Imaging lens

Abstract

An imaging lens includes, from an object side to an image side: a first positive lens having a convex object-side surface; an aperture stop; a second negative lens as a meniscus double-sided aspheric lens having a concave object-side surface; and a third positive lens as a meniscus double-sided aspheric lens having a concave image-side surface, wherein the second lens has a diffractive optical surface on the object side, the aspheric object-side and image-side surfaces of the third lens have pole-change points off an optical axis, and conditional expressions (1) to (4) below are satisfied:
8.0<fdoe/f<26.0(1)
20<vd1vd2<40(2)
20<vd3vd2<40(3)
0.8<ih/f<0.95(4).

Claims

1. An imaging lens for an image sensor which includes elements arranged in order from an object side to an image side, comprising: a first lens having positive refractive power and a convex surface on the object side; an aperture stop; a second lens that is a meniscus double-sided aspheric lens having negative refractive power and a concave surface on the object side; and a third lens that is a meniscus double-sided aspheric lens having positive refractive power near an optical axis and a concave surface on the image side, wherein a diffractive optical surface is formed on the object-side surface of the second lens; the aspheric object-side and image-side surfaces of the third lens have pole-change points off an optical axis; and conditional expressions (1) to (4) below are satisfied:
8.0<fdoe/f<26.0(1)
20<vd1vd2<40(2)
20<vd3vd2<40(3)
0.8<ih/f<0.95(4) where fdoe: focal length of the diffractive optical surface, f: focal length of an overall optical system of the imaging lens, vd1: Abbe number of the first lens at d-ray, vd2: Abbe number of the second lens at d-ray, vd3: Abbe number of the third lens at d-ray, and ih: maximum image height.

2. The imaging lens according to claim 1, wherein on the diffractive optical surface, the number of orbicular zones in an effective diameter is 10 or less and the number of orbicular zones in an area through which rays converging on the optical axis pass is 5 or less.

3. The imaging lens according to claim 2, wherein a conditional expression (5) below is satisfied:
0.2<t3/|r3|<0.6(5) where t3: distance on the optical axis from the aperture stop to the object-side surface of the second lens, and r3: curvature radius of the object-side surface of the second lens.

4. The imaging lens according to claim 2, wherein conditional expressions (6) and (7) below are satisfied:
1.2<(r1+r2)/(r1r2)<0.6(6)
7.0<(r3+r4)/(r3r4)<1.2(7) where r1: curvature radius of the object-side surface of the first lens, r2: curvature radius of the image-side surface of the first lens, 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.

5. The imaging lens according to claim 2, wherein conditional expressions (8) to (10) below are satisfied:
1.0<f1/f<1.5(8)
6.0<f2/f<1.0(9)
0.7<f3/f<2.4(10) where f1: focal length of the first lens, f2: focal length of the second lens including the diffractive optical surface, f3: focal length of the third lens, and f: focal length of the overall optical system of the imaging lens.

6. The imaging lens according to claim 1, wherein a conditional expression (5) below is satisfied:
0.2<t3/|r3|<0.6(5) where t3: distance on the optical axis from the aperture stop to the object-side surface of the second lens, and r3: curvature radius of the object-side surface of the second lens.

7. The imaging lens according to claim 1, wherein conditional expressions (6) and (7) below are satisfied:
1.2<(r1+r2)/(r1r2)<0.6(6)
7.0<(r3+r4)/(r3r4)<1.2(7) where r1: curvature radius of the object-side surface of the first lens, r2: curvature radius of the image-side surface of the first lens, 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.

8. The imaging lens according to claim 1, wherein conditional expressions (8) to (10) below are satisfied:
1.0<f1/f<1.5(8)
6.0<f2/f<1.0(9)
0.7<f3/f<2.4(10) where f1: focal length of the first lens, f2: focal length of the second lens including the diffractive optical surface, f3: focal length of the third lens, and f: focal length of the 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 Example 1 of the present invention;

(2) FIG. 2 shows spherical aberration, astigmatism, distortion, and chromatic aberration of magnification of the imaging lens in Example 1;

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

(4) FIG. 4 shows spherical aberration, astigmatism, distortion, and chromatic aberration of magnification of the imaging lens in Example 2;

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

(6) FIG. 6 shows spherical aberration, astigmatism, distortion, and chromatic aberration of magnification of the imaging lens in Example 3;

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

(8) FIG. 8 shows spherical aberration, astigmatism, distortion, and chromatic aberration of magnification of the imaging lens in Example 4;

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

(10) FIG. 10 shows spherical aberration, astigmatism, distortion, and chromatic aberration of magnification of the imaging lens in Example 5;

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

(12) FIG. 12 shows spherical aberration, astigmatism, distortion, and chromatic aberration of magnification of the imaging lens in Example 6; and

(13) FIG. 13 is a schematic view showing the shape of a diffractive optical surface.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(14) Hereinafter, the preferred embodiment of the present invention will be described in detail referring to the accompanying drawings.

