Image capturing optical lens

Abstract

To provide an optical lens, in particular an image capturing optical lens.SOLUTION: An image capturing optical lens provided herein comprises, in order from an object side to an image side, a first lens having positive refractive power, a second lens having negative refractive power, a third lens having positive refractive power, and a fourth lens having positive refractive power, and satisfies the following relationship expressions: 1.50≤TTL / f≤2.50, 1.00≤f1 / f≤1.50, -12.00≤f2 / d3<-4.00, n1≥1.70, and 1.50≤d7 / d5≤5.00.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to the field of optical lenses, and particularly to an imaging optical lens applicable to portable terminal devices such as smartphones and digital cameras, and imaging devices such as monitors, PC lenses, and in-vehicle lenses.

Background Art

[0002] In recent years, with the booming of various smart devices, the need for miniaturized imaging optical lenses has been increasing. In addition to the reduction of the pixel size of the photosensitive element, current electronic products tend to develop towards an outer shape with good functions and being thin, light, and portable. Therefore, miniaturized imaging optical lenses with good imaging quality have become the mainstream of the current market. In order to obtain excellent imaging quality, a multi-lens structure is often used. Also, with the development of technology and the increasing diversification of user needs, when the pixel area of the photosensitive element is shrinking and the system's requirements for imaging quality are increasing, a four-lens structure is gradually emerging in the lens design. There is a strong desire for an imaging optical lens with good optical performance.

Summary of the Invention

Problems to be Solved by the Invention

[0003] In view of the above problems, an object of the present invention is to provide an imaging optical lens that satisfies the design requirements of having good optical performance.

Means for Solving the Problems

[0004] To solve the above technical problems, an embodiment of the present invention provides an imaging optical lens. The imaging optical lens is composed of a first lens having a positive refractive power, a second lens having a negative refractive power, a third lens having a positive refractive power, and a fourth lens having a positive refractive power in order from the object side to the image side. Let the focal length of the imaging optical lens be f, the focal length of the first lens be f1, the focal length of the second lens be f2, the on-axis thickness of the second lens be d3, the on-axis thickness of the third lens be d5, the on-axis thickness of the fourth lens be d7, and the optical length of the imaging optical lens be TTL. When the refractive index of the first lens is n1, the following conditional expressions (1) to (5) are satisfied. 1.50 ≦ TTL / f ≦ 2.50 (1) 1.00 ≦ f1 / f ≦ 1.50 (2) -12.00 ≦ f2 / d3 < -4.00 (3) n1 ≧ 1.70 (4) 1.50 ≦ d7 / d5 ≦ 5.00 (5)

[0005] Preferably, when the center curvature radius of the object side surface of the third lens is R5 and the center curvature radius of the image side surface of the third lens is R6, the following conditional expression (6) is satisfied. 1.00 ≦ R5 / R6 ≦ 5.00 (6)

[0006] Preferably, when the on-axis distance from the image side surface of the first lens to the object side surface of the second lens is d2, the following conditional expression (7) is satisfied. 1.00 ≦ d3 / d2 ≦ 5.00 (7)

[0007] Preferably, the object side surface of the first lens is convex in the paraxial region. When the on-axis thickness of the first lens is d1, the center curvature radius of the object side surface of the first lens is R1, and the center curvature radius of the image side surface of the first lens is R2, the following conditional expressions (8) to (9) are satisfied. -3.68 ≦ (R1 + R2) / (R1 - R2) ≦ -0.62 (8) 1.27 ≦ d1 / TTL ≦ 5.72 (9)

[0008] Preferably, the second lens has a concave object-side surface and a concave image-side surface in the paraxial region. When the radius of curvature of the center of the object-side surface of the second lens is R3 and the radius of curvature of the center of the image-side surface of the second lens is R4, the following conditional expressions (10) to (12) are satisfied. -2.24 ≦ f2 / f ≦ -0.41 (10) 0.01 ≦ (R3 + R4) / (R3 - R4) ≦ 0.66 (11) 0.44 ≦ d3 / TTL ≦ 4.97 (12)

