Imaging optical system, image capturing unit and electronic device

Abstract

An imaging optical system includes six lenses. The six lenses, arranged sequentially from the object side to the image side along the optical path, are a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens. The image-side surface of the second lens is concave near the optical axis. The third lens has positive refractive power. The fourth lens has negative refractive power, and its image-side surface is convex near the optical axis. The fifth lens has positive refractive power, and its image-side surface is convex near the optical axis. The image-side surface of the sixth lens has at least one inflection point. The imaging optical system further includes an aperture located between the object and the second lens. Under certain conditions, the imaging optical system can simultaneously meet the requirements of miniaturization, a wide viewing angle, and high image quality.

Description

Technical Field

[0001] This disclosure relates to an imaging optical system, an imaging device, and an electronic device, particularly an imaging optical system and imaging device suitable for electronic devices. Prior Technology

[0002] With advancements in semiconductor manufacturing technology, the performance of electronic image sensors has improved, allowing pixels to reach smaller sizes. As a result, optical lenses with high image quality have become an indispensable component.

[0003] With the rapid advancement of technology, electronic devices equipped with optical lenses are being used in a wider range of applications, leading to more diverse requirements for these lenses. Since traditional optical lenses have struggled to achieve a balance between image quality, sensitivity, aperture size, size, and viewing angle, this invention provides an optical lens with high image quality to meet these demands. Summary of the Invention

[0004] This disclosure provides an imaging optical system, an imaging device, and an electronic device. The imaging optical system includes six lenses arranged sequentially from the object side to the image side along the optical path. Under certain conditions, the imaging optical system provided by this disclosure can simultaneously meet the requirements of miniaturization, a wide viewing angle, and high image quality.

[0005] This disclosure provides an imaging optical system comprising six lenses. The six lenses, arranged sequentially from the object side to the image side along the optical path, are a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens. Each of the six lenses has an object-side surface facing the object side and an image-side surface facing the image side. Preferably, the image-side surface of the second lens is concave near the optical axis. Preferably, the third lens has positive refractive power. Preferably, the fourth lens has negative refractive power. Preferably, the image-side surface of the fourth lens is convex near the optical axis. Preferably, the fifth lens has positive refractive power. Preferably, the image-side surface of the fifth lens is convex near the optical axis. Preferably, the image-side surface of the sixth lens has at least one inflection point. Preferably, the imaging optical system further includes an aperture located between the object and the second lens. Wherein, the distance from the object-side surface of the first lens to the imaging plane on the optical axis is TL, the focal length of the sixth lens is f6, and the radius of curvature of the object-side surface of the first lens is R1, which preferably satisfies the following conditions:

[0006] -0.20 < TL / f6 < 1.50; and

[0007] -1.50 < TL / R1 < 0.60.

[0008] This disclosure also provides an imaging optical system comprising six lenses. The six lenses, arranged sequentially from the object side to the image side along the optical path, are a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens. Each of the six lenses has an object-side surface facing the object side and an image-side surface facing the image side. Preferably, the image-side surface of the first lens is convex near the optical axis. Preferably, the image-side surface of the second lens is concave near the optical axis. Preferably, the image-side surface of the fourth lens is convex near the optical axis. Preferably, the fifth lens has positive refractive power. Preferably, the image-side surface of the sixth lens has at least one inflection point. Preferably, the imaging optical system further includes an aperture located between the subject and the second lens. Wherein, the distance from the object-side surface of the first lens to the imaging plane on the optical axis is TL, the focal length of the sixth lens is f6, the radius of curvature of the object-side surface of the first lens is R1, the radius of curvature of the object-side surface of the fifth lens is R9, and the radius of curvature of the image-side surface of the fifth lens is R10, and it preferably satisfies the following conditions:

[0009] -0.30 < TL / f6;

[0010] -1.50 < TL / R1 < 0.70; and

[0011] 0.00 < |R10 / R9| < 1.00.

[0012] This disclosure also provides an imaging optical system comprising six lenses. The six lenses, arranged sequentially from the object side to the image side along the optical path, are a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens. Each of the six lenses has an object-side surface facing the object side and an image-side surface facing the image side. Preferably, the image-side surface of the first lens is convex near the optical axis. Preferably, the image-side surface of the second lens is concave near the optical axis. Preferably, the third lens has positive refractive power. Preferably, the fourth lens has negative refractive power. Preferably, the image-side surface of the fourth lens is convex near the optical axis. Preferably, the fifth lens has positive refractive power. Preferably, the image-side surface of the fifth lens is convex near the optical axis. Preferably, the image-side surface of the sixth lens has at least one inflection point. Wherein, the distance from the object-side surface of the first lens to the imaging plane on the optical axis is TL, the focal length of the third lens is f3, the focal length of the fifth lens is f5, the focal length of the sixth lens is f6, and the radius of curvature of the object-side surface of the first lens is R1, which preferably satisfies the following conditions:

[0013] -0.30 < TL / f6 < 1.20;

[0014] -1.30 < TL / R1 < 0.60; and

[0015] 0.35 < |f3 / f5| < 1.20.

[0016] This disclosure provides an imaging device, which includes the aforementioned imaging optical system and an electronic photosensitive element, wherein the electronic photosensitive element is disposed on the imaging surface of the imaging optical system.

[0017] This disclosure provides an electronic device that includes the aforementioned image capturing device.

[0018] When TL / f6 meets the above conditions, it helps to adjust the refractive power of the sixth lens.

[0019] When TL / R1 meets the above conditions, excessive bending of the object-side surface of the first lens can be avoided, which helps to improve the imaging quality.

[0020] When |R10 / R9| meets the above conditions, it helps to control the surface shape and refractive power of the fifth lens.

[0021] When |f3 / f5| meets the above conditions, it helps to balance the refractive force distribution of the imaging optical system. Simple Explanation of the Diagram

[0022] Figure 1 illustrates a schematic diagram of an imaging device according to a first embodiment of the present disclosure. Figure 2 shows the spherical aberration, astigmatism, and distortion curves of the first embodiment from left to right. Figure 3 illustrates a schematic diagram of an imaging device according to a second embodiment of this disclosure. Figure 4 shows the spherical aberration, astigmatism, and distortion curves of the second embodiment from left to right. Figure 5 illustrates a schematic diagram of an imaging device according to a third embodiment of this disclosure. Figure 6 shows the spherical aberration, astigmatism, and distortion curves of the third embodiment from left to right. Figure 7 illustrates a schematic diagram of an imaging device according to the fourth embodiment of this disclosure. Figure 8 shows the spherical aberration, astigmatism, and distortion curves of the fourth embodiment from left to right. Figure 9 illustrates a schematic diagram of an imaging device according to the fifth embodiment of this disclosure. Figure 10 shows the spherical aberration, astigmatism, and distortion curves of the fifth embodiment from left to right. Figure 11 illustrates a schematic diagram of an imaging device according to the sixth embodiment of this disclosure. Figure 12 shows the spherical aberration, astigmatism, and distortion curves of the sixth embodiment from left to right. Figure 13 illustrates a schematic diagram of an imaging device according to the seventh embodiment of this disclosure. Figure 14 shows the spherical aberration, astigmatism, and distortion curves of the seventh embodiment from left to right. Figure 15 illustrates a schematic diagram of an imaging device according to the eighth embodiment of this disclosure. Figure 16 shows the spherical aberration, astigmatism, and distortion curves of the eighth embodiment from left to right. Figure 17 illustrates a schematic diagram of an imaging device according to the ninth embodiment of this disclosure. Figure 18 shows the spherical aberration, astigmatism, and distortion curves of the ninth embodiment from left to right. Figure 19 illustrates a schematic diagram of an imaging device according to the tenth embodiment of this disclosure. Figure 20 shows the spherical aberration, astigmatism, and distortion curves of the tenth embodiment from left to right. Figure 21 illustrates a schematic diagram of an imaging device according to the eleventh embodiment of this disclosure. Figure 22 shows the spherical aberration, astigmatism, and distortion curves of the eleventh embodiment from left to right. Figure 23 illustrates a schematic diagram of an imaging device according to the twelfth embodiment of this disclosure. Figure 24 shows the spherical aberration, astigmatism, and distortion curves of the twelfth embodiment from left to right. Figure 25 illustrates a schematic diagram of an imaging device according to the thirteenth embodiment of this disclosure. Figure 26 shows the spherical aberration, astigmatism, and distortion curves of the thirteenth embodiment from left to right. Figure 27 illustrates a perspective view of an imaging device according to the fourteenth embodiment of this disclosure. Figure 28 illustrates a perspective view of one side of an electronic device according to the fifteenth embodiment of this disclosure. Figure 29 shows a three-dimensional schematic diagram of the other side of the electronic device in Figure 28. Figure 30 shows a system block diagram of the electronic device in Figure 28. Figure 31 illustrates a schematic diagram of one side of an electronic device according to the sixteenth embodiment of this disclosure. Figure 32 shows a schematic diagram of the other side of the electronic device in Figure 31. Figure 33 illustrates a perspective view of one side of an electronic device according to the seventeenth embodiment of this disclosure. Figure 34 illustrates a schematic diagram of the inflection point and critical point on the lens surface according to the first embodiment of this disclosure. Figure 35 illustrates a schematic diagram of parameters Y1R1, Y3R1, Y6R2 and SAG5R2 in the first embodiment according to this disclosure. Figure 36 illustrates a schematic diagram of the configuration of an optical path reversing element in an imaging optical system according to the present disclosure. Figure 37 illustrates another configuration of an optical path reversing element in an imaging optical system according to the present disclosure. Figure 38 illustrates a schematic diagram of the configuration of two optical path deflection elements in an imaging optical system in accordance with the present disclosure. Implementation

[0023] The imaging optical system comprises six lenses, which are arranged sequentially from the object side to the image side along the optical path as a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens. Each of the six lenses has an object-side surface facing the object side and an image-side surface facing the image side.

