CN2763825Y - Sectional zoom lens - Google Patents

Abstract

The utility model discloses a sectional zoom lens with simple structure and short total length. From an object side, the zoom lens orderly comprises a first lens group with negative refractive power, a second lens group and a third lens group with positive refractive power, wherein both the first lens group and the third lens group are composed of single lens bodies; the second lens group comprises a first lens unit with positive refractive power, and a second lens unit with negative refractive power; the second lens unit is also composed of single lens bodies. The first lens group and the third lens group are fixed and immovable; the second lens group moves from front to rear to change focal length. The focal length of every lens group satisfies the following relational expressions: f2 * (1 + Z< 1/2 >) >-f1f2; (1 + 1/Z< 1/2 >) > (f3 * fb) / (f3-fb), wherein f1 denotes the focal length of the first lens group; f2 denotes the focal length of the second lens group; f3 denotes the focal length of the third lens group; fb denotes rear focal length; z denotes zoom multiplying power.

Description

The sectional type zoom lens

Technical field

The utility model relates to a kind of zoom lens, relates in particular to the negative sectional type zoom lens of just arranging of three groups of short formulas of a kind of total length.

Background technology

In recent years, camera, simple and easy digital camera, have take pictures or the application of portable electron device such as PDA of recording function, mobile phone more and more widely.But the electronic installation that has image-forming module in these is because of the restriction of self thickness, requires the total length of its entrained zoom lens short as much as possible usually, structure is simple as much as possible, to adapt to the development trend of the low framework of portable type electronic product.

On April 8th, 2003, the United States Patent (USP) of bulletin disclosed the negative camera lens of just arranging of a kind of three groups of formulas for the 6th, 545, No. 824.Three groups of lens groups of this camera lens are formed by the multi-disc lens, its complex structure, and cause the camera lens total length bigger, thereby it is not suitable for being applied on the low framework electronic product, and second lens group moves forward and backward to reach focus function can not realize zoom function, thereby this camera lens can not change visible sensation distance and carries out elasticity and find a view when taking pictures.Therefore, how to provide a kind of zoom lens that overcomes the problems referred to above to become the problem that needs to be resolved hurrily.

Therefore, how to provide a kind of zoom mechanism that can overcome the zoom lens of the problems referred to above to become the problem that needs to be resolved hurrily.

Summary of the invention

At the defective that above-mentioned prior art exists, the utility model purpose provides a kind of sectional type zoom lens, and it is simple in structure, total length is shorter.

For achieving the above object, the utility model provides a kind of sectional type zoom lens, images on the imageing sensor, from the thing side direction, comprise having negative refractive power first lens group successively, have positive refractive power second lens group and have positive refractive power the 3rd lens group.Wherein, first lens group and the 3rd lens group are formed by single mirror body; Second lens group comprises first lens unit with positive refractive power and second lens unit with negative refractive power, and second lens unit also is made up of single mirror body; The relative imageing sensor with the 3rd lens group of first lens group maintains static, and second lens group moves forward and backward to change focal length; And the focal length of each lens group satisfies following relational expression:

$\begin{array}{c}{f}_2\&CenterDot;(1+\sqrt{z})>-f_1\\ f_2\&CenterDot;(1+\frac{1}{\sqrt{z}})>\frac{f_3\&CenterDot;f_b}{f_3-f_b}\end{array}$

Wherein, f1 represents the focal length of first lens group, and f2 represents the focal length of second lens group, and f3 represents the focal length of the 3rd lens group, and fb represents back focal length, and z represents zoom ratio.

Because first lens group and the 3rd lens group of utility model sectional type zoom lens are formed by single mirror body, second lens group comprises that refractive power is that one positive one two negative lens units are formed, and first lens group and the 3rd lens group maintain static, move second lens group with the change focal length, thereby it is simple in structure, total length is shorter.

Description of drawings

Below in conjunction with drawings and Examples the utility model is described in further detail.

Fig. 1 is the sectional view that first embodiment of the utility model sectional type zoom lens is in primary importance.

Fig. 2 is the sectional view that first embodiment of the utility model sectional type zoom lens is in the second place.

Fig. 3 A-Fig. 3 C is the various aberration diagrams that first embodiment of the utility model sectional type zoom lens is in primary importance.

Fig. 4 A-Fig. 4 C is the various aberration diagrams that first embodiment of the utility model sectional type zoom lens is in the second place.

Fig. 5 is the sectional view that second embodiment of the utility model sectional type zoom lens is in primary importance.