[0009] Preferably, the third lens has a concave object-side surface and a convex image-side surface in the paraxial region. When the focal length of the third lens is f3, the radius of curvature of the center of the object-side surface of the third lens is R5, and the radius of curvature of the center of the image-side surface of the third lens is R6, the following conditional expressions (13) to (15) are satisfied. 0.77 ≦ f3 / f ≦ 8.67 (13) 0.75 ≦ (R5 + R6) / (R5 - R6) ≦ 120.93 (14) 0.70 ≦ d5 / TTL ≦ 10.64 (15)

[0010] Preferably, the fourth lens has a convex object-side surface. When the focal length of the fourth lens is f4, the radius of curvature of the center of the object-side surface of the fourth lens is R7, and the radius of curvature of the center of the image-side surface of the fourth lens is R8, the following conditional expressions (16) to (18) are satisfied. 0.45 ≦ f4 / f ≦ 2.63 (16) -4.89 ≦ (R7 + R8) / (R7 - R8) ≦ -0.28 (17) 3.47 ≦ d7 / TTL ≦ 16.14 (18)

[0011] Preferably, the first lens, the second lens, the third lens, and the fourth lens are made of glass material.

[0012] Preferably, the aperture value FNO of the imaging optical lens is 2 or less.

[0013] Preferably, when the image height of the imaging optical lens is IH, the following conditional expression (19) is satisfied. TTL / IH≦6.93 (19)

Advantages of the Invention

[0014] The imaging optical lens according to the present invention has excellent optical characteristics and good optical performance, and can be particularly applied to an imaging lens unit of a mobile phone, an in-vehicle lens, and a WEB imaging lens composed of an imaging element such as a CCD or a CMOS for high pixels.

[0015] To more clearly explain the technical solutions of the embodiments of the present invention, the drawings necessary for the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings on the premise of not performing creative labor.

Brief Description of the Drawings

[0016]

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Embodiments for Carrying Out the Invention

[0017] In order to make the objectives, solutions, and advantages of the present invention clearer, the following will describe each embodiment of the present invention in detail with reference to the drawings. It can be understood by those skilled in the art that many technical details are described in order to better understand the present invention in each embodiment of the present invention. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solutions claimed by the present invention can also be realized.

[0018] (First Embodiment) Referring to the drawings, the present invention provides an imaging optical lens 10. The imaging optical lens 10 according to the first embodiment of the present invention includes a total of four lenses as shown in FIG. 1. Specifically, the imaging optical lens 10 includes a first lens L1, a diaphragm S1, a second lens L2, a third lens L3, and a fourth lens L4 in order from the object side to the image side. Optical elements such as optical filters GF1 and GF2 may be installed between the fourth lens L5 and the image plane Si.

[0019] In this embodiment, the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 are all made of glass material. By appropriately selecting the glass lens, the optical performance of the imaging optical lens can be improved. In other alternative embodiments, each lens may be made of other materials.

[0020] When the focal length of the imaging optical lens 10 is f and the optical length of the imaging optical lens 10 is TTL, the conditional expression 1.50 ≤ TTL / f ≤ 2.50 is satisfied. Thereby, the ratio of the optical length TTL to the focal length f of the imaging optical lens 10 is defined. By falling below the upper limit value of the conditional expression, the optical length can be controlled to be shortened, facilitating miniaturization. On the other hand, by exceeding the lower limit value of the conditional expression, correction of distortion aberration and axial chromatic aberration can be facilitated, and good optical performance can be maintained.

[0021] When the focal length of the first lens L1 is f1, the conditional expression 1.00 ≦ f1 / f ≦ 1.50 is satisfied. This defines the ratio of the focal length f1 of the first lens L1 to the focal length of the imaging optical lens 10. By reasonably distributing the optical focal length of the system, the system has excellent imaging quality and low sensitivity.

