JP2007155948A - Zoom lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To miniaturize a zoom lens system to make an apparatus compact by eliminating a negative meniscus lens placed on the object side of a reflecting face or a rectangular prism. <P>SOLUTION: The zoom lens system comprises a rectangular prism P for refracting a luminous flux at about 90°, a first lens group L1 comprising a negative reflecting lens and a positive lens and having a negative optical power as the whole, a second lens group L2 comprising positive, positive, and negative lenses and having a positive optical power as the whole, and a third lens group L3 having a positive optical power, which are arranged in order from the object side, and varies the magnification by changing air gaps between the rectangular prism P and the first lens group L1, between the first lens group L1 and the second lens group L2, and between the second lens group L2 and the third lens group L3 and satisfies 0.75<D/f2<1.25 and R2B>0 wherein; f2 is a focal length of the second lens group; D is an overall length of the second lens group; and R2B is a radius of curvature of the backmost surface of the second lens group, and has the first lens group placed in almost the same position at the widest angle end and the maximum telephoto end. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a low-magnification zoom lens for photographing an image such as a digital camera or a mobile phone.

  With the advancement of optical image digitization technology, digital cameras, mobile phones with photographing functions, etc. have rapidly spread. In order to differentiate from other models as competition intensifies, there is a demand for higher functionality by zooming the photographic lens as well as making it more compact and thinner for greater portability. The demand for zooming in the taking lens contradicts the miniaturization and thinning of the equipment. Therefore, a method has been proposed in which the zoom lens system is bent in the middle of the original connection so that the thickness of the device does not increase.

  For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 11-196303) has a configuration in which a negative lead zoom lens system is arranged by bending the optical path by 90 ° on a reflection surface provided on the image side of a negative meniscus fixed lens element. It is disclosed.

  In Patent Document 2 (Japanese Patent Laid-Open No. 11-258678), a negative meniscus fixed lens element and a movable positive lens group are provided with a reflecting surface behind them, and the light beam is bent by 90 °, followed by a positive lens group. The structure which distributes is disclosed.

Further, in Patent Document 3 (Japanese Patent Laid-Open No. 8-248318), Patent Document 4 (Japanese Patent Laid-Open No. 2000-131610), and Patent Document 5 (Japanese Patent Laid-Open No. 2003-202500), the first group of positive power is A multi-group zoom system composed of a negative lens, a right-angle prism that bends the optical path by 90 °, and a positive lens is disclosed.
JP 11-196303 A JP 11-258678 A JP-A-8-248318 JP 2000-131610 A JP 2003-202500 A

  The above-described conventional technology has a configuration in which a reflecting surface or a right-angle prism is disposed behind a meniscus-shaped negative lens to bend the optical connection by 90 ° in order to achieve both a wide angle at the wide end of the photographic lens and a thinner device. there were. However, this configuration has a problem that the overall length of the zoom lens system itself becomes long and the size thereof increases. An object of the present invention is to reduce the size of a zoom lens system so that a meniscus negative lens placed on the object side of a reflecting surface or a right-angle prism is eliminated and the apparatus becomes compact.

  The present invention is a zoom lens in which a fixed field lens third group is added to a negative / positive power two-group zoom, and the zoom system is made compact by defining the overall length and lens shape of the second lens group. is there.

That is, the invention of claim 1 is composed of a negative lens and a positive lens in order from the object side and having a negative optical power as a whole, a positive first lens group, a positive lens, and a negative lens. A second lens group having a positive optical power, a third lens group having a positive optical power, a prism and a first lens group, a first lens group and a second lens group, and a second lens group and a third lens group. By changing the air spacing of the lens group,
0.75 <D / f2 <1.25
R2B> 0
Here, f2 is the focal length of the second lens group, D is the total length of the second lens group, R2B is the radius of curvature of the rearmost surface of the second lens group, and the zoom ratio is about 3.

  According to a second aspect of the present invention, in the zoom lens of the first aspect, the first group lens is disposed at substantially the same position on the subject side in the widest-angle end state and the telephoto end state, and moves on the image side. It is characterized by being scaled.

  According to a third aspect of the present invention, in the zoom lens of the first or second aspect, a right-angle prism that bends the light beam by approximately 90 ° is disposed on the object side of the first lens group, and the prism, the first lens group, and the first lens group The zoom lens is characterized by changing the magnification by changing the air distance between the second lens group and the second lens group and the third lens group.

  According to a fourth aspect of the present invention, in the zoom lens according to any one of the first to third aspects, the zoom ratio is about 3.

