JP5371412B2 - Imaging optical system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a small telephoto lens favorably corrected in the aberration at a reference wavelength, axial chromatic aberration and chromatic aberration of magnification. <P>SOLUTION: An optical system is provided, comprising a first group having a positive refractive power, a second group that moves on focusing, and a third group including a diaphragm, wherein the first group has one aspheric face where the negative refractive power increases in the peripheral part, and the third group includes a first lens having a negative refractive power. The focal length of the whole optical system, focal length of the first group, Fno of the whole optical system, aspheric quantity, partial dispersion ratio, Abbe number or the like of the first lens are appropriately set. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an optical system including a lens group having a positive refractive power closest to the object side, and particularly to an optical system suitable for an imaging optical system.

  Generally, in a telephoto lens, axial chromatic aberration tends to increase as the focal length increases. Moreover, there is a tendency that axial chromatic aberration and lateral chromatic aberration increase as the overall length becomes smaller. Therefore, in Patent Documents 1 and 2, in order to correct these chromatic aberrations, a low-dispersion positive lens having anomalous partial dispersion such as fluorite and a high-dispersion negative lens are combined to correct chromatic aberration. A telephoto lens is disclosed.

  However, abnormal partial dispersion glass such as fluorite is effective in correcting chromatic aberration, but has a disadvantage that the optical system becomes heavy because the specific gravity is higher than other low dispersion glasses.

In Patent Documents 3 and 4, chromatic aberration is corrected using a diffractive optical element in order to compensate for these drawbacks. For example, in Patent Document 3, a diffractive optical element having a positive refractive power and an aspherical shape are provided in the first lens unit, and a telephoto lens with a small chromatic aberration is obtained while the number of lenses is as small as four and inexpensive. Yes. In Patent Document 4, a telephoto lens having a large aperture ratio and improved imaging performance including chromatic aberration is obtained by combining a refractive optical element and a diffractive optical element.
Japanese Patent Laid-Open No. 08-327897 JP 2004-258571 A Japanese Patent Laid-Open No. 10-186227 JP 2002-072082 A

  However, in the conventional technique disclosed in Patent Document 1 described above, chromatic aberration is corrected well, but the telephoto ratio is as large as about 1.0. In the prior art disclosed in Patent Document 2, the chromatic aberration of magnification is not sufficiently corrected, and the telephoto ratio is about 0.7 with respect to Fno of 4, and there is still room for downsizing. In the prior art disclosed in Patent Document 3, correction of spherical aberration, astigmatism, and chromatic aberration is insufficient, and further, the telephoto ratio is as large as about 0.8 for Fno of 4. In the prior art disclosed in Patent Document 4, the telephoto ratio is about 0.65 with respect to Fno of 4, and there is still room for downsizing.

  The present invention has been made in view of these problems, and an object of the present invention is to obtain a compact optical system in which both the aberration of the reference wavelength, the longitudinal chromatic aberration, and the lateral chromatic aberration are well corrected.

In order to solve the above problems, an optical system according to the present invention includes, in order from the object side, a first group having positive refractive power, a second group that moves in the optical axis direction during focusing, and a third group that includes a stop. An optical system having
The first group has one aspherical surface whose negative refractive power is increased at the periphery, and the third group has a first lens having negative refractive power,
The focal length of the entire optical system is f, the focal length of the first group is f1, Fno of the entire optical system is Fno, and the aspheric surface and paraxial at the effective end of the aspheric surface in the first group. The distance from the spherical surface in the optical axis direction is Das (the direction from the object side to the image side is positive), and the refractive indices of the first lens with respect to g-line, F-line, and C-line are ng, nF, nC, ( ng−nF) / (nF−nC) when the partial dispersion is θgF, the Abbe number of the first lens is vd, and the refractive power of the first lens (the sum in the case of multiple lenses) is φUDR,
0.03 <f1 / f · Fno <1.30
−0.03 <Das / f <−0.001
θgF + 1.3 × 10 ⁻³ · vd> 0.625
vd> 60
−0.8 <1 / (φUDR · f) · Fno <0
It is characterized by satisfying.

  According to the present invention, it is possible to obtain a small telephoto lens in which both the reference wavelength aberration, the axial chromatic aberration, and the lateral chromatic aberration are well corrected.

