JP7009138B2 - Zoom lens and image pickup device with it - Google Patents

Description

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

The zoom lens used in the image pickup device is required to have high optical performance corresponding to high definition of the image pickup element and to have a wide angle of view. Further, an imaging device such as a surveillance camera uses visible light for daytime imaging and near-infrared light for nighttime imaging.

For example, in surveillance cameras, in many cases, near-infrared light having a wavelength of 800 nm to 1000 nm is used for nighttime photography to facilitate photography under low illuminance. Therefore, it is required that the zoom lens used for the surveillance camera is a zoom lens in which various aberrations are well corrected in a wide wavelength range from visible light (wavelength 400 nm to 700 nm) to the near infrared region. Has been done.

Conventionally, as a zoom lens, a negative lead type zoom lens in which a lens group having a negative refractive power is arranged on the most object side is known (Patent Documents 1 and 2).

In Patent Document 1, a three-group zoom lens is composed of a first lens group to a third lens group having negative, positive, and negative refractive powers in order from the object side to the image side, and the distance between adjacent lens groups changes during zooming. Is disclosed. In Patent Document 2, it is composed of a first lens group to a fourth lens group having negative, negative, positive, and negative refractive powers in order from the object side to the image side, and the four groups in which the distance between adjacent lens groups changes during zooming. The zoom lens is disclosed.

In addition, there is known a negative lead type zoom lens in which aberrations are satisfactorily corrected over a wide wavelength range from visible light to near infrared light (Patent Document 3). In Patent Document 3, a three-group zoom lens is composed of a first lens group to a third lens group having negative, positive, and negative refractive powers in order from the object side to the image side, and the distance between adjacent lens groups changes during zooming. Is disclosed.

Japanese Unexamined Patent Publication No. 2007-23405 Japanese Unexamined Patent Publication No. 2014-219543 Japanese Unexamined Patent Publication No. 2016-145928

In the negative lead type zoom lens mentioned above, it is important to properly set the lens configuration of each lens group in order to obtain high optical performance over the entire zoom range while the entire system is small and has a wide angle of view. Come on. For example, in a zoom lens used for a surveillance camera, it is important to have high optical performance in which chromatic aberration is particularly well corrected among various aberrations over a wide wavelength range from the visible region to the near infrared region.

In a negative lead type zoom lens, in order to satisfactorily correct chromatic aberration of magnification over a wide wavelength range and obtain high optical performance, the lens configuration of the first lens group and the lens material used for the lens group arranged on the image side most. It is important to set such things appropriately. If these configurations are inappropriate, it becomes very difficult to obtain a zoom lens having a wide angle of view and high optical performance over a wide wavelength range while reducing the size of the entire system.

An object of the present invention is, for example, to provide a zoom lens which is advantageous in terms of small size , wide angle of view, and high optical performance in the entire zoom range.

The zoom lens of the present invention has an aperture aperture and a plurality of lens groups, and the plurality of lens groups are one or more first lens groups having a negative refractive power arranged in order from the object side to the image side. It is a zoom lens that is composed of an intermediate group and a rear lens group including the lens group of the above lens group, and the distance between adjacent lens groups changes during zooming.
The first lens group has two or more negative lenses and one or more positive lenses.
The rear lens group has a lens element nr having a negative refractive power arranged on the image side most.
When the Abbe number and the partial dispersion ratio of the material of the lens element nr are νdnr and θCtnr, respectively,
20.4 ≤ νdnr ≤ 29.5
0.45 <θCtnr <0.78
Including a negative lens that satisfies the conditional expression
The aperture diaphragm is arranged on the image side of the first lens group, and includes a lens group LP having a positive refractive force arranged adjacent to the image side of the aperture diaphragm, and the lens group LP is telescopic from the wide-angle end. Moving to the object side when zooming to the edge, the lens group Lp has a plurality of positive lenses, and the largest Abbe number among the Abbe numbers of the plurality of positive lenses is νpdp1, and the second largest Abbe number is νpdp2. and when,
75 <(νdp1 + νpd2) / 2 <96
Satisfy the conditional expression
When the refractive indexes of the material at the d-line, C-line, t-line, and F-line are nd, nC, nt, and nF, respectively, the partial dispersion ratio is represented by (nC-nt) / (nF-nC). It is a zoom lens characterized by this.

According to the present invention, for example, a zoom lens which is advantageous in terms of small size , wide angle of view, and high optical performance in the entire zoom range can be obtained.

Figure of lens cross section and movement locus at wide-angle end of Example 1 (A), (B), (C) Aberration diagram at the wide-angle end, intermediate zoom position, and telephoto end of Example 1. Figure of lens cross section and movement locus at wide-angle end of Example 2 (A), (B), (C) Aberration diagram at the wide-angle end, intermediate zoom position, and telephoto end of Example 2. Figure of lens cross section and movement locus at wide-angle end of Example 3 (A), (B), (C) Aberration diagram at the wide-angle end, intermediate zoom position, and telephoto end of Example 3. Figure of lens cross section and movement locus at wide-angle end of Example 4 (A), (B), (C) Aberration diagram at the wide-angle end, intermediate zoom position, and telephoto end of Example 4. Cross-sectional view of the lens in the surveillance camera (imaging device) of the present invention Outline of the main part in the surveillance camera of the present invention (A), (B) Explanatory drawing of glass characteristics (product name S-NPH1, product name S-LAH53) Explanatory drawing about an optical path at a wide-angle end and a telephoto end of Example 1.

Hereinafter, the zoom lens of the present invention and the image pickup apparatus having the same will be described with reference to the drawings. The zoom lens of the present invention is composed of a first lens group having a negative refractive power, an intermediate group including one or more lens groups, and a rear group arranged in order from the object side to the image side, and adjacent lenses for zooming. The spacing of the groups changes.

FIG. 1 is a cross-sectional view of a lens at a wide-angle end (short focal length end) of the zoom lens according to the first embodiment of the present invention. 2A, 2B, and 2C are aberration diagrams at the wide-angle end, the intermediate 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 2.90 and an F number of 1.67 to 2.97. FIG. 3 is a cross-sectional view of the lens at the wide-angle end of the zoom lens according to the second embodiment of the present invention. 4 (A), (B), and (C) are aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end of the zoom lens according to the second embodiment of the present invention. The second embodiment is a zoom lens having a zoom ratio of 2.3 and an F number of 1.28 to 1.64.

