JP6545002B2 - Zoom lens and imaging device having the same - Google Patents

Description

  The present invention relates to a zoom lens, and is particularly suitable as an imaging optical system used for an imaging device such as a surveillance camera, a digital camera, a video camera, and a broadcast camera.

  An imaging optical system used for an imaging apparatus using a solid-state imaging device is a zoom lens with a wide angle of view that has high optical performance that can cope with the high-resolution of the solid-state imaging device and easy to wide area imaging. It is requested to be. In particular, from the viewpoint of high image quality, it is desirable to have high optical performance that can sufficiently cope with an image sensor with megapixels, full HD (High Definition) image quality or more pixels from SD (Standard Definition) image quality. It is done.

  In recent years, with the rapid expansion of the surveillance camera market, zoom lenses used for surveillance cameras are required to have a wide angle of view and small Fno. A common surveillance camera uses visible light for daytime imaging and uses near infrared light for nighttime imaging.

  For example, in surveillance cameras, in many cases, shooting at night is facilitated by using near-infrared light of a wavelength of 800 nm to a wavelength of 1000 nm under low illumination. For this reason, the zoom lens used in the surveillance camera is required to correct chromatic aberration well in a wide wavelength range from visible light (about 400 nm to about 700 nm) to the near infrared region, and to reduce focus deviation etc. ing.

  Furthermore, in order to facilitate installation anywhere and indoors, it is also required that the entire system be particularly compact. As a zoom lens satisfying these demands, a negative lead type zoom lens in which a lens unit of negative refractive power is disposed closest to the object side is known. As a negative lead type zoom lens, it is composed of first to third lens units with negative, positive and positive refractive power in order from the object side to the image side, and the distance between adjacent lens groups changes during zooming 3 Group zoom lenses are known (Patent Documents 1 and 2).

JP 2012-22080 A JP 2011-257625 A

  In the negative lead type three-unit zoom lens described above, it is important to appropriately set the lens configuration of each lens group in order to obtain high optical performance over the entire zoom region while the entire system is compact and has a wide angle of view. It will be In particular, in a zoom lens used for a surveillance camera, it is important to set a lens configuration so that chromatic aberration is well corrected and defocusing is reduced over a wide wavelength range from the visible range to the near infrared range.

  For example, in order to correct chromatic aberration well in a wide wavelength range and to reduce the focus shift, it is important to appropriately set the lens configuration of the second lens unit and the material etc. of the lens used for the second lens unit. It will be If these configurations are inadequate, it becomes very difficult to obtain a zoom lens with high optical performance over a wide wavelength range with a wide angle of view while achieving downsizing of the entire system.

  An object of the present invention is to provide a zoom lens in which the entire lens system is compact, a wide angle of view, and high optical performance easily in the entire zoom range, and an image pickup apparatus having the same.

The zoom lens according to the present invention comprises a first lens group of negative refractive power, a second lens group of positive refractive power, and a third lens group of positive refractive power, which are disposed in order from the object side to the image side. A zoom lens in which all lens groups move so that the distance between adjacent lens groups changes during zooming ,
The second lens group includes a positive lens A,
The refractive index of the material for light of wavelength 486.13 nm is nF, the refractive index of the material for light of wavelength 587.6 nm is nd, the refractive index of the material for light of wavelength 656.27 nm is nC, the material for light of wavelength 1013.98 nm Of the material, and the Abbe number .nu.d of the material and the partial dispersion ratio .theta.Ct, respectively: .nu.d = (nd-1) / (nF-nC)
θCt = (nC−nt) / (nF−nC)
And,
Assuming that the Abbe number of the material of the positive lens A is ddA, the partial dispersion ratio is θCtA , the focal length of the first lens group is f1, and the focal length of the second lens group is f2.
85.0 <νdA
−0.25 <θCtA− (0.0047 × νdA + 0.546) <− 0.10
−0.85 <f1 / f2 <−0.35
It is characterized by satisfying the following conditional expression.

  According to the present invention, it is possible to obtain a zoom lens in which the entire lens system is compact, a wide angle of view, and high optical performance easily in the entire zoom range, and an image pickup apparatus having the same.

Diagram of lens cross section and movement locus at the wide-angle end in Example 1 (A), (B), (C) Aberrations at the wide-angle end, at the intermediate zoom position, and at the telephoto end according to Example 1. Diagram of lens cross section and movement locus at the wide-angle end in Example 2 (A), (B), (C) Aberrations at the wide-angle end, at the intermediate zoom position, and at the telephoto end according to Example 2. Diagram of lens cross section and movement locus at the wide-angle end in Example 3 (A), (B), (C) Aberrations at the wide-angle end, at the intermediate zoom position, and at the telephoto end according to Example 3. Diagram of lens cross section and movement locus at the wide-angle end in Example 4 (A), (B), (C) Aberrations at the wide-angle end, at the intermediate zoom position, and at the telephoto end according to Example 4. Optical path diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end in the first embodiment The principal part schematic diagram of the surveillance camera (imaging device) of the present invention

  Hereinafter, the zoom lens of the present invention and an imaging device having the same will be described based on the drawings. The zoom lens according to the present invention comprises, in order from the object side to the image side, a first lens group of negative refractive power, a second lens group of positive refractive power, and a third lens group of positive refractive power. Each lens group moves so that the distance between adjacent lens groups changes during zooming.

  FIG. 1 is a cross-sectional view of a zoom lens at a wide angle end (short focal length end) according to a first exemplary embodiment of the present invention. FIGS. 2A, 2B, and 2C are aberration diagrams at the wide-angle end, the middle zoom position, and the telephoto end (long focal length end) of the zoom lens according to the first embodiment of the present invention.

