JPH11174325A - Zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a compact telephoto type zoom lens composed of six lens groups having specified refractive index and having variable power ratio of 2.5 to 6. SOLUTION: This lens is composed of six lens groups, that is, the 1st group having positive refractive index, the 2nd group having negative refractive index, the 3rd group having the positive refractive index, the 4th group having the negative refractive index, the 5th group having the positive refractive index, and the 6th group having the negative refractive index in order from an object side. In the case of varying power from a wide angle end to a telephoto end, plural lens groups including at least the 2nd group are moved to the object side and the lens is set to satisfy conditions; D1W<D1T, D2W>D2T, D3W<D3T, D4W>D4T and D5W>D5T when the distance between the i-th group and the (i+1)'th group at the wide angle end is DiW and that at the telephone end is DiT.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a telephoto zoom lens suitable for a film camera (photographic camera), a video camera, an electronic still camera, etc., and more particularly to a total of six lens groups. A telephoto type in which a predetermined lens group is moved to perform zooming and a high zooming ratio of about 2.5 to 6 and high optical performance over the entire zooming range while miniaturizing the entire lens system. It relates to a zoom lens.

[0002]

2. Description of the Related Art Conventionally, a zoom lens having a high zoom ratio and high optical performance has been required for a photographic camera, a video camera and the like. Among these, various telephoto-type multi-unit zoom lenses in which three or more lens units are moved to perform zooming have been proposed.

For example, a three-unit zoom lens composed of three lens units having positive, negative, and positive refractive power in order from the object side;
Four lens groups of positive, negative, positive and positive refractive power, or four lens groups consisting of four lens groups of positive, negative, negative and positive refractive power, positive, negative, positive, negative and positive refraction In a five-unit zoom lens composed of five lens units of power or five lens units of positive, negative, positive, positive, and negative refractive power, a multi-unit zoom lens in which a plurality of lens units are moved to perform zooming is provided. Various proposals have been made.

In these three-group zoom lens, four-group zoom lens, and five-group zoom lens, a plurality of lens units are moved to perform zooming, thereby reducing the size of the entire lens system while maintaining a predetermined zooming ratio. Have gained.

The present applicant discloses in Japanese Patent Application Laid-Open No. 4-186212 a high zoom ratio of about 10 which is composed of six lens units having positive, negative, positive, negative, positive and negative refractive power in order from the object side. A ratio zoom lens is proposed.

Further, the present applicant discloses in Japanese Patent Application Laid-Open No. Hei 8-29686 a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, and a negative lens unit in that order from the object side. There has been proposed a telephoto zoom lens having a zoom ratio of about 4, comprising six lens units, a fourth unit having a refractive power, a fifth unit having a positive refractive power, and a sixth unit having a negative refractive power.

[0007]

Generally, in a zoom lens, it is desired to increase the magnification (higher magnification) at the same time as making the entire lens system compact. To increase the magnification of a zoom lens, increase the number of lens groups that contribute to zooming,
In addition, there are a method of strengthening the zooming action by increasing the refractive power of each lens group, and a method of increasing the amount of movement of the lens group that contributes to zooming.

However, in the former case, it is necessary to increase the number of lens components in order to satisfactorily correct fluctuations of various aberrations caused by zooming, and it is difficult to make the entire lens system compact. Problems arise.

In the latter case, a large space must be secured for the movement of the lens unit due to zooming, and the overall length of the lens becomes long. There is a problem that it becomes difficult to support the group inside the lens barrel, and it becomes difficult to make the entire lens system compact.

According to the present invention, the zoom lens is composed of six lens groups having a predetermined refractive power as a whole, and the refractive power of each lens group, the moving conditions of each lens group for performing zooming, and the like are appropriately set. The objective of the present invention is to provide a telephoto zoom lens having a high zoom ratio of about 2.5 to 6 and having high optical performance over the entire zoom range while reducing the number of lenses and shortening the overall length of the lens. I do.

[0011]

According to a first aspect of the present invention, there is provided a zoom lens comprising: (1-1) a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, and a positive lens in order from the object side. A third group of refractive power of
The zoom lens has six lens units, a fourth unit having a negative refractive power, a fifth unit having a positive refractive power, and a sixth unit having a negative refractive power. At the time of zooming from the wide-angle end to the telephoto end, at least the A plurality of lens units including the two units are moved to the object side, and the air spacing at the wide-angle end and the telephoto end of the i-th unit and the (i + 1) -th unit is set to Di, respectively.
When W and DiT are set, the following condition is satisfied: D1W <D1T D2W> D2T D3W <D3T D4W> D4T D5W> D5T.

