JP6046504B2 - Imaging lens system - Google Patents

Description

  The present invention relates to an imaging lens system suitable for a photographic lens used in a digital camera, a single-lens reflex camera, and a video camera, particularly a camera having an imaging element called an APS-C size.

  A single-lens reflex camera generally has a mechanism in which a mirror disposed inside a camera body is mirrored up at the time of shooting to take an image. Therefore, an imaging lens system used in a single-lens reflex camera needs to have sufficient back focus to avoid interference with a movable mirror.

  Therefore, the imaging lens system having a wide angle in particular is a so-called retrofocus type in which a lens group having a negative refractive power and a lens group having a positive refractive power are arranged in order from the object side in order to ensure back focus. There is a need for lenses to be adopted. Patent Documents 1 and 2 disclose lenses that employ a retrofocus type.

  In addition, it is advantageous for shooting that intends to reduce the exposure time when shooting in astronomical objects and dark places, or to remove the objects before and after the focused object from the depth of field and cause so-called blur. There is a demand for a lens having a large aperture ratio. Japanese Patent Application Laid-Open No. H10-228561 discloses a lens that has a large aperture while ensuring a back focus by adopting a retrofocus type.

  Further, there is a demand for a lens that achieves a small size that is advantageous for portability and convenience during use, while ensuring a back focus by adopting a retrofocus type. Patent Document 2 discloses a lens that employs a retrofocus type while reducing the total optical length.

Japanese Patent Laid-Open No. 11-211978 JP 2009-237542 A

  The imaging lens system described in Patent Document 1 achieves a large aperture ratio. However, since the imaging lens system described in Patent Document 1 employs a retrofocus type that needs to increase the absolute value of the negative refractive power of the front lens group in order to ensure back focus, It is necessary to satisfactorily correct coma, astigmatism, spherical aberration, and distortion due to the configuration. In order to correct these aberrations, the imaging lens system described in Patent Document 1 has an increase in the number of components and the optical total length of the imaging lens system is large, and downsizing the optical total length is a major issue.

  Although the imaging lens system described in Patent Document 1 is an inner focus, the inner focus group is divided into two in order to correct aberrations during focusing, and each group is moved at different speeds along the optical axis. A so-called floating mechanism is adopted. Therefore, in the imaging lens system described in Patent Document 1, the mechanism of the lens barrel tends to be complicated, and the size is increased, and downsizing is a big problem.

  Further, the imaging lens system described in Patent Document 2 can be sufficiently downsized. However, in the imaging lens system described in Patent Document 2, it is necessary to suppress the aperture ratio in order to satisfactorily correct various aberrations such as reduction of the number of lenses and spherical aberration. Therefore, the imaging lens system described in Patent Document 2 has a problem that it is difficult to achieve a so-called large aperture ratio with an open F number of about 1.4 while satisfactorily correcting various aberrations.

  Therefore, the present invention has been made in view of such a situation, and by solving the above problems by the means shown below, a wide angle with a large aperture ratio and a sufficient optical total length after securing a sufficient back focus. An object of the present invention is to provide an imaging lens system that has a good imaging performance over the entire focusing area while reducing the size.

  The present invention solves the above problems by the following means.

The first invention, which is means for solving the above-mentioned problems, is a first lens group G1 having a positive refractive power in order from the object side, and a second lens group G2 including an aperture stop S and having a positive refractive power. The first lens group G1 includes, in order from the object side, a first lens L1 that is a meniscus lens having negative refractive power with a convex surface facing the object side, and a negative lens with a convex surface facing the object side. The second lens L2 is a meniscus lens having a refractive power and the third lens L3 having a positive refractive power with the convex surface facing the object side. When focusing from infinity to a short distance, the first lens An imaging lens system characterized in that the group G1 is fixed with respect to the image plane, the second lens group G2 moves toward the object side, and satisfies the following conditional expressions (1) to (3).
(1) 2.50 <TT / BF <3.00
(2) 1.00 <BF / f <1.35
(3) 1.20 <Fno <1.65
TT: Total optical length of the imaging lens system at infinity at the object distance BF: Back focus of the imaging lens system at infinity at the object distance f: Composite focal length Fno at the time of focusing on the object side at infinity of the imaging lens system: F-number of the imaging lens system at infinite object distance

A second invention, which is a means for solving the above-mentioned problems, is an imaging lens system according to the first invention, which further satisfies the following conditional expression: .
(4) 0.33 <Y / BF <0.45
Y: Maximum image height of the imaging lens system

  A third invention, which is a means for solving the above-mentioned problems, is an imaging lens system according to the first invention or the second invention, and is further closest to the image plane in the second lens group G2. An imaging lens system is characterized in that at least one surface of the arranged lens is an aspherical surface.

  Therefore, according to the present invention, it is possible to provide an imaging lens system that has a wide aperture with a large aperture ratio while ensuring a sufficient back focus, and has good imaging performance over the entire focusing area while reducing the overall optical length. it can.

