JP2006119192A - Zoom lens and imaging apparatus equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a zoom lens constituted of comparatively fewer lenses, also, having a desired zooming ratio and high optical performance. <P>SOLUTION: Regarding the zoom lens constituted of, in order from an object side to an image side, a 1st lens group having negative refractive power, a 2nd lens group having positive refractive power, and a 3rd lens group having positive refractive power, wherein the 1st lens group and the 2nd lens group are shifted at zooming, the 1st lens group is constituted of two lenses, and provided that the focal distance of an i-th lens group is expressed by fi, the focal distance of the whole system at a wide angle end is expressed by fw, and the focal distance of the whole system at a telephoto end is expressed by ft, conditions of 1.5≤ft/fw, and 1.2<¾f1¾/f2<2.5 are satisfied. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a zoom lens, and more particularly to a zoom lens having a high optical performance and a very small size used in a small imaging device (for example, a digital still camera, a mobile phone, a PDA, etc.).

  2. Description of the Related Art In recent years, mobile devices such as mobile phones and PDAs are equipped with optical devices composed of an imaging module combined with a photographing lens and a solid-state imaging device such as a CCD or CMOS. In these optical devices, the overall thickness of the device has been reduced so as not to hinder portability, and the imaging module has also been reduced in thickness accordingly.

  Imaging modules, particularly imaging modules for mobile phones, are very frequently equipped with single-focus imaging lenses with a relatively small number of lenses that can be easily reduced in thickness.

  On the other hand, mobile phones equipped with an image sensor of 1 to 2 megapixels have been developed with higher image quality. On the other hand, there is a growing need for zoom lenses as photographing lenses. As a zoom lens compatible with such a small optical device, a negative lens preceding type (negative lead type) zoom lens system in which a negative lens is disposed on the object side has been proposed (Patent Documents 1 and 2).

  In Patent Document 1, in order from the object side to the image side, the distance between the first and second lens groups decreases in the three-group configuration including the lens groups having negative, positive, and positive refractive powers, and the second and third lens groups. A zoom lens composed of three lenses is disclosed as the entire system in which the first and second lens groups are moved so that the distance between them increases.

  In this way, the number of lenses is reduced, and the entire lens system is reduced in size.

  Further, the third lens group is configured with a positive refractive power that is fixed during zooming, thereby reducing the size of the entire lens system while lengthening the exit pupil.

  Further, Patent Document 2 discloses a zoom lens having a three-group configuration similar to Patent Document 1 that is composed of 5 to 6 lenses as a whole.

In the zoom lenses disclosed in Patent Documents 1 and 2, when the incident angle of the light beam to the image sensor is significantly deviated from the vertical incidence, vignetting is generated by the structure from the surface of the image sensor to the light receiving unit. Yes.
JP 2003-177314 A Japanese Patent Laid-Open No. 2004-4765

  In each of the embodiments of the zoom lens disclosed in Patent Document 1, it is difficult to cope with the above-described sensor having a megapixel or more in terms of optical performance.

  In addition, the lens performance in each example of Patent Document 2 corresponds to a megapixel sensor, but since it is designed on the assumption of a retractable camera, the total length of the lens as an optical system is long, such as a mobile phone or PDA. Miniaturization until it can be mounted on a portable terminal is not always sufficient.

  In the zoom lenses disclosed in Patent Documents 1 and 2, the optical performance can be improved by further increasing the number of constituent lenses.

  However, if the exit pupil is lengthened, the effective diameter of the lens system as a whole becomes close to the sensor size, and as a result, it is necessary to increase the thickness of the lens system, which in turn increases the overall length of the lens.

  In general, if the number of lenses in each lens group constituting the zoom lens is large, the length of each lens group on the optical axis becomes long, and if the amount of movement in zooming and focusing of each lens group is large, the total lens length becomes long. This makes it difficult to reduce the size of the entire lens system.

  An object of the present invention is to provide a zoom lens having a relatively small number of constituent lenses, a desired zoom ratio, and high optical performance, and an image pickup apparatus having the same.

  Another object of the present invention is to provide a zoom lens having a very short total lens length (miniaturized) and having high optical performance, and an image pickup apparatus using the same, corresponding to an image pickup device having megapixels or more.

