JPH02195318A - Switching type variable power optical system - Google Patents

Abstract

PURPOSE:To reduce the quantity of the forward projection of the whole optical system and to speedily vary the focal length by selecting 1st - 4th photography systems and obtaining four kinds of focal length. CONSTITUTION:The 1st photography system obtains the 1st focal length by a 1st positive lens system 1 and the 2nd photography system obtains the 2nd focal length which is longer than the 1st focal length by the 1st positive lens system 1 and a negative lens system 3. Then the 3rd photography system has a 2nd reflecting mirror 5 inserted to obtain the 3rd focal length which is longer than the 2nd focal length by a 2nd positive lens system 2. The 4th photography system has the 2nd reflecting mirror 5 inserted to obtain the 4th focal length which is longer than the 3rd focal length by the 2nd positive lens 2 and the negative lens system 3. A lens driving means and a mirror driving means are driven by switch operation to select the 1st - 4th photography systems. Consequently, the quantity of the forward projection of the optical system can be reduced and the focal length values can be switched speedily.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a switching type variable magnification optical system that provides a plurality of focal lengths.

B. Prior art A method has been known in the past in which a converter is attached to a photographic lens to change the focal length.1 For example, using a single focal length lens with a focal length of 28 mm,
40 mm, 70 tn m, lO5m
To obtain four focal lengths of tn, two 1.4x converters and one 1.8x converter are required. In other words, a 1.4x converter is attached to this photographic lens to obtain a focal length of 40 mm, and a 1.8x converter is attached to this to obtain a focal length of 70 mm, and then a 1.4x converter is attached to this lens to obtain a focal length of 70 mm. attached to obtain a focal length of 105mm.

Problems to be Solved by the C0 Invention However, in the above method, in order to obtain a long focal length, it is necessary to install multiple converters, and the entire optical system protrudes forward, which reduces the stability of the camera during shooting. In addition to the problem, there is also the problem that it takes time to install the converter, making it difficult to take quick pictures.

The technical problem of the present invention is to make it possible to obtain four focal lengths without installing several converters.

Means for Solving the Problems 00 To explain with reference to FIG. 1 showing an embodiment, the switching type variable magnification optical system according to the present invention includes a first positive lens system l having a first refractive power, and this first positive lens system l having a first refractive power. a second positive lens system 2 which is arranged in parallel with the first positive lens system 1 and has a second refractive power different from the first refractive power; and a first positive lens system 2 which is inserted into the optical path of the first positive lens system 1.
A negative lens system 3 capable of taking an insertion position and a second insertion position inserted into the optical path of the second positive lens system 2, and driving this negative lens system 3 between the first insertion position and the second insertion position. a lens driving means 12 (FIG. 2), and a second positive lens system 2.
A first reflecting mirror 4 is inserted into the rear optical path of the first positive lens system 1 so as to reflect the reflected light from the first reflecting mirror 4 toward the photosensitive surface 6. a second reflecting mirror 5 that can take an insertion position where the light passing through the first positive lens system 1 is guided to the photosensitive surface 6, and a retracted position where the light is withdrawn from the rear optical path so as to guide the light that has passed through the first positive lens system 1 to the photosensitive surface 6; Chain drive means 13 (Figure 2) that drives between the insertion position and the retraction position
It is configured such that the first to fourth imaging systems shown below can be selected.

■First photographing system: As shown in FIG. 1(a), the negative lens system 3 is located at the second insertion position, the second reflection fa5 is located at the retracted position,
A first focal length is obtained by the first positive lens system 1.

Second photographing system: As shown in FIG. 1(b), the negative lens system 3 is located at the first insertion position, the second reflecting mirror 5 is located at the retracted position, and the first positive lens system 1 and negative lens system 3 to obtain a second focal length that is longer than the first focal length.

■Third photographing system: As shown in FIG. 1 (Q), the negative lens system 3 is located at the first insertion position, the second reflecting mirror 5 is located at the insertion position, and the second positive lens system 2 The third focal length is longer than the second focal length.
Obtain the focal length of

■Fourth photographing system: As shown in FIG. 1(d), the negative lens system 3 is located at the second insertion position, the second reflecting mirror 5 is located at the insertion position, and the second positive lens system 2 and negative lens system 3 to obtain a fourth focal length that is longer than the third focal length.

E0 effect For example, by driving the lens driving means 12 and the chain driving means 13 by operating a switch, the above-mentioned first to
Since the fourth imaging system can be selected, four types of focal lengths can be obtained without using a plurality of wearable converters as in the prior art.

