surface that reflects the light beam from the total reflection surface to the total reflection surface side, and a reflection surface. A first transparent body composed of an emission surface provided on a part of the total reflection surface for emitting a light beam from the surface, and a second incident surface which is disposed at an interval from the emission surface and into which the light beam from the emission surface enters. A second transparent body disposed at an acute angle to the second incident surface and having a transmission surface that emits a light beam, and a reflection member that reflects the light beam from the transmission surface at least once and guides the light to the eyepiece lens group. It is characterized by having.

According to an eighth aspect, in the finder optical system according to any one of the first to third aspects, the image inversion group includes:
A reflecting member for reflecting the light beam from the objective lens group at least once, a first incident surface for transmitting the light beam from the reflecting member, a total reflecting surface for totally reflecting the light beam from the first incident surface, and a total reflecting surface A first transparent body comprising: a reflecting surface for reflecting the light beam from the reflecting surface to the total reflection surface side; and an emitting surface provided on a part of the total reflecting surface for emitting the light beam from the reflecting surface; A second incident surface on which the light beam from the exit surface is incident, and a second transparent body disposed at an acute angle to the second incident surface and having a transmission surface for emitting the light beam to the eyepiece group.

According to a ninth aspect, in the finder optical system according to the seventh or eighth aspect, the second incident surface is a rotationally asymmetric surface.

According to a tenth aspect, in the finder optical system according to any one of the first to ninth aspects, the rotationally asymmetric surface is a surface symmetric with respect to a certain direction.

According to an eleventh aspect, in the finder optical system according to the tenth aspect, the rotationally asymmetric surface has a curvature in a plane perpendicular to a predetermined axis, and has no curvature in a predetermined axis direction. It is characterized by being.

According to a twelfth aspect, in the finder optical system according to the tenth aspect, when XYZ rectangular coordinates are taken,
The rotationally asymmetric surface is a toric surface having a curvature different from a curvature perpendicular to the X axis and a curvature perpendicular to the Y axis.

According to a thirteenth aspect, in the finder optical system according to any one of the first to ninth aspects, the rotationally asymmetric surface has two curvatures in a plane perpendicular to a predetermined axis, and extends in a predetermined axial direction. On the other hand, the surface is characterized by having no curvature.

According to a fourteenth aspect, in the finder optical system according to any one of the first to ninth aspects, the rotationally asymmetric surface does not have a rotationally asymmetric axis.

According to a fifteenth aspect, in the finder optical system according to any one of the first to fourteenth aspects, the first transparent body has a roof surface.

According to a sixteenth aspect of the present invention, in the finder optical system according to any one of the first to fourteenth aspects, the image inverting group is different from the first transparent body and the second transparent body and is a reflecting member that reflects light rays. And the reflection member has a roof surface.

According to a seventeenth aspect, in the finder optical system according to any one of the first to sixteenth aspects, the image inverting group is different from the first transparent body and the second transparent body, and is a reflecting member that reflects light rays. And the reflection member is made of a transparent body.

An eighteenth invention is characterized in that the optical device has the finder optical system according to any one of the first to seventeenth inventions.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing the embodiments of the present invention, how to represent the configuration and common items of the entire embodiment will be described with reference to FIG.

Since the optical system of the present invention is a decentered optical system, each surface constituting the optical system does not have a common optical axis. Therefore, in the embodiment of the present invention, the center of the effective ray diameter of the first surface R1 is defined as the origin, and the path of the light beam passing through the origin and the center of the pupil is defined as the reference axis of the optical system.

Each axis of the seating system is determined as follows.

Z axis: origin and reference axis toward second surface R2 Y axis: straight line passing through the origin and forming 90 ° counterclockwise to Z axis in the tilt plane (in the paper plane) X axis: passing through the origin A straight line perpendicular to each of the Z and Y axes (a straight line perpendicular to the paper surface) A point at which the reference axis intersects the i-th surface (i = 1, 2, 3,...) Is defined as a surface vertex.