Fig. 6 is the sectional view that second embodiment of the utility model sectional type zoom lens is in the second place.

Fig. 7 A-Fig. 7 C is the various aberration diagrams that second embodiment of the utility model sectional type zoom lens is in primary importance.

Fig. 8 A-Fig. 8 C is the various aberration diagrams that second embodiment of the utility model sectional type zoom lens is in the second place.

Fig. 9 is the sectional view that the 3rd embodiment of the utility model sectional type zoom lens is in primary importance.

Figure 10 is the sectional view that the 3rd embodiment of the utility model sectional type zoom lens is in the second place.

Figure 11 A-Figure 11 C is the various aberration diagrams that the 3rd embodiment of the utility model sectional type zoom lens is in primary importance.

Figure 12 A-Figure 12 C is the various aberration diagrams that the 3rd embodiment of the utility model sectional type zoom lens is in the second place.

Figure 13 is the sectional view that the 4th embodiment of the utility model sectional type zoom lens is in primary importance.

Figure 14 is the sectional view that the 4th embodiment of the utility model sectional type zoom lens is in the second place.

Figure 15 A-Figure 15 C is the various aberration diagrams that the 4th embodiment of the utility model sectional type zoom lens is in primary importance.

Figure 16 A-Figure 16 C is the various aberration diagrams that the 4th embodiment of the utility model sectional type zoom lens is in the second place.

Figure 17 is the sectional view that the 5th embodiment of the utility model sectional type zoom lens is in primary importance.

Figure 18 is the sectional view that the 5th embodiment of the utility model sectional type zoom lens is in the second place.

Figure 19 A-Figure 19 C is the various aberration diagrams that the 5th embodiment of the utility model sectional type zoom lens is in primary importance.

Figure 20 A-Figure 20 C is the various aberration diagrams that the 5th embodiment of the utility model sectional type zoom lens is in the second place.

Embodiment

Fig. 1 and Fig. 2 disclose first embodiment of the utility model sectional type zoom lens 100, and light focuses on the imageing sensor 220 after seeing through sectional type zoom lens 100 and imageing sensor cover glass 210.In the present embodiment, from the thing side, sectional type zoom lens 100 comprises first lens group 110 with negative refractive power, the 3rd lens group 130 that has second lens group 120 of positive refractive power and have positive refractive power successively, and the focal length of each lens group of this sectional type zoom lens 100 should satisfy following relational expression (1) and (2):

$f_2\&CenterDot;(1+\sqrt{z})>-f_1---\left(1\right)$

$f_2\&CenterDot;(1+\frac{1}{\sqrt{z}})>\frac{f_3\&CenterDot;f_b}{f_3-f_b}---\left(2\right)$

Wherein, f1 represents the focal length of first lens group 110, and f2 represents the focal length of second lens group 120, and f3 represents the focal length of the 3rd lens group 130, and fb represents back focal length (Back FocalLength), and z represents zoom ratio.

First lens group 110 is made up of a convex-concave negative lens 111.For reducing the aberration of sectional type zoom lens 100, the Abbe number of convex-concave negative lens 111 is more preferably greater than 50.For reducing the aberration of sectional type zoom lens 100,111 liang of planes of refraction of convex-concave negative lens all adopt the aspheric surface design in addition, and these aspheric surfaces can be represented with following formula (3):

$X=\frac{{\mathrm{cS}}^2}{1+\sqrt{1-(K+1)c^2{S}^2}}+A_4{S}^4+A_6{S}^6+A_8{S}^8+A_{10}{S}^{10}+A_{12}{S}^{12}---\left(3\right)$

Wherein, c represents the curvature at place, aspheric surface refracting surface summit, S represents the distance from the aspheric surface refracting surface coordinate points to optical axis, K represents the circular cone coefficient, A4, A6, A8 and A10 represent asphericity coefficient, X represent from and optical axis distance be that the aspheric surface refracting surface coordinate points of S is to the distance the section on aspheric surface refracting surface summit.

Second lens group 120 comprises first lens unit U1 with positive refractive power and the second lens unit U2 with negative refractive power.The first lens unit U1 comprises at least one single mirror body (balsaming lens, compound lens or single eyeglass), and in the present embodiment, it is made up of the balsaming lens that a biconvex positive lens 121 and concavo-convex negative lens 122 gummeds form.The second lens unit U2 is made up of a concave-concave negative lens 125, in order to proofread and correct the aberration and the aberration of sectional type zoom lens 100, for further reducing the aberration of sectional type zoom lens 100,125 liang of planes of refraction of double-concave negative lens also all adopt the aspheric surface design, and these aspheric surfaces can be used formula (3) expression.