[0022] When the focal length of the second lens L2 is f2 and the on-axis thickness of the second lens L2 is d3, the conditional expression -12.00 ≦ f2 / d3 < -4.00 is satisfied. When the above conditional expression is satisfied, it is advantageous for relaxing the change in the incident angle of light rays with a large viewing angle, propagating the imaging optical lens 10 smoothly, maintaining the refractive power intensity of the second lens L2, improving chromatic aberration, and enhancing imaging quality.

[0023] When the refractive index of the first lens L1 is n1, the conditional expression n1 ≧ 1.70 is satisfied. It is preferable to select and employ a high refractive index material for the first lens L1, which is advantageous for reducing the front aperture diameter and improving imaging quality.

[0024] When the on-axis thickness of the third lens L3 is d5 and the on-axis thickness of the fourth lens L4 is d7, the conditional expression 1.50 ≦ d7 / d5 ≦ 5.00 is satisfied. Within the range defined by the conditional expression, it is advantageous for shortening the optical length of the imaging optical lens 10.

[0025] When the central radius of curvature of the object side surface of the third lens L3 is R5 and the central radius of curvature of the image side surface of the third lens L3 is R6, the conditional expression 1.00 ≦ R5 / R6 ≦ 5.00 is satisfied. This defines the shape of the third lens L3. Within this range, the degree of deflection of light rays passing through the lens can be relaxed, and chromatic aberration can be effectively corrected, with the chromatic aberration being |LC| ≦ 1.2 μm.

[0026] When the on-axis distance from the image side surface of the first lens L1 to the object side surface of the second lens L2 is d2, the conditional expression 1.00 ≦ d3 / d2 ≦ 5.00 is satisfied. Within the range defined by the conditional expression, it is advantageous for shortening the optical length of the imaging optical lens 10.

[0027] In this embodiment, the first lens L1 has a convex object-side surface and a concave image-side surface in the paraxial region, and the first lens L1 has a positive refractive power. In other alternative embodiments, the object-side surface and the image-side surface of the first lens L1 may be arranged in other concave-convex distribution situations.

[0028] The imaging optical lens 10 further satisfies the conditional expression 0.50 ≦ f1 / f ≦ 2.24. This defines the ratio of the focal length f1 of the first lens L1 to the focal length of the imaging optical lens 10. Within this range, it is advantageous for realizing an ultra-wide angle. Preferably, the conditional expression 0.80 ≦ f1 / f ≦ 1.79 is satisfied.

[0029] When the central radius of curvature of the object-side surface of the first lens L1 is R1 and the central radius of curvature of the image-side surface of the first lens L1 is R2, the conditional expression -3.68 ≦ (R1 + R2) / (R1 - R2) ≦ -0.62 is satisfied. This defines the shape of the first lens L1. Within this range, it is advantageous for realizing an ultra-wide angle. Preferably, the conditional expression -2.30 ≦ (R1 + R2) / (R1 - R2) ≦ -0.77 is satisfied.

[0030] When the on-axis thickness of the first lens L1 is d1, the conditional expression 1.27 ≦ d1 / TTL ≦ 5.72 is satisfied. Within the range defined by the conditional expression, it is advantageous for realizing miniaturization. Preferably, the conditional expression 2.03 ≦ d1 / TTL ≦ 4.57 is satisfied.

[0031] In this embodiment, the second lens L2 has a concave object-side surface and a concave image-side surface in the paraxial region, and the second lens L2 has a negative refractive power. In other alternative embodiments, the object-side surface and the image-side surface of the second lens L2 may be arranged in other concave-convex distribution situations.

[0032] In this embodiment, the imaging optical lens 10 satisfies the conditional expression -2.24 ≤ f2 / f ≤ -0.41. This defines the ratio of the focal length f2 of the second lens L2 to the focal length of the imaging optical lens 10. Within this range, the amount of field curvature of the system can be effectively balanced. Preferably, it satisfies the conditional expression -1.40 ≤ f2 / f ≤ -0.51.