The zoom lens according to the present invention includes, in order from the object side to the image side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power. At this time, in the zoom lens in which the first lens group and the second lens group move, the first lens group includes two lenses, and the focal length of the first lens group is f1, and the second lens group When the focal length is f2, and the focal lengths of the entire system at the wide-angle end and the telephoto end are fw and ft, respectively.
1.5 ≦ ft / fw
1.5 <| f1 | / f2 <2.5
It is characterized by satisfying the following conditions.

  According to the present invention, a zoom lens having a relatively small number of constituent lenses, a desired zoom ratio, and high optical performance can be obtained.

  Embodiments of the zoom lens of the present invention and an image pickup apparatus having the same will be described below.

  FIG. 1 is a lens cross-sectional view at the wide-angle end of the zoom lens according to Embodiment 1 of the present invention, and FIGS. 2 and 3 are aberration diagrams at the wide-angle end and telephoto end of the zoom lens according to Embodiment 1, respectively. Example 1 is a zoom lens having a zoom ratio of 1.88 and an aperture ratio of about 3.2 to 4.54.

  FIG. 4 is a lens cross-sectional view at the wide-angle end of the zoom lens according to Embodiment 2 of the present invention, and FIGS. 5 and 6 are aberration diagrams at the wide-angle end and telephoto end of the zoom lens according to Embodiment 2, respectively. The second embodiment is a zoom lens having a zoom ratio of 1.88 and an aperture ratio of about 3.50 to 5.04.

  FIG. 7 is a lens cross-sectional view at the wide-angle end of the zoom lens according to Embodiment 3 of the present invention, and FIGS. 8 and 9 are aberration diagrams at the wide-angle end and telephoto end of the zoom lens according to Embodiment 3, respectively. Example 3 is a zoom lens having a zoom ratio of 2 and an aperture ratio of about 3.00 to 4.48.

  FIG. 10 is a lens cross-sectional view at the wide-angle end of the zoom lens according to Embodiment 4 of the present invention. FIGS. 11 and 12 are aberration diagrams at the wide-angle end and telephoto end of the zoom lens according to Embodiment 4, respectively. The fourth exemplary embodiment is a zoom lens having a zoom ratio of 2 and an aperture ratio of about 3.72 to 5.70.

  FIG. 13 is a schematic view of a portable device having the zoom lens of the present invention.

  FIG. 14 is a schematic diagram of an imaging apparatus having the zoom lens of the present invention.

  The zoom lens of each embodiment is a photographing lens system used in an imaging apparatus (optical apparatus). In the lens cross-sectional view, the left side is the object side, and the right side is the image side.

  In the lens cross-sectional view, L1 is a first lens group having negative refractive power (optical power = reciprocal of focal length), L2 is a second lens group having positive refractive power, and L3 is a third lens group having positive refractive power. It is.

  SP is an aperture stop.

  G is an optical block corresponding to an optical filter, a face plate, a quartz low-pass filter, an infrared cut filter, or the like. IP is an image plane, and when used as a photographing optical system of a video camera or a digital still camera, a photosensitive surface corresponding to an imaging surface of a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor is placed.

  In the aberration diagrams, d and g are d-line and g-line, respectively, ΔM and ΔS are meridional image plane, sagittal image plane, and lateral chromatic aberration are represented by g-line.

  In each of the following embodiments, the wide-angle end and the telephoto end refer to zoom positions when the zoom lens unit (second lens unit L2) is positioned at both ends of the range in which it can move on the optical axis due to the mechanism.

  In each embodiment, in order from the object side to the image side, the first lens group having a negative refractive power, the second lens group having a positive refractive power, and the third lens group having a positive refractive power are provided. The first and second lens groups are moved.

  In particular, during zooming from the wide-angle end to the telephoto end, the first lens unit L1 moves so as to draw a convex locus on the image side, and the second lens unit L2 increases the distance from the third lens unit L3. Has moved to the object side.

  The first lens unit L1 is basically composed of two lenses, particularly a first lens having a negative refractive power and a second lens having a positive refractive power in order from the object side to the image side.

  By having three lens groups in this way, good optical performance capable of dealing with sensors of megapixels or more is obtained.

  In addition, by configuring the first lens unit L1 with only two lenses having negative and positive refractive powers, aberrations caused by decentration in the lens unit can be canceled relatively, and the sensitivity in the lens unit can be reduced. The entire system is reduced in size by reducing the number of lenses (5 or less as a whole).

