Imaging lens

Abstract

An imaging lens comprises a first lens, a second lens, a third lens and a fourth lens. The first lens has negative refractive power. The second lens has positive refractive power. The third lens has positive refractive power and comprises a convex surface facing the image side. The fourth lens has negative refractive power. The first lens, the second lens, the third lens and the fourth lens are sequentially arranged from the object side to the image side along the optical axis.

Description

Technical Field

[0001] The invention relates to an imaging lens. Background Art

[0002] The existing imaging lenses used for infrared light have large chromatic aberration, which makes the imaging positions of infrared light of different wavelengths vary greatly. As a result, the imaging lenses can only be used for infrared light of a fixed wavelength. When the wavelength of the infrared light changes, other suitable imaging lenses need to be replaced accordingly, which is very inconvenient for users. Summary of the invention

[0003] In view of this, the main purpose of the present invention is to provide an imaging lens that can effectively reduce the aperture value, effectively improve the resolution, effectively correct the infrared light chromatic aberration, and effectively achieve the confocal function that can be used for infrared lights of different wavelengths.

[0004] The present invention provides an imaging lens comprising a first lens, a second lens, a third lens and a fourth lens. The first lens has a negative refractive power. The second lens has a positive refractive power. The third lens has a positive refractive power and comprises a convex surface facing the image side. The fourth lens has a negative refractive power. The first lens, the second lens, the third lens and the fourth lens are arranged in sequence from the object side to the image side along the optical axis. The imaging lens satisfies at least one of the following conditions: 6.6≤TTL / BFL≤7.5; Vd1 or Vd4 is less than Vd2; 1.34≤|f1 / f|≤2; 0.3≤|f1 / TTL|≤0.55; -205≤f12 / f34≤12; 4≤|R11 / R42|≤10; 0.4≤f2 / TTL≤1; 3≤d36 / BFL≤6; 20%≤(G12+G23+G34+BFL) / d19≤55%; wherein TTL is the distance from the object side surface of the first lens to the imaging surface on the optical axis, BFL is the distance from the image side surface of the fourth lens to the imaging surface on the optical axis, f is the effective focal length of the imaging lens, f1 is the effective focal length of the first lens, and f2 is the effective focal length of the second lens. focal length, f12 is the combined effective focal length of the combination of the first lens and the second lens, f34 is the combined effective focal length of the combination of the third lens and the fourth lens, R11 is the curvature radius of the object side surface of the first lens, R42 is the curvature radius of the image side surface of the fourth lens, d36 is the distance on the optical axis from the object side surface of the second lens to the image side surface of the third lens, d19 is the distance on the optical axis from the object side surface of the first lens to the image side surface of the fourth lens, G12 is the air distance between the first lens and the second lens, G23 is the air distance between the second lens and the third lens, G34 is the air distance between the third lens and the fourth lens, Vd1 is the Abbe coefficient of the first lens, Vd2 is the Abbe coefficient of the second lens, and Vd4 is the Abbe coefficient of the fourth lens.

[0005] Wherein, the first lens has a concave surface facing the image side, and the fourth lens has a concave surface facing the image side.

[0006] Wherein, the second lens has a convex surface facing the object side, the third lens is a biconvex lens, and may further have another convex surface facing the object side.

[0007] Wherein, the fourth lens is a meniscus lens, and may further have a convex surface facing the object side.

[0008] Wherein, the second lens is a biconvex lens, and has a convex surface facing the object side and another convex surface facing the image side.

[0009] Wherein, the third lens is a biconvex lens, and may further have another convex surface facing the object side.

[0010] Wherein, the imaging lens satisfies the following conditions: Vd1 < Vd2; Vd4 < Vd2; where Vd1 is the Abbe number of the first lens, Vd2 is the Abbe number of the second lens, and Vd4 is the Abbe number of the fourth lens.

[0011] Wherein, the imaging lens satisfies the following conditions: Vd1 + Vd4 < Vd2; where Vd1 is the Abbe number of the first lens, Vd2 is the Abbe number of the second lens, and Vd4 is the Abbe number of the fourth lens.

[0012] The imaging lens of the present invention may further include an aperture disposed between the second lens and the third lens. Wherein, the first lens is a biconcave lens, and may further have another concave surface facing the object side.