(15) FIGS. 1, 3, 5, 7, 9, and 11 are schematic views showing the general configurations of the imaging lenses in Examples 1 to 6 according to this embodiment of the present invention, 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 referring to the schematic view of Example 1 and a schematic view of FIG. 13 showing the shape of a diffractive optical surface.

(16) As shown in FIG. 1, the imaging lens according to the present invention includes, in order from an object side to an image side, a first lens L1 with positive refractive power having a convex surface on the object side, an aperture stop ST, a second lens L2 with negative refractive power as a meniscus double-sided aspheric lens having a concave surface on the object side, and a third lens L3 with positive refractive power as a meniscus double-sided aspheric lens having a concave surface on the image side. The second lens L2 has a diffractive optical surface DOE on the object side and the third lens L3 has pole-change points off the optical axis X on the aspheric object-side and image-side surfaces. A filter IR such as an infrared cut filter is located between the third lens L3 and an image plane IMG. The filter IR is omissible. In this embodiment, the values of total track length and back focus are calculated on the assumption that a thickness of the filter IR is regarded as an air-equivalent distance, that is, an equivalent air distance.

(17) In the imaging lens according to this embodiment, positive, negative and positive refractive power constituent lenses are arranged in order from the object side to enhance the telephoto capability to make it easy to achieve low-profileness, and refractive power is optimally distributed to the constituent lenses and several aspheric surfaces are used to improve the imaging performance. In the imaging lens according to this embodiment, in order to correct chromatic aberrations properly, the first lens L1 of low-dispersion material and the second lens L2 of high-dispersion material are appropriately combined so that the second lens L2, a double-sided aspheric lens with negative refractive power, properly corrects chromatic aberrations which occur on the first lens L1 with positive refractive power, and the appropriate diffractive optical surface DOE is formed on the object-side surface of the second lens L2 with negative refractive power in order to solve the problem related to correction of chromatic aberrations which has been difficult to address in the past. The both surfaces of the third lens L3, located nearest to the image plane, have an aspheric shape with pole-change points off the optical axis X, are used to control the angle of rays incident on the image plane IMG appropriately, and correct field curvature and distortion in a balanced manner. In addition, since the third lens L3 has positive refractive power, the angle of rays incident on the third lens L3 is reduced so that the effective diameter of the second lens L2 can be smaller. Consequently, spherical aberrations and coma aberrations which occur on the second lens L2 are suppressed.

(18) In Example 1, the first lens L1 is a biconvex lens. However, instead it may be a meniscus lens with positive refractive power having a convex surface on the object side or a flat convex lens having a flat surface on the image side.

(19) Since the diffractive optical surface DOE on the object-side surface of the second lens L2 is located near the aperture stop ST as shown in FIG. 13, a bundle of rays exiting the aperture stop ST enters the second lens L2 with a wide incidence area and thus its diffraction efficiency is increased. When d denotes orbicular zone depth, denotes design wavelength and n denotes the refractive index of lens material, the relation among them is expressed by d=/(n1) and the orbicular zone depth is very small at about 1 m. In the design of an ordinary diffractive optical surface, each orbicular zone is in the form of a sharp edge and its cross section C has a sectional shape parallel to the optical axis X. However, actually, since round chamfering is done in the machining process, an edge is not formed and it is desirable that the cross section c be inclined so as to ensure mold releasability. As a consequence, the actual shape of the orbicular zone is an inclined surface with a round tip. The relation between the direction of this inclination and the rays incident on the diffractive optical surface DOE is very important in suppressing flare. Specifically, incident rays 1a, 1b and so on parallel to the lens system, after exiting the first lens L1, go in a direction toward the optical axis X. On the other hand, the cross section c of an orbicular zone of the diffractive optical surface DOE is a surface inclined toward the object side in a direction away from the optical axis X. Therefore, the angles between the incident rays 1a, 1b and so on and the cross sections c are such that they seem almost parallel to each other and the angle of a ray incident on the cross section c is small. This minimizes diffuse reflection which occurs on the cross sections c of the orbicular zones and suppresses flare.

