JP2019061005A - Zoom lens and imaging device including the same - Google Patents

Abstract

To provide a zoom lens that is compact in size of an entire lens system, has a wide angle of view, and easily achieves high optical performance.SOLUTION: A zoom lens includes, disposed in order from an object side to an image side, a first lens group with negative refractive power, an intermediate group including one or more lens groups, and a rear group, and the interval between adjacent lens groups varies during zooming. The first lens group includes two or more negative lenses and one or more positive lenses and the rear group includes a lens element nr with negative refractive power at a position nearest to the image side. Assuming that refractive indexes at the d line, C line, t line, and F line of material are nd, nC, nt, and nF, respectively, the Abbe number νd and partial dispersion ratio θct of the material, and the Abbe number and partial dispersion ratio νdnr and θCtnr of material of the lens element nr are each appropriately set.SELECTED DRAWING: Figure 1

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.

  A zoom lens used for an imaging device is required to have high optical performance that can cope with high definition of an imaging element and to have a wide angle of view. Moreover, imaging devices, such as a surveillance camera, use visible light for daytime imaging, and use 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, it is desirable that the zoom lens used in the surveillance camera be a zoom lens in which various aberrations are favorably corrected in a wide wavelength range from visible light (about 400 nm to about 700 nm) to the near infrared region. It is done.

  Conventionally, as a zoom lens, there is known a negative lead type zoom lens in which a lens unit of negative refractive power is disposed closest to the object side (Patent Documents 1 and 2).

  In Patent Document 1, a three-unit zoom lens configured of, in order from the object side to the image side, first to third lens units having negative, positive, and negative refractive power, and the distance between adjacent lens units changes during zooming. Is disclosed. In Patent Document 2, a fourth lens unit is configured of first to fourth lens units of negative, negative, positive, and negative refractive power in order from the object side to the image side, and the distance between adjacent lens groups changes during zooming A zoom lens is disclosed.

  In addition to this, there is known a zoom lens which is a negative lead type and is well corrected for aberration over a wide wavelength range from visible light to near-infrared range (Patent Document 3). In Patent Document 3, a three-unit zoom lens configured of, in order from the object side to the image side, first to third lens units having negative, positive, and negative refractive power, and the distance between adjacent lens units changes during zooming. Is disclosed.

JP 2007-233045 A JP, 2014-219543, A JP, 2016-145928, A

  In the negative lead type 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 area while the entire system is compact and has a wide angle of view. Come. For example, in a zoom lens used for a surveillance camera, it is important to have high optical performance with chromatic aberration well corrected among various aberrations over a wide wavelength range from the visible region to the near infrared region.

  In the negative lead type zoom lens, in order to properly correct magnification chromatic aberration in a wide wavelength range and obtain high optical performance, the lens configuration of the first lens unit and the lens material used for the lens unit disposed closest to the image It is important to set the etc properly. 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, an intermediate group including one or more lens groups, and a rear group disposed in order from the object side to the image side, and lenses adjacent to each other during zooming A zoom lens in which the distance between groups changes
The first lens group has two or more negative lenses and one or more positive lenses, and the rear group has a lens element nr of negative refractive power on the most image side, and the d-line of the material, C Let the refractive index at the line, t line and F line be nd, nC, nt and nF, respectively, and the Abbe number dd of the material and the partial dispersion ratio θct, respectively
d d = (nd-1) / (nF-nC)
θCt = (nC−nt) / (nF−nC)
Assuming that 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
0.45 <θCtnr <0.78
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 middle 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 middle 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 middle 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 middle zoom position, and at the telephoto end according to Example 4. Lens sectional view in surveillance camera (imaging device) of the present invention Outline of essential parts of the surveillance camera of the present invention (A), (B) explanatory drawing of glass characteristics (brand name S-NPH1, brand name S-LAH 53) Explanatory drawing about the optical path in the wide-angle end and the telephoto end of Example 1

  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 is composed of a first lens group of 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 lenses adjacent to each other during zooming The spacing of the groups changes.

