Imaging lens composed of six optical elements

Abstract

A compact low-profile low-cost imaging lens with an F-value of 2.4 or less which offers a wide field of view and corrects aberrations properly. It includes elements arranged from an object side: a first positive lens having a convex surface on the object side as a first optical element; a second negative lens having a concave surface on an image side as a second optical element; a third positive lens as a third optical element; a fourth negative lens as a double-sided aspheric lens having a convex surface on the image side as a fourth optical element; and a fifth lens as a double-sided aspheric lens having a concave surface on the image side as a fifth optical element. As a sixth optical element, one aberration correction optical element as a double-sided aspheric element with virtually no refractive power is located between the first lens and the image plane.

Claims

1. An imaging lens composed of six optical elements which forms an image of an object on a solid-state image sensor, in which the elements are arranged in order from an object side to an image side, comprising: a first lens with positive refractive power having a convex surface on the object side as a first optical element; a second lens with negative refractive power having a concave surface on the image side as a second optical element; a third lens with positive refractive power as a third optical element; a fourth lens with negative refractive power as a double-sided aspheric lens having a convex surface on the image side as a fourth optical element; and a fifth lens as a double-sided aspheric lens having a concave surface on the image side as a fifth optical element, wherein as a sixth optical element, one aberration correction optical element as a double-sided aspheric element which has virtually no refractive power is located between the first lens and an image plane.

2. The imaging lens composed of six optical elements according to claim 1, wherein the aberration correction optical element is located between the first lens and the second lens.

3. The imaging lens composed of six optical elements according to claim 1, wherein the aberration correction optical element is located between the second lens and the third lens.

4. The imaging lens composed of six optical elements according to claim 1, wherein the aberration correction optical element is located between the third lens and the fourth lens.

5. The imaging lens composed of six optical elements according to claim 1, wherein the aberration correction optical element is located between the fourth lens and the fifth lens.

6. The imaging lens composed of six optical elements according to claim 1, wherein the aberration correction optical element is located between the fifth lens and the image plane.

7. The imaging lens composed of six optical elements according to claim 1, wherein conditional expressions (1) to (3) below are satisfied:
0.05<TN/f<0.5   (1)
0.03<dN/f<0.1   (2)
40<νdN<70   (3) where TN: distance on an optical axis between lenses where the aberration correction optical element is located, dN: thickness of the aberration correction optical element on the optical axis, f: focal length of an overall optical system of the imaging lens, and νdN: Abbe number of the aberration correction optical element at d-ray.

8. The imaging lens composed of six optical elements according to claim 1, wherein the fifth lens is a meniscus lens having a concave surface on the image side which has the weakest positive or negative refractive power among the optical elements with refractive power, and the object-side and image-side surfaces of the fifth lens are aspheric surfaces with pole-change points off an optical axis.

9. The imaging lens composed of six optical elements according to claim 1, wherein conditional expressions (4) and (5) below are satisfied:
0.08<T23/f<0.2   (4)
0.03<d2/f<0.08   (5) where T23: air gap on an optical axis between the second lens and the third lens, d2: thickness of the second lens on the optical axis, and f: focal length of an overall optical system of the imaging lens.

10. The imaging lens composed of six optical elements according to claim 1, wherein a conditional expression (6) below is satisfied:
1.0<f12/f<1.6   (6) where f12: composite focal length of the first lens and the second lens, and f: focal length of an overall optical system of the imaging lens.

11. The imaging lens composed of six optical elements according to claim 1, wherein a conditional expression (7) below is satisfied:
1.0<f3/f<2.0   (7) where f3: focal length of the third lens, and f: focal length of an overall optical system of the imaging lens.

12. The imaging lens composed of six optical elements according to claim 1, wherein a conditional expression (8) below is satisfied:
−2.0<f45/f<−1.2   (8) where f45: composite focal length of the fourth lens and the fifth lens, and f: focal length of an overall optical system of the imaging lens.

13. The imaging lens composed of six optical elements according to claim 1, wherein a conditional expression (9) below is satisfied:
2.5<(r3+r4)/(r3−r4)<5.0   (9) where r3: curvature radius of the object-side surface of the second lens, and r4: curvature radius of the image-side surface of the second lens.

14. The imaging lens composed of six optical elements according to claim 1, wherein conditional expressions (10) to (12) below are satisfied:
20<νd1−νd2<40   (10)
20<νd4−νd3<40   (11)
40<νd5<70   (12) where νd1: Abbe number of the first lens at d-ray, νd2: Abbe number of the second lens at d-ray, νd3: Abbe number of the third lens at d-ray, νd4: Abbe number of the fourth lens at d-ray, and νd5: Abbe number of the fifth lens at d-ray.

15. The imaging lens composed of six optical elements according to claim 7, wherein the fifth lens is a meniscus lens having a concave surface on the image side which has the weakest positive or negative refractive power among the optical elements with refractive power, and the object-side and image-side surfaces of the fifth lens are aspheric surfaces with pole-change points off an optical axis.

16. The imaging lens composed of six optical elements according to claim 7, wherein conditional expressions (4) and (5) below are satisfied:
0.08<T23/f<0.2   (4)
0.03<d2/f<0.08   (5) where T23: air gap on an optical axis between the second lens and the third lens, d2: thickness of the second lens on the optical axis, and f: focal length of an overall optical system of the imaging lens.

17. The imaging lens composed of six optical elements according to claim 7, wherein a conditional expression (6) below is satisfied:
1.0<f12/f<1.6   (6) where f12: composite focal length of the first lens and the second lens, and f: focal length of an overall optical system of the imaging lens.