[0033] When the radius of curvature of the center of the object side surface of the second lens L2 is R3 and the radius of curvature of the center of the image side surface of the second lens L2 is R4, it satisfies the conditional expression 0.01 ≤ (R3 + R4) / (R3 - R4) ≤ 0.66. This defines the shape of the second lens L2. Within this range, it is advantageous for realizing an ultra-wide angle. Preferably, it satisfies the conditional expression 0.01 ≤ (R3 + R4) / (R3 - R4) ≤ 0.53.

[0034] The imaging optical lens 10 further satisfies the conditional expression 0.44 ≤ d3 / TTL ≤ 4.97. Within the range defined by the conditional expression, it is advantageous for realizing miniaturization. Preferably, it satisfies the conditional expression 0.70 ≤ d3 / TTL ≤ 3.98.

[0035] The third lens L3 has a concave surface on the object side in the paraxial region and a convex surface on the image side in the paraxial region, and the third lens L3 has a positive refractive power. In other alternative embodiments, the object side surface and the image side surface of the third lens L3 may be arranged in other concave-convex distribution situations.

[0036] When the focal length of the third lens L3 is f3, it satisfies the conditional expression 0.77 ≤ f3 / f ≤ 8.67. By a reasonable distribution of the refractive power, the system has excellent imaging quality and low sensitivity. Preferably, it satisfies the conditional expression 1.24 ≤ f3 / f ≤ 6.93.

[0037] The imaging optical lens 10 further satisfies the conditional expression 0.75 ≦ (R5 + R6) / (R5 - R6) ≦ 120.93. Thereby, the shape of the third lens L3 is defined. Within this range, the degree of deflection of light rays can be reduced and chromatic aberration can be effectively corrected. Preferably, it satisfies the conditional expression 1.20 ≦ (R5 + R6) / (R5 - R6) ≦ 96.74.

[0038] The imaging optical lens 10 satisfies the conditional expression 0.70 ≦ d5 / TTL ≦ 10.64. Within the range defined by the conditional expression, it is advantageous for realizing miniaturization. Preferably, it satisfies the conditional expression 1.11 ≦ d5 / TTL ≦ 8.51.

[0039] In the present embodiment, the fourth lens L4 has a convex surface on the object side in the paraxial region and a convex surface on the image side in the paraxial region, and the fourth lens L4 has a positive refractive power. In other selectable embodiments, the object side surface and the image side surface of the fourth lens L4 may be arranged in other concave-convex distribution situations.

[0040] When the focal length of the fourth lens L4 is f4, it satisfies the conditional expression 0.45 ≦ f4 / f ≦ 2.63. By a reasonable distribution of refractive power, the system has excellent imaging quality and low sensitivity. Preferably, it satisfies the conditional expression 0.73 ≦ f4 / f ≦ 2.10.

[0041] When the on-axis thickness of the fourth lens L4 is d7, it satisfies the conditional expression 3.47 ≦ d7 / TTL ≦ 16.14. Within the range defined by the conditional expression, it is advantageous for realizing miniaturization. Preferably, it satisfies the conditional expression 5.55 ≦ d7 / TTL ≦ 12.92.

[0042] In the present embodiment, when the angle of view in the diagonal direction of the imaging optical lens 10 is FOV, it satisfies the conditional expression FOV ≧ 32.42°. Thereby, it is advantageous for realizing wide-angleization. Preferably, it satisfies the conditional expression FOV ≧ 32.75°.

[0043] In this embodiment, when the image height of the imaging optical lens 10 is IH, the conditional expression TTL / IH ≤ 6.93 is satisfied. This is advantageous for achieving miniaturization. Preferably, the conditional expression TTL / IH ≤ 6.73 is satisfied.

[0044] In this embodiment, the aperture value FNO of the imaging optical lens 10 is 2 or less. This achieves a large aperture and excellent imaging performance of the imaging optical lens.

[0045] The imaging optical lens 10 has good optical performance. Depending on the characteristics of the imaging optical lens 10, the imaging optical lens 10 can be particularly applied to in-vehicle lenses, imaging lens units of mobile phones, and WEB imaging lenses composed of imaging elements such as CCDs and CMOSs for high-pixel applications.