(20) On the diffractive optical surface DOE on the object-side surface of the second lens L2, the total number of orbicular zones in the effective diameter is 10 or less and the number of orbicular zones at zero image height in the area through which a bundle of rays passes is 5 or less. When the number of orbicular zones is limited to 5 or less for a bundle of rays at zero image height, that is, a bundle of rays with the largest luminous energy which enters the optical system, the amount of diffuse reflection on the cross sections c is further reduced. Off-axial rays tend to enter the cross sections c at a wide incidence angle but their luminous energy is small, so that the influence of diffuse reflection is smaller than with the bundle of rays at zero image height. In this embodiment, flare of off-axial rays is also suppressed by limiting the number of orbicular zones in the effective diameter to 10 or less.

(21) When the imaging lens according to this embodiment satisfies conditional expressions (1) to (11) below, it brings about advantageous effects:
8.0<fdoe/f<26.0(1)
20<vd1vd2<40(2)
20<vd3vd2<40(3)
0.8<ih/f<0.95(4)
0.2<t3/|r3|<0.6(5)
1.2<(r1+r2)/(r1r2)<0.6(6)
7.0<(r3+r4)/(r3r4)<1.2(7)
1.0<f1/f<1.5(8)
6.0<f2/f<1.0(9)
0.7<f3/f<2.4(10)
1.7<f2/(f1+f3)<0.5(11) where f: focal length of the overall optical system of the imaging lens, fdoe: focal length of the diffractive optical surface DOE, vd1: Abbe number of the first lens L1 at d-ray, vd2: Abbe number of the second lens L2 at d-ray, vd3: Abbe number of the third lens L3 at d-ray, ih: maximum image height, f1: focal length of the first lens L1, f2: focal length of the second lens L2 including the diffractive optical surface DOE, f3: focal length of the third lens L3, t3: distance on the optical axis X from the aperture stop ST to the object-side surface of the second lens L2, r1: curvature radius of the object-side surface of the first lens L1, r2: curvature radius of the image-side surface of the first lens L1, r3: curvature radius of the object-side surface of the second lens L2, and r4: curvature radius of the image-side surface of the second lens L2.

(22) When the imaging lens according to this embodiment satisfies conditional expressions (1a) to (11a) below, it brings about more advantageous effects:
9.0<fdoe/f<26.0(1a)
25<vd1vd2<35(2a)
25<vd3vd2<35(3a)
0.8<ih/f<0.95(4a)
0.2<t3/|r3|<0.6(5a)
1.0<(r1+r2)/(r1r2)<0.8(6a)
7.0<(r3+r4)/(r3r4)<1.5(7a)
1.0<f1/f<1.3(8a)
5.5<f2/f<1.2(9a)
0.9<f3/f<2.3(10a)
1.6<f2/(f1+f3)<0.55.(11a)

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

(24) When the imaging lens according to this embodiment satisfies conditional expressions (1b) to (11b) below, it brings about particularly advantageous effects:
9.01fdoe/f24.96(1b)
28<vd1vd2<35(2b)
28<vd3vd2<35(3b)
0.8<ih/f0.93(4b)
0.33t3/|r3|0.46(5b)
1.0(r1+r2)/(r1r2)0.85(6b)
6.58(r3+r4)/(r3r4)1.78(7b)
1.18f1/f1.26(8b)
5.26f2/f1.36(9b)
1.04f3/f2.16(10b)
1.54f2/(f1+f3)0.61.(11b)

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

(26) According to this embodiment, the imaging lens is low-profile with a ratio to diagonal of 0.8 or less and offers high brightness with an F-value of 2.4 or less and a wide field of view (2) of 80 degrees or more and provides high resolution.

(27) 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 X, k denotes a conic constant, and A4, A6, A8, A10, A12, A14, and A16 denote aspheric surface coefficients.

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

(29) In this embodiment, the diffractive optical surface DOE formed on the object side of the second lens L2 is expressed by Equation 2, where P denotes a phase difference and B.sub.2i denotes a phase difference function coefficient (i=1 to 8).