FIG. 5 is a cross-sectional view of the lens at the wide-angle end of the zoom lens according to the third embodiment of the present invention. 6 (A), (B), and (C) are aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end of the zoom lens according to the third embodiment of the present invention. Example 3 is a zoom lens having a zoom ratio of 2.6 and an F number of 1.35 to 2.40.

FIG. 7 is a cross-sectional view of the zoom lens according to the fourth embodiment of the present invention at the wide-angle end. 8 (A), (B), and (C) are aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end of the zoom lens according to the fourth embodiment of the present invention. Example 4 is a zoom lens having a zoom ratio of 2.3 and an F number of 1.24 to 1.68.

FIG. 9 is a cross-sectional view of the lens when the zoom lens of the present invention is housed in the dome. FIG. 10 is a schematic view of a main part of a surveillance camera (imaging device) having a zoom lens of the present invention. 11 (A) and 11 (B) are explanatory views of the characteristics of the material (optical material) used for the zoom lens of the present invention. 12 (A) and 12 (B) are optical path diagrams at the wide-angle end and the telephoto end of the zoom lens of the first embodiment.

The zoom lens of each embodiment is an image pickup optical system used in an image pickup apparatus, and in a cross-sectional view of the lens, the left side is the object side (front side) and the right side is the image side (rear side). The zoom lens of each embodiment may be used for an optical device such as a projector. In this case, the left side is the screen and the right side is the projected image. In the lens cross-sectional view, L0 is a zoom lens.

LM is an intermediate group having one or more lens groups. LR is the rear group located most on the image side. Li is the i-th lens group. L1 is a first lens group having a negative refractive power (optical power = reciprocal of focal length). The SP is an F number determining member (hereinafter, also referred to as “opening diaphragm”) that acts as an aperture diaphragm that determines (limits) the open F number (Fno) luminous flux. Lp is a group of lenses having a positive refractive power arranged adjacent to the image side of the aperture stop SP.

G is an optical block corresponding to an optical filter, a face plate, a crystal low-pass filter, an infrared cut filter, and the like. The IP is an image plane, and when used as a shooting optical system of a video camera or a digital still camera, an image pickup surface of a solid-state image pickup element (photoelectric conversion element) such as a CCD sensor or a CMOS sensor is placed.

The arrows show the movement trajectory of each lens group during zooming from the wide-angle end to the telephoto end. The arrow Fa related to focus indicates the movement locus of the lens group during zooming from the wide-angle end to the telephoto end when focusing at infinity. Further, the arrow Fb indicates the movement locus of the lens group during zooming from the wide-angle end to the telephoto end when focusing on a short distance. The arrow Fc indicates the direction of movement of the lens group during focusing from infinity to a short distance.

The arrow F regarding the focus in FIG. 7 indicates the direction of movement during focusing from infinity to a short distance.

In terms of spherical aberration, d indicates the d line (wavelength 587.6 nm), C indicates the C line (wavelength 656.3 nm), F indicates the F line (wavelength 486.13 nm), and t indicates the t line (wavelength 1013.98 nm). is doing. In astigmatism, ΔM represents the meridional image plane of the d-line, and ΔS represents the sagittal image plane of the d-line. In the distortion aberration, the d line is displayed. In the chromatic aberration of magnification, the aberrations of the C line, the F line, and the t line with respect to the d line are displayed. Fno is the F number and ω is the half angle of view (degrees).

The zoom lens of the present invention is composed of three or more lenses. In order to obtain high optical performance over the entire zoom range from the wide-angle end to the telephoto end while reducing the size of the entire system, the lens configuration is suitable for changing the spacing between each lens group to perform scaling. Further, in order to achieve a wide angle of view at the wide-angle end, a negative lead type is adopted because the lens group on the most object side has a negative refractive power. The first lens group has a lens configuration with many negative lenses in order to have a strong negative refractive power.

Further, in order to satisfactorily correct the chromatic aberration of magnification not only in the visible region but also in the near infrared region, a lens configuration made of a material different from the conventional one is adopted. This will be described with reference to FIGS. 11A, 11B, and 12.

The zoom lens of the present invention has a lens element (lens element) nr having the most negative refractive power on the image side, and the lens element nr has a relatively large difference in refractive index between the visible region and the near infrared region. It has the characteristic (more dispersibility). This is because the refractive index of the material in the near infrared region should be as low as possible with respect to the refractive index of visible light.

The reason is that in the entire lens system, near-infrared light is imaged on the over side (plus direction in the chromatic aberration of magnification diagram) with respect to visible light. Therefore, in order to correct this, it is preferable that the lens element nr has a dispersibility in which the refractive index of near-infrared light becomes small. Therefore, it is better to select a material having a large dispersion of the t-line (wavelength 1013.98 nm) with reference to the d-line (wavelength 587.6 nm), and specifically, to select a material having a small Abbe number νd. good.

Regarding the partial dispersion ratio θct, it is better to select a material that becomes smaller as shown in the general characteristics (from the map issued by O'Hara Co., Ltd. in FIG. 11B) that change according to the Abbe number νd. FIG. 11B shows the Abbe number νd and the partial dispersion ratio θct.

Next, using FIG. 11 (A), two types of OHARA Co., Ltd. (trade name S-NPH1 and trade name S-LAH53) are taken as examples as glass materials having almost the same refractive index of the d-line and different dispersibility. I will explain the principle.

FIG. 11A shows the change in the refractive index at each wavelength. The table shows the refractive indexes of d-line (wavelength 587.56 nm), F-line (wavelength 486.13 nm), C-line (wavelength 656.27 nm), t-line (wavelength 1013.98 nm), nd, nF, nC, nt and Abbe. The number νd and the partial dispersion ratio θCt are shown.

The product name S-NPH1 has a large dispersibility (the Abbe number is small), and the refractive index of the t-line with respect to the d-line is smaller than that of the product name S-LAH53. This is because the trade name S-NPH1 has a characteristic that the dispersibility in the near-infrared region with respect to the d-line is larger. As a result, if the trade name S-NPH1 is selected, the amount of chromatic aberration of magnification in the near-infrared over direction can be suppressed due to the dispersion characteristics while keeping the refractive index of the d-line at the same level. As a result, chromatic aberration of magnification in the near infrared region with respect to the visible light region can be suppressed.