[0013] The imaging lens of the present invention may further include an aperture disposed between the second lens and the third lens. Wherein, the first lens is a meniscus lens, and may further have a convex surface facing the object side.

[0014] Implementing the imaging lens of the present invention can effectively reduce the aperture value, effectively improve the resolution, effectively correct the infrared chromatic aberration, and effectively achieve the confocal function that infrared light of different wavelengths can be used. Description of the Drawings

[0015] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following specifically enumerates preferred embodiments and describes them in detail in conjunction with the accompanying drawings.

[0016] Figure 1 It is a lens configuration and optical path schematic diagram of the first embodiment of the imaging lens according to the present invention.

[0017] Figure 2 、 3, 4, 5, 6, and 7 are respectively a field curvature diagram, a distortion diagram, a modulation transfer function diagram, a modulation transfer function diagram, a through focus modulation transfer function diagram, and a through focus modulation transfer function diagram of the first embodiment of the imaging lens according to the present invention.

[0018] Figure 8 FIG. 4 is a schematic diagram of lens configuration and optical path of a second embodiment of an imaging lens according to the present invention.

[0019] Fig. 9 , 10 , 11, 12, 13, and 14 are respectively a field curvature diagram, a distortion diagram, a modulation transfer function diagram, a modulation transfer function diagram, a defocus modulation transfer function diagram, and a defocus modulation transfer function diagram of the second embodiment of the imaging lens according to the present invention.

[0020] Fig.15 FIG. 4 is a schematic diagram of lens configuration and optical path of a third embodiment of an imaging lens according to the present invention.

[0021] Fig.16 , 17 , 18, 19, 20, and 21 are respectively a field curvature diagram, a distortion diagram, a modulation transfer function diagram, a modulation transfer function diagram, a defocus modulation transfer function diagram, and a defocus modulation transfer function diagram of the third embodiment of the imaging lens according to the present invention.

[0022] Fig. 22 FIG. 4 is a schematic diagram of lens configuration and optical path of a fourth embodiment of an imaging lens according to the present invention.

[0023] Fig.23 , 24 , 25, 26, 27, and 28 are respectively a field curvature diagram, a distortion diagram, a modulation transfer function diagram, a modulation transfer function diagram, a defocus modulation transfer function diagram, and a defocus modulation transfer function diagram of the fourth embodiment of the imaging lens according to the present invention. DETAILED DESCRIPTION

[0024] The present invention provides an imaging lens, comprising: a first lens having negative refractive power; a second lens having positive refractive power; a third lens having positive refractive power, the third lens including a convex surface facing the image side; and a fourth lens having negative refractive power; wherein the first lens, the second lens, the third lens and the fourth lens are arranged in sequence from the object side to the image side along the optical axis; wherein the imaging lens satisfies at least one of the following conditions: 6.6≤TTL / BFL≤7.5; Vd1 or Vd4 is less than Vd2; 1.34≤|f1 / f|≤2; 0.3≤|f1 / TTL|≤0.55; -205≤f12 / f34≤12; 4≤|R11 / R42|≤10; 0.4≤f2 / TTL≤1; 3≤d36 / BFL≤6; 20%≤(G12+G23+G34+BFL) / d19≤55%; wherein TTL is the distance from the object side of the first lens to the imaging surface on the optical axis, and BFL is the image side of the fourth lens. wherein, as shown in FIG. 1 , the distance from the object side surface of the second lens to the image side surface on the optical axis, f is the effective focal length of the imaging lens, f1 is the effective focal length of the first lens, f2 is the effective focal length of the second lens, f12 is the combined effective focal length of the combination of the first lens and the second lens, f34 is the combined effective focal length of the combination of the third lens and the fourth lens, R11 is the curvature radius of the object side surface of the first lens, R42 is the curvature radius of the image side surface of the fourth lens, d36 is the distance from the object side surface of the second lens to the image side surface of the third lens on the optical axis, d19 is the distance from the object side surface of the first lens to the image side surface of the fourth lens on the optical axis, G12 is the air distance between the first lens and the second lens, G23 is the air distance between the second lens and the third lens, G34 is the air distance between the third lens and the fourth lens, Vd1 is the Abbe coefficient of the first lens, Vd2 is the Abbe coefficient of the second lens, and Vd4 is the Abbe coefficient of the fourth lens. When the imaging lens of the present invention meets the above-mentioned features and conditions, and no other additional features and conditions are required, the basic operation of the imaging lens of the present invention can be achieved.

