JP2015200845A - Optical system and image capturing device having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical system which has a long back focus and wide view angle, and yet easily provides a high-quality image over an entire screen area.SOLUTION: An optical system comprises, in order from the object side to the image side, a front group having positive or negative refractive power, an aperture stop, and a rear group having positive refractive power, where the rear group comprises a cemented lens G3a comprising a positive lens G31 and a lens G32 cemented together, a positive lens G33, and a positive lens G34. A curvature radii R31f, R31r of an object-side surface and image-side surface of the positive lens G31, respectively, and an Abbe number and partial dispersion ratio νd31, θgF31 of a material of the positive lens G31 are each set appropriately.

Description

  The present invention relates to an optical system, and is suitable for an imaging optical system used in an imaging apparatus such as a silver salt film camera, a digital still camera, a digital video camera, a surveillance camera, and a TV camera.

  In recent years, an optical system used in an imaging apparatus is required to easily obtain a high-resolution image and to easily capture a wide range with a wide angle of view. Further, since various optical elements such as a low-pass filter and a color correction filter are arranged between the lens surface closest to the image side and the imaging surface, it is required to have a relatively long back focus.

  Conventionally, it consists of a front group of positive or negative refractive power in order from the object side to the image side, an aperture stop, and a rear group of positive refractive power, and is a retrofocus type with a wide angle of view and a shorter focal length than the back focus. Optical systems are known (Patent Documents 1 and 2). Patent Documents 1 and 2 disclose a wide-angle optical system having a long back focus.

JP-A-8-179196 JP 2009-109723 A JP2012-123155A

  A retrofocus optical system is relatively easy to achieve a wide angle of view while ensuring a long back focus. However, a retrofocus optical system has an asymmetric refractive power arrangement with an aperture stop interposed therebetween. For this reason, the occurrence of various aberrations due to asymmetry such as coma, distortion, and lateral chromatic aberration increases, and it tends to be difficult to obtain high optical performance.

  In order to obtain a long back focus, wide angle of view, and high optical performance over the entire screen, it is important to appropriately set the refractive power and lens configuration of the lens groups before and after the aperture stop in the optical system. Come. If these settings are not appropriate, it becomes difficult to obtain an optical system having a wide angle of view and high optical performance.

  An object of the present invention is to provide an optical system that can easily obtain a high-quality image over the entire screen while having a long back focus and a wide angle of view.

The optical system according to the present invention includes, in order from the object side to the image side, a front group having a positive or negative refractive power, an aperture stop, and a rear group having a positive refractive power, and the rear group is sequentially from the object side to the image side. A positive lens G31 and a negative lens G32, a cemented lens G3a, a positive lens G33, and a positive lens G34.
When the radius of curvature of the object-side lens surface and the image-side lens surface of the positive lens G31 is R31f and R31r, and the Abbe number and partial dispersion ratio of the material of the positive lens G31 are νd31 and θgF31, respectively.
1.0 <(R31f + R31r) / (R31f-R31r) <10.0
νd31> 70.0
θgF31 − (− 0.001682 · νd31 + 0.6438)> 0.0
It satisfies the following conditional expression.

  According to the present invention, it is possible to obtain an optical system that can easily obtain a high-quality image over the entire screen while having a long back focus and a wide angle of view.

Lens sectional view of Example 1 Aberration diagram of the object at infinity in Example 1 Lens sectional view of Example 2 Aberration diagrams of the object at infinity in Example 2 Lens sectional view of Example 3 Aberration diagrams of the object at infinity in Example 3 The figure which shows the relationship between Abbe number (nu) d and partial dispersion ratio (theta) gF. 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 optical system of the present invention includes, in order from the object side to the image side, a front group having positive or negative refractive power, an aperture stop, and a rear group having positive refractive power. The optical system of the present invention is a retrofocus imaging optical system having a focal length shorter than the back focus.