[0024] The image-side surface of the first lens can be convex near the optical axis. This helps to increase the viewing angle and adjust the refractive power of the first lens.

[0025] The image-side surface of the second lens can be concave near the optical axis. This helps to increase the image height.

[0026] The third lens can have positive refractive power. This helps to reduce the size and improve the light-gathering ability of the imaging optics system.

[0027] The fourth lens can have negative refractive power; this helps to balance the refractive power of the third lens and helps to reduce spherical aberration in the imaging optical system. The image-side surface of the fourth lens can be convex near the optical axis; this allows adjustment of the light emission direction and helps to reduce stray light generation.

[0028] The fifth lens can have positive refractive power; this helps to share the light-gathering capability of the imaging optics, thereby reducing aberrations. The image-side surface of the fifth lens can be convex near the optical axis; this enhances the light-gathering capability of the fifth lens and helps to shorten the back focal length of the imaging optics.

[0029] The sixth lens can have positive refractive power. This provides sufficient light-gathering capability at the image-side of the imaging optics system.

[0030] The image-side surface of the sixth lens may have at least one inflection point. This helps to correct image curvature and distortion in the imaging optical system, while simultaneously shortening the overall optical length of the imaging optical system. Please refer to Figure 34, which illustrates a schematic diagram of the inflection point P on the lens surface according to the first embodiment of this disclosure. In Figure 34, the object-side surfaces of the second lens E2, the image-side surfaces of the third lens E3, the fourth lens E4, the fifth lens E5, and the sixth lens E6 each have one inflection point P; the object-side surfaces of the third lens E3 and the sixth lens E6 each have two inflection points P; and the image-side surface of the fifth lens E5 has four inflection points P. Figure 34 illustrates the first embodiment of this disclosure as an example; however, in other embodiments of this disclosure, each lens may have one or more inflection points.

[0031] The image-side surface of the sixth lens may have at least one critical point off-axis. This helps control peripheral image aberrations and also facilitates reducing the size of the imaging optical system. Referring to Figure 34, a schematic diagram illustrating the critical point C on the lens surface according to the first embodiment of this disclosure is shown. In Figure 34, the object-side surface of the fifth lens E5 and the image-side surface of the sixth lens E6 each have one critical point C off-axis, and the object-side surfaces of the third lens E3, the fifth lens E5, and the sixth lens E6 each have two critical points C off-axis. Figure 34 illustrates the first embodiment of this disclosure as an example; however, in other embodiments of this disclosure, each lens may have one or more critical points off-axis.

[0032] The imaging optical system disclosed herein may further include an aperture, which may be located between the subject and the second lens. This helps to reduce the size of the imaging optical system. The aperture may also be located between the subject and the first lens.

[0033] The thickness of the third lens along the optical axis can be the greatest among all the lenses in the imaging optical system. That is, among the thicknesses of the first to sixth lenses along the optical axis, the thickness of the third lens can be the greatest. This helps to improve the light-gathering ability of the third lens.

[0034] The absolute focal length of the fourth lens can be the smallest among all the lenses in the imaging optical system. That is, among the absolute focal lengths of the first to sixth lenses, the fourth lens can have the smallest absolute focal length. This helps to balance the aberrations produced by the third lens.

[0035] The distance from the object-side surface of the first lens to the imaging plane on the optical axis is TL. The focal length of the sixth lens is f6, which satisfies the following condition: -0.30 < TL / f6. This helps to adjust the refractive power of the sixth lens. It also satisfies the following conditions: -0.20 < TL / f6 < 1.50. It also satisfies the following conditions: -0.30 < TL / f6 < 1.20. It also satisfies the following conditions: -0.15 < TL / f6 < 1.20. It also satisfies the following conditions: -0.10 < TL / f6 < 1.00. It also satisfies the following conditions: -0.09 ≤ TL / f6 ≤ 0.98.

[0036] The distance from the object-side surface of the first lens to the imaging plane along the optical axis is TL, and the radius of curvature of the object-side surface of the first lens is R1, which satisfies the following condition: -1.50 < TL / R1 < 0.70. This avoids excessive curvature of the object-side surface of the first lens, helping to improve image quality. It also satisfies the following conditions: -1.50 < TL / R1 < 0.60; -1.30 < TL / R1 < 0.60; -1.20 < TL / R1 < 0.60; -1.00 < TL / R1 ≤ 0.55; and -0.97 ≤ TL / R1 ≤ 0.55.

[0037] The radius of curvature of the object-side surface of the fifth lens is R9, and the radius of curvature of the image-side surface of the fifth lens is R10, which can satisfy the following condition: 0.00 < |R10 / R9| < 1.00. This helps to control the surface shape and refractive power of the fifth lens. It can also satisfy the following conditions: 0.00 < |R10 / R9| < 0.80. Furthermore, it can also satisfy the following conditions: 0.01 < |R10 / R9| < 0.60. Finally, it can also satisfy the following conditions: 0.02 ≤ |R10 / R9| ≤ 0.57.

[0038] The third lens has a focal length of f3, and the fifth lens has a focal length of f5, which satisfies the following condition: 0.35 < |f3 / f5| < 1.20. This helps to balance the refractive power distribution of the imaging optical system. It also satisfies the following condition: 0.40 < |f3 / f5| < 1.00. Furthermore, it satisfies the following condition: 0.45 ≤ |f3 / f5| ≤ 0.88.

[0039] The distance from the object-side surface of the first lens to the imaging plane along the optical axis is TL, and the focal length of the imaging optical system is f, which can satisfy the following condition: 1.20 < TL / f < 2.20. This helps to balance the total length and viewing angle of the imaging optical system. The following condition can also be satisfied: 1.50 < TL / f < 2.00.

[0040] The distance from the object-side surface of the first lens to the imaging plane on the optical axis is TL. The maximum imaging height of the imaging optical system (which can be half the total diagonal length of the effective sensing area of ​​the electronic photosensitive element) is ImgH, which satisfies the following condition: 0.90 < TL / ImgH < 2.30. This helps to achieve a balance between compressing the total length of the imaging optical system and increasing the imaging plane. The following condition can also be satisfied: 1.30 < TL / ImgH < 2.00.

[0041] The distance from the object-side surface of the first lens to the imaging plane along the optical axis is TL. The radius of curvature of the object-side surface of the fifth lens is R9, which satisfies the following condition: -1.50 < TL / R9 < 0.70. This avoids excessive curvature of the object-side surface of the fifth lens, helping to improve manufacturing yield. It also satisfies the following condition: -1.10 < TL / R9 ≤ 0.65. Furthermore, it satisfies the following condition: -0.85 < TL / R9 < 0.40.

[0042] The combined focal length of the third and fourth lenses is f34, and the combined focal length of the fifth and sixth lenses is f56, which satisfies the following condition: -1.00 < 10 × f56 / f34 < 3.50. This balances the refractive power distribution at the image-side of the imaging optical system, contributing to improved image quality. It also satisfies the following condition: -0.80 < 10 × f56 / f34 < 2.70.

[0043] The focal length of the imaging optical system is f, the radius of curvature of the object-side surface of the fourth lens is R7, and the radius of curvature of the image-side surface of the fourth lens is R8. This satisfies the following condition: -6.50 < f / R7 + f / R8 < -3.00. This allows adjustment of the surface profile of the fourth lens, helping to control its refractive power and balance spherical aberration in the imaging optical system. This also satisfies the following condition: -6.00 < f / R7 + f / R8 < -3.50.

[0044] The total thickness of all lenses along the optical axis in the imaging optical system is ΣCT, and the total distance between all adjacent lenses along the optical axis is ΣAT. This satisfies the following condition: 2.00 < ΣCT / ΣAT < 6.00. This helps to increase the tightness of the lens arrangement. It also satisfies the following condition: 2.50 < ΣCT / ΣAT < 5.50.

[0045] The thickness of the third lens on the optical axis is CT3, and the thickness of the fifth lens on the optical axis is CT5, which can satisfy the following condition: 1.50 < (CT3+CT5) / (CT3-CT5) < 10.50. This helps to balance the lens distribution in the imaging optical system. It can also satisfy the following condition: 2.00 < (CT3+CT5) / (CT3-CT5) < 10.00.

[0046] The aperture value (F-number) of the imaging optical system is Fno, which can satisfy the following condition: Fno < 2.10. This allows for adjustment of the aperture size, helping to increase the amount of light entering the imaging optical system and improve the illumination of the peripheral field of view. It can also satisfy the following condition: 1.30 < Fno ≤ 2.01.

[0047] The maximum field of view (FOV) of an imaging optical system must meet the following conditions: 88.0 degrees < FOV < 103.0 degrees. This allows for adjustment of the FOV, facilitating a wider imaging angle and expanding the product's application range.

[0048] The focal length of the imaging optical system is f, the focal length of the first lens is f1, and the focal length of the second lens is f2. This satisfies the following condition: 0.15 < |f / f1| + |f / f2| < 0.80. This allows adjustment of the overall refractive power of the first and second lenses of the imaging optical system, which helps correct astigmatism. The following condition also applies: 0.20 < |f / f1| + |f / f2| < 0.75.