In this embodiment, when the focal length at the telephoto end is ft, the focal length at the wide-angle end is fw, the focal length of the first lens unit L1 is f1, and the focal length of the second lens unit L2 is f2.
1.5 ≦ ft / fw (1)
1.5 <| f1 | / f2 <2.5 (2)
Is satisfied.

  Next, the technical contents of each conditional expression will be described.

  Conditional expression (1) and conditional expression (2) define the power (refractive power) of the entire lens system and the power arrangement of each lens group, and the power of the second lens group L2 that moves during zooming. By strengthening, the distance between the first and second lens groups is shortened to achieve downsizing of the entire lens system.

  Even if the conditional expression (1) is satisfied, if the lower limit of the conditional expression (2) is exceeded, the distance between the first lens unit L1 and the second lens unit L2 is increased in order to obtain a predetermined zoom ratio. Therefore, the total lens length at the wide-angle end becomes long. On the contrary, if the upper limit is exceeded, the tele ratio on the telephoto side increases, and the total lens length at the telephoto end increases.

More preferably, the numerical ranges of the conditional expressions (1) and (2) are set to 1.7 ≦ ft / fw (1a).
1.5 <| f1 | / f2 <2.3 (2a)
According to this, it becomes easy to obtain further downsizing of the entire lens system and high optical performance.

  As described above, in each embodiment, by satisfying conditional expressions (1) and (2), the entire lens system is reduced in size, and a zoom with a simple configuration in which the number of lenses is reduced while maintaining high optical performance. I have a lens.

The first lens unit L1 includes, in order from the object side to the image side, an eleventh lens G11 having a negative refractive power and a twelfth lens G12 having a positive refractive power. The curvature of the eleventh lens G11 on the object side and the image side is When the radii are R11 and R12, and the curvature radii of the object side and the image side of the twelfth lens G12 are R13 and R14, respectively.
1.0 <| R11 / R12 | (3)
| R13 / R14 | <1.2 (4)
Is satisfied.

  Conditional expressions (3) and (4) are expressions that define the radii of curvature of the lens surfaces of the two lenses used in the first lens unit L1, and deviate from conditional expressions (3) and (4). The power of the first lens unit L1 becomes weak and it is difficult to reduce the size of the entire lens system.

  More preferably, the numerical ranges of conditional expressions (3) and (4) are set as follows.

1.5 <| R11 / R12 | ... (3a)
| R13 / R14 | <1.0 (4a)
When the Abbe numbers of the materials of the eleventh lens G11 and the twelfth lens G12 are ν11 and ν12, respectively.
1.0 <ν11 / ν12 (5)
Is satisfied.

  Conditional expression (5) defines the Abbe number of the materials of the two lenses used in the first lens unit L1, and if it deviates from conditional expression (5), it is difficult to correct axial chromatic aberration. It is not preferable.

  More preferably, the numerical value of conditional expression (5) is set as follows.

1.1 <ν11 / ν12 (5a)
When the zoom lens in this embodiment is used as a photographic lens mounted on a portable terminal such as a mobile phone or a PDA, the lens barrel that holds the zoom lens is a type that does not retract. When expressed in mm, the back focus is 2.3 mm or less, and the distance from the lens surface closest to the object side of the first lens unit L1 to the sensor surface (imaging surface) is within 15 mm.

  When focusing from an object at infinity to an object at a short distance, the third lens unit L3 is moved backward. Note that focusing may be performed by moving other lens groups or the entire lens.

  Next, features of the zoom lens of each embodiment will be described sequentially.

  In the zoom lens of each embodiment, the first lens unit L1 having a negative refractive power, the second lens unit L2 having a positive refractive power, and the third lens unit L3 having a positive refractive power are sequentially arranged from the object side to the image side. The first lens unit L1 moves so as to draw a convex locus on the image side during zooming from the wide-angle end to the telephoto end, and the stop SP and the second lens unit L2 are on the object side. The third lens unit L3 is fixed or moved to the image plane side.