Normally, in the case of imaging only with a color image, it is sufficient to consider up to the wavelength level of C line in the long wavelength region, but when considering up to near-infrared light having a wavelength of about 1000 nm, the above-mentioned principle is used. The effect is obtained. As shown in FIGS. 12A and 12B, the lens element nr having a negative refractive power located closest to the image plane has the above characteristics at each image height from the wide-angle end to the telephoto end. Differences are unlikely to occur in the passing optical path region of the lens element nr. Therefore, this is to efficiently correct the chromatic aberration of magnification over the entire zoom range.

Here, the lens element nr having the most negative refractive power on the image side means an element having a negative refractive power as a whole due to a single lens or a junction lens.

The present invention is a compact zoom lens with a wide angle of view, which has high optical performance over the entire zoom range while the entire system is compact, and has little chromatic aberration of magnification in a wide wavelength range from visible light to near-infrared light. be. The zoom lens of the present invention is composed of a first lens group L1 having a negative refractive power, an intermediate group LM including one or more lens groups, and a rear group LR arranged in order from the object side to the image side.

The first lens group L1 has two or more negative lenses and one or more positive lenses, and the rear group LR has a lens element nr having a negative refractive power on the image side most. The refractive indexes of the material at the d-line, C-line, t-line, and F-line are nd, nC, nt, and nF, respectively. Abbe number νd and partial dispersion ratio θct of the material, respectively.

νd = (nd-1) / (nF-nC)
θCt = (nC-nt) / (nF-nC)
far. And when the Abbe number and the partial dispersion ratio of the material of the lens element nr are νdnr and θCtnr, respectively,

10.0 <νdnr <33.0 ... (1)
0.45 <θCtnr <0.78 ... (2)
Satisfies the conditional expression.

Next, the technical meaning of each of the above conditional expressions will be described. The conditional equations (1) and (2) are for satisfactorily correcting the chromatic aberration of magnification from the visible region to the near infrared region. If the upper limit of the conditional expression (1) is exceeded, a material having a large refractive index in the near infrared is selected, so that the chromatic aberration of magnification in the near infrared with respect to visible light becomes large, which is not preferable. If the lower limit of the conditional expression (1) is exceeded, the correction of the chromatic aberration of magnification in the near infrared with respect to visible light becomes excessive, and the amount of chromatic aberration of magnification increases, which is not preferable.

If the upper limit of the conditional expression (2) is exceeded, a material having a small dispersion of t-line with respect to C-line will be selected, and the correction of chromatic aberration of magnification will be insufficient, which is not preferable. If the lower limit of the conditional expression (2) is exceeded, a material having a large dispersion of the t-line with respect to the C line will be selected, and the correction of the chromatic aberration of magnification will be excessive, and the chromatic aberration of magnification will increase, which is not preferable.

It is more preferable to limit the conditional expressions (1) and (2) as follows.
15.0 <νd <31.0 ... (1a)
0.60 <θCt <0.72 ... (2a)

In each embodiment, it is more preferable to satisfy one or more of the following conditions. The focal length of the first lens group L1 is f1, and the focal length of the entire system at the wide-angle end is fw. The zoom lens has an aperture stop SP and has a lens group LP having a positive refractive power adjacent to the image side of the aperture stop SP. The lens group LP moves to the object side when zooming from the wide-angle end to the telephoto end, and the focal length of the lens group LP is fp. Let the focal length of the rear group LR be fn and the focal length of the lens element nr be fnr.

The Abbe number of the material of the positive lens included in the first lens group L1 is νd1p, and the refractive index of the material of the positive lens included in the first lens group L1 is Nd1p. All the lens groups located on the object side of the aperture stop SP are referred to as the front lens group, and all the lens groups located on the image side of the aperture stop SP are referred to as the rear lens group. The focal length of the front lens group at the wide-angle end is fAw, and the focal length of the rear lens group at the wide-angle end is fBw.

The lens group Lp has a plurality of positive lenses, and the largest Abbe number among the Abbe numbers of the materials of the plurality of positive lenses is νpdp1, and the second largest Abbe number is νpdp2. At this time, it is preferable to satisfy one or more of the following conditional expressions.

-6.0 <f1 / fw <-2.0 ... (3)
1.5 <fp / fw <5.0 ... (4)
0.50 << | fnr / fn | <3.00 ... (5)
12.0 <νd1p <28.0 ... (6)
1.75 <Nd1p <2.20 ... (7)
-1.2 <fAw / fBw <-0.4 ... (8)
75.0 <(νdp1 + νpd2) / 2 <96.0 ... (9)

Next, the technical meaning of each of the above conditional expressions will be described. The conditional expression (3) is for widening the angle of view while reducing the size of the entire system. If the upper limit of the conditional expression (3) is exceeded, the negative refractive power of the first lens group L1 becomes too strong (the absolute value of the negative refractive power becomes too large), resulting in curvature of field over the entire zoom range. It becomes difficult to correct chromatic aberration of magnification. If the lower limit of the conditional expression (3) is exceeded, the negative refractive power of the first lens group L1 becomes too weak (the absolute value of the negative refractive power becomes too small), making it difficult to widen the angle of view. Become.

Further, the amount of movement of the first lens group L1 during zooming increases, the total length of the lens becomes longer, and the effective diameter of the front lens becomes larger, which makes it difficult to reduce the size of the entire system.

In the conditional equation (4), the relationship between the focal length of the entire system at the wide-angle end and the refractive power of the lens group Lp, which is the lens group for scaling, is appropriately set to reduce the size of the entire system and cover the entire zoom range. This is to obtain high optical performance. If the upper limit of the conditional expression (4) is exceeded, the positive refractive power of the lens group Lp becomes too weak, the amount of movement of the lens group Lp during zooming increases, and it becomes difficult to miniaturize the entire system.

If the lower limit of the conditional expression (4) is exceeded, the positive refractive power of the lens group Lp becomes too strong, and it becomes difficult to correct the spherical aberration when increasing the aperture (when the FNO is reduced). The aperture stop SP is placed at a position on the object side of the lens group for scaling in order to facilitate control of the on-axis luminous flux (FNO) without kicking the off-axis luminous flux.