[0046] Hereinafter, the imaging optical lens 10 of the present invention will be described using examples. The reference signs described in each example are as shown below. The units of the focal length, the on-axis distance, the central radius of curvature, and the on-axis thickness are mm.

[0047] TTL is the optical length (the on-axis distance from the object side surface of the first lens L1 to the image plane Si), and the unit is mm. The aperture value FNO refers to the ratio of the effective focal length of the imaging optical lens to the entrance pupil diameter.

[0048] Table 1 shows the design data of the imaging optical lens 10 according to the first embodiment of the present invention.

[0049]

Table 1

[0050] Here, the meanings of the respective reference signs are as follows. S1: Aperture R: Radius of curvature at the center of the optical surface R1: Central radius of curvature of the object side surface of the first lens L1 R2: Central radius of curvature of the image side surface of the first lens L1 R3: Center curvature radius of the object side surface of the second lens L2 R4: Center curvature radius of the image side surface of the second lens L2 R5: Center curvature radius of the object side surface of the third lens L3 R6: Center curvature radius of the image side surface of the third lens L3 R7: Center curvature radius of the object side surface of the fourth lens L4 R8: Center curvature radius of the image side surface of the fourth lens L4 R9: Center curvature radius of the object side surface of the optical filter GF1 R10: Center curvature radius of the image side surface of the optical filter GF1 R11: Center curvature radius of the object side surface of the optical filter GF2 R12: Center curvature radius of the image side surface of the optical filter GF2 d: Axial thickness of the lens, axial distance between lenses d0: Axial distance from the aperture S1 to the object side surface of the first lens L1 d1: Axial thickness of the first lens L1 d2: Axial distance from the image side surface of the first lens L1 to the object side surface of the second lens L2 d3: Axial thickness of the second lens L2 d4: Axial distance from the image side surface of the second lens L2 to the object side surface of the third lens L3 d5: Axial thickness of the third lens L3 d6: Axial distance from the image side surface of the third lens L3 to the object side surface of the fourth lens L4 d7: Axial thickness of the fourth lens L4 d8: Axial distance from the image side surface of the fourth lens L4 to the object side surface of the optical filter GF1 d9: Axial thickness of the optical filter GF1 d10: Axial distance from the image side surface of the optical filter GF1 to the object side surface of the optical filter GF2 d11: Axial thickness of the optical filter GF2 d12: Axial distance from the image side surface of the optical filter GF2 to the image plane Si nd: Refractive index of the d line (the d line is green light with a wavelength of 550 nm) nd1: Refractive index of the d line of the first lens L1 nd2: Refractive index of the d line of the second lens L2 nd3: Refractive index of the d-line of the third lens L3 nd4: Refractive index of the d-line of the fourth lens L4 ndg1: Refractive index of the d-line of the optical filter GF1 ndg2: Refractive index of the d-line of the optical filter GF2 vd: Abbe number v1: Abbe number of the first lens L1 v2: Abbe number of the second lens L2 v3: Abbe number of the third lens L3 v4: Abbe number of the fourth lens L4 vg1: Abbe number of the optical filter GF1 vg2: Abbe number of the optical filter GF2

[0051] FIG. 2 and FIG. 3 are schematic diagrams showing the axial chromatic aberration and the lateral chromatic aberration after light with wavelengths of 960 nm, 940 nm, and 920 nm passes through the imaging optical lens 10 according to the first embodiment. FIG. 4 is a schematic diagram showing the field curvature and the distortion aberration after light with a wavelength of 940 nm passes through the imaging optical lens 10 according to the first embodiment. In FIG. 4, the field curvature S is the field curvature in the sagittal direction, and T is the field curvature in the tangential direction.

[0052] Table 7 below shows the values corresponding to various numerical values and parameters defined by conditional expressions in each example.

[0053] As shown in Table 7, the first embodiment satisfies each conditional expression.

[0054] In this embodiment, the entrance pupil diameter ENPD of the imaging optical lens 10 is 2.517 mm, the full field image height IH is 2.203 mm, the angle of view FOV in the diagonal direction is 50.99°, the imaging optical lens 10 has a large aperture and good optical performance, its axial and off-axis chromatic aberrations are sufficiently corrected, and it has excellent optical characteristics.