  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 2.90 and an f-number of 1.67 to 2.97. 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 2.3 and an f-number of 1.28 to 1.64.

  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 2.6 and an f-number of 1.35 to 2.40.

  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 2.3 and an f-number of 1.24 to 1.68.

  FIG. 9 is a lens sectional view when the zoom lens of the present invention is accommodated in a dome. 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. FIGS. 11A and 11B are explanatory diagrams of the characteristics of the material (optical material) used for the zoom lens of the present invention. 12A and 12B are optical path diagrams at the wide-angle end and the telephoto end of the zoom lens according to the first embodiment.

  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, L0 is a zoom lens.

  LM is an intermediate group having one or more lens groups. LR is a rear group located closest to the image side. Li is an ith lens group. L1 is a first lens group of negative refractive power (optical power = reciprocal of focal length). 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. Lp is a lens group of positive refractive power disposed adjacent to the image side of the aperture stop SP.

  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 Fa relating to focusing indicates a movement locus of the lens group during zooming from the wide-angle end to the telephoto end when focusing at infinity. An arrow Fb indicates the movement locus of the lens unit during zooming from the wide-angle end to the telephoto end when focusing at a short distance. An arrow Fc indicates the moving direction of the lens unit during focusing from infinity to near distance.

  An arrow F relating to focusing in FIG. 7 indicates the moving direction at the time of focusing from infinity to near distance.

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

  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 achieving downsizing of the entire system, a lens configuration suitable for performing zooming by changing the distance between the lens units is provided. Further, in order to achieve wide angle of view at the wide angle end, a negative lead type is adopted because the lens unit closest to the object side has negative refractive power. In order to give the first lens group a strong negative refracting power, a lens configuration having many negative lenses is adopted.

  Moreover, in order to correct | amend magnification chromatic aberration favorably not only in a visible region but also to a near infrared region, the lens structure which consists of materials different from before is taken. This will be described with reference to FIGS. 11A, 11 B, and 12.

  In the zoom lens according to the present invention, a lens element (lens element) nr of negative refractive power is provided most on the image side, and the lens element nr has a relatively large difference in refractive index in the near infrared region with respect to the visible region. It has a feature (which increases the 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 in visible light.

  The reason is that near-infrared light forms an image on the visible side in the over side (positive direction in the magnification chromatic aberration diagram) in the entire lens system. Therefore, in order to correct this, it is preferable that the lens element nr have a dispersibility that reduces the refractive index of near infrared light. Therefore, it is better to select a material that increases the dispersion of t-line (wavelength 1013.98 nm) with reference to d-line (wavelength 587.6 nm). Specifically, select a material that reduces the Abbe number νd. good.

  With regard to the partial dispersion ratio θct, it is preferable to select a material that becomes smaller as shown in a general characteristic (from the Ohara Inc. issuance map in FIG. 11B) that changes according to the Abbe number νd. FIG. 11B shows the Abbe number dd and the partial dispersion ratio θct.

  Next, FIG. 11A is used, and two types (trade name S-NPH1 and trade name S-LAH53) of OHARA Co., Ltd. are taken as an example as glass materials having different dispersiveness and refractive index of the d-line. I will explain the principle.

  FIG. 11A shows the change of the refractive index at each wavelength. The table shows the refractive index 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 dd and the partial dispersion ratio θCt are shown.

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

  In general, in the case of imaging using only 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 of about 1000 nm wavelength, the above principle is used I get the effect. The lens element nr having a negative refractive power closest to the image plane has the above characteristics at each image height from the wide-angle end to the telephoto end, as shown in FIGS. 12 (A) and 12 (B). A difference hardly occurs in the passing optical path area of the lens element nr. Therefore, it is to efficiently correct the magnification chromatic aberration in the entire zoom range.

  Here, the lens element nr of negative refractive power closest to the image side means an element having a negative refractive power as a whole by a single lens or a cemented lens.