Conditional expression (5) relates to the negative refractive power of the lens element nr having the negative refractive power located closest to the image side. Since the lens element nr is located closest to the image side, it is necessary to bounce a light ray in order to secure a desired image height. Therefore, the conditional expression (5) defines the refractive power.

If the upper limit of the conditional expression (5) is exceeded, the refractive power of the rear group LR becomes too weak, so that it is necessary to increase the lens thickness and the lens diameter. Then, it becomes difficult to miniaturize the entire system. If the lower limit of the conditional expression (5) is exceeded, the refractive power of the rear group LR becomes too strong, so that the light beam jumps up rapidly and the angle of incidence of the light ray on the image sensor becomes too large. Then, it becomes difficult to secure a sufficient amount of light at the outermost peripheral image height, and the optical performance deteriorates.

The conditional expressions (6) and (7) define the characteristics of the material of the positive lens included in the first lens group L1. Conditional expression (6) is for correcting chromatic aberration generated from a negative lens included in the first lens group L1 with respect to correction of chromatic aberration. If the upper limit of the conditional expression (6) is exceeded, the correction of chromatic aberration of magnification will be insufficient. If the lower limit of the conditional expression (6) is exceeded, the amount of correction for chromatic aberration of magnification becomes too large and decreases in the opposite direction, resulting in deterioration of optical performance.

If the upper limit of the conditional expression (7) is exceeded, the refractive index becomes too large, and it becomes difficult to correct spherical aberration and axial chromatic aberration in a well-balanced manner. If the lower limit of the conditional expression (7) is exceeded, spherical aberration is insufficiently corrected at the telephoto end, which is not preferable. Further, it is necessary to increase the lens thickness in order to obtain the refractive power of the positive lens, which makes it difficult to reduce the size of the entire system.

Conditional expression (8) relates to an arrangement of refractive powers for achieving a wide angle of view. Each embodiment has a lens configuration consisting of three or more lens groups, adopts a retrofocus type suitable for widening the angle of view, and has a front lens group having a negative refractive power toward the object side based on the aperture stop SP. It consists of a rear lens group with a positive refractive power on the image side. In order to widen the angle, it is necessary to strengthen the negative refractive power of the front lens group.

If the upper limit of the conditional expression (8) is exceeded, the negative refractive power of the front lens group becomes too strong, and it becomes difficult to correct curvature of field and chromatic aberration over the entire zoom range. If the lower limit of the conditional expression (8) is exceeded, the negative refractive power of the first lens group L1 becomes too weak, and it becomes difficult to widen the angle of view. Further, during zooming, the amount of movement of the first lens group L1 increases, the total length of the lens becomes long, and the effective diameter of the front lens becomes large, which makes it difficult to reduce the size of the entire system.

The conditional expression (9) relates to the material of the positive lens included in the lens group Lp for correcting the axial chromatic aberration. When the axial chromatic aberration becomes large, color bleeding and resolution are likely to be lost. Therefore, the axial chromatic aberration is effectively corrected by using a material that satisfies this conditional equation (9).

If the upper limit of the conditional expression (9) is exceeded, an ultra-low dispersion material is used, which tends to result in a low refractive index as a generally existing material. Therefore, it becomes difficult to secure the refractive power as a lens. This requires measures such as increasing the lens thickness, making it difficult to reduce the size of the entire system. If the lower limit of the conditional expression (9) is exceeded, the correction of chromatic aberration is insufficient, which is not good.

More preferably, it is preferable to set the numerical range of the conditional expressions (3) to (9) as follows.
-5.7 <f1 / fw <-2.8 ... (3a)
1.8 <fp / fw <4.3 ... (4a)
0.7 << | fnr / fn | <2.2 ... (5a)
13.0 <νd1p <24.0 ... (6a)
1.78 <Nd1p <2.05 ... (7a)
-1.0 <fAw / fBw <-0.5 ... (8a)
78.0 <(νdp1 + νpd2) / 2 <90.0 ... (9a)

Next, the lens configuration of the zoom lens of each embodiment will be described. The zoom lens of the first embodiment has a first lens group L1 having a negative refractive power, a second lens group L2 having a negative refractive power, an aperture aperture SP, and a third lens group having a positive refractive power arranged in order from the object side to the image side. It is composed of a lens group L3. The second lens group L2 moves toward the object when focusing from infinity to a short distance.

The second lens group L2 corresponds to the intermediate group LM. The third lens group L3 corresponds to the rear group LR and the lens group Lp. The first lens group L1 and the second lens group L2 correspond to the front lens group. The third lens group L3 corresponds to the rear lens group.

The first lens group L1 is composed of a negative lens G11 having a convex meniscus shape on the object side, a negative lens G12 having a biconcave shape, a negative lens G13 having a convex meniscus shape on the image side, and a positive lens G14 having a meniscus shape having a convex surface on the object side. There is. A material having a relatively high dispersibility is used for the positive lens G14 in order to correct the chromatic aberration of magnification.

The second lens group L2 is formed by a negative lens G21 having a meniscus shape whose image side is convex. For the negative lens G21, a material having relatively low dispersibility is used in order to suppress fluctuations in chromatic aberration of magnification due to focusing.

The third lens group L3 includes a biconvex positive lens G31, a biconvex positive lens G32, a biconcave negative lens G33, a biconvex positive lens G34, and a meniscus-shaped positive lens G35 having a convex image side. The image side is made of a negative lens G36 having a convex meniscus shape. The negative lens G32 and the positive lens G33 are made of a bonded lens, and chromatic aberration is satisfactorily corrected by having a difference in the Abbe number of materials.

Further, by using a material having low dispersibility (large Abbe number) for the positive lens G32, axial chromatic aberration is corrected more satisfactorily. Further, both sides of the positive lens G31 and the positive lens G34 have an aspherical shape. This is because the aspherical surface is appropriately arranged in the third lens group L3 in which the axial luminous flux that determines the FNO (F number) spreads, and the spherical aberration that tends to increase due to the increase in aperture is satisfactorily corrected.

The negative lens G36 uses a material having a relatively high dispersibility, and corrects chromatic aberration of magnification in the under direction, which tends to overshoot the d line at near infrared wavelengths. The aperture stop SP is installed on the object side of the third lens group L3 and is moved together with the third lens group L3 during zooming.