  The zoom lens of each embodiment performs main zooming by moving the second lens unit L2, and corrects movement of the image point accompanying zooming by moving a convex locus on the image side of the first lens unit L1. is doing. Further, the outer diameter of the lenses constituting the first lens unit L1 is increased by placing the stop SP on the most object side of the second lens unit L2 and reducing the distance between the entrance pupil on the wide angle side and the first lens unit L1. In addition, the first lens unit L1 and the third lens unit L3 cancel out various off-axis aberrations across the aperture stop SP disposed on the object side of the second lens unit L2, and it is good without increasing the number of constituent lenses. Has obtained excellent optical performance.

  In the zoom lens of each embodiment, the first lens unit L1 has one negative lens (a lens having a negative refractive power) and one positive lens (a lens having a positive refractive power). The entire lens system is composed of 5 or less lenses.

  In Example 1 of FIG. 1, it consists of five lenses as a whole.

  In order from the object side to the image side, the first lens unit L1 having a negative refractive power is composed of two lenses: a negative meniscus lens having a concave image side surface, and a positive meniscus lens having a convex object side surface. It is composed.

  In order from the object side to the image side, the second lens unit L2 having a positive refractive power is composed of a positive lens having a convex lens surface and a negative lens having a concave lens surface.

  The third lens unit L3 having a positive refractive power is constituted by a meniscus positive lens having a concave surface on the image side.

  In the second embodiment shown in FIG. 4, the lens is composed of five lenses as a whole.

  The first lens unit L1 having negative refractive power is composed of two lenses in order from the object side to the image side: a negative lens having a concave surface on the image side, and a positive lens having a convex meniscus shape on the object side. ing.

  In order from the object side to the image side, the second lens group having a positive refractive power is composed of a positive lens having convex lens surfaces and a negative lens having concave lens surfaces. Further, the third lens unit L3 having a positive refractive power is constituted by a positive lens having convex lens surfaces.

  In Example 3 shown in FIG. 7, the lens is composed of five lenses as a whole.

  In order from the object side to the image side, the first lens unit L1 having negative refractive power is composed of two lenses, a negative lens having a concave shape on both lens surfaces and a positive meniscus lens having a convex surface on the object side. Yes.

  In order from the object side to the image side, the second lens unit L2 having a positive refractive power is composed of a positive lens having a convex lens surface and a negative lens having a concave lens surface. Further, the third lens unit having a positive refractive power is constituted by a positive lens having convex both lens surfaces.

  In Example 4 of FIG. 10, it consists of four lenses as a whole.

  In order from the object side to the image side, the first lens unit L1 having a negative refractive power is composed of two lenses: a negative meniscus lens having a concave image side surface, and a positive meniscus lens having a convex object side surface. It is composed.

  The second lens unit L2 having a positive refractive power is constituted by a positive lens having convex lens surfaces. Further, the third lens unit L3 having a positive refractive power is constituted by a positive lens having convex lens surfaces.

  As described above, each lens group has a lens configuration that achieves both desired refractive power arrangement and aberration correction, thereby making the lens system compact while maintaining good optical performance.

  The first lens unit L1 has a role of forming an off-axis chief ray at the center of the stop SP and forms a pupil image at the center of the aperture stop SP. Aberration and distortion are likely to occur.

  Therefore, in each embodiment, the first lens unit L1 is composed of a negative lens and a positive lens that can suppress an increase in the effective lens diameter closest to the object side, as in a normal wide-angle lens system.

  By making the lens surface on the image side of the negative lens an aspherical surface, astigmatism and distortion are corrected in a well-balanced manner, and the first lens unit L1 is configured with a small number of two, and the entire lens is It is compact.

  Next, the second lens unit L2 has at least one positive lens whose both lens surfaces are convex, reduces the refraction angle of the off-axis chief ray emitted from the first lens unit L1, and has various off-axis aberrations. The shape does not occur. In addition, the positive lens has the highest height for passing on-axis rays, and is mainly involved in correction of spherical aberration and coma aberration.

  In each embodiment, the lens surface on the object side of the positive lens is preferably an aspherical surface. According to this, it becomes easy to satisfactorily correct spherical aberration and coma.

  In Examples 1 to 3, a negative lens is disposed on the image plane side of the positive lens, and axial chromatic aberration and lateral chromatic aberration that cannot be corrected only by the positive lens are corrected.

  Next, the third lens unit L3 includes a positive lens whose convex surfaces are convex or a meniscus positive lens whose concave surface on the image side is concave.