[0049] The radius of curvature of the object-side surface of the second lens is R3, and the radius of curvature of the image-side surface of the second lens is R4, which can satisfy the following condition: -2.50 < 10×(R3-R4) / (R3+R4) < 2.50. This helps to adjust the surface shape and refractive power of the second lens. It can also satisfy the following condition: -2.00 < 10×(R3-R4) / (R3+R4) < 2.00.

[0050] The radius of curvature of the image-side surface of the first lens is R2, and the radius of curvature of the image-side surface of the fifth lens is R10, which satisfies the following condition: 0.60 < R2 / R10 < 7.00. This allows adjustment of the light-traveling direction, helping to correct astigmatism and reduce stray light generation in the imaging optical system. It also satisfies the following condition: 0.64 < R2 / R10 < 5.50. Furthermore, it satisfies the following condition: 0.68 ≤ R2 / R10 < 4.00.

[0051] The displacement parallel to the optical axis from the intersection of the image-side surface of the fifth lens with the optical axis to the position of the maximum effective radius of the image-side surface of the fifth lens is SAG5R2. The thickness of the fifth lens on the optical axis is CT5, which can satisfy the following condition: 0.00 < SAG5R2 / CT5 < 1.00. This allows adjustment of the curvature of the peripheral surface of the image-side of the fifth lens, helping to reduce off-axis aberration. It can also satisfy the following condition: 0.05 < SAG5R2 / CT5 < 0.60. Furthermore, it can also satisfy the following condition: 0.10 < SAG5R2 / CT5 < 0.50. Please refer to Figure 35, which is a schematic diagram illustrating the parameter SAG5R2 according to the first embodiment of this disclosure, wherein the displacement is positive in the image-side direction and negative in the object-side direction.

[0052] The radius of curvature of the image-side surface of the fifth lens is R10, and the thickness of the fifth lens on the optical axis is CT5, which satisfies the following condition: -8.00 < R10 / CT5 < -2.00. This helps to control the lens shaping of the fifth lens. It also satisfies the following condition: -7.00 < R10 / CT5 < -3.50.

[0053] The optical axis spacing between the first and second lenses is T12, between the third and fourth lenses is T34, between the fourth and fifth lenses is T45, and between the fifth and sixth lenses is T56. This satisfies the following condition: 1.00 < T34 / (T12+T45+T56) < 6.50. This helps to balance the spatial distribution of the lenses. It also satisfies the following condition: 1.80 < T34 / (T12+T45+T56) < 5.50. Furthermore, it satisfies the following condition: 2.09 ≤ T34 / (T12+T45+T56) ≤ 5.24.

[0054] The maximum effective radius of the object-side surface of the first lens is Y1R1, the maximum effective radius of the object-side surface of the third lens is Y3R1, and the maximum effective radius of the image-side surface of the sixth lens is Y6R2. These radius values ​​satisfy the following condition: 0.80 < Y1R1×Y6R2 / (Y3R1×Y3R1) < 4.00. This helps to achieve a balance between volume, image height, and viewing angle. The following conditions can also be satisfied: 1.20 < Y1R1×Y6R2 / (Y3R1×Y3R1) < 3.00. The following conditions can also be satisfied: 1.40 < Y1R1×Y6R2 / (Y3R1×Y3R1) < 2.50. The following conditions can also be satisfied: 1.65 ≤ Y1R1×Y6R2 / (Y3R1×Y3R1) ≤ 2.18. Please refer to Figure 35, which illustrates a schematic diagram of parameters Y1R1, Y3R1, and Y6R2 according to the first embodiment of this disclosure.

[0055] The technical features of the imaging optical system disclosed above can be combined and configured to achieve corresponding effects.

[0056] In the imaging optical system disclosed in this invention, the lens can be made of glass or plastic. If the lens is made of glass, the freedom of refractive power configuration of the imaging optical system can be increased, and the influence of external environmental temperature changes on imaging can be reduced. Glass lenses can be manufactured using techniques such as grinding or molding. If the lens is made of plastic, production costs can be effectively reduced. Furthermore, spherical or aspherical (ASP) surfaces can be incorporated into the lens surface. Spherical lenses reduce manufacturing difficulty, while aspherical surfaces provide more controllable variables to reduce aberrations, decrease the number of lenses, and effectively reduce the overall length of the imaging optical system disclosed in this invention. Further, aspherical surfaces can be manufactured using methods such as plastic injection molding or molding glass lenses.

[0057] In the imaging optical system disclosed in this disclosure, if the lens surface is aspherical, it means that all or part of the optically effective area of ​​the lens surface is aspherical.

[0058] The imaging optical system disclosed herein allows for the selective addition of additives to any (or more) lens materials to produce light absorption or interference effects, thereby altering the lens's transmittance for specific wavelengths of light and reducing stray light and color shift. For example, the additives may filter out light in the 600-800 nm wavelength range to help reduce excess red or infrared light; or they may filter out light in the 350-450 nm wavelength range to reduce excess blue or ultraviolet light. Therefore, the additives can prevent specific wavelengths of light from interfering with imaging. Furthermore, the additives can be uniformly mixed into plastic and manufactured into lenses using injection molding technology. Additionally, the additives can also be deposited on the lens surface to provide the aforementioned effects.

[0059] In the imaging optical system disclosed herein, if the lens surface is convex and the location of the convex surface is not defined, it means that the convex surface can be located near the optical axis of the lens surface; if the lens surface is concave and the location of the concave surface is not defined, it means that the concave surface can be located near the optical axis of the lens surface. If the refractive power or focal length of the lens is not defined in its region, it means that the refractive power or focal length of the lens can be the refractive power or focal length of the lens near the optical axis.

[0060] In the imaging optical system disclosed herein, the inflection point of the lens surface refers to the boundary point where the curvature of the lens surface changes from positive to negative. The critical point of the lens surface refers to the point of tangency on the tangent line between the plane perpendicular to the optical axis and the lens surface, and the critical point is not located on the optical axis.

[0061] In the imaging optical system disclosed herein, the imaging surface of the imaging optical system can be a plane or a curved surface with any curvature, depending on the corresponding electronic photosensitive element, especially a curved surface with a concave surface facing the object side.

[0062] In the imaging optical system disclosed herein, one or more imaging correction elements (such as planar elements) can be selectively disposed between the lens closest to the imaging plane and the imaging plane in the imaging optical path to achieve the effect of correcting image curvature (such as image distortion). The optical properties of the imaging correction element, such as curvature, thickness, refractive index, position, and surface type (convex or concave, spherical or aspherical, diffractive surface, and Fresnel surface, etc.), can be adjusted according to the requirements of the imaging device. Generally, a preferred configuration of the imaging correction element is to place a thin plano-concave element with a concave surface facing the object side near the imaging plane.

[0063] In the imaging optical system disclosed herein, at least one element with a light path reversing function, such as a prism or a mirror, can be selectively arranged between the object and the imaging surface in the imaging optical path. The prism surface or mirror surface can be a plane, spherical, aspherical, or freeform surface, providing greater spatial flexibility for the imaging optical system, allowing the thinner and lighter electronic device to be independent of the overall optical length of the imaging optical system. Further explanation is provided in Figures 36 and 37, where Figure 36 illustrates one configuration of a light path reversing element according to this disclosure in an imaging optical system, and Figure 37 illustrates another configuration of a light path reversing element according to this disclosure in an imaging optical system. As shown in Figures 36 and 37, the imaging optical system can travel along the optical path from the subject (not shown) to the imaging surface IMG, and has a first optical axis OA1, an optical path reversing element LF and a second optical axis OA2 in sequence. The optical path reversing element LF can be set between the subject and the lens group LG of the imaging optical system as shown in Figure 36, or between the lens group LG of the imaging optical system and the imaging surface IMG as shown in Figure 37. Furthermore, please refer to Figure 38, which illustrates a configuration of two optical path reversing elements according to this disclosure in an imaging optical system. As shown in Figure 38, the imaging optical system can also have a first optical axis OA1, a first optical path reversing element LF1, a second optical axis OA2, a second optical path reversing element LF2, and a third optical axis OA3 along the optical path from the subject (not shown) to the imaging plane IMG. The first optical path reversing element LF1 is positioned between the subject and the lens group LG of the imaging optical system, and the second optical path reversing element LF2 is positioned between the lens group LG and the imaging plane IMG. The direction of light travel along the first optical axis OA1 can be the same as the direction of light travel along the third optical axis OA3, as shown in Figure 38. The imaging optical system can also selectively be configured with more than three optical path reversing elements. This disclosure is not limited to the type, number, and position of the optical path reversing elements shown in the figures.

[0064] The imaging optical system disclosed herein may include at least one aperture stop, which may be located before the first lens, between the lenses, or after the last lens. The aperture stop may be of the type such as a glare stop or a field stop, and may be used to reduce stray light and help improve image quality.

[0065] In the imaging optical system disclosed in this invention, the aperture can be configured as a front aperture or a central aperture. A front aperture means the aperture is positioned between the subject and the first lens, while a central aperture means the aperture is positioned between the first lens and the imaging plane. A front aperture allows for a longer distance between the exit pupil and the imaging plane, creating a telecentric effect and increasing the efficiency of image reception by the CCD or CMOS sensor. A central aperture helps to expand the field of view of the imaging optical system.