It is a lens block diagram in the infinite distance of the interchangeable lens which concerns on Example 1 of this invention. FIG. 6 is a longitudinal aberration diagram when focusing on an object at infinity according to Example 1. FIG. 6 is a lateral aberration diagram when focusing on an object at infinity according to Example 1. FIG. 4 is a longitudinal aberration diagram of Example 1 at a shooting distance of 600 mm. FIG. 4 is a lateral aberration diagram at Example 600 at an imaging distance of 600 mm. It is a lens block diagram in the infinite distance of the interchangeable lens which concerns on Example 2 of this invention. FIG. 6 is a longitudinal aberration diagram of Example 2 when focusing on an object at infinity. FIG. 10 is a lateral aberration diagram for Example 2 upon focusing on an object at infinity. FIG. 6 is a longitudinal aberration diagram of Example 2 at an imaging distance of 600 mm. FIG. 4 is a lateral aberration diagram at Example 600 at an imaging distance of 600 mm. It is a lens block diagram in the infinite distance of the interchangeable lens which concerns on Example 3 of this invention. FIG. 6 is a longitudinal aberration diagram of Example 3 when focusing on an object at infinity. FIG. 5 is a lateral aberration diagram for Example 3 upon focusing on an object at infinity. FIG. 6 is a longitudinal aberration diagram of Example 3 at a shooting distance of 600 mm. FIG. 5 is a lateral aberration diagram at Example 600 at an imaging distance of 600 mm. It is a lens block diagram in the infinite distance of the interchangeable lens which concerns on Example 4 of this invention. FIG. 6 is a longitudinal aberration diagram when focusing on an object at infinity according to example 4. FIG. 10 is a lateral aberration diagram for Example 4 upon focusing on an object at infinity. FIG. 6 is a longitudinal aberration diagram of Example 4 at a shooting distance of 600 mm. FIG. 6 is a lateral aberration diagram at Example 600 at an imaging distance of 600 mm. It is a lens block diagram in the infinite distance of the interchangeable lens which concerns on Example 5 of this invention. FIG. 6 is a longitudinal aberration diagram when focusing on an object at infinity according to example 5. FIG. 10 is a transverse aberration diagram for Example 5 upon focusing on an object at infinity. FIG. 6 is a longitudinal aberration diagram of Example 5 at an imaging distance of 600 mm. FIG. 6 is a lateral aberration diagram at Example 600 at an imaging distance of 600 mm. It is a lens block diagram in the infinite distance of the interchangeable lens which concerns on Example 6 of this invention. FIG. 12 is a longitudinal aberration diagram when focusing on an object at infinity according to example 6. FIG. 10 is a transverse aberration diagram for Example 6 upon focusing on an object at infinity. FIG. 6 is a longitudinal aberration diagram of Example 6 at a shooting distance of 600 mm. FIG. 6 is a lateral aberration diagram at Example 600 with an imaging distance of 600 mm. It is a lens block diagram in the infinite distance of the interchangeable lens which concerns on Example 7 of this invention. FIG. 11 is a longitudinal aberration diagram when focusing on an object at infinity according to Example 7. FIG. 10 is a transverse aberration diagram for Example 7 upon focusing on an object at infinity. FIG. 10 is a longitudinal aberration diagram at Example 600 with an imaging distance of 600 mm. FIG. 6 is a lateral aberration diagram at Example 600 with an imaging distance of 600 mm.

  Hereinafter, the best mode for carrying out the present invention will be described. In addition, this invention is not limited by the form of this Example.

  The imaging lens system according to the present invention includes, as the first invention, the imaging lens systems according to the first to seventh embodiments of the present invention shown in FIGS. 1, 6, 11, 16, 21, 26, and 31. As can be seen from the lens configuration diagram, the first lens group G1 having positive refractive power in order from the object side and the second lens group G2 including the aperture stop S and having positive refractive power, The lens group G1 is a first lens L1 that is a meniscus lens having a negative refractive power with a convex surface facing the object side and a meniscus lens having a negative refractive power with a convex surface facing the object side. The second lens L2 and a third lens L3 having a positive refractive power facing the object side and having a positive refractive power, the first lens group G1 is fixed with respect to the image plane during focusing from infinity to short distance. The second lens group G2 moves to the object side Going on.

  The first lens group G1 in the imaging lens system of the present invention includes, in order from the object side, a first lens L1 that is a meniscus lens having a negative refractive power with a convex surface facing the object side, and a negative lens with a convex surface facing the object side. The second lens L2 is a meniscus lens having a refractive power of 3 and the third lens L3 has a positive refractive power with a convex surface facing the object side. This is to secure the back focus by increasing the absolute value of the negative refractive power of the first lens L1 having negative refractive power and the second lens L2 having negative refractive power. However, negative distortion occurs. Therefore, by arranging the third lens L3 having a positive refractive power closer to the image plane side than the first lens L1 and the second lens L2, negative distortion can be suppressed, and imaging performance can be reduced. Contributes to improvement.