  The first embodiment is a zoom lens having a zoom ratio of 2.30 and an f-number of 1.24 to 1.81. FIG. 3 is a lens sectional view of a zoom lens at the wide-angle end according to a second embodiment of the present invention. FIGS. 4A, 4B, and 4C are aberration diagrams at the wide-angle end, the middle zoom position, and the telephoto end of the zoom lens according to Embodiment 2 of the present invention. The second embodiment is a zoom lens having a zoom ratio of 2.31 and an f-number of 1.24 to 1.84.

  FIG. 5 is a lens sectional view of a zoom lens at the wide-angle end according to a third embodiment of the present invention. FIGS. 6A, 6B, and 6C are aberration diagrams at the wide-angle end, the middle zoom position, and the telephoto end of the zoom lens according to Embodiment 3 of the present invention. The third embodiment is a zoom lens having a zoom ratio of 2.41 and an f-number of 1.24 to 1.90.

  FIG. 7 is a lens sectional view of a zoom lens at the wide-angle end according to a fourth embodiment of the present invention. FIGS. 8A, 8B, and 8C are aberration diagrams at the wide-angle end, the middle zoom position, and the telephoto end of the zoom lens according to the fourth embodiment of the present invention. The fourth embodiment is a zoom lens having a zoom ratio of 2.32 and an f-number of 1.23 to 1.75.

  FIGS. 9A, 9B, and 9C are optical path diagrams at the wide-angle end, the middle zoom position, and the telephoto end of the zoom lens of Embodiment 1. FIGS. FIG. 10 is a schematic view of the essential portions of a surveillance camera (image pickup apparatus) having a zoom lens according to the present invention.

  The zoom lens of each embodiment is an imaging optical system used for an imaging device, and in the lens 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 an optical apparatus such as a projector. In this case, the left side is the screen and the right side is the projection image. In the lens sectional view, LO is a zoom lens. L1 is a first lens group of negative refractive power (optical power = reciprocal of focal length), L2 is a second lens group of positive refractive power, and L3 is a third lens group of positive refractive power.

  SP is an F-number determining member (hereinafter also referred to as "aperture stop") that acts as an aperture stop that determines (limits) an open F-number (Fno) luminous flux. G is an optical block corresponding to an optical filter, a face plate, a quartz low pass filter, an infrared cut filter, and the like. IP is an image plane, and when used as an imaging optical system of a video camera or a digital still camera, an imaging surface of a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor is placed.

  Arrows indicate movement loci of the respective lens units during zooming from the wide-angle end to the telephoto end. An arrow 3a related to the third lens unit L3 indicates a movement locus during zooming from the wide-angle end to the telephoto end when focusing at infinity. An arrow 3 b indicates a movement locus during zooming from the wide-angle end to the telephoto end when focusing at a short distance. An arrow 3c relating to the third lens unit L3 indicates the moving direction during focusing from infinity to near distance.

In spherical aberration, d-line (wavelength 587.6 nm), C-line (wavelength 656.3 nm), F-line (wavelength 486.13 nm), wavelength 850 nm and t-line (wavelength 1013.98 nm) are displayed. In astigmatism, ΔM represents a meridional image plane, and ΔS represents a sagittal image plane. In distortion, d-line is displayed. C-line for d-line in lateral chromatic aberration,
Aberrations of F-ray, wavelength 850 nm, and t-ray are displayed. Fno is an F number, and ω is a half angle of view (degree).

  The present invention is a compact zoom lens having a wide angle of view and a small zoom lens that has high optical performance over the entire zoom range although the entire system is compact, particularly in a wide wavelength range from visible light to near infrared light. It is. The zoom lens according to the present invention includes, in order from the object side to the image side, a first lens unit L1 of negative refractive power, a second lens unit L2 of positive refractive power, and a third lens unit L3 of positive refractive power. Zoom lens having a three-unit configuration. During zooming from the wide-angle end to the telephoto end, the lens units move in the directions of the arrows along different trajectories.

  The zoom type of the zoom lens according to the present invention is a three-group configuration of negative lead (negative lens group leading). The zooming is performed by changing the distance between the lens units while making the first lens unit L1 have a negative refractive power, and the configuration is suitable for wide angle of view. The second lens unit L2 and the third lens unit L3 move along different trajectories to perform magnification change, and the image plane fluctuation caused thereby is corrected by moving the first lens unit L1 closest to the object side. Focusing is performed by the third lens unit L3.

In each example, the refractive index of the material for light of wavelength 486.13 nm is nF, the refractive index of the material for light of wavelength 587.6 nm is nd, the refractive index of the material for light of wavelength 656.27 nm is nC, and wavelength 1013. The refractive index of the material for light of 98 nm is nt. The Abbe number dd of the material and the partial dispersion ratio θCt are respectively
d d = (nd-1) / (nF-nC)
θCt = (nC−nt) / (nF−nC)
I assume.

At this time, the second lens unit L2 includes a positive lens, the Abbe number of the material of the positive lens included in the second lens unit L2 is ddA, and the partial dispersion ratio is θCtA. At this time, the second lens unit L2
85.0 <νdA (1)
−0.25 <θCtA− (0.0047 × νdA + 0.546) <− 0.10
... (2)
The positive lens A satisfies the following conditional expression.

Then, when the focal length of the first lens group L1 is f1 and the focal length of the second lens group L2 is f2,
−0.85 <f1 / f2 <−0.35 (3)
Satisfy the following conditional expression. In addition, the value of each parameter is a value in d line (wavelength 587.6 nm) unless otherwise noted.

  Next, technical meanings of the above-mentioned conditional expressions will be described. Conditional expressions (1) and (2) are for reducing defocusing in a wide wavelength range from visible light to near infrared light over the entire zoom range, and obtaining high optical performance. In order to correct the defocus in a wide wavelength range, it is preferable to reduce the axial chromatic aberration by using a material having a large Abbe number, that is, a material having a small dispersion, as the material of the positive lens having high marginal rays of axial light.

