JP2536061B2 - Optical system having optical path bending means - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical system having an optical path bending means, and in particular, in a camera such as a photographic camera, a video camera, etc., the thickness of the camera in the vertical direction is thinned. The present invention relates to an optical system having an optical path bending unit suitable for downsizing of the whole.

(Prior Art) Conventionally, in an optical system of a single-lens reflex camera such as a photographic camera or a video camera, a photoreceptive surface 53 is arranged behind an optical axis of a taking lens 51 as shown in FIG. are doing.

Further, the light flux that has passed through the taking lens 51 is reflected upward by the rotating mirror 52 disposed behind the taking lens to form a finder image on the surface of the focusing plate 54. Then, the finder image on the surface of the focusing plate 54 is observed through the condenser lens 55 and the pentaprism 56 as an erect normal image by the eyepiece lens 57, thereby forming a finder system.

As described above, in the conventional single-lens reflex camera, the turning mirror 52 reflects the finder light beam upward of the camera body,
A pentaprism arranged above the taking lens 51 is used to obtain an erected finder image. For this reason, the pentaprism, which is a part of the constituent elements of the finder system, protrudes above the camera body, and when the photographic lens is attached to the camera body, the entire camera tends to become relatively large. In particular, in the configuration using the conventional pentaprism, the shape is partially projected, and it is very difficult to reduce the thickness of the entire camera in the vertical direction.

Further, when a zoom lens or a telephoto lens is used, the photographing system tends to protrude and the entire camera tends to increase in size.

(Problems to be Solved by the Invention) The present invention does not use a conventional pentaprism, but appropriately arranges a plurality of reflecting mirrors as an optical path bending means and a condenser lens or an image forming lens to perform photographing. An object of the present invention is to provide an optical system having an optical path bending means that efficiently stores a system and a finder system in a thin space as a whole, and facilitates thinning and miniaturization of the entire camera.

Another object of the present invention is to provide a compact optical system for a single-lens reflex camera in which the photographing system does not significantly project even when a zoom lens or a telephoto lens is used.

(Means for Solving Problems) Behind the taking lens, approximately 45 ° with respect to the optical axis of the taking lens.
After reflecting the light flux that has passed through the taking lens by the first reflecting mirror arranged at a predetermined angle, the optical axis of the taking lens and the first
An optical system that guides the light flux of the taking lens to a photosensitive surface that is arranged in parallel with the first plane formed by the first reflected light flux reflected by the reflecting mirror, and is a circuit that is parallel to the first plane. A second reflecting mirror having a moving axis is provided, and the first reflected light flux is guided to the photosensitive surface by tilting at an angle of about 45 degrees with respect to the first reflected light flux at the time of shooting, and the first light flux is observed at the time of finder image observation.
It is configured such that the first reflected light flux is guided in a direction opposite to the photosensitive surface while being inclined by about 45 degrees with respect to the reflected light flux and guided to the eyepiece lens.

In addition to this, in the present invention, the light flux passing through the taking lens is reflected by the first reflecting mirror disposed behind the taking lens at approximately 45 degrees with respect to the optical axis of the taking lens, and reflected by the first reflecting mirror. By the rotatable second reflecting mirror in which the first reflected light flux is arranged at about 45 degrees with respect to the first reflected light flux, with respect to the first plane formed by the optical axis of the photographing lens and the first reflected light flux. And a second reflecting mirror configured to guide the second reflected light flux reflected by the second reflecting mirror in a substantially vertical direction onto a photosensitive surface arranged parallel to the optical axis of the photographing lens and the second reflecting light flux. The mirror is rotated to reflect the first reflected light flux reflected by the first reflecting mirror in a direction opposite to the photosensitive surface, and then the third reflected mirror reflects the first reflected light flux in a direction parallel to the first reflected light flux. It is reflected in a direction parallel to the optical axis of the taking lens by a fourth reflecting mirror arranged perpendicular to the first plane. And a finder system configured to guide light to the eyepiece lens.

(Embodiment) FIG. 1 and FIG. 2 are schematic views of the essential parts showing the optical paths of a photographing system and a finder system in an optical system having an optical path bending means of the present invention. However, in FIG. 1, some members constituting the finder system shown in FIG. 2 are omitted.

In FIG. 1, 11 is a zoom lens capable of zooming, M1.
Is a first reflecting mirror, which is substantially aligned with the optical axis S1 of the taking lens 11.
It is arranged at 45 degrees and reflects the light flux L from the taking lens 11 in the direction orthogonal to the optical axis S1.

M2 is a second reflecting mirror, which is approximately 45 with respect to the first reflected light beam L1.
It is arranged every time. The second reflecting mirror M2 is the first reflecting mirror L1.
Is reflected as a second reflected light flux L2 in a direction substantially perpendicular to a first plane formed by the light flux L on the optical axis of the photographing lens 11 and the first reflected light flux L1 of the light flux L by the first reflecting mirror M1. The light is guided to the photosensitive surface 13 such as a film or a CCD. The second reflector M2
Is set to be rotatable about an axis 14 in the first plane or parallel to the first plane as shown in FIG.

In this embodiment, a photographing system is composed of the photographing lens 11 and the first and second reflecting mirrors M1 and M2.

In FIG. 1, numeral 15 is a film cartridge.

FIG. 2 shows the second reflecting mirror M2 in FIG.
It is a principal part schematic diagram when a finder system is constituted by rotating 90 degrees.

