JPH0310232A - Finder optical system with variable observation direction - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a finder optical system with variable observation direction, and in particular, to a finder optical system that can change the viewing direction, and in particular to A photographic camera or video camera that uses a triangular prism and a removable reflective member to switch the observation direction, such as an eye-level direction and a waist-level direction. The present invention relates to a finder optical system with variable observation direction suitable for cameras, binoculars, and the like.

(Prior Art) Conventionally, for example, in the finder optical system of an eye-reflex camera, there has been a finder that selectively switches the observation direction of the subject image between two directions: the eye-level direction and the waist-level direction. Various optical systems have been proposed. For example, such a finder light '-y' system in which the observation direction can be switched has been proposed in Japanese Patent Application Laid-Open No. 51-39120.

4(A) and (rl>) are schematic diagrams of the main parts of the finder optical system proposed in the same publication. FIG.
indicates the time at waist level.

In the same figures (A) and (B), 41 is a fixed first prism, 42 is a rotatable second prism, and these two
A subject image formed on a finder imaging plane (not shown) is corrected to an erect normal image by two prisms 41 and 42. 43 is an eyepiece lens, 48a.

48b is each eye point.

In the same figures (A) and (n), the rotatable second prism 42 is arranged between the exit surface 41a and the entrance surface 42 according to the observation direction.
By rotating the prisms 41 without facing each other, the luminous flux from the first prism 41 can be selectively directed to either the eye level direction ((8) in the same figure) or the waist level direction ((+1) in the same figure). The subject image is observed by switching the camera.

However, in Figures (A) and (B), when switching the observation direction, since the second prism 42 is relatively large, a large storage space must be secured in advance for the rotation of the second prism 42. Therefore, the entire finder device has tended to become larger and more expensive.

Furthermore, in Japanese Utility Model Publication No. 39-35290, the present applicant placed a removable reflection prism behind a so-called penta roof prism, and by inserting and removing the reflection prism, the observation direction can be changed between the eye level direction and the waist level direction. We are proposing a finder optical system that can be easily switched between two directions.

FIG. 5 is a schematic diagram of the main parts of the viewfinder optical system with variable observation direction proposed in the publication.

In the same figure, 54 is a penta roof prism for erected images;
Reference numeral 55 denotes a reflecting prism, which is disposed at the rear of the pentagonal roof prism 54 so as to be freely insertable and removable. 53a and 53b are eyepiece lenses, respectively, and 58a.

58b is each eye point.

In the figure, the reflective prism 55 is used as a finder, and when it is retracted out of the optical path, it is used as an eye-level finder optical system using the eyepiece 53a, and when the reflective prism 55 is inserted into the finder optical path, it is used as an eye-level finder optical system A, and when the reflective prism 55 is inserted into the finder optical path, the eyepiece 53b is used. is used as a level finder optical system.

In other words, at eye level (eye level finder optical system)
The luminous flux from an object (not shown) is transferred to a penta-roof prism 54.
Light is guided to the eyepiece lens 53a through the eyepiece lens 53a, and a subject image formed on a focusing plate (not shown) is observed from the eye point 58a, that is, from the eye level direction.

Furthermore, during observation at waist level (waist level finder optical system), the reflective prism 55, which had been retracted outside the finder optical path, is inserted into the optical path behind the pentagonal roof prism 54, as shown in the figure. Then, the light flux from the object (not shown) is guided to the eyepiece lens 53b via the penta-roof prism 54 and the reflection prism 55, and the object image formed on the surface of the focusing plate (not shown) is focused on the eye point 53.
The image is observed from b, that is, from the waist level direction.

However, in the viewfinder optical system with variable observation direction proposed in the same publication, the removable reflection prism 55 is relatively large, so a large storage space must be secured in advance for insertion and removal. Similarly, there was a tendency for finder devices as a whole to become larger.