[0025] Please refer to Table 1, Table 2, Table 4, Table 5, Table 7, Table 8, Table 10 and Table 11 below, wherein Table 1, Table 4, Table 7 and Table 10 are tables of relevant parameters of each lens of the first embodiment to the fourth embodiment of the imaging lens according to the present invention, and Table 2, Table 5, Table 8 and Table 11 are tables of relevant parameters of the aspherical surface of the aspherical lens in Table 1, Table 4, Table 7 and Table 10.

[0026] Figure 1 , 8, 15, and 22 are schematic diagrams of lens configurations and optical paths of the first, second, third, and fourth embodiments of the imaging lens of the present invention, respectively. The first lens L11, L21, L31, and L41 have negative refractive power, and their image-side surfaces S12, S22, S32, and S42 are concave surfaces, and the object-side surfaces S11, S21, S31, and S41 and the image-side surfaces S12, S22, S32, and S42 are all aspherical surfaces.

[0027] The second lenses L12, L22, L32, and L42 are biconvex lenses with positive refractive power, whose object-side surfaces S13, S23, S33, and S43 are convex surfaces, and image-side surfaces S14, S24, S34, and S44 are convex surfaces, and the object-side surfaces S13, S23, S33, and S43 and the image-side surfaces S14, S24, S34, and S44 are all spherical surfaces.

[0028] The third lens L13, L23, L33, L43 is a biconvex lens with positive refractive power, whose object-side surfaces S16, S26, S36, S46 are convex, and image-side surfaces S17, S27, S37, S47 are convex, and the object-side surfaces S16, S26, S36, S46 and image-side surfaces S17, S27, S37, S47 are aspherical surfaces.

[0029] The fourth lens L14, L24, L34, L44 is a meniscus lens with negative refractive power, whose object-side surfaces S18, S28, S38, S48 are convex, and image-side surfaces S19, S29, S39, S49 are concave, and the object-side surfaces S18, S28, S38, S48 and image-side surfaces S19, S29, S39, S49 are aspherical surfaces.

[0030] In addition, the imaging lenses 1, 2, 3, and 4 satisfy at least one of the following conditions (1) to (16):

[0031] 1.34 ≤|f1 / f|≤ 2; (1)

[0032] 6.6 ≤ TTL / BFL ≤ 7.5; (2)

[0033] 0.3 ≤ | f1 / TTL | ≤ 0.55; (3)

[0034] -205 ≤ f12 / f34 ≤ 12; (4)

[0035] 4 ≤|R11 / R42|≤ 10; (5)

[0036] 0.4 ≤ f2 / TTL ≤ 1; (6)

[0037] 0.8 ≤∣R11∣ / (∣R11∣+ R42) ≤ 1; (7)

[0038] 0.15 ≤ R12 / (∣R11∣+ R42) ≤ 0.3; (8)

[0039] 1 ≤∣R11∣ / (∣R11∣- R42) ≤ 1.4; (9)

[0040] 0.1 ≤ R12 / (∣R11∣- R42) ≤ 0.5; (10)

[0041] 3 ≤ d36 / BFL ≤ 6; (11)

[0042] 20% ≤ (G12+G23+G34+BFL) / d19 ≤ 55%; (12)

[0043] Vd1 < Vd2; (13)

[0044] Vd4 < Vd2; (14)

[0045] Vd1+Vd4 < Vd2; (15)

[0046] 1 ≤ Vd2 / (Vd1+Vd4) ≤ 2 (16)