  According to the present invention, the overall length of the zoom lens can be shortened, and the device can be made thinner and more compact.

  A lens for a digital camera, a mobile phone photographing device, etc. is a condition that requires a wide angle of view with a small size and light weight and a large amount of information. For this reason, it is desirable that the zoom lens has a small number of constituent elements and that the zooming method is simple, that the wide end has a wide angle, and that the principal ray is close to telecentric on the image side. A system in which a field lens is added to a two-group zoom skeleton having negative and positive powers has a possibility of satisfying these conditions.

  As shown in FIG. 1, the zoom lens Z according to the present example includes a right-angle prism P that bends light approximately 90 ° in order from the object side, a negative lens, and a positive lens, and has a negative optical power as a whole. One lens unit L1, a second lens unit L2 including positive, positive, and negative lenses and having a positive optical power as a whole, and a third lens unit L3 having a positive optical power. In this example, the first lens group L1, the second lens group L2, and the third lens group L3 are moved by a cam device, and the right-angle prism P and the first lens group L1, the first lens group L1 and the second lens group L2, Further, the magnification is changed by changing the air gap between the second lens unit L2 and the third lens unit L3.

  1A shows a wide angle, FIG. 1B shows a standard position, and FIG. 1C shows a lens arrangement position on a telephoto position.

In this example, the zoom lens Z is
0.75 <D / f2 <1.25
R2B> 0
However,
f2: Focal length of the second lens group D: Total length of the second lens group R2B: The condition of the radius of curvature of the rearmost surface of the second lens group is satisfied. Thereby, the zoom lens can be made compact.

  In the zoom lens Z according to this example, the first and second lens groups are configured to include elements of positive and negative power so as to have an achromatic ability in order to reduce the upward chromatic aberration and the lateral chromatic aberration in the entire zoom range. . On the other hand, the third lens group necessary for realizing the image side telecentricity is located close to the image plane, and therefore does not need to be achromatic. In addition, the right-angle prism P can secure a larger amount of peripheral light with a smaller shape as the refractive index of the material increases.

  In this example, the first lens group has a negative / positive power configuration, and a wide-angle distortion is corrected by introducing an aspherical surface to the leading negative lens.

  The second lens group has a configuration in which the ratio of the focal length f2 to the total lens length D is 0.75 <D / f2 <1.25, and R2B> 0, so that compactness and good correction of astigmatism are achieved. Can be realized. Under the two conditions, the forward tilt and the rear principal point position of the second lens group are formed closer to the object side, so that the focal length of the second lens group can be shortened and the system can be made compact. Here, if D / f2 exceeds the lower limit, the correction of astigmatism is not sufficient, and if the upper limit is exceeded, the entire length of the second lens group becomes large, which is an obstacle to compactness.

  In addition, since R2B> 0, the principal point position is formed closer to the object side, so that the focal length of the second lens group can be reduced, which is preferable for making the system compact. If F2B <0, the focal length of the second lens group cannot be reduced, which is not preferable for making the system compact.

  The occurrence of spherical aberration due to the increase in power of the second lens group due to the above two conditions can be corrected by making one or two surfaces in the second lens group aspherical.

  Further, in this example, the first lens unit L1 is moved and scaled to the image side between the widest-angle end (FIG. 1A) and the telephoto end (FIG. The position is substantially the same. As a result, the air-to-air distance between the right-angle prism P and the first lens unit L1 can be made substantially the same at the widest-angle end and the telephoto end, and the right-angle prism P and the first lens unit L1 are brought close to each other. Therefore, the overall length of the zoom lens Z can be shortened.

  FIG. 2 shows a cam diagram for moving the first lens group, the second lens group, and the third lens group. In this example, in the region between the widest end and the telephoto end, the lens is in a pan focus state, and the focal length of the zoom lens Z is changed by moving each lens group.

  In this example, a wide-angle macro area is provided outside the widest-angle end with a switching area interposed therebetween. In addition, a telescopic macro area is provided outside the most telephoto end with a switching area interposed therebetween. In this example, autofocus is realized in these regions by moving the third lens unit L3. The first lens unit L1 does not move in both macro regions, and the air space between the right-angle prism P and the first lens unit L1 does not become narrower. For this reason, it is not necessary to widen the air space between the right-angle prism P and the first lens unit L1.

