JP2019132919A - Zoom lens and image capturing device having the same - Google Patents

Abstract

To provide a zoom lens which is compact, has a wide view angle, and yet features magnification chromatic aberration that is sufficiently reduced over an entire zoom range for a wide wavelength range from the visible light to near-infrared light, and to provide an image capturing device having the same.SOLUTION: A zoom lens of the present invention comprises a first lens group L1 having negative refractive power and a rear group LR including a lens group LP having positive refractive power, arranged in order from the object side to the image side, and is configured such that a distance between each pair of adjacent lens groups changes while zooming. At least one lens group has a cemented lens having a diffraction optical element at a cemented surface. An aperture stop SP is disposed on the object side relative to the lens group LP. The lens group LP has two positive lenses and is configured to move toward the object side when zooming from the wide-angle end to the telephoto end. A focal length of the first lens group L1 and a focal length of the lens group Lp are set appropriately.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a zoom lens and an imaging apparatus having the same, and is suitable for, for example, a camera using a solid-state imaging device such as a video camera, an electronic still camera, a broadcast camera, a surveillance camera, or a camera using a silver salt film. Is.

As a zoom lens used in an imaging apparatus, a lens having a short overall lens length, a wide angle of view, and a high resolution is required.
Especially for surveillance cameras, there is a demand for an imaging device capable of executing the night mode, and thus chromatic aberration correction in a wide wavelength region is required.

  Patent Documents 1 and 2 disclose a first lens group having negative refractive power, which is arranged in order from the object side to the image side, as a zoom lens having a good optical performance while having a wide angle of view, and a subsequent lens. And a negative lead type zoom lens having a diffractive optical element.

JP 2002-156582 A International Publication No. 2013/128856

In the zoom lenses disclosed in Patent Documents 1 and 2, the chromatic aberration of magnification is not sufficiently reduced in a wide wavelength region from visible light to near infrared light in the entire zoom range.
Therefore, the present invention has an object to provide a zoom lens in which magnification chromatic aberration is sufficiently reduced in a wide wavelength region from visible light to near infrared light in the entire zoom range, and an image pickup apparatus having the same while having a compact and wide angle of view. To do.

The zoom lens according to the present invention includes a first lens group having a negative refractive power and a rear group including a lens group LP having a positive refractive power, which are arranged in order from the object side to the image side, and are adjacent to each other during zooming. A zoom lens in which the distance between groups is changed. At least one lens group includes a cemented lens having a diffractive optical part on the cemented surface, and an aperture stop is disposed on the object side of the lens group LP. The lens group LP has two positive lenses, moves to the object side during zooming from the wide-angle end to the telephoto end, and the focal length of the first lens group is f1, and the focal length of the lens group LP is fp. When
−1.50 <f1 / fp <−0.20
The following conditional expression is satisfied.

  According to the present invention, it is possible to obtain a zoom lens in which magnification chromatic aberration is sufficiently reduced in a wide wavelength range from visible light to near infrared light in the entire zoom range and an imaging apparatus having the same while having a compact and wide field angle. it can.

FIG. 3 is a lens cross-sectional view when focusing on an object at infinity at the wide-angle end of the zoom lens according to the first exemplary embodiment. FIG. 6 is a diagram illustrating various aberrations when an object at infinity is in focus at the wide-angle end, the intermediate zoom position, and the telephoto end of the zoom lens according to the first exemplary embodiment. FIG. 6 is a lens cross-sectional view when focusing on an object at infinity at the wide-angle end of the zoom lens according to the second exemplary embodiment. FIG. 6 is a diagram illustrating various aberrations when an object at infinity is in focus at the wide-angle end, the intermediate zoom position, and the telephoto end of the zoom lens according to the second exemplary embodiment. FIG. 10 is a lens cross-sectional view when focusing on an object at infinity at the wide-angle end of the zoom lens according to Embodiment 3; FIG. 10 is a diagram illustrating various aberrations when the zoom lens of Example 3 is focused on an object at infinity at the wide-angle end, the intermediate zoom position, and the telephoto end. FIG. 10 is a lens cross-sectional view when focusing on an object at infinity at the wide-angle end of the zoom lens according to Embodiment 4; FIG. 12 is a diagram illustrating various aberrations when the zoom lens of Example 4 is focused on an object at infinity at the wide-angle end, the intermediate zoom position, and the telephoto end. FIG. 10 is a lens cross-sectional view when focusing on an object at infinity at the wide-angle end of the zoom lens according to Embodiment 5; FIG. 12 is a diagram illustrating various aberrations when an object at infinity is in focus at the wide-angle end, the intermediate zoom position, and the telephoto end of the zoom lens according to the fifth exemplary embodiment. 1 is a schematic view of a main part of an imaging apparatus having a zoom lens according to the present invention. 1 is a schematic view of a main part of an imaging apparatus having a zoom lens according to the present invention.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a lens cross-sectional view when focusing on an object at infinity at the wide angle end (short focal length end) of the zoom lens according to Embodiment 1 of the present invention. 2A, 2 </ b> B, and 2 </ b> C are each focused on an object at infinity at the wide-angle end, the intermediate zoom position, and the telephoto end (long focal length end) of the zoom lens of Embodiment 1. FIG.

  FIG. 3 is a lens cross-sectional view when focusing on an object at infinity at the wide-angle end of the zoom lens according to Embodiment 2 of the present invention. 4A, 4B, and 4C are longitudinal aberration diagrams when focusing on an object at infinity at the wide-angle end, the intermediate zoom position, and the telephoto end of the zoom lens of Example 2, respectively. .

  FIG. 5 is a lens cross-sectional view when focusing on an object at infinity at the wide-angle end of the zoom lens according to Embodiment 3 of the present invention. FIGS. 6A, 6B, and 6C are longitudinal aberration diagrams when focusing on an object at infinity at the wide-angle end, the intermediate zoom position, and the telephoto end of the zoom lens according to Embodiment 3, respectively. .

  FIG. 7 is a lens cross-sectional view when focusing on an object at infinity at the wide-angle end of the zoom lens according to Embodiment 4 of the present invention. FIGS. 8A, 8B, and 8C are longitudinal aberration diagrams when focusing on an object at infinity at the wide-angle end, the intermediate zoom position, and the telephoto end of the zoom lens of Example 4, respectively. .

