JP2011145518A - Zoom lens and imaging device having the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a zoom lens which has a wide image angle and high optical performance in the entire zoom areas. <P>SOLUTION: The zoom lens includes, in order from an object side to an image side: a first lens group having negative refractive power; a second lens group having positive refractive power; a third lens group having negative refractive power; and a fourth lens group having positive refractive power, and zooms by moving at least one of the lens groups along the optical axis. At least one of the lens groups, having positive refractive power, includes at least one diffraction optical part, the average refractive index NDP_ave at d-line of a positive lens material among the lens groups having positive refractive power having the diffraction optical part; the focal distance fD of the lens groups having positive refractive power having the diffraction optical part; the focal distances fw, ft at the wide angle end and telescopic end of the zoom lens; and the focal distances f1, f3 of the first lens group and the third lens group are respectively set appropriately. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a zoom lens and an image pickup apparatus having the same, and is suitable for a photographing system such as a digital camera, a video camera, a TV camera, and a silver salt film camera.

  In recent years, the number of pixels of an image sensor used in an image pickup apparatus such as a digital camera or a video camera has been increased. A photographic lens used in an image pickup apparatus having such an image pickup device is required to be a zoom lens having a high resolution over the entire zoom range in which chromatic aberration is well corrected so that there is no blurring of an image color in a white light source. Has been. In addition, in order to expand the photographing area, it is desired that the zoom lens has a wide field angle on the wide angle side.

  As a wide-angle zoom lens, a negative lead type zoom lens in which a lens unit having a negative refractive power is positioned on the object side is known. The negative lead type zoom lens has a feature that it is easy to increase the back focus even if the focal length of the entire system is shortened. For this reason, it is frequently used in single-lens reflex cameras.

  As a negative lead type zoom lens for single-lens reflex cameras, there is a zoom lens that consists of four lens groups of negative, positive, negative, and positive refractive power in order from the object side, and zoomed by moving each lens group. (Patent Document 1). Patent Document 1 discloses a zoom lens in which high-order lateral chromatic aberration and flare caused by diffracted light are suppressed. In this zoom lens, the bending of the sagittal field curvature is well corrected.

  In addition, there are at least five lens groups of negative, positive, negative, positive, and positive refractive power in order from the object side to the image side. Each lens group is moved to perform zooming, and diffractive optics is used to correct chromatic aberration. A zoom lens using an element is known (Patent Document 2). Patent Document 2 discloses a zoom lens in which the chromatic aberration of magnification is favorably corrected over the entire zoom region by optimizing the configuration of each lens group and the arrangement of the diffractive optical elements. In this zoom lens, astigmatism at a low image height at the telephoto end is well corrected.

Japanese Patent Laid-Open No. 2002-244044 JP 2002-156582 A

  In recent years, zoom lenses for digital single-lens reflex cameras are strongly demanded to have high image quality for images taken with a wide angle of view. In general, a negative lead type zoom lens is advantageous for widening the angle of view.

  However, in a negative lead type zoom lens, the power arrangement of the optical system tends to be asymmetric with respect to the entrance pupil. For this reason, on the wide-angle side, the deterioration of the optical performance at the periphery of the screen, that is, the occurrence of various aberrations such as field curvature, astigmatism and distortion increases in other words. Further, in order to correct lateral chromatic aberration, a material having a low refractive index and low dispersion is often used for the positive lens. As a result, the Petzval sum increases in the positive direction, making it difficult to correct astigmatism with a low image height on the telephoto side.

  To reduce chromatic aberration while widening the angle of view, correct various aberrations other than chromatic aberration, and obtain good optical performance over the entire zoom range, set each lens group constituting the zoom lens appropriately. Becomes important. In particular, it is important to appropriately set the refractive power of each lens group and to arrange the diffractive optical element in an appropriate state in the lens group.

  For example, in a zoom lens including lens units having negative, positive, negative, and positive refractive power in order from the object side to the image side, the refractive power of the first and third lens groups, the refractive power of the lens group including the diffractive optical element, and the like It is important to set up properly. If these configurations are inappropriate, a large amount of lateral chromatic aberration occurs at the wide-angle end, and it becomes 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 wide angle of view and high optical performance in the entire zoom range.

The zoom lens according to the present invention includes, in order from the object side to the image side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power, and a positive lens having a positive refractive power. A zoom lens having a fourth lens group and performing zooming by moving at least one lens group along the optical axis,
At least one of the positive refractive power lens groups has at least one diffractive optical portion, and the average of the materials of the positive lenses in the positive refractive power lens group having the diffractive optical portion at the d-line. The refractive index is NDP_ave, the focal length of the positive refractive power lens group having the diffractive optical unit is fD, the focal lengths at the wide-angle end and the telephoto end of the zoom lens are fw and ft, respectively, and the first lens group and the third lens group When the focal length of the lens group is f1 and f3,
0.4 <| NDP_ave / fD × √ (fw · ft) | <1.0
1.8 <f3 / f1 <4.0
It is characterized by satisfying the following conditions.