  FIG. 1 is a lens cross-sectional view of Embodiment 1 of the present invention. FIG. 2 shows longitudinal aberrations when focusing on infinity in Example 1. FIG. 3 is a lens cross-sectional view of Embodiment 2 of the present invention. FIG. 4 shows longitudinal aberrations when focusing on infinity in Example 2. FIG. 5 is a lens cross-sectional view of Embodiment 3 of the present invention. FIG. 6 shows longitudinal aberrations when focusing on infinity in Example 3. FIG. 7 is a graph showing the relationship between the Abbe number νd of the material and the partial dispersion ratio θgF. FIG. 8 is a schematic diagram of a camera (imaging device) including the optical system of the present invention.

  The optical system of each embodiment is suitable as an imaging optical system used in an imaging apparatus (optical apparatus) such as a digital still camera, a digital video camera, or a silver salt film camera. In the lens cross-sectional view, the left side is the object side (front), and the right side is the image side (rear). In addition, you may use the optical system of each Example as projection lenses, such as a projector. At this time, the left side is the screen side and the right side is the projected image side.

  In the lens cross-sectional view, LA is an optical system. The optical system LA has a configuration having a front group LF having positive or negative refractive power on the object side and a rear group LR having positive refractive power on the image side across the aperture stop SP. The front group LF includes a first lens unit L1 having a positive or negative refractive power and a second lens unit L2 having a positive refractive power. The rear group LR includes a third lens unit L3 having a positive refractive power. During the focusing, the second lens unit L2 and the third lens unit L3 move.

  Here, the lens group is divided on the basis of a change in the distance during focusing, and each lens group is composed of one or a plurality of lenses. IP is an image plane. When used as an imaging optical system for a digital 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 used for a silver salt film camera. Sometimes it corresponds to the film surface.

  Each longitudinal aberration diagram shows spherical aberration, astigmatism, distortion, and lateral chromatic aberration in order from the left. In the diagram showing spherical aberration, d represents the d-line (587.6 nm), and g represents the g-line (435.8 nm). In the diagram showing astigmatism, S represents the sagittal direction of the d line, and M represents the meridional direction of the d line. Moreover, the figure which shows distortion represents the distortion in d line | wire. The lateral chromatic aberration is shown for the g-line with respect to the d-line. Fno represents the F number, and ω represents the half angle of view (degrees) of the shooting angle of view.

  The optical system of each embodiment includes, in order from the object side to the image side, a front group LF having a positive or negative refractive power, an aperture stop SP, and a rear group LR having a positive refractive power. The rear group LR includes, in order from the object side to the image side, a cemented lens G3a in which a positive lens G31 and a negative lens G32 are cemented, a positive lens G33, and a positive lens G34.

The curvature radii of the object-side lens surface and the image-side lens surface of the positive lens G31 are R31f and R31r, respectively. The Abbe number and the partial dispersion ratio of the material of the positive lens G31 are νd31 and θgF31, respectively. At this time,
1.0 <(R31f + R31r) / (R31f−R31r) <10.0 (1)
νd31> 70.0 (2)
θgF31 − (− 0.001682 · νd31 + 0.6438)> 0.0 (3)
The following conditional expression is satisfied.

  Here, the Abbe number νd and the partial dispersion ratio θgF are as follows. The refractive indices of the materials for g-line (wavelength 435.8 nm), F-line (wavelength 486.1 nm), d-line (wavelength 587.6 nm), and C-line (wavelength 656.3 nm) are Ng, NF, Nd, and NC, respectively. To do. At this time, the Abbe number νd and the partial dispersion ratio θgF can be expressed as follows.