[0047] Wherein, Vd1 is the Abbe coefficient of the first lens L11, L21, L31, L41 in the first to fourth embodiments, Vd2 is the Abbe coefficient of the second lens L12, L22, L32, L42 in the first to fourth embodiments, Vd4 is the Abbe coefficient of the fourth lens L14, L24, L34, L44 in the first to fourth embodiments, f is the effective focal length of the imaging lens 1, 2, 3, 4 in the first to fourth embodiments, f1 is the effective focal length of the first lens L11, L21, L31, L41 in the first to fourth embodiments, f2 is the effective focal length of the second lens L12, L22, L32, L42 in the first to fourth embodiments, and f12 is the effective focal length of the imaging lens 1, 2, 3, 4 in the first to fourth embodiments. In the first to fourth embodiments, the combined effective focal length of the first lens L11, L21, L31, L41 and the second lens L12, L22, L32, L42, f34 is the combined effective focal length of the third lens L13, L23, L33, L43 and the fourth lens L14, L24, L34, L44 in the first to fourth embodiments, R11 is the curvature radius of the object-side surface S11, S21, S31, S41 of the first lens L11, L21, L31, L41 in the first to fourth embodiments, R12 is the curvature radius of the image-side surface S12, S22, S32, S42 of the first lens L11, L21, L31, L41 in the first to fourth embodiments, and R4 2 is the curvature radius of the image-side surface S19, S29, S39, S49 of the fourth lens L14, L24, L34, L44 in the first to fourth embodiments, TTL is the distance between the object-side surface S11, S21, S31, S41 of the first lens L11, L21, L31, L41 and the imaging surface IMA1, IMA2, IMA3, IMA4 on the optical axes OA1, OA2, OA3, OA4 in the first to fourth embodiments, BFL is the distance between the image-side surface S19, S29, S39, S49 of the fourth lens L14, L24, L34, L44 and the imaging surface IMA1, IMA2, IMA3, IMA4 on the optical axes OA1, OA2, OA3, OA4 in the first to fourth embodiments. d19 is the distance between the object-side surface S11, S21, S31, S41 of the first lens L11, L21, L31, L41 and the image-side surface S19, S29, S39, S49 of the fourth lens L14, L24, L34, L44 on the optical axes OA1, OA2, OA3, OA4 in the first to fourth embodiments,In the first to fourth embodiments, G12 is the air gap between the first lenses L11, L21, L31, L41 and the second lenses L12, L22, L32, L42, G23 is the air gap between the second lenses L12, L22, L32, L42 and the third lenses L13, L23, L33, L43 in the first to fourth embodiments, and G34 is the air gap between the third lenses L13, L23, L33, L43 and the fourth lenses L14, L24, L34, L44 in the first to fourth embodiments. This enables the imaging lenses 1, 2, 3, and 4 to effectively reduce the aperture value, effectively improve the resolution, effectively correct the infrared chromatic aberration, and effectively achieve the confocal function that can be used for infrared light of different wavelengths.

[0048] When the condition (1): 1.34 ≤ |f1 / f| ≤ 2 is satisfied, the refractive power can be effectively increased to increase the light-gathering angle. When the condition (2): 6.6 ≤ TTL / BFL ≤ 7.5 is satisfied, the back focal length can be effectively increased to improve the assembly performance. When the condition (3): 0.3 ≤ |f1 / TTL| ≤ 0.55 is satisfied, the total lens length can be effectively shortened. When the condition (4): -205 ≤ f12 / f34 ≤ 12 is satisfied, the aberration can be effectively corrected to improve the resolution. When the condition (5): 4 ≤ |R11 / R42| ≤ 10 is satisfied, the aberration can be effectively corrected to improve the resolution. When the condition (6): 0.4 ≤ f2 / TTL ≤ 1 is satisfied, the sensitivity of the second lens can be effectively reduced, where the sensitivity is the influence amplitude on the tolerance. The lower the sensitivity, the smaller the tolerance influence, and the larger the allowable tolerance range. When the condition (7): 0.8 ≤ |R11| / (|R11| + R42) ≤ 1 is satisfied, the sensitivity of the first lens can be effectively reduced. When the condition (8): 0.15 ≤ R12 / (|R11| + R42) ≤ 0.3 is satisfied, the refractive power can be effectively increased to shorten the total lens length. When the condition (9): 1 ≤ |R11| / (|R11| - R42) ≤ 1.4 is satisfied, the sensitivity of the first lens can be effectively reduced. When the condition (10): 0.1 ≤ R12 / (|R11| - R42) ≤ 0.5 is satisfied, the sensitivity of the first lens can be effectively reduced. When the condition (11): 3 ≤ d36 / BFL ≤ 6 is satisfied, the back focal length can be effectively increased to improve the assembly performance. When the condition (12): 20% ≤ (G12 + G23 + G34 + BFL) / d19 ≤ 55% is satisfied, the back focal length can be effectively increased to improve the assembly performance. When the condition (13), (14), (15) or (16): Vd1 < Vd2, Vd4 < Vd2, Vd1 + Vd4 < Vd2 or 1 ≤ Vd2 / (Vd1 + Vd4) ≤ 2 is satisfied, the confocal function that can be used for infrared light of different wavelengths can already be effectively achieved. Among them, when the condition (16) is 1.4 ≤ Vd2 / (Vd1 + Vd4) ≤ 1.5, the confocal function that can be used for infrared light of different wavelengths can be more effectively achieved.