  According to the present invention, a zoom lens having a wide angle of view and high optical performance in the entire zoom region can be obtained.

Optical sectional view of Numerical Example 1 of the present invention Various aberration diagrams of the first numerical embodiment of the present invention at the wide-angle end, the intermediate zoom position, and the telephoto end Optical sectional view of Numerical Example 2 of the present invention Various aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end of Numerical Example 2 of the present invention Optical sectional view of Numerical Example 3 of the present invention Various aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end of Numerical Example 3 of the present invention Optical sectional view of Numerical Example 4 of the present invention Various aberration diagrams of Numerical Embodiment 4 at the wide-angle end, an intermediate zoom position, and a telephoto end Schematic diagram of main parts of an embodiment 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, 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 positive lens having a positive refractive power. A fourth lens group is included. In zooming, at least one lens group is moved along the optical axis.

  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. 2A, 2B, and 2C are aberrations when the zoom lens of Example 1 is focused at infinity at the wide-angle end, the intermediate zoom position, and the telephoto end (long focal length end), respectively. FIG. Example 1 is a zoom lens having a zoom ratio of 2.06 and an F number of 2.91.

  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. FIGS. 4A, 4B, and 4C are aberration diagrams when the zoom lens of Example 2 is focused on the infinite object distance at the wide-angle end, the intermediate zoom position, and the telephoto end, respectively. The second embodiment is a zoom lens having a zoom ratio of 2.06 and an F number of 2.91.

  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 when the zoom lens of Example 3 is focused on the infinite object distance at the wide-angle end, the intermediate zoom position, and the telephoto end, respectively. Example 3 is a zoom lens having a zoom ratio of 2.06 and an F number of 2.91.

  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. FIGS. 8A, 8B, and 8C are aberration diagrams when the zoom lens of Example 4 is focused on the infinite object distance at the wide-angle end, the intermediate zoom position, and the telephoto end, respectively. Example 4 is a zoom lens having a zoom ratio of 2.06 and an F number of 2.91. FIG. 9 is a schematic diagram of a main part of a single-lens reflex camera (imaging device) including the zoom lens of the present invention.

  The zoom lens of each embodiment is a photographing lens system (optical system) used in an imaging apparatus such as a video camera, a digital 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). The zoom lens of each embodiment may be used for a projector. In this case, the left side is the screen side and the right side is the projected image side. In the lens cross-sectional view, i indicates the order of the lens groups from the object side, and Li is the i-th lens group. SP is an aperture stop (open F number aperture). SSP is a flare cut stop with a constant aperture diameter.

  IP is an image plane, and when used as a photographing optical system for a video camera or a digital still camera, on the imaging surface of a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor, Corresponds to the film surface. In the aberration diagrams, d and g are d-line and g-line, respectively. ΔM and ΔS are a meridional image plane and a sagittal image plane at d-line. Lateral chromatic aberration is represented by the g-line. Fno is the F number, and ω is the half angle of view. In the following embodiments, the wide-angle end and the telephoto end refer to zoom positions when the zooming lens group (for example, the second lens group) is positioned at both ends of a range in which the mechanism can move on the optical axis.

  In each embodiment, in order from the object side to the image side, the first lens unit L1 having a negative refractive power, the second lens unit L2 having a positive refractive power, the third lens unit L3 having a negative refractive power, and a positive refractive power. The fourth lens unit L4. A lens group such as a converter lens or an afocal lens group may be located on at least one of the object side of the first lens group L1 or the image side of the fourth lens group L4. When zooming from the wide-angle end to the telephoto end, the lens units L1 to L4 move on the optical axis as indicated by arrows so that the intervals between the lens units L1 to L4 change.

  Specifically, the change in the distance between the lens units at the telephoto end compared to the wide-angle end is as follows. The air gap between the first lens group L1 and the second lens group L2 is small, the air gap between the second lens group L2 and the third lens group L3 is large, and the third lens group L3 and the fourth lens group L4 The air gap is reduced. During zooming from the wide-angle end to the telephoto end, the first lens unit L1 moves along a locus convex toward the image side. The second to fourth lens units L2 to L4 move to the object side. The aperture stop SP and the flare cut stop SSP move together with the third lens unit L3 during zooming.