νd = (Nd−1) / (NF-NC) (a)
θgF = (Ng−NF) / (NF−NC) (b)
FIG. 7 is a graph showing the relationship between the Abbe number νd of the material and the partial dispersion ratio θgF. In FIG. 7, product name: PBM2 (νd = 36.26, θgF = 0.5828) and product name: NSL7 (νd = 60.49, θgF = 0.5436) manufactured by OHARA INC. Are shown. In FIG. 7, a line connecting two points of two materials is taken as a reference line. For the low dispersion glass, it is effective for correcting the secondary spectrum to use a glass that is located above the reference line. The correction effect increases as the distance from the reference line increases.

  In each embodiment, by appropriately setting the Abbe number and partial dispersion ratio of the material of the positive lens G31 used for the rear lens group LR and appropriately setting the lens shape of the positive lens, the chromatic aberration can be corrected well. High optical performance is obtained. In particular, the bending of the g-line is reduced in the lateral chromatic aberration.

  Conditional expression (1) relates to the lens shape (shape factor) of the positive lens G31 of the cemented lens G3a constituting the rear group LR. If the upper limit of conditional expression (1) is exceeded, more spherical aberration occurs than in the front group LF, and this aberration correction becomes difficult, and it becomes difficult to obtain high optical performance. In addition, the incident angle of off-axis rays to the positive lens G31 becomes tight, the lateral chromatic aberration increases, and the curve of the g-line increases. If the lower limit of conditional expression (1) is exceeded, spherical aberration will be overcorrected and it will be difficult to maintain high optical performance.

  Conditional expressions (2) and (3) relate to the Abbe number and partial dispersion ratio of the material of the positive lens G31 of the cemented lens G3a constituting the rear group LR. That is, since the material satisfying the conditional expressions (2) and (3) has anomalous dispersion while having low dispersion, chromatic aberration can be corrected effectively. When the lower limit of conditional expression (2) is exceeded, the achromaticity of the rear group LR becomes insufficient, and correction of chromatic aberration becomes difficult. When the lower limit of conditional expression (3) is exceeded, the anomalous dispersion of the material of the positive lens G31 becomes small, and it becomes difficult to correct lateral chromatic aberration.

  More preferably, the numerical ranges of conditional expressions (1) and (2) are set as follows.

3.0 <(R31f + R31r) / (R31f−R31r) <8.0 (1a)
νd3p> 80.0 (2a)
According to each embodiment, by specifying the lens configuration as described above, various chromatic aberrations such as spherical aberration, coma aberration, and astigmatism are corrected well, and axial chromatic aberration and lateral chromatic aberration are corrected well. ing. As a result, a retrofocus type optical system having a long back focus and a wide field angle and high optical performance is obtained.

  In each embodiment, the front group LF includes, in order from the object side to the image side, a first lens group L1 having a positive or negative refractive power and a second lens group L2 having a positive refractive power, and the rear group LR is a positive group. The third lens unit L3 has a refractive power. During focusing from infinity to short distance, the second lens unit L2 and the third lens unit L3 move integrally (with the same trajectory) or independently (with different trajectories) toward the object side. Further, focusing while changing the distance between the first lens unit L1 and the second lens unit L2 reduces the image plane variation caused by the variation of the object distance.

  In each embodiment, it is preferable that the third lens unit L3 has a positive lens closest to the image side, and the positive lens is provided with an aspherical surface. If the positive lens is provided with an aspherical surface, the sagittal image plane is less tilted and it is easy to obtain good optical performance up to the periphery of the screen.

  In each embodiment, it is preferable to satisfy one or more of the following conditional expressions. The Abbe number and the partial dispersion ratio of the material of the negative lens G32 are νd32 and θgF32, respectively. The second lens unit L2 includes a positive lens G21, a positive lens G22, a positive lens G23, and a negative lens G24 in order from the object side to the image side. The positive lens G22, the positive lens G23, and the negative lens G24 are preferably composed of a cemented lens G2a. At this time, the Abbe number and the partial dispersion ratio of the material of the positive lens G22 are νd22 and θgF22, respectively.