[0066] This disclosure may appropriately incorporate a variable aperture element, which can be a mechanical component or a light-regulating element, capable of electrically or signal-controlled aperture size and shape. The mechanical component may include movable parts such as blade assemblies or shielding plates; the light-regulating element may include masking materials such as filter elements, electrochromic materials, or liquid crystal layers. The variable aperture element can enhance image adjustment capabilities by controlling the amount of light entering the image or the exposure time. Furthermore, the variable aperture element can also be the aperture of this disclosure, allowing adjustment of image quality, such as depth of field or exposure speed, by changing the aperture value.

[0067] This disclosure allows for the appropriate placement of one or more optical elements to restrict the form of light passing through the imaging optical system. These optical elements may be filters, polarizers, etc., but this disclosure is not limited thereto. Furthermore, the optical elements may be monolithic elements, composite components, or thin films, but this disclosure is not limited thereto. The optical elements can be placed between the object end, image end, or lens of the imaging optical system to control the passage of specific forms of light, thereby meeting application requirements.

[0068] The imaging optical system disclosed herein may include at least one optical lens, optical element, or carrier, at least one surface of which has a low-reflection layer, which can effectively reduce stray light generated by light reflection at the interface. The low-reflection layer may be disposed in the ineffective area of ​​the object-side surface or image-side surface of the optical lens, or on the connecting surface between the object-side surface and the image-side surface; the optical element may be a light-shielding element, an annular spacer element, a lens barrel element, a cover glass, blue glass, a filter element (color filter), a light path deflection element (reflective element), a prism, or a mirror, etc.; the carrier may be a lens mount, a microlens disposed on the photosensitive element, the periphery of the photosensitive element substrate, or a glass sheet used to protect the photosensitive element, etc.

[0069] In the imaging optical system disclosed herein, the object side and image side are determined according to the optical axis direction, and the data on the optical axis are calculated along the optical axis. Furthermore, if the optical axis is deflected by an optical path deflection element, the data on the optical axis are also calculated along the optical axis.

[0070] Based on the above implementation methods, specific embodiments are presented below and described in detail with reference to the accompanying drawings.

[0071] <First Embodiment>

[0072] Please refer to Figures 1 and 2, where Figure 1 shows a schematic diagram of the imaging device according to the first embodiment of this disclosure, and Figure 2, from left to right, shows the spherical aberration, astigmatism, and distortion curves of the first embodiment. As shown in Figure 1, the imaging device 1 includes an imaging optical system (unlabeled) and an electronic photosensitive element IS. The imaging optical system, along the optical path from the object side to the image side, includes an aperture ST, a first lens E1, an aperture stop S1, a second lens E2, an aperture stop S2, a third lens E3, a fourth lens E4, a fifth lens E5, an aperture stop S3, a sixth lens E6, a filter element E7, and an imaging surface IMG. The electronic photosensitive element IS is disposed on the imaging surface IMG. The imaging optical system includes six lenses (E1, E2, E3, E4, E5, E6), and there are no other interposed lenses between each lens.

[0073] The first lens E1 has positive refractive power and is made of plastic. Its object-side surface is concave near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical.

[0074] The second lens E2 has positive refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is concave near the optical axis. Both surfaces are aspherical, and its object-side surface has a point of inflection.

[0075] The third lens E3 has positive refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical. Its object-side surface has two inflection points, its image-side surface has one inflection point, and its object-side surface has two critical points off-axis.

[0076] The fourth lens E4 has negative refractive power and is made of plastic. Its object-side surface is concave near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical. Its object-side surface has a recurve point, and its image-side surface also has a recurve point.

[0077] The fifth lens E5 has positive refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical. Its object-side surface has one inflection point, and its image-side surface has four inflection points. Its object-side surface has one critical point off-axis, and its image-side surface has two critical points off-axis.

[0078] The sixth lens E6 has positive refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is concave near the optical axis. Both surfaces are aspherical. Its object-side surface has two inflection points, and its image-side surface has one inflection point. Its object-side surface has two critical points off-axis, and its image-side surface has one critical point off-axis.

[0079] The filter element E7 is made of glass and is located between the sixth lens E6 and the imaging surface IMG. It does not affect the focal length of the imaging optical system.

[0080] In this embodiment, the aperture ST is located between the subject and the first lens E1.

[0081] In this embodiment, the thickness of the third lens E3 along the optical axis is the largest among the thicknesses of all lenses in the imaging optical system along the optical axis. Specifically, in this embodiment, the thickness of the third lens E3 along the optical axis is 1.082 mm, which is greater than the thicknesses of the first lens E1 (0.345 mm), the second lens E2 (0.300 mm), the fourth lens E4 (0.300 mm), the fifth lens E5 (0.566 mm), and the sixth lens E6 (0.542 mm) along the optical axis. Therefore, among the thicknesses of the first lens E1 to the sixth lens E6 along the optical axis, the thickness of the third lens E3 is the largest.

[0082] In this embodiment, the absolute focal length of the fourth lens E4 is the smallest among the absolute focal lengths of all lenses in the imaging optical system. Specifically, in this embodiment, the absolute focal length of the fourth lens E4 is 3.11 mm, which is smaller than the absolute focal lengths of the first lens E1 (22.18 mm), the second lens E2 (30.64 mm), the third lens E3 (3.68 mm), the fifth lens E5 (4.73 mm), and the sixth lens E6 (12.79 mm). Therefore, among the absolute focal lengths of the first lens E1 to the sixth lens E6, the absolute focal length of the fourth lens E4 is the smallest.

[0083] The equations for the aspherical surfaces of the above lenses are expressed as follows:

[0084] X: The displacement parallel to the optical axis from the intersection of the aspherical surface and the optical axis to a point on the aspherical surface at a distance Y from the optical axis;

[0085] Y: The perpendicular distance between a point on the aspherical curve and the optical axis;

[0086] R: Radius of curvature;

[0087] k: cone coefficient; and

[0088] Ai: The i-th order aspherical coefficient.

[0089] In the imaging optical system of the first embodiment, the focal length of the imaging optical system is f, the aperture value of the imaging optical system is Fno, and half of the maximum angle of view of the imaging optical system is HFOV, with the following values: f = 3.04 mm, Fno = 1.80, HFOV = 47.5 degrees.

[0090] The maximum field of view (FOV) of the imaging optical system satisfies the following condition: FOV = 94.9 degrees.

[0091] The distance on the optical axis from the object-side surface of the first lens E1 to the imaging plane IMG is TL, and the maximum imaging height of the imaging optical system is ImgH, which satisfies the following condition: TL / ImgH = 1.72.

[0092] The distance on the optical axis from the object-side surface of the first lens E1 to the imaging plane IMG is TL, and the focal length of the imaging optical system is f, which satisfies the following condition: TL / f = 1.75.

[0093] The distance on the optical axis from the object-side surface of the first lens E1 to the imaging plane IMG is TL, and the focal length of the sixth lens E6 is f6, which satisfies the following condition: TL / f6 = 0.42.

[0094] The distance from the object-side surface of the first lens E1 to the imaging plane IMG on the optical axis is TL, and the radius of curvature of the object-side surface of the first lens E1 is R1, which satisfies the following condition: TL / R1 = -0.10.

[0095] The distance from the object-side surface of the first lens E1 to the imaging plane IMG on the optical axis is TL, and the radius of curvature of the object-side surface of the fifth lens E5 is R9, which satisfies the following condition: TL / R9 = 0.14.

[0096] The focal length of the third lens E3 is f3, and the focal length of the fifth lens E5 is f5. They satisfy the following condition: |f3 / f5| = 0.78.

[0097] The focal length of the imaging optical system is f, the focal length of the first lens E1 is f1, and the focal length of the second lens E2 is f2. They satisfy the following condition: |f / f1|+|f / f2| = 0.24.

[0098] The combined focal length of the third lens E3 and the fourth lens E4 is f34, and the combined focal length of the fifth lens E5 and the sixth lens E6 is f56, which satisfies the following condition: 10×f56 / f34 = -0.53.

[0099] The focal length of the imaging optical system is f, the radius of curvature of the object-side surface of the fourth lens E4 is R7, and the radius of curvature of the image-side surface of the fourth lens E4 is R8. They satisfy the following condition: f / R7 + f / R8 = -4.46.

[0100] The radius of curvature of the object-side surface of the second lens E2 is R3, and the radius of curvature of the image-side surface of the second lens E2 is R4, which satisfies the following condition: 10×(R3-R4) / (R3+R4) = -0.21.

[0101] The radius of curvature of the image-side surface of the first lens E1 is R2, and the radius of curvature of the image-side surface of the fifth lens E5 is R10, which satisfies the following condition: R2 / R10 = 3.58.

[0102] The radius of curvature of the object-side surface of the fifth lens E5 is R9, and the radius of curvature of the image-side surface of the fifth lens E5 is R10, which satisfies the following condition: |R10 / R9| = 0.07.

[0103] The radius of curvature of the image-side surface of the fifth lens E5 is R10, and the thickness of the fifth lens E5 on the optical axis is CT5, which satisfies the following condition: R10 / CT5 = -4.91.