[0049] The first embodiment of the imaging lens of the present invention is now described in detail. Figure 1 The imaging lens 1 includes a first lens L11, a second lens L12, an aperture ST1, a third lens L13, a fourth lens L14 and a protective glass CG1 in order from the object side to the image side along the optical axis OA1. When imaging, the light from the object side is finally imaged on the imaging surface IMA1. According to the first to sixth paragraphs of [Specific Implementation], the first lens L11 is a biconcave lens, and its object side surface S11 is a concave surface; the object side surface S110 and the image side surface S111 of the protective glass CG1 are both planes; by using the above-mentioned lens, aperture ST1 and a design that satisfies at least one of conditions (1) to (11), the imaging lens 1 can effectively reduce the aperture value, effectively improve the resolution, effectively correct the infrared light chromatic aberration and effectively achieve the confocal function that can be used for infrared light of different wavelengths.

[0050] Table 1 Figure 1 Table of relevant parameters of each lens of imaging lens 1.

[0051] Table 1

[0052]

[0053] The aspheric surface concavity z of the aspheric lens in Table 1 is obtained by the following formula:

[0054] z=ch 2 / {1+[1-(k+1)c 2 h 2 ] 1 / 2}+Ah 4 +Bh 6 +Ch 8 +Dh 10 +Eh 12 +Fh 14 +Gh 16 .

[0055] Where: c: curvature; h: vertical distance from any point on the lens surface to the optical axis; k: cone coefficient; A~G: aspheric coefficients.

[0056] Table 2 is a table of related parameters of the aspherical surface of the aspherical lens in Table 1, wherein k is the conic constant, and A-G are aspherical coefficients.

[0057] Table 2

[0058]

[0059] Table 3 shows the relevant parameter values ​​of the imaging lens 1 of the first embodiment and the calculated values ​​corresponding to conditions (1) to (16). It can be seen from Table 3 that the imaging lens 1 of the first embodiment can meet the requirements of conditions (1) to (16).

[0060] Table 3

[0061]

[0062] In addition, the optical performance of the imaging lens 1 of the first embodiment can also meet the requirements. Figure 2 It can be seen that the field curvature of the imaging lens 1 of the first embodiment is between -0.05mm and 0.01mm. Figure 3 It can be seen that the distortion of the imaging lens 1 of the first embodiment is between -2% and 0%. Figure 4 It can be seen that the modulation transfer function value of the imaging lens 1 of the first embodiment is between 0.56 and 1.0. Figure 5 It can be seen that the modulation transfer function value of the imaging lens 1 of the first embodiment is between 0.52 and 1.0. Figure 6 It can be seen that, for the imaging lens 1 of the first embodiment, when the focus offset is between -0.05 mm and 0.05 mm, the value of the modulation transfer function is between 0.0 and 0.87. Figure 7 It can be seen that, for the imaging lens 1 of the first embodiment, when the focus offset is between -0.05 mm and 0.05 mm, the value of the modulation transfer function is between 0.0 and 0.88. It is obvious that the field curvature and distortion of the imaging lens 1 of the first embodiment can be effectively corrected, and the lens resolution and focal depth can also meet the requirements, thereby obtaining better optical performance. The imaging lens 1 of the first embodiment above meets conditions (1) to (11) and the refractive power and surface shape of Tables 1 and 2, and is one of the preferred embodiments of the present invention.

[0063] The second embodiment of the imaging lens of the present invention is now described in detail. Figure 8 The imaging lens 2 includes a first lens L21, a second lens L22, an aperture ST2, a third lens L23, a fourth lens L24 and a protective glass CG2 in order from the object side to the image side along the optical axis OA2. When imaging, the light from the object side is finally imaged on the imaging surface IMA2. According to the first to sixth paragraphs of [Specific Implementation], the first lens L21 is a meniscus lens, and its object side surface S21 is a convex surface; the object side surface S210 and the image side surface S211 of the protective glass CG2 are both planes; by using the above-mentioned lens, aperture ST2 and a design that satisfies at least one of conditions (1) to (11), the imaging lens 2 can effectively reduce the aperture value, effectively improve the resolution, effectively correct the infrared light chromatic aberration and effectively achieve the confocal function that can be used for infrared light of different wavelengths.