The zoom lens of the second embodiment has a first lens group L1 having a negative refractive power, a second lens group L2 having a negative refractive power, an aperture aperture SP, and a third lens group having a positive refractive power arranged in order from the object side to the image side. It is composed of a lens group L3 and a fourth lens group L4 having a negative refractive power. When focusing from infinity to a short distance, the fourth lens group L4 moves to the image side. The second lens group L2 and the third lens group L3 correspond to the intermediate group LM. The fourth lens group L4 corresponds to the rear group LR and the lens group Lp. The first lens group L1 and the second lens group L2 correspond to the front lens group. The third lens group L3 and the fourth lens group L4 correspond to the rear lens group.

The first lens group L1 is composed of a meniscus-shaped negative lens G11 having a convex surface on the object side, a negative lens G12 having a biconcave shape, a meniscus-shaped positive lens G13 having a convex surface on the object side, and a positive lens G14 having a biconvex shape.

The second lens group L2 is formed by a negative lens G21 having a meniscus shape whose image side is convex. The third lens group L3 is composed of a biconvex positive lens G31, a biconvex positive lens G32, a biconcave negative lens G33, and a biconvex positive lens G34. The negative lens G32 and the positive lens G33 are made of a bonded lens. Further, both sides of the positive lens G31 and the positive lens G34 have an aspherical shape.

The fourth lens group L4 is formed by a positive lens G41 having a meniscus shape whose object side is convex. The aperture stop SP is installed on the most object side of the third lens group L3, and is moved together with the third lens group L3 during zooming. With the above lens configuration, the same effect as in Example 1 is obtained.

The zoom lenses of Examples 3 and 4 have a first lens group L1 having a negative refractive power, an aperture aperture SP, a second lens group L2 having a positive refractive power, and a negative refractive power arranged in order from the object side to the image side. It is composed of a third lens group L3. When focusing from infinity to a short distance, the third lens group L3 moves to the image side.

The second lens group L2 corresponds to the intermediate group LM and the lens group Lp. The third lens group L3 corresponds to the rear group LR. The first lens group L1 corresponds to the front lens group. The second lens group L2 and the third lens group L3 correspond to the rear lens group.

In the third embodiment, the first lens group L1 has a negative lens G11 having a convex meniscus shape on the object side, a negative lens G12 having a biconcave shape, a positive lens G13 having a convex meniscus shape on the object side, and a positive meniscus shape having a convex surface on the object side. It is made up of a lens G14. The second lens group L2 is composed of a biconvex positive lens G21, a biconvex positive lens G22, a biconcave negative lens G23, and a biconvex positive lens G24. Further, both sides of the positive lens G21 and the positive lens G24 have an aspherical shape.

The third lens group L3 is formed by a positive lens G31 having a meniscus shape whose object side is convex. The aperture stop SP is installed on the most object side of the second lens group L2 and is immobile during zooming.

In the fourth embodiment, the first lens group L1 is composed of a meniscus-shaped negative lens G11 having a convex surface on the object side, a negative lens G12 having a biconcave shape, a positive lens G13 having a biconvex shape, and a meniscus-shaped positive lens G14 having a convex surface on the object side. It is made up.

The second lens group L2 is composed of a biconvex positive lens G21, a biconvex positive lens G22, a biconcave negative lens G23, and a biconvex positive lens G24. Further, both sides of the positive lens G21 and the positive lens G24 have an aspherical shape. The third lens group L3 is formed by a positive lens G31 having a meniscus shape whose object side is convex. The aperture stop SP is installed on the most object side of the second lens group L2 and is immobile during zooming.

In each embodiment, the aperture stop SP is moved or fixed in zooming. It should be noted that the aperture diaphragm SP may be configured to move independently of other lens groups, which makes it easier to properly cut flare rays at each zoom position in zooming.

Next, an embodiment when the zoom lens of each embodiment is used as a surveillance camera (imaging device) will be described with reference to FIG. In FIG. 9, 15 is a dome cover, and 16 is a zoom lens according to the present invention. The dome cover 15 is formed of a plastic material such as polymethylmethacrylate (PMMA) or polycarbonate (PC) to a thickness of about several millimeters. As a result, when the image pickup device is premised on having a dome cover 15, the design may be made in consideration of the influence of the dome cover 15 (focal length and material) and various aberrations may be corrected.

Next, 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. 10, 11 is a surveillance camera main body, and 12 is an image pickup element (photoelectric conversion element) such as a CCD sensor or CMOS sensor that is built in the camera main body 11 and receives a subject image formed by the zoom lens 15.

Reference numeral 13 is a memory unit for recording information corresponding to the subject image photoelectrically converted by the image pickup device 12. Reference numeral 14 is a network cable for transferring the subject image photoelectrically converted by the image pickup device 12. The image pickup device is not limited to the surveillance camera, but can also be used in a video camera, a digital camera, or the like.

As described above, according to each embodiment, the zoom has high optical performance in which various aberrations such as chromatic aberration of magnification are satisfactorily corrected in the visible region to the near infrared region while realizing a wide angle of view while being compact. A lens and an image pickup device having the lens can be obtained. In each embodiment, the following means configuration may be adopted.

-The shape of the lens and the number of lenses shown in the examples are not limited, and may be changed as appropriate.
-Move some lenses and lens groups in a direction that has a component in the direction perpendicular to the optical axis, thereby correcting image blur caused by vibration such as camera shake.
-Correct distortion and chromatic aberration by electrical correction means.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments and optical specifications (angle of view and Fno), and various modifications can be made within the scope of the gist thereof.

Next, the numerical data of the examples corresponding to each embodiment are shown. In the numerical data of each embodiment, the surface number i indicates the order of the 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 + 1th plane spacing. ndi and νdi indicate the refractive index and Abbe number of the material of the optical member with respect to the d line, respectively. The partial dispersion ratio θCt is a numerical value calculated by (nC-nt) / (nF-nC). * Means an aspherical surface.