  Further, the first lens group G1 in the imaging lens system of the present invention has a weak positive refractive power as a whole. By doing so, the axial light beam emitted from the first lens group G1 becomes close to afocal. As a result, this is advantageous in reducing aberration fluctuations during focusing, which will be described later, and contributes to imaging performance.

  Further, the first lens group G1 in the imaging lens system of the present invention is configured to be fixed during focusing. By adopting such a configuration, it is not necessary to move the first lens group G1 having a large lens weight, so that the burden on the focusing mechanism is reduced, which contributes to the improvement of the focusing speed and the accuracy of the stop position at the in-focus position.

  Subsequently, the second lens group G2 in the imaging lens system of the present invention moves toward the object side during focusing from infinity to a short distance, thereby reducing the distance between the first lens group G1 and the second lens group G2. It has a configuration. This is because the distance between the axial light beam portions that are close to afocal in the first lens group G1 described above is reduced, so that the ratio of the change in the axial light beam due to the reduction in the distance is reduced to reduce the spherical aberration. The fluctuation of the is suppressed. That is, it contributes to improvement of imaging performance. Further, the height of the chief ray passing through the first lens group G1 is lowered as the interval between the axial light beam portions is reduced. This alleviates overcorrection of astigmatism and makes it possible to suppress aberration fluctuations compared to focusing that extends all over, thereby contributing to improvement in imaging performance.

The imaging lens system according to the present invention satisfies the following conditional expressions (1) to (3).
(1) 2.50 <TT / BF <3.00
(2) 1.00 <BF / f <1.35
(3) 1.20 <Fno <1.65
TT: Optical total length of the imaging lens system at an object distance of infinity BF: Back focus of the imaging lens system at an object distance of infinity f: Focal length Fno: Object distance of the imaging lens system at the object side infinity F number at infinity

  Conditional expression (1) defines the ratio between the total optical length of the imaging lens system and the back focus as a preferable condition for obtaining a small and yet good imaging performance. The optical total length is the length on the optical axis from the object plane to the image plane of the lens arranged closest to the object side in the entire imaging lens system.

  Aberration correction is advantageous when the upper limit of conditional expression (1) is exceeded, but the total optical length of the imaging lens system is increased, which is not preferable in downsizing.

  If the lower limit of conditional expression (1) is not reached, the total optical length of the imaging lens system is shortened, which is advantageous for downsizing. However, spherical aberration, coma aberration, and astigmatism occurring in the entire imaging lens system cannot be corrected satisfactorily, which is not preferable for imaging performance. In addition, it is difficult to ensure the back focus.

  In addition, regarding the conditional expression (1), when the upper limit value is further set to 2.90 and the lower limit value is further set to 2.60, the above-described effect can be further ensured.

  Conditional expression (2) defines an appropriate range for the ratio between the back focus and the focal length of the imaging lens system, generally called a retro ratio.

  If the upper limit of conditional expression (2) is exceeded, the refractive power of the negative lens in the first lens group G1 of the imaging lens system must be increased, and it is difficult to correct the Petzval sum in the imaging lens system of the present invention. In particular, astigmatism and field curvature are deteriorated, which is not preferable for imaging performance.

  If the lower limit value of conditional expression (2) is not reached, the retro ratio becomes small, and it becomes difficult to ensure the back focus.

  In addition, regarding the conditional expression (2), by further setting the upper limit value to 1.30 and further setting the lower limit value to 1.10, the above-described effect can be further ensured.

  Conditional expression (3) defines an appropriate range for the open F number of the imaging lens system.

  When the upper limit value of conditional expression (3) is exceeded, the aperture ratio decreases, so it becomes easy to correct various aberrations, particularly spherical aberration, and the size can be reduced by reducing the number of lens components and shortening the optical total length of the imaging lens system. Although advantageous, it is difficult to achieve a large aperture ratio, which is not preferable for an imaging lens system that is small and has a wide angle with a large aperture ratio.

  When the lower limit value of conditional expression (3) is not reached, sagittal coma flare generated on a strong lens curved surface increases, and its correction becomes difficult. If the sagittal coma flare remains, the MTF performance in the low frequency region deteriorates. If this is to be corrected, it is necessary to increase the number of lens components or to increase the total optical length. It is not preferable for a small imaging lens system having image performance.

  In addition, regarding the conditional expression (3), by further setting the upper limit value to 1.55 and further setting the lower limit value to 1.30, the above-described effect can be further ensured.

Furthermore, in order to obtain a small and favorable imaging performance, the following conditional expression (4) is satisfied.
(4) 0.33 <Y / BF <0.45
Y: Maximum image height of the imaging lens system

  Conditional expression (4) defines the ratio between the maximum image height of the imaging lens system and the back focus as a preferable condition for obtaining a small and yet good imaging performance.