  In the zoom lens of the three-group configuration of each embodiment, as shown in FIGS. 9A, 9B, and 9C, the marginal rays of axial light flux in the entire zoom range are incident heights of rays in the second lens unit L2. (Hw) goes high. Conditional expressions (1) and (2) define the optical characteristics of the material of at least one positive lens A included in the second lens unit L2.

  The Abbe number dd is defined as described above using the refractive indices nd, nF and nC of d-line, F-line and C-line in the visible light range. Therefore, by selecting the lens material based on the Abbe number 数 d, the correction of the chromatic aberration in the visible light range becomes easy. However, the Abbe number 規定 d does not define the characteristics of the near infrared region, so even if the lens material is selected based on only the Abbe number dd, chromatic aberration is not necessarily required for the near infrared region having a wavelength of 900 nm or more. It can not be corrected well.

  Therefore, by selecting the material of the lens focusing on the partial dispersion ratio θCt in addition to the Abbe number dd, axial chromatic aberration is controlled in the wavelength range of both the visible light region and the near infrared region, Focus shift is reduced in the wavelength range. Further, by selecting such a material, correction of lateral chromatic aberration in the near infrared region is also favorably performed.

  The conditional expression (1) and the conditional expression (2) define the characteristics of the material of at least one positive lens A included in the second lens unit L2. If a material having a small Abbe number (ie, a large dispersion) exceeding the lower limit of conditional expression (1) is applied, it becomes difficult to satisfactorily correct axial chromatic aberration in the visible light range.

A material having a relationship between the partial dispersion ratio θCt and the Abbe number dd beyond the lower limit of the conditional expression (2) can easily suppress axial chromatic aberration in the near infrared region to a small degree, but at present, such characteristics It is difficult to produce an optical material that achieves Conversely, the partial dispersion exceeds the upper limit of conditional expression (2)
If the ratio θCtA becomes too large, the difference in refractive index depending on the wavelength in the near infrared region becomes too large, and it becomes difficult to correct axial chromatic aberration.

  Conditional expression (3) shows that the focal length of the second lens unit L2, which is one of the lens units for zooming, and the first lens which requires relatively strong negative refractive power for widening the angle of view. The relationship of the focal length of the group L1 is set.

  In addition, in order to facilitate widening of the first lens unit L1, the lens configuration has at least two negative lenses, and the second lens unit L2 is easily given a magnification changing action as a lens unit having positive refractive power. In order to do this, the lens configuration has two or more positive lenses. Furthermore, the first lens unit L1 and the second lens unit L2 have a lens configuration that has both a positive lens and a negative lens in order to facilitate balance of aberration correction.

  If the negative refractive power of the first lens unit L1 becomes strong (if the absolute value of negative refractive power becomes large) beyond the upper limit value of the conditional expression (3), it is difficult to correct curvature of field and chromatic aberration in a well-balanced manner become. In addition, exceeding the upper limit of conditional expression (3) may also tend to reduce the positive refractive power of the second lens unit L2. As a result, the positive refractive power of the second lens unit L2 becomes too small, the amount of movement of the second lens unit L2 for zooming increases, the total lens length increases, and the front lens effective diameter increases.

  If the negative refractive power of the first lens unit L1 becomes weak (if the absolute value of the negative refractive power decreases) beyond the lower limit value of the conditional expression (3), then the first lens unit is used as a correction of the image plane fluctuation during zooming The amount of movement of L1 increases, the overall lens length increases, and the front lens effective diameter increases. In addition, exceeding the lower limit value of the conditional expression (3) may also tend to increase the positive refractive power of the second lens unit L2. As a result, various aberrations such as spherical aberration increase.

More preferably, the numerical ranges of the conditional expressions (1) to (3) are set as follows.
90.0 <νdA (1a)
−0.22 <θCtA− (0.0047 × νdA + 0.546) <− 0.08
... (2a)
−0.78 <f1 / f2 <−0.42 (3a)

  The zoom lens which is the object of the present invention is realized by satisfying the above configuration. Furthermore, in each embodiment, preferably, one or more of the following conditions should be satisfied.

The focal length of the third lens unit L3 is f3. The first lens unit L1 includes two or more negative lenses, and the thickness of the first lens unit L1 on the optical axis is 1GL. The second lens unit L2 includes two or more positive lenses, and the thickness of the second lens unit L2 on the optical axis is 2GL. During focusing, the third lens unit L3 moves, and the focal length of the entire system at the wide-angle end is fw. The second lens unit L2 has two positive lenses disposed continuously from the object side, and among these, the positive lens disposed on the object side has an aspheric lens surface, and two positive lenses. The average value of Abbe number of the material of is set as dd2 _pAVE .

  The total lens length at the wide angle end is taken as OALw. The amount of movement of the second lens unit L2 in zooming from the wide-angle end to the telephoto end is M2. The focal length of the entire system at the telephoto end is ft. During zooming from the wide-angle end to the telephoto end, the third lens unit L3 moves to the object side, and the moving amount of the third lens unit L3 in zooming from the wide-angle end to the telephoto end is M3. Here, the sign of the movement amount is moved by zooming from the wide-angle end to the telephoto end, so that the position is closer to the object side at the telephoto end than at the wide-angle end, and is positive when it is positioned to the image side. .

At this time, it is preferable to satisfy one or more of the following conditional expressions.
0.75 <f2 / f3 <1.50 (4)
1.3 <1GL / | f1 | <2.4 (5)
0.45 <2GL / f2 <0.95 (6)
3.2 <f3 / fw <7.0 (7)
70 <νd2p _AVE (8)
0.034 <fw / OALw <0.060 (9)
0.6 <| M2 | / √ (fw × ft) <1.3 (10)
0.8 <| M3 | / √ (fw × ft) <1.6 (11)

  Next, technical meanings of the above-mentioned conditional expressions will be described. In each embodiment, the second lens unit L2 and the third lens unit L3 are independently moved during zooming in order to easily obtain high optical performance over the entire zoom range. Condition (4) appropriately sets the relationship between the two refractive powers for that purpose.