Examples of the zoom lens according to the present invention will be described below. However, f is a focal length, F is an F number, r is a radius of curvature, d is a surface interval, n is a refractive index, and v is an Abbe number. Further, a surface marked with * in r indicates an aspheric surface, and the aspheric surface is expressed by the following equation. However, X is the sag amount in the optical axis direction, and Y is the incident light height.
X = Y ^** 2 / (l tens sqrt (lA * (Y / r ) ** 2)) Ten ^{A4Y ** f * 4 + A6Y **} 6 + A8Y ** 8 + A10Y ** 10

  3 is a lens configuration diagram of the zoom lens according to Example 1. FIG. 3A shows the widest angle state, FIG. 3B shows the standard state, FIG. 3C shows the maximum telephoto state, and FIG. FIG. 5 is a graph showing spherical aberration, astigmatism, and distortion in the standard state of the zoom lens according to Example 1, and FIG. 4 is a graph showing spherical aberration, astigmatism, and distortion in the maximum telephoto state of the zoom lens according to Example 1;

In FIGS. 4 to 6, reference signs A to E attached to the curves indicate differences in wavelength as shown below (the same applies to FIGS. 8 to 10 and FIGS. 12 to 14).
A: 0.43584 μm
B: 0.48613 μm
C: 0.54607 μm
D: 0.58756 μm
E: 0.65628 μm

The zoom lens according to the present embodiment has the following configuration.
r1 = ∞ d1 = 5.900 n1 = 1.78472 v1 = 25.7
r2 = ∞ d2 = 0.320〜1.787〜0.304
r3 = -185.750 d3 = 0.800 n2 = 1.71300 v2 = 53.9
r4 = 3.370 d4 = 0.020 n3 = 1.51313 v3 = 53.9
r5 ^* = 2.704 d5 = 0.760
r6 = 4.510 d6 = 1.130 n4 = 1.80610 v4 = 33.3
r7 = 12.900 d7 = 6.521 ~ 2.023 ~ 0.407
r8 ^* = 5.140 d8 = 0.020 n5 = 1.51313 v5 = 53.9
r9 = 4.073 d9 = 1.430 n6 = 1.48749 v6 = 70.4
r10 = -6.600 d10 = 0.100
r11 = 5.760
d11 = 1.300
n7 = 1.58913
v7 = 61.2
r12 = -12.720 dl2 = 0.100
r13 = 15.500
d13 = 1.320
n8 = 1.80518
v8 = 25.5
r14 = 2.496 d14 = 3.123〜6.154〜9.252
r15 = 10.130
d15 = 1.180
n9 = 1.80518
v9 = 25.5
r16 = -56.350 d16 = 0.66
r17 = ∞
d17 = 1.15
n10 = 1.51680
v10 = 64.2
r18 = ∞

f = 4.15 ~ 7.99 ~ 11.94
F = 2.86〜4.08〜5.34
Angle of view = 65.0 ° to 34.4 ° to 23.4 °

Aspheric data 5th surface (r5 ^* )
A 0.2734
A4 -0.175308E-02
A6 0.109505E-02
A8 -0.225209E-03
A10 0.158585E-04

8th surface (r8 ^* )
A -5.8125
A4 0.152408E-02
A6 -0.425403E-03
A8 0.186806E-03
A10 -0.513259E-04

f2 = 5.536 D = 0.27 D / f2 = 0.77

  That is, as shown in FIG. 3, the zoom lens according to this example is arranged as shown in (a) in the widest angle state, (b) in the standard state, and (c) in the maximum telephoto state. It is moved between states according to a predetermined cam curve similar to the predetermined cam curve shown in FIG.

  4 has the spherical aberration, critical aberration, and distortion shown in FIG. 4 in the widest angle state, FIG. 5 in the standard state, and FIG. 6 in the maximum telephoto state. These spherical aberrations, critical aberrations and distortions are excellent enough to withstand practical use.

  Therefore, according to the zoom lens according to this example, it is possible to reduce the size of the zoom lens as having good lens characteristics.

  Next, a zoom lens according to Example 2 of the present invention will be described. FIG. 7 is a lens configuration diagram of a zoom lens according to Example 2. (a) shows the widest angle state, (b) shows the standard state, (c) shows the maximum telephoto state, and FIG. FIG. 9 is a graph showing spherical aberration, astigmatism, and distortion in the standard state of the zoom lens according to Example 2, and FIG. FIG. 4 is a lens configuration diagram of a zoom lens according to Example 3, wherein (a) shows the widest angle state, (b) shows the standard state, and (c) shows the maximum telephoto state.