18. The imaging lens composed of six optical elements according to claim 10, wherein a conditional expression (7) below is satisfied:
1.0<f3/f<2.0   (7) where f3: focal length of the third lens, and f: focal length of an overall optical system of the imaging lens.

19. The imaging lens composed of six optical elements according to claim 11, wherein a conditional expression (8) below is satisfied:
−2.0<f45/f<−1.2   (8) where f45: composite focal length of the fourth lens and the fifth lens, and f: focal length of an overall optical system of the imaging lens.

20. The imaging lens composed of six optical elements according to claim 7, wherein a conditional expression (9) below is satisfied:
2.5<(r3+r4)/(r3−r4)<5.0   (9) where r3: curvature radius of the object-side surface of the second lens, and r4: curvature radius of the image-side surface of the second lens.

21. The imaging lens composed of six optical elements according to claim 7, wherein conditional expressions (10) to (12) below are satisfied:
20<νd1−νd2<40   (10)
20<νd4−νd3<40   (11)
40<νd5<70   (12) where νd1: Abbe number of the first lens at d-ray, νd2: Abbe number of the second lens at d-ray, νd3: Abbe number of the third lens at d-ray, νd4: Abbe number of the fourth lens at d-ray, and νd5: Abbe number of the fifth lens at d-ray.

22. The imaging lens composed of six optical elements according to claim 17, wherein a conditional expression (7) below is satisfied:
1.0<f3/f<2.0   (7) where f3: focal length of the third lens, and f: focal length of an overall optical system of the imaging lens.

23. The imaging lens composed of six optical elements according to claim 18, wherein a conditional expression (8) below is satisfied:
−2.0<f45/f<−1.2   (8) where f45: composite focal length of the fourth lens and the fifth lens, and f: focal length of an overall optical system of the imaging lens.

24. The imaging lens composed of six optical elements according to claim 22, wherein a conditional expression (8) below is satisfied:
−2.0<f45/f<−1.2   (8) where f45: composite focal length of the fourth lens and the fifth lens, and f: focal length of an overall optical system of the imaging lens.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic view showing the general configuration of an imaging lens in Numerical Example 1 according to an embodiment of the present invention;

(2) FIG. 2 shows spherical aberration, astigmatism, and distortion of the imaging lens in Numerical Example 1 according to the embodiment of the present invention;

(3) FIG. 3 is a schematic view showing the general configuration of an imaging lens in Numerical Example 2 according to the embodiment of the present invention;

(4) FIG. 4 shows spherical aberration, astigmatism, and distortion of the imaging lens in Numerical Example 2 according to the embodiment of the present invention;

(5) FIG. 5 is a schematic view showing the general configuration of an imaging lens in Numerical Example 3 according to the embodiment of the present invention;

(6) FIG. 6 shows spherical aberration, astigmatism, and distortion of the imaging lens in Numerical Example 3 according to the embodiment of the present invention;

(7) FIG. 7 is a schematic view showing the general configuration of an imaging lens in Numerical Example 4 according to the embodiment of the present invention;

(8) FIG. 8 shows spherical aberration, astigmatism, and distortion of the imaging lens in Numerical Example 4 according to the embodiment of the present invention;

(9) FIG. 9 is a schematic view showing the general configuration of an imaging lens in Numerical Example 5 according to the embodiment of the present invention;

(10) FIG. 10 shows spherical aberration, astigmatism, and distortion of the imaging lens in Numerical Example 5 according to the embodiment of the present invention;

(11) FIG. 11 is a schematic view showing the general configuration of an imaging lens in Numerical Example 6 according to the embodiment of the present invention; and

(12) FIG. 12 shows spherical aberration, astigmatism, and distortion of the imaging lens in Numerical Example 6 according to the embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(13) Hereinafter, the preferred embodiment of the present invention will be described in detail referring to the accompanying drawings. FIGS. 1, 3, 5, 7, 9, and 11 are schematic views showing the general configurations of the imaging lenses composed of six optical elements in Examples 1 to 6 according to this embodiment, respectively. Since all these examples have the same basic lens configuration, the general configuration of an imaging lens according to this embodiment is explained below mainly referring to the schematic view of Example 1.

(14) As shown in FIG. 1, the imaging lens composed of six optical elements according to this embodiment includes, in order from an object side, a first positive lens L1 as a first optical element, a second negative lens L2 as a second optical element, a third positive lens L3 as a third optical element, a fourth negative lens L4 as a fourth optical element, and a fifth negative lens L5 as a fifth optical element. As a sixth optical element, an aberration correction optical element NE as a double-sided aspheric element which has virtually no refractive power is located between the first lens L1 and the second lens L2. Thus, the imaging lens according to this embodiment includes a total of six elements: five optical elements with refractive power and one aberration correction optical element with virtually no refractive power.

(15) A filter IR such as an infrared cut filter is located between the fifth lens L5 and the image plane IMG. The filter IR is omissible. The values of total track length and back focus of the imaging lens according to this embodiment are defined as equivalent air distances for the filter IR. An aperture stop ST is located on the object side of the first lens L1.