  The present invention relates to an optical system having a first lens unit having a positive refractive power disposed on the most object side (enlargement side, enlargement conjugate side, front side), and in particular, a silver halide photographic camera and a digital single-lens reflex camera. It is an invention suitable for an imaging optical system. Among them, it is particularly suitable for a telephoto imaging optical system that has good imaging performance such as aberration of reference wavelength and chromatic aberration.

  The optical system shown in each embodiment described below includes, in order from the object side to the image side (reduction side, reduction conjugate side, rear side), a first group having positive power (refractive power), The second group moves in the optical axis direction (movable when performing the focusing operation), and the third group has a stop. Here, in Examples 1, 2, and 3 described below, the second group has negative power (refractive power), and the third group also has negative power (refractive power). . However, one of the second group and the third group may have positive power (refractive power). However, when shortening the total length of the optical system, it is advantageous to make the entire optical system a stronger telephoto type. Therefore, the third group is preferably configured to have negative refractive power.

In the optical system of the present invention, when the focal length of the entire optical system is f, the focal length of the first group is f1, and Fno of the entire optical system is Fno,
0.03 <f1 / f · Fno <1.30 (1)
It is the feature to satisfy. Conditional expression (1) defines the focal length of the first group. If the upper limit is exceeded (exceeded), the total length becomes large (the length in the optical axis direction becomes long), which is not preferable. If the lower limit is exceeded (below), the curvature of the positive lens in the first lens group becomes too tight, resulting in an increased amount of aberration, making it difficult to process the positive lens, This is not preferable because the manufacturing sensitivity increases. Further, it is more preferable that these f1, f and Fno satisfy the following conditional expression (1a).

0.95 <f1 / f · Fno <1.30 (1a)
In addition, the optical system of the present example has at least one aspheric surface in the first group that has a strong negative refractive power (a weak positive refractive power) at the periphery. Here, at the effective end of the aspheric surface in the first group, the distance (deviation, aspheric amount) between the aspheric surface and the paraxial spherical surface in the optical axis direction is expressed as Das (direction from the object side to the image side). Is positive)
−0.03 <Das / f <−0.001 (2)
It is characterized by satisfying. The distance between the aspherical surface and the paraxial spherical surface from the object side to the image side (the direction from the object side to the image side is positive) is the distance in the optical axis direction (direction parallel to the optical axis) ( The distance between two surfaces.

  Conditional expression (2) defines the aspherical conditions necessary to correct spherical aberration, coma aberration, and field curvature, which are generated by increasing the refractive power of the first group when the total lens length is shortened. Is. If the upper limit is exceeded, spherical aberration, coma aberration, and field curvature will be insufficiently corrected. Exceeding the lower limit is not preferable because the aspherical surface becomes too tight, and spherical aberration, coma aberration, and field curvature are overcorrected.

The optical system of the present embodiment is more preferably -0.01 <Das / f <-0.001 (2a)
It is still better to satisfy.

  The aspheric surface is preferably a surface having a convex shape (convex shape) on the object side. On the other hand, when the aspherical surface is introduced on the concave surface on the object side, the concave surface has a tighter shape at the peripheral portion, so that the coma aberration cannot be sufficiently reduced. This aspherical surface may be a surface having a convex shape on the image side.

  In addition, each embodiment of the present invention preferably includes a diffractive optical element having positive power (refractive power) in the first group.

Next, in each embodiment of the present invention, the third group has an optical element UD (first lens) having a negative refractive power, and this optical element UD satisfies the following conditions. . Here, this condition means that the refractive index of the refractive index of the optical element UD (first lens) for the g-line, F-line, and C-line is ng, nF, nC, (ng-nF) / (nF-nC). The expressed partial dispersion is θgF, the Abbe number of the optical element UD is vd, and the refractive power of the optical element UD (the sum in the case where there are a plurality of optical elements) is φUDR. At this time, the above condition is
θgF + 1.3 × 10 ⁻³ · vd> 0.625 (3)
vd> 60 (4)
−0.8 <1 / (φUDR · f) · Fno <0 (5)
It is desirable that these be satisfied.

