JPH0720538A - Optical system for finder of camera - Google Patents

Abstract

PURPOSE:To provide the finder optical system of a camera which is compact and light in weight. CONSTITUTION:Light from an object G1 is made incident on the incident surface 4a of an optical fiber assembly 4 through a photographing lens 1, a quick-return mirror 2 and a condenser lens 3 and the image of the object G2 is formed. The object image G2 formed on the surface 4a is rotated by 180 deg. in the inside of the assembly 4 and it appears on a light exit surface 4b as an image G3. The image G3 on the surface 4b is made incident on the pupil of an observer through a reflecting mirror 5 and an eyepiece 6 and it can be abserved as an erected image. The assembly 4 is constituted by closely bringing the optical fibers whose diameters are <=30mum into contact with each other, bundling them in parallel, twisting them and rotating the incident surface 4a and the light exit surface 4b by 180 deg.. Since an inverted image can be changed to the erected image by short optical path length without using a prism or an erecter lens, the camera can be made compact and light in weight.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera finder optical system.

[0002]

2. Description of the Related Art As shown in FIG. 7, a finder optical system of a conventional single-lens reflex camera includes a taking lens 31, a kite titanium mirror 32, a focusing plate 33 arranged on the focal plane of the taking lens, and an upper and lower image. It is composed of a penta roof prism 34 for reversing left and right, and an eyepiece lens 35. In addition, F shows a film surface.

Photographing lens 31, kit clear mirror
The object scene image formed on the focusing screen 33 through 32 is inverted by the penta roof prism 34 to form an erect image, and the erect image is magnified and observed through the eyepiece lens 35. Therefore, it is possible to easily determine the focus state and focus.

In a real image type finder optical system other than a single-lens reflex camera, a Porro prism, a Petit Yang prism, an optical system including an objective lens and an eyepiece lens,
Alternatively, a structure is adopted in which an erector lens (relay lens) or the like is arranged, an inverted image formed by the objective lens is rotated into an erect image, and this erect image is magnified and observed by an eyepiece lens.

[0005]

As described above, the conventional finder optical system of a single-lens reflex camera requires a penta roof prism and a focusing screen for inverting the image vertically and horizontally, and also a real image type finder optical. In systems that use Porro prisms, Petit Yang prisms, etc. to rotate an inverted image into an erect image, it takes time to process the prism, and the size of the prism is large and the weight is considerable. This is an obstacle to miniaturization and weight reduction, and measures for it have been required. Further, in the case where the erector lens is used to rotate the inverted image into the erect image, the optical path length of the finder optical system becomes long, which also hinders the downsizing and weight saving of the camera. The present invention is intended to solve the above problems.

[0006]

SUMMARY OF THE INVENTION The present invention is to solve the above-mentioned problems, and an objective lens having a positive power and a positive power for enlarging a subject image formed by the objective lens.
In a finder optical system of a camera composed of an eyepiece lens having a
The optical fiber assembly that rotates 0 ° is arranged between the objective lens and the eyepiece lens, and the condenser lens is arranged close to the incident surface of the optical fiber assembly.

[0007]

In order to rotate the inverted image formed by the objective lens into the erected image, an optical fiber assembly which rotates the image by 180 ° between the entrance surface and the exit surface is used. As a result, an inverted image can be converted into an erected image with a short optical path length without using a prism or an elector lens, and the camera can be made compact and lightweight.

[0008]

Embodiments of the present invention will be described below.
1 and 2 show a first embodiment of the present invention.
1 shows a finder optical system of a single-lens reflex camera. In FIGS. 1 and 2, 1 is a taking lens, 2 is a quartz lens mirror, 3 is a condenser lens, 4 is an optical fiber assembly, and its incident surface 4a is aligned with the image forming surface of the taking lens. Will be placed. Further, 5 is a reflection mirror, and 6 is an eyepiece lens.

As shown in FIG. 3, the optical fiber assembly 4 closely bundles optical fibers having a diameter of 30 .mu.m or less in parallel and twists them, and makes their incident surface 4a and exit surface 4b 180 degrees.
It is configured by rotating. Optical fiber assembly 4
The image ga (see FIG. 3A) formed on the incident surface 4a of
It rotates 180 ° and appears as an image gb on the exit surface 4b (see FIG. 3B). The diameter of the optical fiber is preferably 30 μm or less, and when it is 30 μm or more, the shape of the end face of the optical fiber becomes clear and the quality as a fiber deteriorates.

FIG. 1 shows a state in which the fiber optics system is set in the operating position. The reflection mirror 5 is set at a position inclined by 45 ° above the optical fiber assembly 4.
The eyepiece lens 6 is also set at a position corresponding to this.

At the operating position of the fiber optics system shown in FIG. 1, the light from the subject G1 is incident on the incident surface 4a of the optical fiber assembly 4 through the taking lens 1, the kite titanium mirror-2 and the condenser lens 3. Then, the subject image G2 is formed. The subject image G2 formed on the entrance surface 4a is rotated by 180 ° inside the optical fiber assembly 4 and appears as an image G3 on the exit surface 4b. The image G3 appearing on the exit surface 4b enters the observer's pupil through the reflection mirror 5 and the eyepiece lens 6 and can be observed as an erect image.

FIG. 2 shows a state in which the finder optical system is set to the storage position. In this position, the reflection mirror 5 is rotated around the axis 5a and is brought down to a position parallel to the upper side of the optical fiber assembly 4, and the eyepiece 6 is also lowered behind the optical fiber assembly 4. The height of the entire camera can be reduced, which is convenient for carrying.