(16) In the imaging lens composed of six optical elements according to this embodiment, the first lens L1 to the fourth lens L4 have positive, negative, positive, and negative refractive power, respectively, making up a configuration which is advantageous in enhancing the telephoto capability and achieving low-profileness. The first lens L1 is a biconvex lens with strong refractive power to achieve low-profileness. The second lens L2 has a meniscus shape with a concave surface on the image side and corrects spherical aberrations and chromatic aberrations properly. The third lens L3 has a meniscus shape with a convex surface on the image side, and ensures low-profileness through its positive refractive power and corrects astigmatism and field curvature. The fourth lens L4 has a meniscus shape with a convex surface on the image side and corrects spherical aberrations which occur on the third lens L3 and also corrects field curvature properly using the aspheric surfaces on the both sides. The fifth lens L5 has a meniscus shape with a concave surface on the image side and mainly corrects field curvature and distortion in the peripheral area using the aspheric surfaces on the both sides. In addition to these five constituent lenses with refractive power, the aberration correction optical element NE with virtually no refractive power as the sixth optical element is located between the first lens L1 and the second lens L2 to properly correct aberrations which occur in the peripheral area.

(17) Since the aberration correction optical element NE with virtually no refractive power as the sixth optical element has a parallel plate shape near an optical axis, it influences neither the refractive power of the overall optical system of the imaging lens, nor the refractive power of each of constituent lens from the first lens L1 to the fifth lens L5. Therefore, it corrects aberrations only in the peripheral area without changing parameters such as focal length and lens center thickness.

(18) Since the aberration correction optical element NE with virtually no refractive power as the sixth optical element is located somewhere between the first lens L1 and the image plane IMG, using the aspheric surfaces on the both sides it properly corrects aberrations in the peripheral area, particularly aberrations which occur on a lens located nearer to the object than the aberration correction optical element NE. Therefore, it is effective in improving aberrations of rays over a wide field of view, so that it contributes to correcting aberrations in the peripheral area which increase as the field of view is wider and the F-value is lower.

(19) Alternatively, the aberration correction optical element NE may be located between the second lens L2 and the third lens L3 as in Example 2, or between the third lens L3 and the fourth lens L4 as in Example 3, or between the fourth lens L4 and the fifth lens L5 as in Example 4, or between the fifth lens L5 and the image plane IMG as in Examples 5 and 6. In other words, when the aberration correction optical element NE is located between any two neighboring lenses, it properly corrects aberrations in the peripheral area which occur on a lens located nearer to the object than it.

(20) The shape of the first lens L1 is not limited to a biconvex shape, but as in Examples 3 to 6, it may have a meniscus shape with a convex surface on the object side. The shape of the third lens L3 is not limited to a meniscus shape with a convex surface on the image side, but as in Example 2, it may have a biconvex shape. The refractive power of the fifth lens L5 is not limited to negative refractive power, but it may have positive refractive power if its refractive power is well balanced with the refractive power of the fourth lens L4 so that their composite refractive power is negative. The fifth lens L5 has positive refractive power in Examples 2 to 5.

(21) The aperture stop ST is located on the object side of the first lens L1. Therefore, the exit pupil is remote from the image plane IMG, so that it is easy to ensure telecentricity.

(22) When the imaging lens composed of six optical elements according to this embodiment satisfies conditional expressions (1) to (12) below, it brings about advantageous effects:
0.05<TN/f<0.5   (1)
0.03<dN/f<0.1   (2)
40<νdN<70   (3)
0.08<T23/f<0.2   (4)
0.03<d2/f<0.082   (5)
1.0<f12/f<1.6   (6)
1.0<f3/f<2.0   (7)
−2.0<f45/f<−1.2   (8)
2.5<(r3+r4)/(r3−r4)<5.0   (9)
20<νd1−νd2<40   (10)
20<νd4−νd3<40   (11)
40<νd5<70   (12)

(23) where TN: distance on the optical axis X between lenses where the aberration correction optical element NE is located, dN: thickness of the aberration correction optical element NE on the optical axis X, f: focal length of the overall optical system of the imaging lens, νdN: Abbe number of the aberration correction optical element NE at d-ray, T23: air gap on the optical axis X between the second lens L2 and the third lens L3, d2: thickness of the second lens L2 on the optical axis X, f12: composite focal length of the first lens L1 and second lens L2, f3: focal length of the third lens L3, f45: composite focal length of the fourth lens L4 and fifth lens L5, r3: curvature radius of the object-side surface of the second lens L2, r4: curvature radius of the image-side surface of the second lens L2, νd1: Abbe number of the first lens L1 at d-ray, νd2: Abbe number of the second lens L2 at d-ray, νd3: Abbe number of the third lens L3 at d-ray, νd4: Abbe number of the fourth lens L4 at d-ray, and νd5: Abbe number of the fifth lens L5 at d-ray.

(24) When the imaging lens composed of six optical elements according to this embodiment satisfies conditional expressions (1a) to (12a) below, it brings about more advantageous effects:
0.05<TN/f<0.40   (1a)
0.04<dN/f<0.08   (2a)
45<νdN<65   (3a)
0.09<T23/f<0.18   (4a)
0.04<d2/f<0.06   (5a)
1.0<f12/f<1.5   (6a)
1.0<f3/f<1.6   (7a)
−1.8<f45/f<−1.5   (8a)
2.5<(r3+r4)/(r3−r4)<4.8   (9a)
25<νd1−νd2<40   (10a)
25<νd4−νd3<40   (11a)
45<νd5<65.   (12a)

(25) The signs in the above conditional expressions have the same meanings as those in the preceding paragraph.

(26) When the imaging lens composed of six optical elements according to this embodiment satisfies conditional expressions (1b) to (12b) below, it brings about particularly advantageous effects:
0.06≦TN/f≦0.35   (1b)
0.05≦dN/f≦0.07   (2b)
50<νdN<60   (3b)
0.10≦T23/f≦0.17   (4b)
0.05≦d2/f≦0.06   (5b)
1.13≦f12/f≦1.46   (6b)
1.19≦f3/f≦1.87   (7b)
−1.99≦f45/f≦−1.38   (8b)
2.82≦(r3+r4)/(r3−r4)≦4.41   (9b)
28<νd1−νd2<36   (10b)
28<νd4−νd3<36   (11b)
50<νd5<60.   (12b)

(27) The signs in the above conditional expressions have the same meanings as those in the preceding paragraph.