The zoom lens according to the present embodiment has the following configuration.
r1 = ∞ d1 = 5.900 n1 = 1.78472 v1 = 25.7
r2 = ∞ d2 = 0.548 ~ 2.412 ~ 0.466
r3 = -91.380 d3 = 0.800 n2 = 1.71300 v2 = 53.9
r4 = 3.669 d4 = 0.020 n3 = 1.51313
v3 = 53.9
r5 ^* = 2.561 d5 = 0.870
r6 = 4.800 d6 = 1.82 n4 =
1.80610 v4 = 33.3
r7 = 21.487 d7 = 9.126-3.729-1.500
r8 ^* = 9.734 d8 = 2.020 n5 = l.58913
v5 = 61.2
r9 = -5.047 d9 = 0.100
r10 = 11.780 d10 = 2.090 n6 = 1.62041 v6 = 60.4
r11 = -4.394 d11 = 0.100
r12 = -6.052 d12 = 1.340 n7 = 1.69895 v7 = 30.0
r13 = 3.119 d13 = 3.517〜7.050〜11.224
r14 = 9.405 d14 = 3.000 n8 = 1.80518 v8 = 25.5
r15 = -16.258 d15 = 0.100
r16 = ∞ d16 = 0.800 n9 = 1.51680 v9 = 64.2
r17 = ∞

f = 4.15-7.69-11.87
F = 2.91 ~ 4.06 ~ 5.41
Angle of view = 67.6 ° to 38.2 ° to 25.4 °

Aspheric data 5th surface (r5 ^* )
A 0.0238
A4 0.551468E-03
A6 0.181852E-03
A8 0.337067E-04
A10 0.152721E-05
8th surface (r8 ^* )
A 18.6978
A4
-0.190435E-02
A6 0.492125E-03
A8 0.623006E-04
A10 0.138029E-04

f2 = 6.97 D = 5.65 D / f2 = 0.81

  That is, as shown in FIG. 7, the zoom lens according to this example is arranged as shown in (a) in the widest angle state, (b) in the standard state, and (c) in the maximum telephoto state. It is moved between states according to a predetermined cam curve similar to the predetermined cam curve shown in FIG.

  Then, the spherical aberration, the critical aberration, and the distortion shown in FIG. 8 in the widest angle state, in FIG. 9 in the standard state, and in FIG. 10 in the maximum telephoto state are obtained. These spherical aberrations, critical aberrations and distortions are excellent enough to withstand practical use.

  Therefore, according to the zoom lens according to this example, it is possible to reduce the size of the zoom lens as having good lens characteristics.

  11A and 11B are lens configuration diagrams of the zoom lens according to Example 3. FIG. 11A illustrates the widest angle state, FIG. 11B illustrates the standard state, FIG. 11C illustrates the maximum telephoto state, and FIG. FIG. 13 is a graph showing spherical aberration, astigmatism, and distortion in the standard state of the zoom lens according to Example 3, and FIG. 14 is a graph showing spherical aberration, astigmatism, and distortion in the standard state of the zoom lens according to Example 3. FIG. 6 is a graph showing spherical aberration, astigmatism, and distortion in the maximum telephoto state of the zoom lens according to Example 3;

The zoom lens according to the present embodiment has the following configuration.
r1 = ∞
d1 = 5.900
n1 = 1.78472
v 1 = 25.7
r2 = ∞
d2 = 0.548〜2.346〜0.464
r3 = -33.190 d3 = 0.820 n2 = 1.67790 v2 = 54.9
r4 ^* = 3.093 d4 = 0.970
r5 = 5.435 d5 = 2.020 n4 = 1.62004 v4 = 36.3
r6 = -96.557 d6 = 8.833 ~ 3.618 ~ 1.50
r7 ^* = 2.809 d7 = 2.470 n5 = 1.51633 v5 = 64.1
r8 = -9.808 d8 = 0.120
r9 ^* = 11.974 d9 = 2.700
r10 = -3.477 d10 = 0.200 n7 = 1.80610 v7 = 40.4
r11 = -2.573 d11 = 2.570
r12 = 6.125 d12 = 0.879-4.295-8.296
r13 = 9.073 d13 = 2.99 n8 = 1.76182 v8 = 26.6
r14 = -16.227 dl4 = 0.11
r15 = ∞
d15 = 1.00 n10 = 1.51680 v10 = 64.2
r16 = ∞

f = 4.58 ~ 8.55 ~ 13.202.
F = 3 ~ 4.32 ~ 5.94
Angle of view = 68.0 ° to 38.0 ° to 25.4 °