(30) $\begin{array}{cc}P=\underset{i=1}{\overset{8}{.Math.}}{B}_{2i}{H}^{2i}& \mathrm{Equation}2\end{array}$

(31) 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, denotes a half field of view, ih denotes a maximum image height, and TLA and bf respectively denote total track length and back focus with the thickness of the filter IR regarded as the equivalent air distance. i denotes a surface number counted from the object side, r denotes a curvature radius, d denotes the distance on the optical axis X between lens surfaces (surface distance), Nd denotes a refractive index at d-ray (reference wavelength), and vd 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. As for a diffractive optical surface, DOE after surface number i indicates that the surface concerned is a diffractive optical surface DOE.

Example 1

(32) The basic lens data of Example 1 is shown in Table 1 below.

(33) TABLE-US-00001 TABLE 1 in mm f = 1.97 Fno = 2.4 () = 42.0 ih = 1.79 TLA = 2.68 bf = 0.91 Surface Data Surface No. i Curvature Radius r Surface Distance d Refractive Index Nd Abbe Number d (Object Surface) Infinity Infinity 1* 1.420 0.371 1.544 55.57 2* 17.611 0.020 3 (Stop) Infinity 0.412 4*DOE 1.044 0.344 1.635 23.97 5* 2.940 0.181 6* 0.551 0.440 1.544 55.57 7* 0.713 0.200 8 Infinity 0.210 1.517 64.20 9 Infinity 0.568 Image Plane Constituent Lens Data Lens Start Surface Focal Length 1 1 2.43 2 4 3.22 3 6 2.27 Diffractive Optical Surface Focal Length 4th Surface 17.717 Aspheric Surface Data 1st Surface 2nd Surface 4th Surface 5th Surface 6th Surface 7th Surface k 3.752E+00 5.889E+01 2.413E+00 1.207E+01 5.830E+00 1.401E+00 A4 1.486E01 3.292E01 1.413E+00 4.306E+00 8.741E01 1.318E+00 A6 2.348E+00 1.013E+00 1.623E+01 2.760E+01 3.328E01 1.977E+00 A8 1.198E+01 8.041E+00 1.443E+02 1.414E+02 1.674E+00 2.157E+00 A10 3.779E+01 5.494E+01 7.709E+02 4.777E+02 3.040E+00 1.612E+00 A12 4.122E+01 1.642E+02 1.944E+03 9.847E+02 2.340E+00 7.655E01 A14 0.000E+00 1.112E+02 2.028E+03 1.173E+03 8.752E01 2.021E01 A16 0.000E+00 0.000E+00 0.000E+00 6.165E+02 1.297E01 2.217E02 Phase Difference Function Coefficient C2 C4 C6 C8 C10 C12 C14 C16 3.021E+02 2.831E+02 3.029E+03 2.182E+03 8.379E+03 3.684E+04 2.477E+04 0.000E+00

(34) Regarding the imaging lens in Example 1, Table 7 shows the values related to the conditional expressions (1) to (11) and Table 8 shows the number of orbicular zones of the diffractive optical surface DOE. As shown in Table 7, the imaging lens in Example 1 satisfies all the conditional expressions (1) to (11). The number of orbicular zones in the effective diameter is 8 and the number of orbicular zones in the area through which rays converging on the optical axis pass is 4, which satisfies the condition to suppress flare.

(35) FIG. 2 shows spherical aberration (mm), astigmatism (mm), distortion (%), and chromatic aberration of magnification (m) of the imaging lens in Example 1. The spherical aberration diagram shows the amount of aberration at wavelengths of F-ray (486 nm), e-ray (546 nm), d-ray (587 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 and the diagram of chromatic aberration of magnification shows the amount of aberration at wavelengths of F-ray (486 nm), e-ray (546 nm), and C-ray (656 nm) with respect to d-ray as the reference wavelength, (the same is true for FIGS. 4, 6, 8, 10, and 12).

(36) As shown in FIG. 2, the imaging lens in Example 1 corrects chromatic aberrations and other aberrations properly. It is sufficiently low-profile with a ratio to diagonal of 0.75 and offers high brightness with an F-value of 2.4 and a wide field of view (2) of 84 degrees.

Example 2

(37) The basic lens data of Example 2 is shown in Table 2 below.