(28) In this embodiment, all the lens surfaces are aspheric. The aspheric shapes of these lens surfaces are expressed by Equation 1, where Z denotes an axis in the optical axis direction, H denotes a height perpendicular to the optical axis, k denotes a conic constant, and A4, A6, A8, A10, A12, A14, and A16 denote aspheric surface coefficients.

(29) $\begin{array}{cc}Z=\frac{\frac{H^2}{R}}{1+\sqrt{1-\left(k+1\right)\frac{H^2}{R^2}}}+A_4{H}^4+A_6{H}^6+A_8{H}^8+A_{10}{H}^{10}+A_{12}{H}^{12}+A_{14}{H}^{14}+A_{16}{H}^{16}& \mathrm{Equation}1\end{array}$

(30) Next, examples of the imaging lens according to this embodiment will be explained. In each example, f denotes the focal length of the overall optical system of the imaging lens, Fno denotes an F-number, ω denotes a half field of view, ih denotes a maximum image height, TLA denotes a total track length (equivalent air distance for a filter IR), and bf denotes a back focus (equivalent air distance for a filter IR). i denotes a surface number counted from the object side, r denotes a curvature radius, d denotes the distance on the optical axis between lens surfaces (surface distance), Nd denotes a refractive index at d-ray (reference wavelength), and νd denotes an Abbe number at d-ray. As for aspheric surfaces, an asterisk (*) after surface number i indicates that the surface concerned is an aspheric surface.

NUMERICAL EXAMPLE 1

(31) The basic lens data of Numerical Example 1 is shown below.

(32) TABLE-US-00001 in mm f = 4.25 Fno = 2.3 ω(°) = 35.4 ih = 3.06 TLA = 5.15 bf = 1.26 Surface Data Curvature Surface Refractive Abbe Surface No. i Radius r Distance d Index Nd Number νd (Object Surface) Infinity Infinity  1 (Stop) Infinity −0.205  2* 1.858 0.539 1.544 55.57 (vd1)  3* −90.000 0.071  4* Infinity 0.200 1.535 55.66 (vdN)  5* Infinity 0.021  6* 2.762 0.200 1.635 23.97 (vd2)  7* 1.568 0.449  8* −49.915 0.363 1.544 55.57 (vd3)  9* −2.607 0.378 10* −0.878 0.417 1.614 25.58 (vd4) 11* −1.196 0.100 12* 2.778 1.157 1.544 55.57 (vd5) 13* 1.906 0.280 14 Infinity 0.300 1.563 51.30 15 Infinity 0.785 Image Plane Infinity Constituent Lens Data Lens Start Surface Focal Length 1 2 3.354 2 6 −6.111 3 8 5.044 4 10 −10.697 5 12 −20.943 Composite Focal Length Lens 1, 2 5.655 4, 5 −5.872 Aspheric Surface Data 2nd Surface 3rd Surface 4th Surface 5th Surface 6th Surface 7th Surface k 0.000E+00 0.000E+00 0.000E+00 0.000E+00 −4.156E+01 −1.068E+01 A4 −2.570E−02 −8.669E−02 1.921E−03 5.299E−04 −1.206E−01 −1.362E−02 A6 3.148E−02 8.816E−02 −7.954E−03 1.051E−02 1.286E−01 3.824E−02 A8 −6.597E−02 −8.687E−02 −6.724E−03 −6.687E−03 3.982E−02 1.350E−01 A10 −2.043E−02 −2.255E−02 −4.384E−04 −1.264E−02 −1.296E−01 −2.363E−01 A12 8.918E−02 4.768E−02 0.000E+00 0.000E+00 3.503E−02 1.510E−01 A14 −6.655E−02 −2.451E−02 0.000E+00 0.000E+00 1.695E−02 −2.738E−02 A16 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00 8th Surface 9th Surface 10th Surface 11th Surface 12th Surface 13th Surface k 0.000E+00 3.581E+00 −3.899E+00 −8.168E−01 −2.476E+01 −1.031E+01 A4 −1.076E−01 −1.638E−02 −5.435E−02 1.273E−01 −1.233E−01 −4.748E−02 A6 −3.004E−02 −4.221E−02 −1.490E−02 −4.880E−02 6.750E−02 1.762E−02 A8 3.611E−02 3.786E−02 1.137E−01 1.994E−02 −4.172E−02 −7.368E−03 A10 −6.063E−03 4.558E−02 −4.709E−02 1.099E−02 2.106E−02 2.149E−03 A12 1.702E−02 −1.558E−03 −5.391E−03 −2.911E−03 −5.895E−03 −3.892E−04 A14 6.292E−02 6.163E−04 3.333E−03 −2.719E−03 8.248E−04 3.848E−05 A16 −4.209E−02 0.000E+00 −1.655E−04 7.487E−04 −4.592E−05 −1.572E−06

(33) In this example, the aberration correction optical element NE as a double-sided aspheric element with virtually no refractive power is located between the first lens L1 and the second lens L2.

(34) As shown in Table 1, the imaging lens in Numerical Example 1 satisfies all the conditional expressions (1) to (12).