  The present invention is a compact zoom lens having a wide angle of view, which has a small size but has high optical performance over the entire zoom range, and in particular, has little lateral chromatic aberration in a wide wavelength range from visible light to near infrared light. is there. The zoom lens according to the present invention includes a first lens unit L1 of negative refractive power, an intermediate unit LM including one or more lens units, and a rear unit LR, which are disposed in order from the object side to the image side.

  The first lens unit L1 has two or more negative lenses and one or more positive lenses, and the rear unit LR has a lens element nr of negative refractive power on the most image side. Let the refractive indices at d-line, C-line, t-line and F-line of the material be nd, nC, nt and nF respectively. 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)
far. Then, when the Abbe number and the partial dispersion ratio of the material of the lens element nr are respectively ddnr and θCtnr,

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

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

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

The conditional expressions (1) and (2) are more preferably limited 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 unit 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 unit LP of positive refractive power adjacent to the image side of the aperture stop SP. The lens unit LP moves to the object side during zooming from the wide-angle end to the telephoto end, and the focal length of the lens unit LP is fp. The focal length of the rear group LR is fn, and the focal length of the lens element nr is fnr.

  The Abbe number of the material of the positive lens included in the first lens group L1 is dd1p, and the refractive index of the material of the positive lens included in the first lens group L1 is Nd1p. All lens units positioned on the object side of the aperture stop SP are referred to as a front lens unit, and all lens units positioned on the image side of the aperture stop SP are referred to as a rear lens unit. The focal length of the front lens unit at the wide angle end is fAw, and the focal length of the rear lens unit at the wide angle end is fBw.

  The lens unit Lp has a plurality of positive lenses, and among the Abbe numbers of the materials of the plurality of positive lenses, the largest Abbe number is dpdp1, and the largest Abbe number is νdp2. 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 + νdp2) / 2 <96.0 (9)

  Next, technical meanings of the above-mentioned conditional expressions will be described. Condition (3) is intended to achieve a wide angle of view while achieving downsizing of the entire system. If the upper limit value of conditional expression (3) is exceeded, the negative refractive power of the first lens unit L1 becomes too strong (the absolute value of the negative refractive power becomes too large), and the field curvature or the field curvature over the entire zoom range Correction of lateral chromatic aberration becomes difficult. If the lower limit value of the conditional expression (3) is exceeded, the negative refractive power of the first lens unit L1 becomes too weak (the absolute value of the negative refractive power becomes too small), making it difficult to achieve a wide angle of view. Become.

  Furthermore, the amount of movement of the first lens unit L1 during zooming increases, the total lens length increases, and the effective diameter of the front lens increases, making it difficult to miniaturize the entire system.

  Conditional expression (4) appropriately sets the relationship between the focal length of the entire system at the wide-angle end and the refractive power of the lens unit Lp, which is a lens unit for zooming, to achieve downsizing of the entire system and the zoom range. It is for obtaining high optical performance. If the upper limit of conditional expression (4) is exceeded, the positive refractive power of the lens unit Lp will be too weak, and the amount of movement of the lens unit Lp during zooming will increase, making it difficult to miniaturize the entire system.

  If the lower limit of the conditional expression (4) is exceeded, the positive refractive power of the lens unit Lp becomes too strong, and it becomes difficult to correct spherical aberration when increasing the aperture (when FNO is reduced). The aperture stop SP is placed at the object side position of the magnification varying lens group in order to make it easy to control the axial light flux (FNO) without the off-axis light flux being kicked.

  Condition (5) relates to the negative refracting power of the lens element nr of negative refracting power located closest to the image side. Since the lens element nr is located closest to the image side, it is necessary to bounce the light beam in order to secure a desired image height, and the conditional expression (5) defines its refracting power.

  If the upper limit of conditional expression (5) is exceeded, the refractive power of the rear unit LR becomes too weak, and therefore it is necessary to increase the lens thickness and the lens diameter. This makes it difficult to miniaturize the entire system. If the lower limit of the conditional expression (5) is exceeded, the refractive power of the rear unit LR becomes too strong, so the jump of the light beam becomes rapid and the incident angle of the light beam to the imaging device becomes too large. As a result, it becomes difficult to secure a sufficient amount of light at the outermost peripheral image height, and the optical performance is degraded.