  If the upper limit of conditional expression (4) is exceeded, the back focus becomes relatively short, which is not preferable. Further, if the back focus is to be secured, the image height becomes relatively high, so that the spherical aberration and the curvature of field cannot be corrected satisfactorily, which is not preferable for the imaging performance.

  When the lower limit value of conditional expression (4) is not reached, the image height becomes relatively low, so that back focus can be secured. However, the angle of view becomes narrow and it becomes difficult to obtain a wide angle of view. Therefore, it is not preferable for an imaging lens system having a wide aperture with a large aperture ratio. Further, if the image height is maintained, the back focus becomes relatively long, which is not preferable for reducing the optical total length.

  In the conditional expression (4), the above-mentioned effect can be further ensured by setting the upper limit value to 0.43 and the lower limit value to 0.35.

  In the imaging lens system according to the third aspect of the present invention, at least one surface of the lens disposed closest to the image plane of the second lens group G2 is aspherical. It corrects well and contributes to the improvement of imaging performance. In addition, it is possible to reduce the number of lens components as compared with a case where an equivalent imaging performance is obtained using only the spherical system. Therefore, the optical total length of the imaging lens system can be suppressed, which contributes to the miniaturization of the optical total length. Furthermore, this aspherical surface can be manufactured at a low cost and with high accuracy by producing it by the glass mold method.

  In the imaging lens system of the present invention, it is more effective to accompany the following configuration.

  When the lens disposed closest to the image plane of the second lens group G2 is an aspherical surface, spherical aberration and coma are easily changed depending on the surface accuracy, and thus has a positive positive refractive power that is easy to manufacture with high accuracy. A lens is more desirable. Further, in order to enhance the effect of aberration correction, it is more desirable that both surfaces be aspherical surfaces.

  Next, a lens configuration of an example according to the imaging lens system of the present invention will be described. In the following description, the lens configuration is described in order from the object side to the image side.

  Specific numerical data of each embodiment of the imaging lens system of the present invention described above will be shown below.

  In [Surface data], the surface number is the number of the lens surface or aperture stop counted from the object side, r is the radius of curvature of each surface, d is the distance between the surfaces, nd is the refractive index with respect to the d-line (wavelength 587.56 nm). , Vd indicate Abbe numbers for the d line.

  The * (asterisk) attached to the surface number indicates that the lens surface shape is an aspherical surface. BF represents back focus.

  The (diaphragm) attached to the surface number indicates that the aperture stop S is located at that position. ∞ (infinity) is entered in the radius of curvature for the plane or aperture stop S.

In [Aspherical data], each coefficient value giving the aspherical shape of the lens surface marked with * in [Surface data] is shown. The shape of the aspheric surface is y for the displacement from the optical axis in the direction perpendicular to the optical axis, z for the displacement (sag amount) from the intersection of the aspheric surface and the optical axis in the optical axis direction, and r for the radius of curvature of the reference spherical surface. When the conic coefficients are K, 4, 6, 8, and the 10th-order aspheric coefficients are A4, A6, A8, and A10, respectively, the coordinates of the aspheric surface are expressed by the following equations.

  In [various data], a value of infinity (INF) is shown.

  [Variable interval data] indicates values of the variable interval and BF (back focus) when the shooting distance is infinity (INF) and 600 mm.

  In all the following specification values, the focal length f, the radius of curvature r, the lens surface interval d, and other length units described are in millimeters (mm) unless otherwise specified. However, since the same optical performance can be obtained in proportional enlargement and proportional reduction, it is not limited to this.

  FIG. 1 is a lens configuration diagram of an imaging lens system according to Example 1 of the present invention. In order from the object side, the first lens group G1 has a positive refractive power as a whole, a first lens L1 that is a meniscus lens having a negative refractive power with the convex surface facing the object side, and a convex surface on the object side. The second lens L2 is a meniscus lens having a negative refractive power toward the object, and a third lens L3 having a positive refractive power with the convex surface facing the object side. The second lens group G2 is positively refracted as a whole. Lens L4 having a positive refractive power with a convex surface facing the object side, L5 having a negative refractive power with a biconcave shape, an aperture stop S, and a negative lens with a concave surface facing the object side A cemented lens obtained by bonding L6 having refractive power and L7 having biconvex positive refractive power, a lens L8 having positive refractive power with a convex surface facing the image surface side, and both surfaces are aspherical. L9, which has a positive refractive power, and is used for focusing from an object at infinity to a near object. The first lens group G1 is fixed with respect to the image plane, the second lens group G2 moves toward the object side, aperture stop S moves in the same path without changing the distance between the front and rear of the lens.

  In the lens configuration diagram, I is an image plane, which indicates the surface of the image sensor.