If the total length is shortened while maintaining the back focus, the asymmetry (refractive power) of the optical system is generated (increased), and the lateral chromatic aberration is significantly increased even in a super telephoto lens having a narrow field angle. Therefore, in the diffractive optical element in the first group, the secondary spectrum of axial chromatic aberration that normally remains on the over side is corrected to the under side (set to an overcorrected state), and the secondary spectrum of lateral chromatic aberration that normally remains on the negative side is corrected. It will be necessary to make strong corrections. The optical element UD in the third group plays a role of reversely correcting the axial chromatic aberration overcorrected in the first group to the over side and correcting the lateral chromatic aberration to the plus side. Conditional expressions (3) and (4) define the refractive index characteristics of the optical element UD. It is a so-called anomalous dispersion material. Here, θgF and vd defined by the conditional expressions (3) and (4) are
0.700> θgF + 1.3 × 10 ⁻³ · vd> 0.630 (3a)
105>vd> 75 (4a)
Is more preferable.

Conditional expression (5) defines an appropriate refractive power of the optical element UD made of an anomalous dispersion material. If the upper limit is exceeded, the refractive power of the optical element UD becomes too strong, which causes processing problems and eccentricity sensitivity problems. When the lower limit is exceeded, the refractive power of the optical element UD becomes weak, and the lateral chromatic aberration cannot be corrected and remains. The optical system of the present embodiment more preferably satisfies the following conditional expression (5a).
−0.67 <1 / (φUDR · f) · Fno <−0.20 (5a)
Further, in the first group of the embodiment of the present invention, the optical element located on the object side of the intermediate point between the surface vertex of the surface closest to the object side of the first group and the surface vertex of the surface closest to the image side of the first group. When the focal length of the surface is f1F,
1.8 <f / f1F <8.5 (6)
It is good to be satisfied. In other words, the surface vertex of the first object side surface of the first group is P1F, the surface vertex of the most image side is P1R, the intermediate point between P1F and P1R is P1M, and the optical surface exists between P1F and P1M The 1F group may be used as the aggregate, and the focal length of the 1F group may be f1F.

  Conditional expression (6) defines the refractive power arrangement in the first group that is advantageous for reducing the overall length of the optical system. By arranging positive refractive power on the object side in the first group, the first group can be made into a telephoto type, which is advantageous for downsizing of the entire system. If the upper limit is exceeded, the positive refractive power on the object side in the first group becomes too strong, which increases the processing problems and the problem of eccentricity sensitivity, which is not preferable. If the lower limit is exceeded, the positive refractive power on the object side in the first group becomes too weak, which is disadvantageous for shortening the overall lens length.

These f and f1F are more preferably
1.8 <f / f1F <7.2 (6a)
It is good to be satisfied.

Further, in the first group, the focal length of the optical surface existing on the image side with respect to the intermediate point between the surface vertex of the most object side surface of the first group and the surface vertex of the first image side of the first group is defined as f1R. And At this time,
-3.5 <f / f1R <1.0 (7)
It is good to be satisfied. In other words, the assembly of optical surfaces existing between P1M and P1R described above may be a 1R group, and the focal length may be f1R.

Conditional expression (7) defines a refractive power arrangement in the first lens unit that is advantageous for reducing the total lens length. By disposing negative refractive power on the image side in the first group, the first group can be made into a telephoto type, which is advantageous for downsizing of the entire system. If the upper limit is exceeded, the negative refractive power on the image side in the first group becomes too weak, which is disadvantageous for shortening the total lens length. If the lower limit is exceeded, the negative refracting power on the image side in the first group becomes too strong, which increases the processing problem and the problem of eccentricity sensitivity. These f and f1R are more preferably
-3.1 <f / f1R <0.5 (7a)
It is good to be satisfied.

The first group includes a second lens having negative refractive power, and the focal length of the second lens is fn, and the combined focal length of the optical surface disposed on the object side of the second lens is fpp. And when
0.05 <fpp / f <0.32 (8)
-1.0 <fn / f (9)
It is good to be satisfied.