  Conditional expressions (6) and (7) define the characteristics of the material of the positive lens included in the first lens unit L1. Conditional expression (6) relates to the correction of the chromatic aberration, and is for correcting the chromatic aberration generated from the negative lens included in the first lens unit L1. If the upper limit of conditional expression (6) is exceeded, correction of lateral chromatic aberration will be insufficient. If the lower limit of the conditional expression (6) is exceeded, the amount of correction of chromatic aberration of magnification becomes too large to be reduced in the reverse direction, and the optical performance is reduced.

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

  Condition (8) relates to the refractive power arrangement for achieving wide angle of view. Each embodiment has a lens configuration including three or more lens groups, and adopts a retrofocus type suitable for wide angle of view, and a front lens group having negative refractive power on the object side with respect to the aperture stop SP. On the image side, it consists of a rear lens group of positive refractive power. In order to achieve a wide angle, it is necessary to make the negative refractive power of the front lens unit strong.

  If the upper limit of conditional expression (8) is exceeded, the negative refractive power of the front lens unit becomes too strong, and it becomes difficult to correct field curvature and chromatic aberration in the entire zoom range. If the lower limit of conditional expression (8) is exceeded, the negative refractive power of the first lens unit L1 will be too weak, making it difficult to achieve a wide angle of view. Furthermore, the amount of movement of the first lens unit L1 increases during zooming, the overall lens length increases, and the effective diameter of the front lens increases, making it difficult to miniaturize the entire system.

  Condition (9) relates to the material of the positive lens included in the lens unit Lp for correcting longitudinal chromatic aberration. When axial chromatic aberration becomes large, the occurrence of color bleeding and resolution tend to be reduced. Therefore, axial chromatic aberration is effectively corrected by using a material that satisfies the conditional expression (9).

  If the upper limit of the conditional expression (9) is exceeded, a material with an ultra-low dispersion system will be used, which tends to result in a low refractive index as a material generally present. For this reason, it becomes difficult to secure the refractive power as a lens. As a result, it is necessary to take measures such as increasing the lens thickness, making it difficult to miniaturize the entire system. If the lower limit of conditional expression (9) is exceeded, correction of chromatic aberration will be insufficient, which is not good.

More preferably, the numerical ranges of conditional expressions (3) to (9) are set 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 + νdp2) / 2 <90.0 (9a)

  Next, the lens configuration of the zoom lens of each embodiment will be described. The zoom lens according to Example 1 has a first lens unit L1 of negative refractive power, a second lens unit L2 of negative refractive power, an aperture stop SP, and a third lens of positive refractive power, which are disposed in order from the object side to the image side. It comprises the lens unit L3. During focusing from infinity to near distance, the second lens unit L2 moves to the object side.

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

  The first lens unit L1 includes a negative meniscus lens G11 having a convex surface on the object side, a negative biconvex lens G12, a negative meniscus lens G13 having a convex surface on the image side, and a positive meniscus lens G14 having a convex surface on the object side. There is. For the positive lens G14, a material having relatively high dispersion is used to correct magnification chromatic aberration.

  The second lens unit L2 is composed of a negative meniscus lens G21 having a convex surface on the image side. For the negative lens G21, a material having relatively low dispersion is used in order to suppress fluctuation of magnification chromatic aberration due to focusing.

  The third lens unit 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 positive lens G35 having a convex surface on the image side, The image side is composed of a negative meniscus lens G36 having a convex surface. The negative lens G32 and the positive lens G33 are composed of a cemented cemented lens, and correct the chromatic aberration by giving a difference in Abbe number of the material.

  Further, by using a material of low dispersion (large Abbe number) for the positive lens G32, axial chromatic aberration is corrected better. Further, both surfaces of the positive lens G31 and the positive lens G34 are aspheric. In this case, an aspheric surface is appropriately disposed in the third lens unit L3 in which the axial light flux that determines the FNO (F number) spreads, and spherical aberration that easily increases with a large aperture is corrected well.