(38) TABLE-US-00002 TABLE 2 in mm f = 2.00 Fno = 2.4 () = 41.5 ih = 1.79 TLA = 2.69 bf = 0.94 Surface Data Surface No. i Curvature Radius r Surface Distance d Refractive Index Nd Abbe Number d (Object Surface) Infinity Infinity 1* 1.283 0.381 1.544 55.57 2* Infinity 0.021 3 (Stop) Infinity 0.356 4*DOE 1.091 0.402 1.635 23.97 5* 2.150 0.221 6* 0.590 0.387 1.544 55.57 7* 0.671 0.200 8 Infinity 0.210 1.517 64.20 9 Infinity 0.578 Image Plane Constituent Lens Data Lens Start Surface Focal Length 1 1 2.36 2 4 5.09 3 6 3.34 Diffractive Optical Surface Focal Length 4th Surface 19.445 Aspheric Surface Data 1st Surface 2nd Surface 4th Surface 5th Surface 6th Surface 7th Surface k 1.602E+00 5.889E+01 3.483E+00 2.362E+02 5.127E+00 1.701E+00 A4 1.530E01 4.693E01 1.261E+00 5.136E+00 9.216E01 1.350E+00 A6 2.710E+00 2.518E+00 1.642E+01 3.903E+01 4.314E01 2.200E+00 A8 1.431E+01 3.971E+01 1.799E+02 2.314E+02 1.176E+00 2.595E+00 A10 4.399E+01 2.610E+02 1.177E+03 9.022E+02 2.184E+00 2.077E+00 A12 4.513E+01 8.748E+02 3.609E+03 2.141E+03 1.712E+00 1.053E+00 A14 0.000E+00 1.221E+03 4.549E+03 2.829E+03 6.677E01 3.004E01 A16 0.000E+00 0.000E+00 0.000E+00 1.581E+03 1.047E01 3.620E02 Phase Difference Function Coefficient C2 C4 C6 C8 C10 C12 C14 C16 2.752E+02 1.468E+02 1.020E+04 5.237E+04 5.244E+04 1.016E+05 5.171E+05 4.089E+06

(39) Regarding the imaging lens in Example 2, Table 7 shows the values related to the conditional expressions (1) to (11) and Table 8 shows then number of orbicular zones of the diffractive optical surface DOE. As shown in Table 7, the imaging lens in Example 2 satisfies all the conditional expressions (1) to (11). The number of orbicular zones in the effective diameter is 9 and the number of orbicular zones in the area through which rays converging on the optical axis pass is 4, which satisfies the condition to suppress flare.

(40) FIG. 4 shows spherical aberration (mm), astigmatism (mm), distortion (%), and chromatic aberration of magnification (m) of the imaging lens in Example 2. As shown in FIG. 4, the imaging lens in Example 2 also corrects chromatic aberrations and other aberrations properly. It is sufficiently low-profile with a ratio to diagonal of 0.75, and offers high brightness with an F-value of 2.4 and a wide field of view (2w) of 83 degrees.

Example 3

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

(42) TABLE-US-00003 TABLE 3 in mm f = 2.00 Fno = 2.4 () = 41.5 ih = 1.79 TLA = 2.69 bf = 0.94 Surface Data Surface No. i Curvature Radius r Surface Distance d Refractive Index Nd Abbe Number d (Object Surface) Infinity Infinity 1* 1.338 0.377 1.544 55.57 2* Infinity 0.025 3 (Stop) Infinity 0.401 4*DOE 1.110 0.343 1.635 23.97 5* 3.494 0.180 6* 0.541 0.425 1.544 55.57 7* 0.724 0.200 8 Infinity 0.210 1.517 64.20 9 Infinity 0.589 Image Plane Constituent Lens Data Lens Start Surface Focal Length 1 1 2.46 2 4 2.99 3 6 2.16 Diffractive Optical Surface Focal Length 4th Surface 28.262 Aspheric Surface Data 1st Surface 2nd Surface 4th Surface 5th Surface 6th Surface 7th Surface k 8.957E01 5.881E+01 3.080E+00 7.707E+00 6.127E+00 1.150E+00 A4 1.270E02 3.551E01 1.760E+00 4.727E+00 8.152E01 1.407E+00 A6 1.480E+00 1.077E+00 2.250E+01 3.484E+01 2.311E01 2.065E+00 A8 7.016E+00 2.269E+01 2.285E+02 2.013E+02 1.516E+00 2.328E+00 A10 2.257E+01 1.625E+02 1.339E+03 7.669E+02 2.488E+00 1.825E+00 A12 2.394E+01 5.645E+02 3.805E+03 1.796E+03 1.806E+00 9.086E01 A14 0.000E+00 8.057E+02 4.421E+03 2.385E+03 6.498E01 2.527E01 A16 0.000E+00 0.000E+00 0.000E+00 1.357E+03 9.370E02 2.948E02 Phase Difference Function Coefficient C2 C4 C6 C8 C10 C12 C14 C16 1.894E+02 5.100E+02 7.771E+03 4.863E+04 1.030E+05 1.979E+05 4.731E+06 1.209E+07