The back focus (BF) is an air conversion distance from the final surface of the lens to the paraxial image plane. The total length of the lens is defined as the value obtained by adding the back focus (BF) to the distance from the frontmost surface of the lens to the final surface of the lens. When K is the eccentricity factor, A4, A6, A8, A10, and A12 are the aspherical surface coefficients, and the displacement in the optical axis direction at the position of the height H from the optical axis is x with respect to the surface apex, the aspherical surface is aspherical. The shape is

で表示される。但しＲは曲率半径である。また例えば「e－Ｚ」の表示は「１０^－Ｚ」を意味する。また、各実施例における上述した条件式との対応を表１に示す。半画角（度）に関しては、歪曲量を考慮した撮影可能画角に関する数値である。

It is displayed in. However, R is the radius of curvature. Further, for example, the display of "eZ" means "10- ^Z ". Table 1 shows the correspondence with the above-mentioned conditional expressions in each embodiment. The half angle of view (degree) is a numerical value relating to the shootable angle of view in consideration of the amount of distortion.

[Numerical data 1]
Surface data
Surface number rd nd νd θCt
1 31.1 1.3 1.71300 53.9 0.824
2 13.785 9.11
3 -76.899 1.1 1.59522 67.7 0.795
4 23.073 4.46
5 -40.92 0.8 1.60311 60.6 0.832
6 -207.171 0.2
7 31.193 2.87 1.95906 17.5 0.626
8 123.794 (variable)
9 -12.304 0.5 1.49700 81.5 0.826
10 -251.222 (variable)
11 (Aperture) ∞ 0.4
12 * 10.596 3.77 1.55332 71.7 0.816
13 * -117.861 0.17
14 18.705 5 1.43700 95.1 0.843
15 -8.802 0.45 1.91082 35.3 0.713
16 50.28 0.48
17 * 10.384 4.75 1.55332 71.7 0.816
18 * -14.095 1.54
19 -53.218 2.04 1.94595 18 0.632
20 -20.511 3.32
21 -9.979 0.5 1.71736 29.5 0.691
22 -57.455 (variable)
23 ∞ 2 1.54400 60
Image plane ∞ 2.38

Aspherical data
12th page
K = 0.00000e + 000 A 4 = -5.76120e-005 A 6 = 1.17397e-006
A 8 = -2.32279e-009 A10 = 9.24800e-011
Page 13
K = 0.00000e + 000 A 4 = -1.03220e-004 A 6 = 2.75895e-006
A 8 = -1.16921e-008 A10 = -1.97440e-010
Page 17
K = 0.00000e + 000 A 4 = -3.98840e-004 A 6 = 5.53134e-006
A 8 = -5.82520e-008 A10 = 3.53103e-010
Page 18
K = 0.00000e + 000 A 4 = 1.45694e-004 A 6 = 1.02875e-006
A 8 = 2.09863e-008 A10 = 1.62555e-011

Various data
Zoom ratio 2.9
Wide-angle intermediate telephoto
Focal length 5.00 9.62 14.55
F number 1.67 2.32 2.97
Half angle of view (degrees) 71.90 33.20 21.70
Image height 5.50 5.50 5.50
Lens total length 70.00 65.24 66.27
BF (in air) 6.18 12.36 18.53

d 8 8.75 4.85 2.14
d10 11.60 4.57 2.13
d22 2.50 8.68 14.85

Focal length of each group
Group focal length
1 -19.5
2 -26.05
3 11.37

Single lens data
Lens focal length
1 -35.85
2-29.70
3 -84.70
4 42.83
5 -26.05
6 17.76
7 14.50
8 -8.19
9 11.61
10 34.24
11 -16.91

[Numerical data 2]
Surface data
Surface number rd nd νd θCt
1 18.496 0.9 1.88300 40.8 0.740
2 7.973 6.73
3 -27.006 0.6 1.69560 59 0.822
4 13.706 0.96
5 12.818 1.77 1.85478 24.8 0.674
6 20.233 0.98
7 141.349 1.9 1.80809 22.8 0.660
8-39.218 (variable)
9 -9.267 1.5 1.51823 58.9 0.819
10 -23.31 (variable)
11 (Aperture) ∞ 0.3
12 * 9.478 3.53 1.55332 71.7 0.816
13 * -258.326 0.17
14 13.708 3.86 1.43700 95.1 0.843
15 -17.129 0.45 1.69895 30.1 0.697
16 15.507 0.15
17 * 7.102 4.33 1.55332 71.7 0.816
18 * -9.173 (variable)
19 8.799 0.41 1.72151 29.2 0.690
20 5.136 (variable)
21 ∞ 2 1.51633 64.1
Image plane ∞ 1.43

Aspherical data
12th page
K = 0.00000e + 000 A 4 = -1.87419e-004 A 6 = 1.89535e-006
A 8 = 1.10399e-008 A10 = -1.57720e-009 A12 = 4.37354e-011
Page 13
K = 0.00000e + 000 A 4 = -3.30143e-004 A 6 = 1.41244e-005
A 8 = -2.54797e-007 A10 = 3.94749e-009
Page 17
K = 0.00000e + 000 A 4 = -1.30430e-003 A 6 = 2.76606e-006
A 8 = -1.39933e-007 A10 = -3.24081e-009
Page 18
K = 0.00000e + 000 A 4 = 4.33650e-004 A 6 = -1.50558e-005
A 8 = 3.68739e-007 A10 = -5.84152e-009 A12 = -8.37516e-021

Various data
Zoom ratio 2.3
Wide-angle intermediate telephoto
Focal length 2.60 4.11 6.00
F number 1.28 1.43 1.64
Half angle of view (degrees) 77.20 41.90 28.30
Image height 3.04 3.04 3.04
Lens total length 53.23 45.58 40.52
BF (in air) 5.25 5.00 6.32

d 8 2.08 5.33 0.69
d10 15.78 3.17 1.04
d18 0.90 2.86 3.26
d20 2.50 2.25 3.56

Focal length of each group
Group focal length
1 -12.07
2 -30.81
3 8.57
4 -17.95

Single lens data
Lens focal length
1 -16.54
2 -12.99
3 36.87
4 38.17
5 -30.81
6 16.60
7 18.11
8 -11.58
9 7.99
10 -17.95

