JP2002072087A - Zoom lens - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To be suitable for a video camera, an electronic still camera, etc. using a solid-state imaging device, etc.
A zoom lens with an angle of view of 60 ° at the wide-angle end and excellent imaging performance. The zoom lens includes at least a first positive lens group, a second negative lens group, and a third positive lens group in order from the object side. First
In a zoom lens in which the lens group G1 is fixed and the distance between the second lens group G2 and the third lens group G3 is reduced, the first lens group G1 includes one positive lens, and the second lens group G2 includes at least one negative lens and at least one positive lens, and the third lens group G3 includes a stop S, at least one positive lens, and at least one negative lens. (1)
(2) is satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens suitable for a small camera using a solid-state imaging device such as a CCD.
In particular, the present invention relates to a zoom lens having a zoom ratio of 2.5 times or more and an angle of view of 60 ° or more at a wide angle end.

[0002]

2. Description of the Related Art Conventionally, a zoom lens suitable for a solid-state image sensor has been known in Japanese Patent Application Laid-Open No. H11-23967. The overall length tends to be long, and it is difficult to correct distortion at the wide-angle end. On the other hand, the convex leading type has a relatively large front lens diameter and tends to be complicated in overall length, but has an advantage in that the overall length is relatively short and is advantageous in correcting distortion at the wide-angle end. Japanese Patent Application Laid-Open Nos. Hei 6-27377 and Hei 8
A lens described in JP-A-278444 is known.

[0003]

However, in the embodiments of JP-A-6-27377 and JP-A-8-278444, the overall length is still long and the thickness of each group tends to be large, which is disadvantageous for miniaturization. Met.

Therefore, the present invention is suitable for a video camera, an electronic still camera, etc. using a solid-state imaging device, etc., and is compact, has a zoom ratio of about 3 times, has an angle of view of 60 ° at the wide angle end, and is excellent. It is intended to provide a zoom lens having improved imaging performance.

[0005]

In order to solve the above problems, the present invention provides at least a positive first order from the object side.
A first lens group fixed at zooming from the wide-angle end to the telephoto end; and a second lens group and a third lens group. In a zoom lens in which the distance between the groups is reduced, the first lens group includes one positive lens, the second lens group includes at least one negative lens and at least one positive lens, and The three-lens group includes a stop, at least one positive lens, and at least one negative lens, and further provides a zoom lens that satisfies the following conditional expression.

3.9 <f1 / f3 <43 (1) 6.3 <TL / fw <7.9 (2) where f1: focal length of the first lens group, f3: focal length of the third lens group, TL: all Overall length of system (distance from first surface to image plane), fw: focal length of whole system at wide-angle end.

[0007]

Embodiments of the present invention will be described below. 1, 5, 9, 13, 17, 21, 25, 29, 33, 37, 41, 4
5 and FIG. 49 show a sectional view of the lens of the present invention. As can be seen from the figure, the present invention sequentially includes, from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a positive refractive power including a stop S. And a third lens group G3.

The first lens unit having the positive refractive power disposed closest to the object has a function of mainly correcting negative distortion generated by the second lens unit, and has a positive convergence function.
It has the function of lowering the height of light rays incident parallel to the optical axis after the second lens group, and this action can reduce the size of the entire system.

The second lens group having a negative refractive power changes the focal length by moving from the object side to the image side, and moves from the wide-angle end to the telephoto end by moving nonlinearly with respect to the third lens group. When zooming in to, it is responsible for keeping the focal length constant.

The third lens group having a positive refractive power has a role of changing the focal length of the entire system by moving from the image side to the object side when zooming from the wide-angle end to the telephoto end.

According to the present invention, in order to reduce the size of the entire system,
Recognizing that miniaturization of the group is important, the first lens group having a positive refracting power is composed of one positive lens. As a result, an increase in the front lens diameter, which is a problem with a wide-angle positive-lens leading-type zoom lens, is caused. Was minimized, and various aberrations such as distortion were successfully corrected while miniaturizing the entire system.