  In each embodiment, the object side surface of the positive lens has an aspherical shape, and thereby various off-axis aberrations in the entire zoom range are corrected favorably.

  As described above, according to each embodiment, the zoom lens includes three groups of negative, positive, and positive refractive power groups, and the refractive power of each lens group is set as described above even if the number of constituent lenses is small. As a result, a zoom lens having a good optical performance that can be applied to an image pickup device of megapixels or more while reducing the size of the entire lens system is achieved.

  Next, numerical examples of the present invention will be shown. In the numerical examples, i indicates the order from the object side, Ri is the radius of curvature of the i-th surface in order from the object side, Di is the i-th lens thickness and air spacing in order from the object side, and Ni and νi are respectively The refractive index and Abbe number at the d-line of the i-th material in order from the object side.

The aspherical shape is the X axis in the optical axis direction, the H axis in the direction perpendicular to the optical axis, the light traveling direction is positive, R is the paraxial radius of curvature, k is the eccentricity, and B, C, D, and E are not Spherical coefficient

It is expressed by the following formula.
For example, “e-Z” means “10 ^−Z ”. f indicates a focal length, Fno indicates an F number, and ω indicates a half angle of view.

Table 1 shows the relationship between the above-described conditional expressions and various numerical values in the numerical examples.
Numerical example 1

f = 3.80-7.15 Fno = 3.20-4.54 2ω = 63.2 °-34.9 °

R1 = 12.009 D1 = 0.50 N 1 = 1.530410 ν 1 = 56.0
R2 = 2.251 D2 = 0.54
R3 = 2.125 D3 = 0.95 N 2 = 1.859600 ν 2 = 40.4
R4 = 2.188 D4 = variable
R5 = Aperture D5 = 0.10
R6 = 1.98 D6 = 1.00 N 3 = 1.773470 ν 3 = 47.2
R7 = -4.16 D7 = 0.38
R8 = -7.251 D8 = 0.50 N 4 = 1.906808 ν 4 = 21.2
R9 = 2.344 D9 = variable
R10 = -311.442 D10 = 1.30 N 5 = 1.583060 ν 5 = 30.2
R11 = -3.144 D11 = 0.50
R12 = ∞ D12 = 0.70 N 6 = 1.516330 ν 6 = 64.1
R13 = ∞


\ Focal length 3.80 5.07 7.15
Variable interval \
D 4 2.89 1.51 0.30
D 9 1.21 1.94 3.15

Aspheric coefficient

R2 k = -1.83986e-01 B = 1.24001e-02 C = 2.19434e-03 D = 3.41949e-04
E = -1.95515e-05

R3 k = -4.15194e-01 B = 9.22038e-03 C = 1.94799e-04 D = 8.35231e-04
E = -1.13528e-04

R6 k = -1.25416e + 00 B = 6.00255e-03 C = -6.33555e-03 D = 2.80526e-03
E = -8.30079e-04

R9 k = 3.88096e + 00 B = 8.73855e-03 C = -5.27851e-02 D = 8.25766e-02
E = -8.04026e-02

R10 k = -2.10600e + 06 B = -4.49747e-03 C = 6.97414e-04 D = -1.15875e-04
E = 6.32031e-06

Numerical example 2

f = 3.80-7.14 Fno = 3.50-5.04 2ω = 63.3 °-34.8 °

R1 = 110.952 D1 = 0.50 N 1 = 1.524700 ν 1 = 56.2
R2 = 1.891 D2 = 0.43
R3 = 2.375 D3 = 0.95 N 2 = 1.882997 ν 2 = 40.8
R4 = 3.387 D4 = variable
R5 = Aperture D5 = 0.10
R6 = 2.152 D6 = 1.00 N 3 = 1.773770 ν 3 = 47.2
R7 = -4.522 D7 = 0.33
R8 = -12.838 D8 = 0.50 N 4 = 1.906808 ν 4 = 21.2
R9 = 2.421 D9 = variable
R10 = 10.891 D10 = 1.30 N 5 = 1.583060 ν 5 = 30.2
R11 = -6.131 D11 = 0.50
R12 = ∞ D12 = 0.70 N 6 = 1.516330 ν 6 = 64.1
R13 = ∞

\ Focal length 3.80 5.27 7.14
Variable interval \
D 4 2.79 1.31 0.30
D 9 1.34 2.44 3.83