(Problems to be solved by the invention) In order to solve the problems shown in the conventional example, the invention includes two triangular prisms, a first triangular prism and a second triangular prism, each having a predetermined shape, behind the objective lens. Triangular prisms are efficiently arranged at a certain air interval, and a removable reflecting member is provided near the exit surface of the first triangular prism to selectively reflect the object image depending on the observation direction of the subject image. An object of the present invention is to provide a relatively compact and inexpensive viewfinder optical system with a variable observation direction, which can selectively and easily switch between two directions, the eye-level direction and the waist-level direction, by inserting and removing members. 1 target.

(Means for Solving the Problems) The viewfinder optical system with variable observation direction of the present invention emits a light beam based on a subject image formed by an objective lens through a first triangular prism having a reflective surface, and After reflecting with a removable reflective member installed in the optical path,
A first observation system that uses the light flux to observe the subject image from waist level after passing through the first triangular prism again;
A second observation system is provided, which allows the light beam that has passed through the triangular prism to pass through a second triangular prism having a reflective surface, and then uses the light beam to observe the object image from eye level, It is characterized by making the observation direction variable by inserting and removing a member into the finder optical path.

(Embodiment) FIG. 1 is a schematic diagram of a main part of an embodiment of a photographing system when the present invention is applied to an eye reflex camera using a penta roof prism. In the figure, 11 is a luminous flux from an unillustrated subject;
1 is an objective lens, 2 is a quick return mirror,
A light beam 11 from the objective lens 1 is reflected upward where a focusing plate 3, which will be described later, is arranged. Reference numeral 3 denotes a focusing plate, on which a subject image is formed by the objective lens 1.

4 is a penta roof prism, which corrects the subject image formed on the focusing plate 3 into an erect image.

Reference numeral 5 denotes a first triangular prism according to the invention, which is provided behind the pentagonal roof prism 4, and the first triangular prism 5 has an entrance surface 5a substantially perpendicular to the optical axis and the entrance surface. an inclined surface 5b inclined at a certain angle with respect to the optical axis, which totally reflects the light beam incident from 5a downward; and the inclined surface 5
It has an exit surface 5c from which the reflected light beam from b is emitted.

6 is a second triangular prism, and the first triangular prism 5
an entrance surface 6a facing the exit surface 5c; a reflection surface 6b tilted at a certain angle with respect to the optical axis that totally reflects the light flux incident from the entrance surface 6a in a direction opposite to the subject side; and the reflection surface 6b. It has an exit surface 6c from which a reflected light beam is emitted.

Further, a certain air gap is provided between the exit surface 5c of the first triangular prism 5 and the entrance surface 6a of the 203rd prism 6 so that a reflecting member 7, which will be described later, can be inserted and removed.

7 is a reflecting member, and the exit surface 5 of the first triangular prism 5
It consists of a reflecting mirror with a reflecting surface 7a on the c side, and the first
Near the exit surface 5c of the triangular prism 5, that is, the exit surface 5c
and the entrance surface 6a of the second triangular prism 6.

8 is the third triangular prism, and the first triangular prism 5
It has an entrance surface 8a facing the inclined surface 5b, and an exit surface 8b from which the light flux incident from the entrance surface 8a is emitted.

9a is the second eyepiece, 9b is the first eyepiece, 10a
, 10b are eye points 1 to 1, respectively.

Next, the shapes and optical effects of the first triangular prism 5, the second triangular prism 6, and the reflecting member 7, which are the characteristics of the present invention, will be explained using FIG. 2.

Figures 2 (/l) and (B) are explanatory diagrams showing the method of switching the observation direction, and Figure 2 (A) is for the second observation system, that is, at eye level (eye level finder optical system); (B) shows the observation state in the first observation system, that is, at waist level (waist level finder optical system).

The first triangular prism 5 has an entrance surface 5a substantially perpendicular to the optical axis and an entrance surface 5a as shown in FIGS.
an inclined surface 5b inclined at a certain angle with respect to the optical axis, which totally reflects downward the light beam incident from the
It has an exit surface 5c from which a reflected light beam is emitted.

The second triangular prism 6 has an entrance surface 6a facing the exit surface 5c of the first triangular prism 5, as shown in FIGS. It has a reflecting surface 6b inclined at a certain angle with respect to the optical axis for reflection or total reflection in a direction opposite to the side, and an exit direction 6c for emitting the reflected light beam from the reflecting surface 6b. still,
The reflective surface 6b is formed by vapor deposition of aluminum or the like.