  In each embodiment, with the above-described configuration, the entire lens system has a retrofocus type refractive power arrangement at the wide-angle end. Thereby, it is advantageous to widen the angle of view at the wide angle end. In addition, the image plane variation accompanying zooming is corrected by moving the first lens unit L1 nonlinearly during zooming. Focusing from an infinitely distant object to a close object is performed by moving all or part of the second lens unit L2 toward the image side.

  The zoom lens according to each embodiment includes lens groups L1 to L4 having negative, positive, negative, and positive refractive powers in order from the object side to the image side. In the zoom lens configured as described above, when the variable magnification sharing of the third lens unit L3 and the fourth lens unit L4 is increased, the refractive power of each of these lens units is increased. As a result, a large sagittal flare component is generated at the wide angle end due to the strong refractive power of the third lens unit L3 having a negative refractive power close to the aperture stop SP. As a result, the sagittal image plane bends to the over side as the image height increases. In order to correct this, it is necessary to weaken the refractive power of the third lens unit L3. However, if the refractive power of the third lens unit L3 is excessively weakened, a desired zoom ratio cannot be obtained, or the refractive power of the first lens unit L1 is increased, resulting in a large amount of distortion. Therefore, in each embodiment, the sagittal curvature of field is corrected by optimizing the refractive powers of the first lens unit L1 and the third lens unit L3.

  In a zoom lens having the same zoom type as each embodiment, in many cases, when sagittal curvature of curvature occurs, an image plane position at a high image height is reduced by setting the image plane position at a low image height under. Was balanced. However, when the curvature of the sagittal field curvature is corrected, it is necessary to correct the image plane position at a low image height to the over side.

  As a result, the Petzval image plane changes and a lot of astigmatism occurs at the telephoto end. In order to correct this aberration, it is necessary to correct (reduce) the Petzval sum. When the refractive index of the negative lens material is lowered to correct the Petzval sum, the occurrence of various aberrations increases. For this reason, it is conceivable to increase the refractive index of the positive lens material. However, in general, when the refractive index of the positive lens material increases, the Abbe number decreases and a large amount of chromatic aberration occurs. In other words, the sagittal curvature of field curvature at the wide-angle end and the astigmatism and chromatic aberration at a low image height at the telephoto end are correlated with each other, and it has been difficult to correct these simultaneously.

  In order to solve this problem, each embodiment uses a diffractive optical element in which a diffractive optical part (diffractive optical surface) is formed on a lens surface. By using a diffractive optical element, the achromatic degree of freedom is used to increase the refractive index of the material of the positive lens. This facilitates simultaneous correction of sagittal field curvature at the wide angle end and astigmatism at the telephoto end. The lens group using the diffractive optical element is preferably the second lens group L2 or the fourth lens group L4 in which the positive lens material has a low refractive index and low dispersion because the refractive index of the positive lens material is desired to be increased. .

  Further, in consideration of axial chromatic aberration and fluctuations due to zooming of the lateral chromatic aberration, the use of a diffractive optical element in the fourth lens unit L4, which is advantageous for correcting lateral chromatic aberration that occurs greatly at the wide-angle end, has a large correction effect. In each embodiment, a diffractive optical element is used for the fourth lens unit L4. The same effect can be obtained even when the diffractive optical element is used in the second lens unit L2.

In the zoom lens of each embodiment, at least one lens group among the plurality of lens groups having positive refractive power has at least one diffractive optical part. The average refractive index at the d-line of the material of the positive lens in the lens unit having positive refractive power having the diffractive optical part is defined as NDP_ave. Let fD be the focal length of a positive refractive power lens unit having a diffractive optical section. The focal lengths at the wide-angle end and the telephoto end of the zoom lens are fw and ft, respectively. The focal lengths of the first lens group and the third lens group are assumed to be f1 and f3. At this time,
0.4 <| NDP_ave / fD × √ (fw · ft) | <1.0 (1)
1.8 <f3 / f1 <4.0 (2)
It is characterized by satisfying the following conditions.

  In each embodiment, the diffractive optical part refers to a single-layer or multiple-layer diffraction grating formed on the surface of a substrate (for example, a lens). And the diffractive optical element is formed from the base material and the diffractive optical part provided on the base material surface.

  Next, the technical meaning of each conditional expression described above will be described. Conditional expression (1) defines conditions for correcting the Petzval sum well. By increasing the refractive index of the material of each lens of the lens group having the diffractive optical element, it becomes easy to simultaneously correct chromatic aberration and astigmatism at a low image height at the telephoto end. By increasing the average refractive index of the positive lens material in a lens group having a strong positive refractive power, the effect of correcting these various aberrations increases. If the upper limit of the conditional expression (1) is exceeded, the Petzval sum will be excessively corrected, and a large amount of astigmatism will occur. Further, since the Abbe number of the material of the positive lens becomes small, the refractive power of the diffractive optical element becomes strong, and the manufacture becomes difficult. If the lower limit of conditional expression (1) is not reached, the Petzval image surface is not sufficiently corrected, and it becomes difficult to correct astigmatism at the telephoto end.

