JPS6325612A - Photographing system having refractive force filter - Google Patents

Abstract

PURPOSE:To reduce the size of the titled photographing system and allowing the system to have excellent driving efficiency and display prescribed filter effects by attachably/detachably arranging a refractive force filter having its refractive force on one surface between the photographing lens and an image forming surface. CONSTITUTION:The refractive force filter 2 is arranged on the back of the photographing lens 1 to form the image of a light beam 4 on the image forming surface. The filter 2 has the prescribed filter effects such as color change, color temperature change and softening effect and has the positive refractive power on one surface. Although a shear may be generated on an image formation point by the thickness of an usual filter made of a parallel plane, the refractive power filter suppresses the generation of a shear on the image formation surface before and after loading the filter and does not exerts influence upon the optical system because of the extremely small refractive power. Thereby, the small-sized photographing system having excellent driving efficiency and capable of displaying the prescribed filter effects efficiently can be obtained.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a photographing system having a refractive power filter suitable for photographic cameras, video cameras, etc. Alternatively, when the photographic lens is composed of a plurality of lens systems, the present invention relates to a photographic system having a refractive power filter that is removably attached to the lens systems to obtain a desired filter effect.

(Prior Art) Conventionally, in many cameras such as photo cameras and video cameras, various filters such as color filters, ND filters, and soft focus filters are attached to a part of the photographic lens to achieve the desired filter effect. We are taking pictures. In this case, a predetermined filter is attached to a part of the photographic lens each time, or an unnecessary filter is removed from the photographic lens and a desired filter is attached to take the photograph. For this reason, there is a drawback that functionality is poor and quick photographing is difficult.

As a method for solving this drawback, the present applicant previously proposed in Japanese Utility Model Application Laid-Open No. 58-15LI1 a camera having a built-in filter. As shown in FIG. 4, the publication proposes that one or more filters 42 are provided between a protective cover 41 that is movably provided in front of the photographic lens 1 and the front surface of the photographic lens to enable highly mobile photographing. Is going. In the same figure, 3
is an imaging plane, and 43 is a camera body.

However, in this publication, since the filter is built in so that it can be selectively attached to the front of the photographic lens, it is necessary to provide a space in a part of the camera for the filter to retreat from the photographic lens, as shown by the broken line in Fig. 4, for example. There was a tendency for the camera body to become larger only in this area.

Furthermore, since the filter is mounted in front of the photographic lens, the filter diameter tends to increase.

(Problems to be Solved by the Invention) The present invention reduces the size of a camera by removably attaching a refractive power filter having a filter effect and a predetermined refractive power to the image side of the photographic lens or to the photographic lens system. It is an object of the present invention to provide an imaging system having a refractive power filter that has excellent mobility and is capable of producing wL shadows with a predetermined filter effect.

(Means for solving the problem) A refractive power filter having refractive power on at least one surface is removably attached between the taking lens and the imaging surface or in a part of the lens system of the taking lens. be.

Other features of the invention are described in the Examples.

(Embodiment) FIG. 1(A) is a schematic diagram of an optical system according to an embodiment of the present invention. In the figure, 1 is a photographing lens, 2 is a refractive power filter that has predetermined filter effects such as color change, color part change, and soft effect, and has positive refractive power on at least one surface, and 3 is a refractive power filter. The image plane, 4, is an HFi shadow light flux.

Conventionally, filters such as color filters and soft focus filters attached to a part of a TI shadow lens are made of parallel plane plates and have no refractive power. There is no optical problem when attaching this filter to the front of the photographic lens, but when attaching it to a long-focus photographic lens such as a telephoto lens, the filter diameter increases, making the entire photographic lens larger. There is a tendency to Generally, in order to reduce the size of a photographic lens, a filter may be mounted, for example, at a position where the Wit light flux between the photographic lens and the imaging plane converges. However, as shown in FIG. 1(B), if a filter 5 made of a parallel plane plate is attached between the photographing lens 1 and the image forming surface 3, the image forming point of the V & shadow light beam 4 will be the same as that when no filter is attached. The position shifts from point 11 to another point 12. The amount of deviation of the image plane at this time is proportional to the thickness of the attached filter. For this reason, thick filters could not be placed between the photographic lens and the imaging plane because they would degrade optical performance.