Next, a second embodiment will be described. FIG. 4 shows a second embodiment of the present invention, which is a real image type fiber optic system used in a video camera or the like, in which an optical fiber assembly is used in place of the conventionally used erector lens. It was used.

In FIG. 4, 11 is a taking lens, 12 is a prism, 13 is an image forming lens, and F is a focal plane of the taking lens. Reference numeral 15 is an optical fiber assembly, which has the same structure as that shown in FIG. 16 is a prism, 1
Reference numeral 7 represents an eyepiece lens. The end faces of the prism 12 and the prism 16 are spherical and configured to act as a condenser lens.

The light from the subject passes through the taking lens 11, the prism 12 and the imaging lens 13 to form a subject image on the focal plane F. For example, in a video camera, a subject image formed on the focal plane F is converted into an image signal by a detection unit (not shown) arranged on the focal plane F and recorded. On the other hand, the light from the subject that is reflected by the reflecting surface of the prism 12 and heads for the fiber optics system is incident on the optical fiber assembly 15 and the incident surface 1
A subject image is formed on 5a. The image formed on the entrance surface 15a is rotated by 180 ° inside the optical fiber assembly 15 and appears on the exit surface 15b. The image appearing on the exit surface 15b is reflected by the prism 16, enters the observer's pupil through the eyepiece lens 17, and can be observed as an erect image.

Next, a third embodiment will be described. FIG. 5 shows a third embodiment of the present invention, which is a real-image type finder optical system constructed separately from the taking lens, and uses a light instead of the conventionally used image rotating prism or erector lens. It uses a fiber assembly.

In FIG. 5, reference numeral 21 is an objective lens, 22 is a wedge prism for correcting the parallelism caused by the fact that the optical axis of the photographing lens and the optical axis of the finder optical system do not coincide.
23 is the first condenser lens, 24 is the field frame, and 25
Is an optical fiber assembly having the same structure as that shown in FIG. Reference numeral 26 is a second condenser lens, and 27 is an eyepiece lens.

The light from the subject enters the optical fiber assembly 25 through the objective lens 21, the wedge prism 22, and the first condenser lens 23, and forms a subject image on the incident surface 25a. The image formed on the incident surface 25a is an optical fiber.
It rotates 180 ° inside the aggregate 25 and appears on the exit surface 25b. The image that appears on the exit surface 25b is the second condenser
The light enters the observer's pupil through the lens 26 and the eyepiece 27 and can be observed as an erect image. The correction of the parallax is performed by moving the wedge prism 22 in a direction crossing the optical axis according to the subject distance.

In a real image type finder optical system using an image rotating prism such as a Porro prism,
Since the reflecting surface of the image rotating prism may enter the space of the objective lens, the space for inserting the wedge prism is limited. However, when the optical fiber assembly is used, it is possible to secure a sufficient space for inserting the wedge prism between the objective lens and the optical fiber assembly.

In a real image type finder optical system using an erector lens, an optical path length of about 4 times the focal length of the erector lens is required for image rotation, so that the finder optical system The optical path length becomes long. However, when the optical fiber assembly is used, the optical path length of the fiber optics system can be shortened because the image can be rotated only by the thickness of the optical fiber assembly.

In the third embodiment, the field frame 24 can be provided on the entrance surface 25a of the optical fiber assembly 25. In this case, as shown in FIG. 6, the field frame 24, the parallel correction mark 24a, and the distance measuring area display mark 24b.
If these are integrally formed by vapor deposition of a suitable material or by coating, the whole can be made small and the workability can be improved.

The above is an explanation of the fiber optic system of the camera of the present invention. However, the optical fiber assembly used here is not limited to the camera fiber optic system of the camera, but an optical system that requires image rotation. Needless to say, it can be applied to, for example, the optical system of binoculars.

[0023]

As described above, according to the present invention, in order to convert the inverted image formed by the objective lens into the erect image, the light which rotates the image by 180 ° between the incident surface and the exit surface. Since the fiber aggregate is used, the Porro prism,
Since it is possible to rotate an inverted image into an erected image with a short optical path length without using a Petchan prism, an elector lens, etc., and since the incident surface of the optical fiber integrated body can be used as a focusing screen. It is possible to reduce the number of parts constituting the finder optical system, and to reduce the size and weight of the camera.

[Brief description of drawings]

FIG. 1 is a sectional view of a finder optical system of a single lens reflex camera according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a state in which the finder optical system according to the first embodiment is set at a storage position.

FIG. 3 is a perspective view illustrating a configuration of an optical fiber assembly.

FIG. 4 is a sectional view of a real image type finder optical system according to a second embodiment.

FIG. 5 is a sectional view of a real image type finder optical system according to a third embodiment.

FIG. 6 is a perspective view illustrating a field frame formed on an optical fiber assembly according to a third embodiment.

FIG. 7 is a sectional view of a finder optical system of a conventional single-lens reflex camera.

[Explanation of Codes] 1, 11 Photographing lens 21 Objective lens 2 Quitecturnal mirror 3, 23, 26 Condenser lens 4, 15, 25 Optical fiber aggregate 5 Reflective mirror 12, 16 Prism 6, 17, 27 Eyepiece Lens 22 Wedge prism 24 Field frame

Claims (1)

[Claims] 1. A finder optical system for a camera comprising an objective lens having a positive power and an eyepiece lens having a positive power for enlarging a subject image formed by the objective lens. An optical fiber assembly that rotates the image by 180 ° with respect to the exit surface is disposed between the objective lens and the eyepiece lens,
A camera finder characterized in that a condenser lens is arranged close to the incident surface of the optical fiber integrated body.
Optical system.