(43) Regarding the imaging lens in Example 3, Table 7 shows the values related to the conditional expressions (1) to (11) and Table 8 shows then number of orbicular zones of the diffractive optical surface DOE. As shown in Table 7, the imaging lens in Example 3 satisfies all the conditional expressions (1) to (11). The number of orbicular zones in the effective diameter is 10 and the number of orbicular zones in the area through which rays converging on the optical axis pass is 4, which satisfies the condition to suppress flare.

(44) FIG. 6 shows spherical aberration (mm), astigmatism (mm), distortion (%), and chromatic aberration of magnification (m) of the imaging lens in Example 3. As shown in FIG. 6, the imaging lens in Example 3 also corrects chromatic aberrations and other aberrations properly. It is sufficiently low-profile with a ratio to diagonal of 0.75 and offers high brightness with an F-value of 2.4 and a wide field of view (2) of 83 degrees.

Example 4

(45) The basic lens data of Example 4 is shown in Table 4 below.

(46) TABLE-US-00004 TABLE 4 in mm f = 2.00 Fno = 2.3 () = 41.5 ih = 1.79 TLA = 2.68 bf = 0.92 Surface Data Surface No. i Curvature Radius r Surface Distance d Refractive Index Nd Abbe Number d (Object Surface) Infinity Infinity 1* 1.308 0.381 1.544 55.57 2* Infinity 0.023 3 (Stop) Infinity 0.383 4*DOE 1.097 0.338 1.635 23.97 5* 3.917 0.186 6* 0.545 0.452 1.544 55.57 7* 0.746 0.200 8 Infinity 0.210 1.517 64.20 9 Infinity 0.586 Image Plane Constituent Lens Data Lens Start Surface Focal Length 1 1 2.41 2 4 2.72 3 6 2.08 Diffractive Optical Surface Focal Length 4th Surface 32.568 Aspheric Surface Data 1st Surface 2nd Surface 4th Surface 5th Surface 6th Surface 7th Surface k 1.313E+00 9.900E+01 3.393E+00 1.806E+01 6.210E+00 1.373E+00 A4 9.412E02 4.348E01 2.086E+00 5.024E+00 8.623E01 1.300E+00 A6 2.377E+00 2.055E+00 2.767E+01 3.860E+01 5.006E01 1.988E+00 A8 1.267E+01 3.245E+01 2.855E+02 2.327E+02 9.862E01 2.278E+00 A10 3.970E+01 2.088E+02 1.757E+03 9.269E+02 2.006E+00 1.794E+00 A12 4.237E+01 6.865E+02 5.392E+03 2.258E+03 1.604E+00 8.986E01 A14 0.000E+00 9.721E+02 6.919E+03 3.091E+03 6.241E01 2.526E01 A16 0.000E+00 0.000E+00 0.000E+00 1.800E+03 9.648E02 2.990E02 Phase Difference Function Coefficient C2 C4 C6 C8 C10 C12 C14 C16 1.643E+02 5.158E+02 7.789E+03 4.861E+04 1.035E+05 1.921E+05 4.700E+06 1.189E+07

(47) Regarding the imaging lens in Example 4, Table 7 shows the values related to the conditional expressions (1) to (11) and Table 8 shows then number of orbicular zones of the diffractive optical surface DOE. As shown in Table 7, the imaging lens in Example 4 satisfies all the conditional expressions (1) to (11). The number of orbicular zones in the effective diameter is 8 and the number of orbicular zones in the area through which rays converging on the optical axis pass is 3, which satisfies the condition to suppress flare.

