JP2014056055A - Zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact and light-weight zoom lens that can provide bright images in the entire variable magnification area, effectively corrects aberrations over the entire variable magnification area to maintain high optical performance, and includes resolution power that can be applied to a solid state imaging device with high pixels.SOLUTION: The present zoom lens is configured by arranging, in order from an object side, a first lens group Ghaving a positive refractive power, a second lens group Ghaving a negative refractive power, a third lens group Ghaving a positive refractive power, a fourth lens group Ghaving a positive refractive power, and a fifth lens group Ghaving a negative refractive power. The third lens group Gis configured by arranging, in order from the object side, a positive lens L(first lens) with an aspherical surface formed on both sides, and a negative lens L(second lens) composed of a negative meniscus lens with a convex surface directed to the object side. Both an increase in aperture ratio and an increase in resolution power can be achieved by satisfying predetermined conditions.

Description

  The present invention relates to a compact and lightweight zoom lens suitable for a camera equipped with a solid-state image sensor, particularly a surveillance camera.

  As a zoom lens widely used in surveillance cameras, there is a five-group zoom lens in which each lens group having positive, negative, positive, positive, and negative refractive power is arranged in order from the object side (for example, Patent Documents). 1 in Example 5, see Patent Document 2).

  In these zoom lenses, the first lens group, the third lens group, and the fifth lens group are all fixed, and zooming is performed by moving the second lens group in one direction. Further, by moving the fourth lens group in the direction along the optical axis, the correction of the image plane variation due to zooming and the focusing are performed. In addition, the zoom ratio of the zoom lens described in Example 5 of Patent Document 1 is about 3.2 times, and the F number is about 2.0 to 3.2. The zoom lens described in Patent Document 2 has a zoom ratio of about 5 times and an F-number of about 2.0 to 2.4.

JP 2009-237400 A JP 2002-365539 A

  By the way, as a zoom lens mounted on a surveillance camera, particularly a traffic surveillance camera, a large-aperture zoom lens that can satisfactorily monitor even at night or in a dim place has been desired. In addition, with the recent rapid increase in the number of pixels in solid-state image sensors (CCD, CMOS, etc.), it is possible to handle high-pixel solid-state image sensors (more than 3 million pixels that can check the finer features of the subject) There is a demand for a zoom lens having a high resolution.

  In order to obtain a high-quality image, it is essential to correct various aberrations well from the wide-angle end to the telephoto end. However, when attempting to achieve a large aperture ratio of a zoom lens using conventional technology, various aberrations occurring in all zooming ranges cannot be corrected well, and high optical performance is maintained over the entire zooming range. It becomes difficult to do. In addition, a bright image could not be obtained in the entire zoom range.

  As described above, the conventional zoom lens described in each of the above-mentioned patent documents cannot realize a zoom lens suitable for a surveillance camera for the purpose of monitoring at night or in a dim place.

  In order to eliminate the above-mentioned problems caused by the prior art, the present invention can obtain a bright image in the entire zoom range and maintain high optical performance by effectively correcting various aberrations in the entire zoom range. It is another object of the present invention to provide a small and lightweight zoom lens having a resolving power compatible with a high-pixel solid-state imaging device.

In order to solve the above-described problems and achieve the object, a zoom lens according to the present invention includes a first lens group having a positive refractive power and a second lens having a negative refractive power, which are arranged in order from the object side. A third lens group having a positive refractive power, a fourth lens group having a positive refractive power, and a fifth lens group having a negative refractive power, the third lens group comprising an object A first lens having a positive refractive power and an aspherical surface formed on at least one surface, and a meniscus second lens having a negative refractive power with a convex surface facing the object side, arranged in order from the side. A wide-angle end by fixing the first lens group, the third lens group, and the fifth lens group, and moving the second lens group from the object side to the image plane side along the optical axis. Zooming from the telephoto end to the telephoto end and moving the fourth lens group along the optical axis Corrects and focusing of image plane variation due to zooming by making moved, characterized by satisfying the conditional expressions below.
(1) 2.2 <| F3 / F4 | <3.5
(2) νdG3L1 / νdG3L2> 2.8
Where F3 is the focal length of the third lens group, F4 is the focal length of the fourth lens group, νdG3L1 is the Abbe number of the third lens group with respect to the d-line, and νdG3L2 is the third lens group. The Abbe number of the second lens with respect to the d-line is shown.

  According to the present invention, a bright image can be obtained in the entire zoom range, and high optical performance can be maintained by effectively correcting various aberrations over the entire zoom range, thus supporting a high-pixel solid-state imaging device. It is possible to provide a small and lightweight zoom lens having the resolving power possible.

The zoom lens according to the present invention is characterized in that, in the above invention, the following conditional expression is satisfied.
(3) 0.5 <| rp / f31 | <0.8
Here, rp represents the paraxial radius of curvature of the object side surface of the first lens of the third lens group, and f31 represents the focal length of the first lens of the third lens group.

  According to the present invention, it is possible to maintain high optical performance while reducing the manufacturing cost without deteriorating the workability of the zoom lens.

  The zoom lens according to the present invention is characterized in that, in the above invention, an aperture stop is disposed between the second lens group and the third lens group.

  According to the present invention, the diameter of the front lens can be reduced to reduce the size and weight of the entire zoom lens system.

  According to the present invention, a bright image can be obtained in the entire zoom range, and high optical performance can be maintained by effectively correcting various aberrations over the entire zoom range, thus supporting a high-pixel solid-state imaging device. There is an effect that it is possible to provide a small and lightweight zoom lens having a resolving power possible.

FIG. 3 is a cross-sectional view along the optical axis showing the configuration of the zoom lens according to Example 1; FIG. 6 is a diagram illustrating various aberrations of the zoom lens according to Example 1 with respect to the d line. FIG. 6 is a cross-sectional view along the optical axis showing the configuration of a zoom lens according to Example 2; FIG. 9 is a diagram illustrating various aberrations of the zoom lens according to Example 2 with respect to the d line. FIG. 6 is a cross-sectional view along the optical axis showing the configuration of a zoom lens according to Example 3; FIG. 10 is a diagram illustrating various aberrations of the zoom lens according to Example 3 with respect to the d line. FIG. 6 is a cross-sectional view along the optical axis showing the configuration of a zoom lens according to Example 4; FIG. 10 is a diagram illustrating all aberrations of the zoom lens according to Example 4 with respect to the d line.