  The negative lens G36 is made of a material having relatively high dispersion, and corrects the chromatic aberration of magnification that tends to easily go out with respect to the d-line in the near infrared wavelength in the under direction. The aperture stop SP is disposed on the object side of the third lens unit L3, and is moved together with the third lens unit L3 during zooming.

  The zoom lens of Example 2 includes a first lens unit L1 of negative refractive power, a second lens unit L2 of negative refractive power, an aperture stop SP, and a third lens of positive refractive power, which are disposed in order from the object side to the image side. It comprises a lens unit L3 and a fourth lens unit L4 of negative refractive power. During focusing from infinity to near distance, the fourth lens unit L4 moves to the image side. The second lens unit L2 and the third lens unit L3 correspond to the intermediate unit LM. The fourth lens unit L4 corresponds to the rear unit LR and the lens unit Lp. The first lens unit L1 and the second lens unit L2 correspond to the front lens unit. The third lens unit L3 and the fourth lens unit L4 correspond to the rear lens unit.

  The first lens unit L1 is composed of a meniscus negative lens G11 convex on the object side, a biconcave negative lens G12, a meniscus positive lens G13 convex on the object side, and a biconvex positive lens G14.

  The second lens unit L2 is composed of a negative meniscus lens G21 having a convex surface on the image side. The third lens unit L3 is composed of a double convex positive lens G31, a double convex positive lens G32, a double concave negative lens G33, and a double convex positive lens G34. The negative lens G32 and the positive lens G33 are composed of a cemented doublet lens. Further, both surfaces of the positive lens G31 and the positive lens G34 are aspheric.

  The fourth lens unit L4 is composed of a positive meniscus lens G41 having a convex surface on the object side. The aperture stop SP is disposed on the most object side of the third lens unit L3, and is moved together with the third lens unit L3 during zooming. The same lens configuration as in Example 1 is obtained by the above lens configuration.

  The zoom lenses of Examples 3 and 4 have a first lens unit L1 of negative refractive power, an aperture stop SP, a second lens unit L2 of positive refractive power, and a negative lens of L2 arranged in order from the object side to the image side. It comprises the third lens unit L3. During focusing from infinity to near distance, the third lens unit L3 moves to the image side.

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

  In Example 3, the first lens unit L1 is a meniscus negative lens G11 having a convex surface on the object side, a biconcave negative lens G12, a positive meniscus lens G13 having a convex surface on the object side, and a positive meniscus shape having a convex surface on the object side. It consists of a 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 biconvex positive lens G24. Further, both surfaces of the positive lens G21 and the positive lens G24 are aspheric.

  The third lens unit L3 is composed of a positive meniscus lens G31 having a convex surface on the object side. The aperture stop SP is disposed on the most object side of the second lens unit L2, and does not move during zooming.

  In the fourth embodiment, the first lens unit L1 includes a negative meniscus lens G11 having a convex surface on the object side, a negative biconvex lens G12 having a biconcave shape, a positive biconvex lens G13, and a positive meniscus lens G14 having a convex surface on the object side. It consists of.

  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 biconvex positive lens G24. Further, both surfaces of the positive lens G21 and the positive lens G24 are aspheric. The third lens unit L3 is composed of a positive meniscus lens G31 having a convex surface on the object side. The aperture stop SP is disposed on the most object side of the second lens unit L2, and does not move during zooming.

  In each embodiment, the aperture stop SP is moved or fixed in zooming. The aperture stop SP may be moved independently of the other lens units, and it becomes easy to appropriately cut flare light at each zoom position during zooming.

  Next, an embodiment when the zoom lens of each embodiment is used for a surveillance camera (image pickup apparatus) 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 plastic material such as polymethyl methacrylate (PMMA) or polycarbonate (PC) to a thickness of about several millimeters. Thus, when the imaging apparatus is assumed to have the dome cover 15 attached, various aberrations may be corrected by considering the influence of the dome cover 15 (focal length and material).

