JP2016161889A - Zoom lens and imaging apparatus including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zoom lens that excellently corrects a primary axial chromatic aberration and a secondary spectrum while increasing its diameter and that has high optical performance in an entire zoom range.SOLUTION: A zoom lens includes, in order from an object side to an image side, a first lens group L1 having negative refractive power and a second lens group L2 having positive refractive power, and changes a distance between the lens groups adjacent to each other during zooming operation. When νd2n represents an Abbe number of a material of a negative lens included in the second lens group L2 and θgF2n represents a partial dispersion ratio, the zoom lens satisfies the following conditional expressions: θgF2n<3.13×10×νd2n-1.86×10×νd2n+0.878, 5.0<νd2n<25.0.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a zoom lens, and is suitable for an imaging optical system of an imaging apparatus such as a digital still camera, a video camera, a TV camera, and a surveillance camera.

  With recent downsizing and higher functionality of imaging devices, the imaging optical system used for it has a wide angle of view (shooting angle of view) and is a small zoom lens with high optical performance with a large aperture ratio Is required. As a zoom lens having a small overall size, a wide angle of view, and a large aperture ratio, a negative lead type zoom lens in which a lens group having a negative refractive power precedes (most positioned on the object side) is known (Patent Document 1). , 2).

  In Patent Document 1, 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 one or more lens groups are provided, and an interval between the lens groups is changed. 3 group zoom lenses and 4 group zoom lenses that perform zooming are disclosed. Patent Document 1 discloses a zoom lens having a zoom ratio of about 2.8 and an F number of about 2.4 to 5.1 while being relatively compact.

  In Patent Document 2, a first zoom lens unit having a negative refractive power and a second lens unit having a positive refractive power are sequentially arranged from the object side to the image side, and zooming is performed by changing the distance between both lens units. Is disclosed. In addition, Patent Document 2 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 negative refractive power. A three-group zoom lens that performs zooming at different intervals is disclosed. Patent Document 2 discloses a zoom lens having a zoom ratio of 2.6 and an F number of about 3.7 to 6.9.

JP 2007-072263 A JP 2014006275 A

  In the negative lead type zoom lens described above, it is relatively easy to widen the angle of view and downsize the entire system. However, in the negative lead type zoom lens, the incident height of the axial ray is the highest in the second lens group in the entire zoom region. For this reason, a lot of primary axial chromatic aberration and secondary spectrum are generated from the second lens group. Therefore, in order to realize a large aperture and high image quality with a negative lead type zoom lens, it is necessary to appropriately set the lens configuration of the second lens group.

  If the lens configuration of the second lens group is inappropriate, it becomes very difficult to obtain high optical performance while reducing the size of the entire system and increasing the aperture ratio. The zoom lenses disclosed in Patent Documents 1 and 2 are all downsized. However, the lens configuration of the second lens group is not always appropriate. For this reason, when trying to increase the diameter, many primary axial chromatic aberrations and secondary spectra are generated, and it is difficult to obtain high optical performance over the entire zoom range.

  An object of the present invention is to provide a zoom lens having a high optical performance in the entire zoom range and an image pickup apparatus having the same, in which the primary axial chromatic aberration and the secondary spectrum are favorably corrected while increasing the diameter. .

The zoom lens of the present invention has a first lens group having a negative refractive power and a second lens group having a positive refractive power in order from the object side to the image side, and the distance between adjacent lens groups changes during zooming. In zoom lenses,
When the Abbe number of the material of the negative lens included in the second lens group is νd2n and the partial dispersion ratio is θgF2n, the second lens group is
θgF2n <3.13 × 10 ⁻⁴ × νd2n ² −1.86 × 10 ⁻² × νd2n + 0.878
5.0 <νd2n <25.0
It has a negative lens G2n that satisfies the following conditional expression.

  According to the present invention, it is possible to obtain a zoom lens having high optical performance over the entire zoom range by properly correcting the primary axial chromatic aberration and the secondary spectrum while increasing the diameter.

Cross-sectional view of a lens according to Example 1 of the present invention (A), (B), (C) Aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end of Embodiment 1 of the present invention. Lens sectional drawing of Example 2 of the present invention (A), (B), (C) Aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end of Embodiment 2 of the present invention. Lens sectional view of Example 3 of the present invention (A), (B), (C) Aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end of Embodiment 3 of the present invention. Lens sectional view of Example 4 of the present invention (A), (B), (C) Aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end of Embodiment 4 of the present invention. Lens sectional drawing of Example 5 of the present invention (A), (B), (C) Aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end of Embodiment 5 of the present invention. Explanatory diagram of the relationship between Abbe number νd and partial dispersion ratio θgF Schematic diagram of main parts of an imaging apparatus of the present invention

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The zoom lens according to the present invention includes a first lens group having a negative refractive power and a second lens group having a positive refractive power in order from the object side to the image side, and the distance between adjacent lens groups changes during zooming. There may be one or more lens groups that move during zooming on the image side of the second lens group.

  FIG. 1 is a lens cross-sectional view at the wide-angle end (short focal length end) of the zoom lens according to Embodiment 1 of the present invention. FIGS. 2A, 2B, and 2C are aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end (long focal length end), respectively, of the zoom lens according to the first exemplary embodiment. The first embodiment is a zoom lens having a zoom ratio of 2.85 and an F number (aperture ratio) of about 2.06 to 5.01.

  FIG. 3 is a lens cross-sectional view at the wide-angle end of the zoom lens according to Embodiment 2 of the present invention. 4A, 4B, and 4C are aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end, respectively, of the zoom lens according to the second embodiment. The second exemplary embodiment is a zoom lens having a zoom ratio of 2.76 and an F number of about 1.84 to 4.12.