  Hereinafter, preferred embodiments of the zoom lens according to the present invention will be described in detail.

  The zoom lens according to the present invention includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power, which are arranged in order from the object side. And a fourth lens group having a positive refractive power and a fifth lens group having a negative refractive power. In this zoom lens, the first lens group, the third lens group, and the fifth lens group are fixed, and the second lens group is moved from the object side to the image plane side along the optical axis, whereby the telephoto end to the telephoto end. Perform scaling to. Further, the fourth lens group is moved along the optical axis to correct image plane variation accompanying focusing and to perform focusing.

  The present invention is capable of obtaining a bright image in the entire zooming range, maintaining high optical performance by effectively correcting various aberrations over the entire zooming range, and being compatible with a solid-state imaging device with a high pixel. The object is to provide a compact and lightweight zoom lens with resolving power. In order to achieve this object, various conditions as shown below are set.

  First, in the zoom lens according to the present invention, the third lens group is arranged in order from the object side, a first lens having a positive refractive power and having an aspheric surface on at least one surface, and a negative lens with a convex surface facing the object side. And a second meniscus lens having a refractive power of 2 mm.

  By forming an aspherical surface on the first lens located closest to the object side in the third lens group, spherical aberrations and coma that become noticeable in the entire zoom range with a large aperture ratio can be corrected well. it can. Further, by arranging the meniscus second lens having negative refractive power with the convex surface facing the object side, various aberrations can be corrected more favorably. Since the two lenses having such characteristics are provided, it is possible to correct aberrations with a small number of lenses, so that the weight of the zoom lens can be reduced.

In addition, in the zoom lens according to the present invention, the focal length of the third lens group is F3, the focal length of the fourth lens group is F4, the Abbe number of the first lens of the third lens group with respect to the d-line is νdG3L1, When the Abbe number of the second lens of the three lens group with respect to the d-line is νdG3L2, it is preferable to satisfy the following conditional expression.
(1) 2.2 <| F3 / F4 | <3.5
(2) νdG3L1 / νdG3L2> 2.8

  Conditional expression (1) defines an appropriate range of the ratio between the focal length F3 of the third lens group and the focal length F4 of the fourth lens group in the zoom lens according to the present invention.

  If the lower limit of conditional expression (1) is not reached, the refractive power of the third lens group becomes too strong. In this case, it is effective in shortening the total length of the optical system, but it is difficult to correct various aberrations, particularly spherical aberration and coma aberration, which is not preferable. In addition, it becomes difficult to ensure the back focus of the optical system. On the other hand, if the upper limit in conditional expression (1) is exceeded, the refractive power of the third lens group becomes too weak, the overall length of the optical system increases, and it becomes difficult to reduce the size of the zoom lens.

  Conditional expression (2) defines an appropriate range of the ratio of the Abbe number to the d-line of each of the first lens and the second lens constituting the third lens group. By satisfying conditional expression (2), it is possible to satisfactorily correct chromatic aberrations (axial chromatic aberration and lateral chromatic aberration) that occur in the entire zooming range as the aperture ratio is increased. If the lower limit of conditional expression (2) is not reached, it will be difficult to correct chromatic aberration that becomes noticeable in the entire zoom range as the aperture ratio increases.

Further, in the zoom lens according to the present invention, when the paraxial radius of curvature of the object side surface of the first lens of the third lens group is rp and the focal length of the first lens of the third lens group is f31, the following conditional expression Is preferably satisfied.
(3) 0.5 <| rp / f31 | <0.8

  Conditional expression (3) is an expression that defines the shape of the object side surface of the first lens arranged closest to the object side in the third lens group. In the present invention, a convex surface having a large curvature is formed on the object side surface of the first lens in order to satisfactorily correct various aberrations. For this reason, by satisfying conditional expression (3), high optical performance can be maintained without deteriorating the workability of the first lens.

  If the lower limit of conditional expression (3) is not reached, the paraxial radius of curvature of the object side surface of the first lens in the third lens group becomes too small, and the workability of the first lens deteriorates. When the processability of the lens deteriorates, the manufacturing cost of the zoom lens increases, which is not preferable. On the other hand, if the upper limit in conditional expression (3) is exceeded, the workability of the first lens will be good, but it will be difficult to correct various aberrations, particularly spherical aberration and coma aberration, and optical performance will deteriorate.

  Furthermore, in the zoom lens according to the present invention, an aperture stop that defines a predetermined aperture may be disposed between the second lens group and the third lens group. In general, when the aperture ratio is increased, the aperture stop diameter is increased accordingly. As the aperture stop diameter increases, the front lens diameter of the optical system tends to increase. Therefore, in the present invention, the front lens diameter of the optical system can be reduced by arranging an aperture stop between the second lens group and the third lens group having the smallest light beam diameter in the optical system, and zoom The entire lens system can be reduced in size and weight.

  As described above, the zoom lens according to the present invention has the above-described configuration, so that a bright image can be obtained in the entire zoom range, and various aberrations can be effectively corrected over the entire zoom range. A high optical performance can be maintained, and a resolving power that can be applied to a solid-state imaging device having a high pixel can be provided.

  In particular, an aspherical surface is formed on the first lens having positive refractive power arranged on the most object side of the third lens group, and the above conditional expression (1) is satisfied, so that the third lens group and the fourth lens group By optimizing the ratio of the focal length to the lens group, various aberrations that become noticeable in the entire zooming range as the aperture ratio is increased can be favorably corrected to achieve high resolution. Furthermore, when the conditional expression (2) is satisfied, it becomes possible to use glass lenses for the first lens and the second lens of the third lens group, and it is possible to perform better chromatic aberration correction. In addition, by satisfying the conditional expression (3), high optical performance can be maintained without deteriorating the workability of the first lens of the third lens group.

  Embodiments of the zoom lens according to the present invention will be described below in detail with reference to the drawings. In addition, this invention is not limited by the following examples.