In the optical system according to the present invention, the two prisms (transparent bodies) arranged in the optical path with a small air gap are provided with a first prism and a second prism in the order of passage of light in the following embodiments. Say

Where the surface shape of the i-th surface constituting the optical system is represented, Ri is the radius of curvature, the point at which the reference axis and the i-th surface intersect is the surface vertex, and Di is the i-th surface and the (i + 1) -th surface. , A scalar quantity representing the interval between the surface vertices of the i-th surface and (i +
1) The refractive index and Abbe number of the medium between the surfaces. Also, the i-th
The tilt angle of the surface in the YZ plane is defined as an angle θyi (positive in a counterclockwise direction) with respect to a reference axis ray incident on the i-th surface with respect to an angle formed by a surface normal having the origin at the surface vertex of the i-th surface. And the tilt angle in the XZ plane is defined as the angle formed by the surface normal to the reference axis ray incident on the i-th surface with the origin at the surface vertex of the i-th surface. Angle θxi (unit: °). However, on the incident surface of the second prism, (i−
1) It is defined by an angle with respect to a reference axis ray incident on a surface (first prism exit surface).

The embodiment of the present invention has a spherical surface, a rotationally symmetric aspherical surface, and a rotationally asymmetrical aspherical surface. Among them, the spherical portion has a radius of curvature Ri as a spherical shape. The sign of the radius of curvature Ri is minus when the center of curvature is on the first surface side along the reference axis that goes from the first surface to the pupil, and is plus when it is on the imaging surface side.

The shape of the spherical surface is represented by the following equation.

In order to express the shape of each surface by an equation, it is easy to use a local coordinate axis whose origin is the above-mentioned surface vertex. Therefore, in the following expressions of a spherical surface, a rotationally symmetric aspherical surface, and a rotationally asymmetrical aspherical surface, the local coordinates (x, y, z) are used to represent the surface shape.

[0041]

(Equation 1)

The shape of the rotationally symmetric aspheric surface is represented by the following equation.

[0043]

(Equation 2)

Further, the rotationally asymmetric surface shape is represented by the following equation.

[0045]

(Equation 3)

FIG. 1 is a sectional view of a principal part of a finder optical system according to Embodiment 1 (Numerical Example 1) of the present invention in the YZ plane.

In the figure, OL denotes an objective lens, which is a fixed positive lens G1, a negative lens G2 movable on the optical axis for zooming, and a positive lens G3 for correcting an image plane variation accompanying zooming. It has two lenses. P denotes an image inversion group for an erect image, and includes a first prism (second transparent body) 1, a second prism (first transparent body) 2, and a reflecting member 3. S is a field frame for limiting the viewfinder field, and is provided at or near the position of the primary imaging plane where the object image is formed by the objective lens OL. The finder image of the real image by the objective lens OL is transmitted through the first prism 1 and the second prism 2 to the field frame S.
It is formed on a nearby primary imaging plane. EL denotes an eyepiece, which observes a finder image formed near the field frame S via the reflection member 3. SP1 and SP2 are apertures, respectively, provided in the objective lens OL.

Next, the two prisms 1 and 2 and the reflecting member 3 constituting the image inverting group P according to the first embodiment will be described.

The first prism 1 is a triangular prism including an incident surface 11 (R9) for transmitting the light beam from the objective lens OL and a transmitting surface 12 (R10) arranged at an acute angle with the incident surface 11. The second prism 2 has the transmission surface 12 and the surface apex of the first prism 1 arranged at a small interval, and the transmission surface 1
An incident surface 21 (R11) on which the light beam from the light source 2 is incident, a roof reflection surface 22 (R12, R13) for reflecting the light beam from the incident surface 21 to the incident surface 21 side, and a total reflection of the light beam from the roof reflection surface 22 A total reflection surface (R14) 21a provided on a part of the incident surface 21, and an emission surface 23 having a refracting power for emitting a light beam from the total reflection surface 21a to a primary imaging surface.
(R15).

The transmitting surface 12 and the incident surface 21 are eccentric with respect to the reference axis, and the surface vertices are arranged with a small air gap. A rotationally asymmetric aspheric surface is set on the transmission surface 12 (R10), and thereby eccentric aberration generated between the transmission surface 12 and the incident surface 21 is corrected well.

FIG. 17 is an enlarged view of the first prism of this embodiment in the YZ plane, and FIG. 18 is a three-dimensional view of the first prism of this embodiment. The reflecting member 3 reflects a light beam from the primary imaging surface and guides the light beam to the eyepiece.

FIGS. 10A, 10B, and 10C show the wide-angle end, the middle, and the middle, respectively, when the first prism and the second prism are replaced with non-eccentric prisms having equivalent optical path lengths in the first embodiment. It is a lateral aberration figure of a telephoto end. Angle Y = 10.7 when passing through the pupil plane with respect to the center light flux of Y = 0 °
°, -10.7 °, 6.3 °, and -6.3 ° represent lateral aberrations of off-axis light beams.