  FIG. 5 is a lens cross-sectional view at the wide-angle end of the zoom lens according to Embodiment 3 of the present invention. FIGS. 6A, 6B, and 6C are aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end, respectively, of the zoom lens according to the third exemplary embodiment. The third embodiment is a zoom lens having a zoom ratio of 2.76 and an F number of about 1.84 to 4.12.

  FIG. 7 is a lens cross-sectional view at the wide-angle end of the zoom lens according to a fourth exemplary embodiment of the present invention. 8A, 8B, and 8C are aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end, respectively, of the zoom lens according to the fourth exemplary embodiment. The fourth embodiment is a zoom lens having a zoom ratio of 2.99 and an F number of about 2.06 to 4.90.

  FIG. 9 is a lens cross-sectional view at the wide-angle end of the zoom lens according to Embodiment 5 of the present invention. FIGS. 10A, 10B, and 10C are aberration diagrams of the zoom lens of Example 5 at the wide-angle end, the intermediate zoom position, and the telephoto end, respectively. Example 5 is a zoom lens having a zoom ratio of 1.90 and an F number of about 2.40 to 5.02.

  FIG. 11 is an explanatory diagram showing the relationship between the Abbe number νd of the material and the partial dispersion ratio. FIG. 12 is a schematic view of the main part of the imaging apparatus of the present invention. The zoom lens of each embodiment is an imaging optical system used in an imaging apparatus such as a video camera or a digital camera. In the lens cross-sectional view, the left side is the subject side (object side) (front), and the right side is the image side (rear).

  In the lens cross-sectional view, Li indicates the i-th lens group, and i indicates the order of the lens groups counted from the object side to the image side. SP is an F-number determining member (hereinafter referred to as “aperture stop”) that functions as an aperture stop that determines (limits) an open F-number (Fno) light beam. G is an optical block corresponding to an optical filter, a face plate, a crystal low-pass filter, an infrared cut filter, or the like. IP is an image plane, and when used as an imaging optical system of a video camera or a digital still camera, an imaging plane of a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor is placed.

  Further, when used as an imaging optical system for a silver salt film camera, a photosensitive surface corresponding to the film surface is provided. In the spherical aberration diagram, d represents d-line (wavelength 587.6 nm), and g represents g-line (wavelength 435.8 nm). In the astigmatism diagram, ΔM represents a d-line meridional image plane, and ΔS represents a d-line sagittal image plane. Distortion is represented by the d-line. The lateral chromatic aberration is represented by the g line. ω is a half angle of view (degree), and Fno is an F number. In the following embodiments, the wide-angle end and the telephoto end refer to zoom positions when the zoom lens unit is positioned at both ends of a range in which the mechanism can move on the optical axis.

  The zoom lens of each embodiment includes, in order from the object side to the image side, a first lens unit L1 having a negative refractive power and a second lens unit L2 having a positive refractive power. During zooming, the interval between adjacent lens groups changes.

The Abbe number of the negative lens material included in the second lens unit L2 is νd2n, and the partial dispersion ratio is θgF2n. At this time, the second lens unit L2 is
θgF2n <3.13 × 10 ⁻⁴ × νd2n ² −1.86 × 10 ⁻² × νd2n + 0.878 (1)
5.0 <νd2n <25.0 (2)
A negative lens G2n that satisfies the following conditional expression:

Note that the Abbe number νd and the partial dispersion ratio θgF of the material are Nd, NF, NC, and Ng, respectively, for the refractive index of the Fraunhofer line d, F, C, and g. At this time,
νd = (Nd−1) / (NF−NC)
θgF = (Ng−NF) / (NF−NC)
Defined by

  In general, in a negative lead type zoom lens, when trying to increase the diameter of the entire system while reducing the size of the entire system, in the second lens group that passes the highest axial light beam in the entire zoom region, the primary axis Many upper chromatic aberrations and secondary spectra occur. Therefore, in this second lens unit L2, in order to reduce the primary axial chromatic aberration and the secondary spectrum, the Abbe number and the partial dispersion ratio of the material for each lens constituting the second lens unit L2 are considered, It is important to select an appropriate material.

  Specifically, in the “θgF-νd diagram” shown in FIG. 11 (a graph in which the vertical axis represents the partial dispersion ratio θgF and the horizontal axis represents the Abbe number), the slope of the straight line connecting the materials of the positive lens and the negative lens is It is important to select the material of each lens constituting the second lens unit L2 so as to be loose.

  In the present invention, in the “θgF-νd diagram” of FIG. 11, the material in the region indicated by the solid line defined by the conditional expressions (1) and (2) is used as one or more negative members constituting the second lens unit L2. Used for one negative lens G2n of the lenses. As a result, the inclination with the positive lens is relaxed, and the primary axial chromatic aberration and the secondary spectrum are reduced. If the partial difference ratio of the material of the negative lens G2 of the second lens unit L2 exceeds the upper limit value of the conditional expression (1), the ability to correct the secondary spectrum on the telephoto side decreases, and the visible region Correction of chromatic aberration on the short wavelength side becomes insufficient, and color blurring occurs.

  If the Abbe number of the material of the negative lens G2n of the second lens unit L2 exceeds the upper limit value of the conditional expression (2), the dispersion becomes too small, and the first order generated in the second lens unit L2 It becomes difficult to correct axial chromatic aberration and spherical aberration in a balanced manner. If the Abbe number of the material of the negative lens G2n becomes smaller than the lower limit value of the conditional expression (2), the partial difference ratio of the material of the negative lens G2n becomes too large in the actual material, and the secondary spectrum is reduced. Difficult to do.

  By satisfying the above conditional expressions (1) and (2), the primary axial chromatic aberration and the secondary spectrum are corrected satisfactorily over the entire zoom range, and the entire system obtains a compact zoom lens. More preferably, it is preferable to set the numerical ranges of conditional expressions (1) and (2) as follows.