Aspheric coefficient
R2 k = -4.71683e-02 B = -2.92201e-03 C = 7.77841e-04 D = -3.80306e-04
E = -1.76887e-04

R6 k = -1.09780e + 00 B = 2.33860e-03 C = -1.08221e-03 D = -4.54431e-03
E = 3.51702e-03

R9 k = 5.15712e-01 B = 2.52169e-02 C = -1.64825e-03 D = 1.99190e-02
E = -1.39614e-02

R10 k = 2.60279e + 00 B = -2.26755e-03 C = 9.18031e-04 D = -1.50534e-04
E = 9.98272e-06

Numerical example 3

f = 3.70-7.40 Fno = 3.00-4.48 2ω = 63.5 °-32.5 °

R1 = -17.954 D1 = 0.41 N 1 = 1.603112 ν 1 = 60.6
R2 = 1.998 D2 = 0.58
R3 = 3.768 D3 = 1.07 N 2 = 1.882997 ν 2 = 40.8
R4 = 12.046 D4 = variable
R5 = Aperture D5 = 0.10
R6 = 2.191 D6 = 1.35 N 3 = 1.743300 ν 3 = 49.3
R7 = -5.209 D7 = 0.15
R8 = -5.302 D8 = 0.70 N 4 = 1.846660 ν 4 = 23.8
R9 = 4.047 D9 = variable
R10 = 5.972 D10 = 0.80 N 5 = 1.583060 ν 5 = 30.2
R11 = -53.905 D11 = 0.30
R12 = ∞ D12 = 0.70 N 6 = 1.516330 ν 6 = 64.1
R13 = ∞

\ Focal length 3.70 5.48 7.40
Variable interval \
D 4 3.30 1.35 0.30
D 9 2.26 3.85 5.56

Aspheric coefficient
R2 k = -8.41865e-01 B = -4.08956e-03 C = 4.35229e-03 D = -1.66571e-03
E = 2.37998e-04

R6 k = -1.74139e + 00 B = 1.75496e-02 C = 1.66289e-03 D = -1.61387e-03
E = 4.92379e-04

R9 k = 5.56997e + 00 B = 2.77705e-02 C = -1.55451e-02 D = 2.96193e-02
E = -1.14081e-02

R10 k = -1.52784e + 00 B = -2.50682e-03 C = 3.04588e-04 D = 1.82816e-05
E = -4.46231e-06

Numerical example 4

f = 3.75 to 7.50 Fno = 3.72 to 5.70 2ω = 54.3 ° to 25.8 °

R1 = 4.797 D1 = 1.20 N 1 = 1.901355 ν 1 = 31.6
R2 = 2.334 D2 = 0.59
R3 = 3.600 D3 = 1.20 N 2 = 1.846660 ν 2 = 23.8
R4 = 4.900 D4 = variable
R5 = Aperture D5 = 0.15
R6 = 5.630 D6 = 0.85 N 3 = 1.487490 ν 3 = 70.2
R7 = -5.110 D7 = variable
R8 = 7.544 D8 = 0.97 N 4 = 1.487490 ν 4 = 70.2
R9 = -24.379 D9 = variable
R10 = ∞ D10 = 0.30 N 5 = 1.516330 ν 5 = 64.1
R11 = ∞

\ Focal length 3.75 5.12 7.50
Variable interval \
D 4 5.28 3.71 1.50
D 7 0.70 4.03 6.87
D 9 3.05 1.76 0.66

Aspheric coefficient

R2 k = -6.27185e-01 B = 5.08216e-03 C = 1.61761e-04 D = 2.61937e-05
E = 1.25814e-05

R6 k = -1.65518e + 01 B = -1.21900e-02 C = 1.16042e-01 D = -2.60088e-01
E = 2.08789e-01

R8 k = -1.97176e + 01 B = 9.91648e-06 C = 1.22098e-04 D = -5.96814e-05
E = -4.32276e-05

  Next, an embodiment of an image pickup apparatus using the zoom lens of the present invention will be described with reference to FIG.

  In FIG. 13, reference numeral 1 denotes a mobile phone body, and 2 denotes an image pickup module to which the zoom lens 4 of the present invention is attached. The image pickup module includes the zoom lens 4 and the image sensor 5. Reference numeral 6 denotes recording means for recording image data taken by the imaging module, and reference numeral 7 denotes a liquid crystal display unit for displaying a photographic image of the photographic subject at the time of shooting and reproduction.