Further, the second invention provides (1-2) a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, and a negative refractive power in order from the object side. A fourth lens unit, a fifth lens unit having a positive refractive power, and a sixth lens unit having a negative refractive power. At the time of zooming from the wide-angle end to the telephoto end, at least the second unit is included. D1W <D1T D2W> D2T D3W <D3T When the plurality of lens units are moved to the object side, and the air intervals at the wide-angle end and the telephoto end of the i-th unit and the (i + 1) -th unit are DiW and DiT, respectively. D4W <D4T D5W> D5T is satisfied.

[0013]

1 to 4 are lens sectional views of Numerical Embodiments 1 to 4 of the first invention. 5 to 12 are aberration diagrams of Numerical Examples 1 to 4 of the first invention. 13 to 16
FIG. 17 is a lens sectional view of Numerical Examples 1 to 4 of the second invention, FIG.
24 to 24 are aberration diagrams of Numerical Examples 1 to 4 of the second invention.

In the figure, L1 is a first group having a positive refractive power, L2 is a second group having a negative refractive power, L3 is a third group having a positive refractive power, L4
Is a fourth group having a negative refractive power, L5 is a fifth group having a positive refractive power, L
Reference numeral 6 denotes a sixth group having a negative refractive power, and SP denotes a stop. Arrows indicate the movement trajectories of the respective lens units when zooming from the wide-angle end to the telephoto end.

In the first and second aspects of the present invention, at the time of zooming from the wide-angle end to the telephoto end, a predetermined lens group is moved so as to satisfy the above-mentioned condition.

In particular, in the first and second aspects of the present invention, as described above, the refractive power arrangement of each lens group is appropriately set, and the air gap between the lens groups at the time of zooming is changed to achieve a predetermined change. Variations in various aberrations during zooming, mainly fluctuations in various aberrations such as spherical aberration and coma aberration, are satisfactorily corrected while securing the magnification ratio.

As a result, good optical performance is obtained over the entire zoom range. In particular, at the time of zooming from the wide-angle end to the telephoto end, the second lens unit is moved toward the object side to easily secure a predetermined zoom ratio, and to shorten the overall length of the lens at the wide-angle end.

Next, the features of the lens structure of the first invention shown in FIGS. 1 to 4 will be described. In the first invention shown in FIGS. 1 to 4, at the time of zooming from the wide-angle end to the telephoto end, the distance between the first and second units increases, the distance between the second and third units decreases, and the third unit decreases. The distance between the fourth and fifth groups increases, the distance between the fourth and fifth groups decreases, and the distance between the fifth and sixth groups decreases.

In the numerical embodiments 1 and 4 shown in FIGS. 1 and 4, all of the first to sixth lens units are moved to the object side.
Further, in Numerical Example 2 of FIG. 2, the fourth unit is fixed, and all the other lens units are moved to the object side. In the numerical example 3 of FIG. 3, the fifth lens unit is fixed, and the first to third lens units and the sixth lens unit are fixed.
The group is moved to the object side, and the fourth group is moved to the image plane side.

By moving the lens unit having a predetermined refractive power to perform zooming as described above, the zooming effect can be appropriately performed.
It facilitates high magnification while shortening the overall length of the lens. The stop SP is moved integrally with the third lens unit.

The focus from infinity to a close object is first.
The group is moved to the object side. Note that a rear focus method in which the sixth unit is moved to the image plane side to perform focusing may be used.

In the zoom lens according to the first invention, the first lens unit includes, in order from the object side, a positive meniscus lens having a convex surface facing the object side, a negative meniscus lens having a convex surface facing the object side, It is composed of three lenses, a positive lens with the convex surface facing the object side.

The second lens unit comprises three lenses: a negative lens having both concave surfaces or a meniscus negative lens having a convex surface facing the object side, a negative lens having both lens surfaces concave, and a positive lens. .

The third lens unit is composed of two positive lenses, both of which have convex surfaces, and three negative lenses.

The fourth unit is composed of a single negative meniscus lens having a convex surface facing the image surface side.

The fifth unit is composed of three lenses: a negative meniscus lens having a convex surface facing the object side, and two positive lenses having both convex surfaces.

The sixth unit is composed of two negative lenses and a positive lens having a convex surface facing the image plane.