FIGS. 11A, 11B, and 11C are lateral aberration diagrams at the wide-angle end, the middle position, and the telephoto end when no rotationally asymmetric surface is set in the image inversion group according to the first embodiment. A light beam having a large area when passing through the air gap causes aberration due to a difference in the position where the surrounding light passes. FIG.
The coma aberration changes in FIG. 11 as compared with the non-eccentric system. In the off-axis light beam, the amount of aberration varies depending on the position through which the light beam passes.

In FIG. 11, Y = 10.7 °, -1
Compare 0.7 ° or Y = 6.3 °, -6.3 °,
Coma is not symmetric as in the non-eccentric system in FIG. In other words, the viewfinder image is not symmetrical at the top, bottom, left and right of the field of view, which makes the viewfinder difficult to observe.

FIGS. 12A, 12B and 12C are transverse aberration diagrams of the first embodiment at the wide-angle end, at the middle and at the telephoto end. A rotationally asymmetric aspheric surface is set on the transmission surface 12 (R10) of the first prism. The R10 surface is a surface having different aspheric shapes on the + side and the − side in the Y direction with respect to the optical axis in the YZ plane of FIG. The surface has no curvature in the X-axis direction.
By providing such a surface, the eccentric aberration generated due to the difference in the passing position of the air gap in the YZ plane as described above is suppressed, and the finder images in the upper, lower, left, and right directions are symmetrical, and the field of view is improved.

FIG. 2 shows YZ of the second embodiment according to the present invention.
It is the principal part schematic in a plane.

In FIG. 2, a first prism (second transparent body) 1 has an incident surface 11 (R9) for transmitting a light beam from the objective lens OL and a transmitting surface 12 (at an acute angle to the incident surface 11). R10). Second
The prism (first transparent body) 2 is a transmission surface 1 of the first prism 1.
2 and a surface vertex are arranged at a minute interval, and an incident surface 21 (R11) on which a light beam from the transmission surface 12 is incident;
A reflection surface 22 (R1) that reflects the light flux from
2, R13), a total reflection surface (R14) provided on a part of the incident surface 21 for totally reflecting the light beam from the reflection surface 22, and the light beam from the total reflection surface 21 is emitted to the primary imaging surface. And an emission surface 23 (R15).

The transmitting surface 12 and the incident surface 21 are eccentric with respect to the reference axis, and the surface vertices are arranged with a small air gap. As shown in FIG. 18, a rotationally asymmetric aspherical surface is set on the transmission surface 12 (R10), so that the eccentric aberration generated between the transmission surface 12 and the incident surface 21 is corrected well.

The reflecting member 3 is provided at the exit surface 23 of the second prism 2.
Surface 31 for receiving the light beam from the lens, a roof reflecting surface 32 for reflecting the light beam from the incident surface 31, and an emission surface 3 for emitting the light beam from the roof reflecting surface 32 and guiding the light beam to the eyepiece EL.
And 3.

FIG. 3 shows a third embodiment. In FIG. 3, the reflecting member 3 includes an incident surface 31 on which a light beam from the objective lens OL enters, a roof reflecting surface 32 for reflecting the light beam from the incident surface 31, and an exit surface 33 for emitting a light beam from the roof reflecting surface 32. Have. A primary imaging surface on which an object image is formed by the objective lens OL is provided near the exit surface 33.

The first prism (second transparent body) 1 is a triangular prism including an incident surface 11 for transmitting a light beam from the reflecting member 3 and a transmitting surface 12 arranged at an acute angle with the incident surface 11. The second prism (first transparent body) 2 has an incident surface 21 on which the surface apex and the surface apex of the first prism 1 are arranged at a minute interval and on which a light beam from the transmissive surface 12 is incident.
A reflecting surface 22 for reflecting the light beam from the light source 1 to the incident surface 21 side, a total reflecting surface 21a provided in a part of the incident surface 21 for totally reflecting the light beam from the reflecting surface 22, and the total reflecting surface 21a
And an emission surface 23 for emitting a light beam from the light source.