Conditional expression (8) defines the combined refractive power of the positive lens unit on the object side in the first group, which is suitable for making the first group a telephoto type. By increasing the positive refractive power on the object side of the negative lens that satisfies the conditional expression (9), the first lens unit is made a stronger telephoto type. If the upper limit is exceeded, the overall length cannot be shortened sufficiently. Exceeding the lower limit is not preferable because the curvature of the positive lens becomes too tight and the processing becomes difficult and the manufacturing sensitivity becomes too high. Here, each of the above conditional expressions (8) and (9) may preferably be rewritten as follows.
0.10 <fpp / f <0.30 (8a)
−0.450 <fn / f <−0.120 (9a)
When the focal length of the diffractive optical element having the positive power (refractive power) is fDO,
20 <fDO / f1 <130 (10)
It is desirable to satisfy

  This conditional expression (10) is suitable for correcting axial chromatic aberration and lateral chromatic aberration with the diffractive optical element in the first group and the optical element UD in the third group. It defines the refractive power arrangement. If the upper limit value is exceeded, the secondary spectrum of axial chromatic aberration will be undercorrected, and if the upper limit value is exceeded, it will be overcorrected.

For the same reason, the following conditional expression (10a) is more preferably satisfied.
40 <fDO / f1 <130 (10a)
The optical element UD (first lens) described above has a concave surface on the object side, and when the curvature of the concave surface is Rud1,
-0.2 <Rud1 / f <0.0 (11)
It is desirable to satisfy

Conditional expression (11) defines an appropriate shape of the optical element UD. If the upper limit is exceeded, lateral chromatic aberration will be undercorrected. Exceeding the lower limit value is not preferable because the processing of the optical element UD becomes difficult or a problem in the sensitivity to eccentricity occurs. This conditional expression (11) may more preferably be rewritten as follows.
−0.15 <Rud1 / f <−0.01 (11a)
Hereinafter, preferred embodiments of an optical system of the present invention will be described in detail with reference to the accompanying drawings.

  The optical system of Example 1 (Numerical Example 1 shown below) of the present invention will be described below with reference to FIGS. Here, FIG. 1 is a lens cross-sectional view of Example 1, FIG. 2 is an aberration diagram when focused on an object at infinity of Example 1, and FIG. 3 is focused on a close object of Example 1. It is an aberration diagram at the time.

  Here, in the lens cross-sectional view of FIG. 1 (the same applies to FIGS. 2 and 3), Li is the i-th group, DF is the first diffractive optical element, DR is the second diffractive optical element, SP is the stop, and IS is The anti-vibration lens group, IP, represents the image plane. In the figure and the following numerical example 1 (the same applies to 2 and 3), the * mark represents the aspherical position. In each aberration diagram, d and g represent d-line and g-line, respectively, and ΔM and ΔS represent a meridional image surface and a sagittal image surface, respectively. Further, the chromatic aberration of magnification is represented by the g-line.

  Hereinafter, a lens configuration according to the first embodiment of the present invention will be described with reference to FIG.

  The optical system of Embodiment 1 shown in FIG. 1 includes, in order from the object side, a first lens unit (first lens unit) L1 having a positive refractive power, an object having a negative refractive power, and focusing from infinity to the nearest object. A second group (second lens group) L2 moving from the image side to the image side, and a third group (third lens group) having a negative refractive power and having a stop.

  L1 includes, in order from the object side, a cemented lens of a positive lens and a positive lens, a cemented lens of a positive lens and a negative lens, and a cemented lens of a negative lens and a positive lens. Introducing an aspheric surface with negative refractive power at the periphery on the object side surface of the cemented lens of the positive lens and the positive lens in L1 to reduce spherical aberration, coma aberration, and field curvature that occur when the total length is shortened ( Correction). Furthermore, an aspherical surface in which the negative refractive power is increased at the peripheral portion is introduced to the object side surface of the subsequent cemented lens of the positive lens and the negative lens. Further, by introducing a diffractive optical element DO having a positive refractive power to the cemented surface of the cemented lens closest to the object side in L1, axial chromatic aberration and lateral chromatic aberration that occur when the overall length is shortened are reduced (corrected). .

  L2 is composed of a single negative lens, and uses a low-dispersion material to reduce chromatic aberration fluctuations during focusing.

  L3 includes a stop SP from the object side, has a single aspheric surface on the image side of the stop, and is a negative lens (first lens) made of a material having a large partial dispersion at a position where the off-axis ray height is high. 1 lens) UD. This L3 corrects the aberration of the reference wavelength and the lateral chromatic aberration which cannot be corrected by L1. In addition, in order to improve the diffraction efficiency of the diffractive optical element DO, the light incident angle is introduced into a small surface. Further, since chromatic aberration can be corrected by the diffractive optical element DO and the negative lens UD, a material having an abnormal partial dispersion is not used for the positive lens in L1, but of course the material of the positive lens in L1 is an abnormal partial dispersion. It may be a material with

  The optical system of Example 2 (Numerical Example 2 shown below) of the present invention will be described below with reference to FIGS. 4 is a lens cross-sectional view of Example 2, FIG. 5 is an aberration diagram when focusing on an object at infinity of Example 2, and FIG. 6 is focused on a close object of Example 2. It is an aberration diagram at the time.