  In this way, by applying the zoom lens of the present invention to a device such as a mobile phone, a small portable device capable of providing a high-quality image is realized.

  Next, an embodiment of a digital still camera (imaging device) using the zoom lens of the present invention as a photographing optical system will be described with reference to FIG.

  In FIG. 14, reference numeral 20 denotes a camera body, 21 denotes a photographing optical system constituted by the zoom lens of the present invention, 22 denotes a CCD sensor or CMOS sensor built in the camera body and receiving a subject image formed by the photographing optical system 21. A solid-state image pickup device (photoelectric conversion device) such as 23, a memory 23 for recording information corresponding to the subject image photoelectrically converted by the image pickup device 22, and a liquid crystal display panel 24 are formed on the solid-state image pickup device 22. This is a viewfinder for observing the subject image.

  Thus, by applying the zoom lens of the present invention to an image pickup apparatus such as a digital still camera, a small image pickup apparatus having high optical performance is realized.

Lens sectional view of Numerical Example 1 of the present invention Various aberrations at the wide angle end according to Numerical Example 1 of the present invention Various aberrations at the telephoto end according to Numerical Example 1 of the present invention Lens sectional view of Numerical Example 2 of the present invention Various aberrations at the wide angle end according to Numerical Example 2 of the present invention Various aberrations at the telephoto end according to Numerical Example 2 of the present invention Lens sectional view of Numerical Example 3 of the present invention Various aberrations at the wide angle end according to Numerical Embodiment 3 of the present invention Various aberrations at the telephoto end according to Numerical Example 3 of the present invention Lens sectional view of Numerical Example 4 of the present invention Various aberrations at the wide angle end according to Numerical Example 4 of the present invention Various aberrations at the telephoto end according to Numerical Example 4 of the present invention Schematic diagram of the main part of an embodiment of the optical apparatus of the present invention Schematic diagram of main parts of an embodiment of an imaging apparatus of the present invention

Explanation of symbols

L1 First lens unit L2 Second lens unit L3 Third lens unit SP Aperture IP Image surface d d line g g line ΔS Sagittal image surface ΔM Meridional image surface

Claims (9)

In order from the object side to the image side, the lens unit includes a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and a third lens unit having a positive refractive power. In the zoom lens in which the second lens group moves, the first lens group includes two lenses, the focal length of the first lens group is f1, the focal length of the second lens group is f2, and the wide-angle end. When the focal lengths of the entire system at the telephoto end are fw and ft, respectively.
1.5 ≦ ft / fw
1.5 <| f1 | / f2 <2.5
A zoom lens characterized by satisfying the following conditions:   The first lens group includes, in order from the object side to the image side, a first lens having a negative refractive power and a second lens having a positive refractive power, and the total number of lenses is five or less. The zoom lens according to claim 1.   The zoom lens from the wide-angle end to the telephoto end, wherein the first lens group moves to draw a convex locus on the image side, and the second lens group moves to the object side. 1 or 2 zoom lens.   4. The zoom lens according to claim 1, further comprising an aperture stop that moves integrally with the second lens group during zooming on the object side of the second lens group. The first lens group includes, in order from the object side to the image side, an eleventh lens G11 having a negative refractive power and a twelfth lens G12 having a positive refractive power.
When the object-side and image-side radii of curvature of the eleventh lens G11 are R11 and R12, respectively, and the object-side and image-side radii of curvature of the twelfth lens G12 are R13 and R14,
1.0 <| R11 / R12 |
| R13 / R14 | <1.2
The zoom lens according to claim 1, wherein the following condition is satisfied. When the Abbe numbers of the materials of the eleventh lens G11 and the twelfth lens G12 are ν11 and ν12, respectively.
1.0 <ν11 / ν12
The zoom lens according to claim 1, wherein the following condition is satisfied.   The zoom lens according to any one of claims 1 to 6, wherein a back focus at a wide angle end is 2.3 mm or less.   8. The zoom lens according to claim 1, wherein a distance from the first lens surface on the object side to the image surface is 15 mm or less.   An image pickup apparatus comprising: the zoom lens according to claim 1; and a solid-state image sensor that receives an image formed by the zoom lens.