[0055] (Second Embodiment) The second embodiment is basically the same as the first embodiment, and the meanings of the reference signs are also the same as those in the first embodiment. Therefore, only the differences are shown below.

[0056] FIG. 5 shows an imaging optical lens 20 according to the second embodiment of the present invention.

[0057] Table 2 shows the design data of the imaging optical lens 20 according to the second embodiment of the present invention.

[0058] [Table 2]

[0059] FIGS. 6 and 7 are schematic diagrams showing the axial chromatic aberration and lateral chromatic aberration after light having wavelengths of 960 nm, 940 nm, and 920 nm passes through the imaging optical lens 20 according to the second embodiment. FIG. 8 is a schematic diagram showing the field curvature and distortion after light having a wavelength of 940 nm passes through the imaging optical lens 20 according to the second embodiment. In FIG. 8, the field curvature S is the field curvature in the sagittal direction, and T is the field curvature in the tangential direction.

[0060] As shown in Table 7, the second embodiment satisfies each conditional expression.

[0061] In the present embodiment, the entrance pupil diameter ENPD of the imaging optical lens 20 is 2.509 mm, the full field image height IH is 2.203 mm, the angle of view FOV in the diagonal direction is 53.94°, the imaging optical lens 20 has a large aperture and good optical performance, its axial and off-axis chromatic aberrations are sufficiently corrected, and it has excellent optical characteristics.

[0062] (Third Embodiment) The third embodiment is basically the same as the first embodiment, and the meanings of the reference numerals are also the same as those in the first embodiment. Therefore, only the differences are shown below.

[0063] FIG. 9 shows an imaging optical lens 30 according to the third embodiment of the present invention.

[0064] Table 3 shows the design data of the imaging optical lens 30 according to the third embodiment of the present invention.

[0065]

Table 3

[0066] Figures 10 and 11 are schematic diagrams showing the axial chromatic aberration and the lateral chromatic aberration after light with wavelengths of 960 nm, 940 nm, and 920 nm has passed through the imaging optical lens 30 according to the third embodiment. Figure 12 is a schematic diagram showing the field curvature and the distortion aberration after light with a wavelength of 940 nm has passed through the imaging optical lens 30 according to the third embodiment. In Figure 12, the field curvature S is the field curvature in the sagittal direction, and T is the field curvature in the tangential direction.

[0067] Hereinafter, Table 7 lists the numerical values corresponding to the respective conditional expressions in the present embodiment according to the above conditional expressions. Obviously, the imaging optical lens 30 of the present embodiment satisfies the above conditional expressions.

[0068] In the present embodiment, the entrance pupil diameter ENPD of the imaging optical lens 30 is 3.352 mm, the full field image height IH is 2.203 mm, the angle of view FOV in the diagonal direction is 36.52°, and the imaging optical lens 30 has a large aperture and good optical performance, and its axial and off-axis chromatic aberrations are sufficiently corrected, and it has excellent optical characteristics.

[0069] (Fourth Embodiment) The fourth embodiment is basically the same as the first embodiment, and the meanings of the reference signs are also the same as those in the first embodiment. Therefore, only the differences are shown below.

[0070] Figure 13 shows the imaging optical lens 40 according to the fourth embodiment of the present invention.

[0071] Table 4 shows the design data of the imaging optical lens 40 according to the fourth embodiment of the present invention.

[0072]

Table 4

[0073] FIG. 14 and FIG. 15 are schematic diagrams showing the axial chromatic aberration and lateral chromatic aberration after light with wavelengths of 960 nm, 940 nm, and 920 nm passes through the imaging optical lens 40 according to the fourth embodiment. FIG. 16 is a schematic diagram showing the field curvature and distortion aberration after light with a wavelength of 940 nm passes through the imaging optical lens 40 according to the fourth embodiment. In FIG. 16, the field curvature S is the field curvature in the sagittal direction, and T is the field curvature in the tangential direction.