θgF2n <3.25 × 10 ⁻⁴ × νd2n ² −1.87 × 10 ⁻² × νd2n + 0.872 (1a)
10.0 <νd2n <24.0 (2a)
More preferably, the numerical ranges of the conditional expressions (1a) and (2a) are set as follows.
θgF2n <3.30 × 10 ⁻⁴ × νd2n ² −1.88 × 10 ⁻² × νd2n + 0.870 (1b)
15.0 <νd2n <24.0 (2b)

  By adopting the configuration as described above, in a negative lead type zoom lens, the primary axial chromatic aberration and the secondary spectrum are well corrected over the entire zoom range, and a small size and a large aperture ratio. Has got a zoom lens.

  In each embodiment, it is more preferable to satisfy one or more of the following conditional expressions. The focal length of the second lens unit L2 is f2, and the focal length of the entire system at the telephoto end is ft. Let the focal length of the negative lens G2n be f2n. The refractive index of the material of the negative lens G2n is Nd2n. The thickness on the optical axis of the negative lens G2n is D2n, and the distance on the optical axis from the most object-side lens surface vertex of the second lens unit L2 to the most image-side lens surface vertex is D2. The average value of the Abbe number of the material of the positive lens included in the second lens unit L2 is νd2p, and the average value of the partial dispersion ratio of the material of the positive lens included in the second lens unit L2 is θgF2p.

  The second lens group L2 has one or more positive lenses, and the average value of the refractive indexes of the materials of the positive lenses included in the second lens group L2 is Nd2p. Let the focal length of the first lens unit L1 be f1. The partial dispersion ratio of the material of the negative lens G1n included in the first lens unit L1 is θgF1n, and the Abbe number of the material of the negative lens G1n is νd1n. At this time, it is preferable to satisfy one or more of the following conditional expressions.

0.3 <f2 / ft <1.0 (3)
0.4 <| f2n / f2 | <1.0 (4)
1.750 <Nd2n <2.000 (5)
0.04 <D2n / D2 <0.50 (6)
-2.45 × 10 ⁻³ × νd2p + 0.590 <θgF2p (7)
35.0 <νd2p <50.0 (8)
1.800 <νd2p <2.000 (9)
0.8 <| f1 / f2 | <1.8 (10)
-2.40 × 10 ⁻³ × νd1n + 0.600 <θgF1n (11)

  Next, the technical meaning of each conditional expression described above will be described. If the positive refractive power of the second lens unit L2 is too weak beyond the upper limit of the conditional expression (3), if the magnification is changed to the desired focal length at the telephoto end, the amount of movement of the second lens unit L2 is as follows. The lens length increases and the total lens length increases. When the positive refractive power of the second lens unit L2 is too strong beyond the lower limit, the primary axial chromatic aberration and the secondary spectrum increase on the telephoto side, and it becomes difficult to correct them well.

  If the upper limit of conditional expression (4) is exceeded and the negative refractive power of the negative lens G2n becomes too weak (the absolute value of the negative refractive power becomes small), the primary axial chromatic aberration will be undercorrected. If the lower limit of conditional expression (4) is exceeded and the negative refractive power of the negative lens G2n becomes too strong (the absolute value of the negative refractive power increases), the occurrence of spherical aberration and coma increases in the entire zoom range. Come.

  If the upper limit of conditional expression (5) is exceeded and the material of the negative lens G2n has a high refractive index, the curvature of the lens surface of the negative lens G2n becomes too loose, and correction of spherical aberration is insufficient particularly on the wide angle side. To do. If the material of the negative lens G2n has a low refractive index exceeding the lower limit of the conditional expression (5), the negative lens lens is used to share the refractive power of the negative lens necessary for correcting the first-order axial chromatic aberration. The curvature of the surface becomes too tight. As a result, a lot of astigmatism occurs in the entire zoom region.

  If the upper limit of conditional expression (6) is exceeded and the thickness (center thickness) of the negative lens G2n becomes too thick, it becomes difficult to shorten the total lens length. If the thickness of the negative lens G2n becomes too thin beyond the lower limit of the conditional expression (6), the negative lens G2n may be used to share the refractive power of the negative lens G2n necessary for correcting the primary axial chromatic aberration. The curvature of the lens surface on the image side becomes too tight. As a result, a lot of astigmatism occurs in the entire zoom region.

  If the average value of the partial difference ratios of the materials of the positive lenses constituting the second lens unit L2 is reduced beyond the lower limit value of the conditional expression (7), a large secondary spectrum is generated on the telephoto side. Correction on the short wavelength side in the visible range becomes insufficient, and color blurring occurs greatly.

  If the average value of the Abbe number increases beyond the upper limit value of conditional expression (8), the average value of the partial fraction ratio of the positive lens material becomes too small in the actual material, and the secondary spectrum is corrected. It becomes difficult. If the lower limit of conditional expression (8) is exceeded and the average value of the Abbe number becomes small, the dispersion of the material of the positive lens included in the second lens unit L2 becomes too large and occurs in the second lens unit L2. It becomes difficult to correct the primary axial chromatic aberration.

  If the conditional expression (9) exceeds the upper limit and the average value of the refractive index of the positive lens material becomes large and the refractive index becomes high, the dispersion becomes too large in the existing material, and the primary axial chromatic aberration is reduced. It becomes difficult to correct. If the lower limit of conditional expression (9) is exceeded and the average value of the refractive index of the positive lens material becomes small and the refractive index becomes low, the curvature of the lens surface of the positive lens becomes too tight and spherical aberration occurs in the entire zoom range. A lot happens. In general, in a negative lead type zoom lens, the first lens unit L1 is configured to correct a secondary spectrum of axial chromatic aberration with respect to the second lens unit L2.

