JP2000321496A - Zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a four-group zoom lens having high optical performance over the entire power variation range by properly using aspherical surfaces and utilizing an inner focus system. SOLUTION: This zoom lens has a 1st group with positive refracting power which is fixed when the power is varied, a 2nd group with negative refracting power for power variation, a 3rd group with positive or negative refracting power for correcting image plane variation accompanying power variation, and a 4th group with positive refracting power which is fixed in this order from the object side. The 1st group has a 11-th group F1 with negative refracting power which is fixed at the time of focusing, a 12-th group F2 which performs focusing operation, and a 13-th group F3 with positive refracting power which is fixed at the time of the focusing and the 11-th group F1 and 13-th group F3 have aspherical surfaces respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens, and more particularly to a zoom lens having a large aperture, for example, an F-number of about 1.5 at the wide-angle end, by using an aspherical surface appropriately in a part of the lens system. Wide-angle end angle of view 2ω = 78 ° to 95 °)
The present invention relates to a zoom lens suitable for a television camera, a photographic camera, a digital camera, a video camera, and the like having excellent optical performance over the entire zoom range of a high zoom ratio of about 10 to 27. .

[0002]

2. Description of the Related Art Conventionally, large-diameter, high-magnification zoom lenses having high optical performance have been required for television cameras, photographic cameras, digital cameras, video cameras, and the like.

In addition to this, operability and mobility are particularly important in a color television camera for broadcasting, and in response to the demand, an image pickup device is also a small CCD (solid-state image pickup) of ／ inch or イ ン チ inch. Elements) have become mainstream.

Since the CCD has a substantially uniform resolution over the entire imaging range, a zoom lens using the CCD is required to have a substantially uniform resolution from the center of the screen to the periphery of the screen.

For example, it is desired that aberrations such as astigmatism, distortion, and chromatic aberration of magnification are well corrected and the entire screen has high optical performance. Large diameter, wide angle,
There is a demand for a high zoom ratio, small size and light weight, and a long back focus for disposing a color separation optical system and various filters in front of the imaging means.

A first group of positive refractive power for focusing (for focusing), a second group of negative refractive power for zooming, and an image plane that fluctuates with zooming in order from the object side of the zoom lens. The so-called four-unit zoom lens, which includes a fourth lens unit having a positive or negative refractive power for correcting the third lens unit and a fourth lens unit having a positive refractive power for imaging, has a relatively high zoom ratio. Since it is easy to increase the aperture, it is often used for zoom lenses for color television cameras for broadcasting.

[0007] Among the four group zoom lenses, the F number is 1.
For example, Japanese Patent Application Laid-Open No. 6-242378 proposes a four-unit zoom lens having a large aperture ratio of about 7, a wide-angle end angle of view of about 2ω = 86 °, a zoom ratio of about 8, and a high zoom ratio.

[0008]

In a zoom lens, a large aperture ratio (F number: 1.5 to 1.8), a high zoom ratio (zooming ratio: 10 to 27), an ultra wide angle (wide angle end angle of view 2ω = 2ω) In order to obtain high optical performance over the entire zoom range, it is necessary to appropriately set the refractive power and the lens configuration of each lens unit.

Generally, in order to obtain high optical performance with little aberration variation over the entire zoom range, it is necessary to increase the number of lenses in each lens unit, for example, to increase the degree of freedom in aberration correction design. .

Therefore, in order to achieve a zoom lens having a large aperture ratio and an ultra-wide angle and a high zoom ratio, the number of lenses increases and the entire lens system becomes large. It will not be possible to meet the demand for weight reduction.

[0011] First, regarding the imaging performance, distortion is the biggest problem with respect to ultra-wide-angle zoom lenses. This is because the distortion is affected by the cube of the angle of view in the region of the third-order aberration coefficient.

FIG. 29 is a schematic diagram showing a change in distortion at each zooming position in a zoom lens.

As shown in FIG. 29, the distortion is considerably under (minus) at the wide-angle end (focal length fw). From the wide-angle end fw to the desired end (focal length f
As the position goes to t), the value gradually increases in the over (plus) direction, passes through the zoom position where the distortion is 0, and the over value becomes maximum near the zoom position fm = fw × Z ^1/4 . Then, the over amount gradually decreases from the focal length fm to the telephoto end ft. Since this tendency increases as the angle of view at the wide-angle end increases, in an ultra-wide-angle zoom lens in which the angle of view 2ω at the wide-angle end exceeds 78 °, under distortion on the wide-angle side sharply increases, resulting in distortion. Becomes very difficult. Here, fw is the focal length at the wide-angle end, and Z is the zoom ratio.

Next, there is a problem in that the image contrast at the center of the screen is the best, that is, the fluctuation due to the so-called best image plane zooming. This is mainly due to the fluctuation of spherical aberration due to zooming. Since this spherical aberration is affected by the cube of the aperture in the region of the third-order aberration coefficient, it is the biggest problem in increasing the aperture.

Generally, assuming that the zoom ratio is Z and the focal length at the wide-angle end is fw, the zoom position fm = from the wide-angle end where the spherical aberration is 0 as shown in FIG.
Up to around fw × Z ^1/4 , there is an under (minus) tendency with respect to the Gaussian image plane. And the zoom position fm = fw
After about X ^1/4 , the under amount decreases, becomes 0 at a certain zoom position, and then tends to be over (plus).

Then, the on-axis light beam diameter is limited, and the F-number increases (the lens system becomes darker).
It becomes the most over (plus) near (Fno.w / Fno.t) × ft, and after this zoom position, the over amount decreases toward the telephoto end, and becomes almost zero at the telephoto end.

However, Fno. w, Fno. t is the F number at the wide angle end and the telephoto end, and ft is the focal length at the telephoto end.

As described above, it is very difficult to control the spherical aberration on the telephoto side particularly with a zoom lens having a zoom position where the F drop starts.

Conventionally, in order to satisfactorily correct such fluctuations of the aberration over the entire zoom range, correction has been conventionally made by increasing the number of focusing lens units and zooming lens units. For this reason, there is a problem that the entire lens system becomes large and complicated.

The introduction of an aspherical surface for solving such a problem has been proposed in the embodiment of the above-mentioned Japanese Patent Application Laid-Open No. 6-242378.

However, as the specifications of the zoom lens have been improved, it has become necessary to reconsider the method of introducing an aspheric surface in a zoom lens having a large aperture ratio and a high zoom ratio starting from a super wide angle.

In a zoom lens having a large aperture ratio and a high zoom ratio starting from an ultra-wide angle, the distortion greatly varies on the wide angle side, and the spherical aberration greatly varies on the telephoto side. It is becoming difficult to efficiently and satisfactorily correct the aberrations simply by introducing an aspherical surface on any of the surfaces of the variable power unit in order to satisfactorily correct both aberrations.

The present invention relates to a so-called four-group zoom lens,
By appropriately setting the refracting power and F-number value of each lens group and applying an aspherical surface to at least two lens surfaces, fluctuations in aberrations due to zooming are reduced, and especially distortion and telephoto on the wide-angle side are reduced. Satisfactorily corrects spherical aberration on the
It is an object of the present invention to provide a zoom lens having high optical performance over the entire zoom range.

In addition to the above, the present invention provides an F number 1.
5 to 1.8, super wide angle (wide angle end angle of view 2ω = 78 ° to 9
It is an object of the present invention to provide a zoom lens having a large aperture ratio of about 10 to 27 and a high zoom ratio.