The 3rd lens group 130 is made up of a biconvex positive lens 131, biconvex positive lens 131 is in order to compensate the aberration that first lens group 110 produces, and the focusing that improves sectional type zoom lens 100 heart far away (Telecentricity), help the light that imageing sensor 200 sensings see through sectional type zoom lens 100.This biconvex positive lens 131 is towards the plane of refraction almost plane of thing side in addition, but thereby help the ultrared multicoating of plating filtering, to reduce the influence of infrared ray to imageing sensor 200, improve the colors of image correctness, and save base material sheet glass as filtering infrared ray multicoating, can design shorter camera lens.

The utility model sectional type zoom lens 100 also comprises an aperture diaphragm (not marking among the figure), roughly be hollow form, pass for light, in the present embodiment, aperture diaphragm is fixed as one near second lens group 120 and with second lens group 120, with the zoom of reduction sectional type zoom lens 100 and the control difficulty of focusing.

The zoom process of the utility model sectional type zoom lens 100 is described below in conjunction with Fig. 1 and Fig. 2.

First lens group 110 maintains static with the 3rd lens group 130 relative imageing sensors 220, move forward and backward of zoom and the focusing of second lens group 120 to realize sectional type zoom lens 100 simultaneously, for making the utility model sectional type zoom lens 100 not need additional separately focusing offset lens group still can image on the imageing sensor 220,120 of this second lens groups are in the primary importance or the second place, move to the another location to change the focal length of sectional type zoom lens 100 by second lens group 120 by a position, and focus simultaneously on given object distance, thereby, this kind zoom mode is different from the continuous vari-focus mode of the zoom lens with focusing offset lens group, and the selection zoom position that only can disperse and reach the sectional type zoom.In the present embodiment, primary importance is a wide-angle side, and the second place is the end of dolly-out,ing dolly-back.When second lens group 120 was in primary importance, as shown in Figure 1, the focal length of sectional type zoom lens 100 was the shortest; When second lens group 120 was in the second place, as shown in Figure 2, the focal length of sectional type zoom lens 100 was the longest.

The particular data relevant with first embodiment is listed in the table one, two, wherein, R represents radius-of-curvature, d1, d2 represent the distance between the lens plane of refraction summit of first and second position respectively, v represents the Abbe number of lens, nd represents that (refractive index of λ=587.6nm), the unit of d1, d2 and r is " mm " to the d line in addition.

Table one

Plane of refraction	R	d1	d2	nd	v
								1 2 3 4 5 6 7 8 9 10 11	15.170 4.184 2.700 -4.896 -16.370 -5.145 4.029 39.380 -5.329 ∞ ∞	0.600 5.133 2.600 0.400 0.400 0.600 0.431 1.672 2.230 0.300 0.500	0.600 2.201 2.600 0.400 0.400 0.600 3.363 1.672 2.230 0.300 0.500	1.530 1.714 1.806 1.586 1.517 1.517	55.9 53.9 25.5 30.1 64.2 64.2	Aspheric surface aspheric surface aperture diaphragm aspheric surface aspheric surface

Table two

Plane of refraction
						1	2	6	7
K A4 A6 A8 A10 A12	10 -0.650884E-2 0.958770E-3 -0.657142E-4 -0.937298E-7 0.184416E-6	-15.604 0.189365E-1 -0.659529E-2 0.185936E-2 -0.276315E-3 0.166120E-4	10 -0.410924E-1 -0.870482E-3 0.106907E-1 -0.101026E-1 0.290921E-2	-10 -0.267435E-2 -0.428714E-3 0.397223E-2 -0.191713E-2 0.313116E-3

The respective value of each lens group focal length is as follows in the present embodiment:

f1＝-11.110

f2＝5.540

f3＝9.200

fb＝3.030

z＝1.680

Fig. 3 A-Fig. 3 C and Fig. 4 A-Fig. 4 C are the various aberration diagrams of present embodiment sectional type zoom lens 100 when being in the primary importance and the second place respectively, wherein, the pupil radius of PR (Pupil Radius) expression sectional type zoom lens 100, the maximum image field of MF (Maximum Field) expression sectional type zoom lens 100, and by d line (λ=587.6nm), F line (λ=486.1nm) and the C line (optical characteristics of the various aberrations explanation sectional type zoom lens 100 of λ=656.3nm), in astigmatism figure, the S line is the radial astigmatism curve, and the T line is tangential astigmatism curve.