  When the upper limit of conditional expression (10) is exceeded, the negative refractive power of the first lens unit L1 becomes too weak, and the effect of correcting the secondary spectrum generated in the second lens unit L2 becomes insufficient. When the lower limit of conditional expression (10) is exceeded, the negative refractive power of the first lens unit L1 becomes too strong, and it becomes difficult to correct curvature of field, particularly on the wide angle side. If the lower limit of conditional expression (11) is exceeded and the partial fraction ratio of the material of the negative lens G1n constituting the first lens unit L1 becomes small, it becomes difficult to correct the secondary spectrum on the telephoto side, and the visible region The correction of chromatic aberration on the short wavelength side becomes insufficient, resulting in a large amount of color blurring.

  More preferably, in order to increase the effect of the embodiment, it is preferable to set the numerical ranges of the conditional expressions (3) to (11) as follows.

0.4 <f2 / ft <0.8 (3a)
0.45 <| f2n / f2 | <0.96 (4a)
1.780 <Nd2n <1.950 (5a)
0.04 <D2n / D2 <0.20 (6a)
-2.60 × 10 ⁻³ × νd2p + 0.640 <θgF2p (7a)
35.0 <νd2p <45.0 (8a)
1.840 <νd2p <1.900 (9a)
0.9 <| f1 / f2 | <1.6 (10a)
-2.80 × 10 ⁻³ × νd1n + 0.660 <θgF1n (11a)

  The zoom lens according to the present invention includes, in order from the object side to the image side, a first lens unit L1 having a negative refractive power and a second lens unit L2 having a positive refractive power. The first lens unit L1 and the second lens unit L2 have a positive refractive power during zooming. The lens unit L2 moves along different trajectories. The zoom locus of each lens group of the zoom lens of each embodiment is such that the lens group moves so that the distance between the first lens group L1 and the second lens group L2 is narrower at the telephoto end than at the wide angle end during zooming. ing. Furthermore, the second lens unit L2 is located on the object side at the telephoto end compared to the wide-angle end. In each embodiment, these configurations are the basic configurations. The following embodiment is taken under the basic configuration.

  A third lens unit L3 having a positive refractive power is provided on the image side of the second lens unit L2, and the third lens unit L3 moves along a locus different from other lens units during zooming. An image side of the second lens unit L2, which includes a third lens unit L3 having a positive refractive power and a fourth lens unit L4 having a positive refractive power in order from the object side to the image side. Both L3 and the fourth lens unit L4 move along different trajectories from the other lens units.

  An image side of the second lens unit L2, which includes a third lens unit L3 having a negative refractive power and a fourth lens unit L4 having a positive refractive power in order from the object side to the image side, and the third lens unit during zooming Both L3 and the fourth lens unit L4 move along different trajectories from the other lens units.

  Next, a specific lens configuration of each embodiment will be described. In the zoom lens of Example 1, 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. This is a three-group zoom lens composed of two lens groups. During zooming from the wide-angle end to the telephoto end, as indicated by an arrow in the lens cross-sectional view, the first lens unit L1 moves along a locus convex toward the image side, the second lens unit L2 moves toward the object side, The three lens unit L3 moves to the image side.

  The aperture stop SP moves to the object side along a different path from the other lens groups. The zoom lens of Example 1 performs main zooming by moving the second lens unit L2, and corrects the movement of the image plane accompanying zooming by moving a convex locus on the image side of the first lens unit L1. ing. Further, telecentric imaging on the image side necessary for a photographing apparatus using a solid-state imaging device or the like is achieved by making the third lens unit L3 serve as a field lens.

  In Example 1, the first lens unit L1 having a negative refractive power is sequentially arranged from the object side to the image side, the negative lens 11 (G1n) having a concave surface on the image side, and a positive meniscus shape having a convex surface on the object side. The lens 12 is composed of two lenses. In the negative lens 11 of the first lens unit L1, both the object-side lens surface and the image-side lens surface are aspherical.

  In the first lens unit L1 configured in this way, by sufficiently taking the difference in Abbe number between the materials of the negative lens 11 and the positive lens 12, the primary axial chromatic aberration at the telephoto end and the lateral chromatic aberration at the wide angle end are improved. It is corrected. Further, by increasing the partial dispersion ratio of the material used for the negative lens 11, the secondary spectrum of axial chromatic aberration is corrected well in the entire zoom region. The second lens unit L2 is configured as follows in order from the object side to the image side.

  A positive lens 21 having a convex surface facing the object side, a cemented lens 24 having a positive lens 22 having a convex surface facing the object side, and a negative lens 23 (G2n) having a concave surface facing the image surface side, a negative lens 25 and a positive lens 26 and a cemented lens 27 that is cemented with the lens 26. By using an aspherical lens surface for the positive lens 21 arranged on the most object side, spherical aberration and coma are corrected well. In the second lens unit L2 configured as described above, by applying a material having a high dispersion and a small partial dispersion ratio that satisfies the conditional expressions (1) and (2) to the negative lens 23 (G2n), The primary axial chromatic aberration and the secondary spectrum are reduced in the zoom region.

  As a material of the negative lens 23 (G2n) satisfying the above characteristics, for example, there is a glass material containing a lot of SnO, which is disclosed in Japanese Patent Application Laid-Open No. 2012-193065. However, the material that can be used in this embodiment is not limited to the embodiment disclosed in the above-mentioned document, and any material that satisfies the conditional expressions (1) and (2) may be used.

  Further, by sharing the positive refractive power of the second lens unit L2 between the positive lens 21 and the positive lens 22, primary axial chromatic aberration and spherical aberration are reduced in the entire zoom region. In addition, the configuration including the two cemented lenses 24 and the cemented lens 27 favorably corrects the primary axial chromatic aberration and the secondary spectrum at the telephoto end. The third lens unit L3 includes a single positive lens 31. As a result, the entire lens system is thinned, and the small and lightweight third lens unit L3 is moved in the optical axis direction to facilitate rapid focusing.