Here, the conditional expression (1) is a condition for forming the positive first lens unit by a single lens, and includes the focal length of the positive first lens unit and the positive third lens unit. This defines the ratio of the focal length. If the upper limit of conditional expression (1) is exceeded, the refractive power of the positive first lens group is extremely weak.
It is difficult to correct negative distortion at the wide-angle end, and it is difficult to reduce the overall length because the configuration approaches a negative / positive two-unit zoom lens. Conversely, if the lower limit is exceeded, the positive first lens group may have a short focal length and the positive third lens group may have a long focal length. However, the positive first lens group has a short focal length. In this case, since the first lens group is composed of a positive single lens, it is difficult to correct the chromatic aberration generated here, and the first lens group cannot be composed of a single lens. On the other hand, if the focal length of the positive third lens group is long, it is not preferable because the whole system becomes large.

Conditional expression (2) is a condition for miniaturization,
The relationship between the focal length fw at the wide-angle end of the entire lens system and the overall length is defined. If the upper limit of this expression is exceeded, the overall length becomes large and it is difficult to reduce the size, or the angle of view at the wide-angle end becomes narrow and the zoom ratio becomes small. Conversely, when the value exceeds the lower limit of this equation, it is advantageous for miniaturization of the entire system, but it is not preferable because aberration correction is difficult when the zoom ratio is increased.

The aperture is preferably disposed in the third lens group in order to correct various aberrations in a well-balanced manner, and more preferably, is disposed on the most object side of the third lens group.

By adopting the above configuration, a small zoom lens with good correction of various aberrations can be obtained. However, in order to achieve high zoom ratio and miniaturization while correcting various aberrations satisfactorily. It is desirable that the present invention satisfies the conditional expression (3).

It is difficult to correct the Petzval sum even if the upper limit or the lower limit of conditional expression (3) is exceeded. If the upper limit is exceeded, the focal length of the third lens unit is long, so that the zoom It is advantageous to increase the ratio, but it is not preferable because the overall length becomes long. Alternatively, since the refractive power of the second lens group is excessive, it is difficult to correct various aberrations. Conversely, if the lower limit is exceeded, the focal length of the second lens is long and the focal length of the third lens group is short, which is advantageous for correcting various aberrations. It is difficult to secure a high zoom ratio because the distance between groups is close.

It is desirable that the present invention satisfies the conditional expression (4) in order to reduce the size while favorably correcting various aberrations. If the upper limit is exceeded, the thickness of the third lens group is too large, which is against miniaturization. Conversely, if the lower limit is exceeded, the thickness of the third lens group is too thin, and it is particularly difficult to correct coma.

In order to obtain good aberration correction while miniaturizing the zoom lens, it is desirable that the present invention satisfies the conditional expression (5). If the upper limit is exceeded, it is difficult to reduce the size of the entire system. Conversely, if the lower limit is exceeded, it becomes difficult to satisfactorily correct fluctuations in chromatic aberration and spherical aberration during zooming. Therefore, it is not preferable.

It is preferable that the lens according to the present invention further has a positive fourth lens group on the image side of the positive third lens group. The positive fourth lens group has the function of controlling the exit pupil of the entire system, and can efficiently guide light to a solid-state imaging device such as a CCD disposed on the image plane. In addition, the fourth lens group also functions as a reduction optical system, and is effective in favorably correcting aberrations of the entire system. Also, the fourth
The lens group includes a filter for cutting a spatial frequency equal to or higher than the limit resolution of the solid-state imaging device, that is, a low-pass filter P1, and a cover glass P for protecting the solid-state imaging device.
2 inclusive.

When a fourth lens group is provided, it is desirable that the fourth lens group satisfies the conditional expression (6). Exceeding the upper limit or exceeding the lower limit is not preferable because the exit pupil position of the entire system does not become an appropriate position. If the upper limit is exceeded, the refracting power of the fourth lens group is excessively large, which is advantageous for aberration correction, but undesirably leads to an increase in the size of the entire system. Conversely, if the value exceeds the lower limit, the refractive power of the fourth lens group is too small, which is not preferable for good aberration correction.