Fig. 5 and Fig. 6 disclose second embodiment of the utility model sectional type zoom lens 100, present embodiment is similar to Fig. 1, embodiment shown in Figure 2, its difference is: the first lens unit U1 of second lens group 120 is made up of a compound lens (Hybrid) and a concave-concave negative lens 123, this compound lens is that a plastics negative lens 122 ' is overlaid on biconvex positive lens 121 and forms on the plane of refraction as side, and plastics negative lens 122 ' is an aspheric surface towards the plane of refraction as side, is used to eliminate the aberration and the higher order aberratons of sectional type zoom lens 100; And the second lens unit U3 of second lens group 120 is made up of a convex-concave negative lens 125 '.

The particular data relevant with second embodiment is listed in the table three, four, and its special parameter meaning is described in first embodiment.

Table three

Plane of refraction	R	d1	d2	nd	v
								1 2 3 4 5 6 7 8 9 10 11 12 13	19.995 3.857 2.499 -9.978 -9.978 -6.501 3.008 2.456 2.918 11.742 -11.742 ∞ ∞	0.600 5.639 1.135 0.040 0.466 0.600 0.193 0.720 2.440 1.670 0.698 0.300 0.500	0.600 2.759 1.135 0.040 0.466 0.600 0.193 0.720 5.320 1.670 0.698 0.300 0.500	1.543 1.803 1.520 1.847 1.525 1.713 1.517	56.0 46.4 51.4 23.8 56.3 53.8 64.2	Aspheric surface aspheric surface aperture diaphragm aspheric surface aspheric surface aspheric surface

Table four

Plane of refraction
							1	2	5	8	9
K A4 A6 A8 A10 A12	9.998414 -0.430239E-2 0.852077E-4 0.206663E-4 -0.236851E-6 0	-6.018141 0.844452E-2 -0.132563E-2 0.841895E-4 0.147235E-4 0	4.549282 0.120077E-1 -0.127473E-1 0.135419E-1 -0.508264E-2 0	0.331269 -0.313210E-1 -0.224909E-1 -0.504784E-2 0.264617E-2 0	3.530066 -0.620857E-2 -0.437533E-1 0.203316E-1 -0.847188E-2 0

The focal length of each lens group satisfies relational expression (1) and (2) in the present embodiment, and its respective value is as follows:

f1＝-8.910

f2＝4.956

f3＝88.486

fb＝1.498

z＝1.771

Fig. 7 A-Fig. 7 C and Fig. 8 A-Fig. 8 C are the various aberration diagrams that present embodiment sectional type zoom lens 100 is in the primary importance and the second place respectively, and its each symbolic significance is described in first embodiment.

Fig. 9 and Figure 10 disclose the 3rd embodiment of the utility model sectional type zoom lens 100, present embodiment is similar to Fig. 1, embodiment shown in Figure 2, and its difference is: the first lens unit U1 of second lens group 120 is made up of a biconvex positive lens 121 and a concave-concave negative lens 123; The 3rd lens group 130 is made up of a plano-convex positive lens 132.

The particular data relevant with the 3rd embodiment is listed in the table five, six, and its special parameter meaning is described in first embodiment.

Table five

Plane of refraction	R	d1	d2	nd	v
								1 2 3 4 5 6 7 8 9 10 11 12	15.146 4.577 2.360 -25.167 -18.123 3.984 7.472 3.999 ∞ -6.650 ∞ ∞	0.600 6.155 1.303 0.269 0.600 0.353 0.600 0.226 1.540 3.195 0.300 0.500	0.600 2.675 1.303 0.269 0.600 0.353 0.600 3.706 1.540 3.195 0.300 0.500	1.530 1.714 1.806 1.586 1.517 1.517	55.9 53.9 25.5 30.1 64.2 64.2	Aspheric surface aspheric surface aperture diaphragm aspheric surface aspheric surface

Table six

Plane of refraction
						1	2	7	8
K A4	10 -0.265236E-2	-17.936620 0.186584E-1	10 -0.715584E-2	-10 -2.007840E-1

A6 A8 A10 A12

-0.414322E-4 0.444892E-4 -0.357411E-5 0.104452E-6

-0.548912E-2 0.112657E-2 -0.I 19483E-3 0.546056E-5

-0.207769E-1 0.113479E-1 -0.124601E-1 0.290921E-2

-9.169090E-2 0.628447E-2 -0.151789E-2 0.313116E-3

The focal length of each lens group satisfies relational expression (1) and (2) in the present embodiment, and its respective value is as follows:

f1＝-12.620

f2＝6.600

f3＝9.330

fb＝3.995

z＝1.680

Figure 11 A-Figure 11 C and Figure 12 A-Figure 12 C are the various aberration diagrams that present embodiment sectional type zoom lens 100 is in the primary importance and the second place respectively, and its each symbolic significance is described in first embodiment.