  The zoom lens of the second embodiment has the same zoom type as the first embodiment, such as the number of lens groups, the sign of the refractive power of each lens group, and the movement locus of each lens group during zooming. In Example 2, the first lens unit L1 having negative refractive power is arranged in order from the object side by a negative lens 11 (G1n) having a concave surface facing the image side, a negative lens 12, and a positive lens 13 having a convex surface facing the object side. It is composed. The lens surface on the object side and the lens surface on the image side of the negative lens 11 are aspherical.

  In Example 2, the negative refractive power of the first lens unit L1 is shared by the two negative lenses 11 and 12, thereby reducing the first-order axial chromatic aberration and the chromatic aberration of magnification at the wide-angle end at the telephoto end. Yes. The lens configuration of the second lens unit L2 is the same as that of the first embodiment. The lens configuration of the third lens unit L3 is the same as that of the first embodiment.

  The zoom lens according to the third exemplary embodiment includes, in order from the object side to the image side, a first lens unit L1 having a negative refractive power, a second lens unit L2 having a positive refractive power, a third lens unit L3 having a positive refractive power, and a positive lens unit. This is a zoom lens having a four-group configuration including a fourth lens unit L4 having refractive power. When zooming from the wide-angle end to the telephoto end, each lens unit moves as indicated by an arrow. Specifically, during zooming from the wide-angle end to the telephoto end, the first lens unit L1 moves along a locus convex to the image side, the second lens unit L2 moves to the object side, and the third lens unit L3 moves to the object side. Move to. The fourth lens unit L4 moves to the image side.

  In the third exemplary embodiment, the first lens unit L1 having negative refractive power includes, in order from the object side, a negative lens 11 (G1n) having a concave surface facing the image side, a negative lens 12, and a positive lens 13 having a convex surface facing the object side. doing. The lens surface on the object side and the lens surface on the image side of the negative lens 11 are aspherical. In Embodiment 3, the negative refractive power of the first lens unit L1 is shared by the two negative lenses 11 and 12, thereby reducing the first-order axial chromatic aberration and the chromatic aberration of magnification at the wide-angle end at the telephoto end. .

  In Example 3, the second lens unit L2 includes, in order from the object side, a positive lens 21 having a convex surface facing the object side, and a cemented lens 24 in which a positive lens 22 and a negative lens 23 (G2n) are cemented. In the second lens unit L2 configured as described above, by applying a material having a high dispersion and a small partial dispersion ratio that satisfies the conditional expressions (1) and (2) to the negative lens 23 (G2n), The primary axial chromatic aberration and the secondary spectrum are reduced in the zoom region. As a material of the negative lens 23 satisfying the above characteristics, for example, there is a glass material containing a lot of SnO, which is disclosed in JP 2012-193065 A.

  However, the material that can be used in this embodiment is not limited to the embodiment disclosed in the above-mentioned document, and any material that satisfies the conditional expressions (1) and (2) may be used. Further, by sharing the positive refractive power of the second lens unit L2 between the positive lens 21 and the positive lens 22, primary axial chromatic aberration and spherical aberration are reduced in the entire zoom region.

  In the third exemplary embodiment, the third lens unit L3 includes a cemented lens 33 in which a negative lens 31 and a positive lens 32 are cemented in order from the object side to the image side. By configuring the third lens unit L3 with the cemented lens 33, primary axial chromatic aberration and secondary spectrum that occur when the third lens unit L3 shares the variable magnification are reduced. In the third exemplary embodiment, the fourth lens unit L4 includes one positive lens 41. With this configuration, when focusing is performed by the fourth lens unit L4, the lens group to be driven can be reduced in weight, so that quick focusing is facilitated.

  The zoom lens according to the fourth exemplary embodiment includes, in order from the object side to the image side, a first lens unit L1 having a negative refractive power, a second lens unit L2 having a positive refractive power, a third lens unit L3 having a negative refractive power, and a positive lens unit. This is a zoom lens having a four-group configuration including a fourth lens unit L4 having refractive power. When zooming from the wide-angle end to the telephoto end, each lens unit moves as indicated by an arrow. Specifically, during zooming from the wide-angle end to the telephoto end, the first lens unit L1 moves along a convex locus toward the image side, the second lens unit L2 moves toward the object side, and the third lens unit L3 moves toward the object side. Move to the side. The fourth lens unit L4 moves to the image side.

  In Example 4, the lens configuration of the first lens unit L1 having negative refractive power is the same as that of Example 1. In Example 4, the second lens unit L2 is composed of, in order from the object side, a positive lens 21 having a convex surface facing the object side, a cemented lens 24 in which a positive lens 22 and a negative lens 23 (G2n) are cemented, and a positive lens 25. Yes. In the second lens unit L2 configured as described above, by applying a material having a high dispersion and a small partial dispersion ratio that satisfies the conditional expressions (1) and (2) to the negative lens 23 (G2n), The primary axial chromatic aberration and the secondary spectrum are reduced in the zoom region.

  As a material of the negative lens 23 (G2n) satisfying the above characteristics, for example, there is a glass material containing a lot of SnO, which is disclosed in Japanese Patent Application Laid-Open No. 2012-193065. However, the material that can be used in this embodiment is not limited to the embodiment disclosed in the above-mentioned document, and any material that satisfies the conditional expressions (1) and (2) may be used. Further, by sharing the positive refractive power of the second lens unit L2 between the positive lens 21 and the positive lens 22, primary axial chromatic aberration and spherical aberration are reduced in the entire zoom region.

  In the fourth embodiment, the third lens unit L3 includes one negative lens 31. By using a single lens, when the focusing is performed by the third lens unit L3, the lens group to be driven can be reduced in weight, so that quick focusing is facilitated. In the fourth embodiment, the fourth lens unit L4 includes one positive lens 41. With this configuration, when focusing is performed by the fourth lens unit L4, the lens group to be driven can be reduced in weight, so that quick focusing is facilitated.