  Conditional expression (2) defines the ratio of the refractive powers of the first lens unit L1 and the third lens unit L3. By satisfying this conditional expression (2), it becomes easy to satisfactorily correct the curvature of field curvature while suppressing sagittal flare. If the relationship between these refractive powers exceeds the upper limit of the conditional expression (2), the refractive power of the third lens unit L3 becomes small, and it becomes difficult to obtain a desired zoom ratio. Further, the refractive power of the first lens unit L1 becomes too strong, and a lot of distortion is generated. If the lower limit of conditional expression (2) is not reached, the refractive power of the third lens unit L3 becomes too strong, and the curvature of the sagittal field curvature at the wide-angle end increases, or the refractive power of the first lens unit L1 decreases. Too much, the effective diameter of the front lens will increase.

  In each embodiment, the numerical ranges of conditional expressions (1) and (2) are more preferably set as follows.

0.5 <| NDP_ave / fD × √ (fw · ft) | <0.9 (1a)
2.0 <f3 / f1 <3.7 (2a)
As described above, according to each embodiment, the optimal power arrangement of the zoom lens and the effect of changing the glass material by the diffractive optical unit are used for field curvature correction, so that the imaging performance is high over the entire zoom region. A zoom lens can be obtained.

In each embodiment, it is more preferable to satisfy one or more of the following conditions. Let fDOE be the focal length of the diffractive optical section in the air. An aperture stop is provided in the optical path, and the distance from the aperture stop to the diffractive optical unit at the wide angle end is dDOE, and the total lens length (the distance from the first lens surface to the image plane) of the zoom lens is Lw. At this time,
40 <fDOE / √ (fw · ft) <300 (3)
0.2 <dDOE / Lw (4)
−1.3 <f1 / √ (fw · ft) <− 0.8 (5)
−3.9 <f3 / √ (fw · ft) <− 2.0 (6)
1.52 <NDP_ave <1.78 (7)
It is preferable to satisfy one or more of the following conditional expressions.

  Next, the technical meaning of each embodiment will be described. Conditional expression (3) defines the refractive power of the diffractive optical part. If the refractive power of the diffractive optical part exceeds the upper limit of the conditional expression (3), the grating pitch of the diffractive optical part becomes small, which makes manufacturing difficult. If the lower limit of conditional expression (3) is not reached, it is difficult to increase the refractive index of the material of the positive lens in the lens group including the diffractive optical element, and the Petzval image plane is not sufficiently corrected. It becomes difficult to correct aberrations satisfactorily.

  Conditional expression (4) appropriately defines the position of the diffractive optical part disposed in the optical path. In general, in a negative lead type zoom lens, lateral chromatic aberration is greatly generated at the wide-angle end. Therefore, the material of the positive lens in the lens unit having a positive refractive power arranged at a position away from the aperture stop SP in the optical axis direction tends to have a low refractive index and low dispersion. This increases the effect of correcting chromatic aberration. If the lower limit of the conditional expression (4) is not reached, the Petzval image plane is not sufficiently corrected, and a lot of astigmatism occurs at the telephoto end.

  Conditional expressions (5) and (6) define the focal lengths f1 and f3. Among these, the conditional expression (5) defines the negative refractive power of the first lens unit L1. If the upper limit of conditional expression (5) is exceeded, the negative refractive power of the first lens unit L1 will become strong and a lot of distortion will occur. If the lower limit of conditional expression (5) is not reached, the negative refractive power of the first lens unit L1 becomes small, and the front lens effective diameter increases.

  Conditional expression (6) defines the negative refractive power of the third lens unit L3. If the lower limit of conditional expression (6) is not reached, the negative refractive power of the third lens unit L3 becomes small, making it difficult to obtain a desired zoom ratio. If the upper limit of conditional expression (6) is exceeded, the refractive power of the third lens unit L3 becomes too strong, and the curvature of the sagittal field curvature becomes large at the wide angle end.