[Numerical data 3]
Surface data
Surface number rd nd νd θCt
1 27.872 1.35 1.90043 37.4 0.722
2 13.037 11.61
3 -36.962 1.05 1.90043 37.4 0.722
4 18.754 1.59
5 31.084 3.2 1.92286 18.9 0.637
6 70.018 0.99
7 30.941 4.59 1.85478 24.8 0.674
8 109.067 (variable)
9 (Aperture) ∞ (Variable)
10 * 13.72 5.57 1.55332 71.7 0.816
11 * -117.438 0.26
12 32.832 5.68 1.43700 95.1 0.843
13 -18.656 0.45
14 -17.27 0.75 1.73800 32.3 0.715
15 72.111 0.75
16 * 17.496 5.11 1.55332 71.7 0.816
17 * -13.309 (variable)
18 15.756 0.68 1.80809 22.8 0.660
19 8.094 (variable)
20 ∞ 2 1.51633 64.1
Image plane ∞ 2.18

Aspherical data
Page 10
K = 0.00000e + 000 A 4 = -3.96745e-005 A 6 = 2.63499e-007
A 8 = -1.12658e-009 A10 = 1.78443e-011 A12 = 2.05813e-021
Page 11
K = 0.00000e + 000 A 4 = -2.02684e-005 A 6 = 9.94170e-007
A 8 = -4.60023e-009 A10 = 3.74053e-011
16th page
K = 0.00000e + 000 A 4 = -2.88302e-004 A 6 = -1.39776e-006
A 8 = 3.45138e-008 A10 = -7.62529e-010
Page 17
K = 0.00000e + 000 A 4 = 3.03245e-005 A 6 = -1.01871e-006
A 8 = 7.73736e-009 A10 = -2.72249e-010

Various data
Zoom ratio 2.6
Wide-angle intermediate telephoto
Focal length 3.82 6.82 9.90
F number 1.35 1.90 2.40
Half angle of view (degrees) 78.10 37.40 25.30
Image height 4.50 4.50 4.50
Lens total length 99.26 73.08 64.26
BF (in air) 8.46 9.04 9.69

d 8 39.17 12.98 4.17
d 9 6.00 3.50 1.00
d17 1.35 3.26 5.12
d19 4.96 5.55 6.19

Focal length of each group
Group focal length
1 -13.22
2 14.05
3-21.44

Single lens data
Lens focal length
1 -28.43
2 -13.69
3 58.28
4 49.20
5 22.54
6 28.17
7 -18.81
8 14.52
9 -21.44

[Numerical data 4]
Surface data
Surface number rd nd νd θCt
1 23.237 0.9 1.90043 37.4 0.722
2 9.034 6.95
3 -21.122 0.7 1.91082 35.3 0.713
4 14.83 1.1
5 29.738 4.46 1.95906 17.5 0.626
6 -764.966 0.15
7 20.627 2.55 1.85478 24.8 0.674
8 38.636 (variable)
9 (Aperture) ∞ (Variable)
10 * 9.687 3.36 1.55332 71.7 0.816
11 * -275.427 0.17
12 18.553 4.2 1.43700 95.1 0.843
13 -12.459 0.54
14 -11.316 0.5 1.73800 32.3 0.715
15 38.757 0.54
16 * 11.645 3.6 1.55332 71.7 0.816
17 * -8.871 (variable)
18 6.583 0.5 1.89286 20.4 0.646
19 4.504 2.5
20 ∞ 2 1.51633 64.1
Image plane ∞ 1.88

Aspherical data
Page 10
K = 0.00000e + 000 A 4 = -1.01331e-004 A 6 = 2.34520e-006
A 8 = -2.70658e-008 A10 = 9.38847e-010 A12 = 1.78026e-019
Page 11
K = 0.00000e + 000 A 4 = -2.07516e-005 A 6 = 6.69887e-006
A 8 = -7.24485e-008 A10 = 1.84979e-009
16th page
K = 0.00000e + 000 A 4 = -8.90032e-004 A 6 = -1.0844e-006
A 8 = 4.36888e-008 A10 = -1.07330e-008
Page 17
K = 0.00000e + 000 A 4 = 1.02345e-004 A 6 = -3.17024e-006
A 8 = -4.70198e-008 A10 = -3.84119e-009

Various data
Zoom ratio 2.3
Wide-angle intermediate telephoto
Focal length 2.59 4.28 5.97
F number 1.24 1.45 1.68
Half angle of view (degrees) 77.20 40.20 28.20
Image height 3.04 3.04 3.04
Lens total length 65.98 50.37 44.45
BF (in air) 5.70 5.70 5.70

d 8 24.93 9.32 3.40
d 9 3.54 2.04 0.54
d17 0.90 2.40 3.90

Focal length of each group
Group focal length
1 -8.78
2 9.98
3 -18.03

Single lens data
Lens focal length
1 -16.92
2 -9.48
3 29.93
4 48.6
5 16.98
6 17.79
7 -11.82
8 9.71
9 -18.03

L0 Zoom lens LM Intermediate group LR Final lens group nr Lens element L1 1st lens group L2 2nd lens group L3 3rd lens group L4 4th lens group

Claims (17)