  The zoom lens of Example 5 is a two-group zoom lens including two lens groups, a first lens unit L1 having a negative refractive power and a second lens unit L2 having a positive refractive power, in order from the object side to the image side. It is. During zooming from the wide-angle end to the telephoto end, the first lens unit L1 moves to the image side and the second lens unit L2 moves to the object side, as indicated by the arrows in the lens sectional view. The aperture stop SP moves integrally (same locus) with the second lens unit L2.

  The zoom lens according to the fifth exemplary embodiment performs main zooming by moving the second lens unit L2, and corrects the movement of the image plane accompanying zooming by moving the first lens unit L1 toward the image side. In Example 5, the lens configuration of the first lens unit L1 having negative refractive power is the same as that of Example 1. In Example 5, the lens configuration of the second lens unit L2 is the same as that of Example 1.

  In each embodiment, image blur correction may be performed by moving an arbitrary lens group in a direction perpendicular to the optical axis. Furthermore, the zoom lens of each embodiment may be used in combination with a system having a correction unit that corrects an electric signal including distortion and lateral chromatic aberration by image processing. According to this, it becomes easy to obtain higher performance in the entire zoom region.

  Next, an embodiment of a digital camera (optical apparatus) using the zoom lens of the present invention as an imaging optical system will be described with reference to FIG. In FIG. 12, reference numeral 20 denotes a digital camera body, 21 denotes an image pickup optical system constituted by the zoom lens of the above-described embodiment, and 22 denotes an image pickup element such as a CCD for receiving a subject image formed by the image pickup optical system 21. Reference numeral 23 denotes recording means for recording a subject image received by the image sensor 22. Reference numeral 24 denotes a liquid crystal display panel having a function equivalent to that of the viewfinder.

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

  Next, numerical data of each embodiment of the present invention will be shown. In the numerical data of each embodiment, i indicates the order of the surfaces from the object side. ri is the radius of curvature of the lens surface, and di is the lens thickness and the air spacing between the i-th surface and the (i + 1) -th surface. ndi and νdi indicate the refractive index and Abbe number of the material of the i-th optical member with respect to the d-line, respectively. The two surfaces closest to the image side are filter members such as a crystal low-pass filter and an infrared cut filter.

  A portion where the distance d is variable changes during zooming, and indicates the surface distance corresponding to each zoom position. 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 conic constant, A4, A6, A8, A10, A12 Are respectively aspherical coefficients,

It is expressed by the following formula. [E + X] means [× 10 ^{+ x} ], and [e−X] means [× 10 ^−x ]. An aspherical surface is indicated by adding * after the surface number. BF denotes a back focus, which indicates an air conversion length from the final lens surface to the paraxial image surface. The total lens length is a value obtained by adding the back focus BF to the distance from the first lens surface to the final lens surface. Table 1 shows the relationship between the above-described conditional expressions and the respective examples.

[Example 1]
Unit mm

Surface data surface number rd nd νd θgF
1 * -74.810 1.00 1.88202 37.2 0.5769
2 * 12.304 2.50
3 21.016 1.80 2.00272 19.3
4 68.940 (variable)
5 (Aperture) ∞ (Variable)
6 * 11.417 2.58 1.85135 40.1 0.5694
7 * 566.870 0.20
8 13.104 2.44 1.91082 35.3 0.5820
9 665.118 0.45 1.84660 20.6 0.6176
10 6.820 1.98
11 -18.234 0.45 1.69895 30.1
12 83.932 1.39 1.91082 35.3 0.5820
13 -18.038 (variable)
14 48.372 2.80 1.62263 58.2
15 * -32.158 (variable)
16 ∞ 1.09 1.51633 64.1
17 ∞ 1.62
Image plane ∞

Aspheric data 1st surface
K = 0.00000e + 000 A 4 = -1.31035e-004 A 6 = 3.17018e-006
A 8 = -3.99693e-008 A10 = 2.43555e-010 A12 = -5.38672e-013

Second side
K = 0.00000e + 000 A 4 = -1.84487e-004 A 6 = 2.04387e-006
A 8 = 1.98076e-009 A10 = -5.23095e-010 A12 = 4.11098e-012

6th page
K = 5.07382e-001 A 4 = -9.78557e-005 A 6 = -1.79538e-007
A 8 = 4.09380e-010

7th page
K = -1.00000e + 001 A 4 = 3.05647e-005 A 6 = 9.16099e-007

15th page
K = 0.00000e + 000 A 4 = 4.12200e-005 A 6 = -7.26104e-007
A 8 = 8.64422e-009 A10 = -4.49816e-011

Various data Zoom ratio 2.85
Wide angle Medium telephoto focal length 10.50 19.76 29.90
F number 2.06 4.30 5.01
Half angle of view (degrees) 31.44 21.76 14.78
Image height 6.42 7.89 7.89
Total lens length 52.34 49.73 53.96
BF 7.48 5.72 5.08
d 4 17.80 6.88 1.47
d 5 1.17 0.10 0.37
d13 8.30 19.42 29.44
d15 5.14 3.38 2.74

Zoom lens group data group Start surface Focal length
1 1 -22.76
2 6 17.42
3 14 31.44

[Example 2]
Unit mm

Surface data surface number rd nd νd θgF
1 * -1299.825 1.00 1.88202 37.2 0.5769
2 * 10.675 3.00
3 -58.255 0.70 1.74950 35.3
4 80.517 0.10
5 22.989 1.80 2.00272 19.3
6 703.838 (variable)
7 (Aperture) ∞ (Variable)
8 * 11.235 2.58 1.85135 40.1 0.5694
9 * 9212.623 0.20
10 14.374 2.61 1.88300 40.8 0.5667
11 191.876 0.45 1.84660 20.6 0.6176
12 7.327 2.00
13 -20.321 0.45 1.69895 30.1
14 146.668 1.30 1.88300 40.8 0.5667
15 -15.452 (variable)
16 70.335 2.80 1.61881 63.9
17 * -25.129 (variable)
18 ∞ 1.09 1.51633 64.1
19 ∞ 1.61
Image plane ∞

