JPS62177512A - Switching type variable power optical system - Google Patents

Abstract

PURPOSE:To obtain a switching type variable power optical system with a simple constitution by selecting either one of the 1st photographing system and the 2nd photographing system reflecting a light beam radiated from a subject by the 2nd reflector arranged near the 1st photographing system and guiding the reflected light to the 2nd image formation surface on the approximately same plane as the 1st image formation surface. CONSTITUTION:A light beam projected from the object is guided to the 1st image formation surface 4 through a main lens system 1 and the 1st auxiliary lens system 2 to constitute the 1st photographing system, e.g. a photographing system with a short focal distance. Then, the 2nd auxiliary lens system 5 and the 1st reflector 6 are moved to a position shown by a dotted line on the optical axis on the back of the main lens system 1. The light beam from the object is reflected by the 1st reflector 6 in a direction, the rectangular direction, different from then optical axis 3 of the 1st photographing system, through the main lens system 1 and the 2nd auxiliary lens system 5, reflected by the 2nd fixed reflector 8 and led to the 2nd image formation surface 9 to constitute the 2nd photographing system, e.g. a photographing system with a long focal distance. Thus, switching from the 1st photographing system to the 2nd photographing system and its reverse switching can be easily and rapidly executed by loading/unloading both the 2nd auxiliary lens 5 and the 1st reflector 6.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a switching type variable magnification optical system suitable for photographic cameras, video cameras, etc.
The auxiliary lens system is removably placed on the image plane side of the main lens system, and the focal length of the entire system is changed, making it possible to easily obtain relatively high variable magnification and high-performance optical performance. This invention relates to a compact switching type variable magnification optical system.

(Prior Art) Zoom lenses and varifocal lenses have conventionally been used as photographing systems with variable focal lengths.

In addition, some lens groups for the photography system are removably attached.
There is a switching type variable magnification optical system configured to allow selection of two imaging methods.

In particular, the so-called converter type, in which a new auxiliary optical system is attached to the front or rear of the main optical system to change the focal length of the entire system, has a simple configuration and can easily change the focal length, making it suitable for photographic cameras. , is often used in the left camera for Sv. Among these, the so-called front converter type, in which an auxiliary optical system is mounted in front of the main optical system, tends to increase the lens diameter of the auxiliary optical system, making the entire lens system larger.

The so-called rear converter type, in which the auxiliary optical system is attached to the rear of the main optical system, has a smaller lens diameter than the front converter type, but it is difficult to correct aberrations, necessitates an increase in the number of lenses, and the overall lens length is longer. There was a tendency to Furthermore, these single-converter systems have drawbacks such as a necessary auxiliary optical system must be attached each time, resulting in poor mobility in photographing and difficulty in rapid photographing.

On the other hand, in Japanese Patent Publication No. 5B-38778, two lens systems, a standard lens and a telephoto lens, are placed side by side facing the subject, and one lens system is controlled by using a movable reflector built into the camera body. We are proposing a small switching type variable magnification optical system that can be used selectively. However, this variable magnification optical system has a drawback in that since the focal lengths of the two lens systems are different, the amount of extension of the lens systems relative to the object distance is different.

For example, when this is applied to an autofocus camera, the amount of extension of each lens system must be changed between the standard state and the telephoto state, which tends to complicate the internal mechanism of the camera.

(Problems to be Solved by the Invention) The present invention maintains the amount of extension of one lens system during focusing regardless of which of the two imaging systems, the first and second imaging systems having different focal lengths, is used. It is an object of the present invention to provide a switching type variable magnification optical system which has a simple configuration and has a small number of lenses overall.