Next, the features of the lens configuration of the second invention shown in FIGS. 13 to 16 will be described. In the second invention shown in FIGS. 13 to 16, the first lens unit and the second lens unit are used for zooming from the wide-angle end to the telephoto end.
The distance between the groups increases, the distance between the second group and the third group decreases, the distance between the third group and the fourth group increases, the distance between the fourth group and the fifth group increases, and the distance between the fifth group and the fifth group increases. The distance between the sixth group is reduced.

Of these, numerical examples 1 and 2 shown in FIGS.
In 4, the first to sixth groups are all moved to the object side.
In the numerical examples 2 and 3 shown in FIGS. 14 and 15, the fifth lens unit is fixed, and all the other lens units are moved to the object side.

As described above, the zooming effect is appropriately performed by moving the lens group having a predetermined refractive power to perform the zooming, and the overall length of the lens is shortened and the high zooming is facilitated. The stop SP is moved integrally with the fourth lens unit.

Focusing from infinity to a close object is first.
The group is moved to the object side. Note that a rear focus method in which the sixth unit is moved to the image plane side to perform focusing may be used.

In the zoom lens according to the second aspect of the invention, the first lens unit includes, in order from the object side, a negative meniscus lens having a convex surface facing the object side, a positive meniscus lens having a convex surface facing the object side, It is composed of three positive lenses.

The second unit includes a negative lens having both concave lens surfaces,
It consists of two lenses, a meniscus positive lens with the convex surface facing the object side.

The third unit is composed of a cemented lens in which a positive lens and a negative lens are cemented.

The fourth unit includes a single meniscus negative lens having a convex surface facing the image surface side.

The fifth unit includes a cemented lens in which a positive lens and a negative lens are joined.

The sixth unit is composed of two lenses: a meniscus-shaped positive lens whose convex surface faces the image surface side, and a negative lens whose both lens surfaces are concave.

As described above, the first and second aspects of the present invention reduce the number of lenses by appropriately setting the refractive power of each lens group and the moving conditions of each lens group for performing zooming. A zoom lens with high optical performance over the entire zoom range has been achieved while shortening the overall length.

In the first and second aspects of the present invention, in order to further reduce aberration variation over the entire zoom range and obtain high optical performance over the entire screen, at least one of the following conditions is required.
It is good to satisfy one.

(A1) The amount of movement of the second lens unit during zooming from the wide-angle end to the telephoto end is M2, the focal lengths of the entire system at the wide-angle end and the telephoto end are fW and fT, and the natural logarithm is ln. In this case, the following condition is satisfied: 0.015 <ln (fT / fW) × | M2 | / fT <0.15 (1)

Conditional expression (1) indicates the amount of movement to the object side at the time of zooming from the wide-angle end to the telephoto end of the second group with respect to the focal length and the zoom ratio of the entire system at the telephoto end. Is assumed to be negative.). Beyond the lower limit of conditional expression (1), the second
As the amount of movement of the group decreases, the effect of shortening the overall length of the lens at the wide-angle end decreases.

When the amount of movement of the second lens unit is increased beyond the upper limit, other lens units, particularly the first and sixth lens units, are accordingly moved.
It is necessary to increase the amount of movement accompanying zooming of the group, and in order to realize such movement, the lens barrel structure becomes complicated,
It is not preferable because the outer diameter becomes large.

(A2) The first group includes one negative lens,
The second group has at least one negative lens and a positive lens, the third group has one negative lens and at least one positive lens,
The fifth group has one negative lens and at least one positive lens, the sixth group has at least one negative lens and one positive lens, and the focal length of the i-th group is f
i, when the focal lengths at the wide-angle end and the telephoto end of the entire system are fW and fT

[0044]

(Equation 2) 0.8 <f3 / | f2 | <1.7 (4) 0.8 <f5 / | f2 | <2 (5) 0.65 <| f6 | / | f2 | <2. 5 ‥‥‥ (6).

Conditional expressions (2) to (6) allow each lens group to be composed of a small number of lenses while ensuring predetermined optical performance.
This is for simplifying the entire lens configuration.

Conditional expression (2) defines the first group focal length with respect to the focal length of the entire system at the wide-angle end and the telephoto end. When the refractive power of the first lens unit is increased beyond the lower limit value of the conditional expression (2), the amount of change in the distance between the first lens unit and the second lens unit for zooming may be small. Spherical aberration and coma in the group become large, and it becomes difficult to correct the spherical aberration and the coma in a well-balanced manner by other lens groups.

If the refractive power of the first lens unit becomes weaker than the lower limit, the amount of movement of the first lens unit for obtaining a predetermined zoom ratio becomes large, which is not preferable. Conditional expression (3) defines the focal length of the second group with respect to the focal length of the entire system at the wide-angle end and the telephoto end.

