JPH01295244A - Optical system provided with optical path folding means - Google Patents

Abstract

PURPOSE:To thin and miniaturize an entire camera by turning a 2nd reflecting mirror and a semi-transparent mirror centering around a certain axis, appropriately arranging respective reflecting mirrors, lenses and a roof reflecting mirror, etc., and setting the respective elements so that a part of the optical path of a finder system, especially, can be used in going and coming. CONSTITUTION:The 1st reflecting mirror M1 is arranged at nearly 45 deg. against the optical axis S1 of a photographic lens 11 and a 2nd reflecting mirror M2 is arranged at nearly 45 deg. against 1st reflected luminous flux L1. The finder system is so constituted that the primary image of an object is formed near a field lens 17 arranged in a position almost optically equal to the image forming position of the photographic lens 11 and retroduced in the original optical path through an image-formation lens 18 and roof reflecting surface 19 to form the secondary image of the object which is an erect non-reverse image near the field lens 17 through the image-formation lens 18 again, then the secondary image of the object can be observed with an eyepiece lens 20 through the semi-transparent mirror M3. Thus, the entire camera can be easily thinned and miniaturized.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an optical system having an optical path bending means, and in particular to a camera such as a photographic camera, a video camera, etc., by reducing the vertical thickness of the camera. The present invention relates to an optical system having an optical path bending means suitable for downsizing the entire system.

(Prior Art) Conventionally, in the optical system of a single-lens reflex camera such as a photographic camera or a video camera, a photosensitive surface 53 is arranged at the rear on the optical axis of a photographing lens 51 to form a photographing system, as shown in FIG. are doing.

Further, the light flux that has passed through the photographic lens 51 is reflected upward of the camera body by a rotating mirror 52 placed behind the photographic lens to form a finder image on the surface of the focusing plate 54. The finder system is configured such that 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 with the eyepiece lens 57.

In this way, in a conventional single-lens reflex camera, the viewfinder light beam is reflected upward from the camera body by the rotating mirror 52.
A pentaprism placed above the photographing lens 51 is used to obtain an erect finder image. For this reason, the pentaprism, which is part of the components of the finder system, protrudes above the camera body, and when a photographic lens is attached to the camera body, the overall camera tends to become relatively large. In particular, in the conventional configuration using a pentaprism, a portion of the camera has a protruding shape, making it extremely difficult to reduce the thickness of the entire camera in the vertical direction.

(Problems to be Solved by the Invention) The present invention does not use a conventional pentaprism, but instead uses a plurality of reflecting mirrors as optical path bending means, a plurality of lenses for focusing or imaging, and a roof reflecting surface. By appropriately arranging the photographing system and the finder system as a whole in a thin space, the present invention provides an optical system having an optical path bending means that can easily make the entire camera thin and compact. What is the purpose?

(Means for solving the problem) Approximately 45 mm behind the photographic lens with respect to the optical axis of the photographic lens.
A first reflecting mirror arranged at approximately 45 degrees reflects the light beam passing through the photographic lens, and the first reflected light beam reflected by the first reflecting mirror is reflected by a second reflecting mirror arranged at approximately 45 degrees with respect to the first reflected light beam.
A reflecting mirror is used to reflect the second reflected light beam onto a photosensitive surface by reflecting the second reflected light beam by the second reflecting mirror in a direction substantially perpendicular to a first plane formed by the optical axis of the photographic lens and the first reflected light beam. The photographing system configured to guide the light and the second reflecting mirror are evacuated and a semi-transmitting mirror is placed in place of the second reflecting mirror, and the first reflected light beam from the first reflecting mirror is transmitted through the semi-transmitting mirror. After reflecting in a direction parallel to the optical axis of the photographic lens and toward the object side, a primary object image is formed in the vicinity of a field lens arranged at a position optically substantially equal to the imaging position of the photographic lens; Next, after passing through the roof reflection surface from the imaging lens, the original optical path is reversed, and a secondary object image of an erect normal image is formed near the field lens through the imaging lens again. It has a finder system in which an object image is observed with an eyepiece through the semi-transmissive mirror.