(35) FIG. 2 shows spherical aberration (mm), astigmatism (mm), and distortion (%) of the imaging lens in Numerical Example 1. The spherical aberration diagram shows the amount of aberration at wavelengths of F-ray (486 nm), d-ray (588 nm), and C-ray (656 nm). The astigmatism diagram shows the amount of aberration at d-ray on sagittal image surface S and the amount of aberration at d-ray on tangential image surface T (the same is true for FIGS. 4, 6, 8, 10, and 12). As shown in FIG. 2, each aberration is corrected properly.

NUMERICAL EXAMPLE 2

(36) The basic lens data of Numerical Example 2 is shown below.

(37) TABLE-US-00002 in mm f = 4.17 Fno = 2.2 ω(°) = 36.0 ih = 3.06 TLA = 5.15 bf = 1.28 Surface Data Curvature Surface Refractive Abbe Surface No. i Radius r Distance d Index Nd Number νd (Object Surface) Infinity Infinity  1 (Stop) Infinity −0.213  2* 2.014 0.514 1.544 55.57 (vd1)  3* −37.346 0.085  4* 2.559 0.220 1.639 23.23 (vd2)  5* 1.583 0.126  6* Infinity 0.228 1.535 55.66 (vdN)  7* Infinity 0.334  8* 88.859 0.367 1.544 55.57 (vd3)  9* −2.873 0.380 10* −0.837 0.339 1.639 23.23 (vd4) 11* −1.177 0.135 12* 2.208 1.135 1.544 55.57 (vd5) 13* 1.813 0.540 14 Infinity 0.300 1.517 64.20 15 Infinity 0.546 Image Plane Infinity Constituent Lens Data Lens Start Surface Focal Length 1 2 3.531 2 4 −7.122 3 8 5.124 4 10 −7.420 5 12 1709.609 Composite Focal Length Lens 1, 2 5.741 4, 5 −6.105 Aspheric Surface Data 2nd Surface 3rd Surface 4th Surface 5th Surface 6th Surface 7th Surface k 0.000E+00 0.000E+00 −2.937E+01 −9.649E+00 0.000E+00 0.000E+00 A4 1.708E−03 −7.268E−02 −1.446E−01 −5.982E−02 −9.294E−03 −1.454E−02 A6 2.061E−02 1.205E−01 8.857E−02 −2.712E−02 2.627E−02 4.235E−02 A8 −5.672E−02 −9.474E−02 4.803E−02 1.415E−01 3.476E−02 2.168E−02 A10 −5.036E−03 −1.517E−02 −1.294E−01 −2.241E−01 0.000E+00 0.000E+00 A12 9.875E−02 5.516E−02 8.495E−03 1.327E−01 0.000E+00 0.000E+00 A14 −7.472E−02 −4.466E−02 1.541E−02 −2.451E−02 0.000E+00 0.000E+00 A16 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00 8th Surface 9th Surface 10th Surface 11th Surface 12th Surface 13th Surface k 0.000E+00 4.243E+00 −3.919E+00 −7.832E−01 −2.014E+01 −8.448E+00 A4 −1.185E−01 −2.503E−02 −5.027E−02 1.336E−01 −1.277E−01 −5.264E−02 A6 −4.313E−02 −6.120E−02 −1.626E−02 −4.001E−02 6.972E−02 2.013E−02 A8 3.789E−02 2.366E−02 1.052E−01 2.059E−02 −4.182E−02 −7.766E−03 A10 −2.964E−02 4.859E−02 −4.351E−02 8.561E−03 2.102E−02 2.154E−03 A12 2.574E−02 2.543E−03 −4.569E−03 −3.125E−03 −5.891E−03 −3.836E−04 A14 7.214E−02 −1.847E−03 2.486E−03 −2.519E−03 8.238E−04 3.835E−05 A16 −4.822E−02 0.000E+00 −3.554E−04 7.539E−04 −4.561E−05 −1.599E−06

(38) In this example, the aberration correction optical element NE as a double-sided aspheric element with virtually no refractive power is located between the second lens L2 and the third lens L3.

(39) As shown in Table 1, the imaging lens in Numerical Example 2 satisfies all the conditional expressions (1) to (12).

(40) FIG. 4 shows spherical aberration (mm), astigmatism (mm), and distortion (%) of the imaging lens in Numerical Example 2. As shown in FIG. 4, each aberration is corrected properly.

NUMERICAL EXAMPLE 3

(41) The basic lens data of Numerical Example 3 is shown below.