The anomalous partial dispersibility ΔθgF2pi of the material of the positive lens G22 or the positive lens G23 is the Abbe number νd2pi of the material, and the partial dispersion ratio is θgF2pi.
ΔθgF2pi = θgF2pi − (− 1.665 × 10 ⁻⁷ × νd2pi ³ + 5.213 × 10 ⁻⁵ × νd2pi ² −5.656 × 10 ⁻³ × νd2pi + 7.278 × 10 ⁻¹ )
And The refractive index of the material of the positive lens G33 or the material of the positive lens G34 is Nd3p. At this time, it is preferable to satisfy one or more of the following conditional expressions.

θgF32 − (− 0.001682 · νd32 + 0.6458) <0.0 (4)
νd22> 65.0 (5)
θgF22 − (− 0.001682 · νd22 + 0.6438)> 0.0 (6)
ΔθgF2pi> 0.0272 (7)
Nd3p> 1.80 (8)
Next, the technical meaning of each conditional expression described above will be described.

  Conditional expression (4) is mainly for satisfactorily correcting chromatic aberration with respect to the Abbe number and partial dispersion ratio of the material of the negative lens G32 of the cemented lens G3a constituting the rear lens group LR. When the lower limit of conditional expression (4) is exceeded, the anomalous dispersion of the material of the negative lens G32 becomes too large, and it becomes difficult to correct lateral chromatic aberration. Conditional expressions (5) and (6) are mainly for favorably correcting chromatic aberration with respect to the Abbe number and partial dispersion ratio of the material of the positive lens G22 constituting the second lens unit L2. If the lower limit of conditional expression (5) is exceeded, achromaticity in the second lens unit L2 will be insufficient and correction of chromatic aberration will be difficult.

  If the lower limit of conditional expression (6) is exceeded, the anomalous dispersion of the material of the positive lens G22 will be small, and it will be difficult to satisfactorily correct axial chromatic aberration. The abnormal partial dispersion (abnormal partial dispersion ratio) ΔθgF of the material specified by the conditional expression (7) will be described.

  The Abbe number νd and the partial dispersion ratio θgF are expressed by the aforementioned expressions (a) and (b). The abnormal partial dispersion ΔθgF can be expressed as follows.

ΔθgF = θgF − (− 1.665 × 10 ⁻⁷ × νd ³ + 5.213 × 10 ⁻⁵ × νd ² −5.656 × 10 ⁻³ × νd + 7.278 × 10 ⁻¹ ) (c)
Conditional expression (7) represents the anomalous partial dispersion of the material of the positive lens G22 or the positive lens G23 of the second lens unit L2. By using a positive lens made of a material that satisfies the conditional expression (7), it becomes easy to correct chromatic aberration satisfactorily. If the lower limit of conditional expression (7) is exceeded, the anomalous dispersion of the material of the positive lens will be small, and it will be difficult to satisfactorily correct axial chromatic aberration.

  Specific examples of the optical material that satisfies the conditional expression (7) include, for example, an acrylic UV curable resin (Nd = 1.545, νd = 25.3, θgF = 0.77) and N-polyvinylcarbazole (Nd = 1.696). , Νd = 17.7, θgF = 0.69). Note that the material is not limited to these materials as long as the material satisfies the conditional expression (7).

Further, as an optical material having characteristics different from those of general glass materials, there is a mixture in which the following inorganic oxide nanoparticles are dispersed in a synthetic resin. TiO ₂ (Nd = 2.758, νd = 9.54, θgF = 0.76) and the like. When TiO ₂ fine particles are dispersed in a synthetic resin at an appropriate volume ratio, an optical material that satisfies the conditional expression (7) can be obtained. Note that the material is not limited to these as long as it satisfies the conditional expression (7).

TiO ₂ is a material used in various applications, and in the optical field, it is used as a vapor deposition material that constitutes an optical thin film such as an antireflection film. In addition, photocatalysts, white pigments, and the like, and TiO ₂ fine particles are used as cosmetic materials.