FIG. 1 is a cross-sectional view along the optical axis showing the configuration of the zoom lens according to the first embodiment. The zoom lens includes a first lens group G ₁₁ having a positive refractive power, a second lens group G ₁₂ having a negative refractive power, and a third lens group having a positive refractive power in order from an object side (not shown). G ₁₃ , a fourth lens group G ₁₄ having a positive refractive power, and a fifth lens group G ₁₅ having a negative refractive power are arranged.

A second lens group G ₁₂ between the third lens group G _13, an aperture stop STP is disposed to define a predetermined diameter. Further, a cover glass CG is disposed between the fifth lens group G ₁₅ and the image plane IMG. Note that the light receiving surface of the solid-state imaging device is disposed on the image plane IMG.

The first lens group G ₁₁ includes, in order from the object side, a negative lens L _111, a positive lens L _112, a positive lens L _113, is formed are disposed. The negative lens L ₁₁₁ and the positive lens L ₁₁₂ are cemented.

The second lens group G ₁₂ includes, in order from the object side, a negative lens L _121, a negative lens L _122, a positive lens L _123, are configured arranged. The negative lens L ₁₂₂ and the positive lens L ₁₂₃ are cemented.

The third lens group G ₁₃ includes, in order from the object side, a positive lens L ₁₃₁ (first lens), a negative lens L ₁₃₂ (second lens), are configured arranged. Aspherical surfaces are formed on both surfaces of the positive lens _L131 . The negative lens L ₁₃₂ is a negative meniscus lens having a convex surface facing the object side.

The fourth lens group G ₁₄ includes, in order from the object side, a positive lens L _141, a negative lens L _142, is formed are disposed. An aspheric surface is formed on the object side surface of the positive lens L ₁₄₁ . Further, the positive lens L ₁₄₁ and the negative lens L ₁₄₂ are cemented.

The fifth lens group G ₁₅ includes a negative lens L ₁₅₁ and a positive lens L ₁₅₂ arranged in order from the object side. Aspherical surfaces are formed on both surfaces of the positive lens _L152 .

In this zoom lens, the first lens group G ₁₁ , the aperture stop STP, the third lens group G ₁₃ , and the fifth lens group G ₁₅ are always fixed. Then, the magnification to the telephoto end from the wide-angle end by moving toward the image side from the object side along the second lens group G ₁₂ to the optical axis. Further, correction and focusing of the image plane variation due to zooming by moving along the fourth lens group G ₁₄ to the optical axis.

  Various numerical data related to the zoom lens according to Example 1 will be described below.

Focal length of the entire zoom lens = 15.0 (wide-angle end) to 27.4 (intermediate position) to 50.0 (telephoto end)
F number (Fno.) = 1.41 (wide-angle end) to 1.41 (intermediate position) to 1.41 (telephoto end)
Half angle of view (ω) = 17.31 (wide-angle end) to 9.28 (intermediate position) to 5.00 (telephoto end)

(Lens data)
r ₁ = 52.701
d ₁ = 1.00 nd ₁ = 1.84666 νd ₁ = 23.78
r ₂ = 37.494
d ₂ = 5.45 nd ₂ = 1.49700 νd ₂ = 81.54
r ₃ = -209.348
d ₃ = 0.15
r ₄ = 46.627
d ₄ = 2.98 nd ₃ = 1.61800 νd ₃ = 63.39
r ₅ = 173.394
d ₅ = D (5) (variable)
r ₆ = -95.368
d ₆ = 0.70 nd ₄ = 1.90366 νd ₄ = 31.31
r ₇ = 21.124
d ₇ = 2.76
r ₈ = -25.242
d ₈ = 0.60 nd ₅ = 1.51633 νd ₅ = 64.14
r ₉ = 24.624
d ₉ = 1.90 nd ₆ = 1.95906 νd ₆ = 17.47
r ₁₀ = 163.058
d ₁₀ = D (10) (variable)
r ₁₁ = ∞ (aperture stop)
d ₁₁ = 0.80
r ₁₂ = 15.000 (aspherical surface)
d ₁₂ = 3.80 nd ₇ = 1.59201 νd ₇ = 67.02
r ₁₃ = -162.259 (aspherical surface)
d ₁₃ = 5.82
r ₁₄ = 57.534
d ₁₄ = 0.80 nd ₈ = 1.92286 νd ₈ = 18.90
r ₁₅ = 21.153
d ₁₅ = D (15) (variable)
r ₁₆ = 15.452 (aspherical surface)
d ₁₆ = 4.30 nd ₉ = 1.76802 νd ₉ = 49.24
r ₁₇ = -21.694
d ₁₇ = 0.60 nd ₁₀ = 1.72825 νd ₁₀ = 28.32
r ₁₈ = -77.352
d ₁₈ = D (18) (variable)
r ₁₉ = 11.752
d ₁₉ = 1.90 nd ₁₁ = 1.74077 νd ₁₁ = 27.76
r ₂₀ = 6.977
d ₂₀ = 1.77
r ₂₁ = 15.882 (aspherical surface)
d ₂₁ = 2.20 nd ₁₂ = 1.82115 νd ₁₂ = 24.06
r ₂₂ = 23.347 (aspherical surface)
d ₂₂ = 1.00
r ₂₃ = ∞
d ₂₃ = 2.50 nd ₁₃ = 1.51633 νd ₁₃ = 64.14
r ₂₄ = ∞
d ₂₄ = 4.64
r ₂₅ = ∞ (image plane)