(42) TABLE-US-00003 in mm f = 4.15 Fno = 2.2 ω(°) = 36.0 ih = 3.06 TLA = 5.18 bf = 1.24 Surface Data Curvature Surface Refractive Abbe Surface No. i Radius r Distance d Index Nd Number νd (Object Surface) Infinity Infinity  1 (Stop) Infinity −0.276  2* 1.718 0.507 1.544 55.57 (vd1)  3* 9.438 0.133  4* 2.996 0.220 1.639 23.23 (vd2)  5* 1.801 0.415  6* −13.134 0.372 1.544 55.57 (vd3)  7* −2.511 0.020  8* Infinity 0.259 1.535 55.66 (vdN)  9* Infinity 0.390 10* −0.847 0.364 1.639 23.23 (vd4) 11* −1.230 0.024 12* 2.022 1.236 1.544 55.57 (vd5) 13* 1.955 0.540 14 Infinity 0.210 1.517 64.20 15 Infinity 0.561 Image Plane Infinity Constituent Lens Data Lens Start Surface Focal Length 1 2 3.774 2 4 −7.614 3 6 5.640 4 10 −6.774 5 12 19.715 Composite Focal Length Lens 1, 2 6.079 4, 5 −8.258 Aspheric Surface Data 2nd Surface 3rd Surface 4th Surface 5th Surface 6th Surface 7th Surface k 0.000E+00 1.532E+01 −3.112E+01 −1.038E+01 0.000E+00 3.428E+00 A4 2.160E−03 −7.454E−02 −1.356E−01 −1.860E−02 −8.171E−02 −2.431E−02 A6 3.761E−02 1.085E−01 1.092E−01 1.024E−02 −4.947E−02 −5.037E−02 A8 −5.439E−02 −8.601E−02 1.417E−02 1.288E−01 3.894E−02 2.458E−02 A10 −6.624E−03 −1.322E−02 −1.441E−01 −2.425E−01 −3.019E−03 4.834E−02 A12 9.680E−02 4.563E−02 4.376E−02 1.564E−01 2.399E−02 4.622E−03 A14 −7.115E−02 −3.629E−02 2.283E−02 −2.795E−02 5.154E−02 6.046E−03 A16 0.000E+00 0.000E+00 0.000E+00 0.000E+00 −4.171E−02 0.000E+00 8th Surface 9th Surface 10th Surface 11th Surface 12th Surface 13th Surface k 0.000E+00 0.000E+00 −4.363E+00 −7.103E−01 −2.141E+01 −8.826E+00 A4 −3.669E−02 −3.058E−02 −7.187E−02 1.087E−01 −1.162E−01 −4.764E−02 A6 −2.386E−02 5.094E−04 −1.232E−02 −3.615E−02 6.629E−02 1.807E−02 A8 7.154E−03 −2.151E−04 1.202E−01 2.303E−02 −4.189E−02 −7.454E−03 A10 0.000E+00 0.000E+00 −4.675E−02 9.586E−03 2.108E−02 2.165E−03 A12 0.000E+00 0.000E+00 −7.169E−03 −3.120E−03 −5.880E−03 −3.877E−04 A14 0.000E+00 0.000E+00 3.261E−03 −2.651E−03 8.242E−04 3.801E−05 A16 0.000E+00 0.000E+00 4.275E−04 7.816E−04 −4.621E−05 −1.548E−06

(43) In this example, the aberration correction optical element NE as a double-sided aspheric element with virtually no refractive power is located between the third lens L3 and the fourth lens L4.

(44) As shown in Table 1, the imaging lens in Numerical Example 3 satisfies all the conditional expressions (1) to (12).

(45) FIG. 6 shows spherical aberration (mm), astigmatism (mm), and distortion (%) of the imaging lens in Numerical Example 3. As shown in FIG. 6, each aberration is corrected properly.

NUMERICAL EXAMPLE 4

(46) The basic lens data of Numerical Example 4 is shown below.

(47) TABLE-US-00004 in mm f = 4.16 Fno = 2.2 ω(°) = 36.0 ih = 3.06 TLA = 5.09 bf = 1.27 Surface Data Curvature Surface Refractive Abbe Surface No. i Radius r Distance d Index Nd Number νd (Object Surface) Infinity Infinity  1 (Stop) Infinity −0.286  2* 1.650 0.521 1.544 55.57 (vd1)  3* 7.066 0.111  4* 2.822 0.231 1.639 23.23 (vd2)  5* 1.779 0.458  6* −17.526 0.398 1.544 55.57 (vd3)  7* −2.620 0.430  8* −0.804 0.266 1.639 23.23 (vd4)  9* −1.180 0.020 10* Infinity 0.200 1.535 55.66 (vdN) 11* Infinity 0.020 12* 1.792 1.159 1.544 55.57 (vd5) 13* 1.864 0.540 14 Infinity 0.300 1.517 64.20 15 Infinity 0.535 Image Plane Infinity Constituent Lens Data Lens Start Surface Focal Length 1 2 3.828 2 4 −8.245 3 6 5.611 4 8 −5.458 5 12 12.799 Composite Focal Length Lens 1, 2 5.877 4, 5 −7.536 Aspheric Surface Data 2nd Surface 3rd Surface 4th Surface 5th Surface 6th Surface 7th Surface k 0.000E+00 −7.475E+00 −2.094E+01 −8.011E+00 0.000E+00 3.556E+00 A4 3.354E−03 −7.819E−02 −1.256E−01 −4.335E−03 −1.037E−01 −2.577E−02 A6 3.470E−02 1.081E−01 1.128E−01 2.455E−02 −3.601E−02 −4.613E−02 A8 −5.526E−02 −8.402E−02 1.636E−02 1.380E−01 4.126E−02 3.264E−02 A10 −3.851E−03 −1.685E−02 −1.433E−01 −2.363E−01 −3.437E−03 4.496E−02 A12 9.690E−02 4.309E−02 4.470E−02 1.597E−01 2.051E−02 −2.869E−03 A14 −7.427E−02 −3.524E−02 2.068E−02 −2.579E−02 6.025E−02 1.378E−03 A16 0.000E+00 0.000E+00 0.000E+00 0.000E+00 −4.566E−02 0.000E+00 8th Surface 9th Surface 10th Surface 11th Surface 12th Surface 13th Surface k −4.025E+00 −7.240E−01 0.000E+00 0.000E+00 −1.839E+01 −8.627E+00 A4 −8.271E−02 1.085E−01 −3.606E−03 −2.031E−04 −1.157E−01 −4.818E−02 A6 −1.035E−02 −3.412E−02 −1.727E−03 6.968E−04 6.678E−02 1.854E−02 A8 1.207E−01 2.249E−02 2.750E−04 −2.901E−04 −4.187E−02 −7.614E−03 A10 −4.711E−02 9.528E−03 0.000E+00 0.000E+00 2.106E−02 2.170E−03 A12 −7.559E−03 −3.216E−03 0.000E+00 0.000E+00 −5.887E−03 −3.844E−04 A14 3.198E−03 −2.665E−03 0.000E+00 0.000E+00 8.236E−04 3.819E−05 A16 6.086E−04 7.748E−04 0.000E+00 0.000E+00 −4.567E−05 −1.593E−06

(48) In this example, the aberration correction optical element NE as a double-sided aspheric element with virtually no refractive power is located between the fourth lens L4 and the fifth lens L5.