Aspheric data 1st surface
K = 0.00000e + 000 A 4 = -1.88697e-004 A 6 = 5.38456e-006
A 8 = -8.70216e-008 A10 = 6.97310e-010 A12 = -2.15175e-012

Second side
K = 0.00000e + 000 A 4 = -2.58335e-004 A 6 = 4.13420e-006
A 8 = -2.33276e-008 A10 = -9.66651e-010 A12 = 1.08137e-011

8th page
K = 4.53532e-001 A 4 = -8.78812e-005 A 6 = 5.53448e-008
A 8 = -1.97789e-009

9th page
K = -1.00000e + 001 A 4 = 7.44979e-005 A 6 = 8.48773e-007

17th page
K = 0.00000e + 000 A 4 = 9.51153e-005 A 6 = -1.13219e-006
A 8 = 1.51831e-008 A10 = -9.00104e-011

Various data Zoom ratio 2.76
Wide angle Medium telephoto focal length 9.00 16.39 24.80
F number 1.84 3.60 4.12
Half angle of view (degrees) 47.84 47.76 52.59
Image height 6.42 7.89 7.89
Total lens length 48.21 48.13 52.96
BF 7.94 6.15 5.07
d 6 12.54 4.80 1.50
d 7 2.00 0.77 0.00
d15 6.35 17.04 27.01
d17 5.61 3.82 2.74

Zoom lens group data group Start surface Focal length
1 1 -17.67
2 8 15.60
3 16 30.26

[Example 3]
Unit mm

Surface data surface number rd nd νd θgF
1 * -921.116 1.00 1.88202 37.2 0.5769
2 * 10.772 2.94
3 -73.904 0.70 1.74950 35.3
4 62.293 0.10
5 21.516 1.80 2.00272 19.3
6 273.146 (variable)
7 (Aperture) ∞ (Variable)
8 * 11.312 2.58 1.85135 40.1 0.5694
9 * -437.778 0.20
10 14.296 2.61 1.88300 40.8 0.5667
11 165.512 0.45 1.84660 20.6 0.6176
12 7.168 (variable)
13 -20.700 0.45 1.69895 30.1
14 72.796 1.30 1.88300 40.8
15 -15.960 (variable)
16 70.431 2.80 1.62263 58.2
17 * -25.396 (variable)
18 ∞ 1.09 1.51633 64.1
19 ∞ 1.62
Image plane ∞

Aspheric data 1st surface
K = 0.00000e + 000 A 4 = -1.26843e-004 A 6 = 3.75715e-006
A 8 = -6.69432e-008 A10 = 5.82497e-010 A12 = -1.95114e-012

Second side
K = 0.00000e + 000 A 4 = -1.88440e-004 A 6 = 2.95368e-006
A 8 = -3.61203e-008 A10 = -3.76447e-010 A12 = 5.95576e-012

8th page
K = 4.97319e-001 A 4 = -1.00049e-004 A 6 = -4.88905e-007
A 8 = -7.25249e-009

9th page
K = 7.35455e + 000 A 4 = 6.02975e-005 A 6 = 8.03110e-008

17th page
K = 0.00000e + 000 A 4 = 8.86513e-005 A 6 = -1.03267e-006
A 8 = 1.44677e-008 A10 = -8.76642e-011

Various data Zoom ratio 2.76
Wide angle Medium telephoto focal length 9.00 16.34 24.80
F number 1.84 3.60 4.12
Half angle of view (degrees) 35.50 25.78 17.65
Image height 6.42 7.89 7.89
Total lens length 48.32 47.98 52.56
BF 8.10 6.19 5.08
d 6 12.90 4.93 1.50
d 7 2.00 0.80 -0.00
d12 3.00 2.87 2.74
d15 5.38 16.24 26.29
d17 5.76 3.85 2.74

Zoom lens group data group Start surface Focal length
1 1 -18.00
2 8 19.01
3 13 38.76
4 16 30.32

[Example 4]
Unit mm
Surface data

Surface number rd nd νd θgF
1 * -93.593 1.10 1.85135 40.1 0.5694
2 * 10.922 2.61
3 17.313 2.04 2.00272 19.3
4 37.765 (variable)
5 (Aperture) ∞ (Variable)
6 * 12.096 2.54 1.85135 40.1 0.5694
7 * 432.172 0.20
8 10.936 2.76 1.83481 42.7 0.5416
9 -31.934 0.50 1.78490 23.5 0.6090
10 6.544 1.91
11 -300.000 1.10 1.61881 63.9
12 * -35.000 (variable)
13 -16.295 0.50 1.64769 33.8
14 -35.487 (variable)
15 36.376 3.45 1.85 135 40.1
16 * -29.937 (variable)
17 ∞ 1.09 1.51633 64.1
18 ∞ 1.63
Image plane ∞

Aspheric data 1st surface
K = 0.00000e + 000 A 4 = -7.00362e-005 A 6 = 2.26682e-006
A 8 = -3.40144e-008 A10 = 2.41101e-010 A12 = -6.47175e-013

Second side
K = 6.92278e-002 A 4 = -1.22860e-004 A 6 = 1.20708e-006
A 8 = 3.45833e-009 A10 = -5.82879e-010 A12 = 2.52066e-012
A14 = 6.28919e-014 A16 = -5.17193e-016

6th page
K = -3.19318e-001 A 4 = -3.14813e-005 A 6 = 6.54280e-007
A 8 = -1.82134e-008

7th page
K = 8.74893e-001 A 4 = 7.22497e-006 A 6 = 8.31295e-007
A 8 = -2.62312e-008