  An optical system according to Example 2 of the present invention will be described. The optical system of the second embodiment has a first lens unit L1 having a positive refractive power in order from the object side, and a second lens unit having a negative refractive power and moving from the object side to the image side during focusing from infinity to the closest distance. The lens unit L2 includes a stop and includes a third lens unit having a negative refractive power.

  L1 includes a protective glass having a weak refractive power, a cemented lens of a positive lens and a positive lens, a positive lens, a negative lens, and a positive lens in order from the object side. By introducing an aspherical surface that has a negative refractive power at the periphery on the object side surface of the most positive lens on the image side in L1, spherical aberration, coma aberration, and field curvature that occur when shortening the overall length are reduced. (Correction). In addition, a diffractive optical element DO having a positive refractive power is introduced into the cemented surface of the cemented lens closest to the object side in L1, and axial chromatic aberration and lateral chromatic aberration that occur when the total length is shortened are reduced.

  L2 includes a cemented lens of a positive lens and a negative lens, and reduces chromatic aberration fluctuations during focusing.

  L3 includes a stop SP on the object side, a single aspheric surface on the image side of the stop, and a negative lens UD having a high refractive power made of a material having a large partial dispersion at a position where the off-axis ray height is high. It is out. The optical system of the present embodiment corrects the aberration of the reference wavelength and the lateral chromatic aberration that cannot be corrected by L1 by configuring L3 as described above.

  In addition, in order to improve the diffraction efficiency of the diffractive optical element DO, the light incident angle is introduced into a small surface. Further, since chromatic aberration can be corrected by the diffractive optical element DO and the negative lens UD, no abnormal partial dispersion material is used for the positive lens in L1, but of course the material of the positive lens in L1 has abnormal partial dispersion. It is good as a material.

  The optical system of Example 3 (Numerical Example 3 shown below) of the present invention will be described below with reference to FIGS. 7 is a lens cross-sectional view of Example 3, FIG. 8 is an aberration diagram when focusing on an object at infinity of Example 3, and FIG. 9 is focused on a close object of Example 3. It is an aberration diagram at the time.

  As shown in FIG. 7, the optical system of Example 3 includes, in order from the object side, the first lens unit L1 having a positive refractive power, an image from the object side at the time of focusing from infinity to the nearest object having a negative refractive power. A second group L2 that moves to the side, a third group that has a negative refractive power and has a stop.

  L1 includes, in order from the object side, a cemented lens of a positive lens and a positive lens, a cemented lens of a positive lens and a negative lens, and a cemented lens of a negative lens and a positive lens. Introducing an aspherical surface that has negative refractive power at the periphery on the object side surface of the cemented lens between the positive lens and positive lens in L1, and corrects spherical aberration, coma aberration, and field curvature that occur when the total length is shortened. ing. Furthermore, an aspherical surface in which the negative refractive power is increased at the peripheral portion is introduced to the object side surface of the subsequent cemented lens of the positive lens and the negative lens. In addition, a diffractive optical element DO having positive refractive power is introduced into the cemented surface of the cemented lens closest to the object in L1, and axial chromatic aberration and lateral chromatic aberration that occur when the total length is shortened are corrected.

  L2 is composed of a single negative lens, and uses a low dispersion material in order to reduce chromatic aberration fluctuations during focusing.

  L3 has a stop SP from the object side, has one aspheric surface on the image side of the stop, and is made of a material having a large partial dispersion at a position where the off-axis ray height is high, and a negative lens UD having a large refractive power. The reference wavelength aberration and lateral chromatic aberration that cannot be corrected by L1 are corrected. In addition, in order to improve the diffraction efficiency of the diffractive optical element DO, the light incident angle is introduced into a small surface. Further, since chromatic aberration can be corrected by the diffractive optical element DO and the negative lens UD, no abnormal partial dispersion material is used for the positive lens in L1, but of course the material of the positive lens in L1 has abnormal partial dispersion. It is good as a material.