By the way, in the field of silver halide compact cameras, the distance between the lens groups during storage is reduced as much as possible.
In actual use, a retractable type having a lens barrel mechanism that expands to a predetermined lens interval is mainly used. To reduce the size of the camera by utilizing this collapsible mechanism, it is more effective to reduce the total thickness of each lens group than to shorten the entire length of the lens. Here, "thickness of each lens group"
Means "the distance on the optical axis from the most object-side end face of each lens group to the most image-side end face of each lens group". When the stop is provided on the end face of the lens group, the distance from the stop surface is shown. In the case of the fourth lens group, a lens, the low-pass filter P1, and the cover glass P2
Is the distance on the optical axis from the end surface closest to the object side to the end surface closest to the image side. The “sum of the thickness of each lens group” is the sum of the “thickness of each lens group”.
It does not include the air spacing between each lens group.

Conditional expression (7) is a condition that should be satisfied in order to reduce the size of the lens in such a retractable camera. If the upper limit is exceeded, it is not preferable because miniaturization during collapsing cannot be achieved. Conversely, if the lower limit is exceeded, the thickness of each lens group is too thin, and it is difficult to correct aberration fluctuations during zooming.

According to the constitution of the present invention, the following Examples 1 to
As shown in the eighth and twelfth embodiments, sufficient optical performance can be achieved even if each surface is made up of only a flat surface or a spherical surface without using a so-called aspherical surface. In this case, processing is easy and it can be manufactured at low cost.

As shown in the following Examples 9 to 11 and Example 13, the third lens group has a stop disposed closest to the object side and at least one surface of the lens closest to the image side. Is preferably an aspherical surface. An aspherical surface is preferable because the further away from the stop, the better the correction of coma (outer coma) and the lower the processing accuracy, the better. On the other hand, the closer to the stop, the better the spherical aberration, especially the spherical aberration at the telephoto end. Therefore, it is preferable to dispose it on at least one surface of the lens closest to the image as described above in view of the balance between the two.

[0025]

EXAMPLES Examples 1 to 13 of the present invention will be described below. In each embodiment, during zooming from the wide-angle end to the telephoto end, the distance between the second lens group and the third lens group is reduced, and the distance between the third lens group and the image plane is increased. And the third lens group move, and the first and fourth lens groups are fixed.

In the first embodiment, as shown in FIG. 1, the first lens group G1 comprises one biconvex lens, and the second lens group G2
Has a negative refractive power as a whole, and includes a negative meniscus lens having a convex surface facing the object side and a cemented lens of a biconcave lens and a biconvex lens. The third lens group G3 has a positive refractive power as a whole. It has power and consists of a biconvex lens, a cemented lens of a biconvex lens and a biconcave lens, and four biconvex lenses.
The fourth lens group G4 includes one biconvex lens, the low-pass filter P1, and the cover glass P2.
The stop is arranged on the object side in the third lens group and moves together. All surfaces are comprised of flat or spherical surfaces. FIGS. 2 to 4 show aberration diagrams of the first embodiment at the wide-angle end, the intermediate focal length, and the telephoto end, respectively, when focusing on an object point at infinity.

In the second embodiment, as shown in FIG. 5, the first lens group G1 comprises one biconvex lens, and the second lens group G2
Has a negative refractive power as a whole, and includes a negative meniscus lens having a convex surface facing the object side and a cemented lens of a biconcave lens and a biconvex lens. The third lens group G3 has a positive refractive power as a whole. It has power and consists of a biconvex lens, a cemented lens of a biconvex lens and a biconcave lens, and four biconvex lenses.
The fourth lens group G4 includes one biconvex lens, the low-pass filter P1, and the cover glass P2.
The stop is arranged on the object side in the third lens group and moves together. All surfaces are comprised of flat or spherical surfaces. The aberration of the second embodiment is substantially the same as that of the first embodiment and is well corrected.
The wide-angle end, the intermediate focal length, and the
6 to 8 show aberration diagrams at the telephoto end, respectively.