[0025]

According to the first aspect of the present invention, there is provided a zoom lens having a first group of fixed positive refractive power and a second group of negative refractive power for zooming in order from the object side during zooming. Group, a third group having a positive or negative refractive power for correcting image plane fluctuation caused by zooming, and a fourth group having a fixed positive refractive power. The zoom lens includes a twelfth lens unit having a refractive power, a twelfth lens unit having a focusing action, and a thirteenth lens unit having a positive refractive power fixed at the time of focusing.
The group and the thirteenth group each have an aspherical surface.

According to a second aspect of the present invention, in the first aspect, the eleventh lens group has a maximum incident height of the on-axis light flux of the eleventh lens group as ht and an incident height of the off-axis light flux having the maximum angle of view at the wide angle end as h
w, when the off-axis luminous flux incident height of the maximum angle of view at the zoom position at the zoom ratio Z ^1/4 is hz, 1.30 <hw / h
t and at least 1 that satisfies 1.05 <hw / hz
Aspherical surface AS1 is applied to one of the lens surfaces, and the first
The third group is such that the maximum incident height of the axial light flux in the thirteenth group is ht,
The incident height of the off-axis light beam at the maximum angle of view at the wide-angle end is hw, and the zoom ratio Z is
^At least one lens surface satisfying 0.75> hw / ht is provided with an aspherical surface AS2 when an incident height of an off-axis light beam having a maximum angle of view at a zoom position at ^1/4 is hz. And

According to a third aspect of the present invention, in the first aspect of the present invention, the zoom ratio is Z, and the focal lengths of the first, eleventh, and thirteenth groups are f1, f11, f13, and the second, respectively. When the lateral magnification at the wide angle end of the group is β2w, Z> 10−0.42 <β2w <−0.18 {(1) −2.45 <f11 / f1 <−0.98} (2 1.05 <f13 / f1 <2.10 ‥‥ (3)

According to a fourth aspect of the present invention, in the second aspect of the present invention, when the aspherical surface AS1 is applied to a positive refracting surface, the aspherical surface AS1 has a shape in which the positive refracting power becomes stronger toward the peripheral portion of the lens. When applied to the refractive surface of the lens, the negative refractive power becomes weaker toward the periphery of the lens.
Assuming that the aspherical surface amounts at 100%, 90%, and 70% of the lens effective diameter are {1 (10), {1 (9), and {1 (7)}, respectively, 1.07 × 10 ⁻³ <| △ 1 (10) / f1 | <7.20 × 10 ⁻² 1.06 × 10 ⁻³ <| △ 1 (9) / f1 | <4.90 × 10 ⁻² 6.10 × 10 ⁻⁴ <| △ 1 (7) / f1 | <1.95 × 10 ⁻² (4)

According to a fifth aspect of the present invention, in the second aspect of the present invention, when the aspheric surface AS2 is applied to a positive refractive surface, it has a shape in which the positive refractive power becomes weaker toward the lens peripheral portion, When applied to the refracting surface of the aspherical surface AS2, the negative refractive power becomes stronger toward the peripheral portion of the lens.
Assuming that the aspherical surface amounts at 100%, 90%, and 70% of the lens effective diameter are {2 (10), {2 (9),} 2 (7), respectively, 2.15 × 10 ⁻³ <| △ 2 (10) / f1 | <2.45 × 10 ⁻² 1.35 × 10 ⁻³ <| △ 2 (9) / f1 | <1.60 × 10 ⁻² 4.85 × 10 ⁻⁴ <| △ 2 (7) / f1 | <5.60 × 10 ⁻³ ‥‥‥ (5)

According to a sixth aspect of the present invention, in the first aspect, the eleventh lens unit includes at least two negative lenses and one positive lens from the object side, and the negative lens closest to the object side is strong on the image plane side. When forming a meniscus shape or a plano-concave shape with the concave surface facing, the average of Abbe numbers of the materials of the at least two negative lenses is Δν11n, and the Abbe number of the materials of the positive lens is Δν11p, Δν11n− △ ν11p> 26.5 ‥‥‥ (6).

According to a seventh aspect of the present invention, in the first aspect of the present invention, the twelfth lens unit moves to the image plane side when focusing from an object at infinity to an object at a close distance, and has a shape having a convex surface facing the image plane side. It is characterized by having at least one positive lens.

According to an eighth aspect of the present invention, in the first aspect of the present invention, the thirteenth group includes at least one negative lens and three positive lenses, and the Abbe number of the material of the negative lens is △ ν13n, When the average of the Abbe numbers of the materials of the two positive lenses is △ ν13p, the following condition is satisfied: Δν13p−Δν13n> 37.4 ‥‥‥ (7).

[0033]

FIG. 1 is a sectional view of a lens at a wide angle end according to Numerical Embodiment 1 of the present invention. FIGS. 2 to 6 show focal lengths f = 5 and f = 8 in Numerical Embodiment 1 of the present invention. .89, f = 12.5
It is an aberration figure at the time of 0, f = 37.50, and f = 50.

FIG. 7 is a sectional view of a lens at a wide angle end according to a second numerical embodiment of the present invention. FIGS. 8 to 12 show focal lengths f = 5.50 and f = 10.24 in the second numerical embodiment of the present invention. , F = 22.
FIG. 7 is an aberration diagram when 0, f = 46.75, and f = 66.

FIG. 13 is a sectional view of a lens at a wide angle end according to Numerical Embodiment 3 of the present invention. FIGS. 14 to 18 are Numerical Embodiment 3 of the present invention.
F = 6.7, f = 15.27, f = 3
It is an aberration figure at the time of 3.5, f = 107.2, f = 180.9.

FIG. 19 is a sectional view of a lens at a wide-angle end according to Numerical Embodiment 4 of the present invention. FIGS. 20 to 24 are Numerical Embodiment 4 of the present invention.
F = 6.7, f = 15.27, f = 2
It is an aberration figure at the time of 8.66, f = 67.55, and f = 180.9.

In the lens cross-sectional view, F is a focus unit (front lens unit) having a positive refractive power as a first unit.
A fixed negative refractive power 11th lens unit F11 having at least two negative lenses and one positive lens, a focusing twelfth lens unit F12, and a fixed positive refractive power thirteenth lens unit F13. Have.

V is a variator of negative refracting power for zooming as a second lens unit, which moves from the wide-angle end (wide) to the telephoto end (tele) by moving monotonously on the optical axis toward the image plane side. The magnification is changed. C is a compensator having a negative refractive power as a third lens unit. The compensator moves non-linearly on the optical axis with a locus convex toward the object side in order to correct image plane fluctuation due to zooming. I have. The variator V and the compensator C constitute a variable power system. SP is a stop, and R is a fixed relay group having a positive refractive power as a fourth group. P denotes a color separation prism, an optical filter, and the like, and is shown as a glass block in FIG. IP is an image plane.

In the present embodiment, by providing at least one aspherical surface AS1 in the eleventh lens unit and at least one aspherical surface AS2 in the thirteenth lens unit, high optical performance is obtained over the entire zoom range.

Further, high optical performance is obtained over the entire object distance by minimizing aberration fluctuation when focusing is performed by the twelfth lens unit.

The zoom lens aimed at by the present invention is achieved by the above-described configuration, but it is preferable to further satisfy at least one of the following conditions in terms of aberration correction.