Next, optical data of numerical examples 1, 2, and 3 corresponding to the above-described examples 1, 2, and 3 will be shown. Here, in each numerical example, f is a focal length, Fno is an F number, and 2ω is a comprehensive angle of view. Ri is the radius of curvature of the i-th lens surface in order from the object side, Di is the i-th lens thickness or air spacing, and Ni and Vi are the refractive index and Abbe number of the material of the i-th lens. The aspherical shape has a radius of curvature at the center of the lens surface as R, the optical axis direction as the X-axis, the direction perpendicular to the optical axis as the Y-axis, and the aspheric coefficient as Ai (i = 1, 2, 3... )
X = (1 / R) Y2
1+ {1- (K + 1) (Y / R) 2} 1/2
+ A4Y4 + A6Y6 + A8Y8 + A10Y10 + ...
It shall be represented by

Further, the phase shape φ of the diffraction surface is such that the height in the direction perpendicular to the optical axis is h, the diffraction order of the diffracted light is m, the design wavelength is λ0, and the phase coefficient is Ai (i = 1, 2, 3,...). When
φ (h, m) = {2π / (mλ0)} (A2Y2 + A4Y4 + A6Y6 +...)
It shall be represented by In each embodiment, the diffraction order m of the diffracted light is 1, and the design wavelength λ0 is the wavelength of the d-line (587.56 nm).

Numerical example 1
Unit mm
Surface data surface number rd nd vd
1 * 70.057 14.00 1.48749 70.2
2 (Diffraction) 175.248 10.00 1.48749 70.2
3 991.665 6.00
4 * 64.577 15.50 1.48749 70.2
5 2061.532 3.30 1.74 100 52.6
6 302.438 9.50
7 136.628 3.00 1.83481 42.7
8 30.399 13.00 1.48749 70.2
9 -2477.682 (variable)
10 351.570 1.80 1.43387 95.1
11 37.297 (variable)
12 (Aperture) ∞ 4.02
13 -313.023 1.30 1.80518 25.4
14 32.780 4.70 1.51742 52.4
15 -49.402 2.30
16 58.242 3.30 1.75520 27.5
17 -50.314 1.30 1.81600 46.6
18 41.966 2.34
19 313.763 1.30 1.83481 42.7
20 53.391 3.60
21 42.779 7.20 1.64769 33.8
22 -19.470 1.40 1.83481 42.7
23 * 46.582 0.44
24 57.578 8.00 1.51742 52.4
25 -19.943 0.00
26 -22.932 2.00 1.43387 95.1
27 44.999 0.50
28 38.754 4.80 1.51742 52.4
29 1425.717 0.50
30 ∞ 2.20 1.51633 64.1
31 ∞
Image plane ∞

Aspheric data 1st surface
K = -1.43855e-001 A 4 = -1.93099e-010 A 6 = -2.74985e-011 A 8 = 1.37063e-015 A10 = -2.18842e-018
Second surface (diffractive surface)
A 2 = -4.70000e-005 A 4 = -1.54677e-009 A 6 = 1.48064e-012 A 8 = -2.78650e-016
4th page
K = 8.12883e-002 A 4 = -3.09766e-007 A 6 = -1.38173e-011 A 8 = -1.30814e-014 A10 = 8.97456e-018
23rd page
K = -2.20153e-001 A 4 = 6.33415e-007 A 6 = -9.37707e-012 A 8 = 2.58779e-012 A10 = -2.54583e-014

Various data Zoom ratio 1.00

Focal length 389.99
F number 4.12
Angle of View 3.18
Statue height 21.64
Total lens length 212.07
BF 52.70

Object distance -3500
d 9 13.83 20.34
d11 18.24 11.73

Lens group data group Start surface Focal length
1 1 114.82
2 10 -95.98
3 12 -86.05