Subsequently, specification values of the imaging lens system according to Example 1 are shown below.
Numerical example 1
Unit: mm
[Surface data]
Surface number rd nd vd
1 79.7416 1.0000 1.51680 64.20
2 24.1967 5.8508
3 821.6299 1.0000 1.48749 70.44
4 34.6531 6.9632
5 34.8591 7.6704 1.62041 60.34
6 -77.7385 (d6)
7 40.6045 6.2678 1.75520 27.53
8 -1548.9374 3.0312
9 -169.5439 1.0000 1.80518 25.46
10 44.5130 4.3810
11 (Aperture) ∞ 7.1696
12 -17.9099 1.6071 1.76182 26.61
13 71.7339 6.1003 1.80420 46.50
14 -37.5094 0.1500
15 -200.1294 3.7906 1.72916 54.67
16 -43.0881 0.1500
17 * 142.2414 5.0190 1.77250 49.47
18 * -42.6480 (BF)

[Aspherical data]
17 faces 18 faces
K 0.00000E + 00 0.00000E + 00
A4 -4.06947E-07 5.73182E-06
A6 0.00000E + 00 -1.99338E-09
A8 0.00000E + 00 5.80103E-12
A10 0.00000E + 00 -3.50184E-15

[Various data]
INF
Focal length 30.78
F number 1.46
Full angle of view 2ω 50.64
Statue height Y 14.20
Total lens length 105.00

[Variable interval data]
INF 600mm
d6 5.4490 3.5754
BF 38.3990 40.2725

[Lens group data]
Group Start surface Focal length
G1 1 239.28
G2 7 40.87

  FIG. 6 is a lens configuration diagram of the imaging lens system according to Example 2 of the present invention. In order from the object side, the first lens group G1 has a positive refractive power as a whole, a first lens L1 that is a meniscus lens having a negative refractive power with the convex surface facing the object side, and a convex surface on the object side. The second lens L2 is a meniscus lens having a negative refractive power toward the object, and a third lens L3 having a positive refractive power with the convex surface facing the object side. The second lens group G2 is positively refracted as a whole. Lens L4 having a positive refractive power with a convex surface facing the object side, L5 having a negative refractive power with a biconcave shape, an aperture stop S, and a negative lens with a concave surface facing the object side A cemented lens obtained by bonding L6 having refractive power and L7 having biconvex positive refractive power, a lens L8 having positive refractive power with a convex surface facing the image surface side, and both surfaces are aspherical. L9, which has a positive refractive power, and is used for focusing from an object at infinity to a near object. The first lens group G1 is fixed with respect to the image plane, the second lens group G2 moves toward the object side, aperture stop S moves in the same path without changing the distance between the front and rear of the lens.

  In the lens configuration diagram, I is an image plane, which indicates the surface of the image sensor.

Subsequently, specification values of the imaging lens system according to Example 2 are shown below.
Numerical example 2
Unit: mm
[Surface data]
Surface number rd nd vd
1 83.9402 1.0000 1.48749 70.44
2 23.4484 6.3588
3 1000.0000 1.0000 1.51680 64.20
4 31.7922 8.2593
5 36.4465 7.7281 1.62041 60.34
6 -64.4840 (d6)
7 59.0993 3.8189 1.76182 26.61
8 ∞ 6.8237
9 -123.8522 1.0000 1.84666 23.78
10 79.9486 3.4286
11 (Aperture) ∞ 7.6408
12 -16.6537 1.0000 1.76182 26.61
13 143.5280 6.0995 1.80420 46.50
14 -31.4736 0.1500
15 -284.1222 4.6969 1.72916 54.67
16 -36.7002 0.1500
17 * 202.4136 4.3717 1.77250 49.47
18 * -49.4360 (BF)

[Aspherical data]
17 faces 18 faces
K 0.00000E + 00 0.00000E + 00
A4 -1.61803E-06 3.63210E-06
A6 1.25626E-09 2.37138E-10
A8 0.00000E + 00 2.34941E-12
A10 0.00000E + 00 1.21607E-15

[Various data]
INF
Focal length 28.19
F number 1.45
Full angle of view 2ω 54.65
Statue height Y 14.20
Total lens length 107.00

[Variable interval data]
INF 600mm
d6 4.6737 3.1009
BF 38.7984 40.3712

[Lens group data]
Group Start surface Focal length
G1 1 217.63
G2 7 39.40

  FIG. 11 is a lens configuration diagram of the imaging lens system according to Example 3 of the present invention. In order from the object side, the first lens group G1 has a positive refractive power as a whole, a first lens L1 that is a meniscus lens having a negative refractive power with the convex surface facing the object side, and a convex surface on the object side. The second lens L2 is a meniscus lens having a negative refractive power toward the object, and a third lens L3 having a positive refractive power with the convex surface facing the object side. The second lens group G2 is positively refracted as a whole. Lens L4 having a positive refractive power with the convex surface facing the object side, L5 having a negative refractive power, an aperture stop S, and a negative refractive power with the concave surface facing the object side A cemented lens in which L6 and a biconvex L7 having a positive refractive power are bonded together, a lens L8 having a positive refractive power with a convex surface facing the image surface side, and a positive surface in which both surfaces are formed of aspheric surfaces When focusing from an object at infinity to an object at a short distance, Lens group G1 is fixed with respect to the image plane, the second lens group G2 moves toward the object side, aperture stop S moves in the same path without changing the distance between the front and rear of the lens.