  FIG. 9 is a lens cross-sectional view when focusing on an object at infinity at the wide-angle end of the zoom lens according to Embodiment 5 of the present invention. 10A, 10B, and 10C are longitudinal aberration diagrams when focusing on an object at infinity at the wide-angle end, the intermediate zoom position, and the telephoto end of the zoom lens of Example 5, respectively. .

  An arrow drawn with a solid line in the lens cross-sectional view indicates a movement locus of each lens unit during zooming. In addition, an arrow drawn with a dotted line in the lens cross-sectional view indicates a movement locus of the focus group when the zoom lens is focused on the closest object.

  In the longitudinal aberration diagram, with respect to spherical aberration and lateral chromatic aberration, the solid line is d line (wavelength 587.56 nm), the two-dot chain line is g line (wavelength 435.84 nm), the broken line is F line (wavelength 486.13 nm), and the one-dot chain line is The C line (wavelength 656.27 nm) and the dotted line indicate the wavelength 850 nm. Regarding astigmatism, a broken line and a solid line indicate the meridional image surface and the sagittal image surface of the d line, respectively. Fno represents the F number, and ω represents the shooting half angle of view. Further, spherical aberration is drawn on a scale of 0.2 mm, astigmatism is 0.2 mm, distortion is 50%, and lateral chromatic aberration is drawn on a scale of 0.05 mm.

The zoom lens of each embodiment includes a first lens unit L1 having a negative refractive power and a lens unit having a positive refractive power (hereinafter simply referred to as “positive lens group”), which are arranged in order from the object side to the image side. And a rear group LR including LP, and a variable stop (aperture stop) SP is disposed on the image side of the first lens unit L1, and the distance between adjacent lens units changes during zooming. .
The positive lens group LP included in the rear group LR monotonically moves from the image side to the object side during zooming from the wide-angle end to the telephoto end, is disposed on the image side from the variable stop SP, and has two or more positive refractions. A lens having power (hereinafter simply referred to as “positive lens”).
The zoom lens of each embodiment has at least one cemented lens formed by bonding a plurality of lenses, and has a diffractive optical element DOE (diffractive optical unit) on the cemented surface of at least one cemented lens.

Here, when the focal length of the first lens unit L1 is f1, and the focal length of the positive lens unit LP included in the rear unit LR is fp, the zoom lens of each embodiment has −1.50 <f1 / fp <−. 0.20 ... (1)
The following conditional expression is satisfied.

  The zoom lens of each embodiment is small and lightweight, has a wide angle of view, and is arranged in order from the object side in order to satisfactorily correct aberrations. The first lens unit L1 having negative refractive power is disposed in order. And a rear group LR including the positive lens group LP.

The positive lens group LP included in the rear group LR is configured to move monotonously from the image side to the object side during zooming from the wide-angle end to the telephoto end in order to efficiently perform zooming.
In addition, when the positive lens group LP included in the rear lens group LR is monotonically moved from the image side to the object side during zooming from the wide-angle end to the telephoto end, the zoom lens can be downsized and aberration generated in the zoom lens. Variations can be suppressed.
Further, the positive lens group LP included in the rear group LR is arranged on the image side from the variable stop SP in order to improve the spherical aberration and the coma aberration well by increasing the position where the axial ray passes particularly at the wide angle end. In addition, the configuration has two or more positive lenses.

Further, the zoom lens of each embodiment has a diffractive optical element DOE in order to correct chromatic aberration.
Here, the Abbe number νddoe for the d-line of the diffractive optical element DOE and the partial dispersion ratio θCtdoe for the C-line and t-line are the wavelengths of the d-line, C-line, F-line, and t-line, respectively, λd, λC, λF, λt Is expressed by the following formulas (A) and (B).
νddoe = λd / (λF−λC) (A)
θCtdoe = (λC−λt) / (λF−λC) (B)

From the expressions (A) and (B), the Abbe number νddo and the partial dispersion ratio θCtdoe of the diffractive optical element DOE provided in the zoom lens of each embodiment are −3.45 and 2.10.
The dispersion characteristic of the diffractive surface of the diffractive optical element DOE has a negative value, and has an action opposite to that of a general optical material. Moreover, since the partial dispersion ratio θCtdoe of the C-line and the t-line of the diffractive optical element DOE is larger than that of a general optical material, it can be used for a lens system to widen the range from visible light to near infrared light. This is very effective for correcting chromatic aberration over the wavelength range.

  The diffractive optical element DOE is preferably joined in a form sandwiched between the optical element A and the optical element B. The diffractive optical element DOE is generally made of a UV curable resin. However, when used in a state exposed to the outside air, the diffraction efficiency decreases due to secular change, and the optical performance deteriorates. Specifically, the refractive index and shape of the diffractive optical element DOE change due to water absorption, and the diffraction efficiency decreases. Therefore, by joining the diffractive optical element DOE so as to be sandwiched between the optical element A and the optical element B, it is possible to suppress a decrease in diffraction efficiency due to water absorption.

Next, the technical meaning of conditional expression (1) will be described.
Conditional expression (1) defines the value of the ratio between the focal length of the first lens unit L1 and the focal length of the positive lens unit LP included in the rear unit LR (hereinafter simply referred to as “ratio”). It is a formula. When the focal length ratio is below the lower limit value of the conditional expression (1), the negative focal length of the first lens unit L1 becomes too long (the absolute value of the focal length becomes too large), and a wide angle of view is obtained at the wide angle end. Since it becomes difficult to ensure, it is not preferable.
On the other hand, when the focal length ratio exceeds the upper limit value of the conditional expression (1), the negative focal length of the first lens unit L1 becomes too short (the absolute value of the focal length becomes too small), and various aberrations occur on the wide angle side. In particular, this is not preferable because it is difficult to correct lateral chromatic aberration.