The transmitting surface 12 and the incident surface 21 are eccentric with respect to the reference axis, and the vertices of the surfaces are arranged with a small air gap. The transmission surface 12 is provided with a rotationally asymmetric aspherical surface, and thereby satisfactorily corrects eccentric aberration generated between the transmission surface 12 and the incident surface 21. The light beam from the surface 23 is guided to the eyepiece EL.

The shape of the first prism of this embodiment corresponds to, for example, a case where the first prism 1 of FIG. 18 is rotated about 180 ° in the Y-axis direction and about 270 ° counterclockwise in the X-axis direction.

FIG. 4 shows a fourth embodiment. In FIG. 4, a reflecting member 3 reflects a light beam from the objective lens OL to form an object image on a primary imaging surface S.

The first prism (second transparent body) 1 is a triangular prism including an incident surface 11 for transmitting a light beam from the reflecting member 3 and a transmitting surface 12 arranged at an acute angle with the incident surface 11. The second prism (first transparent body) 1 has a transmission surface 12 and a surface apex arranged at a minute interval, and an incident surface 21 on which a light beam from the transmission surface 12 is incident, and reflects the light beam from the incident surface 21 to the incident surface 21 side. Roof reflection surface 22, a total reflection surface 21a provided on a part of the incident surface 21 for totally reflecting the light flux from the roof reflection surface 22, and an emission for emitting the light flux from the total reflection surface 21a to the eyepiece EL. Surface 23. The transmitting surface 12 and the incident surface 21 are eccentric with respect to the reference axis, and the surface vertices are arranged with a small air gap.

The transmission surface 12 is provided with a rotationally asymmetric aspherical surface, so that the eccentric aberration generated between the transmission surface 12 and the incident surface 21 is corrected well. The shape of the first prism of this embodiment is, for example, the first prism 1 of FIG.
Approx. 180 ° in Y-axis direction, 270 counterclockwise in X-axis direction
° corresponds to the case of rotation.

FIG. 5 is a sectional view of a main part of a finder optical system according to a fifth embodiment (numerical example 2) of the present invention in the YZ plane.

In the figure, OL denotes an objective lens, which is a fixed positive lens G1, a negative lens G2 movable on the optical axis for zooming, and a positive lens for correcting image plane fluctuation due to zooming. It has four lenses, the positive lens G4. P denotes an image inversion group of an erect normal image, and includes a first prism (first transparent body) 1, a second prism (second transparent body) 2, and a reflecting member 3. S is a field frame that limits the viewfinder field,
It is provided at or near the primary imaging plane position where an object image is formed by the objective lens OL. The finder image of the real image formed by the objective lens OL is formed on the primary image forming surface near the field frame S via the first prism and the second prism. EL denotes an eyepiece, which observes a finder image formed near the field frame S via the reflection member 3.

Next, two prisms and a reflecting member constituting the image inverting group P according to the fifth embodiment will be described.

The first prism 1 has an incident surface 11 (R11) for transmitting the light beam from the objective lens OL, a total reflection surface 12 (R12) for totally reflecting the light beam from the incident surface 11, and a light reflected from the total reflection surface 12. A roof reflecting surface 13 (R13, R14) for reflecting a light beam toward the total reflection surface 12; and an emission surface (R15) 12a provided on a part of the total reflection surface 12 for emitting a light beam from the roof reflection surface 13. Consists of The second prism 2 has an exit surface 12a and a surface apex arranged at a minute interval, and an entrance surface 21 (R1) on which a light beam from the exit surface 12a enters.
6) and a triangular prism including a transmission surface 22 (R17) having a refracting power and arranged at an acute angle to the incident surface 21 and exiting to the primary imaging surface. The exit surface 12a and the entrance surface 21 are eccentric with respect to the reference axis, and the vertices of the surfaces are arranged with a small air gap. A rotationally asymmetric aspherical surface is set on the entrance surface 21 (R16), whereby the eccentric aberration generated between the exit surface 12a and the entrance surface 21 is satisfactorily corrected. The reflecting member 3 reflects a light beam from the primary imaging surface and guides the light beam to the eyepiece. The shape of the second prism of the present embodiment corresponds to, for example, a case where the first prism 1 of FIG. 18 is rotated about 180 ° in the Y-axis direction and about 90 ° counterclockwise in the X-axis direction.