  In each example, the average diameter of the fine particles dispersed in the resin is preferably about 2 nm to 50 nm in consideration of the influence of scattering and the like, and a dispersant or the like may be added to suppress aggregation. The medium material for dispersing the fine particles is preferably a polymer, and high mass productivity can be obtained by photopolymerization molding or thermal polymerization molding using a mold or the like. The dispersion characteristic N (λ) of the mixture in which the nanoparticles are dispersed can be easily calculated by the following equation derived from the well-known Drude equation.

That is, the refractive index N (λ) at the wavelength λ is
N (λ) = [1 + V {Npar (λ) ² −1} + (1-V) {Npoly (λ) ² −1}] ^1/2
It is. Here, λ is an arbitrary wavelength, Npar is the refractive index of the fine particles, Npoly is the refractive index of the polymer, and V is a fraction of the total volume of the fine particles with respect to the polymer volume. Thus, the resin or the organic composite in which the fine particles are dispersed in the resin is an optical material that satisfies the conditional expression (7).

    In each example, the above-described organic composite is used as a material that satisfies the above-described conditional expression (7).

  Conditional expression (8) sets the Petzval sum of the optical system appropriately. When the lower limit of conditional expression (8) is exceeded, the Petzval sum increases in the positive direction, and it becomes difficult to satisfactorily correct off-axis aberrations such as field curvature. More preferably, the numerical ranges of conditional expressions (5), (7), and (8) are set as follows.

νd22> 67.0 (5a)
ΔθgF2pi> 0.1 (7a)
Nd3p> 1.84 (8a)
As described above, according to each embodiment, a retrofocus type of a long back focus with high image quality in which axial chromatic aberration and lateral chromatic aberration are well corrected while suppressing various aberrations such as spherical aberration, coma aberration, and astigmatism. An optical system is obtained.

Next, the lens configuration of each example will be described.
[Example 1]
Example 1 of the present invention will be described. The first exemplary embodiment includes, in order from the object side to the image side, a first lens unit L1 having a positive refractive power, a second lens unit L2 having a positive refractive power, an aperture stop SP, and a third lens unit L3 having a positive refractive power. Has been. During the focusing, the second lens unit L2 and the third lens unit L3 move.

  The first lens unit L1 is, in order from the object side to the image side, a meniscus lens having a negative refractive power (negative lens), a negative lens, a lens having a positive refractive power (positive lens), a negative lens, a positive lens, and a positive lens. And a negative lens. The second lens unit L2 includes, in order from the object side to the image side, a cemented lens G2a in which three lenses of a positive lens G21, a positive lens G22, a positive lens G23, and a negative lens G24 are cemented. The positive lens G23 constituting the cemented lens G2a is made of a resin or a material containing an organic composite in which fine particles are dispersed in the resin.

  The third lens unit L3 includes, in order from the object side to the image side, a cemented lens G3a in which a positive lens G31 and a negative lens G32 are cemented, a positive lens G33, and a positive lens G34. As is apparent from the respective aberration diagrams, in the first embodiment, various aberrations are corrected satisfactorily.

[Example 2]
A second embodiment of the present invention will be described. The second exemplary embodiment includes, in order from the object side to the image side, a first lens unit L1 having a positive refractive power, a second lens unit L2 having a positive refractive power, an aperture stop SP, and a third lens unit L3 having a positive refractive power. Has been. During the focusing, the second lens unit L2 and the third lens unit L3 move. The first lens unit L1 includes, in order from the object side to the image side, a meniscus negative lens, a negative lens, a positive lens, a cemented lens in which the negative lens and the positive lens are cemented, and a cemented lens in which the positive lens and the negative lens are cemented. ing.

  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. As is apparent from each aberration diagram, various aberrations are corrected favorably in Example 2.

[Example 3]
A third embodiment of the present invention will be described. 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, an aperture stop SP, and a third lens unit L3 having a positive refractive power. Has been. During the focusing, the second lens unit L2 and the third lens unit L3 move.