In the third embodiment, as shown in FIG. 9, the first lens group G1 comprises one biconvex lens, and the second lens group G2
Has a negative refractive power as a whole, and includes a negative meniscus lens having a convex surface facing the object side and a cemented lens of a biconcave lens and a biconvex lens. The third lens group G3 has a positive refractive power as a whole. It has power and consists of a biconvex lens, a cemented lens of a biconvex lens and a biconcave lens, and four biconvex lenses.
The fourth lens group G4 includes one biconvex lens, the low-pass filter P1, and the cover glass P2.
The stop is arranged on the object side in the third lens group and moves together. All surfaces are comprised of flat or spherical surfaces. The aberration of the third embodiment is substantially the same as that of the first embodiment and is well corrected.
The wide-angle end, the intermediate focal length, and the
10 to 12 show aberration diagrams at the telephoto end.

In the fourth embodiment, as shown in FIG. 13, the first lens group G1 is composed of one biconvex lens, and the second lens group G1.
2 has a negative meniscus lens having a negative refractive power as a whole and having a convex surface facing the object side, and a cemented lens of a biconcave lens and a biconvex lens, and the third lens group G3 has a positive The fourth lens group G4 has one biconvex lens, the low-pass filter P1, and the cover glass P2. The fourth lens group G4 has a biconvex lens, a biconvex lens, a cemented lens of the biconvex lens and the biconcave lens, and a biconvex lens. It is composed of The stop is arranged on the object side in the third lens group and moves together. All surfaces are comprised of flat or spherical surfaces. Example 4
Is substantially the same as that of the first embodiment and is well corrected. 14 to 16 show aberration diagrams at the wide-angle end, at an intermediate focal length, and at a telephoto end, respectively, in Example 4 upon focusing on an object point at infinity.

In the fifth embodiment, as shown in FIG. 17, the first lens group G1 comprises one biconvex lens, and the second lens group G
2 has a negative meniscus lens having a negative refractive power as a whole and having a convex surface facing the object side, and a cemented lens of a biconcave lens and a biconvex lens, and the third lens group G3 has a positive The fourth lens group G4 has one biconvex lens, the low-pass filter P1, and the cover glass P2. The fourth lens group G4 has a biconvex lens, a biconvex lens, a cemented lens of the biconvex lens and the biconcave lens, and a biconvex lens. It is composed of The stop is arranged on the object side in the third lens group and moves together. All surfaces are comprised of flat or spherical surfaces. Example 5
Is substantially the same as that of the first embodiment and is well corrected. 18 to 20 show aberration diagrams at the wide-angle end, an intermediate focal length, and a telephoto end of the fifth embodiment when focused on an object point at infinity.

In the sixth embodiment, as shown in FIG. 21, the first lens group G1 is composed of one biconvex lens, and the second lens group G1.
2 has a negative meniscus lens having a negative refractive power as a whole and having a convex surface facing the object side, and a cemented lens of a biconcave lens and a biconvex lens, and the third lens group G3 has a positive The fourth lens group G4 has a refractive power and includes a biconvex lens, a cemented lens of a biconvex lens and a biconcave lens, and a positive meniscus lens having a convex surface facing the object side. The fourth lens group G4 has a positive lens having a convex surface facing the object side. It comprises one meniscus lens, the low-pass filter P1, and the cover glass P2. The stop is arranged on the object side in the third lens group and moves together. All surfaces are comprised of flat or spherical surfaces. The aberration of the sixth embodiment is substantially the same as that of the first embodiment and is well corrected. FIGS. 22 to 24 show aberration diagrams at the wide-angle end, an intermediate focal length, and a telephoto end when focusing on an object point at infinity according to the sixth embodiment.

In the seventh embodiment, as shown in FIG. 25, the first lens group G1 is composed of one biconvex lens, and the second lens group G1.
2 has a negative meniscus lens having a negative refractive power as a whole and having a convex surface facing the object side, and a cemented lens of a biconcave lens and a biconvex lens, and the third lens group G3 has a positive The fourth lens group G4 includes one biconvex lens, one biconvex lens, and one low-pass lens. The fourth lens group G4 includes a biconvex lens, a cemented lens of a biconvex lens and a biconcave lens, and a positive meniscus lens having a convex surface facing the object side. It is composed of a filter P1 and the cover glass P2. The stop is arranged on the object side in the third lens group and moves together. All surfaces are comprised of flat or spherical surfaces. The aberration of the seventh embodiment is substantially the same as that of the first embodiment and is well corrected. 26 to 28 show aberration diagrams at the wide-angle end, an intermediate focal length, and a telephoto end of the seventh embodiment when focused on an object point at infinity, respectively.