Numerical example 2
Unit mm
Surface data surface number rd nd vd
1 ∞ 4.50 1.51633 64.1
2 ∞ 0.90
3 79.911 13.00 1.48749 70.2
4 (Diffraction) 180.000 12.00 1.48749 70.2
5 -410.392 6.00
6 78.598 12.50 1.48749 70.2
7 783.108 3.80
8 -240.575 3.00 1.80610 40.9
9 73.587 0.14
10 * 65.709 12.50 1.48749 70.2
11 -211.470 (variable)
12 225.694 4.60 1.78472 25.7
13 925.141 2.20 1.83481 42.7
14 90.756 (variable)
15 (Aperture) ∞ 10.00
16 * 586.982 1.80 1.84666 23.9
17 53.892 5.20 1.71999 50.2
18 52.114 1.20
19 74.287 6.25 1.84666 23.9
20 -52.079 1.65 1.60311 60.6
21 -419.815 5.52
22 -329.581 1.60 1.77250 49.6
23 42.356 2.82
24 143.913 9.30 1.71999 50.2
25 -19.617 1.80 1.83400 37.2
26 396.634 0.50
27 58.569 10.50 1.54072 47.2
28 -30.000 2.00 1.49700 81.5
29 -2239.456 2.00
30 ∞ 2.00 1.51633 64.1
31 ∞
Image plane ∞

Aspheric data 4th surface (diffractive surface)
A 2 = -3.50000e-005 A 4 = 4.64752e-010

10th page
K = 4.90788e-001 A 4 = -6.09902e-007 A 6 = -1.41185e-010 A 8 = -3.80264e-014 A10 = 5.22218e-018

16th page
K = -2.26102e + 001 A 4 = 8.30526e-007 A 6 = -6.52746e-011 A 8 = 2.21720e-012 A10 = -2.55480e-015

Various data Zoom ratio 1.00

Focal length 284.97
F number 2.91
Angle of View 4.34
Statue height 21.64
Total lens length 218.75
BF 55.47

Object distance -∞ -6000
d11 11.50 16.12
d14 12.50 7.88

Lens group data group Start surface Focal length
1 1 114.65
2 12 -179.33
3 15 -117.33

Numerical example 3

Unit mm
Surface data surface number rd nd vd
1 * 66.840 12.94 1.48749 70.2
2 (Diffraction) 122.932 12.44 1.48749 70.2
3 1072.527 5.85
4 * 68.786 15.70 1.48749 70.2
5 1909.848 3.22 1.74 100 52.6
6 347.428 9.26
7 192.222 2.92 1.83481 42.7
8 31.142 15.50 1.48749 70.2
9 -1876.226 (variable)
10 167.205 1.75 1.43387 95.1
11 35.165 (variable)
12 (Aperture) ∞ 3.92
13 199.016 1.27 1.80518 25.4
14 46.568 0.00
15 46.568 5.08 1.51742 52.4
16 -95.666 2.24
17 44.521 4.22 1.75520 27.5
18 389.659 1.27 1.81600 46.6
19 60.363 2.28
20 3746.396 1.27 1.83481 42.7
21 63.462 3.51
22 146.214 3.00 1.64769 33.8
23 -69.451 1.36 1.83481 42.7
24 * 63.140 0.80
25 111.379 11.00 1.51742 52.4
26 -21.017 0.00
27 -21.006 1.95 1.43387 95.1
28 63.736 0.49
29 48.454 5.68 1.51742 52.4
30 1402.397 0.49
31 ∞ 2.14 1.51633 64.1
32 ∞
Image plane ∞

Aspheric data 1st surface
K = -3.49165e-001 A 4 = 3.92214e-008 A 6 = -2.32827e-011 A 8 = 5.26911e-015 A10 = -2.28687e-018

Second surface (diffractive surface)
A 2 = -5.04353e-005 A 4 = -2.62726e-010 A 6 = 4.90495e-013 A 8 = -4.98370e-017

4th page
K = -1.18277e-002 A 4 = -2.20294e-007 A 6 = 4.18510e-011 A 8 = -3.48675e-014 A10 = 1.79742e-017

24th page
K = -2.91125e + 000 A 4 = 1.39454e-006 A 6 = -1.31073e-009 A 8 = 5.38346e-012 A10 = -1.07741e-014

Various data Zoom ratio 1.00

Focal length 291.00
F number 2.88
Angle of View 4.17
Statue height 21.64
Total lens length 208.00
BF 54.00

Object distance -∞ -3500
d 9 4.69 11.33
d11 17.78 11.13

Lens group data group Start surface Focal length
1 1 124.05
2 10 -102.68
3 12 -383.79

  Next, Table 1 below shows the calculation results of conditional expressions (1) to (11) in each example of the present invention.