  The first lens unit L1 includes, in order from the object side to the image side, a meniscus negative lens, a negative lens, a positive lens, and a cemented lens in which the negative lens and the positive lens are cemented. 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. As is apparent from each aberration diagram, various aberrations are corrected favorably in Example 3.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

  Next, an embodiment of a single-lens reflex camera system (imaging device) using the optical system of the present invention will be described with reference to FIG.

  In FIG. 8, reference numeral 10 denotes a single-lens reflex camera body, and 11 denotes an interchangeable lens on which the optical system according to the present invention is mounted as an imaging optical system. Reference numeral 12 denotes recording means such as a film or an image sensor for receiving a subject image obtained through the interchangeable lens 11. Reference numeral 13 denotes a finder optical system for observing a subject image from the interchangeable lens 11, and reference numeral 14 denotes a rotating quick return mirror for switching the subject image formed by the interchangeable lens 11 to the recording means 12 and the finder optical system 13 for transmission. is there.

  When observing the subject image with the finder, the subject image formed on the focusing plate 15 via the quick return mirror 14 is made into an erect image with the pentaprism 16 and then magnified and observed with the eyepiece optical system 17. At the time of shooting, the quick return mirror 14 rotates in the direction of the arrow, and the subject image is formed and recorded on the recording means 12. Reference numeral 18 denotes a submirror, and 19 denotes a focus detection device.

  As described above, by applying the optical system of the present invention as an imaging optical system such as an interchangeable lens such as a single-lens reflex camera, an imaging apparatus having high optical performance is obtained. In addition, the present imaging apparatus can be similarly applied to a mirrorless single-lens reflex camera that does not have the quick return mirror 14 or the like, or an imaging apparatus that is not a lens interchangeable type.

  In the following, numerical examples 1 to 3 corresponding to the first to third examples will be described. In each numerical example, i indicates the order of the surfaces from the object side, ri is the i-th (i-th surface) radius of curvature, di is the distance between the i-th surface and the (i + 1) -th surface, ndi, νdi Represents a refractive index and an Abbe number based on the d-line, respectively. BF is a back focus.

  The variable interval varies depending on the shooting magnification. An aspheric surface is represented by adding a symbol * after the surface number. In the aspherical shape, X is the amount of displacement from the surface vertex in the optical axis direction, h is the height from the optical axis in the direction perpendicular to the optical axis, r is the paraxial radius of curvature, K is the conic constant, A4, A6, When A8, A10, and A12 are aspherical coefficients of respective orders,

Represented by Note that “E ± ^XX ” in each aspheric coefficient means “× 10 ^{± XX} ”. Table 1 shows numerical values related to each conditional expression described above. Further, Table 2 shows the refractive index of the material related to the conditional expression (7).

(Numerical example 1)
Unit mm
Surface data surface number rd nd νd
1 73.355 3.50 1.58313 59.4
2 * 27.700 11.46
3 -307.490 1.85 1.48749 70.2
4 52.694 5.39
5 -260.875 4.01 1.90366 31.3
6 -73.913 3.89
7 -41.457 1.85 1.60342 38.0
8 110.769 0.20
9 74.880 6.93 1.91082 35.3
10 -112.546 0.20
11 90.943 10.39 1.59522 67.7
12 -38.225 1.70 1.73800 32.3
13 -81.837 (variable)
14 47.083 5.24 1.91082 35.3
15 -1364.203 1.40
16 196.395 4.08 1.59522 67.7
17 -75.554 1.00 1.54493 25.3
18 -51.514 1.55 1.69895 30.1
19 29.651 (variable)
20 (Aperture) ∞ 6.96
21 -22.117 4.42 1.49700 81.5
22 -16.399 1.50 1.73800 32.3
23 -52.708 0.13
24 123.246 7.39 1.59522 67.7
25 -31.376 0.14
26 * -103.187 4.35 1.85400 40.4
27 -38.560 (variable)
Image plane ∞