It has an aperture diaphragm and a plurality of lens groups, and the plurality of lens groups are a first lens group having a negative refractive power arranged in order from the object side to the image side, and an intermediate group including one or more lens groups. A zoom lens that consists of a rear lens group and changes the distance between adjacent lens groups during zooming.
The first lens group has two or more negative lenses and one or more positive lenses.
The rear lens group has a lens element nr having a negative refractive power arranged on the image side most.
When the Abbe number and the partial dispersion ratio of the material of the lens element nr are νdnr and θCtnr, respectively,
20.4 ≤ νdnr ≤ 29.5
0.45 <θCtnr <0.78
Including a negative lens that satisfies the conditional expression
The aperture diaphragm is arranged on the image side of the first lens group, and includes a lens group LP having a positive refractive force arranged adjacent to the image side of the aperture diaphragm, and the lens group LP is telescopic from the wide-angle end. Moving to the object side when zooming to the edge, the lens group Lp has a plurality of positive lenses, and the largest Abbe number among the Abbe numbers of the plurality of positive lenses is νpdp1, and the second largest Abbe number is νpdp2. and when,
75 <(νdp1 + νpd2) / 2 <96
Satisfy the conditional expression
When the refractive indexes of the material at the d-line, C-line, t-line, and F-line are nd, nC, nt, and nF, respectively, the partial dispersion ratio is represented by (nC-nt) / (nF-nC). A zoom lens that features that. It has an aperture diaphragm and a plurality of lens groups, and the plurality of lens groups are a first lens group having a negative refractive power arranged in order from the object side to the image side, and an intermediate group including one or more lens groups. A zoom lens that consists of a rear lens group and changes the distance between adjacent lens groups during zooming.
The first lens group has two or more negative lenses and one or more positive lenses.
The rear lens group has a lens element nr having a negative refractive power arranged on the image side most.
When the Abbe number and the partial dispersion ratio of the material of the lens element nr are νdnr and θCtnr, respectively,
20.4 ≤ νdnr ≤ 29.5
0.45 <θCtnr <0.78
Including a negative lens that satisfies the conditional expression
The intermediate group is composed of a second lens group having a negative refractive power, and the rear group is composed of a third lens group having a positive refractive power.
When the refractive indexes of the material at the d-line, C-line, t-line, and F-line are nd, nC, nt, and nF, respectively, the partial dispersion ratio is represented by (nC-nt) / (nF-nC). A zoom lens that features that. It has an aperture diaphragm and a plurality of lens groups, and the plurality of lens groups are a first lens group having a negative refractive power arranged in order from the object side to the image side, and an intermediate group including one or more lens groups. A zoom lens that consists of a rear lens group and changes the distance between adjacent lens groups during zooming.
The first lens group has two or more negative lenses and one or more positive lenses.
The rear lens group has a lens element nr having a negative refractive power arranged on the image side most.
When the Abbe number and the partial dispersion ratio of the material of the lens element nr are νdnr and θCtnr, respectively,
20.4 ≤ νdnr ≤ 29.5
0.45 <θCtnr <0.78
Including a negative lens that satisfies the conditional expression
The intermediate group is composed of a second lens group having a negative refractive power and a third lens group having a positive refractive power arranged in order from the object side to the image side, and the rear group is a fourth lens group having a negative refractive power. Consists of
When the refractive indexes of the material at the d-line, C-line, t-line, and F-line are nd, nC, nt, and nF, respectively, the partial dispersion ratio is represented by (nC-nt) / (nF-nC). A zoom lens that features that. It has an aperture diaphragm and a plurality of lens groups, and the plurality of lens groups are a first lens group having a negative refractive power arranged in order from the object side to the image side, and an intermediate group including one or more lens groups. A zoom lens that consists of a rear lens group and changes the distance between adjacent lens groups during zooming.
The first lens group has two or more negative lenses and one or more positive lenses.
The rear lens group has a lens element nr having a negative refractive power arranged on the image side most.
When the Abbe number and the partial dispersion ratio of the material of the lens element nr are νdnr and θCtnr, respectively,
20.4 ≤ νdnr ≤ 29.5
0.45 <θCtnr <0.78
Including a negative lens that satisfies the conditional expression
The intermediate group is composed of a second lens group having a positive refractive power, and the rear group is composed of a third lens group having a negative refractive power.
When the refractive indexes of the material at the d-line, C-line, t-line, and F-line are nd, nC, nt, and nF, respectively, the partial dispersion ratio is represented by (nC-nt) / (nF-nC). A zoom lens that features that. When the focal length of the first lens group is f1 and the focal length of the entire system at the wide-angle end is fw,
-6.0 <f1 / fw <-2.0
The zoom lens according to any one of claims 1 to 4, wherein the zoom lens satisfies the conditional expression. The aperture diaphragm is arranged on the image side of the first lens group, and has a lens group LP having a positive refractive force arranged adjacent to the image side of the aperture diaphragm, and the lens group LP has a wide angle. When moving to the object side during zooming from the end to the telephoto end, the focal length of the lens group LP is fp, and the focal length of the zoom lens at the wide-angle end is fw.
1.5 <fp / fw <5.0
The zoom lens according to any one of claims 1 to 5, wherein the zoom lens satisfies the conditional expression. When the focal length of the rear lens group is fn and the focal length of the lens element nr is fnr,
0.50 << | fnr / fn | <3.0
The zoom lens according to any one of claims 1 to 6 , wherein the zoom lens satisfies the conditional expression. In the first lens group, when the Abbe number and the refractive index of the material are νd1p and Nd1p, respectively,
12 <νd1p <28
1.75 <Nd1p <2.20
The zoom lens according to any one of claims 1 to 7 , further comprising a positive lens satisfying the conditional expression. The aperture diaphragm is arranged on the image side of the first lens group, and all the lens groups located on the object side of the aperture diaphragm are the front group, and all the lens groups located on the image side of the aperture diaphragm are the rear group. When the focal length of the front group at the wide-angle end is fAw and the focal length of the rear group at the wide-angle end is fBw,
-1.2 <fAw / fBw <-0.40
The zoom lens according to any one of claims 1 to 8 , wherein the zoom lens satisfies the conditional expression. The aperture diaphragm is arranged on the image side of the first lens group, and includes a lens group LP having a positive refractive force arranged adjacent to the image side of the aperture diaphragm, and the lens group LP is telescopic from the wide-angle end. Moving to the object side when zooming to the edge, the lens group Lp has a plurality of positive lenses, and the largest Abbe number among the Abbe numbers of the plurality of positive lenses is νpdp1, and the second largest Abbe number is νpdp2. and when,
75 <(νdp1 + νpd2) / 2 <96
The zoom lens according to any one of claims 2 to 9 , wherein the zoom lens satisfies the conditional expression. The zoom lens according to claim 1 , wherein the intermediate group is composed of a second lens group having a negative refractive power, and the rear group is composed of a third lens group having a positive refractive power. The zoom lens according to claim 2 or 11 , wherein the second lens group moves toward an object when focusing from infinity to a short distance. The intermediate group is composed of a second lens group having a negative refractive power and a third lens group having a positive refractive power arranged in order from the object side to the image side, and the rear group is a fourth lens group having a negative refractive power. The zoom lens according to claim 1 , further comprising: The zoom lens according to claim 3 or 13 , wherein the fourth lens group moves toward the image side when focusing from infinity to a short distance. The zoom lens according to claim 1 , wherein the intermediate group is composed of a second lens group having a positive refractive power, and the rear group is composed of a third lens group having a negative refractive power. The zoom lens according to claim 4 or 15 , wherein the third lens group moves toward the image side when focusing from infinity to a short distance. An image pickup apparatus comprising the zoom lens according to any one of claims 1 to 16 and an image pickup element that receives an image formed by the zoom lens.

Images