  If the positive refractive power of the second lens unit L2 becomes too strong beyond the lower limit value of the conditional expression (4), various aberrations such as spherical aberration and coma aberration in particular increase, and these aberrations It becomes difficult to correct in group L3. If the positive refractive power of the third lens unit L3 becomes too strong beyond the upper limit value of the conditional expression (4), it becomes difficult to perform well-balanced correction of the second lens unit L2 and various aberrations.

  Condition (5) relates to the thickness on the optical axis when the first lens unit L1 includes two or more negative lenses. This other conditional expression (5) is a first lens group for downsizing of the whole system with respect to the refractive power of the first lens group L1 which requires relatively strong negative refractive power for wide angle of view. It relates to the thickness ratio on the optical axis of L1. If the negative refractive power of the first lens unit L1 becomes too strong beyond the upper limit value of the conditional expression (5), various aberrations such as astigmatism and field curvature increase. If the negative refractive power of the first lens unit L1 becomes too weak beyond the lower limit value of the conditional expression (5), widening of the angle of view becomes difficult, which is not preferable.

  The conditional expression (6) relates to the thickness on the optical axis at the time when the second lens unit L2 includes two or more positive lenses. In particular, conditional expression (6) applies to the second lens unit L2 for miniaturizing the entire system with respect to the focal length of the second lens unit L2 which requires a relatively strong positive refractive power for zooming. It relates to the thickness ratio on the optical axis. If the positive refractive power of the second lens unit L2 becomes too strong beyond the upper limit value of the conditional expression (6), aberrations such as spherical aberration increase. If the positive refractive power of the second lens unit L2 becomes too weak beyond the lower limit value of the conditional expression (6), the amount of movement of the second lens unit L2 increases during zooming, and the total lens length increases. Is difficult to miniaturize.

  Conditional expression (7) appropriately sets the refractive power of the third lens unit L3 which moves during zooming and focusing. If the positive refractive power of the third lens unit L3 becomes too strong beyond the lower limit value of the conditional expression (7), off-axis aberrations such as astigmatism and field curvature increase. Further, the aberration fluctuation at the time of focusing from infinity to close in the third lens unit L3 is increased, which is not preferable. If the positive refractive power of the third lens unit L3 becomes too weak beyond the upper limit value of the conditional expression (7), the moving amount of the third lens unit L3 increases during zooming and focusing, and the size of the entire system is reduced. It will be difficult.

The second lens unit L2 has two positive lenses. Condition (8) relates to the average value νd2p _AVE of the Abbe numbers of the materials of the two positive lenses at this time, for reducing defocus in a wide wavelength range from visible light to near-infrared light. A focus shift due to a difference in wavelength occurs under the influence of so-called axial chromatic aberration. Here, the incident height of the axial light beam to each lens surface is the highest at the object-side lens surface of the second lens unit L2. Condition (8) is for effectively correcting axial chromatic aberration by using a lens of an appropriate material at this point.

  If the lower limit value of the conditional expression (8) is exceeded, the correction of the chromatic aberration will be insufficient, and the defocus will increase in the wavelength range from visible light to near infrared light, which is not preferable. In each embodiment, a lens having an aspheric surface is disposed on the most object side of the second lens unit L2 in order to correct spherical aberration that is likely to occur when the F number Fno is reduced (brightened).

  Conditional expression (9) is for achieving wide angle of view while achieving downsizing of the entire system. If the upper limit value of conditional expression (9) is exceeded, the negative refractive power of the first lens unit L1 becomes too weak, and it becomes difficult to achieve a wide angle of view while achieving downsizing of the entire system. Come. If the lower limit value of the conditional expression (9) is exceeded, the negative refractive power of the first lens unit L1 becomes too strong, and various aberrations such as astigmatism and field curvature increase.

  Condition (10) relates to the amount of movement of the second lens unit L2, which is one of the lens units for zooming, during zooming. When the moving amount of the second lens unit L2 increases beyond the upper limit value of the conditional expression (10), the total length of the lens increases, which makes it difficult to miniaturize the entire system. As the moving amount of the second lens unit L2 decreases beyond the lower limit value of the conditional expression (10), it becomes necessary to increase the positive refractive power of the second lens unit L2 in order to obtain a predetermined magnification ratio, and spherical aberration Is not preferable because various aberrations such as The third lens unit L3 moves toward the object side during zooming from the wide-angle end to the telephoto end.

  Condition (11) relates to the amount of movement of the third lens unit L3, which is one of the lens units for zooming, at the time of zooming. The third lens unit L3 plays a role as a variable power lens unit by moving to the object side together with the second lens unit L2. If the moving amount of the third lens unit L3 increases beyond the upper limit value of the conditional expression (11), the total lens length becomes long, and it becomes difficult to miniaturize the entire system. When the moving amount of the third lens unit L3 becomes short beyond the lower limit value of the conditional expression (11), it becomes necessary to strengthen the positive refractive power of the third lens unit L3 in order to obtain a predetermined magnification ratio. It is not preferable because aberrations such as aberration increase.

More preferably, the numerical ranges of conditional expressions (4) to (11) are set as follows.
0.90 <f2 / f3 <1.40 (4a)
1.5 <1GL / | f1 | <2.3 (5a)
0.50 <2GL / f2 <0.80 (6a)
3.8 <f3 / fw <6.5 (7a)
74.0 <νd2p _AVE (8a)
0.038 <fw / OALw <0.055 (9a)
0.8 <| M2 | / √ (fw × ft) <1.2 (10a)
0.9 <| M3 | / √ (fw × ft) <1.4 (11a)

  In each embodiment, the first lens unit L1 is composed of, in order from the object side to the image side, a negative lens, a negative lens, and a cemented lens in which a negative lens and a positive lens are cemented. Alternatively, the first lens unit L1 includes, in order from the object side to the image side, a negative lens, a negative lens, a biconvex positive lens, and a cemented lens in which a negative lens and a positive lens are cemented.