Cone coefficient (k) and aspheric coefficient (A, B, C, D)
(Twelfth surface)
k = -0.5866,
A = -3.61877 × 10 ⁻⁶ , B = −7.61256 × 10 ⁻⁸ ,
C = 3.33045 × 10 ⁻¹⁰ , D = −6.25838 × 10 ⁻¹²
(13th page)
k = 83.9072,
A = 1.65979 × 10 ⁻⁵ , B = −7.339338 × 10 ⁻⁸ ,
C = -3.64627 × 10 ⁻¹¹ , D = −2.88792 × 10 ⁻¹²
(16th surface)
k = -1.3890,
A = 1.59736 × 10 ⁻⁵ , B = 1.27294 × 10 ⁻⁷ ,
C = -4.84226 × 10 ^-9 , D = 4.27025 × 10 ^-11
(21st surface)
k = 2.8196,
A = -1.79940 × 10 ^-5 , B = -2.89823 × 10 ^-6 ,
C = 7.03458 × 10 ^-8 , D = -5.72816 × 10 ^-9
(Twenty-second surface)
k = 2.8897,
A = -9.52100 × 10 ^-6 , B = 1.32989 × 10 ^-6 ,
C = -2.79234 × 10 ⁻⁷ , D = −8.990638 × 10 ⁻¹⁰

(Scaled data)
Wide angle end Intermediate position Telephoto end
D (5) 7.841 18.228 27.201
D (10) 21.539 11.153 2.179
D (15) 4.744 4.256 6.630
D (18) 2.685 3.174 0.800

(Numerical values related to conditional expression (1))
F3 (the focal length of the third lens group G ₁₃₎ = 39.041
F4 (focal length of the fourth lens group G ₁₄₎ = 16.828
| F3 / F4 | = 2.32

(Numerical value related to conditional expression (2))
νdG3L1 (abbe number of the positive lens L ₁₃₁ (first lens) with respect to the d-line) = 67.02
νdG3L2 (abbe number of d-line of negative lens L ₁₃₂ (second lens)) = 18.90
νdG3L1 / νdG3L2 = 3.546

(Numerical values related to conditional expression (3))
rp (Paraxial radius of curvature of object side surface of positive lens L ₁₃₁ (first lens)) = 15,000
f31 (focal length of positive lens L ₁₃₁ (first lens)) = 23.38
| Rp / f31 | = 0.642

  FIG. 2 is a diagram illustrating various aberrations of the zoom lens according to Example 1 with respect to the d-line (λ = 587.56 nm). In the astigmatism diagrams, S and M represent aberrations with respect to the sagittal image surface and the meridional image surface, respectively.

FIG. 3 is a cross-sectional view along the optical axis showing the configuration of the zoom lens according to the second embodiment. In this zoom lens, in order from the object side (not shown), a first lens group G ₂₁ having a positive refractive power, a second lens group G ₂₂ having a negative refractive power, and a third lens group having a positive refractive power. G ₂₃ , a fourth lens group G ₂₄ having a positive refractive power, and a fifth lens group G ₂₅ having a negative refractive power are arranged.

An aperture stop STP that defines a predetermined aperture is disposed between the second lens group G ₂₂ and the third lens group G ₂₃ . Further, a cover glass CG is disposed between the fifth lens group G ₂₅ and the image plane IMG. Note that the light receiving surface of the solid-state imaging device is disposed on the image plane IMG.

The first lens group G ₂₁ includes a negative lens L ₂₁₁ , a positive lens L _212, and a positive lens L ₂₁₃ arranged in this order from the object side. The negative lens L ₂₁₁ and the positive lens L ₂₁₂ are cemented.

The second lens group G ₂₂ includes, in order from the object side, a negative lens L _221, a negative lens L _222, a positive lens L _223, are configured arranged. The negative lens L ₂₂₂ and the positive lens L ₂₂₃ are cemented.

The third lens group G ₂₃ includes, in order from the object side, a positive lens L ₂₃₁ (first lens), a negative lens L ₂₃₂ (second lens), are configured arranged. Aspherical surfaces are formed on both surfaces of the positive lens _L231 . The negative lens L ₂₃₂ is a negative meniscus lens having a convex surface facing the object side.

The fourth lens group G ₂₄ includes a positive lens L ₂₄₁ and a negative lens L ₂₄₂ arranged in this order from the object side. An aspherical surface is formed on the object side surface of the positive lens L ₂₄₁ . Further, the positive lens L ₂₄₁ and the negative lens L ₂₄₂ are cemented.

The fifth lens group G ₂₅ includes a negative lens L ₂₅₁ and a positive lens L ₂₅₂ arranged in this order from the object side. Aspherical surfaces are formed on both surfaces of the positive lens _L252 .

In this zoom lens, the first lens group G ₂₁ , the aperture stop STP, the third lens group G ₂₃ , and the fifth lens group G ₂₅ are always fixed. Then, the magnification to the telephoto end from the wide-angle end by moving toward the image side from the object side along the second lens group G ₂₂ to the optical axis. Further, correction and focusing of the image plane variation due to zooming by moving along the fourth lens group G ₂₄ to the optical axis.

  Various numerical data related to the zoom lens according to Example 2 will be described below.

Focal length of the entire zoom lens = 15.0 (wide-angle end) to 27.4 (intermediate position) to 50.0 (telephoto end)
F number (Fno.) = 1.42 (wide-angle end) to 1.44 (intermediate position) to 1.44 (telephoto end)
Half angle of view (ω) = 17.19 (wide-angle end) to 9.23 (intermediate position) to 5.00 (telephoto end)