Aspheric dake fourth surface (r4 ^* )
A 0.5476
A4 0.157578E-02
A6 0.685253E-04
A8 0.454629E-06
A10 0.394742E-06
7th surface (r7 ^* )
A -1.6387
A4 0.143317E-01
A6 -0.850613E-03
A8
0.232605E-03
A10 -0.146094E-04

9th surface (r9 ^* )
A -8.6118
A4 -0.623431E-02
A6 -0.475627E-03
A8 -0.153647E-04
A10 0.000000E + 00

f2 = 6.653 D = 0.06 D / f2 = 1.21

  That is, as shown in FIG. 11, the zoom lens according to this example is arranged as shown in (a) in the widest angle state, (b) in the standard state, and (c) in the maximum telephoto state. It is moved between states according to a predetermined cam curve similar to the predetermined cam curve shown in FIG.

  Then, the spherical aberration, critical aberration, and distortion shown in FIG. 12 in the widest angle state, FIG. 13 in the standard state, and FIG. 14 in the maximum telephoto state are obtained. These spherical aberrations, critical aberrations and distortions are excellent enough to withstand practical use.

  Therefore, according to the zoom lens according to this example, it is possible to reduce the size of the zoom lens as having good lens characteristics.

  The zoom lens according to the present invention can be used as a low-power zoom lens for photographing such as a small, light, and thin digital camera and a mobile phone. Needless to say, it can be used as a low magnification zoom lens without a prism.

1 is a lens configuration of a zoom lens according to an embodiment. It is a cam diagram of the zoom lens according to the embodiment. FIG. 2 is a lens configuration diagram of a zoom lens according to Example 1, wherein (a) shows the widest angle state, (b) shows the standard state, and (c) shows the maximum telephoto state. 3 is a graph showing spherical aberration, astigmatism, and distortion in the widest angle state of the zoom lens according to Example 1; 3 is a graph showing spherical aberration, astigmatism, and distortion in the standard state of the zoom lens according to Example 1; 6 is a graph showing spherical aberration, astigmatism, and distortion in the maximum telephoto state of the zoom lens according to Example 1; FIG. 6 is a lens configuration diagram of a zoom lens according to Example 2, wherein (a) shows the widest angle state, (b) shows the standard state, and (c) shows the maximum telephoto state. 7 is a graph showing spherical aberration, astigmatism, and distortion in the widest angle state of the zoom lens according to Example 2; 6 is a graph showing spherical aberration, astigmatism, and distortion in a standard state of a zoom lens according to Example 2. 10 is a graph showing spherical aberration, astigmatism, and distortion in the maximum telephoto state of the zoom lens according to Example 2; FIG. 4 is a lens configuration diagram of a zoom lens according to Example 3, wherein (a) shows the widest angle state, (b) shows the standard state, and (c) shows the maximum telephoto state. 7 is a graph showing spherical aberration, astigmatism, and distortion in the widest angle state of the zoom lens according to Example 3; 10 is a graph showing spherical aberration, astigmatism, and distortion in a standard state of the zoom lens according to Example 3; 10 is a graph showing spherical aberration, astigmatism, and distortion in the maximum telephoto state of the zoom lens according to Example 3;

Explanation of symbols

L1 ... 1st lens group L2 ... 2nd lens group L3 ... 3rd lens group P ... Right angle prism Z ... Zoom lens

Claims (4)

A first lens group composed of a negative lens and a positive lens in order from the object side and having a negative optical power as a whole;
A second lens group composed of positive, positive and negative lenses and having positive optical power as a whole;
A third lens group having positive optical power,
By changing the air interval between the first lens group and the second lens group, and between the second lens group and the third lens group,
0.75 <D / f2 <1.25
R2B> 0
However,
f2: Focal length of the second lens group D: Full length of the second lens group R2B: A zoom lens having a radius of curvature of the rearmost surface of the second lens group. 2. The zoom according to claim 1, wherein the first group lens is disposed at substantially the same position on the most object side in the maximum wide-angle end state and the maximum telephoto end state, and is moved and zoomed on the image side. lens. A right-angle prism that bends the light beam by approximately 90 ° is disposed on the object side of the first lens group, and the air of the prism and the first lens group, the first lens group and the second lens group, and the second lens group and the third lens group. 3. The zoom lens according to claim 1, wherein the zoom lens is zoomed by changing the interval. 4. The zoom lens according to claim 1, wherein the zoom ratio is about 3.