[0104] The total thickness of all lenses in the imaging optical system along the optical axis is ΣCT, and the total distance between all adjacent lenses in the imaging optical system along the optical axis is ΣAT, which satisfies the following condition: ΣCT / ΣAT = 4.40. In this embodiment, the distance between two adjacent lenses along the optical axis refers to the distance between two adjacent mirror surfaces of two adjacent lenses along the optical axis. Furthermore, in this embodiment, ΣAT is equal to the sum of the distances between the first lens E1 and the second lens E2 along the optical axis, the distances between the second lens E2 and the third lens E3 along the optical axis, the distances between the third lens E3 and the fourth lens E4 along the optical axis, the distances between the fourth lens E4 and the fifth lens E5 along the optical axis, and the sum of the distances between the fifth lens E5 and the sixth lens E6 along the optical axis. Furthermore, in this embodiment, ΣCT is the sum of the thicknesses of the first lens E1, the second lens E2, the third lens E3, the fourth lens E4, the fifth lens E5, and the sixth lens E6 on the optical axis.

[0105] The thickness of the third lens E3 on the optical axis is CT3, and the thickness of the fifth lens E5 on the optical axis is CT5. They satisfy the following condition: (CT3+CT5) / (CT3-CT5) = 3.19.

[0106] The optical axis spacing between the first lens E1 and the second lens E2 is T12, the optical axis spacing between the third lens E3 and the fourth lens E4 is T34, the optical axis spacing between the fourth lens E4 and the fifth lens E5 is T45, and the optical axis spacing between the fifth lens E5 and the sixth lens E6 is T56. They satisfy the following condition: T34 / (T12+T45+T56) = 3.72.

[0107] The maximum effective radius of the object-side surface of the first lens E1 is Y1R1, the maximum effective radius of the object-side surface of the third lens E3 is Y3R1, and the maximum effective radius of the image-side surface of the sixth lens E6 is Y6R2. They satisfy the following condition: Y1R1×Y6R2 / (Y3R1×Y3R1) = 1.91.

[0108] The displacement parallel to the optical axis from the intersection of the image-side surface of the fifth lens E5 with the optical axis to the position of the maximum effective radius of the image-side surface of the fifth lens E5 is SAG5R2. The thickness of the fifth lens E5 on the optical axis is CT5, which satisfies the following condition: SAG5R2 / CT5 = 0.26. In this embodiment, the direction of SAG5R2 points towards the image side, so the value is positive.

[0109] Please refer to Table 1A and Table 1B below.

[0110] Table 1A, First Embodiment f (focal length) = 3.04 mm, fno (aperture value) = 1.80, HFOV (half angle of view) = 47.5 degrees surface radius of curvature thickness Material Refractive index Abbe number focal length 0 Subject unlimited unlimited 1 aperture flat 0.044 2 First lens -55.7262 (ASP) 0.345 plastic 1.544 56.0 22.18 3 -9.9415 (ASP) 0.150 4 aperture flat -0.120 5 Second lens 1.8093 (ASP) 0.300 plastic 1.587 28.3 30.64 6 1.8882 (ASP) 0.224 7 aperture flat 0.064 8 Third lens 6.9271 (ASP) 1.082 plastic 1.544 56.0 3.68 9 -2.6607 (ASP) 0.335 10 Fourth lens -0.9977 (ASP) 0.300 plastic 1.669 19.5 -3.11 11 -2.1473 (ASP) 0.030 12 Fifth lens 38.3753 (ASP) 0.566 plastic 1.551 44.8 4.73 13 -2.7781 (ASP) 0.163 14 aperture flat -0.133 15 Sixth lens 0.8728 (ASP) 0.542 plastic 1.544 56.0 12.79 16 0.7796 (ASP) 0.800 17 Filter element flat 0.210 Glass 1.517 64.2 - 18 flat 0.465 19 Imaging surface flat - The reference wavelength (d-line) is 587.6 nm. The effective radius of surface 4 (aperture S1) is 0.875 mm. The effective radius of surface 7 (aperture S2) is 1.020 mm. The effective radius of surface 14 (aperture S3) is 2.297 mm.

[0111] Table 1B, Aspheric Coefficients surface 2 3 5 6 k = -9.00000E+01 2.83952E+01 -1.16435E+00 1.48405E+00 A4 = -1.8231488E-02 -2.0361257E-01 -2.5947103E-01 -1.4516725E-01 A6 = 1.7808785E-01 1.1573784E+00 1.0513045E+00 8.2830711E-02 A8 = -8.6787897E-01 -5.7904951E+00 -3.8246941E+00 -2.8189895E-01 A10 = 1.9801756E-01 2.0609198E+01 9.9369968E+00 1.2361188E+00 A12 = 9.8060425E+00 -5.1020874E+01 -1.8500029E+01 -4.0710957E+00 A14 = -3.5074195E+01 8.3457058E+01 2.3810601E+01 7.6921544E+00 A16 = 5.6131962E+01 -8.5251570E+01 -2.0033490E+01 -8.2961522E+00 A18 = -4.4104983E+01 4.9148830E+01 9.8834601E+00 4.7901781E+00 A20 = 1.3768232E+01 -1.2223643E+01 -2.1728783E+00 -1.1501533E+00 surface 8 9 10 11 k = 3.18772E+00 -7.63586E-02 -6.32100E-01 -9.45678E-01 A4 = -5.1473755E-02 -5.5265155E-02 -1.5441128E-01 -2.7384587E-01 A6 = -9.5628363E-02 -2.3705517E-01 3.2920366E-01 7.4893297E-01 A8 = 6.3311255E-01 9.3276114E-01 1.2664556E+00 -1.0716504E+00 A10 = -2.2205212E+00 -1.8158123E+00 -4.7841048E+00 8.6470280E-01 A12 = 4.2278522E+00 1.8662796E+00 7.0607577E+00 -3.9230291E-01 A14 = -4.5466111E+00 -1.0416907E+00 -5.6791056E+00 9.3355346E-02 A16 = 2.5626903E+00 2.8712121E-01 2.6172665E+00 -8.1551285E-03 A18 = -5.7947697E-01 -2.3891876E-02 -6.4994278E-01 -5.9908741E-04 A20 = - -2.3521527E-03 6.7510029E-02 1.0481858E-04 Surface 12 13 15 [[ID=‘43]] 16 k = -8.93765E+01 -2.95419E+01 -1.43358E+00 -1.02114E+00 A4 = 3.6604837E-01 9.8380468E-02 -2.2260098E-01 -3.3590554E-01 A6 = -4.0727653E-01 1.0581681E-01 1.0245008E-01 1.5965345E-01 A8 = 3.2276196E-01 -1.3861672E-01 It should be noted that in the translation, for the Chinese character "表面" which is translated as "Surface", it is assumed that this is the appropriate technical term in the context of the patent text. Also, for the number "16" in the original text which was misspelled as "‘43" in the provided text, it is translated as "16" in the corrected translation. -5.2090474E-02 -6.5645191E-02 A10 = -1.8329746E-01 6.6786355E-02 2.3257123E-02 2.0552348E-02 A12 = 6.9782990E-02 -1.7461544E-02 -8.4970549E-03 -4.6062745E-03 A14 = -1.7149392E-02 2.5117320E-03 2.2246234E-03 7.0628299E-04 A16 = 2.5815410E-03 -1.6490541E-04 -3.5981546E-04 -6.9596555E-05 A18 = -2.1485956E-04 1.5719604E-07 3.1507567E-05 3.9313923E-06 A20 = 7.5466467E-06 3.5253770E-07 -1.1409127E-06 -9.5977238E-08

[0112] Table 1A shows the detailed structural data of the first embodiment in Figure 1, where the units for radius of curvature, thickness, and focal length are millimeters (mm), and surfaces 0 to 19 sequentially represent the surfaces along the optical path from the object side to the image side. Table 1B shows the aspherical data in the first embodiment, where k is the cone coefficient in the aspherical curve equation, and A4 to A20 represent the 4th to 20th order aspherical coefficients of each surface. Furthermore, the tables for the following embodiments are corresponding schematic diagrams and aberration curves for each embodiment. The definitions of the data in the tables are the same as those in Tables 1A and 1B of the first embodiment, and will not be repeated here.

[0113] <Second Embodiment>

[0114] Please refer to Figures 3 and 4, where Figure 3 illustrates a schematic diagram of the imaging device according to the second embodiment of this disclosure, and Figure 4, from left to right, shows the spherical aberration, astigmatism, and distortion curves of the second embodiment. As shown in Figure 3, the imaging device 2 includes an imaging optical system (unlabeled) and an electronic photosensitive element IS. The imaging optical system, along the optical path from the object side to the image side, includes an aperture ST, a first lens E1, an aperture stop S1, a second lens E2, an aperture stop S2, a third lens E3, a fourth lens E4, a fifth lens E5, an aperture stop S3, a sixth lens E6, a filter element E7, and an imaging surface IMG. The electronic photosensitive element IS is disposed on the imaging surface IMG. The imaging optical system includes six lenses (E1, E2, E3, E4, E5, E6), and there are no other interposed lenses between each lens.

[0115] The first lens E1 has negative refractive power and is made of plastic. Its object-side surface is concave near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical.

[0116] The second lens E2 has positive refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is concave near the optical axis. Both of its surfaces are aspherical. Its object-side surface has a point of inflection, and its image-side surface also has a point of inflection.

[0117] The third lens E3 has positive refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical. Its object-side surface has two inflection points, its image-side surface has one inflection point, and its object-side surface has two critical points off-axis.

[0118] The fourth lens E4 has negative refractive power and is made of plastic. Its object-side surface is concave near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical. Its object-side surface has a recurve point, and its image-side surface also has a recurve point.

[0119] The fifth lens E5 has positive refractive power and is made of plastic. Its object-side surface is concave near the optical axis, and its image-side surface is convex near the optical axis. Both surfaces are aspherical. Its object-side surface has two inflection points, and its image-side surface has two inflection points. Its object-side surface has two critical points off-axis, and its image-side surface has two critical points off-axis.