In the eighth embodiment, as shown in FIG. 29, the first lens group G1 comprises one positive meniscus lens having a convex surface facing the object side, and the second lens group G2 has a negative refractive power as a whole. A third lens group G3 comprising: a negative meniscus lens having a convex surface facing the object side; and a cemented lens of a biconcave lens and a positive meniscus lens having a convex surface facing the object side.
Has a positive refractive power as a whole, and is composed of a biconvex lens, a cemented lens of a biconvex lens and a biconcave lens, and a positive meniscus lens having a convex surface facing the object side. The fourth lens group G4 is a biconvex lens. One sheet and the low-pass filter P1
And the cover glass P2. Aperture is 3rd
It is arranged on the object side in the lens group and moves together. All surfaces are comprised of flat or spherical surfaces. The aberration of the eighth embodiment is substantially the same as that of the first embodiment and is well corrected. FIGS. 30 to 32 show aberration diagrams at the wide-angle end, an intermediate focal length, and a telephoto end of the eighth embodiment when focused on an object point at infinity, respectively.

In the ninth embodiment, as shown in FIG. 33, the first lens group G1 is composed of one biconvex lens, and the second lens group G1.
Numeral 2 has a negative refractive power as a whole, and includes three biconcave lenses and a cemented lens of a biconcave lens and a biconvex lens. The third lens group G3 has a positive refractive power as a whole and has a biconvex lens. , A cemented lens of a biconvex lens and a biconcave lens, and a biconvex lens, and the object-side surface of the lens closest to the image is aspheric. The fourth lens group G4 includes one biconvex lens, the low-pass filter P1, and the cover glass P2.
It is composed of The stop is arranged on the object side in the third lens group and moves together. The aberration of the ninth embodiment is substantially the same as that of the first embodiment and is well corrected. FIGS. 34 to 36 show aberration diagrams at the wide-angle end, an intermediate focal length, and a telephoto end of the ninth embodiment when focused on an object point at infinity, respectively.

In the tenth embodiment, as shown in FIG.
The second lens group G2 includes a negative meniscus lens having a negative refractive power as a whole and having a convex surface facing the object side, and a cemented lens of a biconcave lens and a biconvex lens. The third lens group G3 has four lenses: a biconvex lens, a cemented lens of a biconvex lens and a biconcave lens, and a positive meniscus lens having a convex surface facing the object side. The object-side surface of the lens closest to the image is an aspheric surface. The fourth lens group G4 includes one biconvex lens, the low-pass filter P1, and the cover glass P2. The stop is arranged on the object side in the third lens group and moves together. The aberration of the tenth embodiment is substantially the same as that of the first embodiment and is well corrected. Example 10
38 to 40 show aberration diagrams at the wide-angle end, at the intermediate focal length, and at the telephoto end, respectively, when focusing on an object point at infinity.

In the eleventh embodiment, as shown in FIG.
The second lens group G2 includes a negative meniscus lens having a negative refractive power as a whole and having a convex surface facing the object side, and a cemented lens of a biconcave lens and a biconvex lens. The third lens group G3 has four lenses: a biconvex lens, a cemented lens of a biconvex lens and a biconcave lens, and a positive meniscus lens having a convex surface facing the object side. The object-side surface of the lens closest to the image is an aspheric surface. The fourth lens group G4 includes one biconvex lens, the low-pass filter P1, and the cover glass P2. The stop is arranged on the object side in the third lens group and moves together. The aberration of the eleventh embodiment is substantially the same as that of the first embodiment and is well corrected. Example 11
42 to 44 show aberration diagrams at the wide-angle end, at the intermediate focal length, and at the telephoto end, respectively, when focusing on an object point at infinity.