The reflecting member 7 is made up of a reflecting mirror having a reflecting surface 7a on the exit direction side of the first triangular prism 5, as shown in FIG. 2(B). Note that the reflective surface 7a is formed, for example, by vapor deposition of aluminum or the like.

In this embodiment, two triangular prisms 5 having such shapes,
6 and the reflecting member 7, when used as an eye-level finder optical system (second observation system), the reflecting member 7 is retracted out of the finder optical path as shown in FIG.

As a result, the light beam entering from the entrance surface 5a of the first triangular prism 5 is totally reflected downward by the inclined surface 5b and exits from the exit surface 5c. The light flux emitted from the exit direction 5c enters the second triangular prism 6 through the entrance surface 6a, is reflected by the reflection surface 6b in a direction opposite to the subject side, and exits from the exit surface 6c. The light beam emitted from the exit direction 6c is the second
The light is incident on the eyepiece lens 9a.

Also, waist level finder optical system (first observation system)
When used as
c and the incident surface 6a of the second triangular prism 6 are inserted into the finder optical path with an air gap formed (see Fig.
11) condition).

At this time, the angle θ7 between the normal line of the reflective surface 7a of the reflective member 7 and the optical axis is approximately 10° (the incident light beam totally reflected on the inclined surface 5b exits from the exit direction 5c and enters again from the exit surface 5c). Considering the width of the luminous flux of ±10° in order to transmit it through the inclined surface 5b, the luminous flux reflected by the reflective member 70 and the reflective surface 7a will be 20°.
It is installed diagonally so that the deflection must be approximately 1°.

As a result, as shown in FIG. 5B, the light beam incident from the entrance surface 5a of the first triangular prism 5 is totally reflected downward by the inclined surface 5b and exits from the exit direction 5c. and injection direction 5
The light beam emitted from c is reflected by the reflecting member 7'rf7i7
a is reflected upward and enters the first triangular prism 5 again. The light beam incident from the exit direction 5c of the first triangular prism 5 exits from the inclined surface 5b of the first triangular prism 5, passes through the third triangular prism 8, and enters the first eyepiece 9b. ing.

As described above, in this embodiment, the optical path of the finder is provided near the exit surface 5c of the first triangular prism 5, that is, between the exit surface 5c and the entrance surface 6a of the second triangular prism 6. A reflecting member 7 is provided to be freely inserted and removed, and the observation direction is changed by inserting and removing the reflecting member 7.

This changes the observation direction to the eye level direction (second observation system).
Alternatively, one of the waist level directions (first observation system) can be selectively and easily switched to observe the subject image.

Next, conditions regarding the shape of the first triangular prism 5 and the setting angle of the reflecting member 7 according to this embodiment will be explained using FIG. 2(C).

Now, if the first triangular prism 5 is a right-angled prism for convenience and the angle between the normal line of the inclined surface 5b of the first triangular prism 5 and the optical axis L1 is 05, then the angle 05 is the first triangular prism. For example, if the refractive index of the material of the first triangular prism 5 is nl, then the entire finder light flux incident on the finder 5 (assuming an aperture angle of approximately ±100) must be totally reflected by the inclined surface 5b. You have to be satisfied when you do it.

At this time, the angle α1 of the first triangular prism 5 shown in the same figure
can be calculated using the formula α1-90°-05.

Further, if the angle between the normal line of the inclined surface 5b of the first triangular prism 5 and the bent optical axis L3 is 08, then the angle θ
Reference numeral 8 indicates a luminous flux that has been totally reflected on the inclined surface 5b, exits from the exit surface 5c, is reflected on the reflective surface 7a of the reflective member 7, and enters the first triangular prism 5 again (with an opening angle of approximately ±10°). (assumed) must be emitted to cause total reflection on the inclined surface 5b, so the formula must be satisfied.