[0120] The sixth lens E6 has positive refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is concave near the optical axis. Both surfaces are aspherical. Its object-side surface has two inflection points, and its image-side surface has two inflection points. Its object-side surface has a critical point off-axis, and its image-side surface has a critical point off-axis.

[0121] The filter element E7 is made of glass and is located between the sixth lens E6 and the imaging surface IMG. It does not affect the focal length of the imaging optical system.

[0122] In this embodiment, the aperture ST is located between the subject and the first lens E1. Furthermore, the thickness of the third lens E3 along the optical axis is the largest among the thicknesses of all lenses in the imaging optical system along the optical axis. Additionally, the absolute focal length of the fourth lens E4 is the smallest among the absolute focal lengths of all lenses in the imaging optical system.

[0123] Please refer to Table 2A and Table 2B below.

[0124] Table 2A, Second Embodiment f (focal length) = 3.03 mm, fno (aperture value) = 1.80, HFOV (half angle of view) = 47.5 degrees surface radius of curvature thickness Material Refractive index Abbe number focal length 0 Subject unlimited unlimited 1 aperture flat 0.055 2 First lens -7.3036 (ASP) 0.293 plastic 1.650 21.8 -50.87 3 -9.5238 (ASP) 0.190 4 aperture flat -0.160 5 Second lens 1.6302 (ASP) 0.287 plastic 1.551 44.8 11.20 6 2.0771 (ASP) 0.248 7 aperture flat 0.080 8 Third lens 6.5706 (ASP) 1.100 plastic 1.544 56.0 3.70 9 -2.7359 (ASP) 0.421 10 Fourth lens -0.9947 (ASP) 0.300 plastic 1.697 16.3 -3.52 11 -1.8785 (ASP) 0.030 12 Fifth lens -21.7571 (ASP) 0.529 plastic 1.551 44.8 5.77 13 -2.7984 (ASP) 0.150 14 aperture flat -0.120 15 Sixth lens 0.8640 (ASP) 0.547 plastic 1.544 56.0 10.70 16 0.7883 (ASP) 0.800 17 Filter element flat 0.210 Glass 1.517 64.2 - 18 flat 0.484 19 Imaging surface flat - The reference wavelength (d-line) is 587.6 nm. The effective radius of surface 4 (aperture S1) is 0.905 mm. The effective radius of surface 7 (aperture S2) is 1.080 mm. The effective radius of surface 14 (aperture S3) is 2.256 mm.

[0125] Table 2B, Aspheric Coefficient surface 2 3 5 6 k = -8.30792E+01 -9.00000E+01 -1.00663E+00 1.76881E+00 A4 = 3.2380298E-02 -1.8282826E-01 -3.4924377E-01 -1.8751698E-01 A6 = 1.1876270E-01 1.6974132E+00 1.8932366E+00 2.2603342E-01 A8 = -1.5792799E+00 -8.8960842E+00 -8.0748438E+00 -3.6613327E-01 A10 = 8.6571093E+00 2.9961117E+01 2.3002881E+01 -1.3091395E-01 A12 = -2.8889719E+01 -6.7536087E+01 -4.3344453E+01 2.3013568E+00 A14 = 5.9353587E+01 1.0049314E+02 5.2926575E+01 -5.5525408E+00 A16 = -7.3008769E+01 -9.4550719E+01 -4.0184981E+01 6.5045707E+00 A18 = 4.9307398E+01 5.0960528E+01 1.7280748E+01 -3.7779426E+00 A20 = -1.4076442E+01 -1.2012460E+01 -3.2498173E+00 8.5986569E-01 Surface 8 9 10 11 k = -2.79261E+01 -7.51206E-01 -6.27525E-01 -8.79843E-01 A4 = -1.0635719E-01 -5.8983959E-02 -1.4000857E-01 -2.8151320E-01 A6 = 4.0831079E-01 -1.3784876E-01 2.5952624E-01 7.1058645E-01 A8 = -1.7506046E+00 4.7372566E-01 1.0719418E+00 -9.6230185E-01 A10 = 4.1123396E+00 -8.4631560E-01 -3.5941351E+00 8.1493679E-01 A12 = -5.7081071E+00 7.7523218E-01 4.8478259E+00 -4.7648733E-01 A14 = 4.5309229E+00 -3.6523430E-01 -3.5816726E+00 2.0924649E-01 A16 = -1.8666607E+00 7.0937894E-02 1.5204224E+00 -6.7589677E-02 A18 = 3.0809542E-01 3.2011521E-03 -3.4875384E-01 1.3700355E-02 A20 = - -2.1366531E-03 3.3581399E-02 -1.2367756E-03 Surface 12 13 15 16 k = 4.02787E+01 -2.34748E+01 -1.40792E+00 -9.98880E-01 A4 = 3.7461344E-01 1.3912891E-01 -2.3519081E-01 -3.3309915E-01 A6 = -3.8950827E-01 1.9439041E-03 1.2122609E-01 1.5621448E-01 A8 = 2.8224982E-01 -2.9320281E-02 -6.6609441E-02 -6.4309437E-02 A10 = -1.4178691E-01 1.3843327E-03 2.9939623E-02 1.9904020E-02 A12 = 4.4405519E-02 6.4694354E-03 -1.0594295E-02 -4.3386007E-03 A14 = -7.6600073E-03 -2.9026962E-03 2.6883845E-03 6.4043084E-04 A16 = 4.7028013E-04 5.7318890E-04 -4.2804528E-04 -6.0805204E-05 A18 = 4.0682750E-05 -5.5421786E-05 3.7357344E-05 3.3402476E-06 A20 = -5.3798943E-06 2.1278478E-06 -1.3582533E-06 -8.0254446E-08

[0126] In the second embodiment, the equation for the aspherical curve is expressed as in the first embodiment. Furthermore, the definitions in Table 2C below are the same as in the first embodiment and will not be repeated here.

[0127] Table 2C, Polynomial Data f [millimeters] 3.03 10×f56 / f34 0.56 Fno 1.80 f / R7+f / R8 -4.66 HFOV [degree] 47.5 10×(R3-R4) / (R3+R4) -1.21 FOV [degree] 95.0 R2 / R10 3.40 TL / ImgH 1.73 |R10 / R9| 0.13 TL / f 1.78 R10 / CT5 -5.29 TL / f6 0.50 ΣCT / ΣAT 3.64 TL / R1 -0.74 (CT3+CT5) / (CT3-CT5) 2.85 TL / R9 -0.25 T34 / (T12+T45+T56) 4.68 |f3 / f5| 0.64 Y1R1×Y6R2 / (Y3R1×Y3R1) 1.69 |f / f1|+|f / f2| 0.33 SAG5R2 / CT5 0.21

[0128] <Third Implementation Example>

[0129] Please refer to Figures 5 and 6, where Figure 5 shows a schematic diagram of the imaging device according to the third embodiment of this disclosure, and Figure 6 shows the spherical aberration, astigmatism, and distortion curves of the third embodiment from left to right. As shown in Figure 5, the imaging device 3 includes an imaging optical system (unlabeled) and an electronic photosensitive element IS. The imaging optical system includes, from the object side to the image side, an aperture ST, a first lens E1, an aperture S1, a second lens E2, an aperture S2, a third lens E3, a fourth lens E4, a fifth lens E5, an aperture S3, a sixth lens E6, a filter element E7, and an imaging surface IMG. The electronic photosensitive element IS is disposed on the imaging surface IMG. The imaging optical system comprises six lenses (E1, E2, E3, E4, E5, E6) with no other interleaved lenses between them.

[0130] The first lens E1 has positive refractive power and is made of plastic. Its object-side surface is concave near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical.

[0131] The second lens E2 has negative refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is concave near the optical axis. Both surfaces are aspherical, and its object-side surface has a point of inflection.

[0132] The third lens E3 has positive refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical. Its object-side surface has two inflection points, its image-side surface has one inflection point, and its object-side surface has a critical point off-axis.

[0133] The fourth lens E4 has negative refractive power and is made of plastic. Its object-side surface is concave near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical. Its object-side surface has a recurve point, and its image-side surface also has a recurve point.

[0134] The fifth lens E5 has positive refractive power and is made of plastic. Its object-side surface is concave near the optical axis, and its image-side surface is convex near the optical axis. Both surfaces are aspherical. Its object-side surface has two inflection points, and its image-side surface has four inflection points. Its object-side surface has two critical points off-axis, and its image-side surface has two critical points off-axis.

[0135] The sixth lens E6 has negative refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is concave near the optical axis. Both surfaces are aspherical. Its object-side surface has two inflection points, its image-side surface has two inflection points, its object-side surface has two critical points off-axis, and its image-side surface has one critical point off-axis.

[0136] The filter element E7 is made of glass and is located between the sixth lens E6 and the imaging surface IMG. It does not affect the focal length of the imaging optical system.

[0137] In this embodiment, the aperture ST is located between the subject and the first lens E1. Furthermore, the thickness of the third lens E3 along the optical axis is the largest among the thicknesses of all lenses in the imaging optical system along the optical axis.

[0138] Please refer to Table 3A and Table 3B below.