(A-1) In the eleventh lens group, the maximum incident height of the axial light flux in the eleventh lens group is ht, the incident height of the off-axis light flux at the maximum angle of view at the wide-angle end is hw, and the zoom ratio Z ^1/4 is Assuming that the incident height of the off-axis light flux at the maximum angle of view at the zoom position is hz,
At least one lens surface that satisfies 30 <hw / ht and 1.05 <hw / hz is provided with an aspherical surface AS1, and the thirteenth lens unit sets the maximum incident height of the axial light flux in the thirteenth lens unit to ht. , The incident height of the off-axis light beam at the maximum angle of view at the wide-angle end is h
0.75> hw / ht where hz is the incident height of the off-axis light beam at the maximum angle of view at the zoom position at a zoom ratio of Z ^1/4
Aspherical surface AS2 is applied to at least one lens surface satisfying the following condition.

In the present invention, in order to correct distortion on the wide-angle side which is affected by the cube of the angle of view, all the lens surfaces constituting the first lens unit (front lens unit) are all changed in the eleventh lens unit. In the magnification range, the maximum incident height of the on-axis light beam is ht, the incident angle of the off-axis light beam having the maximum angle of view at the wide angle end is hw, and the incident angle of the off-axis light beam having the maximum angle of view at the zoom position at the zoom ratio Z ^1/4 . Where hz is 1.30 <hw / ht and 1.05 <hw / h
The aspheric surface AS1 is applied to at least one surface that satisfies z, and the maximum incidence of the axial light flux in the entire zoom range in the thirteenth group in order to correct spherical aberration on the telephoto side that is affected by the cube of the aperture. When the height is ht, the off-axis light flux incident height at the maximum angle of view at the wide-angle end is hw, and the off-axis light flux incident height at the maximum zoom angle at the zoom ratio at the zoom ratio Z ^1/4 is hz, 0.75> hw
/ Ht and at least one lens surface satisfying 0.80> hw / hz is provided with an aspherical surface AS2.

This effectively corrects the distortion (distortion) which becomes maximum at the zoom position near the zoom ratio Z ^1/4 .

Next, the features of the aspherical surface of the zoom lens according to the present invention will be described. Angle of view 2ω = 78 ° at wide-angle end
In a zoom lens having a zoom ratio of about 10 to 27 times starting from 95 [deg.], The incident height of on-axis rays to the front lens group and the variator sequentially increases from the wide-angle end to the telephoto end as shown in FIGS. That is, in a zoom lens having an F-drop, it becomes highest at the F-drop start position (zoom position fd, FIG. 27). At the telephoto end, the drop is constant in the front lens group due to the F-drop and low in the variator.

On the other hand, at the wide-angle end, the incident height of the off-axis ray passes through the entire effective diameter of the eleventh lens group among the front lens groups, but the zoom position is fm = fw ×
In Z ^1/4 incidence height in the 11 group abruptly lowered,
Conversely, the incident height in the thirteenth group among the front lens groups sharply increases. This tendency becomes remarkable when aiming at wide angle, high magnification, and small size and light weight.

When an aspherical surface is provided to the front lens unit to suppress aberration fluctuations, a single aspherical surface efficiently corrects both the distortion that varies greatly on the wide angle side and the spherical aberration that varies greatly on the telephoto side. Can not do it. It is because distortion and spherical aberration differ greatly in aspherical shape and the amount of aspherical surface for correcting each due to the problem of properties as aberrations. This has an adverse effect, such as higher-order aberration, on this aberration.

Conversely, the aspherical shape of the aspherical surface AS1 has an adverse effect on the distortion at the zoom position at the zoom ratio Z ^1/4 , and the front lens at the zoom position at the zoom ratio Z ^1/4 . Over (plus) due to strong positive refractive power in the group
Is more strongly jumped up by the aspherical effect, it becomes difficult to suppress the distortion.

Therefore, satisfying the above condition of 1.30 <hw / ht is necessary only in the vicinity of the wide-angle end in the entire zooming range, because the off-axis ray passes through and the incident height of the on-axis ray on the telephoto side. Is large, and thereby, the distortion aberration at the wide-angle end due to the widening of the angle is favorably corrected, and the influence on the fluctuation of the spherical aberration on the telephoto side is suppressed as much as possible. In addition, simultaneously satisfying the above condition of 1.05 <hw / hz means that off-axis rays pass only near the wide-angle end in the entire zoom range, and near the zoom position at the zoom ratio Z ^1/4 . Indicates that the difference between the maximum angle of view and the incident height of the off-axis light beam is large, and the over (plus) caused by the strong positive refractive power of the front lens group at the zoom position at the zoom ratio Z ^1/4 is shown. It is avoided as much as possible to jump up the distortion aberration more strongly by the aspherical effect. In this way, the distortion aberration at the wide-angle end due to widening of the angle is favorably corrected, and the influence on the fluctuation of the spherical aberration on the telephoto side is minimized.

Regarding the aspherical surface AS2 of the 13th lens group, satisfying the above-mentioned condition of 0.75> hw / ht means that an axial ray passes only near the telephoto end in the entire zoom range, and This shows that the difference from the incident height of off-axis rays on the wide-angle side is large, and this allows the spherical aberration at the telephoto end due to the increase in magnification to be corrected well while affecting the fluctuation of distortion on the wide-angle side. It is suppressed as much as possible.

As an additional effect of the aspherical surface AS2, the off-axis ray height in the front lens group at the zoom position fm = fw × Z ^1/4 sharply increases, so that off-axis rays are reduced by the front lens group. It is also possible to suppress over (plus) of distortion due to the strong refraction caused by the positive refracting power. In other words, it is very effective to apply an aspheric surface to the lens surface of the thirteenth lens group of the front lens group in which the on-axis ray incident height on the telephoto side is high and the off-axis ray incident height on the wide angle side has a large change. Become.

The aspherical surfaces AS1 and AS2 exert a greater effect when they are arranged as far apart as possible due to the difference in their aberration correction effects. Therefore, as a block, the first group having the largest thickness is divided into three, and the twelfth group is set to the inner focus to set an appropriate distance between the aspherical surface AS1 and the aspherical surface AS2. The maximum aberration correction effect can be achieved with only two aspheric surfaces.

As described above, in the present embodiment, the lens surface on which the aspherical surface is formed is appropriately set, the distortion on the wide-angle side and the fluctuation of the spherical aberration on the telephoto side are satisfactorily corrected, and a high optical power is obtained in the entire zoom range. Has gained performance.

(A-2) The zoom ratio is Z, the first group, the first
The focal lengths of the first lens group and the thirteenth lens group are respectively f1 and f1
1, f13, the lateral magnification of the second group at the wide-angle end is β2
Assuming that w, Z> 10−0.42 <β2w <−0.18 (1) −2.45 <f11 / f1 <−0.98 (2) 1.05 <f13 / f1 <2.10 ‥‥‥ (3)

The present invention has a zoom ratio Z of 10 times or more,
In order to realize an ultra-wide-angle zoom lens with a wide-angle end angle of view 2ω exceeding 78 ° and a zoom lens with a large aperture over the entire zoom range, first, a variator (second group) at the wide-angle end of the entire system Is set as in the conditional expression (1), and the optimal power (refractive power) is set for a wide angle.

The refractive power of the eleventh lens unit is set so as to satisfy the conditional expression (2). This is because, by arranging a lens group having a strong diverging function on the most object side of the first lens unit, the refractive power of the entire first lens unit is strengthened to realize a wide angle, and at the same time, a focusing effect is achieved. The twelfth lens unit has an appropriate diverging function in order to improve the aberration correcting function when moving on the optical axis.