(Means for solving the problem) A first lens system in which a light beam from an object is guided to a first imaging plane by passing through a main lens system having a positive refractive power and a first auxiliary lens system having a negative refractive power in order. A second auxiliary lens system having a negative refractive power and a first reflecting mirror are both removably arranged on the rear optical axis of the first imaging system and the main lens system, and the light flux from the subject is directed between the main lens system and the first reflecting mirror. After passing through two auxiliary lens systems in order and being reflected by the first reflecting mirror in a direction different from the optical axis of the first imaging system,
One of the second imaging systems is reflected by a second reflecting mirror disposed near the first imaging system and guided to a second imaging plane substantially coplanar with the first imaging system. It is configured to be selectable.

Other features of the invention are described in the Examples.

(Example) FIG. 1 is a schematic diagram of a switching type variable magnification optical system of the present invention.

In the figure, 1 is a main lens system with positive refractive power, 2 is a first auxiliary lens system with negative refractive power, and 4 is a first imaging plane. It makes up the shooting system.

A second auxiliary lens system 5 having a negative refractive power is removably installed on the rear optical axis of the main lens system 1, which is indicated by a dotted line in the figure. Reference numeral 6 denotes a first reflecting mirror that moves to the position shown by the dotted line in cooperation with the movement of the second auxiliary lens system 5 about the rotation axis 61.

8 is a fixed second reflecting mirror, 9 is a second imaging plane, and first imaging plane 4
It is placed approximately on the same plane as the IO is a light shielding plate that prevents stray light from entering other imaging systems.

In this embodiment, the light flux from the subject passes through the main lens system 1 and the first auxiliary lens system 2, and then is guided to the first imaging plane 4 to form a first imaging system, for example, a short focal length imaging system. are doing. FIG. 2 is a schematic diagram of the optical system at this time.

Next, the second auxiliary lens system 5 and the first reflecting mirror 6 are moved to the position shown by the dotted line on the rear optical axis of the main lens system 1. Then, the light flux from the subject passes through the main lens system 1 and the second auxiliary lens system 5, and is reflected at the first reflection m6 in a direction different from the optical axis 3 of the first imaging system, for example, in a right angle direction, and then fixed. The light is reflected by a second reflecting mirror 8 and guided onto a second imaging plane 9, and a second photographing system,
For example, it constitutes a long focal length photographing system. FIG. 3 is a schematic diagram of the optical system at this time, and 7 indicates the optical axis.

As described above, in this embodiment, by inserting and removing both the second auxiliary lens 5 and the first reflecting mirror 6 on the optical axis 3 of the first imaging system, switching from the first imaging system to the second wL shadow system and the like are possible. This facilitates quick reverse switching.

In this embodiment, the main lens system 1 has a positive refractive power, the first auxiliary lens system 2 has a negative refractive power, and the distance between both lens systems is set to such an extent that the second auxiliary lens system 5 and the first reflecting mirror 6 can be inserted. When expanded, the first photographing system is a telephoto type as a whole.

The second auxiliary lens system also has a negative refractive power and is placed close to the rear of the main lens system 1, and is connected to the first imaging plane 4 through two reflecting mirrors.
A second imaging system is constructed by guiding light to a second imaging plane 9 on substantially the same plane as the first image plane. As a result, a focal length longer than that of the first photographing system can be easily obtained.

In addition, by adopting the above configuration, the variable power ratio of both photographing systems is increased, and the total length of both lenses is shortened.
The aim is to downsize the entire lens system.

In this embodiment, when the first imaging system is used, the first reflection 'm
6. By appropriately arranging the second reflecting mirror 8 and the light shielding plate 10, the light flux is prevented from entering the second imaging plane 9 of the second photographing system.

In this embodiment, both the first photographing system and the second photographing system have a configuration in which the main lens system is placed on the subject side,
When focusing, by moving part or all of the main lens system, the amount of lens movement for the same subject is made equal in both WL shadow systems, which simplifies the mechanism when using an automatic focus detection device, for example. I'm trying.

In this embodiment, it is preferable to arrange the diaphragm behind the main lens system 1 or in the main lens system since it is not necessary to change it every time the photographing system is switched.