The first lens unit L1 includes at least one positive lens, and the refractive index and the Abbe number for the d-line of any one of the at least one positive lens included in the first lens unit L1 are Nd1p, Let νd1p. In addition, an Abbe number related to the d-line of any positive lens among at least two positive lenses included in the positive lens group LP included in the rear group LR is represented by νdpp. The focal length at the wide-angle end and the focal length at the telephoto end of the zoom lens of each embodiment are defined as fw and ft, respectively.
Note that the Abbe number for the d-line is as follows, where the refractive indices for the d-line, C-line, and F-line are nd, nC, and nF, respectively.
νd = (nd−1) / (nF−nC) (C)
It is expressed as
Further, the focal length of the diffractive optical element DOE is fdoe, and the focal length fdoe is obtained by using the phase coefficient C2 of the diffraction grating. Fdoe = −1 / (2 × C2) (D)
It is expressed as
At this time, in the zoom lens of each embodiment, it is more preferable to satisfy one or more of the following conditional expressions.
1.80 <Nd1p <2.50 (2)
10 <νd1p <40 (3)
80 <νdpp (4)
50.0 <| fdoe / fw | <2000.0 (5)
−5.0 <f1 / fw <−0.5 (6)
0.5 <fp / ft <3.0 (7)

Conditional expressions (2) and (3) are expressions relating to the material properties of at least one positive lens included in the first lens unit L1.
Exceeding the upper limit value of conditional expression (2) is not preferable because spherical aberration occurring particularly at the telephoto end tends to increase in the under direction. On the other hand, if the lower limit of conditional expression (2) is not reached, the spherical aberration occurring at the telephoto end tends to increase in the over direction, which is not preferable. Further, it is necessary to reduce the radius of curvature or increase the lens thickness in order to obtain the power of the positive lens, which is not preferable because it prevents miniaturization.

Conditional expression (3) is a condition related to correction of chromatic aberration, and chromatic aberration generated in a lens having negative refractive power (hereinafter simply referred to as “negative lens”) included in the first lens unit L1 is expressed by the conditional expression. It can be canceled by using a positive lens that satisfies (3).
If the lower limit of conditional expression (3) is not reached, lateral chromatic aberration will increase over the entire zoom range. For example, aberrations on the short wavelength side such as g-line and F-line with respect to d-line increase in the over direction, which is not preferable. On the other hand, when the upper limit value of conditional expression (3) is exceeded, the chromatic aberration of magnification increases in the entire zoom range, similarly to when the lower limit value is exceeded. In this case, aberrations on the short wavelength side such as g-line and F-line with respect to d-line increase in the under direction, which is not preferable.

Conditional expression (4) is an expression relating to the material characteristics of at least two positive lenses included in the positive lens group LP included in the rear group LR. Conditional expression (4) is a condition relating to correction of axial chromatic aberration in particular, and by using a positive lens that satisfies conditional expression (4) at a position where the passage of axial rays is high, axial chromatic aberration is excellent over the entire zoom range. Can be corrected.
If the lower limit of conditional expression (4) is not reached, the correction of longitudinal chromatic aberration will be insufficient. In order to correct it well, it is necessary to weaken the refractive power of each lens group. However, in this case, the entire lens length becomes large in order to ensure a wide angle and a high zoom ratio, which is not preferable.

Conditional expression (5) defines the ratio between the focal length of the diffractive optical element DOE and the focal length at the wide-angle end of the zoom lens.
If the lower limit of conditional expression (5) is not reached, the focal length of the diffractive optical element DOE becomes too small and the lateral chromatic aberration is overcorrected, which is not preferable. If the lower limit of conditional expression (5) is not reached, the focal length at the wide-angle end of the zoom lens becomes too long, and it is difficult to ensure a wide angle of view at the wide-angle end.
On the other hand, if the upper limit value of conditional expression (5) is exceeded, the focal length of the diffractive optical element DOE becomes too large, and the chromatic aberration of magnification becomes insufficiently corrected. If the upper limit of conditional expression (5) is exceeded, the focal length of the first lens unit L1 becomes too short, and it becomes difficult to correct various aberrations on the wide-angle side, particularly lateral chromatic aberration.

Conditional expression (6) defines the ratio between the focal length of the first lens unit L1 and the focal length at the wide-angle end of the zoom lens.
Below the lower limit of conditional expression (6), the negative focal length of the first lens unit L1 becomes too long (the absolute value of the focal length becomes too large), and it is difficult to ensure a wide angle of view at the wide angle end. Therefore, it is not preferable.
On the other hand, when the upper limit value of conditional expression (6) is exceeded, the negative focal length of the first lens unit L1 becomes too short (the absolute value of the focal length becomes too small), and occurs in the first lens unit L1 over the entire zoom range. This is not preferable because the curvature of field and the distortion are increased and correction for fluctuations in zooming becomes difficult.

Conditional expression (7) is an expression that defines the ratio between the focal length of the positive lens group LP included in the rear lens group LR and the focal length at the telephoto end of the zoom lens.
If the lower limit value of conditional expression (7) is not reached, the focal length of the positive lens group LP included in the rear lens group LR becomes too short, and spherical aberration and coma aberration occur greatly over the entire zoom range, and suppression of fluctuations in zooming is suppressed. Since it becomes difficult, it is not preferable.
On the other hand, if the upper limit value of conditional expression (7) is exceeded, the focal length of the positive lens group LP included in the rear group LR becomes too long. In this case, in order to ensure a wide angle of view at the wide-angle end, it is necessary to extremely increase the negative refractive power of the first lens unit L1, and it is difficult to suppress field curvature and distortion generated in the first lens unit L1. Therefore, it is not preferable.

More preferably, the numerical ranges of conditional expressions (1) to (3) and (5) to (7) are set as follows.
−1.35 <f1 / fp <−0.30 (1a)
1.82 <Nd1p <2.45 (2a)
13 <νd1p <38 (3a)
100.0 <| fdoe / fw | <1500.0 (5a)
−4.5 <f1 / fw <−1.0 (6a)
0.70 <fp / ft <2.00 (7a)

More preferably, the numerical ranges of the conditional expressions (1a) to (3a) and (5a) to (7a) are set as follows.
−1.30 <f1 / fp <−0.40 (1b)
1.84 <Nd1p <2.40 (2b)
15 <νd1p <36 (3b)
150.0 <| fdoe / fw | <1000.0 (5b)
-4.0 <f1 / fw <-1.2 (6b)
0.8 <fp / ft <1.5 (7b)

Next, features of the lens configurations of the first to fifth embodiments of the zoom lens according to the present invention will be described.
In the lens cross-sectional views of the respective examples, I is an image plane, which corresponds to the imaging plane of the solid-state imaging device. In the following description, it is assumed that the optical elements are arranged in order from the object side to the image side unless otherwise specified.