  The second lens unit L2 includes, in order from the object side to the image side, a positive lens, a cemented lens in which a positive lens and a negative lens are cemented, and a positive lens. Alternatively, the second lens unit L2 is composed of, in order from the object side to the image side, a positive lens, and a cemented lens in which a positive lens, a negative lens and a positive lens are cemented. Alternatively, the second lens unit L2 includes, in order from the object side to the image side, a positive lens, a positive lens, and a cemented lens in which a negative lens and a positive lens are cemented. Alternatively, the second lens unit L2 is composed of, in order from the object side to the image side, a positive lens and a cemented lens in which a positive lens and a negative lens are cemented.

  The third lens unit L3 is composed of a positive lens. Alternatively, the third lens unit L3 is composed of a cemented lens in which a negative lens and a positive lens are cemented.

  By configuring as described above, high optical performance is obtained over the entire zoom range. The aperture stop SP is located on the object side of the second lens unit L2, but is configured to be independently movable during zooming. As a result, a ray is appropriately cut at each zoom position, and coma aberration is corrected well.

  Hereinafter, specific lens configurations of the respective embodiments will be described. Hereinafter, the lens configuration will be described as being disposed in order from the object side to the image side unless otherwise noted.

Example 1
The first lens unit L1 includes a meniscus negative lens G11 having a convex surface facing the object side, a biconcave negative lens G12, a meniscus negative lens G13 having a convex surface facing the object, and a convex surface facing the object side It consists of a positive lens G14 having a meniscus shape. The negative lens G13 and the positive lens G14 are cemented. For the negative lens G11, a material with a high refractive index of more than 2.0 is used to achieve a wide angle of view as a strong negative refractive power. The chromatic aberration is corrected well by using a high dispersion material for the positive lens G14.

  The second lens unit L2 is composed of a biconvex positive lens G21, a biconvex positive lens G22, a biconcave negative lens G23, and a meniscus positive lens G24 having a convex surface facing the object side. The positive lens G22 and the negative lens G23 are cemented, and the chromatic aberration is well corrected by setting the difference in Abbe numbers of the materials of both lenses large. Further, both lens surfaces of the positive lens G21 are aspheric. For the positive lens G22, an ultra-low dispersion material having an Abbe number of 90 or more is used, whereby axial chromatic aberration is well corrected over a wide wavelength range from the visible light range to the near infrared range.

  The third lens unit L3 is composed of a positive meniscus lens G31 having a convex surface facing the object side. In the positive lens G31, both lens surfaces are aspheric, so that off-axis aberrations such as astigmatism are corrected well.

(Example 2)
The lens configuration of the first lens unit L1 is the same as that of the first embodiment. The second lens unit L2 is composed of a biconvex positive lens G21, a biconvex positive lens G22, a biconcave negative lens G23, and a meniscus positive lens G24 having a convex surface facing the object side. The positive lens G22, the negative lens G23, and the positive lens G24 are cemented. Both lens surfaces of the positive lens G21 are aspheric. The lens configuration of the third lens unit L3 is the same as that of the first embodiment.

(Example 3)
The lens configuration of the first lens unit L1 is the same as that of the first embodiment. The second lens unit L2 is composed of a biconvex positive lens G21, a biconvex positive lens G22, a biconcave negative lens G23, and a meniscus positive lens G24 having a convex surface facing the object side. The negative lens G23 and the positive lens G24 are cemented. Both lens surfaces of the positive lens G21 are aspheric. The lens configuration of the third lens unit L3 is the same as that of the first embodiment.

(Example 4)
The first lens unit L1 is composed of a meniscus negative lens G11 with a convex surface facing the object side, a meniscus negative lens G12 with a convex surface facing the object side, and a biconvex positive lens G13. Further, it comprises a biconcave negative lens G14 and a meniscus positive lens G15 having a convex surface facing the object side. The negative lens G14 and the positive lens G15 are cemented. Both lens surfaces of the negative lens G12 are aspheric, and distortion is corrected well.

  The second lens unit L2 is composed of a biconvex positive lens G21, a biconvex positive lens G22, and a biconcave negative lens G23. The negative lens G22 and the positive lens G23 are cemented. Both lens surfaces of the positive lens G21 are aspheric. The third lens unit L3 is composed of a negative meniscus lens G31 with a convex surface facing the object side and a positive meniscus lens G32 with a convex surface facing the object side. The negative lens G31 and the positive lens G32 are cemented. The lens surface on the image side of the positive lens G32 is aspheric.

  As described above, according to each embodiment, the zoom lens with a wide angle of view and bright zoom lens having high optical performance over the entire zoom range while having a small size of the entire system, and little focus shift from visible light to near infrared light And an imaging device having the same. For example, it is possible to obtain an image pickup apparatus which covers a full angle of view of 120 ° or more, an F-number Fno of about 1.2 at the wide angle end and about 1.2 of full HD or more pixels.

In each embodiment, the following means may be used.
The shape of the glass shown in the embodiment is not limited to the number of sheets, and may be appropriately changed.
At the time of zooming, it is necessary to move the aperture stop SP independently of the other lens units during fixing or zooming.
-The material of the aspheric lens is not limited to glass, and a hybrid aspheric lens (having aspheric component mounted) formed of resin material on the spherical lens surface (aspheric lens made of plastic material) is used about.

Moving some of the lenses and lens groups so as to have a component in the direction perpendicular to the optical axis, thereby correcting image blurring accompanying vibrations such as camera shake.
When used in an imaging device, correcting distortion aberration and chromatic aberration of the zoom lens by an electrical correction means.
Perform focusing by moving the lens units other than the third lens unit.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to these embodiments and optical specifications (field angle and Fno), and various modifications and changes can be made within the scope of the present invention.