[0074] In Table 7 below, the numerical values corresponding to the respective conditional expressions in this embodiment are listed according to the above conditional expressions. Obviously, the imaging optical lens 40 of this embodiment satisfies the above conditional expressions.

[0075] In this embodiment, the entrance pupil diameter ENPD of the imaging optical lens 40 is 2.284 mm, the full field image height IH is 2.203 mm, the angle of view FOV in the diagonal direction is 58.47°, the imaging optical lens 40 has a large aperture and good optical performance, its axial and off-axis chromatic aberrations are sufficiently corrected, and it has excellent optical characteristics.

[0076] (Fifth Embodiment) The fifth embodiment is basically the same as the first embodiment, and the meanings of the reference signs are also the same as those in the first embodiment. Therefore, only the differences are shown below.

[0077] FIG. 17 shows the imaging optical lens 50 according to the fifth embodiment of the present invention. The image side surface of the first lens L1 is convex in the paraxial region, and the image side surface of the fourth lens L4 is convex in the paraxial region.

[0078] Table 5 shows the design data of the imaging optical lens 50 according to the fifth embodiment of the present invention.

[0079]

Table 5

[0080] Figs. 18 and 19 are schematic diagrams showing the axial chromatic aberration and lateral chromatic aberration after light with wavelengths of 960 nm, 940 nm, and 920 nm passes through the imaging optical lens 50 according to the fifth embodiment. Fig. 20 is a schematic diagram showing the field curvature and distortion after light with a wavelength of 940 nm passes through the imaging optical lens 50 according to the fifth embodiment. In Fig. 20, the field curvature S is the field curvature in the sagittal direction, and T is the field curvature in the tangential direction.

[0081] Hereinafter, Table 7 lists the numerical values corresponding to the respective conditional expressions in this embodiment according to the above conditional expressions. Obviously, the imaging optical lens 50 of this embodiment satisfies the above conditional expressions.

[0082] In this embodiment, the entrance pupil diameter ENPD of the imaging optical lens 50 is 3.846 mm, the full field image height IH is 2.203 mm, the angular field of view FOV in the diagonal direction is 33.08°, the imaging optical lens 50 has a large aperture and good optical performance, its axial and off-axis chromatic aberrations are sufficiently corrected, and it has excellent optical characteristics.

[0083] (Comparative Embodiment) The sixth embodiment is basically the same as the first embodiment, and the meanings of the reference signs are also the same as those in the first embodiment. Therefore, only the differences are shown below.

[0084] Fig. 21 shows the imaging optical lens 60 of the comparative embodiment.

[0085] Table 6 shows the design data of the imaging optical lens 60 according to the comparative embodiment.

[0086]

Table 6

[0087] Figs. 22 and 23 are schematic diagrams showing the axial chromatic aberration and magnification chromatic aberration after light with wavelengths of 960 nm, 940 nm, and 920 nm passes through the imaging optical lens 60 according to the comparative embodiment. Fig. 24 is a schematic diagram showing the field curvature and distortion aberration after light with a wavelength of 940 nm passes through the imaging optical lens 60 according to the comparative embodiment. In Fig. 24, the field curvature S is the field curvature in the sagittal direction, and T is the field curvature in the tangential direction.

[0088] Hereinafter, Table 7 lists the numerical values corresponding to the respective conditional expressions in this embodiment according to the above conditional expressions. Apparently, the imaging optical lens 60 of this embodiment satisfies the above conditional expressions.

[0089] In this embodiment, the entrance pupil diameter ENPD of the imaging optical lens 60 is 5.398 mm, the full field image height IH is 2.203 mm, and the angular field of view FOV in the diagonal direction is 22.99°.

[0090] Hereinafter, Table 7 lists the numerical values corresponding to the respective conditional expressions in the comparative embodiment according to the above conditional expressions. Apparently, the imaging optical lens 60 of the comparative embodiment does not satisfy the conditional expression -30.00 ≦ f1 / d1 ≦ -8.00 and cannot improve chromatic aberration.