In contrast, in this embodiment, as shown in FIG. 1(A), at least one surface of the filter 2 is provided with a spherical or aspherical surface in consideration of the filter thickness in order to correct the deviation of the imaging plane when the filter is attached. A refractive power filter having a refractive surface with positive refractive power consisting of the above is attached, and this corrects the amount of deviation of the image forming plane when the filter is attached between the photographing lens and the image forming plane, and the difference between before and after attaching the filter is corrected. Shooting with luminous flux 4
are formed on the same imaging plane 3.

FIGS. 2(A) and 2(B) are schematic diagrams of an optical system according to another embodiment of the present invention. In this embodiment, the photographing lens is configured to have a main lens system 21 and an auxiliary lens system 22 with positive or negative refractive power detachably arranged on the image plane side of the main lens system 21, and having two focal lengths. There is.

When attaching the auxiliary lens system 22, the main lens system 21 is extended toward the object side. As shown in FIG. 2B, a refractive power filter 2 having a positive refractive power is removably disposed between the main lens system 21 and the auxiliary lens system 22. Note that the refractive power filter 2 may be arranged between the auxiliary lens system 22 and the image forming surface 3.

As a result, regardless of whether or not the auxiliary lens system 22 is attached, the image forming position of the image forming surface 3 behind the mounting surface of the refractive power filter 2 is maintained at the same position.

In addition, the same figure (C) shows when the image forming point 20 is shifted to the point 24 when the filter 23 having no refractive power is placed between the main lens system 21 and the auxiliary lens system 22. It is an explanatory diagram.

As described above, in this embodiment, by using a refractive power filter having a positive refractive power as a part of the photographic lens system, the deviation of the imaging plane is effectively corrected.

3(A) and 3(B), similarly to the embodiment shown in FIG. 2, the photographing lens is composed of the main lens system 21 and the auxiliary lens system 22, and the refractive power filter 2 is composed of the main lens system 21 and the auxiliary lens. This is a case where it is detachably attached to the system 22.

In the figure, 30 is a film surface, and 31 is a camera body.

In this embodiment, each element is spatially configured so that the refractive power filter 2 is not used when photographing only with the main lens system 21, and the refractive power filter is used only when the auxiliary lens system 22 is attached. We are trying to make it smaller.

In other words, as shown in FIG.
1 only 19 When in the shadow, the refractive power filter 2 is arranged so that it cannot be attached to the image plane side. And the same figure (B)
As shown in the figure, when the main lens system 21 is extended toward the object side, the auxiliary lens system 22 and the refractive power filter 2 can be placed in that space on the image plane side of the main lens system 21, thereby increasing the space usage efficiency. The aim is to make the entire camera more compact.

As described above, in this embodiment, the auxiliary lens system 22 is installed so that a filter effect such as soft focus can be obtained only during telephoto shooting, for example.

Note that the refractive power of the refractive power filter according to the present invention is generally extremely small. For this reason, even if a refractive power filter is attached, it hardly affects the optical performance of the photographic lens, making it possible to take photographs with a predetermined filter effect.

In each of the above embodiments, only one refractive power filter is used, but two or more refractive power filters may be built into the camera.

(Effects of the Invention) According to the present invention, by removably attaching a refractive power filter having a predetermined refractive power to a predetermined position of a photographic lens, the camera is miniaturized and has excellent mobility. It has a refractive power filter that allows you to take pictures with excellent filter effects! A shadow system can be achieved.

[Brief explanation of the drawing]

Figure 1 (^) is a schematic diagram of an optical system according to an embodiment of the present invention, Figure 1 (B) is a schematic diagram of a conventional optical system, Figure 2 (A), (
11), FIGS. 3(A) and 3(B) are schematic diagrams of an optical system according to another embodiment of the present invention, and FIGS. 2(C) and 4 are explanatory diagrams of conventional optical systems, respectively. be. In the figure, 1 is an S shadow lens, 2 is a refractive power filter, 3 is an imaging plane, 4 is a shooting light beam, 5, 23.42 is a filter, 21
2 is a main lens system, and 22 is an auxiliary lens system. Patent applicant: Canon Co., Ltd. 1 Figure 4: Rabbit 3

Claims (2)

[Claims] (1) A refractive power filter characterized in that a refractive power filter having refractive power on at least one surface is removably attached between a photographic lens and an image forming surface or in a part of a lens system of a photographic lens. Photography system. (2) The photographing lens has a main lens system and a removable auxiliary lens system on the imaging plane side of the main lens system for changing the focal length of the entire system, and the refractive power filter is A refractive power filter according to claim 1, comprising a positive filter having a refractive power, the positive filter being detachably attached between the main lens system and the auxiliary lens system. Photography system.