(Lens data)
r ₁ = 57.066
d ₁ = 1.00 nd ₁ = 1.84666 νd ₁ = 23.78
r ₂ = 39.550
d ₂ = 5.11 nd ₂ = 1.49700 νd ₂ = 81.54
r ₃ = -245.030
d ₃ = 0.15
r ₄ = 48.097
d ₄ = 3.05 nd ₃ = 1.61800 νd ₃ = 63.39
r ₅ = 222.471
d ₅ = D (5) (variable)
r ₆ = -143.269
d ₆ = 0.70 nd ₄ = 1.90366 νd ₄ = 31.31
r ₇ = 20.787
d ₇ = 3.02
r ₈ = -22.781
d ₈ = 0.60 nd ₅ = 1.51633 νd ₅ = 64.14
r ₉ = 27.841
d ₉ = 1.90 nd ₆ = 1.95906 νd ₆ = 17.47
r ₁₀ = 486.697
d ₁₀ = D (10) (variable)
r ₁₁ = ∞ (aperture stop)
d ₁₁ = 0.80
r ₁₂ = 15.214 (aspherical surface)
d ₁₂ = 3.80 nd ₇ = 1.61881 νd ₇ = 63.85
r ₁₃ = -300.983 (aspherical surface)
d ₁₃ = 5.32
r ₁₄ = 70.442
d ₁₄ = 0.80 nd ₈ = 1.92286 νd ₈ = 18.90
r ₁₅ = 21.752
d ₁₅ = D (15) (variable)
r ₁₆ = 13.489 (aspherical surface)
d ₁₆ = 4.30 nd ₉ = 1.76802 νd ₉ = 49.24
r ₁₇ = -25.255
d ₁₇ = 0.60 nd ₁₀ = 1.72825 νd ₁₀ = 28.32
r ₁₈ = -49.793
d ₁₈ = D (18) (variable)
r ₁₉ = 17.183
d ₁₉ = 1.90 nd ₁₁ = 1.74077 νd ₁₁ = 27.76
r ₂₀ = 7.215
d ₂₀ = 1.76
r ₂₁ = 17.712 (aspherical surface)
d ₂₁ = 2.20 nd ₁₂ = 1.82115 νd ₁₂ = 24.06
r ₂₂ = 31.109 (aspherical surface)
d ₂₂ = 1.00
r ₂₃ = ∞
d ₂₃ = 2.50 nd ₁₃ = 1.51633 νd ₁₃ = 64.14
r ₂₄ = ∞
d ₂₄ = 5.58
r ₂₅ = ∞ (image plane)

Cone coefficient (k) and aspheric coefficient (A, B, C, D)
(Twelfth surface)
k = -0.6090,
A = -4.19699 × 10 ⁻⁶ , B = −9.56196 × 10 ⁻⁸ ,
C = 6.43385 × 10 ⁻¹⁰ , D = −8.48882 × 10 ⁻¹²
(13th page)
k = 13.6295,
A = 4.91055 × 10 ^-6 , B = -2.78020 × 10 ^-8 ,
C = -4.26331 × 10 ⁻¹¹ , D = −3.778172 × 10 ⁻¹²
(16th surface)
k = -1.4320,
A = -1.94318 × 10 ⁻⁵ , B = 2.72495 × 10 ⁻⁸ ,
C = -3.03937 × 10 ^-9 , D = 3.38298 × 10 ^-11
(21st surface)
k = 3.3539,
A = -2.50356 × 10 ⁻⁵ , B = 4.03139 × 10 ⁻⁷ ,
C = -2.52553 × 10 ^-8 , D = -4.37056 × 10 ^-9
(Twenty-second surface)
k = 4.9321,
A = -3.78714 × 10 ⁻⁶ , B = 3.63191 × 10 ⁻⁶ ,
C = -2.99492 × 10 ^-7 , D = -5.48636 × 10 ^-10

(Scaled data)
Wide angle end Intermediate position Telephoto end
D (5) 7.817 18.771 28.099
D (10) 22.378 11.424 2.096
D (15) 4.317 3.910 5.389
D (18) 1.872 2.279 0.800

(Numerical values related to conditional expression (1))
F3 (the focal length of the third lens group G ₂₃₎ = 42.458
F4 (focal length of the fourth lens group G ₂₄₎ = 14.165
| F3 / F4 | = 2.997

(Numerical value related to conditional expression (2))
νdG3L1 (abbe number of the positive lens L ₂₃₁ (first lens) with respect to the d-line) = 63.85
νdG3L2 (abbe number of d-line of negative lens L ₂₃₂ (second lens)) = 18.90
νdG3L1 / νdG3L2 = 3.378

(Numerical values related to conditional expression (3))
rp (Paraxial radius of curvature of object side surface of positive lens L ₂₃₁ (first lens)) = 15.214
f31 (focal length of positive lens L ₂₃₁ (first lens)) = 23.511
| Rp / f31 | = 0.647

  FIG. 4 is a diagram illustrating various aberrations of the zoom lens according to Example 2 with respect to the d-line (λ = 587.56 nm). In the astigmatism diagrams, S and M represent aberrations with respect to the sagittal image surface and the meridional image surface, respectively.

FIG. 5 is a cross-sectional view along the optical axis showing the configuration of the zoom lens according to the third embodiment. The zoom lens includes a first lens group G ₃₁ having a positive refractive power, a second lens group G ₃₂ having a negative refractive power, and a third lens group having a positive refractive power in order from an object side (not shown). G ₃₃ , a fourth lens group G ₃₄ having a positive refractive power, and a fifth lens group G ₃₅ having a negative refractive power are arranged.

An aperture stop STP that defines a predetermined aperture is disposed between the second lens group G ₃₂ and the third lens group G ₃₃ . A cover glass CG is disposed between the fifth lens group G ₃₅ and the image plane IMG. Note that the light receiving surface of the solid-state imaging device is disposed on the image plane IMG.

The first lens group G ₃₁ includes a negative lens L ₃₁₁ , a positive lens L _312, and a positive lens L ₃₁₃ arranged in order from the object side. The negative lens L ₃₁₁ and the positive lens L ₃₁₂ are cemented.

The second lens group G ₃₂ includes, in order from the object side, a negative lens L _321, a negative lens L _322, a positive lens L _323, are configured arranged. The negative lens L ₃₂₂ and the positive lens L ₃₂₃ are cemented.

The third lens group G ₃₃ includes a positive lens L ₃₃₁ (first lens) and a negative lens L ₃₃₂ (second lens) arranged in order from the object side. Aspherical surfaces are formed on both surfaces of the positive lens _L331 . The negative lens L ₃₃₂ is a negative meniscus lens having a convex surface facing the object side.

The fourth lens group G ₃₄ includes a positive lens L ₃₄₁ and a negative lens L ₃₄₂ arranged in this order from the object side. An aspherical surface is formed on the object side surface of the positive lens L ₃₄₁ . The positive lens L ₃₄₁ and the negative lens L ₃₄₂ are cemented.

The fifth lens group G ₃₅ includes a negative lens L ₃₅₁ and a positive lens L ₃₅₂ arranged in this order from the object side. Aspherical surfaces are formed on both surfaces of the positive lens _L352 .