12th page
K = -1.48440e + 001 A 4 = 3.32874e-005 A 6 = 3.82315e-006
A 8 = 2.55770e-008

16th page
K = -9.41891e-001 A 4 = 3.20807e-005 A 6 = -1.49417e-007
A 8 = 3.33298e-010

Various data Zoom ratio 2.99
Wide angle Medium Telephoto focal length 10.00 19.35 29.90
F number 2.06 3.65 4.90
Half angle of view (degrees) 33.53 22.20 14.80
Image height 6.63 7.90 7.90
Total lens length 49.85 47.36 51.84
BF 6.31 6.12 5.92
d 4 17.41 5.24 1.47
d 5 0.10 0.86 0.18
d12 4.12 8.87 14.16
d14 3.20 7.58 11.41
d16 3.96 3.77 3.57

Zoom lens group data group Start surface Focal length
1 1 -20.32
2 6 14.84
3 13 -47.00
4 15 19.76

[Example 5]
Unit mm

Surface data surface number rd nd νd θgF
1 * -89.470 1.00 1.88202 37.2 0.5769
2 * 12.781 2.80
3 18.156 1.80 2.00272 19.3
4 40.000 (variable)
5 (Aperture) ∞ 1.00
6 * 10.506 2.80 1.80139 45.5 0.5581
7 * 1000.000 0.20
8 15.264 1.61 1.88300 40.8 0.5667
9 22.413 0.45 1.86900 19.4 0.6222
10 7.913 2.05
11 -18.305 0.45 1.76182 26.5
12 4995.127 1.39 1.88300 40.8 0.5667
13 -11.393 (variable)
14 ∞ 1.09 1.51633 64.1
15 ∞ 1.62
Image plane ∞

Aspheric data 1st surface
K = 0.00000e + 000 A 4 = 6.15911e-005 A 6 = -1.30659e-006
A 8 = 1.24530e-008 A10 = -2.78819e-011 A12 = -1.87484e-013

Second side
K = 0.00000e + 000 A 4 = 5.82623e-005 A 6 = -1.44726e-006
A 8 = -2.54963e-009 A10 = 3.73271e-010 A12 = -3.50005e-012

6th page
K = -3.84548e-001 A 4 = -2.73378e-006 A 6 = -1.06742e-006
A 8 = -4.91674e-009

7th page
K = 1.00000e + 001 A 4 = 1.48050e-004 A 6 = -1.91894e-006

Various data Zoom ratio 1.90
Wide angle Medium telephoto focal length 10.30 14.95 19.60
F number 2.40 4.30 5.02
Half angle of view (degrees) 31.93 27.82 21.93
Image height 6.42 7.89 7.89
Total lens length 49.20 41.49 38.84
BF 15.83 18.80 21.77
d 4 17.80 7.12 1.51
d13 13.49 16.46 19.43

Zoom lens group data group Start surface Focal length
1 1 -23.55
2 6 15.02

L1 First lens group L2 Second lens group L3 Third lens group L4 Fourth lens group

Claims (14)

In a zoom lens having a first lens group having a negative refractive power and a second lens group having a positive refractive power in order from the object side to the image side, and the distance between adjacent lens groups changes during zooming.
When the Abbe number of the material of the negative lens included in the second lens group is νd2n and the partial dispersion ratio is θgF2n, the second lens group is
θgF2n <3.13 × 10 ⁻⁴ × νd2n ² −1.86 × 10 ⁻² × νd2n + 0.878
5.0 <νd2n <25.0
A zoom lens comprising a negative lens G2n that satisfies the following conditional expression: When the focal length of the second lens group is f2, and the focal length of the entire system at the telephoto end is ft,
0.3 <f2 / ft <1.0
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. When the focal length of the second lens group is f2, and the focal length of the negative lens G2n is f2n,
0.4 <| f2n / f2 | <1.0
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. When the refractive index of the material of the negative lens G2n is Nd2n,
1.750 <Nd2n <2.000
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. When the thickness on the optical axis of the negative lens G2n is D2n and the distance on the optical axis from the most object-side lens surface vertex to the most image-side vertex of the second lens group is D2,
0.04 <D2n / D2 <0.50
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. The second lens group includes a positive lens, the average value of Abbe number of the material of the positive lens included in the second lens group is νd2p, and the partial dispersion ratio of the material of the positive lens included in the second lens group is When the average value is θgF2p,
-2.45 × 10 ⁻³ × νd2p + 0.590 <θgF2p
35.0 <νd2p <50.0
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. When the second lens group has a positive lens and the average value of the refractive index of the material of the positive lens included in the second lens group is Nd2p,
1.800 <νd2p <2.000
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. When the focal length of the first lens group is f1, and the focal length of the second lens group is f2,
0.8 <| f1 / f2 | <1.8
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. When the partial dispersion ratio of the negative lens material included in the first lens group is θgF1n and the Abbe number is νd1n, the first lens group is
-2.40 × 10 ⁻³ × νd1n + 0.600 <θgF1n
The zoom lens according to claim 1, further comprising a negative lens that satisfies the following conditional expression:   10. The zoom lens according to claim 1, wherein the zoom lens includes, in order from the object side to the image side, a first lens group having a negative refractive power and a second lens group having a positive refractive power. The zoom lens according to item.   The zoom lens 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. The zoom lens according to any one of claims 1 to 9.   In the zoom lens, 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, a third lens group having a positive refractive power, and a fourth lens having a positive refractive power. The zoom lens according to claim 1, comprising a lens group.   The zoom lens 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, a third lens group having a negative refractive power, and a fourth lens having a positive refractive power. The zoom lens according to claim 1, comprising a lens group.   An image pickup apparatus comprising: the zoom lens according to claim 1; and a solid-state image pickup device that receives an image formed by the zoom lens.