Here, if the angle between the normal line of the reflective surface 7a of the reflective member 7 and the bent optical axis L2 is 07, then the angle θ8 can be found as θ8−α1−07.

Also, the angle θ7 at this time is θ7=900-2α1 It can be found by

Hereinafter, the first triangular prism 5 is treated as a right-angled prism, but even if it is not a right-angled prism, the shape of the first triangular prism 5 can be obtained in the same manner as described above.

Accordingly, in this embodiment, the shape of the first triangular prism 5 and the setting angle of the reflecting member 7 are specified and configured so as to satisfy the conditional expressions (]) and (2).

This allows the luminous flux from the subject to be efficiently focused at eye level.
or the corresponding 1st. The light is guided to the second eyepiece.

In this embodiment, since the removable reflective member 7 is relatively small, the entire apparatus can be easily miniaturized, and a finder optical system with variable observation direction can be achieved.

Also, 1st. Second. If the third triangular prisms 5, 68 are molded from a material such as resin, they can be manufactured at a very low cost and have the advantage of being able to reduce costs.

FIG. 3 is a schematic diagram of main parts of another embodiment when the present invention is applied to a finder optical system of a lens shutter camera or the like.

In this figure, the same elements as those shown in FIG. 1 are given the same reference numerals. Note that 12 is an objective lens of a finder system.

In this embodiment, a light beam from an object (not shown) is diverged by the objective lens 12 and enters the first triangular prism 5.

At eye level (second observation system), the reflecting member 7 is retracted out of the finder optical path as shown by the dotted line in the figure.

The luminous flux incident from the entrance surface 5a of the first triangular prism 5 is totally reflected downward by the inclined surface 5b and exits from the exit surface 5c. As shown by the dotted line in the figure, the light beam emitted from the exit surface 5c is directed to the entrance surface 6a of the second triangular prism 6.
The light is incident on the reflective surface 6b and reflected in the opposite direction to the subject side.
Alternatively, the light is totally reflected, exits from the exit surface 6c, and reaches the eyepoint 10a via the second eyepiece 9a. This allows the subject image to be observed from the eye level direction.

Next, at waist level (first observation system), the reflection member 7, which had been retracted outside the finder optical path, is placed between the exit surface 5c of the first triangular prism 5 and the second triangular prism 5, as shown by the solid line in the figure. It is inserted into the finder optical path with an air gap provided between it and the incident surface 6a of No. 6.

At this time, the reflective member 7 is installed diagonally so that the angle between the normal line of the reflective surface 7a and the optical axis is approximately 10 degrees.

As a result, the light beam entering from the entrance surface 5a of the first triangular prism 5 is totally reflected downward by the inclined surface 5b and exits from the exit surface 5c. Then, the light beam emitted from the exit surface 5c is reflected upward by the reflection surface 7a of the reflection member 7, and is again reflected from the exit surface 5c.
The light enters the first triangular prism 5 from c. Then, the light beam passes through the inclined surface 5b of the first triangular prism 5 and passes through the third triangular prism 5.
The light passes through the triangular prism 8 and reaches the eyepoint 10b via the first eyepiece 9b. This allows the subject image to be observed from the waist level direction.

As described above, in this embodiment, the first triangular prism 5 having a predetermined shape that satisfies the above-mentioned conditional expressions (]) and (2) is arranged between the objective lens 12 and the observer, and the first triangular prism 5 is arranged between the objective lens 12 and the observer. A removable reflection member 7 is provided in the finder optical path with an air gap provided near the exit surface 5c of the prism 5, that is, between the exit surface 5c and the entrance surface 6a of the second triangular prism 6. Using the member 7, the reflecting member 7 is retracted out of the finder optical path when the object is at eye level, and the reflecting member 7 is inserted into the finder optical path when the object is at waist level.

As a result, the subject image is observed by selectively switching the light flux from the subject to either the eye level direction (second observation system) or the waste-first-hell direction (first observation system).

In addition to the embodiments described above, the present invention can be widely applied to various finder optical systems (observation optical systems) such as real-image finder optical systems such as video cameras and binoculars.

