JPS58137812A - Inner focusing system of zoom lens - Google Patents

Abstract

PURPOSE:To enable focusing up to the nearest distance by moving the lens group except the 1st lens group on the side nearest the object among plural lens groups or part thereof over the entire zooming range for the purpose of focusing. CONSTITUTION:A zoom lens is so constituted that the lens group except the 1st lens group placed on the side nearest the object among the plural lens groups constituting the zoom lens or part thereof is moved over the entire zooming range for the purpose of focusing. The need for moving the 1st lens group which is generally large in aperture and is heaviest is eliminated by such constitution; therefore, the zoom lens can be made correspondingly lighter in weight and the lens group is required to be moved for a shorter length for focusing, thus the zoom lens of simpler constitution is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention focuses on
Lens groups other than the lens group of the IJ section (relating to an inner focusing method that performs focusing).

The following focusing methods have been conventionally used in zoom lenses.

−〇 Moths are also focused by moving the lens detail on the object side □ Focusing method '2) Focusing method by moving part of the lens detail <3) Macro 7 focusing method by moving arbitrary subgroups of the zoom lens system Among them, the method (l) is generally used with a trowel, and has the advantage of being able to perform seven orcasing with a simple mechanism. However, in telephoto zoom lenses, the focusing group, the 1st lens group, generally has a large aperture and tends to be heavy, and the amount of movement for focussing also tends to be large. The excavating mechanism is also large and looks like an eastern Amano. On the other hand, with wide-angle zoom lenses,
The amount of light incident around the Imm leg passing through the first lun group is large, and the peripheral light intensity decreases rapidly due to vignetting due to the movement of the first lun group for focusing. [1:1] It had the disadvantage that the deviceization of the first run details was unavoidable.

The cut-off method is a method to improve the above-mentioned drawbacks, but because it separates the lens group into a focusing lens group and other lens groups, it actually complicates the detailed structure of the lens group.

Other drawbacks also occurred, and the effectiveness was limited.

The method of η3) uses the method of C1) to round off the object to achieve a uniformly close distance, and performs 7-oakashi/g only at a specific focal length, and is only an auxiliary means to the method of (υ). ◎ In order to eliminate the drawbacks associated with each of the 7 focusing methods described above, the present invention eliminates the housing of the 7th focusing lens group, which is located closest to the object 11, and replaces the 7th focusing lens group with the
By using 2 orcasing for 2 orcasing, both the weight and size are small, and the amount of movement for 7 orcasing is also relatively small, making the 7 orcasing mechanism more compact than the previous method. This method provides a method that can perform 7 orcasing up to a sufficient short distance for silkworms.
This will be specifically explained with reference to Examples.

The implementation Ml is positive, negative, positive, positive 4# as shown in the broom 1 figure.
This is a zoom lens with a 1 & subtraction correction wrinkle, in which the second negative lens group is moved in the optical axis direction for zooming, and the resulting focus movement is corrected by movement of the third positive lens group. Focusing is performed by moving the third concave lens from the object side in the fourth lens group (so-called master lens) of this zoom lens to the side.

Actual tIpA example 1 General (Part of the lens group after variable power lens details.

(7) used for focusing (7) Even for the same object distance S, the amount of lens movement for focusing changes to VCf as shown in Figure 6 (r11) by varying the magnification. Generally, a mechanism for applying such a movement amount to an arbitrary focal length and an arbitrary object-to-image distance during zooming is extremely complicated and difficult to realize.

Even in such a case, the inventors have found that the relationship between the parameter f', which is obtained by converting the focal length f using an appropriate conversion function, and the lens movement amount for 7ocusing is expressed by one function F.
We discovered that there is a conversion function expressed as
- Invented a mechanism that allows focusing with sufficient precision using a single cam. (Japanese Patent Application No. 55-77124) That is, by converting the horizontal axis of FIG. 6(a) as shown in flit-[7, the curve group in FIG. 6<a) is slightly f-shaped, and By making a preliminary movement in the horizontal axis direction,
With sufficient scrutiny, the curves can be superimposed on one curve F shown in FIG. 6, 7b). As a result, sufficient accuracy can be achieved with a simple mechanism in which the amount of movement of the focusing section is determined by cams with different ranges corresponding to each of zooming and seven-focusing on the transferred amount curve shown in FIG. 6(b). Inner 7 focusing can be achieved in a zoom lens.

In addition, in this utterance, the wide angle 11f = 72■ Fig. 6<b)
Using the A-A' part of the movement amount curve, telephoto side f = 14
7■, the B-B' part of the same curve is used for 7 orcasing, but for wide-angle fog, the movement amount curve is A'-B'.
There is a rich part in B', and if you use this part you can focus very close! ll shadow distance can be further shortened, and so-called flow 7 orcasing can be easily realized on the same mechanism.

Hereinafter, the actual tIIA of the 7 ordering method of the present invention will be explained.
Give an example.

! l! Remaining example 2 Example 2 is an optical correction type that has a positive, negative, positive, and positive four-group configuration, and performs magnification by moving the first positive lens group and the third positive lens group as one unit in the optical axis direction. In this example of implementing the focusing method of the present invention in a zoom lens, focusing is performed by moving the negative lens of the second view from the object side in the fourth lens group to the image side.

Table 2 11I Right Example 3 Example 3 is composed of four groups: positive, negative, positive, and positive. Invention 7 of the IlI castle correction type zoom lens using the same method as in Example 1
This is an example in which the excusing method is introduced, and the second, third, and fourth negative, positive, and
Focusing is performed by moving three positive lenses as one unit toward the side. Table 3 Example 4 1! Example 4 consists of four lenses: positive, negative, negative, and positive, and the second lens moves in the optical axis direction for zooming.

The third lens group moves to compensate for focal shift due to zooming! If you move the 4th lens, 511st lens, and 6th negative lens, positive lens, and positive lens from the object side in the master lens group of the 4th detail correction type zoom lens as one unit to the object side, Tokuyosho zooming will occur. It is something to do.

Implementation 1F15 Implementation P15 consists of four parts: positive, negative, positive, and positive, and the second lens part and the third lens part are moved as one in the optical axis direction to change the magnification and correct the focal shift due to the change in magnification. for the 4th
This is a zoom lens in which the lens group moves, and the fourth lens group also moves the negative lens on the object side toward the image side to perform 7 focusing.

Cost 5 In Tables 6 to 15, for each example,
The movement amount of the seven focusing parts r with respect to the focal length f of the entire system, and the correspondence relationship of the conversion value of f on the f axis are shown for each example.

[Brief explanation of the drawing]

1 to 5 are cross-sectional views of the zoom lenses in Examples 1 to 5t, and FIGS. It is an optimized movement amount curve diagram. Patent applicant Konishiroku Photo Industry Aji Shiki Company applicant agent
Patent attorney Fumi Sato (and 1 other person) Figure 1 Figure 2

Claims (1)

[Claims] A zoom lens characterized in that among a plurality of lens groups constituting the zoom lens, a lens group other than the lens group placed closest to the object side, or a part thereof, is moved for focusing over the entire zooming range. Inner-7 orcasing method