In the twelfth embodiment, as shown in FIG.
The second lens group G2 includes a negative meniscus lens having a negative refractive power as a whole and having a convex surface facing the object side, and a cemented lens of a biconcave lens and a biconvex lens. The third lens group G3 has a positive refractive power as a whole, and has a biconvex lens, a cemented lens of a biconvex lens and a biconcave lens, and a cemented lens of a positive meniscus lens having a convex surface facing the object side and a biconvex lens The fourth lens group G4 includes one biconvex lens, the low-pass filter P1, and the cover glass P2. The stop is arranged on the object side in the third lens group and moves together. All surfaces are comprised of flat or spherical surfaces. The aberration of the twelfth embodiment is substantially the same as that of the first embodiment and is well corrected. 46 to 48 show aberration diagrams of the twelfth embodiment at the wide-angle end, an intermediate focal length, and a telephoto end when focused on an object point at infinity, respectively.

In the thirteenth embodiment, as shown in FIG.
The second lens group G2 includes a negative meniscus lens having a negative refractive power as a whole and having a convex surface facing the object side, and a cemented lens of a biconcave lens and a biconvex lens. The third lens group G3 has a positive refractive power as a whole, and has a biconvex lens, a cemented lens of two meniscus lenses having a convex surface facing the object side, and a positive lens having a convex surface facing the object side. It is composed of four meniscus lenses, and the object-side surface of the lens closest to the image is an aspheric surface. The fourth lens group G4 includes one biconvex lens, the low-pass filter P1, and the cover glass P2. The stop is arranged on the object side in the third lens group and moves together.
The aberration of the thirteenth embodiment is substantially the same as that of the first embodiment and is well corrected. The wide-angle end at the time of focusing on an object point at infinity in Example 13,
The aberration diagrams at the intermediate focal length and the telephoto end are shown in FIGS.
Shown in

Tables 1 to 13 below show values of specifications of the first to thirteenth embodiments, respectively.

In the [Overall Specifications], f represents the focal length, Bf represents the back focus, FNO represents the F number, and 2ω represents the angle of view (unit: degree (°)). The values separated by are shown at the wide-angle end, the intermediate focal length, and the telephoto end in order from the left.

In [lens specifications], the first column is the number of the lens surface from the object side, the second column r is the radius of curvature of the lens surface, the third column d is the lens surface interval, and the fourth column ν is the Abbe number. , The fifth column n represents the refractive index for the d-line (λ = 587.6 nm), and the refractive index of air, 1.000000, is omitted.

[Aspherical surface data]
The coordinate in the optical axis direction is x, the coordinate in the direction perpendicular to the optical axis is y, the reference radius of curvature is r, the conic constant is K, and the nth order aspheric coefficient is Cn, and is represented by the following equation.

[0043]

[Number 1] ^{x = (y 2 / r)} / [1+ [1-K (y 2 / r 2)] 1/2] + C2 * y 2 + C4 * y 4 +
C6 * y ⁶ + C8 * y ⁸ + C10 * y ^{10 In the} formula, * indicates a product. In the numerical values of the aspheric coefficients in the table, “E-6” and the like indicate “× 10 ⁻⁶ ” and the like.

The [zooming data] shows the values of the focal length and the variable interval in each state of the wide-angle end, the intermediate focal length, and the telephoto end.

The unit of the focal length f, the radius of curvature r, the surface distance d and other lengths described in all of the following specification values are generally "mm", but the optical system is proportionally enlarged. Or, even if proportionally reduced, equivalent optical performance can be obtained,
However, it is not limited to this.

[0046]

[Table 1]

[0047]

[Table 2]

[0048]

[Table 3]

[0049]

[Table 4]

[0050]

[Table 5]

[0051]

[Table 6]

[0052]

[Table 7]

[0053]

[Table 8]

[0054]

[Table 9]

[0055]

[Table 10]

[0056]

[Table 11]

[0057]

[Table 12]

[0058]

[Table 13] The numerical values corresponding to the conditions of each embodiment are shown below.