If the refractive power of the second lens unit is increased beyond the lower limit of conditional expression (3), the amount of change in the distance between the first lens unit and the second lens unit for zooming may be small, but the lens system needs This is a retrofocus type refractive power arrangement, and the back focus becomes unnecessarily long, that is, the entire length of the lens is undesirably long. Also, when the refractive power of the second group is weakened below the lower limit,
The amount of movement of the first group for obtaining a predetermined zoom ratio becomes large,
Not preferred.

Conditional expression (4) defines the focal length of the third lens group with respect to the focal length of the second lens group. Conditional expression (4)
When the refractive power of the third lens unit is increased beyond the lower limit of the above condition, various aberrations generated in this lens unit become large, and it becomes difficult to correct this by another lens unit. On the other hand, if the refractive power of the third lens unit is weakened beyond the upper limit value, it is not preferable because spherical aberration particularly generated in the second lens unit cannot be corrected with good balance in this lens unit.

Conditional expression (5) defines the focal length of the fifth lens group with respect to the focal length of the second lens group. Conditional expression (5)
When the refractive power of the fifth lens unit is increased beyond the lower limit of the condition (1), it is advantageous for reducing the overall length of the lens, but undesirably deteriorates various aberrations. Further, if the refractive power of the fifth lens unit is weakened beyond the upper limit, the meaning of the lens system having the six lens units is lost.

The conditional expression (6) defines the focal length of the sixth lens group with respect to the focal length of the second lens group. Conditional expression (6)
When the refractive power of the sixth lens unit is increased beyond the lower limit of the condition (5), the tendency of the telephoto type is increased by the fifth and sixth lens units, which is advantageous for shortening the overall length of the lens system. Is difficult to ensure, and various aberrations are undesirably deteriorated.

If the refractive power of the sixth unit is weakened beyond the upper limit, the tendency of the telephoto type is weakened by the fifth and sixth units, and the lens system becomes longer.

(A3) The fourth unit is composed of one negative lens, and when the focal length of the i-th unit is fi, 1.5 <| f4 | / | f2 | <10 (7) Satisfy the conditions.

Conditional expression (7) is for forming the fourth unit with a single lens and favorably correcting various aberrations. The focal length of the fourth group is made smaller than the focal length of the second group. By making the refractive power relatively weak so as to fall within the range of the conditional expression, good optical performance can be obtained from the wide-angle end to the telephoto end.

Next, numerical examples of the first and second inventions will be described.
In the numerical examples, ri is the radius of curvature of the i-th lens surface in order from the object side, di is the i-th lens thickness and air gap from the object side, and ni and νi are the i-th lenses in order from the object side.
The refractive index and Abbe number of the glass of the second lens. or,
Table 1 shows the relationship between the above-described conditional expressions and various numerical values in the numerical examples.

[0056]

[Outside 1]

[0057]

[Outside 2]

[0058]

[Outside 3]

[0059]

[Outside 4]

[0060]

[Outside 5]

[0061]

[Outside 6]

[0062]

[Outside 7]

[0063]

[Outside 8]

[0064]

[Table 1]

[0065]

According to the present invention, as described above, the zoom lens is composed of six lens groups having a predetermined refractive power as a whole, and each lens group for performing the refractive power and zooming of each lens group. By appropriately setting the moving conditions of
A telephoto zoom lens having high optical performance over the entire zoom range and a zoom ratio of about 2.5 to 6 can be achieved while reducing the number of lenses and shortening the overall length of the lens.

In the first and second aspects of the invention, a so-called image stabilizing function for correcting camera shake and the like, and for displacing the image plane in a direction perpendicular or inclined to the optical axis for other purposes. It is possible to shift each lens group or some of the lenses in each lens group in a direction perpendicular to the optical axis or to tilt the optical axis, but preferably good optical performance is obtained. And the amount of movement of the lens group is small,
It is preferable to shift the second group in a direction perpendicular to the optical axis.

[Brief description of the drawings]

FIG. 1 is a sectional view of a lens according to a numerical example 1 of the first invention.