(Embodiment) FIGS. 1 and 2 are schematic diagrams showing the optical paths of a photographing system and a finder system, respectively, of the optical system having the optical path bending means of the present invention.

In FIG. 1, reference numeral 11 denotes a photographing lens, which is provided with a lens shutter inside as required. Ml is a first reflecting mirror, which is arranged at approximately 45 degrees with respect to the optical axis S1 of the photographic lens 11, and reflects the luminous flux from the photographic lens 11 as a first reflected luminous flux L1 in a direction perpendicular to the optical axis S1. I'm letting you do it.

M2 is a second reflecting mirror, which is arranged at approximately 45 degrees with respect to the first reflected light beam L1. Further, the second reflecting mirror M2 is configured to be rotatable about an axis 12 that is substantially parallel to a first plane formed by the light beam on the optical axis S1 of the photographing lens 11 and the first reflected light beam L1. There is.

The second reflecting mirror M2 reflects the first reflected light beam L1 in a direction substantially perpendicular to the first plane as a second reflected light beam L2, and guides the light to a photosensitive surface 13 such as a film or a CCD. Note that a light shielding member (not shown) is provided on the photosensitive surface 13 as necessary.

In this embodiment, the photographing lens 11 and the first lens. second reflecting mirror Ml,
The photographing system is composed of M2.

Although not shown, a lens shutter is provided within the photographing lens 11, or a focal plane shutter is disposed between the second reflecting mirror M2 and the photosensitive surface 13, and these shutters expose the photosensitive surface 13. There is.

Next, the finder system will be explained. To switch from the photographing system shown in FIG. 1 to the finder system shown in FIG. move it to any position. Next, the semi-transparent mirror M3 is rotated by a certain angle about an axis 14 perpendicular to the first plane, and moved to a position shown by a solid line in the photographing optical path. When a lens shutter is disposed within the photographic lens 11, the lens shutter is opened. This allows the camera to switch from a shooting system to a viewfinder system.

In this embodiment, when the second reflecting mirror M2 is retracted from the photographing optical path, the entire surface of the photosensitive surface 13 may be covered, and the second reflecting mirror M2 may also have the function of a light shielding member.

In FIG. 2, the first reflected light beam L1 reflected by the first reflecting mirror M1 is reflected by the semi-transmissive mirror M3 in a direction parallel to the optical axis S1 of the photographing lens 11 and toward the object side. Semi-transparent mirror M3
The third reflected light beam L3 reflected by the field lens 1 is arranged at a position optically substantially equal to the imaging plane of the photographing lens 11.
A primary object image 2b of the object 2a is formed near 7. At this time, the primary object image 2b is an inverted left-right right image.

Next, the primary object image 2b is passed through the imaging lens 18 using the lidar reflecting surface 19 to backlight the original optical path, and the imaging effect of the imaging lens 18 again forms a second erect left and right image near the field lens 17. A secondary object image 2C is formed. Then, the secondary object image 2C is transmitted to the eyepiece 2 through the semi-transparent mirror 16.
It is observed by 0. Incidentally, the roof reflection surface 19 is perpendicular to the plane consisting of the light beam and the third reflected light beam L3. Reference numeral 15 denotes an eyepiece shutter, which is provided near the eyepiece lens 20 in order to prevent reverse incident light from the eyepiece lens 20 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 photographing lens and the optical axis S2 of the finder system are substantially parallel to facilitate observation of the finder image.

In this embodiment, the photosensitive surface 13 is
In order to prevent unnecessary light from entering, the second reflecting mirror may be used as described above, or a light shielding member such as a focal brain shutter may be disposed on the photosensitive surface 13'.