  The zoom lens according to the present invention is used in an imaging apparatus having a solid-state imaging device that receives a formed image. In recent years, in order to process an image digitally, a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) is mainly used. The zoom lens according to the present invention is also used in an image pickup apparatus having a solid-state image pickup device corresponding to the zoom lens.

  Next, an embodiment of a surveillance camera (image pickup apparatus) using the zoom lens according to the present invention as a photographing optical system will be described with reference to FIG. In FIG. 10, reference numeral 30 denotes a monitoring camera main body, and reference numeral 31 denotes an imaging optical system constituted by any of the zoom lenses described in the first to fourth embodiments. Reference numeral 32 denotes a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor which is incorporated in the camera body and receives an object image formed by the imaging optical system 31. In order to obtain high resolution, a high-definition imaging device such as full HD (1920 × 1080) is configured.

  Reference numeral 33 denotes a memory for recording information corresponding to a subject image photoelectrically converted by the solid-state imaging device 32. Reference numeral 34 denotes a network cable for transferring an object image photoelectrically converted by the image 32.

  As described above, according to each embodiment, it is compact but has high optical performance over the entire zoom range, suppresses defocusing in visible light to near infrared light, and has a wide-angle wide bright zoom lens and the same. An imaging device can be obtained. These embodiments are a compact zoom lens that covers a maximum pixel angle of 2 [omega] of 120 [deg.] Or more and an Fno of about 1.2 and can be used for a high pixel image sensor of full HD or more, and an image pickup apparatus having the same.

  Next, numerical data of the embodiments corresponding to the respective embodiments will be shown. In the numerical data of each embodiment, the surface number i indicates the order of optical surfaces counted from the object side. ri is the radius of curvature of the i-th optical surface. di is the i-th and (i + 1) th surface spacing. ndi and νdi respectively indicate the refractive index and Abbe number of the material of the optical member with respect to the d-line. The partial dispersion ratio θCt is a numerical value calculated by (nC−nt) / (nF−nC). * Means aspheric surface.

  Back focus (BF) is the air-equivalent distance from the lens last surface to the paraxial image plane. The total lens length is defined as a value obtained by adding back focus (BF) to the distance from the lens front surface to the lens final surface. An aspheric surface where K is eccentricity, A4, A6, A8, A10 and A12 are aspheric coefficients, and displacement in the direction of the optical axis at the height H from the optical axis is x with the surface vertex as a reference The shape is

Is displayed. Where R is the radius of curvature. Also, for example "e-Z" means ^{"10 -Z".} Table 1 shows the correspondence with the above-described conditional expressions in each example. f is the focal length (d line), Fno is the F-number, with respect to the half angle (omega) is Ru numerical der about photographable angle in consideration of the distortion amount.

Example 1
Unit mm
Surface data
Face number rd nd dd θCt
1 15.193 0.9 2.00100 29.1 0.6835
2 6.518 6.93
3 -19.198 0.6 1.59282 68.6 0.796
4 22.592 0.73
5 32.426 0.45 1.69895 30.1 0.6966
6 8.535 2.9 1.94595 18.0 0.6319
7 28.883 (variable)
8 (stop) ∞ (variable)
9 * 9.796 4.2 1.59201 67.0 0.8499
10 *-35.715 0.15
11 8.797 3.14 1.43875 94.9 0.8373
12-25.439 0.4 1.68893 31.1 0.6995
13 6.128 0.4
14 6.08 2.13 1.59282 68.6 0.796
15 8.736 (variable)
16 * 6.193 3.4 1.55332 71.7 0.8164
17 * 220.717 (variable)
18 1.7 1.7 1.51633 64.1-
19 0.6 0.67
Image plane

Aspheric data
9th surface
K = -6.34322e-001 A 4 = 3.01103e-005 A 6 = 4.94887e-006
A 8 = -1.73940e-007 A10 = 4.02943e-009
Face 10
K = 0.00000e + 000 A 4 = 1.38348e-004 A 6 = 4.97780e-006
A8 = -2.05255e-007 A10 = 5.55060e-009
16th
K = 0.00000e + 000 A 4 = 3.80202e-005 A 6 = 2.86108e-006
A 8 = 3.92446e-007 A10 =-2.76685e-009 A12 =-8.44640e-028
17th
K = 0.00000e + 000A 4 = 1.23294e-003 A 6 = 5.48588e-005
A 8 = -2.64115e-006 A10 = 2.36700e-007

Various data
Zoom ratio 2.30
Wide-angle Mid-telephoto
Focal length 2.59 4.32 5.95
F number 1.24 1.52 1.81
Half angle of view (degrees) 70.8 40.7 29.2
Image height 3.04 3.04 3.04
Lens total length 52.45 43.62 41.49
BF 4.55 7.21 9.56

Spacing Wide-angle Mid-telephoto
d 7 15.55 6.72 4.60
d 8 4.41 2.28 0.15
d15 1.60 1.06 0.85
d17 2.76 5.43 7.77

Group focal length
First group-6.83
Second group 13.71
Three groups 11.45

Example 2
Unit mm
Surface data
Face number rd nd dd θCt
1 15.497 0.9 2.00100 29.1 0.6835
2 6.79 7.1
3 -22.334 0.6 1.59282 68.6 0.796
4 17.343 1.02
5 34.334 0.45 1.68893 31.1 0.6995
6 9.149 3.0 2.00272 19.3 0.6315
7 31.213 (variable)
8 (stop) ∞ (variable)
9 * 8.854 4.2 1.59201 67.0 0.8499
10 * -44.907 0.15
11 10.209 2.74 1.43875 94.9 0.8373
12 -57.777 0.4 1.68893 31.1 0.6995
13 5.272 1.73 1.59282 68.6 0.796
14 9.443 (variable)
15 * 5.539 3.4 1.55332 71.7 0.8164
16 * 29.154 (variable)
17 1.7 1.7 1.51633 64.1-
18 0.6 0.60
Image plane

