JPH01295242A - Optical system provided with optical path folding means - Google Patents

Abstract

PURPOSE:To effectively utilize space in a camera and to thin and miniaturize the entire camera by turning a 1st reflecting mirror centering around a specified axis so that the switching of a photographing system and a finder system can be performed 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 the luminous flux L from the photographic lens 11 in a specified direction. The 2nd reflecting mirror M2 is arranged at nearly 45 deg. against the 1st reflected luminous flux L1. The finder system is so constituted that the 1st reflecting mirror M1 is turned centering around the axis titled at a specified angle against 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 side and conduct 3rd reflected luminous flux L3 reflected from the 3rd reflecting mirror M3 to an eyepiece lens. Thus, the photographing system and the finder system can be effectively housed as a whole in the space whose thickness is thin and 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., in which the thickness of the camera in the vertical direction is reduced. 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 flux that has passed through the photographic lens 41 is reflected upward of the camera body by a rotating mirror 42 placed behind the photographic lens to form a finder image on the surface of the focusing plate 44. The finder system is configured such that the finder image on the surface of the focusing plate 44 is observed through the condenser lens 45 and the pentaprism 46 as an erect normal image with the eyepiece lens 47.

In this way, in a conventional single-lens reflex camera, the viewfinder light flux 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, when the pentaprism, which is part of the components of the finder system, protrudes above the camera body, and a photographic lens is attached to the camera body, the overall camera tends to become relatively large.

In particular, in the configuration using a conventional pentaprism, a portion of the camera has a protruding shape, making it extremely difficult to make the entire camera thin 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. To provide an optical system having an optical path bending means, which allows a photographing system and a finder system to be efficiently housed as a whole in a thin space, thereby easily making the entire camera 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 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. A photographing system configured to guide light, and a first reflected light beam from the first reflecting mirror by rotating the first reflecting mirror around an axis tilted at a certain angle from an axis perpendicular to the first plane. The light is guided to a third reflecting mirror placed on the photographing lens side, and the third reflected from the third reflecting mirror is
It also has a finder system configured to guide the reflected light flux to the 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 inclined at a certain angle from an axis 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 an axis 12 that is inclined at a predetermined angle from an axis perpendicular to the first plane. Incidentally, in the figure, each lens constituting the finder system is omitted.

In the figure, the first reflecting mirror M1 is rotated by a certain angle about the support 12, and the first reflected light beam L1 is guided to the third reflecting mirror M3 arranged on the photographing lens 11 side. The third reflected light beam L3 reflected by the third reflecting mirror M3 passes through the non-reflecting surface side of the back surface of the second reflecting mirror M2 and is guided to an eyepiece (not shown).

In this embodiment, the luminous flux L, the first reflected luminous flux L1, and the third reflected luminous flux L3 exist on the same plane that is inclined at a certain angle to the first plane. Incidentally, when a finder system is used, a shutter (not shown) as a light shielding material is provided on the photosensitive surface 13.

In this example, the first. Second. Each of the third reflecting mirrors constitutes a part of the optical path bending means.

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 2. Next, the primary 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 24, which constitutes a finder system.

In this embodiment, in order to facilitate observation of the finder image, the finder system is configured such that the first reflecting mirror M1 and the third reflecting mirror M3 are parallel to each other.

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. It's good.

FIG. 3 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.
Each element is arranged so that the third reflected light flux L3, which corresponds to the center of the light flux 31 in this embodiment, passes through an area above the first plane behind the second reflecting mirror M2. It is set.

This makes effective use of the space inside the camera and facilitates miniaturization of the entire camera.

In this embodiment, the light beam 31 shown in FIG.
The position and inclination of each element may be configured so that it passes through the space formed by the photosensitive surface 2 and the photosensitive surface 13.

In addition, 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 provided when switching during photographing, such as an eyepiece shutter. It is preferable to provide it in a part of the inter 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, and in particular, when configuring the finder system, the camera is behind the second reflecting mirror. By allowing the light beam from the finder system to pass through one region of the camera, and making effective use of the space inside the camera, an optical system has been achieved that allows the camera to be thin and compact as a whole.

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 finer system according to an embodiment of the present invention, and FIG. 2 is a plan view of the main parts of the finer system of FIG. 1. FIG. 3 is an explanatory diagram 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. Patent applicant: Canon Corporation Shima 3 Figures 4 Figures

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 flux reflected by the second reflecting mirror onto a photosensitive surface; and an imaging system configured to guide the second reflected light beam reflected by the second reflecting mirror onto a photosensitive surface; The first reflected light beam from the first reflecting mirror is guided to a third reflecting mirror disposed on the photographing lens side by rotating around the center, and the third reflected light beam reflected from the third reflecting mirror is directed to the eyepiece lens. 1. An optical system having an optical path bending means, comprising a finder system configured to guide light. (2) The optical system having an optical path bending means according to claim 1, wherein when forming the finder system, the first reflecting mirror and the third reflecting mirror are parallel to each other. (3) An optical system having an optical path bending means according to claim 1, wherein each element is set so that the third reflected light beam passes through a non-reflecting surface side of the second reflecting mirror. .