JPS58149015A - Zoom lens system - Google Patents

Abstract

PURPOSE:To reduce the size of a titlted lens system by making it constituted of at least the 1st lens group having positive refracting power, the negative 2nd and the 3rd lens groups, and the positive 4th lens group successively from an object side, fixing the 3rd lens group and moving at least the 2nd, the 1st and the 4th lens groups integrally. CONSTITUTION:Lens groups consists of the 1st lens groupIhaving positive refracting power, the 2nd lens group II having negative refracting power, the 3rd lens group III having negative refracting power, the 4th lens group IV having positive refracting power and the 5th lens group V having positive refracting power, successively from an object side. In the stage of zooming, the 3rd lens group is fixed, and the 2nd lens group II and the 5th lens group V as well as the 1st lens groupIand the 4th lens group IV are moved integrally. The 1st lens group and the 4th lens group as well as the 2nd lens group are moved linearly, and the 5th lens group is moved curvilinearly in order to hold the movement of the image picture caused by the zooming in a fixed position. In the tableIshowing the disposition of paraxial refracting powers, fi denotes the focal length of the i-th lens group, ei the distance between the principal points of the i-th lens group and the i+ lens group, and (f) the focal lengths in the zoom positions at the wide angle end, the intermediate and the telephoto end.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a zoom lens having at least four lens groups and having at least three movable lens groups,
In particular, the present invention relates to a zoom lens with a wide range of zoom ratios and good performance.

In a zoom lens system, in order to change the magnification while keeping the image point at a constant position, it is necessary to move at least two lenses # along the optical axis.

In recent years, it has been desired in various fields to reduce the size of such zoom lenses while maintaining a large variable power ratio.

Generally, in order to obtain a zoom lens that is compact and has a large zoom ratio, the refractive power of each moving lens group for zooming is strengthened, the amount of movement of the variable power lens group is reduced, and the distance t between each lens group is narrowed. I will explain how to do this.@However, if you strengthen the refractive power of each moving lens group for zooming,
(1) Good aberration correction becomes difficult.

(2) The lens group movement mechanism is required to have an extremely high stacking capacity, and if this is not fully satisfied, the optical performance will deteriorate sharply.

・For zooming, there is a method of increasing the number of Os excitation lens groups. A zoom lens that performs zooming has been proposed.The entire lens system of this known zoom lens consists of a lens group with a positive refractive power, a $12 lens group with a negative refractive power, and a $12 lens group with a positive refractive power. 3rd lens group, and 4 with positive refractive power
V's details 9. 2nd Lens group and @ Luns group and 3rd Lens group
Zooming is performed by integrating the lens group with I11/Ik.In this way, the zoom system allows the movement of the second lens group during zooming. 1) It is an advantage that a larger magnification change effect can be obtained.

In order to achieve the object of the present invention, the present invention aims to provide a zoom lens system that has a wide angle of view, high variable values, and good aperture while making the entire zoom lens smaller. The lens configuration of the zoom lens system has at least four characteristics.
The four lens groups are, in order from the object side, a first lens group with positive refractive power, a second lens group with negative refractive power, a third lens group with negative refractive power, and a third lens group with positive refractive power. The lens aI3 is fixed and at least the second lens group, the fourth lens group, and the fourth lens group are integrated and moved to perform zooming. The zooming effect of the second lens group O is increased by the second lens group that moves during zooming, and the second lens group also has an aberration correction function.

In particular, the WJ3 lens group is fixed during zooming [by setting it in a zoom lens system, it produces a special effect.

By giving the 1st lens group a positive refractive power, the diameter of the lenses below the 2nd lens can be made smaller, making the entire lens system more compact. The distance from the image point is set to a negative value to make the lens more compact.The third lens group has a fixed negative refractive power during zooming, which increases the zoom lens's dispersion and reduces @4v lens group or less. By increasing the positive refractive power of the 1m4 lens, a predetermined variable magnification effect can be achieved with a small amount of movement of the 1m4 lens, thereby making the zoom lens more compact. Or, if there is a positive refractive power O lens IPt after the fourth lens group, the paraxial sense - human radiation ^^ fluctuation that enters this lens group by the positive refractive power lens group, or - paraxial ray incidence Utilizing the fluctuation of the high pitch, it effectively cancels various aberrations occurring in the variable system of the lens group lCm with a refractive power of 100 degrees, as well as fluctuations in spherical aberration and distortion-aberration. p, it is possible to achieve miniaturization of the zoom lens and freedom in correcting aberrations 1
is increasing. In addition, at this time, the direction in which the refractive power of the lens group bends is the direction in which the pack 7 is distorted.
By adding the front lens #t - M, the back focus can be lengthened and vice versa, making it possible to configure an optical system similar to that used in eye reflex cameras, video cameras, etc. By integrating and moving the lens group and the fourth lens group, the moving cam structure on the lens barrel can be simplified, and the effect of moving the lens group and the movement of the fourth lens group can be efficiently achieved at the same time. In general, the zoom method for zoom lenses uses the variable magnification effect produced by burning a point and bringing the lens close to it, and the zoom method uses the magnification change effect produced by bringing the lens close to a certain point. The zoom lens system of the present invention employs the above-mentioned zoom methods and uses both of these two zoom methods at the same time to efficiently perform the zooming action. It is.