Aspheric data
9th surface
K = -7. 2856 e-001 A4 = 1.60037 e-005 A 6 = 4.06409 e-006
A 8 = -1.81753e-007 A10 = 3.43748e-009
Face 10
K = 0.00000e + 000 A 4 = 1.11527e-004 A 6 = 3.76311e-006
A 8 = -2.41163e-007 A10 = 5.07980e-009
15th
K = 0.00000e + 000 A 4 = 1.32027e-004 A 6 = 6.38206e-006
A 8 = -6.22902e-008 A10 = 2.77300e-008 A12 = 2.53514e-025
16th
K = 0.00000e + 000 A 4 = 1.76432e-003 A 6 = 7.64146e-005
A 8 = -3.40910e-006 A10 = 4.01662e-007

Various data
Zoom ratio 2.31
Wide-angle Mid-telephoto
Focal length 2.56 4.21 5.92
F number 1.24 1.53 1.84
Half angle of view (degrees) 69.8 40.9 28.7
Statue height 3.0 3.0 3.0
Lens total length 52.44 43.34 40.42
BF 4.55 6.81 9.06

Spacing Wide-angle Mid-telephoto
d7 16.7 7.6 4.68
d8 3.81 1.98 0.15
d14 1.70 1.26 0.85
d16 2.83 5.09 7.34

Group focal length
First group-7.27
Second group 14.18
Three groups 11.75

[Example 3]
Unit mm
Surface data
Face number rd nd dd θCt
1 19.748 0.9 2.00100 29.1 0.6835
2 7.76 7.48
3-22.065 0.6 1.49700 81.5 0.8258
4 16.334 1.62
5 21.817 0.45 1.69895 30.1 0.6966
6 10.511 2.9 1.94595 18.0 0.6319
7 27.733 (variable)
8 (stop) ∞ (variable)
9 * 10.366 3.73 1.59201 67.0 0.8499
10 * -73.645 0.15
11 11.504 3.64 1.43875 94.9 0.8373
12 -11.103 0.32
13-19.425 0.4 1.69895 30.1 0.6966
14 4.972 1.37 1.88300 40.8 0.7381
15 7.837 (variable)
16 * 5.089 2.8 1.55332 71.7 0.8164
17 * 17.126 (variable)
18 1.7 1.7 1.51633 54.1-
19 0.6 0.62
Image plane

Aspheric data
9th surface
K = -6.04458e-001 A 4 = -6.41371e-005 A 6 = 7.18786e-007
A8 = -7.50103e-008 A10 = -1.51296e-009
Face 10
K = 0.00000e + 000 A 4 = 8.05633e-005 A 6 = 4.08556e-006
A 8 = -2.18138e-007 A10 = 2.79999e-009
16th
K = 0.00000e + 000 A 4 = 5.09719e-005 A 6 = 9.66019e-006
A8 = -8.37614e-008 A10 = 2.37850e-008 A12 = 4.43637e-021
17th
K = 0.00000e + 000A 4 = 2.12830e-003 A 6 = 6.49444e-005
A 8 = 1.08492e-006 A10 = 2.07340e-007

Various data
Zoom ratio 2.41
Wide-angle Mid-telephoto
Focal length 2.59 4.42 6.24
F number 1.24 1.57 1.90
Half angle of view (degrees) 70.3 39.1 27.4
Statue height 3.0 3.0 3.0
Lens total length 55.95 44.71 41.38
BF 4.55 6.83 9.04

Spacing Wide-angle Mid-telephoto
d 7 18.79 6.55 2.22
d 8 4.25 3.20 2.15
d15 1.99 1.76 1.6
d17 2.81 5.09 7.30

Group focal length
1 group-8.2
Second group 14.56
Three groups 12.09

Example 4
Unit mm
Surface data
Face number rd nd dd θCt
1 19.998 1.1 2.00100 29.1 0.6835
2 9.8 4.89
3 * 39.03 0.9 1.85135 40.1 0.7361
4 * 8.488 3.49
5 25.417 2.52 1.52249 59.8 0.8326
6-30.904 1.3
7 -13.249 0.6 1.48749 70.2 0.8924
8 16.581 2.2 1.94595 18.0 0.6319
9 67.783 (variable)
10 (stop) ∞ (variable)
11 * 11.371 3.79 1.62299 58.1 0.8464
12 *-84.147 0.15
13 8.351 4.4 1.43700 95.1 0.8427
14-28.613 0.6 1.80518 25.4 0.6680
15 12.613 (variable)
16 7.955 0.75 1.80518 25.4 0.6680
17 4.645 3.2 1.69350 53.2 0.8143
18 * 194.725 (variable)
19 ∞ 1.2 1.51633 64.1-
20 1. 1.75
Image plane

Aspheric data
Third side
K = 5.19045e + 000 A 4 = 3.14005e-004 A 6 =-5.92 273e-006
A8 = 8.08528e-008 A10 = -6.68118e-010 A12 = 2.50048e-012
Fourth side
K = 0.00000e + 000A 4 = 2.31240e-004 A 6 =-5.86228e-006
A 8 = 4.44980e-008 A10 =-6.72826e-010
11th
K = -5.65257e-001 A4 = 7.78684e-005 A6 = 4.48090e-006
A8 = -1.16430e-007 A10 = 3.41115e-009 A12 = -8.78512e-012
12th
K = 0.00000e + 000 A 4 = 1.40914e-004 A 6 = 5.75346e-006
A8 = -1.82577e-007 A10 = 5.39920e-009 A12 = 8.03250e-021
18th
K = 0.00000e + 000 A 4 = 7.99 389 e-004 A 6 = 1.73784 e-006
A 8 = 4.40833e-007 A10 = -1.00417e-008