In this example, the first. The second reflecting mirror and the semi-transmissive mirror each constitute a part of the optical path bending means.

In this embodiment, a roof reflector 19 is used to reciprocate a part of the optical path of the finder system, thereby making effective use of the space inside the camera and downsizing the entire optical system. Note that other optical members having the same function may be used instead of the roof reflector. Furthermore, by using one field lens and one imaging lens in a reciprocating manner, the sharing of refractive power between each lens is reduced compared to the case where they are used one way, thereby achieving high optical performance.

Next, for example, when there is a lens shutter in the photographic lens 11, in order to switch from the finder system to the photographic system, (a) close the lens shutter in the photographic lens.

(b) Close the eyepiece shutter 15.

(c) The semi-transmissive mirror M3 is retreated from the photographing optical path, and then the second reflecting mirror M2 is introduced into the photographing optical path.

The three steps may be performed simultaneously or in random order.

The photosensitive surface 13 can be exposed to light by opening and closing the lens shutter. Also, switching from the photographing system to the finder system can be performed by reversing the above process.

In this embodiment, a focal brain shutter may be placed in front of the photosensitive surface 13, and in this case, the step (a) described above becomes unnecessary, and the aperture in the photographic lens is appropriately set, and the focal brain shutter is opened and closed. The photosensitive surface may be exposed using the following steps.

In this embodiment, the optical axis S1 and the optical axis S2 may not be parallel to each other, but may be configured to be inclined depending on the purpose.

(Effects of the Invention) According to the present invention, as described above, the second reflecting mirror and the semi-transparent mirror can be rotated around a fixed axis, and each reflecting mirror, lens, roof reflecting mirror, etc. are appropriately arranged, In particular, by configuring each element so that a portion of the optical path of the finder system is used in both directions, the space inside the camera is effectively utilized, resulting in an optical system that makes the entire camera thinner and smaller.

[Brief explanation of the drawing]

1 and 2 are schematic diagrams showing the optical path of the finder system of the photographing system in the optical system having the optical path bending means of the present invention, and FIG. 3 is a schematic diagram of the optical system of a conventional single-lens reflex camera. It is a diagram. In the figure, 11 is a photographing lens, 12 and 14 are rotating shafts, 13 is a photosensitive surface, Ml is a first reflecting mirror, M2 is a second reflecting mirror, M3 is a semi-transmissive mirror, L is a luminous flux, and Ll is a first reflecting mirror. , L2 is a second reflecting mirror, L3 is a third reflected light beam, 15 is an eye shutter, 16 is a film, 17 is a field lens, 18 is an imaging lens, 19 is a roof reflection surface, and 20 is an eyepiece lens. . Patent applicant: Canon Co., Ltd. Figure 3

Claims (1)

[Claims] (1) A first reflecting mirror placed behind the taking lens at approximately 45 degrees with respect to the optical axis of the taking lens reflects the light flux that has passed through the taking lens, and the first reflection is reflected by the first reflecting mirror. The light beam is reflected in a direction substantially perpendicular to a first plane formed by the optical axis of the photographing lens and the first reflected light beam by a second reflecting mirror arranged at approximately 45 degrees with respect to the first reflected light beam. , a photographing system configured to guide a second reflected light beam reflected by the second reflecting mirror onto a photosensitive surface, and a semi-transmissive mirror being positioned at the position of the second reflecting mirror by retracting the second reflecting mirror; , after reflecting the first reflected light beam from the first reflecting mirror by the semi-transmissive mirror in a direction parallel to the optical axis of the photographing lens and toward the object side;
A primary object image is formed in the vicinity of a field lens arranged at a position optically substantially equal to the imaging position of the photographic lens, and then, after passing through a roof reflection surface from the imaging lens, the original optical path is backlit; A finder system that forms a secondary object image of an erect image near the field lens again through the imaging lens, and observes the secondary object image with an eyepiece through the semi-transparent mirror. An optical system comprising an optical path bending means.