[0064] Table 4 is a table of relevant parameters of each lens of the imaging lens 2 in FIG. 8 .

[0065] Table 4

[0066]

[0067]

[0068] The definition of the aspheric surface concavity z of each lens in Table 4 is the same as the definition of the aspheric surface concavity z of each lens in Table 1 of the first embodiment, and will not be repeated here.

[0069] Table 5 is a table of related parameters of the aspherical surface of the aspherical lens in Table 4, wherein k is the conic constant and A-G are aspherical coefficients.

[0070] Table 5

[0071]

[0072] Table 6 shows the relevant parameter values ​​of the imaging lens 2 of the second embodiment and the calculated values ​​corresponding to conditions (1) to (16). It can be seen from Table 6 that the imaging lens 2 of the second embodiment can meet the requirements of conditions (1) to (16).

[0073] Table 6

[0074]

[0075] In addition, the optical performance of the imaging lens 2 of the second embodiment can also meet the requirements. Fig. 9 It can be seen that the field curvature of the imaging lens 2 of the second embodiment is between -0.03mm and 0.035mm. Fig.10 It can be seen that the distortion of the imaging lens 2 of the second embodiment is between -1.4% and 0%. Fig.11 It can be seen that the modulation transfer function value of the imaging lens 2 of the second embodiment is between 0.62 and 1.0. Fig.12 It can be seen that the modulation transfer function value of the imaging lens 2 of the second embodiment is between 0.64 and 1.0. Fig.13 It can be seen that, for the imaging lens 2 of the second embodiment, when the focus offset is between -0.05 mm and 0.05 mm, the value of the modulation transfer function is between 0.0 and 0.87. Fig.14It can be seen that, for the imaging lens 2 of the second embodiment, when the focus offset is between -0.05 mm and 0.05 mm, the modulation transfer function value is between 0.0 and 0.88. It is obvious that the field curvature and distortion of the imaging lens 2 of the second embodiment can be effectively corrected, and the lens resolution and focal depth can also meet the requirements, thereby obtaining better optical performance. The imaging lens 2 of the second embodiment above meets conditions (1) to (16) and the refractive power and surface shape of Tables 4 and 5, and is one of the preferred embodiments of the present invention.

[0076] The third embodiment of the imaging lens of the present invention is now described in detail. Please refer to FIG. 15 . The imaging lens 3 includes a first lens L31, a second lens L32, an aperture ST3, a third lens L33, a fourth lens L34 and a protective glass CG3 in order from the object side to the image side along the optical axis OA3. When imaging, the light from the object side is finally imaged on the imaging surface IMA3. According to the first to sixth paragraphs of [Specific Implementation], the first lens L31 is a biconcave lens, and its object side surface S31 is a concave surface; the object side surface S310 and the image side surface S311 of the protective glass CG3 are both planes; by using the above-mentioned lens, aperture ST3 and the design that satisfies at least one of conditions (1) to (16), the imaging lens 3 can effectively reduce the aperture value, effectively improve the resolution, effectively correct the infrared light chromatic aberration and effectively achieve the confocal function that can be used for infrared light of different wavelengths.

[0077] Table 7 is a table of relevant parameters of each lens of the imaging lens 3 in FIG. 15 .

[0078] Table 7

[0079]

[0080]

[0081] The definition of the aspheric surface concavity z of each lens in Table 7 is the same as the definition of the aspheric surface concavity z of each lens in Table 1 of the first embodiment, and will not be repeated here.

[0082] Table 8 is a table of related parameters of the aspherical surface of the aspherical lens in Table 7, wherein k is the conic constant, and A~G are aspherical coefficients.

[0083] Table 8

[0084]

[0085] Table 9 shows the relevant parameter values ​​of the imaging lens 3 of the third embodiment and the calculated values ​​corresponding to conditions (1) to (16). It can be seen from Table 9 that the imaging lens 3 of the third embodiment can meet the requirements of conditions (1) to (16).