Figure 13 and Figure 14 disclose the 4th embodiment of the utility model sectional type zoom lens 100, and present embodiment is similar to Fig. 5, embodiment shown in Figure 6, and its difference is: first lens group 110 is made up of a concave-concave negative lens 111 '; The first lens unit U1 of second lens group 120 is made up of a biconvex positive lens 121 and a concave-concave negative lens 123.

The particular data relevant with the 4th embodiment is listed in the table seven, eight, and its special parameter meaning is described in first embodiment.

Table seven

Plane of refraction	R	d1	d2	nd	v
								1 2 3 4 5 6 7 8	-7.549 3.680 2.588 -5.913 -2.721 23.966 3.904 5.156	0.600 4.851 2.014 0.412 0.600 0.199 0.720 2.981	0.600 2.962 2.014 0.412 0.600 0.199 0.720 4.870	1.491 1.713 1.805 1.521	57.4 53.8 25.4 48.1	Aspheric surface aspheric surface aperture diaphragm aspheric surface aspheric surface

9 10 11 12

10.529 -625.866 ∞ ∞

1.243 0.600 0.300 0.500

1.243 0.600 0.300 0.500

1.602 1.517

63.5 64.2

Table eight

Plane of refraction
						1	2	7	8
K A4 A6 A8 A10 A12	-5.6510 -1.776137E-2 2.587407E-3 -1.600197E-4 2.851552E-6 0	-6.7294 -3.499917E-3 1.190527E-4 3.367767E-4 -2.860850E-5 0	0 -2.159358E-2 -9.661138E-3 -3.600200E-3 1.654988E-3 0	3.3876 -3.432277E-5 -1.3457811E-2 2.400977E-3 2.623520E-5 0

The focal length of each lens group satisfies relational expression (1) and (2) in the present embodiment, and its respective value is as follows:

f1＝-4.943

f2＝4.756

f3＝16.978

fb＝1.400

z＝1.730

Figure 15 A-Figure 15 C and Figure 16 A-Figure 16 C are the various aberration diagrams that present embodiment sectional type zoom lens 100 is in the primary importance and the second place respectively, and its each symbolic significance is described in first embodiment.

Figure 17 and Figure 18 disclose the 5th embodiment of the utility model sectional type zoom lens 100, present embodiment is similar to Fig. 5, embodiment shown in Figure 6, and its difference is: the first lens unit U1 of second lens group 120 is made up of a biconvex positive lens 121, a concave-concave negative lens 123 and a convex-concave positive lens 124; And the 3rd lens group 130 form by a concavo-convex positive lens 133.

The particular data relevant with the 5th embodiment is listed in the table nine, ten, and its special parameter meaning is described in first embodiment.

Table nine

Plane of refraction	R	d1	d2	nd	v
								1 2 3 4 5 6 7 8 9 10 11 12 13 14	52.114 3.708 2.925 -11.208 -4.977 4.840 2.850 10.275 3.938 2.864 -26.937 -7.622 ∞ ∞	0.600 5.240 1.117 0.558 0.572 0.145 1.115 0.200 0.798 1.927 1.330 0.597 0.300 0.500	0.600 2.568 1.117 0.558 0.572 0.145 1.115 0.200 0.798 4.599 1.330 0.597 0.300 0.500	1.543 1.804 1.805 1.517 1.520 1.713 1.517	56.0 46.5 25.5 64.2 51.4 53.8 64.2	Aspheric surface aspheric surface aperture diaphragm aspheric surface aspheric surface

Table ten

Plane of refraction
						1	2	9	10
K A4 A6 A8 A10 A12	1.541916 -0.217713E-3 -0.146712E-3 0.692152E-5 0.436252E-6 0	0.062104 0.117334E-2 -0.175252E-3 -0.645287E-4 0.136159E-4 0	-5.002061 -0.343674E-1 -0.812569E-2 -0.139806E-2 -0.151730E-3 0	-4.167022 -0.350275E-2 -0.589330E-2 -0.121543E-3 0.407579E-3 0

The focal length of each lens group satisfies relational expression (1) and (2) in the present embodiment, and its respective value is as follows:

f1＝-7.380

f2＝4.440

f3＝14.490

fb＝1.397

z＝1.791

Figure 19 A-Figure 19 C and Figure 20 A-Figure 20 C are the various aberration diagrams that present embodiment sectional type zoom lens 100 is in the primary importance and the second place respectively, and its each symbolic significance is described in first embodiment.

