JPS62100721A - wide converter lens - Google Patents

Abstract

PURPOSE:To obtain a wide converter lens appropriate for multi-purpose use by constituting two lens groups having negative and positive refractive power values respectively of two structures to be separated each other. CONSTITUTION:Holding rings 3, 5 are attachable/detachably constituted. When the lens system is to be used as a wide converter lens, the 1st and 2nd lens groups 1, 2 are coupled with each other and both the lens groups are set up in front of a photographing system. When the lens system is used as a close-up lens, the 1st lens group 1 is separated from the 2nd lens group and only the 2nd lens group 2 having positive refractive power is set up in front of the photographing system. The wide converter lens is constituted of two lens groups having negative and positive refractive power values respectively. Consequently, a using method corresponding to a photographing purpose can be obtained.

Description

[Detailed Description of the Invention] (Industrial Field of Application) The present invention is directed to photography! Concerning the wide converter lens that can be attached to the front of lenses 2 and 6 to change the focal length of the entire system, this wide converter lens can be used for multiple purposes by being configured so that it can be separated into two lens groups. It is related to.

(Prior art) Conventionally, so-called wide converter lenses have been used, which are attached to the object side of a photographing system and change the focal length of the entire system to, for example, the wide-angle side while maintaining the focal plane of the entire system at a constant position. Various proposals have been made.

In general, many wide converter lenses are composed of two lens groups having negative and positive refractive powers in order from the object side. The lens barrel is held within an integral lens barrel, and is attached to a part of the lens barrel facing the photographing system with a screw, bayonet, or the like.

In this way, conventional wide converter lenses are built into an integrated lens barrel, so they only have the function of shifting the focal length range of the photographing system to the wide-angle side, for example, for close-up photography. had to prepare a new close-up lens.

As an example that can be used for this purpose, it is proposed that the wide converter lens be used as a so-called teleconverter lens, in which the direction of the wide converter lens is reversed and the focal length of the entire camera system is shifted to the telephoto side. has been done. However, this method has problems such as a lot of vignetting of the light beam due to insufficient lens effective diameter, and it is very difficult to maintain good optical performance.

(Problems to be Solved by the Invention) The present invention provides a wide converter lens that is suitable for multi-purpose use such that it can be used for purposes other than its function as a wide converter lens, such as a close-up lens or a wide attachment lens. The purpose is to provide a wide converter lens with a wide configuration.

(Means for solving the problem) A wide converter lens that is attached to the object side of the photographing system and changes the focal length of the entire system, and the wide converter lens is sequentially installed from the object side with a negative refractive power. It is composed of two lens groups, a lens group and a lens group with positive refractive power, and is configured so that the members holding the two lens groups can be separated. Particularly, in the present invention, the separation attachment part on the side of the lens group having negative refractive power is configured to have the same shape as the attachment part of the wide converter lens to the imaging system, for convenience in attachment.

Other features of the invention are described in the Examples.

(Example) FIG. 1 is a sectional view of a wide converter lens according to an example of the present invention. In the figure, 1 is a negative lens group with a negative refractive power, 2 is a second lens group with a positive refractive power, 3 is a retaining ring for the first lens group, 4 is a holding ring for the first lens group, and 5 is a second lens group. The holding ring 6 of the lens group 2 is a holding ring of the second lens n2.

In this embodiment, the retaining ring 3 and the retaining ring 5 are configured to be detachable,
The two are connected by screws, bayonet, etc. The retaining ring 5 is provided with a mounting portion, such as a screw or bayonet, for mounting on the imaging system. A mounting portion is also provided in the holding portion 3 in exactly the same manner.

In this embodiment, when used as a wide converter lens, the first lens group 1 and the second lens group are connected and both are mounted in front of the photographing system. When used as a close-up lens, the first lens group and the second lens group are separated, and only the second lens group 2 with positive refractive power is mounted in front of the #&shadow system.

In this way, in this embodiment, the retaining ring 3 and the retaining ring 5 can be separated, and the wide converter lens is configured with two lens groups with negative and positive refractive powers, making it possible to use it according to the purpose of photography. It is said that

Further, in this embodiment, if the photographing system has a macro mechanism, this macro mechanism can be used and the lens group 1 can be mounted in front of the photographing system as disclosed in Japanese Patent Publication No. 58-8481. It can be used as a wide attachment for use as an ultra-wide-angle lens.

In this embodiment, the first. Although the second lens group has been shown to be composed of one lens, it may also be composed of two or more lenses, and aberration correction can be performed satisfactorily.

In addition, in this embodiment, the wide converter lens may be configured so that three or more lens groups including lenses with positive and negative refractive powers can be separated from each other, and the mounting portions of each lens group are made common. .

(Effects of the Invention) According to the present invention, by configuring two lens groups with negative and positive refractive powers in a separable two-body structure, it not only functions as a wide converter lens, but also functions as a close-up lens and wide attachment lens. A wide converter lens can be achieved which can also be used as a lens and can be used as a versatile system accessory.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a wide converter lens according to an embodiment of the present invention. In the figure, 1 is a lens group with negative refractive power, 2 is a second lens group with positive refractive power, 3.5 is a holding ring, and 4.6 is a holding ring.

Claims (2)

[Claims] (1) A wide converter lens that is attached to the object side of the photographing system and changes the focal length of the entire system, and the wide converter lens is connected to a lens group with negative refractive power and a lens with positive refractive power in order from the object side. What is claimed is: 1. A wide converter lens comprising two lens groups, and a member holding the two lens groups is configured to be separable. (2) The wide converter lens according to claim 1, wherein the separate attachment portion on the side of the lens group having negative refractive power is shaped so that it can be attached to the imaging system.