(49) As shown in Table 1, the imaging lens in Numerical Example 4 satisfies all the conditional expressions (1) to (12).

(50) FIG. 8 shows spherical aberration (mm), astigmatism (mm), and distortion (%) of the imaging lens in Numerical Example 4. As shown in FIG. 8, each aberration is corrected properly.

NUMERICAL EXAMPLE 5

(51) The basic lens data of Numerical Example 5 is shown below.

(52) TABLE-US-00005 in mm f = 4.16 Fno = 2.2 ω(°) = 36.0 ih = 3.06 TLA = 5.14 bf = 1.35 Surface Data Curvature Surface Refractive Abbe Surface No. i Radius r Distance d Index Nd Number νd (Object Surface) Infinity Infinity  1 (Stop) Infinity −0.299  2* 1.619 0.522 1.544 55.57 (vd1)  3* 7.865 0.126  4* 2.737 0.220 1.639 23.23 (vd2)  5* 1.678 0.456  6* −14.973 0.360 1.544 55.57 (vd3)  7* −2.552 0.453  8* −0.805 0.351 1.639 23.23 (vd4)  9* −1.138 0.035 10* 2.288 1.269 1.544 55.57 (vd5) 11* 2.188 0.200 12* Infinity 0.200 1.535 55.66 (vdN) 13* Infinity 0.300 14 Infinity 0.300 1.517 64.20 15 Infinity 0.451 Image Plane Infinity Constituent Lens Data Lens Start Surface Focal Length 1 2 3.642 2 4 −7.380 3 6 5.600 4 8 −7.288 5 10 26.587 Composite Focal Length Lens 1, 2 5.773 4, 5 −8.261 Aspheric Surface Data 2nd Surface 3rd Surface 4th Surface 5th Surface 6th Surface 7th Surface k 0.000E+00 −1.592E+00 −2.341E+01 −7.960E+00 0.000E+00 3.448E+00 A4 4.775E−03 −7.694E−02 −1.260E−01 2.184E−04 −9.638E−02 −2.532E−02 A6 3.436E−02 1.107E−01 1.146E−01 2.768E−02 −3.270E−02 −3.623E−02 A8 −5.522E−02 −7.825E−02 1.400E−02 1.371E−01 4.020E−02 3.471E−02 A10 6.881E−05 −1.783E−02 −1.430E−01 −2.416E−01 −4.716E−03 4.440E−02 A12 9.966E−02 4.318E−02 4.329E−02 1.558E−01 2.076E−02 −1.989E−04 A14 −7.794E−02 −3.982E−02 1.527E−02 −2.441E−02 6.126E−02 1.857E−03 A16 0.000E+00 0.000E+00 0.000E+00 0.000E+00 −4.840E−02 0.000E+00 8th Surface 9th Surface 10th Surface 11th Surface 12th Surface 13th Surface k −3.751E+00 −7.262E−01 −2.596E+01 −1.041E+01 0.000E+00 0.000E+00 A4 −7.993E−02 1.167E−01 −1.127E−01 −4.821E−02 −5.471E−04 3.600E−03 A6 −9.851E−03 −3.821E−02 6.623E−02 1.759E−02 −3.314E−04 −6.680E−04 A8 1.205E−01 2.258E−02 −4.194E−02 −7.469E−03 −1.474E−05 −1.517E−05 A10 −4.720E−02 9.711E−03 2.106E−02 2.171E−03 4.112E−06 3.031E−06 A12 −7.712E−03 −3.071E−03 −5.881E−03 −3.860E−04 0.000E+00 0.000E+00 A14 3.133E−03 −2.652E−03 8.250E−04 3.810E−05 0.000E+00 0.000E+00 A16 6.918E−04 7.605E−04 −4.611E−05 −1.572E−06 0.000E+00 0.000E+00

(53) In this example, the aberration correction optical element NE as a double-sided aspheric element with virtually no refractive power is located between the fifth lens L5 and the image plane IMG.

(54) As shown in Table 1, the imaging lens in Numerical Example 5 satisfies all the conditional expressions (1) to (12).

(55) FIG. 10 shows spherical aberration (mm), astigmatism (mm), and distortion (%) of the imaging lens in Numerical Example 5. As shown in FIG. 10, each aberration is corrected properly.

NUMERICAL EXAMPLE 6

(56) The basic lens data of Numerical Example 6 is shown below.