Aspheric data 2nd surface
K = 0.00000e + 000 A 4 = -8.44469e-007 A 6 = -1.40474e-009 A 8 = -1.12523e-012 A10 = 9.45006e-016 A12 = -3.55532e-018

26th page
K = 0.00000e + 000 A 4 = -6.94362e-006 A 6 = -1.20811e-009 A 8 = 8.28446e-013 A10 = -2.15964e-014 A12 = 2.93999e-017

Focal length 34.30
F number 1.45
Half angle of view (degrees) 32.25
Statue height 21.64
Total lens length 142.82
BF 38.99

INF NEAR (0.3m)
d13 8.46 1.87
d19 5.83 5.83
d27 38.99 45.58

Lens group data group Start surface Focal length
1 1 145.81
2 14 757.69
3 20 46.16

(Numerical example 2)
Unit mm
Surface data surface number rd nd νd
1 58.880 3.50 1.58313 59.4
2 * 25.574 11.77
3 -8571.522 1.85 1.48749 70.2
4 45.855 5.78
5 -290.363 4.23 1.90366 31.3
6 -61.704 3.36
7 -40.401 1.85 1.60342 38.0
8 48.751 6.53 1.91082 35.3
9 -744.267 0.20
10 72.017 11.11 1.59522 67.7
11 -37.051 1.70 1.73800 32.3
12 -58.399 (variable)
13 49.989 5.04 1.91082 35.3
14 -1201.246 1.96
15 203.633 3.92 1.59522 67.7
16 -79.188 1.00 1.54493 25.3
17 -52.680 1.55 1.69895 30.1
18 31.002 (variable)
19 (Aperture) ∞ 6.96
20 -22.067 4.36 1.49700 81.5
21 -16.489 1.50 1.73800 32.3
22 -52.550 0.13
23 112.424 7.46 1.59522 67.7
24 -31.650 0.14
25 * -104.966 4.30 1.85400 40.4
26 -39.119 (variable)
Image plane ∞

Aspheric data 2nd surface
K = 0.00000e + 000 A 4 = -5.95247e-007 A 6 = -3.22391e-009 A 8 = 7.57366e-012 A10 = -1.94579e-014 A12 = 1.29887e-017

25th page
K = 0.00000e + 000 A 4 = -7.01689e-006 A 6 = -1.74541e-010 A 8 = -8.57313e-012 A10 = 1.08161e-014 A12 = -1.14301e-017

Focal length 34.30
F number 1.45
Half angle of view (degrees) 32.25
Statue height 21.64
Total lens length 142.47
BF 38.99

INF NEAR (0.3m)
d12 7.60 1.02
d18 5.67 5.67
d26 38.99 45.57

Lens group data group Start surface Focal length
1 1 140.52
2 13 1011.41
3 19 46.03

(Numerical Example 3)
Unit mm
Surface data surface number rd nd νd
1 57.537 3.00 1.64000 60.1
2 26.533 11.82
3 30275.720 3.00 1.58313 59.4
4 * 33.009 2.80
5 62.337 7.05 1.91082 35.3
6 -100.178 5.49
7 -49.964 1.50 1.69895 30.1
8 41.962 6.69 1.91082 35.3
9 -163.205 (variable)
10 53.176 5.83 1.88300 40.8
11 -177.927 2.19
12 68.697 5.71 1.59522 67.7
13 -76.651 1.02 1.69934 26.4
14 -50.341 1.55 1.69895 30.1
15 31.098 (variable)
16 (Aperture) ∞ 6.96
17 -22.290 4.52 1.49700 81.5
18 -16.536 1.50 1.73800 32.3
19 -43.827 0.13
20 91.538 7.63 1.59522 67.7
21 -32.553 0.30
22 * -94.707 4.45 1.85400 40.4
23 -40.988 (variable)
Image plane ∞