  Conditional expression (7) defines the average refractive index NDp_ave of the positive lens material in the positive refractive power lens group having the diffractive optical element. If the upper limit of the conditional expression (7) is exceeded, Petzval sum correction becomes excessive, and astigmatism increases in many cases. Further, since the Abbe number of the material of the positive lens becomes small, the refractive power of the diffractive optical part becomes strong, and the manufacture becomes difficult. If the lower limit of conditional expression (7) is not reached, the Petzval image plane will not be sufficiently corrected, and it will be difficult to satisfactorily correct astigmatism at the telephoto end. Preferably, the numerical ranges of conditional expressions (3) to (7) are set as follows.

50 <fDOE / √ (fw · ft) <250 (3a)
0.25 <dDOE / Lw (4a)
−1.1 <f1 / √ (fw · ft) <− 0.85 (5a)
−3.6 <f3 / √ (fw · ft) <− 2.0 (6a)
1.52 <NDP_ave <1.70 (7a)
Next, the features of the lens configuration of each example will be described.

[Example 1]
In Example 1, a blazed diffraction grating (diffractive optical unit) B.B which is rotationally symmetric with respect to the cemented surface of the cemented lens L4G closest to the image plane of the fourth lens unit L4. O is formed. Thereby, the average refractive index of the positive lens material of the fourth lens unit L4 is increased to 1.63515. As a result, the ratio of refractive power of the first lens unit L1 and the third lens unit L3 is optimized to correct the curvature of the sagittal field curvature, and the Petzval image surface is optimally corrected. The point aberration is also corrected well at the same time.

[Example 2]
The lens configuration of Example 2 is the same as that of Example 1. In Example 2, a blazed diffraction grating (diffraction optical unit) B.B which is rotationally symmetric with respect to the cemented surface of the cemented lens L4G closest to the image plane of the fourth lens unit L4. O is formed. This increases the average refractive index of the positive lens material of the fourth lens unit L4 to 1.53531. As a result, the ratio of refractive power of the first lens unit L1 and the third lens unit L3 is optimized to correct the curvature of the sagittal field curvature, and the Petzval image surface is optimally corrected. The point aberration is also corrected well at the same time.

[Example 3]
The lens configuration of the third embodiment is the same as that of the first embodiment except for the lens configuration of the fourth lens unit L4. B. A blazed diffraction grating (diffractive optical part) that is rotationally symmetric to the cemented surface of the cemented lens L4G closest to the image plane of the fourth lens unit L4. O is formed. This increases the average refractive index of the positive lens material of the fourth lens unit L4 to 1.59092. As a result, the ratio of refractive power of the first lens unit L1 and the third lens unit L3 is optimized to correct the curvature of the sagittal field curvature, and the Petzval image surface is optimally corrected. The point aberration is also corrected well at the same time.

[Example 4]
The lens configuration of the fourth embodiment is the same as that of the first embodiment except for the lens configuration of the fourth lens unit L4. B. A blazed diffraction grating (diffractive optical part) that is rotationally symmetric to the cemented surface of the cemented lens L4G closest to the image plane of the fourth lens unit L4. O is formed. This increases the average refractive index of the positive lens of the fourth lens unit L4 to 1.53896. As a result, the ratio of refractive power of the first lens unit L1 and the third lens unit L3 is optimized to correct the curvature of the sagittal field curvature, and the Petzval image surface is optimally corrected. The point aberration is also corrected well at the same time.

  Next, numerical examples of the present invention will be shown. In the numerical examples, i indicates the order of the surfaces from the object side. ri is the radius of curvature of the lens surface, di is the lens thickness and air spacing, and ndi and νdi are the refractive index and Abbe number for the d-line of the lens, respectively. The aspherical shape is given by the following equation using R as a paraxial radius of curvature and using aspherical coefficients K, A4, A6, A8, A10, and A12.

^{X = (H 2 / R)} / [1+ {1- (1 + K) (H / R) 2} 1/2]
+ A4H ⁴ + A6H ⁶ + A8H ⁸ + A10H ¹⁰ + A12H ¹²
“E-X” means “× 10 ^−X ”. Further, the phase shape φ (h, m) of the diffractive surface (diffractive optical part) 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 λ 0, and the phase coefficient is Ci. (I = 1,2,3 ...)
φ (h, m) = {2π / (mλ0)} (C2 · h ² + C4 · h ⁴ + C6 · h ⁶ )
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). The power of the diffractive optical part (the reciprocal of the focal length fDOE) φD is φD = 1 / fDOE = −2 · C2
It becomes. Table 1 shows the relationship between each conditional expression described above and each embodiment.