In the figure, the light flux L from the taking lens 11 is reflected by the first reflecting mirror M1 as a first reflected light flux L1 in a direction orthogonal to the optical axis S1, and then is reflected by the second reflecting mirror M2 in a direction opposite to the photosensitive surface 13. The second reflected light beam L2 is reflected in the direction perpendicular to the first plane,
A finder image b of an object a is formed on the surface of a focusing plate 16 formed of a Fresnel surface that is optically equivalent to the photosensitive surface 13.

The light flux from the finder image on the surface of the focusing plate 16 is condensed by the condenser lens 17 and reflected by the third reflecting mirror M3 as the third reflected light flux L3 in the direction orthogonal to the optical axis S1. Then, after being reflected in a direction substantially parallel to the optical axis S1 of the taking lens 11 by a fourth reflecting mirror M4 arranged so as to have a reflecting surface in a direction perpendicular to the first plane, it is reflected by an eyepiece lens 18 via an eyepiece shutter 19. It is guiding light. Then, the finder image formed on the surface of the focusing plate 14 is observed through the eyepiece lens 18 in an upright state.

The eyepiece shutter 19 is provided in the vicinity of the eyepiece lens 18 in order to prevent the reverse incident light from the eyepiece lens 18 side from entering the photosensitive surface 13 during photographing.

In the finder system in this embodiment, each element is set so that the optical axis S1 of the taking lens and the optical axis S2 of the finder system are substantially parallel to each other in order to facilitate observation of the finder image.

In this embodiment, the first to fourth reflecting mirrors, the condenser lens, and the eyepiece lens constitute a part of the finder system.

In the present embodiment, when a focal plane shutter is used in the vicinity of the photosensitive surface 13, exposure is performed in the same manner as in a normal single lens reflex camera.

When a lens shutter is used, for example, the lens shutter and the eyepiece shutter are closed, while the second reflecting mirror M2 is rotated 90 ° about the axis 14 from the viewfinder observation state to the photographing state, and then the lens shutter is opened. Open and close to expose. After that, the second reflecting mirror M2 is returned to the finder observation state, and the lens shutter and the eyepiece shutter are opened to restore the original state.

In the embodiment shown in FIG. 1, when the screen size is a so-called half size, it is extremely small and a horizontally long field of view can be obtained by holding the horizontal position like binoculars.

FIG. 3 is a schematic view of an essential part showing an optical path of a finder system in an optical system having an optical path bending means of the present invention. In the figure, the same elements as those shown in FIG. 2 are designated by the same reference numerals.

In this embodiment, the third reflecting mirror used in the embodiment shown in FIG.
It is composed of a reflection type prism body 31 in which M3 and the fourth reflecting mirror M4 are integrated. In the reflection type prism body 31, 31a and 31b are reflecting surfaces, and correspond to the third and fourth reflecting mirrors M3 and M4, respectively.

In this embodiment, a reflection type prism body 31 as shown in the figure is provided in the finder optical path to shorten the air-equivalent length, thereby improving the finder magnification.

In each of the above embodiments, the first reflecting mirror M1 may be a reflection type right angle prism.

According to the present invention, the photographing system and the finder system are switched by rotating the final reflecting mirror of the plurality of reflecting mirrors arranged behind the photographing lens about a predetermined axis, and the photographing system By increasing the length of the common optical path between the camera and the viewfinder system, we have achieved an optical system that achieves a thin and compact camera as a whole.

In particular, by properly setting a plurality of reflecting mirrors and lenses as described above, the TTL viewfinder system is downsized and the overall thickness of the camera is facilitated.

[Brief description of drawings]

FIG. 1 and FIG. 2 are schematic views of the essential parts showing the optical paths of the photographing system and the finder system in one embodiment of the present invention, and FIG. 3 is the viewfinder system in another embodiment of the present invention. FIG. 4 is a schematic view of a main part showing an optical path, and FIG. 4 is a schematic view of an optical system of a conventional single-lens reflex camera. In the figure, 11 is a photographing lens, 14 is a rotation axis, 13 is a photosensitive surface, 16 is a focusing plate, 17 is a condenser lens, M1 is a first reflecting mirror,
M2 is the second reflecting mirror, M3 is the third reflecting mirror, M4 is the fourth reflecting mirror, L
Is a light beam, L1 is a first reflected light beam, L2 is a second reflected light beam, L3 is a third reflected light beam, an 18 eyepiece lens, and 19 is an eyepiece shutter.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Oizumi 770 Shimonoge, Takatsu-ku, Kawasaki-shi, Kanagawa Canon Inc. Tamagawa Plant (56) References JP-A-60-200244 (JP, A) JP-A-57- 196224 (JP, A) Actually open 61-70840 (JP, U)

Claims (1)

(57) [Claims] 1. A first reflecting mirror disposed behind the taking lens at an angle of about 45 degrees with respect to the optical axis of the taking lens, reflects the light flux passing through the taking lens, and then, with the optical axis of the taking lens. An optical system for guiding the light flux of the taking lens to a photosensitive surface arranged in parallel with a first plane formed by the first reflected light flux reflected by the first reflecting mirror, the optical system including: It has a second reflecting mirror having a parallel rotation axis, guides the first reflected light flux to the photosensitive surface by inclining about 45 degrees with respect to the first reflected light flux at the time of photographing, and makes the first reflection at the time of finder image observation. An optical system having an optical path bending means, characterized in that the first reflected light flux is guided in a direction opposite to the photosensitive surface at a tilt of about 45 degrees with respect to the light flux and guided to an eyepiece lens.