In the above-mentioned sections and section E, which describe the present invention in detail, figures of embodiments are used to make the present invention easier to understand, but the present invention is not limited to the embodiments.

F. Example An embodiment of the present invention will be explained with reference to FIGS. 1 to 3.

FIG. 1 shows an example of a switching type variable magnification optical system according to the present invention.

This optical system includes a first positive lens system 1.

A second positive lens system 2, a negative lens system 3, and a first positive lens system 2 are arranged in parallel with the first positive lens system 1. a second reflecting mirror 4.5, and a photosensitive surface 6 of the film behind the first positive lens system 1.
is arranged.

The first positive lens system 1 has a first refractive power, and the second positive lens system 2 has a second refractive power different from the first refractive power. The negative lens system 3 is inserted into the optical path of the first positive lens system 1 at a first insertion position as shown in FIGS. 1(b) and (c), and at a first insertion position as shown in FIGS. 1(a) and (d). As shown in FIG. 2, it is movable between the second insertion position and the second insertion position where it is inserted into the optical path of the second positive lens system 2.

The first reflection @4 is inserted and fixed in the rear optical path of the second positive lens system 2, and reflects the light that has passed through the second positive lens system 2. The second reflecting mirror 5 is rotatable around an axis 5a, and has an insertion position where it is inserted into the rear optical path of the first positive lens system 1, as shown in FIGS. 1(Q) and (d). , Figure 1 (
As shown in a) and (b), it can take a retracted position in which it is retracted from this rear optical path. And this second reflecting mirror 5
When the mirror 4 is in the inserted position, the light reflected from the first reflecting mirror 4 is reflected toward the photosensitive surface 6, and when it is in the retracted position, the light that has passed through the first positive lens system 1 is guided to the photosensitive surface 6. It will be destroyed. Note that 7 is a shutter.

FIG. 2 shows a drive mechanism for the lens systems 1, 2.3 and the second reflecting mirror 5. As shown in FIG. 1st. Second positive lens system 1, 2
The negative lens system 3 is electrically driven 11J by a driving unit 11 having a motor, and is moved to the retracted position shown in FIG. 1(a), the intermediate position shown in FIGS. 1(b) and (e), and the first It can take the feeding position shown in Figure (d).

The negative lens system 3 is driven by the drive unit (lens drive means) 12 to the above-mentioned first insertion position or second insertion position,
The second reflecting mirror 5 is driven to an insertion position or a retracted position by a driving section (chain driving means) 13. These drive parts 1
1, 12, and 13 are connected to a control unit 14 including, for example, a CPU. The control unit 14 also includes first to fourth four
A changeover switch 15 that can be switched between two positions is connected to the switch 15.
Depending on the switching position of this switch 15, the driving units 11 to 13 are controlled according to the procedure shown in FIG.

When the changeover switch 15 is operated, the program shown in FIG. 3 is executed. First, in step S10, it is determined to which position the changeover switch 15 has been operated. If it is determined that the changeover switch 15 is in the first position, the process proceeds to step S11. . In step Sll, the driving section 11 drives the lens systems 1, 2.3 to the retraction position, the driving section 12 moves the negative lens system 3 to the second insertion position, and the driving section 13 moves the second reflecting mirror 5. Drive each to the retracted position. As a result, the first photographing system shown in FIG. Focal length at this time (first focal length)
is 28 mrn.

Further, if it is determined in step S1 that the changeover switch 15 has been operated to the second position, the process proceeds to step SL2.In step 312, the lens system 1.2.3 is driven to the intermediate position, and the negative lens System 3 in the first insertion position,
The second reflecting mirrors 5 are each driven to the retracted position. This forms the second photographing system shown in FIG. 1(b), and when the shutter 7 is opened in this state, the subject light passes through the first positive lens system 1 and the negative lens system 3 in order, and 6. Focal length ys at this time (second focal length 11111
) is 40mm.

Furthermore, if it is determined in step S1 that the changeover switch [5 has been operated to the third position, the process proceeds to step 813. In step S13, the lens systems 1, 2.3 are driven to the intermediate position, and the negative The lens system 3 is driven to the first insertion position, and the second reflecting mirror 5 is driven to the insertion position. As a result, the third photographing system shown in FIG. The light is sequentially reflected by the second reflecting mirrors 4 and 5 and guided to the photosensitive surface 6. The focal ratio at this time is 111
(Third focal length) is 70 mm.

