JPH01295245A - Optical system provided with optical path folding means - Google Patents

Abstract

PURPOSE:To thin and miniaturize an entire camera by performing the switching of a photographing system and a finder system by turning a 1st reflecting mirror centering around a specified axis and making the luminous flux of the finder system pass through one area in the rear of a 2nd reflecting mirror. CONSTITUTION:The 1st reflecting mirror M1 is arranged at nearly 45 deg. against the optical axis S1 of a photographic lens 11 so as to reflect luminous flux L from the photographic lens 11 in a specified direction. The 2nd reflecting mirror M2 is arranged at nearly 45 deg. against 1st reflected luminous flux L1. The finder system is so constituted that the 1st reflecting mirror M1 is turned centering around the axis perpendicular to a 1st plane to conduct the 1st reflected luminous flux L1 from the 1st reflecting mirror M1 to a 3rd reflecting mirror M3 arranged on the photographic lens 11 and conduct 3rd reflected luminous flux L3 reflected from the 3rd reflecting mirror M3 to an eyepiece lens. 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 43 is arranged at the rear on the optical axis of a photographing lens 41 to form a photographing system, as shown in FIG. are doing.

Further, the light beam passing through the photographing lens 41 is reflected upward of the camera body by a rotating mirror 42 disposed behind the photographing lens, thereby forming a finder image on the entire surface of the plate 44 toward the pin 1. The finder system is configured such that the finder image on the surface of the focusing plate 44 is observed as an erect normal image through a condenser lens 45 and a pentaprism 46 through an eyepiece lens 47.

In this way, in a conventional single-lens reflex camera, the finder light beam is reflected above the camera body by the rotating mirror 42,
A pentaprism placed above the photographic lens 41 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 size of the 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 make the entire camera thinner in the vertical direction.

(Problems to be Solved by the Invention) The present invention does not use the conventional pentaprism, but by appropriately arranging a plurality of reflecting mirrors as optical path bending means and a plurality of lenses for focusing or imaging. An object of the present invention is to provide an optical system having an optical path bending means, in which a photographing system and a finder system are efficiently housed as a whole in a thin space, and the whole camera is easily made thin and compact.

(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 substantially perpendicularly reflects the first plane formed by the optical axis of the photographic lens and the first reflected light beam, and the second reflected light beam reflected by the second reflecting mirror is directed onto a photosensitive surface. A photographing system configured to guide light, and rotating the first reflecting mirror around an axis perpendicular to the first plane to place a first reflected light beam from the first reflecting mirror on the photographing lens side. and a finder system configured to guide light to a third reflecting mirror, and guide a third reflected light beam reflected from the third reflecting mirror to an eyepiece.

(Example) FIG. 1 is a schematic view of the main parts showing the optical paths of a photographing system and a finder system of an optical system having an optical path bending means according to the present invention.

In the figure, 11 is a photographing lens, and 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 light beam from the photographic lens 11 in a predetermined direction. There is. Further, the first reflecting mirror M1 is configured to reflect the light beam on the optical axis of the photographing lens 11 and the first reflection mirror M1 of the light beam.
It is set to be rotatable about an axis 12 that is substantially perpendicular to the first plane formed by the reflected light beam L1.

M2 is a second reflecting mirror, which is arranged at approximately 45 degrees with respect to the first reflected light beam L1, and reflects the first reflected light beam L1 in a direction substantially perpendicular to the first plane as a second reflected light beam L2. The light is guided to a photosensitive surface 13 of a film, CCD, etc.

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

Next, a case will be described in which a finder system is constructed by rotating the first reflecting mirror M1 by a predetermined angle around the shaft 12. In this figure, the lenses constituting the finder system are omitted.

In the figure, the first reflecting mirror M1 is rotated to guide the first reflected light beam L1 to the third reflecting mirror M3 arranged on the photographing lens 11 side. Then, the third reflected light beam L3 reflected by the third reflecting mirror M3 in a direction parallel to the optical axis S1 of the photographic lens 11 is transferred to the second reflected light beam L3.
The light passes through the non-reflective side of the back surface of the reflecting mirror M2 and is guided to an eyepiece (not shown).

In this embodiment, the first reflected light beam L1 and the third reflected light beam L3 exist on the same plane. Incidentally, when a finder system is used, a shutter (not shown) is provided as a light shielding material on the photosensitive surface 13.

In this example, the first. Second. Each of the third mirrors constitutes a part of the optical path bender stage.