[0086] Table 9

[0087]

[0088]

[0089] In addition, the optical performance of the imaging lens 3 of the third embodiment can also meet the requirements. As shown in FIG. 16, the field curvature of the imaging lens 3 of the third embodiment is between -0.045mm and 0.015mm. As shown in FIG. 17, the distortion of the imaging lens 3 of the third embodiment is between -2.0% and 0%. As shown in FIG. 18, the modulation transfer function value of the imaging lens 3 of the third embodiment is between 0.60 and 1.0. As shown in FIG. 19, the modulation transfer function value of the imaging lens 3 of the third embodiment is between 0.58 and 1.0. As shown in FIG. 20, when the focus shift of the imaging lens 3 of the third embodiment is between -0.05mm and 0.05mm, the modulation transfer function value is between 0.0 and 0.88. As shown in FIG. 21, when the focus shift of the imaging lens 3 of the third embodiment is between -0.05mm and 0.05mm, the modulation transfer function value is between 0.0 and 0.88. It is obvious that the field curvature and distortion of the imaging lens 3 of the third embodiment can be effectively corrected, and the lens resolution and focal depth can also meet the requirements, thereby obtaining better optical performance. The imaging lens 3 of the third embodiment above meets conditions (1) to (16) and the refractive power and surface shape of Tables 7 and 8, and is one of the preferred embodiments of the present invention.

[0090] The fourth embodiment of the imaging lens of the present invention is now described in detail. Please refer to FIG. 22 , the imaging lens 4 includes a first lens L41, a second lens L42, an aperture ST4, a third lens L43, a fourth lens L44 and a protective glass CG4 in order from the object side to the image side along the optical axis OA4. When imaging, the light from the object side is finally imaged on the imaging surface IMA4. According to the first to sixth paragraphs of [Specific Implementation], the first lens L41 is a biconcave lens, and its object side surface S41 is a concave surface; the object side surface S410 and the image side surface S411 of the protective glass CG4 are both planes; by using the above-mentioned lens, aperture ST4 and the design that satisfies at least one of conditions (1) to (16), the imaging lens 4 can effectively reduce the aperture value, effectively improve the resolution, effectively correct the infrared light chromatic aberration and effectively achieve the confocal function that can be used for infrared light of different wavelengths.

[0091] Table 10 is a table of relevant parameters of each lens of the imaging lens 4 in FIG. 22 .

[0092] Table 10

[0093]

[0094]

[0095] The definition of the aspheric surface concavity z of each lens in Table 10 is the same as the definition of the aspheric surface concavity z of each lens in Table 1 of the first embodiment, and will not be repeated here.

[0096] Table 11 is a table of related parameters of the aspherical surface of the aspherical lens in Table 10, wherein k is the conic constant and A~G are the aspherical coefficients.

[0097] Table 11

[0098]

[0099] Table 12 shows the relevant parameter values ​​of the imaging lens 4 of the fourth embodiment and the calculated values ​​corresponding to conditions (1) to (16). It can be seen from Table 12 that the imaging lens 4 of the fourth embodiment can meet the requirements of conditions (1) to (16).

[0100] Table 12

[0101]

[0102]

[0103] In addition, the optical performance of the imaging lens 4 of the fourth embodiment can also meet the requirements. Fig.23 It can be seen that the field curvature of the imaging lens 4 of the fourth embodiment is between -0.06mm and 0.02mm. Fig.24 It can be seen that the distortion of the imaging lens 4 of the fourth embodiment is between -2.4% and 0%. Fig.25 It can be seen that the modulation transfer function value of the imaging lens 4 of the fourth embodiment is between 0.44 and 1.0. Fig.26 It can be seen that the modulation transfer function value of the imaging lens 4 of the fourth embodiment is between 0.31 and 1.0. Fig. 27 It can be seen that, for the imaging lens 4 of the fourth embodiment, when the focus offset is between -0.05 mm and 0.05 mm, the value of the modulation transfer function is between 0.0 and 0.88. Fig.28 It can be seen that, for the imaging lens 4 of the fourth embodiment, when the focus offset is between -0.05 mm and 0.05 mm, the modulation transfer function value is between 0.0 and 0.87. It is obvious that the field curvature and distortion of the imaging lens 4 of the fourth embodiment can be effectively corrected, and the lens resolution and focal depth can also meet the requirements, thereby obtaining better optical performance. The imaging lens 4 of the fourth embodiment above meets conditions (1) to (16) and the refractive power and surface shape of Tables 10 and 11, and is one of the preferred embodiments of the present invention.