In this zoom lens, the first lens group G ₃₁ , the aperture stop STP, the third lens group G ₃₃ , and the fifth lens group G ₃₅ are fixed. Then, the magnification to the telephoto end from the wide-angle end by moving toward the image side from the object side along the second lens group G ₃₂ to the optical axis. Further, correction and focusing of the image plane variation due to zooming by moving along the fourth lens group G ₃₄ to the optical axis.

  Various numerical data relating to the zoom lens according to Example 3 will be described below.

Focal length of the entire zoom lens = 15.0 (wide-angle end) to 27.4 (intermediate position) to 50.0 (telephoto end)
F number (Fno.) = 1.42 (wide-angle end) to 1.44 (intermediate position) to 1.44 (telephoto end)
Half angle of view (ω) = 17.15 (wide-angle end) to 9.22 (intermediate position) to 5.00 (telephoto end)

(Lens data)
r ₁ = 55.770
d ₁ = 1.00 nd ₁ = 1.84666 νd ₁ = 23.78
r ₂ = 38.896
d ₂ = 5.06 nd ₂ = 1.49700 νd ₂ = 81.54
r ₃ = -197.191
d ₃ = 0.15
r ₄ = 47.173
_{d 4 = 2.70 nd 3 = 1.61800} νd 3 = 63.39
r ₅ = 132.026
d ₅ = D (5) (variable)
r ₆ = 205.465
d ₆ = 0.70 nd ₄ = 1.90366 νd ₄ = 31.31
r ₇ = 19.963
d ₇ = 3.80
r ₈ = -19.359
d ₈ = 0.60 nd ₅ = 1.51633 νd ₅ = 64.14
r ₉ = 35.304
d ₉ = 1.90 nd ₆ = 1.95906 νd ₆ = 17.47
r ₁₀ = -414.596
d ₁₀ = D (10) (variable)
r ₁₁ = ∞ (aperture stop)
d ₁₁ = 0.80
r ₁₂ = 16.621 (aspherical surface)
d ₁₂ = 3.80 nd ₇ = 1.61881 νd ₇ = 63.85
r ₁₃ = -115.603 (aspherical surface)
d ₁₃ = 4.35
r ₁₄ = 69.820
d ₁₄ = 0.80 nd ₈ = 1.92286 νd ₈ = 18.90
r ₁₅ = 21.887
d ₁₅ = D (15) (variable)
r ₁₆ = 14.112 (aspherical surface)
d ₁₆ = 4.30 nd ₉ = 1.76802 νd ₉ = 49.24
r ₁₇ = -23.853
d ₁₇ = 0.60 nd ₁₀ = 1.72825 νd ₁₀ = 28.32
r ₁₈ = -43.429
d ₁₈ = D (18) (variable)
r ₁₉ = 20.742
d ₁₉ = 1.90 nd ₁₁ = 1.71736 νd ₁₁ = 29.50
r ₂₀ = 6.937
d ₂₀ = 1.71
r ₂₁ = 16.656 (aspherical surface)
d ₂₁ = 2.20 nd ₁₂ = 1.82115 νd ₁₂ = 24.06
r ₂₂ = 38.845 (aspherical surface)
d ₂₂ = 1.00
r ₂₃ = ∞
d ₂₃ = 2.50 nd ₁₃ = 1.51633 νd ₁₃ = 64.14
r ₂₄ = ∞
d ₂₄ = 6.16
r ₂₅ = ∞ (image plane)

Cone coefficient (k) and aspheric coefficient (A, B, C, D)
(Twelfth surface)
k = -0.5439,
A = -1.48046 × 10 ^-6 , B = -6.19350 × 10 ^-8 ,
C = 3.86077 × 10 ⁻¹⁰ , D = −5.71423 × 10 ⁻¹²
(13th page)
k = -0.2573,
A = 1.81004 × 10 ^-5 , B = -2.58080 × 10 ^-8 ,
C = 1.42210 × 10 ⁻¹⁰ , D = −3.82567 × 10 ⁻¹²
(16th surface)
k = -1.3867,
A = -1.71342 × 10 ⁻⁵ , B = 1.18333 × 10 ⁻⁸ ,
C = -1.77195 × 10 ⁻⁹ , D = 1.91952 × 10 ⁻¹¹
(21st surface)
k = 4.4474,
A = 2.05738 × 10 ⁻⁵ , B = -1.83122 × 10 ⁻⁶ ,
C = 5.50981 × 10 ^-8 , D = -6.10561 × 10 ^-9
(Twenty-second surface)
k = 24.9779,
A = 4.51606 × 10 ⁻⁵ , B = -1.43913 × 10 ⁻⁷ ,
C = -1.36900 × 10 ^-7 , D = -4.15559 × 10 ^-9

(Scaled data)
Wide angle end Intermediate position Telephoto end
D (5) 6.002 17.936 28.123
D (10) 24.170 12.236 2.050
D (15) 4.283 4.010 5.496
D (18) 2.012 2.286 0.800

(Numerical values related to conditional expression (1))
F3 (the focal length of the third lens group G ₃₃₎ = 45.653
F4 (focal length of the fourth lens group G ₃₄₎ = 14.267
| F3 / F4 | = 3.2

(Numerical value related to conditional expression (2))
νdG3L1 (abbe number of the positive lens L ₃₃₁ (first lens) with respect to the d-line) = 63.85
νdG3L2 (abbe number of d-line of negative lens L ₃₃₂ (second lens)) = 18.90
νdG3L1 / νdG3L2 = 3.378

(Numerical values related to conditional expression (3))
rp (Paraxial radius of curvature of object side surface of positive lens L ₃₃₁ (first lens)) = 16.621
f31 (focal length of positive lens L ₃₃₁ (first lens)) = 23.744
| Rp / f31 | = 0.7

  FIG. 6 is a diagram of various aberrations of the zoom lens according to Example 3 with respect to the d-line (λ = 587.56 nm). In the astigmatism diagrams, S and M represent aberrations with respect to the sagittal image surface and the meridional image surface, respectively.