(Numerical example 1)
Surface data surface number rd nd νd Effective diameter
1 * 219.522 2.30 1.77250 49.6 49.45
2 20.713 10.16 35.44
3 314.794 1.80 1.80610 40.9 34.61
4 34.749 0.16 1.51640 52.2 31.16
5 * 53.243 6.23 31.11
6 -79.552 1.60 1.83400 37.2 30.70
7 267.676 0.15 30.65
8 52.707 4.50 1.80518 25.4 30.80
9 -257.033 (variable) 30.39
10 48.891 1.30 1.80518 25.4 24.98
11 24.529 6.20 1.56732 42.8 25.14
12 -79.728 0.15 25.56
13 143.990 2.55 1.80 400 46.6 25.93
14 132.175 3.53 26.02
15 45.385 3.80 1.58313 59.4 27.12
16 * -88.867 (variable) 27.05
17 (Aperture) ∞ 1.90 22.91
18 -278.038 1.40 1.88300 40.8 22.37
19 241.463 1.86 22.12
20 -50.981 1.10 1.76200 40.1 22.06
21 32.175 4.50 1.78470 26.3 22.48
22 -173.216 1.00 22.66
23 ∞ (variable) 22.73
24 65.410 1.20 1.84666 23.8 22.79
25 32.394 0.20 22.50
26 25.324 6.00 1.59240 68.3 23.86
27 -55.308 0.20 24.23
28 -869.003 1.20 1.83481 42.7 24.37
29 (Diffraction) 16.136 6.95 1.67790 55.3 24.82
30 * -74.785 24.94

Aspheric data 1st surface
K = 5.84190e + 001 A 4 = 1.75507e-005 A 6 = -2.90049e-008
A 8 = 3.95614e-011 A10 = -2.97382e-014 A12 = 7.31017e-018

5th page
K = 4.83052e + 000 A 4 = 2.09635e-005 A 6 = -1.20311e-008
A 8 = -7.80772e-011 A10 = 2.89323e-013 A12 = -4.88915e-016

16th page
K = -3.45315e + 000 A 4 = -2.22271e-008 A 6 = -7.78824e-010
A 8 = -1.02146e-012 A10 = 9.05549e-014 A12 = -2.31917e-016

29th surface (diffractive surface)
C 2 = -1.38871e-004 C 4 = 3.05998e-007 C 6 = -3.36691e-009

30th page
K = -9.68073e + 000 A 4 = 4.21267e-006 A 6 = 3.96878e-008
A 8 = -1.12252e-010 A10 = 2.35038e-013 A12 = 1.53617e-015

Various data focal length 16.48 24.00 33.95
F number 2.91 2.91 2.91
Angle of view 52.70 42.04 32.51

d 9 26.22 10.49 0.99
d16 0.93 6.58 11.78
d23 11.50 6.20 0.19

(Numerical example 2)
Surface data surface number rd nd νd Effective diameter
1 * 246.712 2.30 1.77250 49.6 49.16
2 21.684 9.73 35.84
3 426.521 1.80 1.80400 46.6 35.01
4 36.953 0.16 1.51640 52.2 31.52
5 * 42.521 7.02 30.99
6 -71.206 1.60 1.77250 49.6 30.59
7 495.944 0.15 30.62
8 54.279 4.50 1.72825 28.5 30.75
9 -187.617 (variable) 30.39
10 56.510 1.30 1.80518 25.4 26.42
11 24.529 6.20 1.56732 42.8 26.72
12 -275.767 0.15 27.31
13 112.755 2.55 1.80 400 46.6 27.89
14 360.386 3.90 28.12
15 59.137 4.20 1.62299 58.2 29.66
16 -71.678 (variable) 29.64
17 (Aperture) ∞ 1.90 24.89
18 -129.986 1.40 1.88300 40.8 24.47
19 -671.169 1.86 24.32
20 -49.506 1.10 1.90366 31.3 24.23
21 89.850 4.50 1.92286 18.9 24.73
22 * -92.175 0.83 25.12
23 ∞ (variable) 25.10
24 60.482 1.20 1.84666 23.9 25.09
25 42.383 0.20 24.75
26 21.130 6.50 1.48749 70.2 25.13
27 -65.057 0.20 24.70
28 1089.271 1.20 1.83400 37.2 23.54
29 (Diffraction) 15.973 6.95 1.58313 59.4 22.63
30 * -99.255 23.14

Aspheric data 1st surface
K = 6.80273e + 001 A 4 = 1.77449e-005 A 6 = -2.98598e-008
A 8 = 4.20411e-011 A10 = -3.43840e-014 A12 = 1.09582e-017

5th page
K = 3.00620e + 000 A 4 = 2.06840e-005 A 6 = -1.20085e-008
A 8 = -1.03876e-010 A10 = 2.92622e-013 A12 = -4.71360e-016

22nd page
K = 1.91671e + 001 A 4 = 2.12751e-006 A 6 = -5.59247e-009
A 8 = 5.08730e-011 A10 = -8.56586e-015 A12 = -2.26945e-016