FIGS. 13 (A), (B) and (C) show the wide angle end, the middle position and the middle position when the first prism and the second prism are replaced with non-eccentric prisms having equivalent optical path lengths in the second embodiment. It is a lateral aberration figure of a telephoto end. Angle Y = 10.7 when passing through the pupil plane with respect to the center light flux of Y = 0 °
°, -10.7 °, 6.3 °, and -6.3 ° represent lateral aberrations of off-axis light beams.

FIGS. 14A, 14B, and 14C are lateral aberration diagrams at the wide-angle end, the middle position, and the telephoto end when no rotationally asymmetric surface is set in the image inversion group according to the second embodiment. A light beam having a large area when passing through the air gap causes aberration due to a difference in the position where the surrounding light passes. FIG.
14, the coma aberration changes in comparison with the non-eccentric system of FIG. In the off-axis light beam, the amount of aberration varies depending on the position through which the light beam passes. In FIG. 14, Y = 10.7
Comparing °, -10.7 ° or Y = 6.3 °, -6.3 °, the coma is not symmetric as in the non-eccentric system in FIG. In other words, the viewfinder image is not symmetrical at the top, bottom, left and right of the field of view, which makes the viewfinder difficult to observe.

FIGS. 15A, 15B, and 15C are lateral aberration diagrams of the second embodiment at the wide-angle end, at the middle, and at the telephoto end. A rotationally asymmetric aspheric surface is set on the transmission surface 21 (R16) of the first prism. The R16 surface is a surface having different aspheric shapes on the + side and the − side in the Y direction with respect to the optical axis in the YZ plane of FIG. The surface has no curvature in the X-axis direction.
By providing such a surface, the eccentric aberration generated due to the difference in the passing position of the air gap in the YZ plane as described above is suppressed, and the finder images in the upper, lower, left, and right directions are symmetrical, and the field of view is improved.

FIG. 6 shows a sixth embodiment according to the present invention.
It is the principal part schematic in a plane.

In FIG. 6, a first prism (first transparent body) 1 has an incident surface 11 (R11) for transmitting the light beam from the objective lens OL and a total reflection surface 12 (for total reflection of the light beam from the incident surface 11). R12) and a roof reflecting surface 13 (R1) for reflecting the light flux from the total reflecting surface 12 to the total reflecting surface 12 side.
3, R14), and an emission surface (R1) provided on a part of the total reflection surface 12 for emitting a light beam from the roof reflection surface 13.
5) 12a. Second prism (second transparent body) 2
Is an incident surface 21 (R16) where the exit surface 12a and the surface apex are arranged at a minute interval and the light beam from the exit surface 12a enters.
And a triangular prism including a transmission surface 22 (R17) having a refracting power and arranged to form an acute angle with the incident surface 21 and exit to the primary imaging surface. The exit surface 12a and the entrance surface 21 are eccentric with respect to the reference axis, and the vertices of the surfaces are arranged with a small air gap. A rotationally asymmetric aspherical surface is set on the entrance surface 21 (R16), whereby the exit surface 1 (R16) is set.
The eccentric aberration generated between 2a and the entrance surface 21 is satisfactorily corrected.

The reflecting member 3 is provided at the exit surface 23 of the second prism 2.
Surface 31 for receiving the light beam from the lens, a roof reflecting surface 32 for reflecting the light beam from the incident surface 31, and an emission surface 3 for emitting the light beam from the roof reflecting surface 32 and guiding the light beam to the eyepiece EL.
And 3. The shape of the second prism of the present embodiment is, for example, the first prism 1 of FIG.
This corresponds to a case where the lens is rotated about 90 ° counterclockwise in the X-axis direction by 0 °.

FIG. 7 shows a seventh embodiment. In FIG. 7, a reflecting member 3 includes an incident surface 31 on which a light beam from the objective lens OL enters, a roof reflecting surface 32 for reflecting the light beam from the incident surface 31, and an exit surface 33 for emitting a light beam from the roof reflecting surface 32. Have. A primary imaging surface on which an object image is formed by the objective lens OL is provided near the exit surface 33.

The first prism (first transparent body) 1 has an incident surface 11 having a refractive power for transmitting the light beam from the reflecting member 3.
(R11), a total reflection surface 12 for totally reflecting the light beam from the incident surface 11, and a light beam from the total reflection surface 12 for the total reflection surface 1.
It comprises a reflecting surface 13 for reflecting light to two sides, and an emitting surface 12a provided on a part of the total reflecting surface 12 for emitting a light beam from the reflecting surface 13.