FIG. 7 is a cross-sectional view along the optical axis showing the configuration of the zoom lens according to the fourth example. The zoom lens includes a first lens group G ₄₁ having a positive refractive power, a second lens group G ₄₂ having a negative refractive power, and a third lens group having a positive refractive power in order from an object side (not shown). G ₄₃ , a fourth lens group G ₄₄ having a positive refractive power, and a fifth lens group G ₄₅ having a negative refractive power are arranged.

A second lens group G ₄₂ between the third lens group G _43, an aperture stop STP is disposed to define a predetermined diameter. Further, a cover glass CG is disposed between the fifth lens group G ₄₅ and the image plane IMG. Note that the light receiving surface of the solid-state imaging device is disposed on the image plane IMG.

The first lens group G ₄₁ includes, in order from the object side, a negative lens L _411, a positive lens L _412, a positive lens L _413, is formed are disposed. The negative lens L ₄₁₁ and the positive lens L ₄₁₂ are cemented.

The second lens group G ₄₂ includes, in order from the object side, a negative lens L _421, a negative lens L _422, a positive lens L _423, are configured arranged. The negative lens L ₄₂₂ and the positive lens L ₄₂₃ are cemented.

The third lens group G ₄₃ includes a positive lens L ₄₃₁ (first lens) and a negative lens L ₄₃₂ (second lens) arranged in this order from the object side. Aspherical surfaces are formed on both surfaces of the positive lens _L431 . The negative lens L ₄₃₂ is a negative meniscus lens having a convex surface facing the object side.

The fourth lens group G ₄₄ includes, in order from the object side, a positive lens L _441, a negative lens L _442, is formed are disposed. On the object side surface of the positive lens L ₄₄₁ , an aspheric surface is formed. Further, the positive lens L ₄₄₁ and the negative lens L ₄₄₂ are cemented.

The fifth lens group G ₄₅ includes a negative lens L ₄₅₁ and a positive lens L ₄₅₂ arranged in this order from the object side. Aspherical surfaces are formed on both surfaces of the positive lens L ₄₅₂ .

In this zoom lens, the first lens group G ₄₁ , the aperture stop STP, the third lens group G ₄₃ , and the fifth lens group G ₄₅ are fixed. Then, the magnification to the telephoto end from the wide-angle end by moving toward the image side from the object side along the second lens group G ₄₂ to the optical axis. Further, correction and focusing of the image plane variation due to zooming by moving along the fourth lens group G ₄₄ to the optical axis.

  Various numerical data relating to the zoom lens according to Example 4 will be described below.

Focal length of the entire zoom lens = 15.0 (wide-angle end) to 27.4 (intermediate position) to 50.0 (telephoto end)
F number (Fno.) = 1.42 (wide-angle end) to 1.44 (intermediate position) to 1.44 (telephoto end)
Half angle of view (ω) = 17.15 (wide-angle end) to 9.21 (intermediate position) to 5.00 (telephoto end)

(Lens data)
r ₁ = 64.654
d ₁ = 1.00 nd ₁ = 1.84666 νd ₁ = 23.78
r ₂ = 42.859
d ₂ = 4.83 nd ₂ = 1.49700 νd ₂ = 81.54
r ₃ = -188.181
d ₃ = 0.15
r ₄ = 46.926
d ₄ = 3.02 nd ₃ = 1.61800 νd ₃ = 63.39
r ₅ = 214.595
d ₅ = D (5) (variable)
r ₆ = -159.632
d ₆ = 0.70 nd ₄ = 1.90366 νd ₄ = 31.31
r ₇ = 21.034
d ₇ = 3.04
r ₈ = -22.653
d ₈ = 0.60 nd ₅ = 1.51633 νd ₅ = 64.14
r ₉ = 28.525
d ₉ = 1.90 nd ₆ = 1.95906 νd ₆ = 17.47
r ₁₀ = 619.032
d ₁₀ = D (10) (variable)
r ₁₁ = ∞ (aperture stop)
d ₁₁ = 0.80
r ₁₂ = 15.492 (aspherical surface)
d ₁₂ = 3.80 nd ₇ = 1.61881 νd ₇ = 63.85
r ₁₃ = 461.986 (aspherical surface)
d ₁₃ = 4.96
r ₁₄ = 64.368
d ₁₄ = 0.80 nd ₈ = 1.95906 νd ₈ = 17.47
r ₁₅ = 25.648
d ₁₅ = D (15) (variable)
r ₁₆ = 13.369 (aspherical surface)
d ₁₆ = 4.30 nd ₉ = 1.76802 νd ₉ = 49.24
r ₁₇ = -25.681
d ₁₇ = 0.60 nd ₁₀ = 1.72825 νd ₁₀ = 28.32
r ₁₈ = -49.936
d ₁₈ = D (18) (variable)
r ₁₉ = 21.590
d ₁₉ = 1.90 nd ₁₁ = 1.74077 νd ₁₁ = 27.76
r ₂₀ = 7.666
d ₂₀ = 1.63
r ₂₁ = 22.153 (aspherical surface)
d ₂₁ = 2.20 nd ₁₂ = 1.82115 νd ₁₂ = 24.06
r ₂₂ = 45.276 (aspherical surface)
d ₂₂ = 1.00
r ₂₃ = ∞
d ₂₃ = 2.50 nd ₁₃ = 1.51633 νd ₁₃ = 64.14
r ₂₄ = ∞
d ₂₄ = 6.63
r ₂₅ = ∞ (image plane)

Cone coefficient (k) and aspheric coefficient (A, B, C, D)
(Twelfth surface)
k = -0.6311,
A = -4.15876 × 10 ⁻⁶ , B = -1.37883 × 10 ⁻⁷ ,
C = 4.15271 × 10 ⁻¹⁰ , D = -1.52593 × 10 ⁻¹¹
(13th page)
k = -100.0000,
A = -3.24557 × 10 ^-6 , B = -3.64173 × 10 ^-8 ,
C = -7.92874 × 10 ^-10 , D = -5.83352 × 10 ^-12
(16th surface)
k = -1.4459,
A = -2.09475 × 10 ^-5 , B = -8.45495 × 10 ^-8 ,
C = -1.17046 × 10 ^-9 , D = 2.39402 × 10 ^-11
(21st surface)
k = 4.1333,
A = 5.12895 × 10 ^-5 , B = 1.63393 × 10 ^-6 ,
C = 2.00177 × 10 ⁻⁸ , D = −4.775306 × 10 ⁻⁹
(Twenty-second surface)
k = 10.1512,
A = 9.62421 × 10 ⁻⁵ , B = 2.29371 × 10 ⁻⁶ ,
C = -7.74967 × 10 ^-8 , D = -4.41659 × 10 ^-9