  In the lens configuration diagram, I is an image plane, which indicates the surface of the image sensor.

Subsequently, specification values of the imaging lens system according to Example 3 are shown below.
Numerical example 3
Unit: mm
[Surface data]
Surface number rd nd vd
1 115.3033 1.0000 1.48749 70.44
2 26.7846 6.9099
3 1004.5958 1.0000 1.77250 49.62
4 44.1906 7.6611
5 52.8482 8.4409 1.80420 46.50
6 -66.0711 (d6)
7 34.3450 4.8940 1.78590 43.93
8 72.5018 4.1464
9 595.4078 1.0000 1.84666 23.78
10 52.5249 4.8526
11 (Aperture) ∞ 8.2805
12 -23.1687 1.0000 1.76182 26.61
13 89.4169 7.0910 1.80420 46.50
14 -44.2695 0.1500
15 -69.2952 3.2683 1.72916 54.67
16 -43.3172 0.1500
17 * 91.2292 6.5813 1.77250 49.47
18 * -46.3878 (BF)

[Aspherical data]
17 faces 18 faces
K 0.00000E + 00 0.00000E + 00
A4 -2.34038E-06 3.32183E-06
A6 0.00000E + 00 -9.45116E-10
A8 0.00000E + 00 1.43155E-12
A10 0.00000E + 00 3.45822E-16

[Various data]
INF
Focal length 31.22
F number 1.25
Full angle of view 2ω 49.92
Statue height Y 14.20
Total lens length 110.00

[Variable interval data]
INF 600mm
d6 5.5739 3.6133
BF 37.9992 39.9598

[Lens group data]
Group Start surface Focal length
G1 1 189.39
G2 7 43.98

  FIG. 16 is a lens configuration diagram of an imaging lens system according to Example 4 of the present invention. In order from the object side, the first lens group G1 has a positive refractive power as a whole, a first lens L1 that is a meniscus lens having a negative refractive power with the convex surface facing the object side, and a convex surface on the object side. The second lens L2 is a meniscus lens having a negative refractive power toward the object, and a third lens L3 having a positive refractive power with the convex surface facing the object side. The second lens group G2 is positively refracted as a whole. Lens L4 having a positive refractive power with a convex surface facing the object side, an aperture stop S, L5 having a negative refractive power with a concave surface facing the object side, and a biconvex positive refraction A cemented lens obtained by bonding L6 having a force and L7 having a positive refractive power formed by an aspheric surface on the image plane side. The lens group G1 is fixed with respect to the image plane, the second lens group G2 moves toward the object side, Mouth stop S moves in the same path without changing the distance between the front and rear of the lens.

  In the lens configuration diagram, I is an image plane, which indicates the surface of the image sensor.

Subsequently, specification values of the imaging lens system according to Example 4 are shown below.
Numerical example 4
Unit: mm
[Surface data]
Surface number rd nd vd
1 347.1392 1.0000 1.53172 48.84
2 20.6137 3.9672
3 384.6098 1.0000 1.58144 40.89
4 53.1216 0.8049
5 27.3036 5.9014 1.77250 49.62
6 -105.5975 (d6)
7 31.1049 5.7256 1.80518 25.46
8 33.9814 5.3398
9 (Aperture) ∞ 5.8791
10 -15.0370 4.4792 1.76182 26.61
11 65.0186 5.7971 1.77250 49.62
12 -25.4404 0.1500
13 80.1401 4.9186 1.77250 49.47
14 * -35.5189 (BF)

[Aspherical data]
14
K 0.00000E + 00
A4 9.02321E-06
A6 -8.39906E-09
A8 3.94948E-11
A10 -4.44100E-14

[Various data]
INF
Focal length 30.92
F number 1.60
Full angle of view 2ω 39.21
Statue height Y 10.82
Total lens length 83.00

[Variable interval data]
INF 600mm
d6 5.5371 3.6824
BF 32.5000 34.3547

[Lens group data]
Group Start surface Focal length
G1 1 171.30
G2 7 35.63

  FIG. 21 is a lens configuration diagram of the imaging lens system according to Example 5 of the present invention. In order from the object side, the first lens group G1 has a positive refractive power as a whole, a first lens L1 that is a meniscus lens having a negative refractive power with the convex surface facing the object side, and a convex surface on the object side. The second lens L2 is a meniscus lens having a negative refractive power toward the object, and a third lens L3 having a positive refractive power with the convex surface facing the object side. The second lens group G2 is positively refracted as a whole. Lens L4 having a positive refractive power with a convex surface facing the object side, L5 having a negative refractive power with a biconcave shape, an aperture stop S, and a negative lens with a concave surface facing the object side It consists of a cemented lens made by bonding L6, which has refractive power, and L7, which has a biconvex shape and has positive refractive power, and L8, which has a positive refractive power and is aspherical on both sides. When focusing on a distance object, the first lens group G1 is fixed with respect to the image plane. Lens group G2 moves toward the object side, aperture stop S moves in the same path without changing the distance between the front and rear of the lens.