The second prism (second transparent body) 2 is the exit surface 1
2a and the surface vertex are arranged at a minute interval, and the exit surface 12a
Surface 21 on which a light beam from the lens is incident and a transmission surface 2 disposed at an acute angle with respect to the incident surface 21 and emitted to the eyepiece EL
2 is a triangular prism. Exit surface 12a and entrance surface 2
Numeral 1 is eccentric with respect to the reference axis, and its surface apex is arranged with a small air gap.

A rotationally asymmetric aspherical surface is set on the entrance surface 21, and thereby eccentric aberrations generated between the exit surface 12 a and the entrance surface 21 are satisfactorily corrected. The shape of the second prism of the present embodiment is, for example, the first prism 1 of FIG.
Is rotated about 180 ° in the X-axis direction.

FIG. 8 shows an eighth embodiment. In FIG. 8, a reflecting member 3 includes an incident surface 31 on which a light beam from the objective lens OL is incident, a reflecting surface 32 on which the light beam from the incident surface 31 is reflected, and an emission surface 33 on which a light beam from the reflecting surface 32 is emitted.
And A primary imaging surface on which an object image is formed by the objective lens OL is provided near the exit surface 33.

The first prism (first transparent body) 1 has an incident surface 11 having a refractive power for transmitting a light beam from the objective lens, a total reflection surface 12 for totally reflecting the light beam from the incident surface 11, and its total reflection. A roof reflecting surface 13 for reflecting a light beam from the surface 12 to the total reflection surface 12 side, and an emission surface 12 provided on a part of the total reflection surface 12 for emitting a light beam from the roof reflecting surface 13
a.

The second prism (second transparent body) 2 has an exit surface 1
2a and the surface vertex are arranged at a minute interval, and the exit surface 12a
Is a triangular prism including an incident surface 21 on which a light beam from the lens enters, and a transmission surface 22 disposed at an acute angle to the incident surface 21 and exiting to the primary imaging surface. The exit surface 12a and the entrance surface 21 are eccentric with respect to the reference axis, and the vertices of the surfaces are arranged with a small air gap.

A rotationally asymmetric aspherical surface is set on the incident surface 21, thereby satisfactorily correcting eccentric aberration generated between the exit surface 12 a and the incident surface 21. The shape of the second prism of the present embodiment is, for example, the first prism 1 of FIG.
Is rotated about 180 ° in the X-axis direction.

The embodiments 1 to 8 have been described above.
In the present embodiment, the eccentric aberration correction surface is, for example,
In the case of the first and second embodiments, as shown in FIG. 18, a surface having curvature in the Y direction and having different curvatures in + and − directions and having no curvature in the X direction is set. Is not limited to this. For example, as shown in FIG.
A cylindrical surface having a curvature symmetric in the direction and having no curvature in the X direction may be used. For example, as shown in FIG. 20, a toric surface having different curvatures in the Y direction and the X direction may be used. For example, the surface may not be symmetrical in both the Y direction and the X direction (a surface having no axis of rotational symmetry). It is desirable to appropriately set a shape that corrects eccentric aberration according to the position of the air gap and the amount of eccentricity.

In the first to fourth embodiments, the rotationally asymmetric aspheric surface (the surface for correcting the decentering aberration) is provided on the surface adjacent to the air gap of the first prism. In the fifth to eighth embodiments, the air of the second prism is provided. Although it is provided on the surface adjacent to the gap, it is not limited to this and may be provided on any surface constituting the image inversion group. For example, the same effect as that of the present embodiment can be obtained by providing the device on a surface as shown in FIGS.

The following is a numerical example 1 of the present invention. In the numerical examples, "E-0X" means 10-X.

[0088]

[Outside 1]

A numerical embodiment 2 of the present invention will be described below. In the numerical examples, "E-0X" means 10-X.

[0090]

[Outside 2]

Next, one embodiment of an optical device having the above-described finder optical system will be described with reference to FIG. FIG. 24A is a front view of the optical device, and FIG. 24B is a side sectional view. In the figure, 81 is an optical device main body (housing), 82 is a photographing optical system, 83 is a finder optical system of the present embodiment, and 84 is a film as a photosensitive surface. Thus, by applying the finder optical system of the present embodiment to an optical device, a compact and high-performance optical device can be realized.