FIG. 2 is a schematic diagram of an embodiment in which condensing and imaging lenses are arranged in an optical path that seems to require the imaging relationship of the finder system shown in FIG. 1. In the figure, after the light beam from the photographing lens 11 is reflected by the first reflecting mirror M1, a primary object image 2b of the object 2a is formed near the first field lens 21. Next, the first object image 2b formed near the first field lens 21 is transferred to the imaging lens 22.
the second field lens 2 via the third reflecting mirror M3.
A second object image 2c, which is an erect image, is formed in the vicinity of 3. The secondary object image 2c is then observed through an eyepiece lens 24, which constitutes a finder system.

In this embodiment, in order to facilitate observation of the finder image, when configuring the finder system, the first reflecting mirror M1 and the third reflecting mirror M3 are parallel to each other, that is, the optical axis s1 of the photographing lens 11 and the finder It is configured to be parallel to the optical axis S2 of the system.

In this embodiment, the optical axis s1 and the optical axis s2 may not be parallel to each other, but may be displaced depending on the purpose.

In this embodiment, in order to shorten the optical path length of the entire finder system and downsize the lens system, a lens with positive refractive power is placed in the optical path where the first reflecting mirror M1 and the primary object image are formed. That's good.

FIG. 3(A) is a schematic diagram showing the state of the light flux near the second reflecting mirror M2 when looking in the direction of the third reflecting mirror M3 from the eyepiece 24 side in the present invention.

In particular, in the same figure, the first image taken by the imaging system. Second reflected light flux Ll, L
2 and the third reflected light beam L3 by the finder system.

In the figure, 31 is the third reflecting mirror M by the finder system.
In this example, the light beam 31 is the reflected light beam from the second
Each element is set so as to pass through an area behind the reflecting mirror M2. This makes effective use of the space inside the camera and facilitates miniaturization of the entire camera.

FIG. 3(B) is a schematic diagram showing the state of the light flux in an embodiment in which the inclination of the third reflecting mirror M3 in FIG. 1 is changed to displace the light flux 31 of the finder system above the second reflecting mirror M2. . In the figure, since the optical axis S1 of the photographic lens and the optical axis s2 of the finder system are no longer parallel, it becomes difficult to aim the finder image, but it becomes easier to downsize the entire camera.

In this embodiment, the position and inclination of each element may be configured so that the light beam 31 shown in FIG. 3(B) passes through the space formed by the second reflecting mirror M2 and the photosensitive surface 13.

In the present invention, if reverse incident light from the eyepiece side of the finder system reaches the photosensitive surface 13 during photographing, a member for blocking the reverse incident light, such as an eyepiece shutter, is attached to the viewfinder when switching during photographing. It is best to install it in a part of the system, for example near the eyepiece.

(Effects of the Invention) According to the present invention, switching between the photographing system and the finder system is performed by rotating the first reflecting mirror around a predetermined axis. By allowing the light beam from the finder system to pass through a region at the back and making effective use of the space inside the camera, we have achieved a thin and compact optical system that allows the entire camera to be thin and compact.

In particular, by appropriately setting the plurality of reflecting mirrors and lenses as described above, it is easy to reduce the thickness of the entire camera.

[Brief explanation of the drawing]

FIG. 1 is a schematic view of the main parts showing the optical path of a photographing system and a finder system according to an embodiment of the present invention, and FIG. 2 is a plan view of the main parts of the finder system of FIG. FIGS. 3(8) and 3(B) are explanatory diagrams of a portion of FIG. 1, and FIG. 4 is a schematic diagram of the optical system of a conventional single-lens reflex camera. In the figure, 11 is a photographing lens, 12 is a rotation axis, 13 is a photosensitive surface, Ml is a first reflecting mirror, M2 is a second reflecting mirror, M3 is a third reflecting mirror, L is a luminous flux, Ll is a first reflected luminous flux, L2 is a second reflected light beam, L3 is a third reflected light beam, 21 is a first field lens, 23 is a second field lens, 22 is an imaging lens,
24 is an eyepiece lens, and 31 is a finder light beam. Figure 3 (A) (B)

Claims (3)

[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. , an imaging system configured to guide a second reflected light beam reflected by the second reflecting mirror onto a photosensitive surface; and a photographing system configured to rotate the first reflecting mirror about an axis perpendicular to the first plane. The first reflected light beam from the first reflecting mirror is guided to a third reflecting mirror disposed on the photographing lens side, and the third reflected light beam reflected from the third reflecting mirror is guided to an eyepiece lens. An optical system having an optical path bending means, characterized in that it has a finder system. (2) An optical system having an optical path bending means according to claim 1, wherein the optical axis of the photographing lens and the third reflected light beam are parallel to each other. (3) Each element is set so that the third reflected light beam is parallel to the optical axis of the photographing lens, and the third reflected light beam passes through the non-reflective surface side of the second reflecting mirror. An optical system having an optical path bending means according to claim 1.