When the value exceeds the upper limit of conditional expression (2), the diverging effect becomes insufficient, and it becomes difficult to widen the angle of the entire zoom lens system. In addition, a large fluctuation in aberration due to focusing remains. . If the lower limit of conditional expression (2) is exceeded, the diverging effect becomes excessive and negative spherical aberration and the like increase sharply.
It becomes difficult to correct aberrations in the second group and the thirteenth group.

When the value exceeds the upper limit of conditional expression (3), the radius of curvature of the lens surface constituting the thirteenth lens unit becomes sharply small, so that aberration variation particularly on the telephoto side increases. To correct this, a large number of lens components is required as a degree of design freedom, which makes it difficult to increase the aperture and reduce the size.

If the lower limit of conditional expression (3) is exceeded, the positive Petzval sum significantly decreases, and it is difficult to correct negative spherical aberration generated in the eleventh lens unit and negative Petzval sum generated in the variator V. turn into. If the upper limit is exceeded, the principal point of the front lens group as a whole enters the image plane side, which has an adverse effect on miniaturization.

(A-3) When the aspheric surface AS1 is applied to the positive refracting surface, it has a shape in which the positive refracting power becomes stronger toward the periphery of the lens, and when applied to the negative refracting surface. Has a shape in which the negative refractive power becomes weaker toward the lens peripheral portion, and is 100%, 90%, 70% of the effective lens diameter of the aspherical surface AS1.
非 1 (10), △ 1 (9),
1.01 × 10 ⁻³ <| △ 1 (10) / f1 | <7.20 × 10 ⁻² 1.06 × 10 ⁻³ <| ６1 (9) / f1 | <4.90 × 10 ⁻² 6.10 × 10 ⁻⁴ <| △ 1 (7) / f1 | <1.95 × 10 ⁻² ‥‥‥ (4)

When the aspheric surface AS1 is provided on the positive refracting surface in the eleventh group for correcting the fluctuation of distortion on the wide-angle side, the positive refractive power increases toward the lens periphery. When it is applied to the negative refracting surface, the negative refracting power becomes weaker toward the periphery of the lens, so that the distortion near the wide-angle end becomes under (minus). , The variation of the distortion on the wide-angle side is favorably corrected.

Further, in the present invention, the aspherical surface AS of the eleventh lens group
In order to satisfactorily correct the distortion at the wide-angle end due to widening of the aspherical surface shape of No. 1 in order to satisfy the conditional expression (4), the central portion of the aspherical surface is almost spherical, and the aspherical surface is closer to the periphery. The shape is large.

The above-mentioned conditional expression (4) indicates that the zoom lens has the aspherical surface distortion correcting effect only in a small part of the zoom range near the wide-angle end in the zooming system in the zooming system. This is for minimizing the influence on spherical aberration, astigmatism, coma aberration and the like in the region.

(A-4) When the aspheric surface AS2 is applied to the positive refracting surface, it has a shape in which the positive refracting power becomes weaker toward the lens periphery, and when applied to the negative refracting surface. Has a shape in which the negative refractive power becomes stronger toward the periphery of the lens, and is 100%, 90%, 70% of the effective lens diameter of the aspherical surface AS2.
非 2 (10), △ 2 (9),
When Δ2 (7) is satisfied, 2.15 × 10 ⁻³ <| Δ2 (10) / f1 | <2.45 × 10 ⁻² 1.35 × 10 ⁻³ <| Δ2 (9) / f1 | <1.60 × 10 ⁻² 4.85 × 10 ⁻⁴ <| {2 (7) / f1 | <5.60 × 10 ⁻³ } (5)

When the aspheric surface AS2 is provided with an aspheric surface for correcting the variation of spherical aberration on the telephoto side on the positive refractive surface in the thirteenth group, the positive refractive power increases toward the lens periphery. Spherical aberration near the telephoto end will be under (minus) by forming a shape that becomes weaker and applying a negative refractive power to the negative refractive surface when applied to the periphery of the lens. Is corrected, the fluctuation of spherical aberration on the telephoto side is favorably corrected.

In order to satisfactorily correct the distortion at the telephoto end by increasing the magnification of the aspherical surface of the aspherical surface AS2 of the thirteenth lens group, the aspherical surface must satisfy the above-mentioned conditional expression (5). The central portion has a substantially spherical shape, and the aspherical surface becomes larger toward the periphery.

The above-mentioned conditional expression (5) allows the zoom lens to perform the aspherical spherical aberration correction effect only in a very small part of the zoom range near the telephoto end in the zooming system in the zooming system. This is for minimizing the influence on astigmatism, coma aberration and the like in the region.

(A-5) The eleventh unit is composed of at least two negative lenses and one positive lens from the object side, and the negative lens closest to the object side has a meniscus shape or flat shape with a strong concave surface facing the image plane side. A concave shape, said at least two
Assuming that the average of the Abbe numbers of the materials of the two negative lenses is △ ν11n and the Abbe number of the material of the positive lens is △ ν11p, the condition of Δν11n− △ ν11p> 26.5 ‥‥‥ (6) is satisfied. It is.

This is related to the front lens unit. The eleventh unit is composed of at least two negative lenses and at least one positive lens in order from the object side, and the negative lens closest to the object side has a strong concave surface facing the image plane side. The meniscus or plano-concave shape minimizes distortion at the wide-angle end.

Further, the achromatic condition (6) in the eleventh lens unit is satisfied, and the achromaticity of off-axis rays on the wide-angle side is particularly well corrected.

If the lower limit of conditional expression (6) is exceeded, achromaticity will be insufficient, and large variations in chromatic aberration of magnification on the wide-angle side will remain.

(A-6) The twelfth lens unit has at least one positive lens which moves toward the image plane when focusing from an object at infinity to an object at a close distance, and has a convex surface facing the image plane. That is.

The twelfth lens group satisfactorily corrects aberration fluctuations due to subject distance by introducing a so-called inner focus method in which the object moves to the image plane side when focusing from an object at infinity to an object at a close distance. And achieves effects such as reduction of focus operation torque.

The twelfth lens unit includes at least one positive lens. The shape of the twelfth lens unit has a shape with a strong convex surface facing the image plane side, thereby correcting distortion that greatly fluctuates under (minus) at the wide angle end. Have achieved.

(A-7) The thirteenth lens unit is composed of at least one negative lens and three positive lenses. The Abbe number of the material of the negative lens is Δν13n, and the Abbe number of the material of the at least three positive lenses. Is the average of Δν13p, the condition Δν13p−Δν13n> 37.4 ‥‥‥ (7) is satisfied.

The thirteenth group includes at least one negative lens and at least three positive lenses.

Further, the achromatic condition (7) in the thirteenth lens group is satisfied, and the achromaticity of axial rays on the telephoto side is particularly well corrected. If the lower limit of conditional expression (7) is exceeded, achromatism will be insufficient and axial chromatic aberration on the telephoto side will remain largely.