Furthermore, when it is determined in step S1 that the changeover switch 15 has been operated to the third position, step S14
In step S14, the lens systems 1, 2.3 are driven to the extended position.

The negative lens system 3 is driven to the second insertion position 5, and the second reflecting mirror 5 is driven to the insertion position. As a result, the fourth photographing system shown in FIG. 1(d) is formed, and when the shutter 7 is opened in this state, the subject light passes through the second positive lens system 2 and the negative lens system 3 in order. The light is sequentially reflected by the first and second reflecting mirrors 4 and 5 and guided to the photosensitive surface 6. Focal length at this time (4th
The focal ratio l1l) is 105 mrn.

According to the above, since four focal lengths can be obtained with a single optical system, the amount of forward protrusion of the optical system can be reduced compared to the case where several 1Mi converters are installed to change the focal length. It becomes possible to quickly switch the focal length.

In addition, FIG. 4 shows not only the second reflecting mirror 5 but also the first reflecting mirror j.
! 4 also shows an example in which it is rotatably movable around the shaft 4a. The states of the first to third imaging systems shown in FIGS. 4(a) to (Q) are the same as those in FIGS. 1(a) to (0) described above. Figure 4 (d
) When forming the fourth imaging system shown in ), the first reflection t
lt4 is rotated by a predetermined amount in the clockwise direction, and the second reflection 1115 is rotated parallel to this. According to this K, since the optical path length of the reflected light from the first reflecting mirror 4 and the reflected light from the second reflecting mirror 5 is longer than that in FIG. 1(d), each lens system 1, 2.3 The same focal length (10
5mm) can be obtained. Therefore, the amount of protrusion of the entire optical system can be further reduced.

Although the lens system and the reflecting mirror are driven electrically in the above example, they may also be driven mechanically.Also, the lens system and the reflecting mirror may be driven simultaneously with the operation of the selector switch 5W15. Although the imaging system is formed, the lens system and the reflecting mirror may be driven by separate operating members. Furthermore, the focal length of each imaging system is not limited to the above-mentioned values.

G0 Effects of the Invention According to the present invention, the first to fourth imaging systems are configured to be selectable so that four types of focal lengths can be obtained.
In addition to being able to reduce the amount of forward protrusion of the entire optical system compared to the conventional case where a converter is attached, the focal length can be changed quickly.

[Brief explanation of the drawing]

1 to 3 show an embodiment of the present invention, FIG. 1 is a principle diagram showing a variable magnification optical system according to the present invention, FIG. 2 is a block diagram showing its drive system, and FIG. A flowchart showing the processing procedure, and FIG. 4 is a principle diagram of a variable magnification optical system showing another embodiment. ■=First positive lens system 2: Second positive lens system 3: Negative lens system 4: First reflecting mirror 5: Second reflecting mirror 11 to t3: G moving part 6: Photosensitive surface

Claims (1)

Claims: A first positive lens system having a first refractive power, and a second positive lens system disposed in parallel with the first positive lens system and having a second refractive power different from the first refractive power. a positive lens system; and a negative lens system that can take a first insertion position inserted into the optical path of the first positive lens system and a second insertion position inserted into the optical path of the second positive lens system. , a lens driving means for driving the negative lens system between the first insertion position and the second insertion position; a first reflecting mirror that reflects the light that has passed through the second positive lens system; an insertion position inserted into the rear optical path of the first positive lens system so as to reflect the light reflected from the first reflecting mirror toward the photosensitive surface; a second reflecting mirror capable of taking a retracted position where it is retracted from the rear optical path so as to guide the light toward a surface; and mirror driving means for driving the second reflecting mirror between the insertion position and the retracted position; a first imaging system in which the negative lens system is located at the second insertion position, the second reflecting mirror is located at the retracted position, and a first focal length is obtained by the first positive lens system; The lens system is located at the first insertion position, the second reflecting mirror is located at the retracted position, and the first positive lens system and negative lens system create a second focal point that is longer than the first focal length. a second photographing system for obtaining distance, the negative lens system is located at the first insertion position, the second reflecting mirror is located at the insertion position, and the second positive lens system measures the second focal length. a third imaging system that obtains a third focal length longer than , the negative lens system is located at the second insertion position, the second reflecting mirror is located at the insertion position, A switching type variable magnification optical system, characterized in that it is configured such that any one of the fourth photographing systems that obtains a fourth focal length longer than the third focal length by the lens system and the negative lens system can be selected.