[0059]

[Table 14] [Conditional values] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 (1) f1 / f3 5.64 5.64 7.60 7.86 7.45 8.00 (2) f2 / f3 -1.07 -1.07- 1.00 -1.03 -1.05 -1.07 (3) f3 / f4 0.64 0.64 0.57 0.55 0.58 0.64 (4) S3 / f3 0.60 0.60 0.89 0.88 0.86 0.72 (5) S2 / fw 0.96 0.96 0.99 0.98 0.99 0.96 (6) TL / fw 6.48 6.48 7.28 6.70 7.26 6.41 (7) Σd / fw 3.00 3.00 3.60 3.54 3.59 3.12 Example 7 Example 8 Example 9 Example 10 Example 11 Example 12 Example 13 (1) f1 / f3 7.04 8.09 5.99 4.93 4.93 5.33 4.93 (2) f2 / f3 -1.07 -1.03 -1.07 -1.07 -1.07 -1.00 -1.07 (3) f3 / f4 0.65 0.51 0.64 0.64 0.64 0.65 0.64 (4) S3 / f3 0.65 0.97 0.62 0.56 0.55 0.71 0.56 (5) S2 / fw 0.96 1.11 0.96 0.98 0.98 1.03 0.98 (6) TL / fw 6.39 6.52 6.37 6.71 6.53 7.17 6.66 (7) Σd / fw 3.05 4.05 3.03 3.04 2.93 3.43 3.03 Focusing is possible by moving the entire lens group or the fourth lens group or a part of the group. Of course, it is needless to say that the whole extension may be performed by moving all the lenses from the first lens to the fourth lens.

[0060]

As described above, according to the present invention, it is suitable for a video camera, an electronic still camera or the like using a solid-state imaging device or the like, and is small in size, has a zoom ratio of about 3 times, and has an image of 60 ° at the wide-angle end. A zoom lens having an angle and having excellent image forming performance can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a lens according to a first embodiment.

FIG. 2 is an aberration diagram at a wide angle end according to the first embodiment.

FIG. 3 is an aberration diagram of the first embodiment at an intermediate focal length.

FIG. 4 is an aberration diagram at a telephoto end according to the first embodiment.

FIG. 5 is a sectional view of a lens according to a second embodiment.

FIG. 6 is an aberration diagram at a wide-angle end according to a second embodiment.

FIG. 7 is an aberration diagram of the second embodiment at an intermediate focal length.

FIG. 8 is an aberration diagram at a telephoto end in Example 2.

FIG. 9 is a sectional view of a lens according to a third embodiment.

FIG. 10 is an aberration diagram at a wide-angle end according to a third embodiment.

FIG. 11 is an aberrational diagram of the third embodiment at an intermediate focal length.

FIG. 12 is an aberration diagram at a telephoto end in Example 3.

FIG. 13 is a sectional view of a lens according to a fourth embodiment.

FIG. 14 is an aberration diagram at a wide angle end according to the fourth embodiment.

FIG. 15 is an aberration diagram at an intermediate focal length of the fourth embodiment.

FIG. 16 is an aberration diagram at a telephoto end in Example 4.

FIG. 17 is a sectional view of a lens according to a fifth embodiment.

FIG. 18 is an aberration diagram at a wide angle end according to the fifth embodiment.

FIG. 19 is an aberration diagram of Example 5 at an intermediate focal length.

FIG. 20 is an aberration diagram at a telephoto end in Example 5.

FIG. 21 is a sectional view of a lens according to a sixth embodiment.

FIG. 22 is an aberration diagram at a wide-angle end in Example 6.

FIG. 23 is an aberration diagram of Example 6 at an intermediate focal length.

FIG. 24 is an aberration diagram at a telephoto end in Example 6.

FIG. 25 is a sectional view of a lens according to a seventh embodiment.

FIG. 26 is an aberration diagram at a wide angle end according to the seventh embodiment.

FIG. 27 is an aberrational diagram of the seventh embodiment at an intermediate focal length.

FIG. 28 is an aberration diagram at a telephoto end in Example 7.

FIG. 29 is a sectional view of a lens according to an eighth embodiment.

FIG. 30 is an aberration diagram at a wide-angle end in Example 8.

FIG. 31 is an aberration diagram of Example 8 at an intermediate focal length.

FIG. 32 is an aberration diagram at a telephoto end in Example 8.

FIG. 33 is a sectional view of a lens according to a ninth embodiment.

FIG. 34 is an aberration diagram at a wide-angle end in Example 9.

FIG. 35 is an aberrational diagram of the ninth embodiment at an intermediate focal length.