[Example 1]
The zoom lens according to Example 1 includes a first lens unit L1 having a negative refractive power and a second lens unit L2 having a positive refractive power. The cemented lens included in the first lens unit L1 includes a diffractive optical element DOE on the cemented surface. The rear lens group LR of the zoom lens according to Example 1 includes the second lens unit L2, and the positive lens unit LP included in the rear unit LR includes the second lens unit L2.
During zooming from the wide-angle end to the telephoto end, the second lens unit L2 moves monotonically to the object side and performs zooming. The first lens unit L1 corrects image plane fluctuations accompanying zooming. The variable stop SP disposed between the first lens unit L1 and the second lens unit L2 is fixed with respect to the optical axis direction at the time of zooming.
The use of the diffractive optical element DOE on the cemented surface of the cemented lens included in the first lens unit L1 ensures the durability required for the surveillance camera. Also in the following Examples 2 to 5, the diffractive optical element DOE is provided on the cemented surface of the cemented lens.

The first lens unit L1 includes, in order from the object side, a negative lens, a negative lens, and a cemented lens of a positive lens including a diffractive optical element DOE on the cemented surface and a negative lens. By providing the diffractive optical element DOE in the first lens unit L1 passing through a position where the off-axis light beam is high, fluctuations in lateral chromatic aberration in a wide wavelength region from visible light to near infrared light are suppressed in the entire zoom range.
The second lens unit L2 includes, in order from the object side, a positive lens, a cemented lens of a negative lens and a positive lens, a negative lens, and a cemented lens of a positive lens and a negative lens. The positive lens closest to the object side of the second lens unit L2 is both aspheric. By providing the second lens unit L2 which is a main zooming group and where the axial ray passes at a high position, a lens having both aspheric surfaces is provided, thereby suppressing variations in spherical aberration and coma in the entire zoom range.

  Table 1 shows corresponding values for the conditional expressions of the zoom lens according to Example 1. In Example 1, all the conditional expressions are satisfied, and a zoom lens in which the chromatic aberration of magnification is reduced in the entire zoom range while having a compact and wide field angle is realized.

  Note that the cemented lens that does not have the diffractive optical element DOE in the zoom lens of the present invention may be provided as a separation lens having a minute air interval. In addition, the aperture diameter of the variable stop SP in the zoom lens of the present invention can be constant during zooming or can be changed. By changing the diameter of the variable stop SP, underline coma flare in the off-axis light beam can be cut, and better optical performance can be obtained. This is within the assumption of deformation and change as the lens shape in the zoom lens of the present invention, and the same applies to all the embodiments below.

[Example 2]
The zoom lens according to Example 2 includes a first lens unit L1 having a negative refractive power, a second lens unit L2 having a positive refractive power, a third lens unit L3 having a positive refractive power, and a positive refractive power. The fourth lens unit L4 includes a fifth lens unit L5 having a negative refractive power, and a sixth lens unit L6 having a positive refractive power. The cemented lens included in the first lens unit L1 includes a diffractive optical element DOE on the cemented surface. The rear lens group LR of the zoom lens according to Example 2 includes the second lens unit L2, the third lens unit L3, the fourth lens unit L4, the fifth lens unit L5, and the sixth lens unit L6. The included positive lens group LP includes a fourth lens group L4.
During zooming from the wide-angle end to the telephoto end, the second lens unit L2, the third lens unit L3, the fourth lens unit L4, and the fifth lens unit L5 move monotonically to the object side and perform zooming. The first lens unit L1 corrects image plane fluctuations accompanying zooming. The sixth lens unit L6 does not move during zooming. Further, the variable stop SP disposed between the third lens unit L3 and the fourth lens unit L4 moves in the optical axis direction together with the fourth lens unit L4 during zooming. A flare cut stop FC is provided on the most object side of the third lens unit L3.

The first lens unit L1 includes, in order from the object side, a negative lens, a negative lens, and a cemented lens of a negative lens including a diffractive optical element DOE on the cemented surface and a positive lens. By providing the diffractive optical element DOE in the first lens unit L1 passing through a position where the off-axis light beam is high, fluctuations in lateral chromatic aberration in a wide wavelength region from visible light to near infrared light are suppressed in the entire zoom range. Further, the image-side surface of the second negative lens of the first lens unit L1 is an aspherical surface, and thereby particularly corrects the curvature of field and distortion on the wide-angle side.
The second lens unit L2 includes a positive lens. The object side surface of the positive lens in the second lens unit L2 is an aspherical surface, and thereby, variations in spherical aberration, coma aberration, and field curvature in the entire zoom range are corrected favorably.
The third lens unit L3 includes, in order from the object side, a cemented lens of a positive lens and a negative lens, and a positive lens. The image side surface of the negative lens of the third lens unit L3 is an aspherical surface, thereby favorably correcting variations in spherical aberration and coma aberration over the entire zoom range.

The fourth lens unit L4 includes, in order from the object side, a negative lens, a cemented lens of a positive lens and a negative lens, and a cemented lens of a negative lens and a positive lens.
The fifth lens unit L5 includes, in order from the object side, a positive lens, a cemented lens of a negative lens and a positive lens, and a negative lens. The object-side surface of the positive lens closest to the object side in the fifth lens unit L5 is an aspherical surface, thereby favorably correcting field curvature and coma variation in the entire zoom range.
The sixth lens unit L6 includes a positive lens. By using the sixth lens unit L6 closest to the image plane as a positive lens unit, the incident angle to the image sensor at a high image height can be reduced. Thereby, it is possible to prevent a decrease in the amount of peripheral light that occurs when light rays are incident on the image sensor at an angle. For example, in order to correct the peripheral light amount drop, it is necessary to increase the gain around the screen in terms of image processing or electric circuit, but noise may occur in an environment where a sufficient light amount is not obtained. Since noise is not preferable for the monitoring camera, it is preferable for the monitoring camera to suppress the generation of noise.