  In the lens configuration diagram, I is an image plane, which indicates the surface of the image sensor.

Subsequently, specification values of the imaging lens system according to Example 5 are shown below.
Numerical example 5
Unit: mm
[Surface data]
Surface number rd nd vd
1 187.5268 1.0000 1.51742 52.15
2 30.6033 4.6135
3 378.4556 1.0000 1.48749 70.44
4 41.2900 5.9030
5 39.4460 6.6141 1.77250 49.62
6 -148.9879 (d6)
7 44.3603 5.0390 1.83481 42.72
8 323.8371 5.1420
9 -208.4111 1.0000 1.69895 30.05
10 44.1776 4.2800
11 (Aperture) ∞ 6.9878
12 -19.0286 4.0811 1.76182 26.61
13 112.9487 6.3431 1.77250 49.62
14 -31.6810 1.1024
15 * 74.4940 6.1160 1.77250 49.47
16 * -40.6109 (BF)

[Aspherical data]
15 faces 16 faces
K 0.00000E + 00 0.00000E + 00
A4 -2.09456E-06 4.19204E-06
A6 7.99330E-10 9.70388E-11
A8 0.00000E + 00 7.27073E-13
A10 0.00000E + 00 8.05603E-16

[Various data]
INF
Focal length 35.97
F number 1.45
Full angle of view 2ω 43.82
Statue height Y 14.20
Total lens length 105.00

[Variable interval data]
INF 600mm
d6 6.9781 4.3982
BF 38.8000 41.3798

[Lens group data]
Group Start surface Focal length
G1 1 204.55
G2 7 43.90

  FIG. 26 is a lens configuration diagram of the imaging lens system according to Example 6 of the present invention. In order from the object side, the first lens group G1 has a positive refractive power as a whole, a first lens L1 that is a meniscus lens having a negative refractive power with the convex surface facing the object side, and a convex surface on the object side. The second lens L2 is a meniscus lens having a negative refractive power toward the object, and a third lens L3 having a positive refractive power with the convex surface facing the object side. The second lens group G2 is positively refracted as a whole. A lens L4 having a negative refractive power with a convex surface facing the object side, an aperture stop S, a L5 having a negative refractive power with a concave surface facing the object side, and a biconvex positive refraction It consists of a cemented lens pasted with L6 having power, a lens L7 having positive refractive power with the convex surface facing the image surface side, and L8 having positive refractive power formed by aspherical on the image surface side. When focusing from an object at infinity to an object at a short distance, the first lens group G1 faces the image plane. A fixed Te, the second lens group G2 moves toward the object side, aperture stop S moves in the same path without changing the distance between the front and rear of the lens.

  In the lens configuration diagram, I is an image plane, which indicates the surface of the image sensor.

Subsequently, specification values of the imaging lens system according to Example 6 are shown below.
Numerical example 6
Unit: mm
[Surface data]
Surface number rd nd vd
1 84.6836 1.0000 1.60342 38.01
2 23.7475 4.6027
3 652.9094 1.0000 1.48749 70.44
4 33.4736 5.5816
5 34.8637 6.7508 1.77250 49.62
6 -81.6574 (d6)
7 32.6926 9.4639 1.84666 23.78
8 27.2948 3.0000
9 (Aperture) ∞ 9.1054
10 -15.0188 1.7857 1.80518 25.46
11 73.1234 5.6615 1.80420 46.50
12 -31.9101 0.1500
13 294.7106 4.8879 1.72916 54.67
14 -36.3428 0.1500
15 276.9721 4.3738 1.77250 49.47
16 * -41.1846 (BF)

[Aspherical data]
16 sides
K 0.00000E + 00
A4 8.67797E-06
A6 -4.78841E-09
A8 2.34675E-11
A10 -3.92419E-14

[Various data]
INF
Focal length 27.84
F number 1.41
Full angle of view 2ω 43.09
Statue height Y 10.82
Total lens length 95.00