(Scaled data)
Wide angle end Intermediate position Telephoto end
D (5) 7.366 18.632 28.186
D (10) 22.908 11.642 2.088
D (15) 4.228 3.829 5.038
D (18) 1.611 2.010 0.800

(Numerical values related to conditional expression (1))
F3 (the focal length of the third lens group G ₄₃₎ = 42.7
F4 (focal length of the fourth lens group G ₄₄₎ = 14.079
| F3 / F4 | = 3.033

(Numerical value related to conditional expression (2))
νdG3L1 (abbe number with respect to d-line of positive lens L ₄₃₁ (first lens)) = 63.85
νdG3L2 (abbe number of the negative lens L ₄₃₂ (second lens) with respect to the d-line) = 17.47
νdG3L1 / νdG3L2 = 3.655

(Numerical values related to conditional expression (3))
rp (Paraxial radius of curvature of object side surface of positive lens L ₄₃₁ (first lens)) = 15.492
f31 (focal length of positive lens L ₄₃₁ (first lens)) = 25.82
| Rp / f31 | = 0.6

  FIG. 8 is a diagram of various aberrations of the zoom lens according to Example 4 with respect to the d-line (λ = 587.56 nm). In the astigmatism diagrams, S and M represent aberrations with respect to the sagittal image surface and the meridional image surface, respectively.

In the numerical data in each of the above embodiments, r ₁ , r ₂ ,... Are the curvature radii of the lenses and the diaphragm surface, and d ₁ , d ₂ ,. Thickness or spacing between them, nd ₁ , nd ₂ ,... Is the refractive index with respect to d-line (λ = 587.56 nm) of each lens, νd ₁ , νd ₂ ,. The Abbe number with respect to the d-line (λ = 587.56 nm) is shown. The unit of length is all “mm”, and the unit of angle is “°”.

  In addition, each of the aspheric shapes has a depth of the aspheric surface Z, a height in the direction perpendicular to the optical axis y, a paraxial radius of curvature R, a cone coefficient k, 4th order, 6th order, 8th order, When the 10th-order aspheric coefficients are A, B, C, and D, respectively, and the traveling direction of light is positive, it is expressed by the following equation.

  As described above, the zoom lens of each embodiment described above has the above-described configuration, so that a bright image can be obtained in the entire zoom range and various aberrations can be effectively corrected over the entire zoom range. Thus, it is possible to maintain a high optical performance and to have a resolving power that can be applied to a solid-state imaging device having a high pixel. In particular, by satisfying the above conditional expressions, it is possible to effectively correct various aberrations over the entire zooming range while the F-number over the entire zooming range is a large aperture ratio of about 1.4. It is possible to realize a small and lightweight zoom lens that maintains high optical performance and has high resolution that can be applied to a solid-state imaging device having 3 million pixels or more.

  As described above, the zoom lens according to the present invention is useful for monitoring cameras that monitor nighttime and dimly lit places, and is particularly suitable for traffic monitoring cameras that require clear evidence images regardless of day or night.

G ₁₁ , G ₂₁ , G ₃₁ , G ₄₁ 1st lens group G ₁₂ , G ₂₂ , G ₃₂ , G ₄₂ 2nd lens group G ₁₃ , G ₂₃ , G ₃₃ , G ₄₃ 3rd lens group G ₁₄ , G ₂₄ , G ₃₄ , G ₄₄ fourth lens group G ₁₅ , G ₂₅ , G ₃₅ , G ₄₅ fifth lens group L ₁₁₁ , L ₁₂₁ , L ₁₂₂ , L ₁₃₂ , L ₁₄₂ , L ₁₅₁ , L ₂₁₁ , L ₂₂₁ , L ₂₂₂ , _L232 , _L242 , _L251 , _L311 , _L321 , _L322 , _L332 , _L342 , _L351 , _L411 , _L421 , _L422 , _L432 , _L442 , _L451 negative lens _{L112 , L 113, L 123, L} 131, L 141, L 152, L 212, L 213, L 223, L 231, L 241, L 252, L 312, L 313, L 323, L 331, L 341, L ₃₅₂ , L ₄₁₂ , L ₄₁₃ , L ₄₂₃ , L ₄₃₁ , L ₄₄₁ , L ₄₅₂ Positive lens STP Aperture stop CG Cover glass IMG Image plane

Claims (3)

A first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a positive refractive power, which are arranged in order from the object side. A fourth lens group, and a fifth lens group having negative refractive power,
The third lens group includes a first lens having a positive refractive power and an aspheric surface formed on at least one surface, and a meniscus having a negative refractive power with a convex surface facing the object side. A second lens having a shape,
The first lens group, the third lens group, and the fifth lens group are fixed, and the second lens group is moved from the object side to the image plane side along the optical axis to move from the wide-angle end to the telephoto end. , And
By moving the fourth lens group along the optical axis, correction of image plane variation accompanying focusing and focusing are performed.
A zoom lens that satisfies the following conditional expression:
(1) 2.2 <| F3 / F4 | <3.5
(2) νdG3L1 / νdG3L2> 2.8
Where F3 is the focal length of the third lens group, F4 is the focal length of the fourth lens group, νdG3L1 is the Abbe number of the third lens group with respect to the d-line, and νdG3L2 is the third lens group. The Abbe number of the second lens with respect to the d line is shown. The zoom lens according to claim 1, wherein the following conditional expression is satisfied.
(3) 0.5 <| rp / f31 | <0.8
Here, rp represents the paraxial radius of curvature of the object side surface of the first lens of the third lens group, and f31 represents the focal length of the first lens of the third lens group.   The zoom lens according to claim 1, wherein an aperture stop is disposed between the second lens group and the third lens group.

Images