Various data
Zoom ratio 2.32
Wide-angle Mid-telephoto
Focal length 2.51 4.14 5.82
F number 1.23 1.48 1.75
Half angle of view (degrees) 62.1 39.7 28.9
Statue height 3.05 3.05 3.05
Lens total length 60.52 48.86 44.86
BF 4.54 6.79 9.03

Spacing Wide-angle Mid-telephoto
d 9 19.45 7.78 3.79
d10 4.04 2.1 0.15
d15 2.6 2.3 2.0
d18 2.0 4.25 6.49

Group focal length
One group-8.01
Second group 14.86
Three groups 13.28

L0 zoom lens L1 first lens unit L2 second lens unit L3 third lens unit

Claims (18)

The first lens group of negative refractive power, the second lens group of positive refractive power, and the third lens group of positive refractive power, which are disposed in order from the object side to the image side, and are adjacent to each other during zooming A zoom lens in which all lens groups move so that the distance changes , and
The second lens group includes a positive lens A,
The refractive index of the material for light of wavelength 486.13 nm is nF, the refractive index of the material for light of wavelength 587.6 nm is nd, the refractive index of the material for light of wavelength 656.27 nm is nC, the material for light of wavelength 1013.98 nm Of the material, and the Abbe number .nu.d of the material and the partial dispersion ratio .theta.Ct, respectively: .nu.d = (nd-1) / (nF-nC)
θCt = (nC−nt) / (nF−nC)
And,
Assuming that the Abbe number of the material of the positive lens A is ddA, the partial dispersion ratio is θCtA , the focal length of the first lens group is f1, and the focal length of the second lens group is f2.
85.0 <νdA
−0.25 <θCtA− (0.0047 × νdA + 0.546) <− 0.10
−0.85 <f1 / f2 <−0.35
A zoom lens characterized by satisfying the following conditional expression. When the focal length of the third lens group is f3
0.75 <f2 / f3 <1.50
The zoom lens according to claim 1, which satisfies the following conditional expression. When the first lens group includes two or more negative lenses, and the thickness of the first lens group on the optical axis is 1GL,
1.3 <1GL / | f1 | <2.4
The zoom lens according to claim 1 or 2, wherein the following conditional expression is satisfied. When the second lens group includes two or more positive lenses, and the thickness of the second lens group on the optical axis is 2GL,
0.45 <2GL / f2 <0.95
The zoom lens according to any one of claims 1 to 3, wherein the following conditional expression is satisfied. When the third lens unit is moved during focusing, the focal length of the third lens unit is f3, and the focal length of the entire system at the wide-angle end is fw,
3.2 <f3 / fw <7.0
The zoom lens according to any one of claims 1 to 4, wherein the following conditional expression is satisfied. The second lens group includes two positive lenses arranged in succession from the object side, a positive lens disposed on the object side of the two positive lenses have the lens surfaces of aspherical shape When the average value of the Abbe numbers of the materials of the two positive lenses is dd2p _AVE ,
70 <νd2p _AVE
The zoom lens according to any one of claims 1 to 5, wherein the following conditional expression is satisfied. Assuming that the focal length of the entire system at the wide angle end is fw and the total lens length at the wide angle end is OALw,
0.034 <fw / OALw <0.060
The zoom lens according to any one of claims 1 to 6, wherein the following conditional expression is satisfied. Assuming that the moving amount of the second lens group during zooming from the wide-angle end to the telephoto end is M2, the focal length of the entire system at the wide-angle end is fw, and the focal length of the entire system at the telephoto end is ft
0.6 <| M2 | / √ (fw × ft) <1.3
The zoom lens according to any one of claims 1 to 7, wherein the following conditional expression is satisfied. During zooming from the wide-angle end to the telephoto end, the third lens group moves to the object side, and the moving amount of the third lens group in zooming from the wide-angle end to the telephoto end is M3, the focal length of the entire system at the wide-angle end When fw and the focal length of the entire system at the telephoto end are ft,
0.8 <| M3 | / √ (fw × ft) <1.6
The zoom lens according to any one of claims 1 to 8, satisfying the following conditional expression. 10. The first lens group according to claim 1, wherein the first lens group comprises a negative lens, a negative lens, and a cemented lens formed by cementing a negative lens and a positive lens, disposed in order from the object side to the image side. The zoom lens according to any one of the above. The first lens group is characterized by comprising a negative lens, a negative lens, a biconvex positive lens, and a cemented lens formed by cementing a negative lens and a positive lens, disposed in order from the object side to the image side. The zoom lens according to any one of claims 1 to 9, wherein The second lens group, disposed in order from the object side to the image side, a positive lens, according to claim 1 to 11 cemented lens positive lens and a negative lens, which are joined, characterized in that it is composed of a positive lens The zoom lens according to any one of the above. The second lens group, disposed in order from the object side to the image side, a positive lens, according to claim 1 to 11 a positive lens and a negative lens and a positive lens is characterized in that it is composed of a cemented lens consisting joined The zoom lens according to any one of the above. The second lens group includes a positive lens, a positive lens, and a cemented lens formed by cementing a negative lens and a positive lens, disposed in order from the object side to the image side. The zoom lens according to any one of the above. The second lens group, disposed in order from the object side to the image side, a positive lens, any one of claims 1 to 11 positive lens and the negative lens is characterized in that it is composed of a cemented lens consisting joined The zoom lens according to item 1.   The zoom lens according to any one of claims 1 to 15, wherein the third lens group is composed of a positive lens. The zoom lens according to any one of claims 1 to 15, wherein the third lens group is configured of a cemented lens in which a negative lens and a positive lens are cemented .   An image pickup apparatus comprising: the zoom lens according to any one of claims 1 to 17; and an image pickup element for receiving an image formed by the zoom lens.