In addition, in the embodiments described so far, the first. The second and third triangular prisms 5, 6.8 are arranged between the objective lens and the eyepiece lens, or the first triangular prism 5, 6.8 is arranged behind the eyepiece lens 9c, as shown in FIG. Second. A third triangular prism 5, 68 may also be arranged.

That is, as shown in FIG. 6, an eyepiece lens 9c is arranged behind the pentagonal roof prism 4, and a first eyepiece lens 9c is arranged behind it. Second. The third triangular prism 5, 6.8 is arranged, and the eyepiece 9c
It is also possible to divide the luminous flux after passing through into the eye level direction and the waist level direction. According to this method, the eyepiece can be manufactured at a low cost with just one eyepiece.

90 (Effects of the Invention) According to the present invention, a first lens having a predetermined shape is provided behind the objective lens. The second triangular prism is efficiently arranged at a certain air interval, and a removable reflection member is installed in the finder optical path near the exit surface of the first triangular prism. By inserting and removing the reflective member, the entire device can be made more compact, and with an inexpensive and simple configuration, the subject image can be selectively viewed either in the eye-level direction or in the waist-level direction. A finder optical system with variable observation direction can be achieved.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of the main parts of an embodiment of a photographing system when the present invention is applied to an eye reflex camera using a penta roof prism, and Figures 2 (8), (B), and (fl:) are FIG. 3 is an explanatory diagram showing a method for switching the observation direction in the present invention, and FIG.
S41Δ(A), CB), FIG. 5 is a schematic diagram of a main part of a conventional finder optical system, and FIG. 6 is a schematic diagram of a main part of another embodiment of the present invention. In the figure, 1.11 is an objective lens, 2 is a quick return mirror, 3 is a focusing plate, 4 is a penta roof prism, 5 is a first triangular prism, 5a is an entrance surface, 5b is an inclined surface, 5c
is the exit surface, 6 is the second triangular prism, 6a is the entrance surface, 6
b is a reflective surface, 6c is an exit surface, 7 is a reflective member, 7a is a reflective surface, 8 is a third triangular prism, 8a is an entrance surface, 8b is an exit surface, 9a is a second eyepiece, 9b is a first eyepiece,
10a and 10b are eye points, and 11 is a luminous flux.

Claims (2)

[Claims] (1) The light beam based on the subject image formed by the objective lens is emitted through a first triangular prism having a reflective surface, reflected by a removable reflective member provided in the finder optical path, and then reflected again. A first observation system that uses the light beam to observe the subject image from waist level after passing through the first triangular prism; and a first observation system that retracts the reflecting member from the finder optical path and passes through the first triangular prism. A second observation system is provided, which passes the light flux through a second triangular prism having a reflective surface, and then uses the light flux to observe the subject image from eye level, and the reflection member is placed in the finder optical path. A viewfinder optical system with a variable observation direction, characterized in that the observation direction can be changed by inserting and removing the viewfinder. (2) An incident surface (5a) that is substantially perpendicular to the optical axis for the light beam based on the subject image formed by the objective lens, and an optical axis that totally reflects the light beam incident from the incident surface (5a) in a predetermined direction. The light is emitted after passing through a first triangular prism having an inclined surface (5b) that is inclined at a certain angle with respect to A light beam is reflected by a removable reflection member provided in the finder optical path near the surface (5c), is incident on the exit surface (5c) of the first triangular prism, and is emitted from the inclined surface (5b). A first observation system for observing the subject image from waist level, and a light beam emitted from the exit surface (5c) of the first triangular prism by retracting the reflecting member from the finder optical path. Injection surface (5c
), a reflecting surface (6b) tilted at a certain angle with respect to the optical axis that reflects the light flux incident from the incident surface (6a) in a predetermined direction;
) and a second triangular prism having an exit surface (6c) for emitting the reflected light flux from the second triangular prism, the second observation system is configured to observe the subject image from eye level using the light flux emitted after passing through the second triangular prism. What is claimed is: 1. A finder optical system having a variable observation direction, characterized in that the observation direction is made variable by inserting and removing the reflecting member into the finder optical path.