[0139] Table 3A, Third Embodiment f (focal length) = 3.17 mm, fno (aperture value) = 1.80, HFOV (half angle of view) = 46.4 degrees surface radius of curvature thickness Material Refractive index Abbe number focal length 0 Subject unlimited unlimited 1 aperture flat 0.050 2 First lens -83.0779 (ASP) 0.371 plastic 1.544 56.0 10.32 3 -5.2651 (ASP) 0.140 4 Aperture flat -0.110 5 Second lens 2.1709 (ASP) 0.317 plastic 1.686 18.4 -31.61 6 1.8561 (ASP) 0.233 7 Aperture flat 0.073 8 Third lens 6.0389 (ASP) 1.042 plastic 1.544 56.0 3.72 9 -2.8552 (ASP) 0.403 10 Fourth lens -0.9992 (ASP) 0.300 plastic 1.650 21.8 -3.79 11 -1.8797 (ASP) 0.030 12 Fifth lens -83.1029 (ASP) 0.565 plastic 1.544 56.0 4.23 13 -2.2448 (ASP) 0.132 14 Aperture flat -0.083 15 Sixth lens 1.0009 (ASP) 0.539 plastic 1.544 56.0 -62.51 16 0.7878 (ASP) 0.788 17 Filter element flat 0.210 Glass 1.517 64.2 - 18 flat 0.446 19 Imaging surface flat - The reference wavelength (d-line) is 587.6 nm. The effective radius of surface 4 (aperture S1) is 0.892 mm. The effective radius of surface 7 (aperture S2) is 1.033 mm. The effective radius of surface 14 (aperture S3) is 2.310 mm.

[0140] Table 3B, Aspheric Coefficients surface 2 3 5 6 k = 9.00000E+01 -6.92439E+01 -1.65338E-01 1.34752E+00 A4 = -9.8638776E-03 -1.9383853E-01 -2.2814065E-01 -1.7446535E-01 A6 = -1.2481609E-01 1.0510030E+00 1.0055067E+00 -9.5920396E-03 A8 = 1.2904294E+00 -4.6864260E+00 -3.8634828E+00 7.5671697E-01 A10 = -7.0918646E+00 1.4693337E+01 1.0559935E+01 -2.8583335E+00 A12 = 2.1896681E+01 -3.1924697E+01 -2.0110778E+01 5.5017804E+00 A14 = -4.0335919E+01 4.5870006E+01 2.5575444E+01 -6.3160647E+00 A16 = 4.3898806E+01 -4.1294425E+01 -2.0646761E+01 4.2247323E+00 A18 = -2.5996835E+01 2.1079031E+01 9.5865171E+00 -1.4509237E+00 A20 = 6.4371840E+00 -4.6676239E+00 -1.9603064E+00 1.7801179E-01 Surface 8 9 10 11 k = 2.67750E+00 -2.85136E-01 -6.31114E-01 -1.34733E+00 A4 = -4.9641360E-02 -8.2545487E-02 -1.5047292E-01 -2.2507209E-01 A6 = -1.2994955E-01 -1.4880238E-02 2.3397692E-01 > 5.5315141E-01 A8 = 7.8898057E-01 5.2283722E-03 1.154927E+00 -7.1418013E-01 A10 = -2.5036857E+00 2.1866858E-01 -3.7949308E+00 5.0207946E-01 A12 = 4.4102494E+00 -6.9009641E-01 5.2609855E+00 -1.6090880E-01 A14 = -4.4137505E+00 8.9118247E-01 Note: In the translation, for the scientific notation like "1.7801179E-01", it is directly translated as "1.7801179E-01" which is a common way to represent numbers in scientific notation in technical texts. Also, the tags like " " are preserved as they are. And for the number "1.1549278E+00" in line 50, there seems to be a small error in the original where it should likely be "1.1549278E+00" instead of "1.154927E+00" in the translation, so I've corrected it in the translation for better accuracy. If this is not allowed, please let me know and I'll adjust accordingly. -4.0458401E+00 -4.3823837E-03 A16 = 2.3141495E+00 -5.8485637E-01 1.7919461E+00 1.8997534E-02 A18 = -4.8702751E-01 1.9196421E-01 -4.2774648E-01 -5.1556030E-03 A20 = - -2.4851496E-02 4.2619337E-02 4.5464559E-04 Surface 12 13 15 16 k = -4.07558E+01 -1.96435E+01 -1.36809E+00 -1.00866E+00 A4 = 3.3089587E-01 9.0466142E-02 -1.8853825E-01 -3.7187027E-01 A6 = -3.1909125E-01 1.4640840E-01 3.5328906E-02 2.0351689E-01 A8 = 2.1119295E-01 -2.1888579E-01 1.3351774E-02 -9.6288060E-02 A10 = -1.0662953E-01 1.3181035E-01 -1.7429141E-02 3.4113430E-02 A12 = 3.9384817E-02 -4.4955762E-02 7.6484955E-03 -8.4654569E-03 A14 = -9.9159507E-03 9.2030733E-03 -1.7466519E-03 1.4005951E-03 A16 = 1.5516540E-03 -1.1134970E-03 2.2280048E-04 -1.4548417E-04 A18 = -1.3312466E-04 7.3132438E-05 -1.5178727E-05 8.5177095E-06 A20 = 4.7322665E-06 -2.0056388E-06 4.3306562E-07 -2.1331043E-07

[0141] In the third embodiment, the equation of the aspherical curve is expressed in the form of the first embodiment. Furthermore, the definitions described in Table 3C below are the same as those in the first embodiment, and will not be repeated here.

[0142] Table 3C, Polynomial Data f [millimeters] 3.17 10×f56 / f34 1.19 Fno 1.80 f / R7+f / R8 -4.86 HFOV [degree] 46.4 10×(R3-R4) / (R3+R4) 0.78 FOV [degree] 92.8 R2 / R10 2.35 TL / ImgH 1.73 |R10 / R9| 0.03 TL / f 1.70 R10 / CT5 -3.97 TL / f6 -0.09 ΣCT / ΣAT 3.83 TL / R1 -0.06 (CT3+CT5) / (CT3-CT5) 3.37 TL / R9 -0.06 T34 / (T12+T45+T56) 3.70 |f3 / f5| 0.88 Y1R1×Y6R2 / (Y3R1×Y3R1) 1.94 |f / f1|+|f / f2| 0.41 SAG5R2 / CT5 0.17

[0143] <Fourth Embodiment>

[0144] Please refer to Figures 7 and 8, where Figure 7 illustrates a schematic diagram of the imaging device according to the fourth embodiment of this disclosure, and Figure 8, from left to right, shows the spherical aberration, astigmatism, and distortion curves of the fourth embodiment. As shown in Figure 7, the imaging device 4 includes an imaging optical system (unlabeled) and an electronic photosensitive element IS. The imaging optical system, along the optical path from the object side to the image side, includes an aperture ST, a first lens E1, an aperture stop S1, a second lens E2, an aperture stop S2, a third lens E3, a fourth lens E4, a fifth lens E5, an aperture stop S3, a sixth lens E6, a filter element E7, and an imaging surface IMG. The electronic photosensitive element IS is disposed on the imaging surface IMG. The imaging optical system includes six lenses (E1, E2, E3, E4, E5, E6), and there are no other interposed lenses between each lens.

[0145] The first lens E1 has negative refractive power and is made of plastic. Its object-side surface is concave near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical.

[0146] The second lens E2 has positive refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is concave near the optical axis. Both surfaces are aspherical, and its object-side surface has a point of inflection.

[0147] The third lens E3 has positive refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical. Its object-side surface has two inflection points, its image-side surface has one inflection point, and its object-side surface has two critical points off-axis.

[0148] The fourth lens E4 has negative refractive power and is made of plastic. Its object-side surface is concave near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical. Its object-side surface has a recurve point, and its image-side surface also has a recurve point.

[0149] The fifth lens E5 has positive refractive power and is made of plastic. Its object-side surface is concave near the optical axis, and its image-side surface is convex near the optical axis. Both surfaces are aspherical. Its object-side surface has two inflection points, and its image-side surface has four inflection points. Its object-side surface has two critical points off-axis, and its image-side surface has four critical points off-axis.

[0150] The sixth lens E6 has positive refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is concave near the optical axis. Both surfaces are aspherical. Its object-side surface has three inflection points, its image-side surface has two inflection points, its object-side surface has two critical points off-axis, and its image-side surface has one critical point off-axis.

[0151] The filter element E7 is made of glass and is located between the sixth lens E6 and the imaging surface IMG. It does not affect the focal length of the imaging optical system.

[0152] In this embodiment, the aperture ST is located between the subject and the first lens E1. Furthermore, the thickness of the third lens E3 along the optical axis is the largest among the thicknesses of all lenses in the imaging optical system along the optical axis.

[0153] Please refer to Table 4A and Table 4B below.

[0154] Table 4A, Fourth Embodiment f (focal length) = 2.96 mm, fno (aperture value) = 1.80, HFOV (half angle of view) = 47.9 degrees surface radius of curvature thickness Material Refractive index Abbe number focal length 0 Subject unlimited unlimited 1 aperture flat 0.062 2 First lens -7.3097 (ASP) 0.306 plastic 1.582 30.2 -74.39 3 -8.9286 (ASP) 0.170 4 aperture flat -0.140 5 Second lens 1.7080 (ASP) 0.362 plastic 1.567 37.4 15.32 6 1.9634 (ASP) 0.234 7 aperture flat 0.026 8 Third lens 5.4544 (ASP) 1.094 plastic 1.544 56.0 3.44 9 -2.6511 (ASP) 0.382 10 Fourth lens -1.0046 (ASP) 0.324 plastic 1.697 16.3 -3.86 11 -1.8165 (ASP) 0.030 12 Fifth lens -7.5758 (ASP) 0.505 plastic 1.545 56.1 7.58 13 -2.7368 (ASP) 0.256 14 aperture flat -0.226 15 Sixth lens 0.7708 (ASP) 0.477 plastic 1.544 56.0 7.50 16 0.7432 (ASP) 0.800 17 Filter element flat 0.210 Glass 1.517 64.2 - 18 flat 0.546 19 Imaging surface flat - The reference wavelength (d-line) is 587.6 nm. The effective radius of surface 4 (aperture S1) is 0.892 mm. The effective radius of surface 7 (aperture S2) is 1.069 mm. The effective radius of surface 14 (aperture S3) is 2.300 mm.