  Table 1 shows corresponding values for the conditional expressions of the zoom lens according to Example 2. In Example 2, all the conditional expressions are satisfied, and a zoom lens in which the chromatic aberration of magnification is reduced in the entire zoom range while having a compact and wide field angle is realized.

[Example 3]
The zoom lens according to Example 3 includes a first lens unit L1 having a negative refractive power and a second lens unit L2 having a positive refractive power. One of the cemented lenses included in the second lens unit L2 includes a diffractive optical element DOE on the cemented surface. The rear group LR of the zoom lens according to Example 3 is configured by the second lens group L2, and the positive lens group LP included in the rear group LR is configured by the second lens group L2.
During zooming from the wide-angle end to the telephoto end, the second lens unit L2 moves monotonically to the object side and performs zooming. The first lens unit L1 corrects image plane fluctuations accompanying zooming. The variable stop SP disposed between the first lens unit L1 and the second lens unit L2 is fixed with respect to the optical axis direction at the time of zooming.

The first lens unit L1 includes, in order from the object side, a negative lens, a cemented lens of a negative lens and a positive lens, a negative lens, and a positive lens.
The second lens unit L2 includes, in order from the object side, a positive lens, a negative lens including a diffractive optical element DOE on the cemented surface and a positive lens, a negative lens, and a cemented lens of a positive lens and a negative lens. Yes.
The diffractive optical element DOE is provided in the cemented lens on the object side of the second lens unit L2 through which the off-axis light beam passes through a relatively high position on the wide angle side and the off-axis light beam passes through a relatively low position on the telephoto side. Thereby, the chromatic aberration of magnification in the entire zoom range is canceled in a wide wavelength region from visible light to near infrared light. The positive lens closest to the object side of the second lens unit L2 has two aspheric surfaces. By providing the second lens unit L2 which is the main zooming unit and has a high position through which axial rays pass, a lens having both aspheric surfaces is provided, thereby suppressing variations in spherical aberration and coma in the entire zoom range.

  Table 1 shows corresponding values for the conditional expressions of the zoom lens according to Example 3. In Example 3, all the conditional expressions are satisfied, and a zoom lens in which the chromatic aberration of magnification is reduced in the entire zoom range while having a compact and wide field angle is realized.

[Example 4]
The zoom lens according to Example 4 includes a first lens unit L1 having a negative refractive power and a second lens unit L2 having a positive refractive power. One of the cemented lenses included in the second lens unit L2 includes a diffractive optical element DOE on the cemented surface. The rear group LR of the zoom lens according to Example 4 is configured by the second lens group L2, and the positive lens group LP included in the rear group LR is configured by the second lens group L2.
During zooming from the wide-angle end to the telephoto end, the second lens unit L2 moves monotonically to the object side and performs zooming. The first lens unit L1 corrects image plane fluctuations accompanying zooming. The variable stop SP disposed between the first lens unit L1 and the second lens unit L2 is fixed with respect to the optical axis direction at the time of zooming.

The first lens unit L1 includes, in order from the object side, a negative lens, a cemented lens of a negative lens and a positive lens, and a cemented lens of a negative lens and a positive lens.
The second lens unit L2 includes, in order from the object side, a positive lens, a cemented lens of a negative lens and a positive lens, a negative lens, and a cemented lens of a positive lens and a negative lens including a diffractive optical element DOE on the cemented surface. Yes.
By providing the diffractive optical element DOE on the most image side cemented lens of the second lens unit L2 where the off-axis light beam passes through, the chromatic aberration of magnification in a wide wavelength region from visible light to near infrared light in the entire zoom range. Fluctuation is suppressed. The positive lens closest to the object side of the second lens unit L2 has two aspheric surfaces. By providing the second lens unit L2 which is the main zooming unit and has a high position through which axial rays pass, a lens having both aspheric surfaces is provided, thereby suppressing variations in spherical aberration and coma in the entire zoom range.
Table 1 shows corresponding values for the conditional expressions of the zoom lens according to Example 4. In Example 4, all the conditional expressions are satisfied, and a zoom lens in which the chromatic aberration of magnification is reduced in the entire zoom range while having a compact and wide field angle is realized.

[Example 5]
The zoom lens according to Example 5 includes a first lens unit L1 having negative refractive power and a second lens unit L2 having positive refractive power. One of the cemented lenses included in the second lens unit L2 includes a diffractive optical element DOE on the cemented surface. The rear lens group LR of the zoom lens according to Example 5 includes the second lens unit L2, and the positive lens unit LP included in the rear lens group LR includes the second lens unit L2.
During zooming from the wide-angle end to the telephoto end, the second lens unit L2 moves monotonically to the object side and performs zooming. The first lens unit L1 corrects image plane fluctuations accompanying zooming. The variable stop SP disposed between the first lens unit L1 and the second lens unit L2 is fixed with respect to the optical axis direction at the time of zooming.

The first lens unit L1 includes a negative lens, a negative lens, and a positive lens in order from the object side.
The configuration of the second lens unit L2 is the same as that of the fourth embodiment. Variation in chromatic aberration of magnification in a wide wavelength range from visible light to near-infrared light over the entire zoom range by providing a diffractive optical element DOE on the most image side cemented lens of the second lens unit L2 passing through a position where off-axis rays pass through a high position. Is suppressed.

  Table 1 shows corresponding values for the conditional expressions of the zoom lens according to Example 5. In Example 5, all the conditional expressions are satisfied, and a zoom lens in which the chromatic aberration of magnification is reduced in the entire zoom range while having a compact and wide field angle is realized.

Next, an embodiment of a digital video camera using the zoom lens of the present invention as an imaging optical system will be described with reference to FIG.
In FIG. 11, reference numeral 10 denotes a camera body, and 11 denotes an image pickup optical system constituted by any of the zoom lenses according to the first to fifth embodiments. Reference numeral 12 denotes a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor that receives a subject image formed by the imaging optical system 11 and is built in the camera body.

An embodiment of a surveillance camera using the zoom lens of the present invention as an imaging optical system will be described with reference to FIG.
In FIG. 12, reference numeral 20 denotes a camera body, and 21 denotes an imaging optical system constituted by any of the zoom lenses according to the first to fifth embodiments. Reference numeral 22 denotes a solid-state image pickup device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor that receives a subject image formed by the image pickup optical system 21 and is built in the camera body.