[0104] Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Those skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. An imaging lens, characterized in that: include: The first lens has negative refractive power; The second lens has positive refractive power; The third lens has positive refractive power, and the third lens includes a convex surface facing the image side; as well as The fourth lens element has negative refractive power; wherein the first lens, the second lens, the third lens and the fourth lens are arranged in sequence from the object side to the image side along the optical axis; The imaging lens satisfies at least one of the following conditions: 6.6≤TTL / BFL≤7.5; Vd1 or Vd4 is less than Vd2; 1.34≤|f1 / f|≤2; 0.3≤|f1 / TTL|≤0.55; -205≤f12 / f34≤12; 4≤|R11 / R42|≤10; 0.4≤f2 / TTL≤1; 3≤d36 / BFL≤6; 20%≤(G12+G23+G34+BFL) / d19≤55%; Wherein, TTL is the distance between the object side surface of the first lens and the imaging surface on the optical axis, BFL is the distance between the image side surface of the fourth lens and the imaging surface on the optical axis, f is the effective focal length of the imaging lens, f1 is the effective focal length of the first lens, f2 is the effective focal length of the second lens, f12 is the combined effective focal length of the first lens and the second lens, f34 is the combined effective focal length of the third lens and the fourth lens, R11 is the curvature radius of the object side surface of the first lens, R42 is the image side surface of the fourth lens The curvature radius of the surface is as follows: d36 is the distance from the object side surface of the second lens to the image side surface of the third lens on the optical axis, d19 is the distance from the object side surface of the first lens to the image side surface of the fourth lens on the optical axis, G12 is the air distance between the first lens and the second lens, G23 is the air distance between the second lens and the third lens, G34 is the air distance between the third lens and the fourth lens, Vd1 is the Abbe coefficient of the first lens, Vd2 is the Abbe coefficient of the second lens, and Vd4 is the Abbe coefficient of the fourth lens.

2. The imaging lens according to claim 1, wherein: The first lens includes a concave surface facing the image side, and the fourth lens includes a concave surface facing the image side.

3. The imaging lens according to claim 2, wherein: The second lens includes a convex surface facing the object side. The third lens is a biconvex lens and further includes another convex surface facing the object side.

4. The imaging lens according to claim 2, wherein: The fourth lens is a meniscus lens and further includes a convex surface facing the object side.

5. The imaging lens according to claim 2, wherein: The second lens is a biconvex lens and includes a convex surface facing the object side and another convex surface facing the image side.

6. The imaging lens according to claim 5, wherein: The third lens is a biconvex lens and further includes another convex surface facing the object side.

7. The imaging lens according to claim 1, wherein: The imaging lens meets the following conditions: Vd1 <Vd2; Vd4 <Vd2; Wherein Vd1 is the Abbe coefficient of the first lens, Vd2 is the Abbe coefficient of the second lens, and Vd4 is the Abbe coefficient of the fourth lens.

8. The imaging lens according to claim 1, wherein: The imaging lens meets the following conditions: Vd1+Vd4 <Vd2; Wherein Vd1 is the Abbe coefficient of the first lens, Vd2 is the Abbe coefficient of the second lens, and Vd4 is the Abbe coefficient of the fourth lens.

9. The imaging lens according to any one of claims 1 to 8, wherein: It further includes an aperture disposed between the second lens and the third lens, wherein the first lens is a biconcave lens and further includes another concave surface facing the object side; wherein the imaging lens satisfies the following condition: 1≤Vd2 / (Vd1+Vd4)≤2; Wherein Vd1 is the Abbe coefficient of the first lens, Vd2 is the Abbe coefficient of the second lens, and Vd4 is the Abbe coefficient of the fourth lens.

10. The imaging lens according to any one of claims 1 to 8, wherein: It further includes an aperture disposed between the second lens and the third lens, wherein the first lens is a meniscus lens and further includes a convex surface facing the object side; wherein the imaging lens satisfies the following condition: 1≤Vd2 / (Vd1+Vd4)≤2; Wherein Vd1 is the Abbe coefficient of the first lens, Vd2 is the Abbe coefficient of the second lens, and Vd4 is the Abbe coefficient of the fourth lens.

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