  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. For example, in the embodiments of the present invention, the description has been mainly made of the single-focus optical system. However, the present invention may be applied to a zoom lens, and as described above, the second group or the third group. May have a positive refractive power.

  Moreover, it is applicable also to the optical apparatus containing this optical system. For example, the present invention can also be applied to an image pickup apparatus that includes an image pickup device such as a CCD and the optical system of this embodiment and forms an image of a subject on the image pickup device by the optical system of this embodiment. In addition, the liquid crystal panel (image display element) and the optical system of the present embodiment can be applied to a liquid crystal projector (image projection apparatus) that projects light from the liquid crystal panel onto the projection surface with the optical system of the present embodiment. It is.

Lens sectional view of Numerical Example 1 of the present invention Aberration diagram when focusing on an object at infinity according to Numerical Example 1 of the present invention Aberration diagram at the time of focusing on the closest object according to Numerical Example 1 of the present invention Lens sectional view of Numerical Example 2 of the present invention Aberration diagram when focusing on an object at infinity according to Numerical Example 2 of the present invention Aberration diagram at the time of focusing on the closest object according to Numerical Example 2 of the present invention Lens sectional view of Numerical Example 3 of the present invention Aberration diagram when focusing on an object at infinity according to Numerical Example 3 of the present invention Aberration diagram at the time of focusing on the closest object according to Numerical Example 3 of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 L1 1st lens group 2 L2 2nd lens group 3 L3 3rd lens group 4 SP Aperture 5 IP Image surface 6 * Aspherical surface 7 DO Diffractive optical element according to the present invention 8 UD Negative refractive power according to the present invention 9 d d line 10 g g line 11 ΔS sagittal image plane 12 ΔM meridional image plane

Claims (10)

In order from the object side, in an optical system having a first group having positive refractive power, a second group that moves in the optical axis direction during focusing, and a third group that includes a stop,
The first group has one aspherical surface whose negative refractive power is strong at the peripheral part,
The third group includes a first lens having negative refractive power;
The focal length of the entire optical system is f, the focal length of the first group is f1, Fno of the entire optical system is Fno, and the aspheric surface and paraxial at the effective end of the aspheric surface in the first group. The distance from the spherical surface to the image side is expressed as Das, and the refractive indexes of the first lens with respect to the g-line, F-line, and C-line are expressed as ng, nF, nC, (ng-nF) / (nF-nC). When the partial dispersion is θgF, the Abbe number of the first lens is vd, and the refractive power of the first lens is φUDR,
0.03 <f1 / f · Fno <1.30
−0.03 <Das / f <−0.001
θgF + 1.3 × 10 ⁻³ · vd> 0.625
vd> 60
−0.8 <1 / (φUDR · f) · Fno <0
An optical system characterized by satisfying   The optical system according to claim 1, wherein the second group has a negative refractive power and the third group has a negative refractive power.   The optical system according to claim 1, wherein the aspheric surface is a surface convex toward the object side. In the first group, the focal length of the optical surface existing on the object side relative to the intermediate point between the surface vertex of the surface closest to the object side of the first group and the surface vertex of the surface closest to the image side of the first group. When f1F
1.8 <f / f1F <8.5
The optical system according to claim 1, wherein: In the first group, the focal length of the optical surface existing on the image side with respect to the intermediate point between the surface vertex of the surface closest to the object side of the first group and the surface vertex of the surface closest to the image of the first group. When f1R is assumed,
−3.5 <f / f1R <1.0
The optical system according to claim 1, wherein: The first group includes a second lens having a negative refractive power, and the focal length of the second lens is fn, and the combined focal length of the optical surface disposed on the object side of the second lens is fpp. And when
-1.0 <fn / f
0.05 <fpp / f <0.32
The optical system according to claim 1, wherein:   The optical system according to claim 1, wherein the first group includes a diffractive optical element having a positive refractive power. When the focal length of the diffractive optical element having positive refractive power is fDO,
20 <fDO / f1 <130
The optical system according to claim 7, wherein: The first lens has a concave surface on the object side, and when the curvature of the concave surface on the object side is Rud1,
−0.2 <Rud1 / f <0.0
The optical system according to claim 1, wherein:   An optical apparatus comprising the optical system according to claim 1.

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