[Variable interval data]
INF 600mm
d6 5.4867 3.9565
BF 31.9998 33.5301

[Lens group data]
Group Start surface Focal length
G1 1 137.25
G2 7 35.13

  FIG. 31 is a lens configuration diagram of the imaging lens system according to Example 7 of the present invention. In order from the object side, the first lens group G1 has a positive refractive power as a whole, a first lens L1 that is a meniscus lens having a negative refractive power with the convex surface facing the object side, and a convex surface on the object side. The second lens L2 is a meniscus lens having a negative refractive power toward the object, and a third lens L3 having a positive refractive power with the convex surface facing the object side. The second lens group G2 is positively refracted as a whole. Lens L4 having a positive refractive power with a convex surface facing the object side, L5 having a negative refractive power with a biconcave shape, an aperture stop S, and a negative lens with a concave surface facing the object side A cemented lens in which L6 having a refractive power and L7 having a biconvex positive refractive power are bonded together, a lens L8 having a positive refractive power with a convex surface facing the image surface side, and an aspherical surface on the image surface side Consists of L9, which has a positive refractive power, and focuses from an object at infinity to a near object When, the first lens group G1 is fixed with respect to the image plane, the second lens group G2 moves toward the object side, aperture stop S moves in the same path without changing the distance between the front and rear of the lens.

  In the lens configuration diagram, I is an image plane, which indicates the surface of the image sensor.

Subsequently, specification values of the imaging lens system according to Example 7 are shown below.
Numerical example 7
Unit: mm
[Surface data]
Surface number rd nd vd
1 70.1284 1.0000 1.51680 64.20
2 22.2491 5.5221
3 120.2813 1.0000 1.48749 70.44
4 29.7286 6.2172
5 29.9443 7.4990 1.62041 60.34
6 -83.8122 (d6)
7 59.4411 3.8031 1.75520 27.53
8 -287.6070 4.3240
9 -297.7774 1.0000 1.80518 25.46
10 49.9143 3.6677
11 (Aperture) ∞ 8.1889
12 -14.1235 1.0000 1.76182 26.61
13 118.6309 7.0205 1.80420 46.50
14 -25.2564 0.1500
15 289.8204 5.1735 1.72916 54.67
16 -35.3214 0.1500
17 497.7686 3.3130 1.77250 49.47
18 * -64.7347 (BF)

[Aspherical data]
18 sides
K 0.00000E + 00
A4 6.03679E-06
A6 -3.47698E-09
A8 2.26662E-11
A10 -3.38092E-14

[Various data]
INF
Focal length 28.00
F number 1.46
Full angle of view 2ω 54.14
Statue height Y 14.20
Total lens length 98.00

[Variable interval data]
INF 600mm
d6 4.9711 3.4285
BF 34.0000 35.5426

[Lens group data]
Group Start surface Focal length
G1 1 150.96
G2 7 35.09

  In addition, a list of corresponding values of the conditional expressions in each of these examples is shown.

[Values for conditional expressions]
Conditional expression / Example 1 2 3 4 5 6 7
(1) 2.50 <TT / BF <3.00 2.73 2.76 2.89 2.55 2.71 2.97 2.88
(2) 1.00 <BF / f <1.40 1.25 1.38 1.22 1.05 1.08 1.15 1.21
(3) 1.20 <Fno <1.65 1.46 1.45 1.25 1.60 1.45 1.41 1.46
(4) 0.33 <Y / BF <0.45 0.37 0.37 0.37 0.33 0.37 0.34 0.42

L1 1st lens L2 2nd lens L3 3rd lens G1 1st lens group G1
G2 Second lens group G2
S aperture stop I image plane d d line C C line g g line Fno F number ΔS sagittal image plane ΔM meridional image plane Y image height

Claims (3)

A first lens group G1 having a positive refractive power in order from the object side, and a second lens group G2 including an aperture stop S and having a positive refractive power,
The first lens group G1 includes:
In order from the object side, a first lens L1 that is a meniscus lens having a negative refractive power with a convex surface facing the object side, and a second lens L2 that is a meniscus lens having a negative refractive power with a convex surface facing the object side A third lens L3 having a positive refractive power with a convex surface facing the object side,
During focusing from infinity to short distance, the first lens group G1 is fixed with respect to the image plane, and the second lens group G2 moves toward the object side.
An imaging lens system satisfying the following conditional expressions (1) to (3):
(1) 2.50 <TT / BF <3.00
(2) 1.00 <BF / f <1.35
(3) 1.20 <Fno <1.65
However,
TT: Total optical length of the imaging lens system at infinity at the object distance BF: Back focus of the imaging lens system at infinity at the object distance f: Composite focal length Fno at the time of focusing on the object side at infinity of the imaging lens system: F-number of the imaging lens system at infinite object distance The imaging lens system according to claim 1, wherein the following conditional expression is satisfied.
(4) 0.33 <Y / BF <0.45
However,
Y: Maximum image height of the imaging lens system 3. The imaging lens system according to claim 1, wherein at least one surface of the lens disposed closest to the image plane in the second lens group G <b> 2 is an aspherical surface.

Images