Thus, by applying the zoom lens of the present invention to an imaging apparatus such as a digital video camera or a surveillance camera, an imaging apparatus having a small size and high optical performance can be realized.
The zoom lens of each embodiment can also be used as a projection optical system for a projection device (projector).

  The image pickup apparatus of the present invention may include a circuit (correction unit) that electrically corrects at least one of distortion and lateral chromatic aberration in addition to the zoom lens of each of the above embodiments. If the zoom lens has such a configuration that can tolerate distortion and the like, the number of lenses in the entire zoom lens can be reduced, and the size can be easily reduced. Further, by electrically correcting the chromatic aberration of magnification, it becomes easier to reduce the color blur of the captured image and improve the resolution.

  An imaging system (monitoring camera system) including the zoom lens of each embodiment and a control unit that controls the zoom lens may be configured. In this case, the control unit may control the zoom lens so that each lens group moves as described above during zooming. At this time, the control unit does not need to be configured integrally with the zoom lens, and the control unit may be configured separately from the zoom lens. For example, a configuration is adopted in which a control unit (control device) disposed far from a drive unit that drives each lens of the zoom lens includes a transmission unit that sends a control signal (command) for controlling the zoom lens. May be. According to such a control unit, the zoom lens can be remotely operated.

  In addition, an operation unit such as a controller or a button for remotely operating the zoom lens may be provided in the control unit, so that the zoom lens may be controlled in accordance with an input to the user operation unit. For example, an enlargement button and a reduction button are provided as an operation unit, and the zoom lens magnification is increased when the user presses the enlargement button, and the zoom lens magnification is reduced when the user presses the reduction button. What is necessary is just to comprise so that a signal may be sent to the drive part.

  In addition, the imaging system may include a display unit such as a liquid crystal panel that displays information (movement state) regarding zoom of the zoom lens. The information regarding the zoom of the zoom lens includes, for example, zoom magnification (zoom state) and movement amount (movement state) of each lens group. In this case, the user can remotely operate the zoom lens via the operation unit while viewing information on the zoom of the zoom lens shown on the display unit. At this time, the display unit and the operation unit may be integrated by adopting, for example, a touch panel.

  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, numerical examples 1 to 5 corresponding to the first to fifth embodiments of the present invention will be described. In each numerical example, i indicates the order of the surfaces from the object side, ri is the radius of curvature of the i-th surface from the object side, and di is the i-th surface and the (i + 1) -th surface from the object side. The intervals ndi and νdi are the refractive index and Abbe number of the optical member between the i-th surface and the (i + 1) -th surface, respectively.
The focal length, F number, and half angle of view represent values when focusing on an object at infinity.

Further, the aspherical shape is expressed by the following equation, where x is the coordinate in the optical axis direction, y is the coordinate in the direction perpendicular to the optical axis, R is the reference radius of curvature, K is the conic constant, and An is the nth-order aspherical coefficient. It is represented by (E).
x = (y ² / r) / {1+ (1−K × y ² / r ² ) ^0.5 } + A4 × y ⁴ + A6 × y ⁶ + A8 × y ⁸ + A10 × y ¹⁰ +... E)
“E−x” means “× 10 ^−x ”, and a lens surface having an aspherical surface is marked with * on the right side of the surface number in each table.

The phase φ of the diffractive surface (diffractive optical element) labeled (Diffraction) beside the surface number is m is the diffraction order of the diffracted light, λ0 is the reference wavelength, and Cj (j = 1, 2, 3,...). When the phase coefficient is of each order, it is expressed by the following formula (F).
φ (h) = (2π × m / λ0) (C2h ² + C4h ⁴ + C6h ⁶ + C8h ⁸ +...) (F)

In addition, the focal length fdoe of the diffractive optical element DOE at the reference wavelength λ0 is expressed by the following equation (G).
fdoe = −1 / (2 × C2) (G)
Furthermore, the focal length fdoe (λ) of the diffractive optical element DOE at an arbitrary wavelength λ is expressed by the following equation (H).
fdoe = −1 / (2 × C2) (λ0 / λ) (H)

Table 1 below shows correspondence between Numerical Examples 1 to 5 and the above-described conditional expressions.

Numerical example 1
Unit mm

Surface data surface number rd nd νd
1 61.561 1.30 2.00 100 29.1
2 14.374 6.33
3 -97.833 1.10 1.63854 55.4
4 24.202 3.92
5 30.409 3.40 1.85478 24.8
6 (Diffraction) -148.060 1.00 1.60311 60.6
7 112.055 (variable)
8 (Aperture) ∞ (Variable)
9 * 12.266 3.23 1.49710 81.6
10 * -76.377 0.12
11 14.025 0.80 1.54814 45.8
12 7.145 6.97 1.49700 81.5
13 -19.403 0.15
14 29.165 0.70 1.64769 33.8
15 7.433 0.89
16 15.407 5.73 1.49700 81.5
17 -5.558 0.70 1.71999 50.2
18 -6036.471 (variable)
19 ∞ 1.72 1.51633 64.1
20 ∞ 2.07
Image plane ∞

Aspheric data 6th surface (diffractive surface)
C 2 = 1.23632e-004 C 4 = 1.18586e-006 C 6 = -1.17682e-008 C 8 = 1.27968e-010
C10 = -6.55566e-013

9th page
K = -4.96140e-001 A 4 = -4.87543e-006 A 6 = 5.86472e-007 A 8 = -1.57891e-009