  Next, a surveillance camera using the zoom lens of the present invention as an imaging optical system will be described using FIG. In FIG. 10, reference numeral 11 denotes a monitoring camera body, and 12 denotes an imaging element (photoelectric conversion element) such as a CCD sensor or a CMOS sensor which is built in the camera body 11 and receives an object image formed by the zoom lens 15.

  A memory unit 13 records information corresponding to the subject image photoelectrically converted by the imaging device 12. Reference numeral 14 denotes a network cable for transferring an object image photoelectrically converted by the imaging device 12. The imaging device is not limited to a surveillance camera, and can be used in a video camera, a digital camera, and the like.

  As described above, according to each embodiment, a zoom having a high optical performance that favorably corrects various aberrations such as lateral chromatic aberration in the visible region to the near infrared region while realizing a wide angle of view while being small. A lens and an imaging device having the same can be obtained. In each embodiment, the following means may be adopted.

-It is not limited to the shape of the lens shown in the embodiment and the number of lenses, and may be changed appropriately.
Moving some lenses and lens groups in a direction having a component in a direction perpendicular to the optical axis, thereby correcting image blurring accompanying vibrations such as camera shake.
· Correct distortion, chromatic aberration, etc. by electrical correction means.

  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 can be made within the scope of the present invention.

  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. The half angle of view (degrees) is a numerical value related to the image capturing available angle of view in which the amount of distortion is taken into consideration.

[Numeric data 1]
Surface data
Face number rd nd dd θCt
1 31.1 1.3 1.7 1300 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 2 1.54400 60
Image plane ∞ 2.38

Aspheric data
12th
K = 0.00000e + 000A 4 = -5.76120e-005 A 6 = 1.17397e-006
A 8 = -2.32279e-009 A10 = 9.24800e-011
13th surface
K = 0.00000e + 000A 4 = -1.03220e-004 A 6 = 2.75895e-006
A 8 = -1.16921e-008 A10 = -1.97440e-010
17th
K = 0.00000e + 000A 4 = -3.98840e-004 A 6 = 5.53134e-006
A 8 = -5.82520e-008 A10 = 3.53103e-010
18th
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 Mid-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

Group focal length
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

[Numeric data 2]
Surface data
Face number rd nd dd 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 1.721151 29.2 0.690
20 5.136 (variable)
21 ∞ 2 1.51633 64.1
Image plane 1. 1.43

Aspheric data
12th
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
13th surface
K = 0.00000e + 000A 4 = -3.30143e-004 A 6 = 1.12424e-005
A 8 = -2.54797e-007 A10 = 3.94749e-009
17th
K = 0.00000e + 000 A 4 = -1.30430e-003 A 6 = 2.76606e-006
A 8 = -1.39933e-007 A10 = -3.24081e-009
18th
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 Mid-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

Group focal length
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

[Numeric data 3]
Surface data
Face number rd nd dd 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 (stop) ∞ (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

Aspheric data
Face 10
K = 0.00000e + 000 A 4 = -3.96745e-005 A 6 = 2.63499e-007
A8 = -1.12658e-009 A10 = 1.78443e-011 A12 = 2.05813e-021
11th
K = 0.00000e + 000A 4 = -2.02684e-005 A 6 = 9.94170e-007
A 8 = -4.60023e-009 A10 = 3.74053e-011
16th
K = 0.00000e + 000 A 4 = -2.88302e-004 A 6 = -1.39776e-006
A 8 = 3.45138e-008 A10 = -7.62529e-010
17th
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 Mid-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

Group focal length
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

[Numeric data 4]
Surface data
Face number rd nd dd 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 (stop) ∞ (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. 1.88

Aspheric data
Face 10
K = 0.00000e + 000A 4 =-1.01331e-004 A 6 = 2.34520e-006
A 8 = -2.70658e-008 A10 = 9.38847e-010 A12 = 1.78026e-019
11th
K = 0.00000e + 000 A 4 = -2.07516e-005 A 6 = 6.69887e-006
A 8 = -7.24485e-008 A10 = 1.84979e-009
16th
K = 0.00000e + 000A 4 = -8.90032e-004 A 6 =-1. 08484e-006
A 8 = 4.36888e-008 A10 = -1.07330e-008
17th
K = 0.00000e + 000 A 4 = 1.02345e-004 A 6 = -3.17024e-006
A8 = -4.70198e-008 A10 = -3.84119e-009