[0092]

According to the present invention, as described above, the objective is realized by utilizing the image inverting group having the first transparent body and the second transparent body having only the function of transmitting light rays, which are arranged at intervals. When observing an object image formed through a lens system as an erect erect image with an eyepiece, at least one surface of the first transparent body and the second transparent body is made to be a rotationally asymmetric surface, so that eccentric aberration is reduced. A finder optical system capable of observing a good finder image over the entire field of view can be achieved.

According to the present invention, as described above, when the object image formed by the objective lens system (objective optical system) is observed as an erect erect image using the image inversion group by the eyepiece, the image inversion group is used. By appropriately setting the configuration of (1), it is possible to achieve a real image type finder optical system capable of observing a good finder image while reducing the size of the entire optical system.

In addition, according to the present invention, aberrations generated in the air gap between the first prism and the second prism used as the image inverting group are suppressed, and a good finder image can be obtained with a high magnification and a wide angle of view. A small real-image finder optical system that can be observed can be achieved.

Further, even with a small finder optical system, it is possible to achieve a finder optical system which has a high finder magnification and a large viewing angle, and enables good finder images to be observed over the entire visual field.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of an optical system according to a first embodiment of the present invention.

FIG. 2 is an essential part cross-sectional view of an optical system showing an embodiment 2 of the present invention;

FIG. 3 is a sectional view of a main part of an optical system according to a third embodiment of the present invention.

FIG. 4 is a sectional view of a main part of an optical system showing an embodiment 4 of the present invention.

FIG. 5 is a sectional view of a main part of an optical system according to a fifth embodiment of the present invention.

FIG. 6 is an essential part cross-sectional view of an optical system showing an embodiment 6 of the present invention.

FIG. 7 is a sectional view of a main part of an optical system showing an embodiment 7 of the present invention.

FIG. 8 is an essential part cross-sectional view of an optical system showing an embodiment 8 of the present invention.

FIG. 9 is a sectional view of a main part of an optical system of a conventional real image type viewfinder.

FIG. 10 is a lateral aberration diagram in a coaxial system according to Numerical Example 1 of the present invention.

FIG. 11 is a lateral aberration diagram showing eccentric aberration according to Numerical Example 1 of the present invention.

FIG. 12 is a lateral aberration diagram of Numerical Example 1 of the present invention.

FIG. 13 is a lateral aberration diagram in a coaxial system according to Numerical Example 2 of the present invention.

FIG. 14 is a lateral aberration diagram showing eccentric aberration according to Numerical Example 2 of the present invention.

FIG. 15 is a lateral aberration diagram of Numerical Example 2 of the present invention.

FIG. 16 is an explanatory diagram of a coordinate system according to the embodiment of the present invention.

FIG. 17 is an enlarged view of the first prism in the YZ plane according to the first embodiment.

FIG. 18 is a three-dimensional view of the first prism according to the first embodiment.

FIG. 19 is a three-dimensional view of a prism having a cylindrical surface.

FIG. 20 is a three-dimensional view of a prism having a toric surface.

FIG. 21: Another form of a portion having a rotationally asymmetric surface

FIG. 22: Another form of a portion having a rotationally asymmetric surface

FIG. 23: Another form of a portion having a rotationally asymmetric surface

FIG. 24 is an optical device including a finder optical system according to the present invention.

[Explanation of symbols]

 OL Objective lens P Image inversion group EL Eyepiece 1 First prism 2 Second prism 3 Reflecting member S Field frame

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H087 KA14 LA01 LA11 PA01 PA03 PA17 PB01 PB03 QA01 QA07 QA13 QA14 QA22 QA25 QA34 QA42 QA45 RA05 RA06 RA12 RA13 RA36 RA41 SA13 SA17 SA19 SA63 SA64 SA72 SB02 SB12 SB22

Claims (18)