Next, the features of each embodiment (numerical embodiment) of the present invention will be described. Embodiment 1 shown in FIG. 1 has a zoom ratio of 10 times, and the wide-angle end angle of view 2ω exceeds 95 °.
R1 to R17 are front lens units F. R1 to R8
Denotes a fixed first lens unit F11 having a negative power (refractive power) at the time of focusing, and R9 to R10 have a focusing effect and move to the image plane side when focusing from an object at infinity to an object at a close distance. A twelfth lens group F12, from R11 to R17
Denotes a thirteenth group F13 which is fixed at the time of focusing and has a positive power. R18 to R26 are variators V that move monotonously from the wide (wide-angle end) to the tele (telephoto end) to the image plane side for zooming. Reference numerals R27 to R29 denote compensators C having an effect of correcting image points accompanying zooming, have negative power, and move in a convex arc toward the object side when zooming from wide to tele. SP (30) is an aperture. R31 to R47 are relay groups R having an imaging action
And R48 to R50 are glass blocks equivalent to the color separation prism.

In the first embodiment, if the lateral magnification of the variator at the wide-angle end of the entire zoom lens system is β2w, β2w =
A power (refractive power) arrangement of −0.392 corresponds to an ultra-wide angle.

In order to increase the angle of view, in the front lens group, since the incident height of off-axis rays becomes large on the wide-angle side, the eleventh group F11 having a large influence on aberrations on the wide-angle side is sequentially concaved from the object side. Negative), concave (negative), concave (negative), convex (positive) lenses, and the concave lens closest to the object side should have a meniscus shape or a plano-concave shape with a strong concave surface facing the image surface side. This suppresses the occurrence of distortion in the front lens group.

As a focusing method, a twelfth lens group F
By adopting a so-called inner focus method in which the focus movement group 12 is used, aberration fluctuation due to subject distance can be corrected well, and at the same time, effects such as miniaturization of the entire zoom lens and reduction of focus operation torque are achieved.

Further, since the incident height of the axial ray becomes large on the telephoto side, the influence on the aberration on the telephoto side is large.
13 is a four-piece configuration of concave, convex, convex, convex in order from the object side,
Spherical aberration is diverged by the concave lens, and the occurrence of spherical aberration in the front lens group is suppressed.

The above-mentioned conditional expression is given by f11 / f1 = −2.30.
2, f13 / f1 = 2.009, △ ν11n- △ ν11
p = 29.35, Δν13p−Δν13n = 41.79
It is.

The variator V has a lens arrangement that is concave, convex, concave, convex, concave from the object side. First,
The negative lens closest to the object side has a meniscus shape with a strong concave surface facing the image plane side, thereby effectively correcting distortion at the wide-angle end.

The variation of the chromatic aberration and particularly the chromatic aberration of magnification itself are corrected by the combination of the second and third concaves and convexes. This is because the variator V is composed of five lenses, and the thickness of the entire variator V is increased. Therefore, the more the achromatic position of the variator is on the image plane side, the more the wavelength depends on the variator. The deviation of the position of the point becomes large, and the chromatic aberration of magnification occurs largely. For this reason, as in the configuration example of the embodiment, the achromatic position as the variator V is present on the object side, and the chromatic aberration of magnification is satisfactorily corrected.

Further, by setting the fourth and fifth concave and convex combinations and setting an appropriate refractive index difference between the two, the coma aberration particularly on the telephoto side is corrected. Considering the effects of higher-order aberrations, the positive lens and the negative lens take either the cemented or the separated form.Therefore, if the refractive index difference is small, the frame when the positive lens and the negative lens take the joined form The divergence effect of the aberration is significantly lost.

The compensator C is also made up of two concave and convex components, and diverges spherical aberration and chromatic aberration at the boundary surface.
The occurrence of aberration is suppressed.

The aspherical surface AS1 of the eleventh lens unit F11 is provided on the R1 surface. The aspherical surface of the R1 surface allows an off-axis ray to pass only near the wide-angle end in the entire zoom range, and an on-axis ray on the telephoto side. The difference from the incident height is large, and the off-axis light beam passes only near the wide-angle end in the entire zoom range, and the off-axis luminous flux incident height at the maximum angle of view near the zoom position at the zoom ratio Z ^1/4 Is used effectively, and hw / ht =
3.796, hw / hz = 1.413.

The direction of the aspherical surface of the aspherical surface AS1 is a direction in which the positive power increases as the distance from the optical axis increases, and it is necessary to efficiently correct distortion and spherical aberration up to a high-order region. , Aspherical coefficients B, C, D and E are used. The aspherical amount at this time is 1847 μm at the maximum height of the incident light ray of R1.

The aspherical surface AS2 of the 13th lens unit F13 is provided on the R14 surface. The aspherical surface of the R14 surface allows an on-axis ray to pass only near the telephoto end in the entire zoom range and an off-axis ray on the wide-angle side. The fact that the difference from the incident height is large is effectively used, and hw / ht = 0.743.

The direction of the aspherical surface of the aspherical surface AS2 is a direction in which the positive power becomes weaker as the distance from the optical axis increases, and it is necessary to efficiently correct distortion and spherical aberration up to a high-order region. , Aspherical coefficients B, C, D and E are used. The aspherical amount at this time is 621.1 μm at the maximum height of the incident light ray on R14.

FIGS. 2 to 6 show the spherical aberration, astigmatism, and distortion at each zoom position. Example 2 shown in FIG.
Has a 12x zoom ratio, and the angle of view 2ω at the wide angle end is 90 °
Is over. R1 to R17 are front lens units F. R1 to R8 are an eleventh lens unit F fixed during focusing.
11, which has negative power (refractive power), and R9 to R1
Reference numeral 0 denotes a twelfth lens unit F12 which has a focusing action and moves to the image plane side when focusing from an object at infinity to an object at a close distance,
R11 to R17 are fixed to the thirteenth lens group F during focusing.
13 which has a positive power. R18 to R25 are variators V which move monotonously from the wide (wide-angle end) to the tele (telephoto end) to the image plane side for zooming. R26 to R
Numeral 28 denotes a compensator C having an effect of correcting an image point accompanying zooming, has negative power, and moves to draw a convex arc toward the object side when zooming from wide to tele. SP
(29) is an aperture. R30 to R46 are relay groups R having an image forming function, and R47 to R49 are glass blocks equivalent to color separation prisms.

In the second embodiment, if the lateral magnification of the variator at the wide-angle end of the entire zoom lens system is β2w, β2w =
A power (refractive power) arrangement of −0.342 corresponds to an ultra-wide angle. For these wide-angle and large-aperture lenses, the front lens group first has a large off-axis ray incident height on the wide-angle side, so that the eleventh group F11 having a large effect on aberrations on the wide-angle side is concave, A concave, concave, and convex lens configuration is used, and the concave lens closest to the object side has a meniscus shape with a strong concave surface facing the image plane side, thereby suppressing the occurrence of distortion in the front lens group. I have.

As a focusing method, a twelfth lens group F
By adopting a so-called inner focus method in which the focus movement group 12 is used, aberration fluctuation due to subject distance can be corrected well, and at the same time, effects such as miniaturization of the entire zoom lens and reduction of focus operation torque are achieved.

Further, F3, which has a large influence on aberrations on the telephoto side because the height of incident light on the axial side becomes large on the telephoto side, is composed of four lenses of concave, convex, convex, and convex in order from the object side. The aberration is diverged, and the occurrence of spherical aberration in the front lens group is suppressed.

The above-mentioned conditional expression satisfies f11 / f1 = −1.99.
5, f13 / f1 = 1.743, △ ν11n- △ ν11
p = 28.12, Δν13p−Δν13n = 41.83
It is.

The variator V has a concave, concave, convex and concave configuration. The convex lens diverges spherical aberration, coma and the like, thereby suppressing occurrence of aberrations in the variator.