Various data
Zoom ratio 2.3
Wide-angle Mid-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

Group focal length
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 first lens group L2 second lens group L3 third lens group L4 fourth lens group

Claims (14)

It consists of an aperture stop, a first lens group of negative refractive power arranged in order from the object side to the image side, an intermediate group including one or more lens groups, and a rear group, and the spacing between adjacent lens groups during zooming is A changing zoom lens,
The first lens group has two or more negative lenses and one or more positive lenses,
The rear group has a lens element nr of negative refractive power disposed closest to the image side,
Assuming that the Abbe number and the partial dispersion ratio of the lens element nr are νdnr and θCtnr, respectively
10 <νdnr <33
0.45 <θCtnr <0.78
A zoom lens characterized by satisfying the following conditional expression. Assuming that 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 claim 1, which satisfies the following conditional expression. The aperture stop is disposed closer to the image than the first lens group, and includes a lens group LP of positive refractive power disposed adjacent to the image side of the aperture stop, and the lens group LP has a wide angle. When the lens unit LP moves to the object side during zooming from the end to the telephoto end and the focal length of the lens unit LP is fp and the focal length of the entire system at the wide-angle end is fw,
1.5 <fp / fw <5.0
The zoom lens according to claim 1 or 2, wherein the following conditional expression is satisfied. Assuming that the focal length of the rear 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 3, wherein the following conditional expression is satisfied. When the Abbe number and the refractive index of the positive lens included in the first lens group are respectively dd1p and Nd1p,
12 <νd1p <28
1.75 <Nd1p <2.20
The zoom lens according to any one of claims 1 to 4, wherein the following conditional expression is satisfied. The aperture stop is disposed on the image side of the first lens unit, and a lens unit located on the object side of the aperture stop is a front lens unit, and a lens unit located on the image side of the aperture stop is a rear lens unit Assuming that 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,
−1.2 <fAw / fBw <−0.40
The zoom lens according to any one of claims 1 to 5, wherein the following conditional expression is satisfied. It has an aperture stop disposed on the image side of the first lens group, and includes a lens group LP of positive refractive power disposed adjacent to the image side of the aperture stop, the lens group LP having a wide-angle end The lens unit Lp has a plurality of positive lenses, and the Abbe number of the plurality of positive lenses is the largest Abbe number as 正 dp1, and the second largest Abbe number. When νdp2,
75 <(νdp1 + νdp2) / 2 <96
The zoom lens according to any one of claims 1 to 6, wherein the following conditional expression is satisfied.   8. The image display apparatus according to any one of claims 1 to 7, wherein the intermediate group comprises a second lens group of negative refractive power, and the rear group comprises a third lens group of positive refractive power. Zoom lens described.   9. The zoom lens according to claim 8, wherein the second lens unit moves to the object side during focusing from infinity to near distance.   The intermediate group includes a second lens group having negative refractive power and a third lens group having positive refractive power, which are disposed in order from the object side to the image side, and the rear group includes a fourth lens group having negative refractive power. The zoom lens according to any one of claims 1 to 7, wherein the zoom lens comprises:   11. The zoom lens according to claim 10, wherein the fourth lens unit is moved to the image side during focusing from infinity to near distance.   8. The image display apparatus according to any one of claims 1 to 7, wherein the intermediate group is constituted of a second lens group of positive refractive power, and the rear group is constituted of a third lens group of negative refractive power. Zoom lens described.   The zoom lens according to claim 12, wherein the third lens unit moves to the image side during focusing from infinity to near distance.   An image pickup apparatus comprising: the zoom lens according to any one of claims 1 to 13; and an image pickup element for receiving an image formed by the zoom lens.