(48) FIG. 8 shows spherical aberration (mm), astigmatism (mm), distortion (%), and chromatic aberration of magnification (m) of the imaging lens in Example 4. As shown in FIG. 8, the imaging lens in Example 4 also corrects chromatic aberrations and other aberrations properly. It is sufficiently low-profile with a ratio to diagonal of 0.75 and offers high brightness with an F-value of 2.3 and a wide field of view (2) of 83 degrees.

Example 5

(49) The basic lens data of Example 5 is shown in Table 5 below.

(50) TABLE-US-00005 TABLE 5 in mm f = 2.00 Fno = 2.3 () = 41.6 ih = 1.79 TLA = 2.66 bf = 0.94 Surface Data Surface No. i Curvature Radius r Surface Distance d Refractive Index Nd Abbe Number d (Object Surface) Infinity Infinity 1* 1.306 0.386 1.544 55.57 2* Infinity 0.020 3 (Stop) Infinity 0.382 4*DOE 1.080 0.347 1.635 23.97 5* 3.262 0.193 6* 0.515 0.397 1.544 55.57 7* 0.655 0.200 8 Infinity 0.210 1.517 64.20 9 Infinity 0.606 Image Plane Constituent Lens Data Lens Start Surface Focal Length 1 1 2.40 2 4 2.94 3 6 2.21 Diffractive Optical Surface Focal Length 4th Surface 32.568 Aspheric Surface Data 1st Surface 2nd Surface 4th Surface 5th Surface 6th Surface 7th Surface k 7.395E01 9.900E+01 3.304E+00 1.398E+01 5.392E+00 2.515E+00 A4 1.934E02 4.257E01 1.877E+00 4.765E+00 8.662E01 1.089E+00 A6 1.909E+00 1.946E+00 2.690E+01 3.680E+01 2.005E01 1.838E+00 A8 1.095E+01 3.150E+01 2.982E+02 2.221E+02 1.906E+00 2.309E+00 A10 3.736E+01 2.058E+02 1.900E+03 8.880E+02 3.472E+00 1.991E+00 A12 4.186E+01 6.865E+02 5.960E+03 2.183E+03 2.907E+00 1.094E+00 A14 0.000E+00 9.721E+02 7.792E+03 3.024E+03 1.219E+00 3.364E01 A16 0.000E+00 0.000E+00 0.000E+00 1.779E+03 2.052E01 4.327E02 Phase Difference Function Coefficient C2 C4 C6 C8 C10 C12 C14 C16 1.643E+02 5.158E+02 7.789E+03 4.861E+04 1.035E+05 1.728E+05 4.676E+06 1.189E+07

(51) Regarding the imaging lens in Example 5, Table 7 shows the values related to the conditional expressions (1) to (11) and Table 8 shows then number of orbicular zones of the diffractive optical surface DOE. As shown in Table 7, the imaging lens in Example 5 satisfies all the conditional expressions (1) to (11). The number of orbicular zones in the effective diameter is 7 and the number of orbicular zones in the area through which rays converging on the optical axis pass is 3, which satisfies the condition to suppress flare.

(52) FIG. 10 shows spherical aberration (mm), astigmatism (mm), distortion (%), and chromatic aberration of magnification (m) of the imaging lens in Example 5. As shown in FIG. 10, the imaging lens in Example 5 also corrects chromatic aberrations and other aberrations properly. It is sufficiently low-profile with a ratio to diagonal of 0.75 and offers high brightness with an F-value of 2.3 and a wide field of view (2) of 83 degrees.

Example 6

(53) The basic lens data of Example 6 is shown in Table 6 below.