The compensator C also has a concave and convex configuration, and diverges spherical aberration and chromatic aberration at the boundary surface.
The occurrence of aberration is suppressed.

The aspheric surface AS1 is provided on the R3 surface.
The aspheric surface has an off-axis ray that passes only near the wide-angle end in the entire zoom range, and has a large difference from the incident height of on-axis rays on the telephoto side. A large difference between the maximum angle of view and the incident height of the off-axis light flux near the zoom position at the zoom ratio Z ^1/4 is effectively used, and hw / ht = 1.784. , Hw
/Hz=1.198.

The direction of the aspherical surface is a direction in which the positive power increases as the distance from the optical axis increases, and in order to efficiently correct distortion and spherical aberration up to higher-order regions,
Aspheric coefficients B, C, D, and E are used. The aspherical amount at this time is 105.5 μm at the maximum height of the incident light ray on R3.
It is.

The aspheric surface AS2 applied to the R16 surface is large.
The generated spherical aberration on the telephoto side is corrected. Aspheric
The direction is positive power as the distance from the optical axis increases
In the direction of weakening, efficiently distorting and collecting up to higher-order regions.
To correct for differences and spherical aberration, the aspheric coefficients B, C,
D and E are used. The aspherical amount at this time is R16
Is 260.4 μm at the maximum incident light height. This non-sphere
The surface shape is simultaneously the zoom ratio Z ^1/4Over-distortion
It is a direction to reduce, and the axial ray incident height is large on the telephoto side
Since it is more effective for the lens surface, it is applied to R16. hw /
ht = 0.562.

8 to 12 show the spherical aberration, astigmatism, and distortion at each zoom position.

Embodiment 3 shown in FIG. 13 has a zoom ratio of 27 times, and the angle of view 2ω at the wide angle end exceeds 78 °. R1
R19 is a front lens unit F. R1 to R6 are fixed F1 during focusing and have negative power (refractive power)
R7 to R11 are a twelfth lens unit F12 having a focusing action and moving to the image plane side when focusing from an object at infinity to an object at a close distance, and R12 to R19 are a twelfth lens unit fixed during focusing. Group F13 having positive power.
R20 to R28 are variators V that move monotonously from the wide (wide-angle end) to the telephoto (telephoto end) to the image plane side for zooming.
It is. Reference numerals R29 to R31 denote compensators C having an effect of correcting an image point accompanying zooming, have negative power, and move in a convex arc toward the object side when zooming from wide to tele. SP (32) is an aperture. R33 to R47 are relay groups R having an imaging action, and R48
To R50 are glass blocks equivalent to the color separation prism.

In the third embodiment, if the lateral magnification of the variator at the wide angle end of the entire zoom lens system is β2w, β2w =
A power (refractive power) arrangement of −0.231 corresponds to an ultra-wide angle. In order to increase the angle of view, in the front lens unit, first, the off-axis ray incident height becomes large on the wide angle side, so that the eleventh group F11 having a large influence on the aberration on the wide angle side is concave, concave, convex in order from the object side. With three lens configurations,
The concave lens closest to the object side has a meniscus shape with a strong concave surface facing the image plane side, thereby suppressing the occurrence of distortion in the front lens group.

As a focusing method, a twelfth lens group F
In addition to adopting a so-called inner focus method in which the focus movement group 12 is used, by using a convex, concave, and convex three-element configuration, spherical aberration and chromatic aberration due to subject distance that are difficult to correct with a high-magnification zoom lens. At the same time, the fluctuation is favorably corrected, and at the same time, effects such as miniaturization of the entire zoom lens and reduction of the focus operation torque are achieved.

Further, since the incident height of the axial ray becomes large on the telephoto side, the influence on the aberration on the telephoto side is large.
13 is a four-piece configuration of concave, convex, convex, convex in order from the object side,
Spherical aberration is diverged by the concave lens, and the occurrence of spherical aberration in the front lens group is suppressed.

The above-mentioned conditional expression is f11 / f1 = −1.09
2, f13 / f1 = 1.155, △ ν11n- △ ν11
p = 30.1 and Δν13p−Δν13n = 39.4.

Further, the variator V has a lens arrangement that is concave, convex, concave, convex, concave from the object side. First,
The negative lens closest to the object side has a meniscus shape with a strong concave surface facing the image plane side, thereby effectively correcting distortion at the wide-angle end.

The variation of the chromatic aberration and particularly the chromatic aberration of magnification itself are corrected by the combination of the second and third concave and convex portions. This is because the variator V is composed of five lenses, and the thickness of the entire variator V is increased. Therefore, the more the achromatic position of the variator is on the image plane side, the more the wavelength depends on the variator. The deviation of the position of the point becomes large, and the chromatic aberration of magnification occurs largely. For this reason, as in the configuration example of the embodiment, the achromatic position as the variator V is present on the object side, and the chromatic aberration of magnification is satisfactorily corrected.

Further, the fourth and fifth concave and convex combinations are set, and an appropriate refractive index difference is set between the two to correct coma aberration particularly on the telephoto side. Considering the effects of higher-order aberrations, the positive lens and the negative lens take either the cemented or the separated form.Therefore, if the refractive index difference is small, the frame when the positive lens and the negative lens take the joined form The divergence effect of the aberration is significantly lost.

The compensator C also has a concave and convex configuration, and diverges spherical aberration and chromatic aberration at the boundary surface.
The occurrence of aberration is suppressed.

The aspherical surface AS1 of the eleventh lens unit F11 is provided on the R5 surface. The aspherical surface of the R5 surface allows an off-axis ray to pass only near the wide-angle end in the entire zoom range, and an on-axis ray on the telephoto side. The difference from the incident height is large, and the off-axis light beam passes only near the wide-angle end in the entire zoom range, and the off-axis luminous flux incident height at the maximum angle of view near the zoom position at the zoom ratio Z ^1/4 Is used effectively, and hw / ht =
1.343, hw / hz = 1.057.

The direction of the aspherical surface of the aspherical surface AS1 is a direction in which the positive power increases as the distance from the optical axis increases, and it is necessary to efficiently correct distortion and spherical aberration up to higher-order regions. , Aspherical coefficients B, C, D and E are used. The aspherical amount at this time is −140.3 μm at the maximum height of the incident light ray of R5.

The aspherical surface AS2 of the 13th lens unit F13 is provided on the R18 surface. The aspherical surface of the R18 surface allows an on-axis ray to pass only near the telephoto end in the entire zoom range, and an off-axis ray on the wide-angle side. The fact that the difference from the incident height is large is effectively used, and hw / ht = 0.521.

The direction of the aspherical surface of the aspherical surface AS2 is a direction in which the positive power becomes weaker as the distance from the optical axis increases, and it is necessary to efficiently correct distortion and spherical aberration up to a high-order region. , Aspherical coefficients B, C, D and E are used. The amount of aspherical surface at this time is 501.8 μm at the maximum height of the incident ray on R18.

FIGS. 14 to 18 show the spherical aberration, astigmatism, and distortion at each zoom position.