10th page
K = 0.00000e + 000 A 4 = 1.12042e-004 A 6 = 7.24976e-007

Various data Zoom ratio 2.90
Wide angle Medium telephoto focal length 5.52 9.71 15.99
F number 1.65 2.14 2.95
Half angle of view 58.2 31.6 19.3
Image height 5.50 5.50 5.50
Total lens length 78.05 60.86 55.31
BF 2.07 2.07 2.07

d 7 25.20 8.02 2.47
d 8 10.02 6.61 1.50
d18 2.70 6.11 11.22

Zoom lens group data group Start surface Focal length
1 1 -17.99
2 9 14.66

Numerical example 2
Unit mm

Surface data surface number rd nd νd
1 48.171 2.80 1.80 400 46.5
2 31.564 5.00
3 42.373 1.90 1.77250 49.6
4 * 16.243 15.65
5 -277.043 1.65 1.80610 33.3
6 (Diffraction) 29.656 6.02 2.00272 19.3
7 86.925 (variable)
8 * 45.686 3.56 1.77250 49.6
9 374.936 (variable)
10 ∞ 0.99
11 31.739 6.53 1.49700 81.5
12 -31.258 1.10 1.91650 31.6
13 * -80.738 0.08
14 67.802 5.27 1.49700 81.5
15 -35.941 (variable)
16 (Aperture) ∞ 2.02
17 -44.661 1.00 1.72825 28.5
18 40.664 0.28
19 42.537 6.78 1.49700 81.5
20 -16.260 0.90 1.58144 40.8
21 431.305 0.09
22 90.286 0.80 1.54814 45.8
23 21.907 5.12 1.84666 23.8
24 -34.443 (variable)
25 * -43.899 1.49 2.00100 29.1
26 -26.109 0.13
27 -35.204 1.00 1.89190 37.1
28 64.052 5.82 1.43875 94.7
29 -15.634 0.75
30 -22.094 1.10 1.68948 31.0
31 43.460 (variable)
32 50.772 4.53 1.49700 81.5
33 230.033 14.56
Image plane ∞

Aspheric data 4th surface
K = -4.36825e-001 A 4 = -1.01084e-006 A 6 = -6.35716e-010 A 8 = 8.34947e-013 A10 = -3.77602e-015

6th surface (diffractive surface)
C 2 = 7.29473e-005 C 4 = 4.16309e-007 C 6 = -1.07641e-009 C 8 = 9.86093e-013

8th page
K = 0.00000e + 000 A 4 = -2.24813e-006 A 6 = -3.78737e-010 A 8 = 7.06398e-012 A10 = -1.37684e-014 A12 = 2.70566e-017

Side 13
K = 0.00000e + 000 A 4 = 3.23317e-006 A 6 = 2.22670e-010 A 8 = 6.02592e-011 A10 = -2.97346e-013 A12 = 6.05622e-016

25th page
K = 0.00000e + 000 A 4 = -4.32513e-005 A 6 = -7.82363e-008 A 8 = 4.36862e-010 A10 = -7.08198e-012 A12 = 3.79207e-014

Various data Zoom ratio 2.00
Wide angle Medium telephoto focal length 15.79 19.00 31.58
F number 2.85 2.88 2.88
Half angle of view 53.9 48.7 34.4
Image height 21.64 21.64 21.64
Total lens length 135.28 132.50 129.71
BF 14.56 14.56 14.56

d 7 16.96 11.84 4.52
d 9 16.77 14.46 3.86
d15 0.99 1.98 5.29
d24 1.63 1.54 1.03
d31 2.00 5.75 18.09

Zoom lens group data group Start surface Focal length
1 1 -19.50
2 8 67.03
3 10 30.90
4 16 46.34
5 25 -26.93
6 32 130.00

Numerical Example 3
Unit mm

Surface data surface number rd nd νd
1 60.284 1.30 1.83481 42.7
2 11.557 5.17
3 281.669 1.10 1.49700 81.5
4 11.876 2.83 1.77250 49.6
5 19.281 4.31
6 -25.155 1.00 1.49700 81.5
7 292.318 0.50
8 50.676 1.79 2.00100 29.1
9 -142.532 (variable)
10 (Aperture) ∞ (Variable)
11 * 12.764 4.24 1.49710 81.6
12 * -60.559 0.92
13 19.704 0.80 1.65844 50.9
14 (Diffraction) 9.217 6.13 1.49700 81.5
15 -19.798 1.55
16 44.951 0.80 1.95375 32.3
17 9.828 1.78
18 14.453 5.38 1.69895 30.1
19 -9.788 0.80 1.85478 24.8
20 1859.061 (variable)
21 ∞ 1.72 1.51633 64.1
22 ∞ 2.07
Image plane ∞

Aspheric data 11th surface
K = -1.04161e-002 A 4 = -4.84596e-005 A 6 = 3.93621e-007 A 8 = -3.31170e-010

12th page
K = 0.00000e + 000 A 4 = 9.48009e-005 A 6 = 6.07006e-007

14th surface (diffractive surface)
C 2 = -1.44758e-004 C 4 = -2.46762e-006 C 6 = 2.32195e-008 C 8 = 7.46455e-010
C10 = -8.27267e-013

Various data Zoom ratio 3.39
Wide angle Medium telephoto focal length 5.71 11.18 19.38
F number 1.85 2.42 4.14
Half angle of view 58.0 28.1 16.2
Image height 5.50 5.50 5.50
Total lens length 85.14 69.15 68.69
BF 2.07 2.07 2.07

d 9 18.44 2.45 1.99
d10 17.13 10.87 1.49
d20 5.37 11.63 21.01

Zoom lens group data group Start surface Focal length
1 1 -15.07
2 11 17.25

Numerical Example 4
Unit mm

Surface data surface number rd nd νd
1 63.162 1.30 1.83481 42.7
2 11.034 4.89
3 186.446 1.10 1.49700 81.5
4 12.054 2.78 1.77250 49.6
5 21.692 4.53
6 -19.768 1.00 1.49700 81.5
7 33.821 2.17 1.91082 35.3
8 -68.690 (variable)
9 (Aperture) ∞ (Variable)
10 * 13.186 4.42 1.49710 81.6
11 * -56.136 0.53
12 18.753 0.80 1.63854 55.4
13 8.856 6.45 1.49700 81.5
14 -19.387 0.12
15 33.538 0.80 1.95375 32.3
16 11.489 3.18
17 21.851 4.09 1.69895 30.1
18 (Diffraction) -10.413 0.80 1.85478 24.8
19 -189.818 (variable)
20 ∞ 1.72 1.51633 64.1
21 ∞ 2.07
Image plane ∞

Aspheric data 10th surface
K = 1.15976e-001 A 4 = -4.53000e-005 A 6 = 4.50170e-007 A 8 = -7.17479e-010