In addition in the various embodiments described above, the convex-concave negative lens 111 of first lens group 110 or double-concave negative lens 111 ' can adopt the balsaming lens with negative refractive power or the design of compound lens, the biconvex positive lens 131 of the 3rd lens group 130, plano-convex positive lens 132 or concavo-convex positive lens 133 also can adopt the balsaming lens with positive refractive power or the design of compound lens, with further elimination sectional type zoom lens 100 higher order aberratons.

Claims (9)

1, a kind of sectional type zoom lens images on the imageing sensor, from the thing side direction, comprises successively:

First lens group, first lens group has negative refractive power;

Second lens group, second lens group has positive refractive power; And

The 3rd lens group, the 3rd lens group has positive refractive power;

It is characterized in that: first lens group and the 3rd lens group are formed by single mirror body; Second lens group comprises first lens unit with positive refractive power and second lens unit with negative refractive power, and second lens unit is made up of single mirror body; The relative imageing sensor with the 3rd lens group of first lens group maintains static, and second lens group moves forward and backward to change focal length; And the focal length of each lens group satisfies following relational expression:

$f_2\&CenterDot;(1+\sqrt{z})>-f_1$

$f_2\&CenterDot;(1+\frac{1}{\sqrt{z}})>\frac{f_3\&CenterDot;f_b}{f_3-f_b}$

Wherein, f1 represents the focal length of first lens group, and f2 represents the focal length of second lens group, and f3 represents the focal length of the 3rd lens group, and fb represents back focal length, and z represents zoom ratio.

2, sectional type zoom lens as claimed in claim 1 is characterized in that: second lens unit of described first lens group, second lens group and the 3rd lens group are formed by a slice lens.

3, sectional type zoom lens as claimed in claim 2 is characterized in that: two planes of refraction of the lens of second lens unit of described first lens group and second lens group are aspheric surface.

4, sectional type zoom lens as claimed in claim 3 is characterized in that: the lens of described first lens group are a convex-concave negative lens; First lens unit of described second lens group is made up of the balsaming lens that a biconvex positive lens and a concavo-convex negative lens compose; The lens of second lens unit of described second lens group are a concave-concave negative lens; The lens of described the 3rd lens group are a biconvex positive lens.

5, sectional type zoom lens as claimed in claim 3 is characterized in that: the lens of described first lens group are a convex-concave negative lens; First lens unit of described second lens group is become with a concave-concave negative lens group by a compound lens, and this compound lens is made up of a biconvex positive lens and a plastics negative lens; The lens of second lens unit of described second lens group are a convex-concave negative lens; The lens of described the 3rd lens group are a biconvex positive lens.

6, sectional type zoom lens as claimed in claim 5 is characterized in that: described plastics negative lens is an aspheric surface towards the plane of refraction as side.

7, sectional type zoom lens as claimed in claim 3 is characterized in that: the lens of described first lens group are a convex-concave negative lens; First lens unit of described second lens group is become with a concave-concave negative lens group by a biconvex positive lens; The lens of second lens unit of described second lens group are a concave-concave negative lens; The lens of described the 3rd lens group are a plano-convex positive lens.

8, sectional type zoom lens as claimed in claim 3 is characterized in that: the lens of described first lens group are a concave-concave negative lens; First lens unit of described second lens group is become with a concave-concave negative lens group by a biconvex positive lens; The lens of second lens unit of described second lens group are a convex-concave negative lens; The lens of described the 3rd lens group are a biconvex positive lens.

9, sectional type zoom lens as claimed in claim 3 is characterized in that: the lens of described first lens group are a convex-concave negative lens; First lens unit of described second lens group is made up of a biconvex positive lens, a concave-concave negative lens and a convex-concave positive lens; The lens of second lens unit of described second lens group are a convex-concave negative lens; The lens of described the 3rd lens group are a concavo-convex positive lens.

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