JP3128125B2 - Imaging optical system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an imaging optical system used for a silver halide photographic camera, a still video camera, a video movie camera, and the like.

[Conventional technology]

In the case where the camera is to be reduced in size, particularly in the front-rear direction, for example, a method of reducing the telephoto ratio of an imaging optical system as described in JP-A-61-67814 or described in JP-A-64-28610 A method to bend the optical axis using a mirror as shown in the figure or a method to flatten the front side of the camera when not in use and eliminate the protrusion by using a retractable mechanism as described in "Photo Industry Vol. 47 No.5 P75-80" There is.

[Problems to be solved by the invention]

However, with the method of reducing the telephoto ratio, it becomes difficult to reduce the telephoto ratio toward the wide-angle side, the number of lenses increases to correct aberrations, and aspherical surfaces must be used frequently. However, there is a disadvantage that cost and quality are disadvantageous. Further, there is a disadvantage that it is difficult to maintain the imaging performance at a high level.

Also, in the method of bending the optical axis using a mirror, if the mirror is too close to the imaging surface or if the distance between the two optical axes is too close, it will not be possible to block harmful light flux, so it is limited to miniaturization. There is a disadvantage that there is. Further, since the optical path length increases as the mirror space increases, there is a disadvantage that it is difficult to form a mirror having a short focal length.

Further, the method using the collapsible mechanism has a disadvantage that the mechanical mechanism is complicated. Further, there is a disadvantage that eccentricity occurs due to the movement of the optical system, which is disadvantageous in quality. Furthermore,
Since the lens system protrudes from the body during photographing, there is a disadvantage that it is difficult to configure the camera in a waterproof structure.

The present invention has been made in view of the above-described problems, and enables the camera to be significantly thinned in the front-rear direction, while maintaining high performance and quality, simplifying the structure of the camera, and completely eliminating harmful light. It is an object of the present invention to provide an imaging optical system that can shield light, easily configure a camera in a waterproof structure, and reduce manufacturing costs.

[Means and actions for solving the problem]

An imaging optical system according to the present invention includes: an objective optical system; an entrance surface, a reflection exit surface, and a reflection surface; and an imaging light beam exiting the objective optical system is received by the entrance surface, and the reflection exit surface reflects the reflection surface. A prism which is totally reflected in the direction of, further reflected by the reflecting surface, and then emitted from the reflecting exit surface, a region of the objective optical system being closer to the object side than the most object side surface, an entrance surface of the prism, A light-shielding film is provided in at least one of the area outside the effective light beam passing area outside the prism near the incident surface, the reflection exit surface of the prism, and the area outside the prism near the reflection exit surface. It is characterized by that.

That is, as shown in FIG. 1, for example, the imaging optical system according to the present invention has an objective optical system 1, an entrance surface 2a, a reflection exit surface 2b, and a reflection surface 2c, and a light beam emitted from the objective optical system 1. And a prism 2 that totally reflects in the direction of the reflecting surface 2c by the reflecting and emitting surface 2b received by the incident surface 2a, and further emits the reflected light from the reflecting and emitting surface 2b after reflection. It is designed to be imaged. Also, incident surface 2a
Light-shielding films 4 and 5 are provided on portions of the reflection exit surface 2b outside the effective light beam passage areas, respectively.

According to the above configuration, since the optical axis is bent in the prism 2, the thickness of the camera in the front-rear direction can be significantly reduced.

The harmful light flux passing through the prism 2 generally has a pattern as shown in FIG. 2 (A) or (B).
Of these, light shielding is established when light rays are absorbed by the light shielding film 5 or travel outside the imaging surface 3. Light shielding film 4 formed on the incident surface 2a side of prism 2
Cuts off harmful light incident on the imaging surface 3 while repeating internal reflection within the prism 2 by shielding as much as possible extra light beams other than the imaging light flux incident on the prism 2. The light-shielding film 5 formed on the reflection exit surface 2b side
Harmful light, such as a light ray, that exits the reflection exit surface 2b is cut. In this way, the harmful light emitted into the space passing through the imaging light flux behind the reflection emission surface 2b can be always a light ray that travels outside the imaging surface 3. Thus, harmful light can be completely blocked. In order to cut off harmful light that cannot enter the prism 2 due to being unable to shield light with the light shielding film 4 on the incident surface 2a side, a frame in the objective optical system 1 is used, or a light shielding member is provided on the object side of the imaging optical system. Should be arranged. If the light-shielding effect is sufficiently exerted, the most object-side surface of the objective optical system 1, the entrance surface 2a of the prism 2, the region outside the prism 2 near the entrance surface 2a, the reflection exit surface 2b of the prism 2, It is only necessary to provide a light-shielding film outside the prism 2 at at least one of the regions near the reflection / emission surface 2b.