Embodiment 4 shown in FIG. 19 has a zoom ratio of 27 times, and the angle of view 2ω at the wide angle end exceeds 78 °. R1
R19 is a front lens unit F. R1 to R6 are an eleventh lens unit F11 fixed at the time of focusing and have a negative power (refractive power). R7 to R11 have a focusing effect and an image plane at the time of focusing from an object at infinity to an object at a close distance. The twelfth lens unit F12 moves to the side, and R12 to R19 are a thirteenth lens unit F13 that is fixed at the time of focusing and have a positive power. R20 to R27 are variators V that move monotonously from the wide (wide-angle end) to the tele (telephoto end) to the image plane side for zooming. Reference numerals R28 to R38 denote compensators C having an effect of correcting an image point accompanying zooming, have positive power, and move monotonously to the object side when zooming from wide to tele. SP (39) is an aperture. R40 to R
Reference numeral 55 denotes a relay group R having an image forming function, and R56 to R58 denote glass blocks equivalent to a color separation prism.

In the fourth embodiment, if the lateral magnification of the variator at the wide-angle end of the entire zoom lens system is β2w, β2w =
A power (refractive power) arrangement of -0.206 corresponds to an ultra-wide angle. In order to increase the angle of view, in the front lens unit, first, the off-axis ray incident height becomes large on the wide angle side, so that the eleventh group F11 having a large influence on the aberration on the wide angle side is concave, concave, convex in order from the object side. With three lens configurations,
The concave lens closest to the object side has a meniscus shape or a plano-concave shape with a strong concave surface facing the image surface side, thereby suppressing the occurrence of distortion in the front lens group.

As a focusing method, the twelfth lens group F
In addition to adopting a so-called inner focus method in which the focus movement group 12 is used, by using a convex, concave, and convex three-element configuration, spherical aberration and chromatic aberration due to subject distance that are difficult to correct with a high-magnification zoom lens. At the same time, the fluctuation is favorably corrected, and at the same time, effects such as miniaturization of the entire zoom lens and reduction of the focus operation torque are achieved.

Further, since the incident height of the axial ray becomes large on the telephoto side, the influence on the aberration on the telephoto side is large.
13 is a four-piece structure of convex, concave, convex, convex in order from the object side,
Spherical aberration is diverged by the concave lens, and the occurrence of spherical aberration in the front lens group is suppressed.

The above conditional expression is f11 / f1 = −1.02
9, f13 / f1 = 1.231, △ ν11n- △ ν11
p = 30.1 and Δν13p−Δν13n = 41.49.

The variator V has a symmetrical lens arrangement of concave, concave, convex, concave, concave from the object side. First, the negative lens closest to the object side has a meniscus shape with a strong concave surface facing the image plane side, thereby effectively correcting distortion at the wide-angle end.

The variation of the chromatic aberration and especially the chromatic aberration of magnification itself are corrected by the combination of the second and third concave and convex portions. This is because the variator V is composed of five lenses, and the thickness of the entire variator V is increased. Therefore, the more the achromatic position of the variator is on the image plane side, the more the wavelength depends on the variator. The deviation of the position of the point becomes large, and the chromatic aberration of magnification occurs largely. For this reason, as in the configuration example of the embodiment, the achromatic position as the variator V is present on the object side, and the chromatic aberration of magnification is satisfactorily corrected. The fourth and fifth concave lenses suppress the occurrence of negative spherical aberration at the telephoto end.

In the compensator C, the third lens unit has the positive refractive power, and the power arrangement as in this embodiment has the third lens unit.
Since the incident height of the on-axis ray in the group becomes large, it becomes difficult to correct the aberration. Therefore, convex, convex, concave, concave, convex, convex, and symmetrical lens arrangement are used, and spherical aberration, coma, and chromatic aberration are diverged by setting a plurality of positions where the aberrations due to the convex and concave are canceled out, thereby generating aberrations. Has been suppressed.

The aspheric surface AS1 of the eleventh lens unit F11 is provided on the R1 surface. The aspheric surface of the R1 surface allows an off-axis ray to pass only near the wide-angle end in the entire zoom range, and an on-axis ray on the telephoto side. The difference from the incident height is large, and the off-axis light beam passes only near the wide-angle end in the entire zoom range, and the off-axis luminous flux incident height at the maximum angle of view near the zoom position at the zoom ratio Z ^1/4 Is used effectively, and hw / ht =
2.169, hw / hz = 1.384.

The direction of the aspherical surface of the aspherical surface AS1 is a direction in which the positive power increases as the distance from the optical axis increases, and it is necessary to efficiently correct distortion and spherical aberration up to higher-order regions. , Aspherical coefficients B, C, D and E are used. The aspherical amount at this time is −1323.8 μm at the maximum height of the incident light ray on R1.

The aspheric surface AS2 of the 13th lens unit F13 is provided on the R18 surface. The aspheric surface of the R18 surface allows an on-axis ray to pass only near the telephoto end in the entire zoom range, and an off-axis ray on the wide-angle side. The fact that the difference from the incident height is large is effectively used, and hw / ht = 0.504.

The direction of the aspherical surface of the aspherical surface AS2 is a direction in which the positive power becomes weaker as the distance from the optical axis increases, and it is necessary to efficiently correct distortion and spherical aberration up to a high-order region. , Aspherical coefficients B, C, D and E are used. The aspherical amount at this time is 277.4 μm at the maximum height of the incident light ray on R18.

FIGS. 20 to 24 show the spherical aberration, astigmatism, and distortion at each zoom position.

Next, numerical examples of the present invention 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 vi are the i-th lens d in order from the object side. The refractive index and Abbe number of the glass with respect to the line. In the numerical examples, the last three lens surfaces are glass blocks such as a face plate and a filter.

The aspherical shape has an X axis in the optical axis direction, an H axis in a direction perpendicular to the optical axis, a positive traveling direction of light, R represents a paraxial radius of curvature, and K, B, C, D, and E represent aspherical shapes. Assuming spherical coefficients,

[0132]

(Equation 1)

This is represented by the following equation. “D-0x” means “10 ^−x ”.

[0134]

[Outside 1]

[0135]

[Table 1]

[0136]

[Outside 2]

[0137]

[Outside 3]

[0138]

[Table 2]

[0139]

[Outside 4]

[0140]

[Outside 5]

[0141]

[Table 3]

[0142]

[Outside 6]

[0143]

[Outside 7]

[0144]

[Table 4]

[0145]

[Outside 8]

[0146]

As described above, according to the present invention, the present invention relates to a so-called four-unit zoom lens, in which the refractive power, the F-number, etc. of each lens unit are appropriately set, and at least two lens surfaces are aspherical. Reduces the fluctuation of aberrations associated with zooming, and corrects distortion especially on the wide-angle side and spherical aberration on the telephoto side, achieving a zoom lens with high optical performance over the entire zoom range. can do.

In addition, according to the present invention, the F number at the wide angle end is about 1.5 to 1.8, and the ultra wide angle (wide angle end angle of view 2ω = 78)
(Approximately {95}), a zoom lens having a high zoom ratio with a large aperture ratio of approximately 10 to 27 can be achieved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a lens at a wide angle end according to Numerical Embodiment 1 of the present invention.

FIG. 2 is an aberration diagram at a focal length f = 5.00 of the first embodiment of the present invention.

FIG. 3 is an aberration diagram of a focal length f = 8.89 according to the first embodiment of the present invention.

FIG. 4 is an aberration diagram of the focal length f = 12.50 according to the first embodiment of the present invention.

FIG. 5 is an aberration diagram of a focal length f = 37.50 according to the first embodiment of the present invention.

FIG. 6 is an aberration diagram of a focal length f = 50.00 according to the first embodiment of the present invention.

FIG. 7 is a sectional view of a lens at a wide-angle end according to a second numerical embodiment of the present invention.

FIG. 8 is an aberration diagram at a focal length of f = 5.50 according to the second embodiment of the present invention.