In the second photographing system, the reflection angle of the optical axis 7 by the first reflecting mirror is at an angle other than the right angle depending on the focal length and back focus length of the second photographing system, for example, at an angle θ as shown in FIG. The light may be reflected by the first and second reflecting mirrors.

The second auxiliary lens system 5 and the first reflecting mirror 6 may be moved in parallel, for example, as shown in FIG. 5, or as shown in FIG. It is also possible to rotate and move it.

1st. In both of the second photographing systems, as a method of shielding light from the other photographing system, for example, as shown in FIG. A method of arranging members 12 such as plates and shutters may also be used.

Next, numerical examples of the present invention will be shown. In numerical examples R
i is the radius of curvature of the i-th lens surface in order from the object side, D
i is the i-th lens thickness and air distance from the object side, Ni
and νi are the refractive index and Abbe number of the glass of the i-th lens, respectively, in order from the object side. Also, ■ is the main lens system, ■ is the first auxiliary lens system, and ■ is the second auxiliary lens system.

In addition, in Numerical Example 2, when switching from the first image removal system to the second imaging system, the main lens system is moved toward the object side, and the first auxiliary lens system is moved toward the image plane side, thereby increasing the distance between both lens systems. This secures a space in which the second auxiliary lens system and the first reflective surface are inserted.

Numerical Example 1 First imaging system F= 100 FNO= 1 : 3.5 2ω
= 49.4° 2nd imaging system F = 200.92 FNO = 1: 8 2ω =
25.8' Numerical Example 2 First imaging system F= 100 FNO= 1 : 2.8 2ω
= 56.8' 2nd imaging system F = 227.2 FNO = 1: 6.8 2
ω = 26.8' (Effects of the Invention) As described above, according to the present invention, by inserting and removing the auxiliary lens system and the reflecting mirror on the optical axis of the imaging system, the first imaging system and the second imaging system can be It is possible to easily select one of these, and to achieve a switchable magnification optical system with a simple configuration, in which the amount of movement of the lens system is equal when focusing on the same subject in both photographing systems. can.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an optical system according to an embodiment of the present invention, and FIG. Figure 3 shows the first imaging system and cram school 2w in the embodiment shown in Figure 1.
FIG. 4 is an explanatory diagram of the optical system of the shadow system; FIG. 4 is an explanatory diagram of another embodiment of the second photographing system in FIG. 1; 6th. FIG. 7 is a schematic diagram of an optical system according to another embodiment of the present invention, and FIG. FIG. 10 is a cross-sectional view of the lens of Numerical Example 1.2 according to the present invention, and FIG. FIG. 11 is a diagram of various aberrations of Numerical Example 1.2 according to the present invention. In the figure, 1 is the main lens system, 2 is the first auxiliary lens system, and 4 is the first lens system.
An imaging plane, 5 is a second auxiliary lens system, 6 is a first reflecting mirror, 8 is a second reflecting mirror, 9 is a second imaging plane, in the lens cross-sectional view and aberration diagram, (A) is the first imaging system; (B) shows the case of the second imaging system.

Claims (2)

[Claims] (1) A first imaging system and the main lens in which the light flux from the subject is guided to the first imaging plane by passing through the main lens system with positive refractive power and the first auxiliary lens system with negative refractive power in order. A second auxiliary lens system with a negative refractive power and a first reflecting mirror are both removably arranged on the rear optical axis of the system, and the light beam from the subject passes through the main lens system and the second auxiliary lens system in order. The first image forming surface is reflected by the first reflecting mirror in a direction different from the optical axis of the first imaging system, and then reflected by a second reflecting mirror disposed near the first imaging system. A switching type variable magnification optical system characterized in that one of the second imaging systems guided to a second imaging plane substantially on the same plane as the second imaging system can be selected. (2) In both the first photographing system and the second photographing system, focusing is performed by moving at least a part of the main lens system. Double optical system.