(54) TABLE-US-00006 TABLE 6 in mm f = 1.93 Fno = 2.2 () = 41.6 ih = 1.79 TLA = 2.61 bf = 0.93 Surface Data Surface No. i Curvature Radius r Surface Distance d Refractive Index Nd Abbe Number d (Object Surface) Infinity Infinity 1* 1.317 0.328 1.544 55.57 2* Infinity 0.020 3 (Stop) Infinity 0.400 4*DOE 0.870 0.313 1.635 23.97 5* 1.182 0.227 6* 0.654 0.389 1.535 55.66 7* 0.735 0.500 8 Infinity 0.210 1.517 64.20 9 Infinity 0.292 Image Plane Constituent Lens Data Lens Start Surface Focal Length 1 1 2.42 2 4 10.13 3 6 4.15 Diffractive Optical Surface Focal Length 4th Surface 48.072 Aspheric Surface Data 1st Surface 2nd Surface 4th Surface 5th Surface 6th Surface 7th Surface k 1.302E+00 9.900E+01 2.400E02 5.556E01 5.654E+00 2.911E+00 A4 2.466E01 4.043E01 1.422E+00 2.123E+00 7.230E01 7.396E01 A6 5.941E02 5.880E01 1.082E+01 9.162E+00 7.584E01 1.081E+00 A8 5.444E+00 1.570E+01 1.093E+02 2.734E+01 2.479E01 1.180E+00 A10 1.210E+01 1.278E+02 5.840E+02 3.373E+01 1.630E01 8.695E01 A12 3.420E+01 5.448E+02 1.214E+03 3.989E+01 1.893E01 4.006E01 A14 2.577E+02 9.302E+02 7.761E+02 3.817E+01 6.901E02 1.018E01 A16 3.691E+02 0.000E+00 0.000E+00 7.417E+01 9.064E03 1.067E02 Phase Difference Function Coefficient C2 C4 C6 C8 C10 C12 C14 C16 1.113E+02 8.623E+02 2.400E+03 1.248E+04 3.955E+04 1.074E+04 7.774E+04 0.000E+00

(55) Regarding the imaging lens in Example 6, Table 7 shows the values related to the conditional expressions (1) to (11) and Table 8 shows then number of orbicular zones of the diffractive optical surface DOE. As shown in Table 7, the imaging lens in Example 6 satisfies all the conditional expressions (1) to (11). The number of orbicular zones in the effective diameter is 5 and the number of orbicular zones in the area through which rays converging on the optical axis pass is 2, which satisfies the condition to suppress flare.

(56) FIG. 12 shows spherical aberration (mm), astigmatism (mm), distortion (%), and chromatic aberration of magnification (m) of the imaging lens in Example 6. As shown in FIG. 12, the imaging lens in Example 6 also corrects chromatic aberrations and other aberrations properly. It is sufficiently low-profile with a ratio to diagonal of 0.75 and offers high brightness with an F-value of 2.3 and a wide field of view (2) of 83 degrees.

(57) TABLE-US-00007 TABLE 7 Exam- Exam- Exam- Exam- Exam- Exam- ple 1 ple 2 ple 3 ple 4 ple 5 ple 6 (1) fdoe/f 9.01 9.73 14.14 16.27 16.26 24.96 (2) d1 31.60 31.60 31.60 31.60 31.60 31.60 d2 (3) d3 31.60 31.60 31.60 31.60 31.60 31.69 d2 (4) ih/f 0.91 0.90 0.90 0.90 0.89 0.93 (5) t3/|r3| 0.39 0.33 0.36 0.35 0.35 0.46 (6) (r1 + 0.85 1.00 1.00 1.00 1.00 1.00 r2)/ (r1 r2) (7) (r3 + 2.10 3.06 1.93 1.78 1.99 6.58 r4)/ (r3 r4) (8) f1/f 1.24 1.18 1.23 1.20 1.20 1.26 (9) f2/f 1.64 2.54 1.49 1.36 1.47 5.26 (10) f3/f 1.16 1.67 1.08 1.04 1.10 2.16 (11) f2/(f1 + 0.68 0.89 0.65 0.61 0.64 1.54 f3)

(58) TABLE-US-00008 TABLE 8 Exam- Exam- Exam- Exam- Exam- Exam- ple 1 ple 2 ple 3 ple 4 ple 5 ple 6 Number of 8 9 10 8 7 5 Orbicular Zones in Effective Diameter Number of 4 4 4 3 3 2 Orbicular Zones in Area through which Rays Converging on Optical Axis Pass

(59) As explained so far, the imaging lens in the above examples according to the preferred embodiment of the present invention are low-profile and compact enough to be applicable to the low-profile high-density image sensors in the latest mobile terminals, etc. They also offer high brightness and a wide field of view and correct various aberrations properly. These high-performance imaging lenses are each composed of three constituent lenses and can be supplied at low cost.

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

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

(62) According to the present invention, there is provided a high-performance low-cost imaging lens, composed of three constituent lenses, which is low-profile and compact enough to be applicable to the latest low-profile mobile terminals and capable of correcting various aberrations properly, particularly chromatic aberrations.