Advantageously, in the zoom lens according to the present invention, at the zoom position at the telephoto end, compared to the zoom position at the wide-angle end, the illll lens is located at the same position due to zooming, and the #1 iris 2 lens group is located at the image plane. By adopting a flexible lens structure, the magnification change function can be performed efficiently and the size of the zoom lens can be made smaller.

Next, a zoom lens according to an embodiment of the present invention will be explained with reference to each figure.
Theory of zoom locus ij I side @The arrow in the figure shows the movement direction of the lens group due to zooming.Five lenses 1 in the figure
# is a group of lenses with positive refractive power from the object side! , negative 0
A JIfI refractive power OG2 lens lens, a negative refractive power third lens, a positive refractive power fourth lens group, and a positive refractive power H5 lens are used for zooming.
The above ga lens group is identified], series 2 lens details, series 5
Lens review Ma A B GL lens sharp and II 4 lens #Summer and moved). The integrated lens group is moved linearly to the 4th lens group and the 2nd lens group, and the 5th lens group is moved linearly to maintain the image plane movement caused by zooming at a constant position. I'm letting you do it.

Next, Table 1 shows Example 1o paraxial power arrangement 1・fi is j
The focal length of the ii lens group, el is the focal length of the ii lens group and the t+th lens group.
Of is the focal length of the zoom position at the wide-angle end, middle, and telephoto end at that time.Table 1. Paraxial fracture 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. Example 1 is composed of five lens groups. Then, divide it by the magnification and get $1. $2. Summary 4. Although the lens configuration is such that the iris 5 lens details are moved, Example 2 is composed of 6 lens groups, and the 3rd lens group and the 5th lens group are fixed during zooming.
As for the lens review, while zooming, the J16 lens group, which moves as a unit for zooming, is moved like a trout and held at a constant position as the wI box moves during zooming, but the 6th lens group Even if the ρ・waCKJII5 lens group is used, the result is essentially the same.

The near @ refractive power arrangement of Example 2 is shown in Table 2 in the same way as Table 1. Table 2. Paraxial refractive power arrangement 883 of Example 2 is an explanatory diagram of the optical arrangement and zoom trajectory of Example 3 of the book @ Ming, which is similar to Fig. 1.
# in Table 3! Similar to t, the paraxial power distribution wtt- of Example 3
show.

implementation? Reference numeral 113 performs zooming by integrating and moving the Cfg2 lens group, the 4th lens group, and the 4th lens group, which are composed of four lens groups. The movement of the image plane due to zooming may be maintained at a fixed position by the #i second lens group or by the lens group and the fourth lens group.

Table 3. Paraxial power arrangement of Example 3 Focusing in the zoom lens according to the present invention is performed by moving the entire zoom lens. You may go, j! KFi 2 or more Vs
rMay be carried out by moving integrally or independently02
If a focusing system is adopted in which three or more lens groups are moved by S-movement, it will be possible to correct aberrations.

This makes it possible to easily perform combined S edge production.In Examples 1 to 3 above, if only one lens group is made nonlinear K11llb and the remaining p V lenses t# are moved linearly, the lens purchase can be easily performed. In addition, if two or more lens groups are moved non-linearly, the freedom of movement increases, which is useful in correcting aberrations.

Next, Table 4 shows a numerical example of the V-lens structure at the time of death using the paraxial power arrangement of the first embodiment shown in Table 1.

Also, the lens cross section vA of the zoom lens at -4 is j#
! As is clear from FIG. 4 and FIG. 4, which show diagrams of various aberrations, the overall length of the lens is extremely short and compact, and the aberrations are well corrected.

In the numerical example, R1 is the radius of curvature of the i-th lens surface in order of object similarity, and Di is the radius of curvature of the lens surface of the i-th scan in order of object resemblance.
The lens thickness and air spacing of the eye, Ni and ν5 are the refractive index and Atsube number of the glass of the first lens in a from the object condition, respectively. SL 1 bit ll
l5.

[Brief explanation of the drawing]

Claims (1)

[Claims] (1) It has at least four lens groups, and the four lens groups have a positive refractive power when viewed from the object side;
Negative refractive power nest 2 lens group, negative MAFr power (0743
Consists of a V lens group and a fourth lens group with positive refractive power,
A zoom lens system characterized in that the $3 lens*tm is fixed, and zooming is performed by integrating and moving at least the second lens group, the second lens group, and the fourth lens group. ) The JIl lens group and the IE11E4 lens group are located on the object side, and the 2nd lens group is located on the image side. A zoom lens system with a patented range of 1 range.