29th surface (diffractive surface)
C 2 = -9.63435e-005 C 4 = 1.49958e-007 C 6 = -2.75452e-009

30th page
K = -2.62398e + 001 A 4 = 1.42365e-005 A 6 = 6.57748e-008
A 8 = -3.67087e-011 A10 = 1.56014e-013 A12 = 4.90435e-015

Various data focal length 16.48 24.01 33.95
F number 2.91 2.91 2.91
Angle of view 52.70 42.03 32.51

d 9 27.59 11.98 2.37
d16 0.93 7.56 13.14
d23 12.70 6.86 0.16

(Numerical Example 3)
Surface data surface number rd nd νd Effective diameter
1 * 241.841 2.30 1.77250 49.6 50.01
2 21.342 10.33 35.89
3 -2931.562 1.80 1.80400 46.6 35.24
4 34.274 0.16 1.51640 52.2 31.59
5 * 45.178 4.95 31.52
6 -245.096 1.60 1.83481 42.7 31.34
7 219.105 0.15 31.08
8 43.900 4.50 1.80518 25.4 30.94
9 253.686 (variable) 30.16
10 64.989 1.30 1.80518 25.4 24.45
11 24.529 5.70 1.56732 42.8 24.90
12 -210.325 0.15 25.57
13 69.821 2.55 1.80 400 46.6 26.42
14 503.543 6.39 26.54
15 78.309 3.80 1.62299 58.2 27.94
16 * -83.475 (variable) 27.91
17 (Aperture) ∞ 1.90 24.42
18 -198.029 1.40 1.88300 40.8 24.01
19 161.330 1.86 23.82
20 -50.660 1.10 1.76200 40.1 23.82
21 34.993 5.00 1.84666 23.8 24.74
22 -179.538 0.73 25.08
23 ∞ (variable) 25.26
24 * 24.119 8.50 1.56384 60.7 25.83
25 -19.665 1.20 1.83400 37.2 25.80
26 -30.224 0.20 25.84
27 -231.106 1.20 1.83400 37.2 24.41
28 (Diffraction) 15.884 6.95 1.61800 63.4 23.76
29 * -656.593 24.15

Aspheric data 1st surface
K = 7.06891e + 001 A 4 = 1.65970e-005 A 6 = -2.75627e-008
A 8 = 3.69994e-011 A10 = -3.06736e-014 A12 = 1.02856e-017

5th page
K = 5.11918e + 000 A 4 = 1.56334e-005 A 6 = -3.87222e-008
A 8 = -6.42607e-011 A10 = 2.33257e-013 A12 = -8.23021e-016

16th page
K = 3.98267e + 000 A 4 = -4.95014e-007 A 6 = 8.39354e-010
A 8 = -2.02552e-012 A10 = 1.09063e-013 A12 = -3.37969e-016

24th page
K = -6.29012e-001 A 4 = 1.54969e-006 A 6 = -4.82485e-009
A 8 = 7.16935e-012 A10 = -3.50818e-014 A12 = 1.17335e-016

28th surface (diffractive surface)
C 2 = -1.19327e-004

29th page
K = -2.94321e + 002 A 4 = 1.78191e-005 A 6 = 4.89413e-008
A 8 = -2.04329e-010 A10 = 5.36861e-013 A12 = -5.64474e-016

Various data focal length 16.48 24.00 33.95
F number 2.91 2.91 2.91
Angle of view 52.70 42.03 32.51

d 9 23.85 10.19 2.31
d16 0.93 6.65 11.76
d23 12.35 6.26 0.13

(Numerical example 4)
Surface data surface number rd nd νd Effective diameter
1 * 641.627 2.30 1.58313 59.4 57.11
2 22.265 13.37 39.86
3 -3092.678 1.80 1.88300 40.8 37.97
4 35.147 0.16 1.51640 52.2 33.23
5 * 46.818 7.09 32.69
6 -77.036 1.60 1.74400 44.8 32.50
7 1024.935 0.15 32.52
8 48.936 4.50 1.80518 25.4 32.61
9 -2422.950 (variable) 32.13
10 57.004 1.30 1.80518 25.4 24.78
11 24.529 6.20 1.56732 42.8 25.01
12 -114.293 0.15 25.56
13 114.535 2.55 1.80 400 46.6 26.04
14 229.658 4.35 26.17
15 56.732 3.80 1.62299 58.2 27.30
16 * -74.786 (variable) 27.24
17 (Aperture) ∞ 1.90 24.28
18 -105.464 1.40 1.88300 40.8 23.84
19 196.553 1.86 23.66
20 -45.002 1.10 1.76200 40.1 23.66
21 25.847 5.50 1.78470 26.3 24.90
22 -98.042 1.23 25.19
23 ∞ (variable) 25.48
24 37.158 8.50 1.51633 64.1 25.87
25 -20.449 1.20 1.84666 23.9 25.60
26 -30.551 0.20 26.04
27 413.247 1.20 1.83400 37.2 24.20
28 (Diffraction) 26.725 6.95 1.51742 52.4 23.13
29 -360.016 0.20 24.31
30 193.101 2.90 1.58313 59.4 24.63
31 * -1001.484 25.20