FIG. 9 is an aberration diagram of a focal length f = 10.24 according to the second embodiment of the present invention.

FIG. 10 shows a focal length f = 22.00 of Embodiment 2 of the present invention.
Aberration diagram of

FIG. 11 shows a focal length f = 46.75 according to the second embodiment of the present invention.
Aberration diagram of

FIG. 12 shows a focal length f = 66.00 according to the second embodiment of the present invention.
Aberration diagram of

FIG. 13 is a sectional view of a lens at a wide angle end according to Numerical Embodiment 3 of the present invention.

FIG. 14 is an aberration diagram of a focal length f = 6.70 according to the third embodiment of the present invention.

FIG. 15 shows a focal length f = 15.27 according to the third embodiment of the present invention.
Aberration diagram of

FIG. 16 shows a focal length f = 33.50 according to the third embodiment of the present invention.
Aberration diagram of

FIG. 17 shows a focal length f = 107.2 according to the third embodiment of the present invention.
Aberration diagram of

FIG. 18 shows a focal length f = 180.9 of Embodiment 3 of the present invention.
Aberration diagram of

FIG. 19 is a sectional view of a lens at a wide angle end according to Numerical Example 4 of the present invention.

FIG. 20 is an aberration diagram at a focal length of f = 6.70 according to the fourth embodiment of the present invention.

FIG. 21 shows a focal length f = 15.27 according to the fourth embodiment of the present invention.
Aberration diagram of

FIG. 22 is a focal length f = 28.66 of Embodiment 4 of the present invention.
Aberration diagram of

FIG. 23 is a focal length f = 67.55 of Embodiment 4 of the present invention.
Aberration diagram of

FIG. 24 shows a focal length f = 180.9 of Embodiment 4 of the present invention.
Aberration diagram of

FIG. 25 is an optical path diagram of a part of a wide-angle zoom lens.

FIG. 26 is an optical path diagram of a part of a wide-angle zoom lens.

FIG. 27 is an optical path diagram of a part of a wide-angle zoom lens.

FIG. 28 is an optical path diagram of a part of a wide-angle zoom lens;

FIG. 29 is an explanatory diagram of aberration fluctuations due to zooming of the zoom lens.

FIG. 30 is an explanatory diagram of aberration fluctuations due to zooming of the zoom lens.

[Explanation of symbols]

 F Front lens group (focus group) F1 11th group F2 12th group F3 13th group V 2nd group (variator) C 3rd group (compensator) R 4th group (relay group) P Glass block SP Aperture e e-line S sagittal image plane M meridional image plane

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Seiji Fukami 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. (reference) 2H087 KA02 KA03 MA18 PA15 PA16 PB20 QA02 QA06 QA07 QA17 QA22 QA25 QA26 QA32 QA34 QA42 QA45 RA05 RA12 RA32 RA41 RA43 SA23 SA27 SA29 SA30 SA32 SA63 SA64 SA72 SA75 SB01 SB15 SB16 SB23 SB27 SB31

Claims (8)

[Claims] 1. A first lens unit having a fixed positive refractive power, a second lens unit having a negative refractive power for zooming, and a positive or negative lens for correcting an image plane variation caused by zooming during zooming in order from the object side. A third lens unit having a negative refractive power and a fourth lens unit having a fixed positive refractive power, wherein the first lens unit has a focusing negative action with a twelfth lens unit having a fixed negative refractive power; 13th of positive refractive power fixed at the time of focusing with the group
A zoom lens comprising: a lens unit; and the eleventh unit and the thirteenth unit each have an aspheric surface. 2. The eleventh lens unit has a maximum incident height of on-axis light flux in the eleventh lens unit, ht, an incident height of an off-axis light flux having a maximum angle of view at a wide-angle end, hw, and a zoom position at a zoom ratio Z ^1/4 . Where hz is the incident height of the off-axis light beam having the maximum angle of view of 1.30 <h
At least one lens surface satisfying w / ht and 1.05 <hw / hz is provided with an aspherical surface AS1, and the thirteenth unit has a maximum incident height of an axial light flux in the thirteenth unit, ht, and a wide angle. When the height of the off-axis light beam having the maximum angle of view at the end is hw and the height of the off-axis light beam having the maximum angle of view at the zoom position at the zoom ratio Z ^1/4 is hz, 0.75> hw / ht is satisfied. 2. The zoom lens according to claim 1, wherein the at least one lens surface has an aspheric surface AS2. 3. The zoom ratio is Z, and the focal length of each of the first, eleventh, and thirteenth groups is f1, f11, and f1, respectively.
3. When the lateral magnification of the second lens unit at the wide-angle end is β2w, Z> 10−0.42 <β2w <−0.18−2.45 <f11 / f1 <−0.98 1.05 <f13 2. The zoom lens according to claim 1, wherein a condition of /f1<2.10 is satisfied. 4. When the aspheric surface AS1 is applied to a positive refracting surface, it has a shape in which the positive refractive power becomes stronger toward the periphery of the lens, and when applied to a negative refracting surface, the periphery of the lens becomes peripheral. The negative refractive power becomes weaker as going to the portion, and the aspherical amounts at 100%, 90%, and 70% of the effective lens diameter of the aspherical surface AS1 are を 1 (10), △ 1 (9), △ 1
Assuming (7), 1.07 × 10 ⁻³ <| △ 1 (10) / f1 | <7.20
× 10 ^-2 1.06 × 10 ^-3 <| △ 1 (9) / f1 | <4.90
× 10 ^-2 6.10 × 10 ^-4 <| △ 1 (7) / f1 | <1.95
3. The zoom lens according to claim ^{2, wherein} a condition of × 10 ⁻² is satisfied. 5. The aspheric surface AS2 has a shape in which the positive refractive power becomes weaker toward the lens peripheral portion when applied to the positive refractive surface, and the lens peripheral portion when applied to the negative refractive surface. The negative refractive power becomes stronger as going to the portion, and the aspherical amounts at 100%, 90%, and 70% of the effective lens diameter of the aspherical surface AS2 are △ 2 (10), △ 2 (9), △ 2
Assuming (7), 2.15 × 10 ⁻³ <| △ 2 (10) / f1 | <2.45
× 10 ^-2 1.35 × 10 ^-3 <| △ 2 (9) / f1 | <1.60
× 10 ^-2 4.85 × 10 ^-4 <| △ 2 (7) / f1 | <5.60
The zoom lens according to claim 2, wherein a condition of ^10-3 is satisfied. 6. The eleventh lens group is at least 2 mm from the object side.
The negative lens closest to the object side has a meniscus shape or a plano-concave shape with a strong concave surface facing the image plane, and the Abbe number of the material of the at least two negative lenses. 2. The zoom lens according to claim 1, wherein, when an average is Δν11n and an Abbe number of the material of the positive lens is Δν11p, a condition of Δν11n−Δν11p> 26.5 is satisfied. 3. 7. The twelfth lens unit has at least one positive lens that moves toward the image plane when focusing from an object at infinity to an object at a close distance, and has a convex surface facing the image plane. The zoom lens according to claim 1, wherein: 8. The thirteenth group includes at least one negative lens and three positive lenses, wherein the Abbe number of the material of the negative lens is Δν13n, and the average of the Abbe numbers of the materials of the at least three positive lenses is 2. The zoom lens according to claim 1, wherein when Δν13p is satisfied, a condition of Δν13p−Δν13n> 37.4 is satisfied. 3.