FIG. 2 is a sectional view of a lens according to a second numerical example of the first invention;

FIG. 3 is a sectional view of a lens according to a third numerical example of the first invention;

FIG. 4 is a sectional view of a lens according to a numerical example 4 of the first invention;

FIG. 5 is an aberration diagram at a wide angle end according to Numerical Example 1 of the first invention;

FIG. 6 is an aberration diagram at a telephoto end in Numerical Example 1 of the first invention;

FIG. 7 is an aberration diagram at a wide angle end according to Numerical Example 2 of the first invention;

FIG. 8 is an aberration diagram at a telephoto end in Numerical Example 2 of the first invention;

FIG. 9 is an aberration diagram at a wide angle end according to Numerical Example 3 of the first invention;

FIG. 10 is an aberration diagram at a telephoto end in Numerical Example 3 of the first invention;

FIG. 11 is an aberration diagram at a wide angle end according to Numerical Example 4 of the first invention.

FIG. 12 is an aberration diagram at a telephoto end in Numerical Example 4 of the first invention;

FIG. 13 is a sectional view of a lens according to a numerical example 1 of the second invention.

FIG. 14 is a sectional view of a lens according to a second numerical example of the second invention;

FIG. 15 is a sectional view of a lens according to a numerical example 3 of the second invention.

FIG. 16 is a sectional view of a lens according to a numerical example 4 of the first invention.

FIG. 17 is an aberration diagram at a wide angle end according to Numerical Embodiment 1 of the second invention;

FIG. 18 is an aberration diagram at a telephoto end in Numerical Example 1 of the second invention;

FIG. 19 is an aberration diagram at a wide-angle end according to Numerical Example 2 of the second invention.

FIG. 20 is an aberration diagram at a telephoto end in Numerical Example 2 of the second invention;

FIG. 21 is an aberration diagram at a wide angle end according to Numerical Example 3 of the second invention.

FIG. 22 is an aberration diagram at a telephoto end in Numerical Example 3 of the second invention;

FIG. 23 is an aberration diagram at a wide angle end according to Numerical Example 4 of the second invention.

FIG. 24 is an aberration diagram at a telephoto end in Numerical Example 4 of the second invention;

[Explanation of symbols]

 L1 First lens unit L2 Second lens unit L3 Third lens unit L4 Fourth lens unit L5 Fifth lens unit L6 Sixth lens unit SP Aperture IP image plane d d-line g g-line ΔS Sagittal image plane ΔM Meridional image plane

Claims (7)

[Claims] 1. A first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, a fourth lens unit having a negative refractive power, and a positive lens having a positive refractive power. The zoom lens has six lens units, a fifth lens unit and a sixth lens unit having a negative refractive power. At the time of zooming from the wide-angle end to the telephoto end, at least a plurality of lens units including the second unit are moved to the object side. In addition, assuming that the air intervals at the wide angle end and the telephoto end of the i-th lens unit and the (i + 1) -th lens unit are DiW and DiT, respectively, the following conditions are satisfied. A zoom lens characterized in that: 2. A first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, a fourth lens unit having a negative refractive power, and a positive lens having a positive refractive power in order from the object side. The zoom lens has six lens units, a fifth lens unit and a sixth lens unit having a negative refractive power. At the time of zooming from the wide-angle end to the telephoto end, at least a plurality of lens units including the second unit are moved to the object side. At the same time, assuming that the air intervals at the wide angle end and the telephoto end of the i-th lens unit and the (i + 1) -th lens unit are DiW and DiT, respectively, the following condition is satisfied. A zoom lens characterized in that: 3. The moving amount of the second lens unit during zooming from the wide-angle end to the telephoto end is M2, the focal lengths of the entire system at the wide-angle end and the telephoto end are fW and fT, and the natural logarithm is ln. When 0.015 <ln (fT / fW) × | M2 | / fT <
The zoom lens according to claim 1, wherein the following condition is satisfied: 0.15. 4. The first group has one negative lens and at least one positive lens, and the second group has at least one lens.
The third group has one negative lens and at least one positive lens, and the fifth group has one negative lens and at least one positive lens. The sixth unit has at least one negative lens and one positive lens, and the focal length of the i-th unit is fi, and the focal lengths of the entire system at the wide-angle end and the telephoto end are fW and fT. Equation 1 0.8 <f3 / | f2 | <1.7 0.8 <f5 / | f2 | <2 0.65 <| f6 | / | f2 | <2.5 Item 1. The zoom lens according to item 1, 2 or 3. 5. The fourth lens unit includes one negative lens, and satisfies the following condition: 1.5 <| f4 | / | f2 | <10 where fi is the focal length of the i-th lens unit. The zoom lens according to any one of claims 1 to 4, wherein 6. The zoom lens according to claim 1, wherein said fourth unit is fixed during zooming. 7. The zoom lens according to claim 1, wherein said fifth unit is fixed at the time of zooming.