Aspheric data 1st surface
K = 6.72936e + 001 A 4 = 1.76336e-005 A 6 = -2.35027e-008
A 8 = 3.32002e-011 A10 = -2.73401e-014 A12 = 1.11503e-017

5th page
K = 3.83163e + 000 A 4 = 2.20481e-005 A 6 = -5.42322e-009
A 8 = -9.28023e-011 A10 = 3.52776e-013 A12 = -5.43046e-016

16th page
K = 6.78966e-001 A 4 = 1.60837e-007 A 6 = -1.54811e-009
A 8 = 4.84837e-012 A10 = 6.44025e-014 A12 = -3.00848e-016

28th surface (diffractive surface)
C 2 = -3.09599e-004

No. 31
K = -1.73994e + 001 A 4 = 1.08574e-005 A 6 = 3.13078e-008
A 8 = -1.24047e-010 A10 = 5.43286e-013 A12 = -8.12756e-016

Various data focal length 16.48 23.98 33.95
F number 2.91 2.91 2.91
Angle of view 52.70 42.05 32.51

d 9 27.53 10.67 0.21
d16 0.93 4.90 7.10
d23 7.96 4.37 0.36

  Next, an embodiment of a single-lens reflex camera system using the zoom lens (optical system) of the present invention will be described with reference to FIG. In FIG. 9, 10 is a single-lens reflex camera body, and 11 is an interchangeable lens equipped with a zoom lens according to the present invention. Reference numeral 12 denotes a recording unit such as a film or a solid-state imaging device that records (receives) a subject image formed through the interchangeable lens 11, and 13 denotes a finder optical system that observes the subject image from the interchangeable lens 11. Reference numeral 14 denotes a rotating quick return mirror for switching and transmitting the subject image from the interchangeable lens 11 to the recording means 12 and the finder optical system 13. 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.

  Thus, by applying the zoom lens of the present invention to an imaging apparatus such as a single-lens reflex camera interchangeable lens, an imaging apparatus having high optical performance can be realized. The present invention can be similarly applied to an SLR (Single Lens Reflex) camera having no quick return mirror.

  As described above, according to each embodiment, it is possible to obtain a compact zoom lens having excellent optical performance and an imaging apparatus having the same, which are suitable for an imaging system using a solid-state imaging device.

L1 1st lens group L2 2nd lens group L3 3rd lens group L4 4th lens group SP Aperture IP image surface dd line g g line ΔM meridional image surface ΔS sagittal image surface

Claims (6)

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 group having a positive refractive power are provided. A zoom lens that performs zooming by moving at least one lens group along the optical axis,
At least one of the positive refractive power lens groups has at least one diffractive optical portion, and the average of the materials of the positive lenses in the positive refractive power lens group having the diffractive optical portion at the d-line. The refractive index is NDP_ave, the focal length of the positive refractive power lens group having the diffractive optical unit is fD, the focal lengths at the wide-angle end and the telephoto end of the zoom lens are fw and ft, respectively, and the first lens group and the third lens group When the focal length of the lens group is f1 and f3,
0.4 <| NDP_ave / fD × √ (fw · ft) | <1.0
1.8 <f3 / f1 <4.0
A zoom lens characterized by satisfying the following conditions: When the focal length in the air of the diffractive optical unit is fDOE,
40 <fDOE / √ (fw · ft) <300
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. When having an aperture stop, when the distance from the aperture stop to the diffractive optical unit at the wide angle end is dDOE, and the total lens length of the zoom lens is Lw,
0.2 <dDOE / Lw
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. The focal lengths f1 and f3 of the first lens group and the third lens group are:
−1.3 <f1 / √ (fw · ft) <− 0.8
−3.9 <f3 / √ (fw · ft) <− 2.0
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. The average refractive index NDp_ave at the d-line of the positive lens material in the positive refractive power lens group having the diffractive optical part is 1.52 <NDP_ave <1.78.
The zoom lens according to claim 1, wherein the following conditional expression is satisfied.   6. 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.