Aspheric data 4th surface
K = 0.00000e + 000 A 4 = -4.72094e-006 A 6 = -4.59421e-009 A 8 = 9.92671e-013 A10 = -4.41856e-015

22nd page
K = 0.00000e + 000 A 4 = -7.55876e-006 A 6 = 4.60713e-009 A 8 = -4.19026e-011 A10 = 1.07707e-013 A12 = -1.18808e-016

Focal length 34.28
F number 1.45
Half angle of view (degrees) 32.26
Statue height 21.64
Total lens length 135.83
BF 38.99

INF NEAR (0.3m)
d 9 8.10 0.79
d15 5.62 5.62
d23 38.99 46.30
Zoom lens group data group Start surface Focal length
1 1 -147.21
2 10 90.29
3 16 43.84

LA optical system LF Front group LR Rear group SP Aperture stop L1 First lens group L2 Second lens group L3 Third lens group

Claims (7)

A front group having a positive or negative refractive power, an aperture stop, and a rear group having a positive refractive power are arranged in order from the object side to the image side. The rear group is arranged in order from the object side to the image side, and a positive lens G31 and a negative lens. Having a cemented lens G3a, a positive lens G33, and a positive lens G34 joined with G32.
When the radius of curvature of the object-side lens surface and the image-side lens surface of the positive lens G31 is R31f and R31r, and the Abbe number and partial dispersion ratio of the material of the positive lens G31 are νd31 and θgF31, respectively.
1.0 <(R31f + R31r) / (R31f-R31r) <10.0
νd31> 70.0
θgF31 − (− 0.001682 · νd31 + 0.6438)> 0.0
An optical system that satisfies the following conditional expression:   The front group includes, in order from the object side to the image side, a first lens group having a positive or negative refractive power and a second lens group having a positive refractive power, and the rear group is a third lens having a positive refractive power. The optical system according to claim 1, wherein the second lens group and the third lens group move during focusing. When the Abbe number and the partial dispersion ratio of the material of the negative lens G32 are νd32 and θgF32, respectively.
θgF32 − (− 0.001682 · νd32 + 0.6458) <0.0
The optical system according to claim 1, wherein the following conditional expression is satisfied. The front group includes, in order from the object side to the image side, a first lens group having a positive or negative refractive power and a second lens group having a positive refractive power, and the rear group is a third lens having a positive refractive power. And the second lens group and the third lens group move during focusing,
The second lens group includes, in order from the object side to the image side, a positive lens G21, a positive lens G22, a positive lens G23, and a negative lens G24.
The positive lens G22, the positive lens G23, and the negative lens G24 are configured by a cemented lens G2a,
When the Abbe number and partial dispersion ratio of the material of the positive lens G22 are νd22 and θgF22, respectively.
νd22> 65.0
θgF22 − (− 0.001682 · νd22 + 0.6438)> 0.0
The optical system according to claim 1, wherein the following conditional expression is satisfied. The abnormal partial dispersion ΔθgF2pi of the material of the positive lens G22 or the positive lens G23 is defined as the Abbe number νdpi of the material, and the partial dispersion ratio is θgF2pi.
ΔθgF2pi = θgF2pi − (− 1.665 × 10 ⁻⁷ × νd2pi ³ + 5.213 × 10 ⁻⁵ × νd2pi ² −5.656 × 10 ⁻³ × νd2pi + 7.278 × 10 ⁻¹ )
And when
ΔθgF2pi> 0.0272
The optical system according to claim 4, wherein the following conditional expression is satisfied. When the refractive index of the material of the positive lens G33 or the material of the positive lens G34 is Nd3p,
Nd3p> 1.80
The optical system according to claim 1, wherein the following conditional expression is satisfied.   An imaging apparatus comprising: the optical system according to claim 1; and a photoelectric conversion element that receives an image formed by the optical system.