[0091]

Table 7

[0092] As will be understood by those skilled in the art, the above embodiments are specific embodiments for implementing the present invention, and in actual applications, various changes can be made to the form and details without departing from the gist and scope of the present invention.

Claims

1. An imaging optical lens comprising, in order from an object side to an image side, a first lens having positive refractive power, a second lens having negative refractive power, a third lens having positive refractive power, and a fourth lens having positive refractive power, an imaging optical lens, characterized in that the following conditional expressions (1) to (5) are satisfied, when a focal length of the imaging optical lens is f, a focal length of the first lens is f1, a focal length of the second lens is f2, an axial thickness of the second lens is d3, an axial thickness of the third lens is d5, an axial thickness of the fourth lens is d7, an optical length of the imaging optical lens is TTL, and a refractive index of the first lens is n1: 1.50≦TTL / f≦2.50 (1) 1.00≦f1 / f≦1.50 (2) -12.00≦f2 / d3<-4.00 (3) n1≧1.70 (4) 1.50≦d7 / d5≦5.00 (5)

2. 2. The imaging optical lens according to claim 1, wherein the following conditional expression (6) is satisfied when a central radius of curvature of an object-side surface of the third lens is R5 and a central radius of curvature of an image-side surface of the third lens is R6: 1.00≦R5 / R6≦5.00 (6)

3. 2. The imaging optical lens according to claim 1, wherein the following conditional expression (7) is satisfied when an axial distance from an image side surface of the first lens to an object side surface of the second lens is d2: 1.00≦d3 / d2≦5.00 (7)

4. the first lens has an object side surface that is convex on a paraxial line; 2. The imaging optical lens according to claim 1, wherein the following conditional expressions (8) to (9) are satisfied when an axial thickness of the first lens is d1, a central radius of curvature of an object-side surface of the first lens is R1, and a central radius of curvature of an image-side surface of the first lens is R2: -3.68≦(R1+R2) / (R1-R2)≦-0.62 (8) 1.27≦d1 / TTL≦5.72 (9)

5. the second lens has an object side surface that is paraxially concave and an image side surface that is paraxially concave, 2. The imaging optical lens according to claim 1, wherein the following conditional expressions (10) to (12) are satisfied, when a central radius of curvature of an object-side surface of the second lens is R3 and a central radius of curvature of an image-side surface of the second lens is R4. −2.24≦f2 / f≦−0.41 (10) 0.01≦(R3+R4) / (R3-R4)≦0.66 (11) 0.44≦d3 / TTL≦4.97 (12)

6. the third lens has an object side surface that is a paraxial concave surface and an image side surface that is a paraxial convex surface, 2. The imaging optical lens according to claim 1, wherein the following conditional expressions (13) to (15) are satisfied when a focal length of the third lens is f3, a central radius of curvature of the object-side surface of the third lens is R5, and a central radius of curvature of the image-side surface of the third lens is R6. 0.77≦f3 / f≦8.67 (13) 0.75≦(R5+R6) / (R5-R6)≦120.93 (14) 0.70≦d5 / TTL≦10.64 (15)

7. the fourth lens has an object side surface that is convex on a paraxial line; 2. The imaging optical lens according to claim 1, wherein the following conditional expressions (16) to (18) are satisfied when a focal length of the fourth lens is f4, a central radius of curvature of the object-side surface of the fourth lens is R7, and a central radius of curvature of the image-side surface of the fourth lens is R8: 0.45≦f4 / f≦2.63 (16) -4.89≦(R7+R8) / (R7-R8)≦-0.28 (17) 3.47≦d7 / TTL≦16.14 (18)

8. The imaging optical lens according to claim 1 , wherein the first lens, the second lens, the third lens and the fourth lens are made of a glass material.

9. 9. The imaging optical lens according to claim 8, wherein the aperture value FNO of the imaging optical lens is 2 or less.

10. 2. The imaging optical lens according to claim 1, wherein the following conditional expression (19) is satisfied, where IH is an image height of the imaging optical lens: TTL / IH≦6.93 (19)

Images