11th page
K = 0.00000e + 000 A 4 = 1.08787e-004 A 6 = 7.46893e-007

18th surface (diffractive surface)
C 2 = -2.90922e-004 C 4 = -4.09942e-006 C 6 = -1.27544e-010 C 8 = 3.56717e-009
C10 = -5.47670e-011

Various data Zoom ratio 2.89
Wide angle Medium telephoto focal length 5.78 10.15 16.70
F number 1.65 2.09 3.30
Half angle of view 59.2 31.4 18.8
Image height 5.50 5.50 5.50
Total lens length 80.12 68.00 67.06
BF 2.07 2.07 2.07

d 8 15.06 2.94 2.00
d 9 15.11 9.66 1.50
d19 7.21 12.65 20.82

Zoom lens group data group Start surface Focal length
1 1 -13.75
2 10 17.12

Numerical Example 5
Unit mm

Surface data surface number rd nd νd
1 249.363 1.30 1.83481 42.7
2 14.749 6.42
3 -29.273 1.10 1.49700 81.5
4 22.426 1.89
5 30.798 2.62 2.00 100 29.1
6 1096.749 (variable)
7 (Aperture) ∞ (Variable)
8 * 15.483 2.95 1.49710 81.6
9 * -1217.114 0.72
10 14.015 0.80 1.70154 41.2
11 9.156 6.11 1.49700 81.5
12 -19.628 1.48
13 19.487 0.80 1.90366 31.3
14 8.723 3.58
15 18.205 2.49 1.74950 35.3
16 (Diffraction) -91.908 0.80 1.85478 24.8
17 51.251 (variable)
18 ∞ 1.72 1.51633 64.1
19 ∞ 2.07
Image plane ∞

Aspheric data 8th surface
K = 4.93464e-001 A 4 = -5.37673e-006 A 6 = 8.67748e-007 A 8 = -1.49643e-009

9th page
K = 0.00000e + 000 A 4 = 1.41698e-004 A 6 = 1.40625e-006

16th surface (diffractive surface)
A 2 = -4.12878e-004 A 4 = 2.23481e-006 A 6 = -1.92381e-007 A 8 = 1.27816e-008
A10 = -2.67556e-010

Various data Zoom ratio 2.89
Wide angle Medium Telephoto focal length 6.00 10.54 17.35
F number 1.65 2.06 2.87
Half angle of view 60.0 30.2 18.1
Image height 5.50 5.50 5.50
Total lens length 80.16 62.76 58.03
BF 2.07 2.07 2.07

d 6 24.90 7.50 2.77
d 7 12.47 8.08 1.50
d17 5.95 10.34 16.92

Zoom lens group data group Start surface Focal length
1 1 -17.73
2 8 17.14

DOE diffractive optical element (diffractive optical part)
L1 First lens group LP Lens group LR having positive refractive power Rear group SP Aperture stop

Claims (22)

A zoom lens including a first lens unit having a negative refractive power and a rear group including a lens unit LP having a positive refractive power, which are arranged in order from the object side to the image side, and in which the distance between adjacent lens units changes during zooming. A lens,
The at least one lens group includes a cemented lens in which a diffractive optical part is provided on the cemented surface,
An aperture stop is disposed on the object side of the lens group LP,
The lens group LP has two positive lenses and moves to the object side during zooming from the wide-angle end to the telephoto end.
When the focal length of the first lens group is f1, and the focal length of the lens group LP is fp,
−1.50 <f1 / fp <−0.20
A zoom lens satisfying the following conditional expression: The first lens group has at least one positive lens;
When the refractive index and Abbe number regarding the d-line of any material of the at least one positive lens are Nd1p and νd1p, respectively.
1.80 <Nd1p <2.50
10 <νd1p <40
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. When the Abbe number of either of the two positive lenses included in the lens group LP is νdpp,
80 <νdpp
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. When the focal length of the entire system at the wide-angle end is fw, and the focal length of the diffractive optical unit is fdoe,
50.0 <| fdoe / fw | <2000.0
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. When the focal length of the entire system at the wide angle end is fw,
−5.0 <f1 / fw <−0.5
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. When the focal length of the entire system at the telephoto end is ft,
0.5 <fp / ft <3.0
The zoom lens according to claim 1, wherein the following conditional expression is satisfied.   The zoom lens according to claim 1, wherein the lens group LP monotonously moves toward the object side during zooming from the wide-angle end to the telephoto end.   The zoom lens according to claim 1, wherein the rear group includes a second lens group having a positive refractive power.   The zoom lens according to claim 8, wherein the first lens group includes the cemented lens.   The zoom lens according to claim 8, wherein the second lens group includes the cemented lens.   The rear group includes a second lens group having a positive refractive power, a third lens group having a positive refractive power, a fourth lens group having a positive refractive power, a fifth lens group having a negative refractive power, and a positive refractive power. The zoom lens according to claim 1, comprising a sixth lens group.   The zoom lens according to claim 11, wherein the fourth lens group is the lens group LP.   The zoom lens according to claim 11, wherein the first lens group includes the cemented lens.   The zoom lens according to claim 11, wherein the aperture stop is disposed between the third lens group and the fourth lens group.   During zooming from the wide-angle end to the telephoto end, the first lens group moves, and the second lens group, the third lens group, the fourth lens group, and the fifth lens group move monotonously toward the object side. The zoom lens according to claim 11, wherein the sixth lens group is stationary. −1.35 <f1 / fp <−0.30
The zoom lens according to claim 1, wherein the following conditional expression is satisfied.   An image pickup apparatus comprising: the zoom lens according to claim 1; and an image pickup element that receives an image formed by the zoom lens.   The imaging apparatus according to claim 17, further comprising a correction unit that electrically corrects an aberration of the zoom lens. A zoom lens according to any one of claims 1 to 16,
An imaging system comprising: a control unit that controls the zoom lens during zooming.   The imaging system according to claim 19, wherein the control unit is configured separately from the zoom lens, and includes a transmission unit that transmits a control signal for controlling the zoom lens.   21. The imaging system according to claim 19, wherein the control unit is configured separately from the zoom lens and includes an operation unit for operating the zoom lens.   The imaging system according to any one of claims 19 to 21, further comprising a display unit configured to display information regarding zoom of the zoom lens.

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