Further, according to the above configuration, since the number of optical elements is small and the optical system is not moved, the performance and quality can be maintained at a high level, and the structure of the camera can be simplified and the manufacturing can be simplified. Costs are low. Further, since the collapsible mechanism is not used, it is easy to configure the camera with a waterproof structure.

〔Example〕

Hereinafter, the present invention will be described in detail based on illustrated embodiments.

FIG. 3 shows an embodiment of an image pickup optical system according to the present invention. In this embodiment, in addition to the configuration shown in FIG.
A cover glass 6 is arranged on the front side of the objective optical system 1, and a light shielding film 7 is provided on a portion of the object side surface outside the effective light beam passage area. The shapes of the light shielding films 7, 4, and 5 are as shown in FIGS. 4 (A), (B) and (C), respectively.
The data of this embodiment is as follows.

Surface number rdn ν 1 ∞1 1.51633 64.1 2 ∞3.3 13 12.214 4.715 1.79952 42.2 4 14.961 1.1 15 -29.683 1 1.5927 35.3 6 10.500 0.342 17 13.803 2.3 1.7725 49.6 8 -27.635 2.645 1.9 9 ∞29.024 1.516334.1 ∞f = 35.6, F _No. = 3.64, 2ω = 62.5 ゜ where r is the radius of curvature of the lens surface, d is the distance between the lens surfaces, n is the refractive index of the lens, ν is the Abbe number of the lens, and f is the entire system. focal length of, F _No. is effective F-number of the entire system, omega denotes a half angle of view.

 The dimension data of the prism 2 is as follows.

 ▲ = 16.757 ∠PQR = 90 ゜ ▲ ▼ = 33.514 ∠QRP = 30 ゜ ▲ ▼ = 29.024 ∠RPQ = 60 ゜ The aberration states of the present embodiment are as shown in FIG.

 The dimensional data of the films 7, 4, and 5 are as follows.

The light-shielding film 7 on the object side surface of the cover glass 6 D = 17.96 H = 12,26 The light-shielding film 4 on the entrance surface 2a of the prism 2 D = 8.88 H = 8.06 The light-shielding film 5 on the reflection exit surface 2b of the prism 2 W = 28.15 H = 19.6 FIG. 6 shows the light shielding state by these light shielding films. This shows the passing state and the light blocking state of the imaging luminous flux by using the sine of the incident height h and the ray inclination u as the vertical axis and the horizontal axis, respectively, of the light beam that has passed through the entrance surface 2a of the prism 2 in the meridional section. A substantially parallelogram portion is a region of the light beam incident on the prism 2, and a light beam other than the effective imaging light flux area (a white portion surrounded by a solid line) is cut by a light shielding material or is out of the imaging surface. You can see that it goes to. In addition, reflection surface 2c
Is provided with a reflective coat, and the range of the reflective coat is determined so as to coincide with the effective range of the imaging light flux.

〔The invention's effect〕

As described above, the imaging optical system according to the present invention can greatly reduce the thickness of the camera in the front-rear direction, can maintain high performance and quality, can simplify the structure of the camera, and can reduce harmful light. It has a practically important advantage that light can be completely shielded, the camera can be easily configured in a waterproof structure, and the manufacturing cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of an image pickup optical system according to the present invention, FIGS. 2A and 2B are diagrams showing the principle of light shielding in the image pickup optical system, FIG. FIG. 4 is a view showing the shape of each light-shielding film of the above embodiment, FIG. 5 is a view showing an aberration state of the above-mentioned embodiment, and FIG. 6 is a view showing a light-shielding state of the above-mentioned embodiment. 1 ... objective optical system, 2 ... prism, 2a ... entrance surface, 2b
…… Reflection exit surface, 2c …… Reflection surface, 3 …… Imaging surface, 4,5,7
…… Light shielding film, 6 …… Cover glass.

Claims (1)

(57) [Claims] An objective optical system, an incident surface, a reflection exit surface, and a reflection surface, wherein an imaging light beam emitted from the objective optical system is received by the incident surface and is directed toward the reflection surface by the reflection exit surface. An imaging optical system, comprising: a prism that totally reflects the light, reflects the light on the reflection surface, and then emits the light from the reflection emission surface. The light incidence film and the reflection emission surface are provided with a light shielding film that cuts harmful light.