(57) TABLE-US-00006 in mm f = 4.71 Fno = 2.2 ω(°) = 35.7 ih = 3.43 TLA = 5.33 bf = 1.51 Surface Data Curvature Surface Refractive Abbe Surface No. i Radius r Distance d Index Nd Number νd (Object Surface) Infinity Infinity  1 (Stop) Infinity −0.390  2* 1.614 0.628 1.544 55.57 (vd1)  3* 12.591 0.088  4* 4.535 0.220 1.635 23.97 (vd2)  5* 2.161 0.599  6* −6.796 0.307 1.544 55.57 (vd3)  7* −2.857 0.369  8* −1.113 0.277 1.639 23.23 (vd4)  9* −1.335 0.389 10* 3.017 0.948 1.544 55.57 (vd5) 11* 1.951 0.204 12* Infinity 0.322 1.535 55.66 (vdN) 13* Infinity 0.115 14 Infinity 0.210 1.517 64.20 15 Infinity 0.729 Image Plane Infinity Constituent Lens Data Lens Start Surface Focal Length 1 2 3.337 2 4 −6.743 3 6 8.820 4 8 −20.382 5 10 −14.801 Composite Focal Length Lens 1, 2 5.334 4, 5 −7.526 Aspheric Surface Data 2nd Surface 3rd Surface 4th Surface 5th Surface 6th Surface 7th Surface k 0.000E+00 2.474E+01 −5.029E+01 −8.615E+00 0.000E+00 2.349E+00 A4 9.239E−04 −5.801E−02 −7.901E−02 2.753E−02 −9.798E−02 −2.487E−02 A6 1.929E−02 5.650E−02 9.725E−02 5.177E−02 −2.279E−02 −4.689E−02 A8 −2.631E−02 −1.450E−02 1.355E−02 7.271E−02 1.802E−02 5.196E−02 A10 −2.527E−03 −8.675E−03 −5.394E−02 −1.021E−01 2.425E−02 0.000E+00 A12 3.072E−02 1.080E−02 1.460E−02 5.637E−02 −6.249E−03 0.000E+00 A14 −1.692E−02 −8.963E−03 0.000E+00 −2.927E−03 1.228E−02 0.000E+00 A16 0.000E+00 0.000E+00 0.000E+00 0.000E+00 −8.610E−03 0.000E+00 8th Surface 9th Surface 10th Surface 11th Surface 12th Surface 13th Surface k −4.092E+00 −7.796E−01 −2.627E+01 −9.941E+00 0.000E+00 0.000E+00 A4 −2.818E−02 8.952E−02 −1.046E−01 −5.639E−02 −7.612E−03 6.290E−03 A6 −2.885E−03 −2.530E−02 3.896E−02 1.065E−02 −1.015E−04 −1.650E−03 A8 4.449E−02 1.211E−02 −1.860E−02 −3.088E−03 4.157E−05 −2.549E−06 A10 −1.898E−02 3.216E−03 7.501E−03 7.829E−04 1.265E−07 5.363E−06 A12 −1.577E−03 −1.315E−03 −1.659E−03 −1.128E−04 0.000E+00 0.000E+00 A14 1.383E−03 −6.889E−04 1.834E−04 8.110E−06 0.000E+00 0.000E+00 A16 0.000E+00 1.876E−04 −8.133E−06 −2.241E−07 0.000E+00 0.000E+00

(58) In this example, the aberration correction optical element NE as a double-sided aspheric element with virtually no refractive power is located between the fifth lens L5 and the image plane IMG.

(59) As shown in Table 1, the imaging lens in Numerical Example 6 satisfies all the conditional expressions (1) to (12).

(60) FIG. 12 shows spherical aberration (mm), astigmatism (mm), and distortion (%) of the imaging lens in Numerical Example 6. As shown in FIG. 12, each aberration is corrected properly.

(61) TABLE-US-00007 TABLE 1 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 0.05 < TN/f < 0.5 0.07 0.17 0.16 0.06 0.35 0.34 0.03 < dN/f < 0.1 0.05 0.05 0.06 0.05 0.05 0.07 40 < vdN < 70 55.66 55.66 55.66 55.66 55.66 55.66 0.08 < T23/f < 0.2 0.11 0.17 0.10 0.11 0.11 0.13 0.03 < d2/f < 0.08 0.05 0.05 0.05 0.06 0.05 0.05 1.0 < f12/f < 1.6 1.33 1.38 1.46 1.41 1.39 1.13 1.0 < f3/f < 2.0 1.19 1.23 1.36 1.35 1.35 1.87 −2.0 < f45/f < −1.2 −1.38 −1.47 −1.99 −1.81 −1.98 −1.60 2.5 < (r3 + r4)/(r3 − r4) < 5.0 3.63 4.25 4.02 4.41 4.17 2.82 20 < vd1 − vd2 < 40 31.60 32.34 32.34 32.34 32.34 31.60 20 < vd4 − vd3 < 40 29.99 32.34 32.34 32.34 32.34 32.34 40 < vd5 < 70 55.57 55.57 55.57 55.57 55.57 55.57

(62) As explained above, the imaging lenses composed of six optical elements in the examples according to this embodiment of the present invention provide a compact optical system with a short total track length, though they use a total of six optical elements: five elements for an imaging lens and one element with virtually no refractive power for aberration correction. When the degree of low-profileness is expressed by the ratio of total track length TLA to maximum image height ih (TLA/2ih), the TLA/2ih of each of these imaging lenses is about 0.8. In addition, the imaging lenses offer a wide field of view of 70 degrees or more and brightness with an F-value of 2.4 or less, and correct various aberrations properly and can be manufactured at low cost.

(63) When any one of the imaging lenses composed of six optical elements in the examples according to this embodiment of the present invention is used in the image pickup device mounted in an increasingly compact and low-profile mobile terminal such as a smartphone, mobile phone or PDA (Personal Digital Assistant), a game console, an information terminal such as a PC, or a home appliance with a camera function, it contributes to the compactness the image pickup device and provides high camera performance.

(64) The effects of the present invention are as follows.

(65) According to the present invention, there is provided a compact low-cost imaging lens which meets the demand for low-profileness, offers brightness with an F-value of 2.4 or less and a wide field of view, and corrects various aberrations properly.