[Claims] 1. A finder optical system comprising: an objective lens group, an image inverting group that sets an object image formed through the objective lens group as an erect image, and an eyepiece lens group that observes the erect image. The inversion group has a first transparent body and a second transparent body only for transmitting light rays, which are arranged with an interval therebetween, and at least one surface of the first transparent body and the second transparent body is
A viewfinder optical system having a rotationally asymmetric surface. 2. The finder optical system according to claim 1, wherein at least one of the surfaces facing the first transparent body and the second transparent body is a rotationally asymmetric surface. 3. The finder optical system according to claim 1, wherein the first transparent body has a surface having only a reflection function and a surface having both a reflection function and a transmission function with respect to light rays. system. 4. The image inverting group includes a second transparent body having a second incident surface for transmitting a light beam from the objective lens group, and a transmitting surface disposed at an acute angle to the second incident surface. ,
A first incident surface, which is disposed at an interval from the transmission surface and on which a light beam from the transmission surface is incident, a reflection surface that reflects the light beam from the first incident surface to the first incident surface side, and the reflection surface A first transparent body comprising: a total reflection surface provided on a part of the first incidence surface for totally reflecting the light flux from the light source; and an emission surface for emitting the light flux from the total reflection surface; 4. The finder optical system according to claim 1, further comprising a reflecting member configured to reflect a light beam toward the eyepiece lens group. 5. The image inverting group includes: a reflecting member that reflects a light beam from the objective lens group at least once; a second incident surface that transmits a light beam from the reflecting member;
A second surface having a transmission surface disposed at an acute angle with the entrance surface;
A transparent body, a first incident surface which is disposed at an interval from the transmitting surface and on which a light beam from the transmitting surface is incident, and a reflecting surface which reflects the light beam from the first incident surface to the first incident surface side. A first transparent body including: a total reflection surface provided on a part of the first incident surface that totally reflects the light beam from the reflection surface; and an emission surface that emits the light beam from the total reflection surface. The finder optical system according to any one of claims 1 to 3, comprising: 6. The finder optical system according to claim 4, wherein the transmission surface is a rotationally asymmetric surface. 7. The image inverting group includes: a first incident surface that transmits a light beam from the objective lens group; a total reflection surface that totally reflects the light beam from the first incident surface; A first transparent body including: a reflecting surface that reflects a light beam to the total reflection surface side; and an emission surface provided on a part of the total reflection surface that emits the light beam from the reflection surface; and a distance from the emission surface. A second incident surface on which the light beam from the exit surface is incident, and a second transparent body having an acute angle with the second incident surface and having a transmission surface for emitting the light beam; And a reflecting member that reflects the light beam at least once and guides the light beam to the eyepiece lens group.
4. The finder optical system according to any one of claims 1 to 3. 8. The image inverting group includes: a reflecting member that reflects a light beam from the objective lens group at least once; a first incident surface that transmits a light beam from the reflecting member;
A total reflection surface that totally reflects the light beam from the incident surface, and a reflection surface that reflects the light beam from the total reflection surface to the total reflection surface side,
A first transparent body composed of an emission surface provided on a part of the total reflection surface for emitting a light beam from the reflection surface, and a light beam from the emission surface, which is disposed at an interval from the emission surface, enters 4. A light-emitting device comprising: a second incident surface; and a second transparent body disposed at an acute angle to the second incident surface and having a transmission surface for emitting a light beam to the eyepiece group.
The finder optical system according to any one of the above items. 9. The finder optical system according to claim 7, wherein the second incident surface is a rotationally asymmetric surface. 10. The finder optical system according to claim 1, wherein the rotationally asymmetric surface is a surface symmetric with respect to a certain direction. 11. The rotationally asymmetric surface is a cylindrical surface having a curvature in a plane perpendicular to a predetermined axis, and having no curvature in the predetermined axis direction. Viewfinder optical system. 12. When the XYZ orthogonal coordinates are taken, the rotationally asymmetric surface is a toric surface having a curvature different from a curvature perpendicular to the X-axis and a curvature perpendicular to the Y-axis. Item 11. The finder optical system according to Item 10. 13. The rotationally asymmetric surface has two curvatures in a plane perpendicular to a predetermined axis, and has no curvature in the predetermined axis direction. 10. The finder optical system according to any one of items 9 to 9. 14. The method according to claim 1, wherein the rotationally asymmetric surface has no rotationally asymmetric axis.
The finder optical system according to the item. 15. The finder optical system according to claim 1, wherein the first transparent body has a roof surface. 16. The image reversing group has a reflecting member that reflects light rays different from the first transparent body and the second transparent body, and the reflecting member has a roof surface. Item 15. The finder optical system according to any one of Items 1 to 14. 17. The image reversing group includes a reflecting member that reflects light rays different from the first transparent member and the second transparent member, and the reflecting member is made of a transparent member. Item 17. The finder optical system according to any one of items 1 to 16. 18. An optical device comprising the finder optical system according to claim 1. Description: