JPS58140710A - High variable power zoom lens system - Google Patents

Abstract

PURPOSE:To obtain a zoom lens which has a variable power ratio of a wide range, and is satisfactory in its performance, by providing at least four lens groups, and executing zooming by moving at least three moving lens groups. CONSTITUTION:Five lens groups consist of the first lens groupIof positive refractive power, the second lens group II of negative refractive power, the third lens group III of negative refractive power, the fourth lens group IV of positive refractive power, and the fifth lens group V of positive refractive, power, in order from an object side, and in case of zooming, the third lens group is fixed, and the first groupI, the second lens group II and at least one lens group beyond the fourth group, for instance, the fourth lens group IV move on the optical axis. In the course of zooming a variable power effect of the second lens group II is increased by the first lens groupIwhich is moving, and also the first lens groupIis made to have a function for correcting the aberration.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a zoom lens having at least four lens groups and having at least three movable lens groups, comprising:
・In a zoom lens system, which is related to a zoom lens with a wide range of zoom ratios, at least two lens groups are It is necessary to move the lens along the axis.In recent years, there has been a desire in many quarters for such zoom lenses to have a large variable power ratio while also making the zoom lens system more compact. In order to obtain a compact zoom lens with a large zoom ratio, the refractive power of each moving lens group for zooming is strengthened, the amount of movement of the variable magnification lens group is reduced, and the distance between each lens group is narrowed. There is a way to do it
However, from the table, it is clear that if the refractive power of each moving lens group is strengthened for zooming, (1) it becomes difficult to correct aberrations. If this is not fully satisfied, the optical performance will be significantly degraded.

There are drawbacks such as.

Another method is to add a moving lens group for zooming. Japanese Unexamined Patent Publication No. 54-50855 (hereinafter referred to as "known zoom lens") proposes a zoom lens that performs zooming by moving six lens groups.

Known zoom lenses consist of six lens groups, and there are two methods: one method to perform a zoom lens by moving all three lens groups;
A method is disclosed in which zooming is performed by moving six lens groups. In any known zoom lens, zooming is performed by moving the lens group. The difference in the lens structure of this known zoom lens is that the known zoom lens consists of four lens groups, and a lens group with positive refractive power is inserted between the @2 lens group and the @3 lens group. ing.

However, a known zoom lens that performs zooming by moving three lens groups has a variable power ratio of 6 times, which cannot be said to be sufficient as a zoom lens.

SUMMARY OF THE INVENTION An object of the present invention is to provide a high variable power zoom lens system that has a high variable power ratio of 6 times and achieves good aberration correction while reducing the size of the entire zoom lens.

The lens structure of the high-power zoom lens system for achieving the object of the present invention is characterized by having at least four lens groups,
The four lens groups are, in order from the object side, the 1st lens group with positive refractive power, the 2nd lens group with negative refractive power, and the 6th lens group with negative refractive power.
and a fourth lens group with positive refractive power, in which the third lens group is fixed and the lens group and the @2 lens group are fixed.
Zooming is performed by moving each lens group and at least one lens group among the lens groups arranged below the fourth lens group. In particular, during zooming, the second lens group is moved by the moving lens group. In addition to increasing the zooming effect of the lens group, the lens group also has an aberration correction function.

By making the IE lens group have positive refractive power, it is possible to reduce the lens diameters of the second lens and below, thereby making the entire lens system more compact.

The distance between the object point and the field point is set to a negative value in order to make the lens more compact. @The 6th lens group has a fixed negative M refractive power to increase the pack focus of the zoom lens, and the positive refractive power of the 4th lens group and below is increased to achieve the desired magnification change effect with a small amount of movement of the 4th lens group. By obtaining this, we aim to make the zoom lens more compact. and the g-luns group and the second
By performing zooming by moving the lens group and at least one lens group below the fourth lens group independently, the degree of freedom in correcting aberrations is increased, and excellent aberration correction can be achieved despite high zoom ratios. -・ru.

Comparing the zoom lens according to the present invention with the above-mentioned known zoom lens, it can be seen that the zoom lens according to the present invention has a lens configuration in which a sixth lens group with a fixed negative refractive power is inserted during zooming. In particular, by inserting the @6 lens group with negative refractive power, the following effects can be obtained.

In other words, by creating a lens configuration in which the fixed s1!6 lens group is inserted, the positive refractive power of the fourth lens group located below this can be strengthened, and as a result, the positive refractive power of the fourth lens group located below this lens group can be strengthened. A magnification change effect can be achieved by changing the amount of movement, and
It becomes possible to keep the image plane constant. At this time, the moving lens group with positive refractive power is controlled by changes in the entrance back gate of paraxial rays incident on this lens group and the entrance height i of the pupil paraxial light beam.
By using the rotation of the lens, it is possible to effectively cancel out various aberrations that occur in the variable magnification system in front of the lens group with positive refractive power, especially fluctuations in spherical aberration and distortion, making the zoom lens more compact. can be achieved, and the degree of freedom in correcting aberrations can be increased. Also, in this case, the stronger the refractive power of the lens, the shorter the back focus, but by inserting the negative lens group, the back focus can be lengthened. Further, in the zoom lens according to the present invention, the zooming speed of the first V is lower at the telephoto end zoom position than at the wide angle end zoom position. By using a lens configuration in which the lens group is located on the object side and the second lens group is located on the image plane side, the zoom lens can efficiently perform the variable magnification function and can be made more compact. In other words, the zooming action of the second lens group is performed efficiently. Generally speaking, the zoom system in a single zoom lens uses the zooming action that occurs when the lens is brought close to a certain object point. The zoom lens of the present invention uses both of these two zoom methods at the same time to efficiently change the magnification. The above-mentioned lens configuration is adopted in order to perform the following.Next, the zoom lens according to the embodiment of the present invention will be explained with reference to each figure.Figure 1 shows the zoom lens according to the first embodiment of the present invention, which has five lens groups. FIG. 2 is an explanatory diagram of the optical arrangement of the zoom lens and the zoom locus during zooming. The arrows in the figure indicate the movement directions of the lens groups during zooming.The five lens groups in the figure consist of the fifth lens group V, which has refractive power on the object side.
In this embodiment, the third lens group is fixed, and the fourth lens group is movable on the optical axis. It has become.

Next, Table 1 shows the paraxial power arrangement of Example 1. Fi is the focal length of the fourth lens, and ei is the distance between the principal points of the lens group and the i+th lens group.

Table 1 Paraxial power arrangement of Example 1 FIG. 2 is an explanatory diagram of Example 2 of the present invention, and is illustrated similarly to the example of FIG. 1.

Embodiment 1 is composed of five lens groups, and when changing magnification, the first
．． Second. The lens configuration is such that the fourth lens group is moved, but in the second embodiment, the fourth lens is fixed and instead, the fifth lens group behind that lens group is moved to change the magnification. The paraxial refractive power arrangement of Example 2 is shown in Table 2 in the same way as Table 1. In Example 2 shown in Table 2, the third lens group or the fourth lens group ■ has a focusing function. There is a special feature that allows you to easily perform focusing operations.

Table 2 FIGS. 3 and 4 are explanatory diagrams of the optical arrangement and the zoom locus during zooming in Examples 3 and 4 of the present invention, which are composed of four lens groups.

Table 3 shows the paraxial power arrangement of Example 3, and Table 4 shows the paraxial power arrangement of Example 4. The examples shown in FIGS. 3 and 4 are both shown in Example 1. Second and fourth lenses! Zooming is performed by moving #.
As is clear from the figure, the zoom trajectories of the two lenses are different, and aberrations are corrected well by making changes appropriate to each refractive power arrangement.

Table 4 It is also possible to move only the lens group 1-'), or even to move two or more lens groups integrally or independently. FIG. 7 is an explanatory diagram of an optical arrangement and a zoom locus by zooming in Example 5 of the present invention.

Example 5 has a lens configuration consisting of five lens groups, in which the third lens group is fixed during zooming, and the remaining four lens groups are all moved.In this example, the fourth lens group and the fifth lens group Moving the group has the effect of relaxing the cam precision in shizooming and making it easier to manufacture.Table 5 shows the paraxial power arrangement of Example 5.

Table 5 In Examples 1 to 5 above, if only one lens group is moved non-linearly and the remaining lens groups are moved linearly, the manufacturing of the cam body installed in the lens barrel becomes easier. . or,
If two or more lens groups are moved non-linearly, the degree of freedom in movement increases, which is advantageous in correcting aberrations.

Next l! Table 6 shows a numerical example of a lens configuration at 9 o'clock by adopting the paraxial refractive power arrangement of Example 4 listed in Section 4.

Also, the sectional view of the zoom lens O lens at %lI6 is shown in
In addition, various aberration diagrams are shown in FIG. As is clear from Fig. 6.7, the total length of the V lens is extremely short, 7 pacts, and the aberrations are well corrected.

In the numerical examples, R1 is the gravity radius of the first lens surface from the object side, Di is the first lens thickness and air gap from the object side, and Ni and Wi are the i1th lens surface from the object side, respectively. These are the glass OJI refractive index and Atsube number of the O lens.

Table 6 JAM 1#-11111IQ -jam piece 11Q
-1-GQ-11Q Agony-ichieveneven@! @11 Spacing 1
g Figures 1 to 5 are explanatory diagrams of the optical arrangement and zoom locus of the embodiment of the present invention.

5aia is a cross-sectional view of a zoom lens according to an embodiment of the present invention, and FIG. 7 is a diagram showing various differences of the zoom lens shown in FIG. , indicates the zoom position at the intermediate and telephoto end, M indicates the meridional image plane, and S indicates the sagittal image plane.O Patent applicant: Canon Corporation OCu5

Claims (2)

[Claims] (1) It has at least 44 lens groups, and the 4' lens groups are, in order from the object side, a first lens group with positive refractive power and a second lens group with negative refractive power. Consisting of a third lens group with negative OR refractive power and a fourth lens group with positive refractive power, the third lens group is fixed, and the lens group, the second lens group, and the fourth V lens group are arranged below. 1. A high variable power zoom lens system, characterized in that zooming is performed by individually varying at least one of the lens groups arranged in the lens group. (2) The lens group is located on the object side, and the second lens group is located on the far side, which makes zooming easier at a zoom position at the telephoto end than at a zoom position at the wide-angle end. High variable power zoom lens system O according to claim 1