FIG. 36 is an aberration diagram at a telephoto end in Example 9.

FIG. 37 is a sectional view of a lens according to a tenth embodiment.

FIG. 38 is an aberration diagram at a wide-angle end in Example 10.

FIG. 39 is an aberration diagram at an intermediate focal length of the tenth embodiment.

FIG. 40 is an aberration diagram at a telephoto end in Example 10.

FIG. 41 is a sectional view of a lens according to an eleventh embodiment.

FIG. 42 is an aberration diagram at a wide-angle end in Example 11.

FIG. 43 is an aberration diagram at an intermediate focal length of the eleventh embodiment.

FIG. 44 is an aberration diagram at a telephoto end in Example 11.

FIG. 45 is a sectional view of a lens according to a twelfth embodiment.

FIG. 46 is an aberration diagram at a wide-angle end in Example 12.

FIG. 47 is an aberration diagram at an intermediate focal length in Example 12.

FIG. 48 is an aberration diagram at a telephoto end of Example 12.

FIG. 49 is a lens cross-sectional view of Example 13.

FIG. 50 is an aberration diagram at a wide-angle end in Example 13.

FIG. 51 is an aberration diagram of Example 13 at an intermediate focal length.

FIG. 52 is an aberration diagram at a telephoto end in Example 13.

[Explanation of symbols]

 G1: First lens group G2: Second lens group G3: Third lens group G4: Fourth lens group S: Aperture P1: Low-pass filter P2: Cover glass FNO: F number Y: Image height

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H087 KA01 PA07 PA19 PA20 PB09 PB10 QA02 QA07 QA12 QA14 QA22 QA26 QA32 QA34 QA41 QA46 RA05 RA12 RA36 RA42 RA43 SA23 SA27 SA29 SA32 SA63 SA64 SA72 SA75 SB02 SB14 SB25 SB26 SB32

Claims (8)

[Claims] A first lens unit, a second negative lens unit, and a third positive lens unit, in order from the object side;
In a zoom lens in which the first lens group is fixed and the distance between the second lens group and the third lens group is reduced at the time of zooming from the wide-angle end to the telephoto end, the first lens group includes
The second lens group includes at least one negative lens and at least one positive lens, and the third lens group includes an aperture, at least one positive lens, and at least one positive lens. A zoom lens comprising a negative lens and further satisfying the following conditional expression. 3.9 <f1 / f3 <43 (1) 6.3 <TL / fw <7.9 (2) where f1: focal length of the first lens group, f3: focal length of the third lens group, TL: total length of the entire system (Distance from the first surface to the image surface), fw: focal length of the entire system at the wide-angle end. 2. The zoom lens according to claim 1, wherein said zoom lens further satisfies the following conditional expression. -1.4 <f2 / f3 <-0.98 (3) where f2 is the focal length of the second lens group. 3. The zoom lens according to claim 1, wherein the zoom lens further satisfies the following conditional expression. 0.52 <S3 / f3 <1.04 (4) where S3 is the thickness of the third lens group. 4. The zoom lens according to claim 1, wherein said zoom lens further satisfies the following conditional expression. 0.96 <S2 / fw <1.13 (5) where S2 is the thickness of the second lens group. 5. The zoom lens according to claim 1, wherein the zoom lens further includes a fourth lens group on the image side of the positive third lens, and further satisfies the following conditional expression. Zoom lens. 0.1 <f3 / f4 <0.8 (6) where f4 is the focal length of the fourth lens group. 6. The zoom lens according to claim 1, further comprising a fourth lens group on the image side of the positive third lens, and further satisfying the following conditional expression. Zoom lens. 2.7 <Σd / S2 <4.05 (7) where, S2: the thickness of the second lens group, Σd: the thickness of the first lens group, the thickness of the second lens group, and the thickness of the third lens group. The total thickness of the fourth lens group. 7. The zoom lens according to claim 1, wherein the zoom lens comprises only a flat surface or a spherical surface.
A zoom lens according to claim 1. 8. The lens system according to claim 1, wherein the third lens group has a stop disposed closest to the object, and at least one surface of the lens closest to the image is an aspheric surface. The zoom lens described.