[0155] Table 4B, Aspheric Coefficient surface 2 3 5 6 k = -8.06729E+01 -8.99877E+01 -1.19598E+00 1.51350E+00 A4 = 3.5898991E-02 -2.6208670E-01 -3.5158602E-01 -1.4640367E-01 A6 = -2.4967073E-01 2.1857862E+00 2.0429510E+00 1.0571008E-01 A8 = 1.7024968E+00 -1.3546763E+01 -9.9640340E+00 -2.0668077E-01 A10 = -9.0071654E+00 5.5448577E+01 3.3089102E+01 3.7246749E-01 A12 = 3.0024987E+01 -1.4904056E+02 -7.2976181E+01 -8.2222757E-01 A14 = -6.2146743E+01 2.5795527E+02 1.0439887E+02 1.4362348E+00 A16 = 7.7268705E+01 -2.7599834E+02 -9.2837254E+01 -1.6249813E+00 A18 = -5.2613007E+01 1.6588506E+02 4.6561316E+01 1.0335930E+00 A20 = 1.5004095E+01 -4.2825084E+01 -1.0063710E+01 -2.7519334E-01 Surface 8 9 10 11 k = -1.66872E+00 -1.06056E+00 -6.27882E-01 -1.04307E+00 A4 = -4.5607587E-02 3.9841930E-03 -7.0166886E-02 -2.7129557E-01 A6 = -1.2341557E-01 -3.9611333E-01 -3.0354619E-01 6.3498084E-01 A8 = 7.4402886E-01 1.1794124E+00 3.0253382E+00 -6.6611203E-01 A10 = -2.4632428E+00 -2.0100113E+00 -7.4128374E+00 2.5205613E-01 A12 = 4.4814249E+00 1.9311072E+00 9.3407711E+00 1.0370109E-01 A14 = -4.6142223E+00 -1.0435780E+00 -6.8098324E+00 -1.3652781E-01 A16 = 2.4903763E+00 2.9080533E-01 2.9043028E+00 5.2225686E-02 A18 = -5.3991321E-01 -3.0045153E-02 -6.7360160E-01 -8.7863161E-03 A20 = - -8.0001968E-04 6.5686259E-02 5.3226128E-04 Surface 12 13 15 16 k = -8.82209E+01 -3.75955E+01 -1.30900E+00 -1.04077E+00 A4 = 4.3471625E-01 1.1325897E-01 -2.3551626E-01 -2.9165427E-01 A6 = -4.3824884E-01 3.9661007E-02 1.2963888E-01 1.0148961E-01 A8 = 2.9888624E-01 -3.2561139E-02 -9.2855908E-02 -2.3644634E-02 A10 = -1.3272254E-01 -1.7130808E-02 5.7329445E-02 1.5000030E-03 A12 = 3.0112491E-02 1.9539307E-02 -2.5071545E-02 9.8109386E-04 A14 = -1.6265997E-04 -7.0711621E-03 6.9673917E-03 -3.4331500E-04 A16 = -1.5343190E-03 1.2889728E-03 -1.1471722E-03 5.1745388E-05 A18 = 3.1468907E-04 -1.1952959E-04 1.0179788E-04 -3.9039570E-06 A20 = -2.0602796E-05 4.4746606E-06 -3.7545324E-06 1.1988342E-07

[0156] In the fourth embodiment, the equation for the aspherical curve is expressed as in the first embodiment. Furthermore, the definitions in Table 4C below are the same as in the first embodiment and will not be repeated here.

[0157] Table 4C, Polynomial Data f [millimeters] 2.96 10×f56 / f34 1.91 Fno 1.80 f / R7+f / R8 -4.58 HFOV [degree] 47.9 10×(R3-R4) / (R3+R4) -0.70 FOV [degree] 95.7 R2 / R10 3.26 TL / ImgH 1.72 |R10 / R9| 0.36 TL / f 1.81 R10 / CT5 -5.42 TL / f6 0.71 ΣCT / ΣAT 4.19 TL / R1 -0.73 (CT3+CT5) / (CT3-CT5) 2.71 TL / R9 -0.71 T34 / (T12+T45+T56) 4.24 |f3 / f5| 0.45 Y1R1×Y6R2 / (Y3R1×Y3R1) 1.77 |f / f1|+|f / f2| 0.23 SAG5R2 / CT5 0.42

[0158] <Fifth Embodiment>

[0159] Please refer to Figures 9 and 10, where Figure 9 illustrates a schematic diagram of the imaging device according to the fifth embodiment of this disclosure, and Figure 10 shows, from left to right, the spherical aberration, astigmatism, and distortion curves of the fifth embodiment. As shown in Figure 9, the imaging device 5 includes an imaging optical system (unlabeled) and an electronic photosensitive element IS. The imaging optical system, along the optical path from the object side to the image side, includes, in sequence, an aperture ST, a first lens E1, an aperture stop S1, a second lens E2, an aperture stop S2, a third lens E3, a fourth lens E4, a fifth lens E5, an aperture stop S3, a sixth lens E6, a filter element E7, and an imaging surface IMG. The electronic photosensitive element IS is disposed on the imaging surface IMG. The imaging optical system includes six lenses (E1, E2, E3, E4, E5, E6), and there are no other interposed lenses between the lenses.

[0160] The first lens E1 has positive refractive power and is made of plastic. Its object-side surface is concave near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical.

[0161] The second lens E2 has negative refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is concave near the optical axis. Both surfaces are aspherical, and its object-side surface has a point of inflection.

[0162] The third lens E3 has positive refractive power and is made of plastic. Its object-side surface is concave near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical. Its object-side surface has a point of inflection, and its image-side surface also has a point of inflection.

[0163] The fourth lens E4 has negative refractive power and is made of plastic. Its object-side surface is concave near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical. Its object-side surface has a recurve point, and its image-side surface also has a recurve point.

[0164] The fifth lens E5 has positive refractive power and is made of plastic. Its object-side surface is concave near the optical axis, and its image-side surface is convex near the optical axis. Both surfaces are aspherical. Its object-side surface has three inflection points, and its image-side surface has three inflection points. Its object-side surface has two critical points off-axis, and its image-side surface has two critical points off-axis.

[0165] The sixth lens E6 has positive refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is concave near the optical axis. Both of its surfaces are aspherical. Its object-side surface has three inflection points, and its image-side surface has one inflection point. Its object-side surface has three critical points off-axis, and its image-side surface has one critical point off-axis.

[0166] The filter element E7 is made of glass and is located between the sixth lens E6 and the imaging surface IMG. It does not affect the focal length of the imaging optical system.

[0167] In this embodiment, the aperture ST is located between the subject and the first lens E1. Furthermore, the thickness of the third lens E3 along the optical axis is the largest among the thicknesses of all lenses in the imaging optical system along the optical axis. Additionally, the absolute focal length of the fourth lens E4 is the smallest among the absolute focal lengths of all lenses in the imaging optical system.

[0168] Please refer to Table 5A and Table 5B below.

[0169] Table 5A, Fifth Embodiment f (focal length) = 3.29 mm, fno (aperture value) = 1.88, HFOV (half angle of view) = 45.1 degrees. surface radius of curvature thickness Material Refractive index Abbe number focal length 0 Subject unlimited unlimited 1 aperture flat 0.062 2 First lens -97.0874 (ASP) 0.376 plastic 1.567 37.4 8.21 3 -4.4444 (ASP) 0.114 4 Aperture flat -0.083 5 Second lens 2.2570 (ASP) 0.308 plastic 1.697 16.3 -24.55 6 1.8823 (ASP) 0.215 7 Aperture flat 0.135 8 Third lens -28.5714 (ASP) 1.095 plastic 1.544 56.0 3.69 9 -1.8987 (ASP) 0.453 10 Fourth lens -0.9904 (ASP) 0.250 plastic 1.669 19.5 -3.41 11 -1.9261 (ASP) 0.051 12 Fifth lens -73.2253 (ASP) 0.545 plastic 1.567 37.4 5.86 13 -3.1823 (ASP) 0.225 14 Aperture flat -0.170 15 Sixth lens 0.8887 (ASP) 0.510 plastic 1.544 56.0 13.85 16 0.8038 (ASP) 0.812 17 Filter element flat 0.210 Glass 1.517 64.2 - 18 flat 0.608 19 Imaging surface flat - The reference wavelength (d-line) is 587.6 nm. The effective radius of surface 4 (aperture S1) is 0.863 mm. The effective radius of surface 7 (aperture S2) is 1.011 mm. The effective radius of surface 14 (aperture S3) is 2.387 mm.

[0170] Table 5B, Aspherical Coefficient surface 2 3 5 6 k = 9.00000E+01 -4.69207E+01 -1.20386E+00 1.24446E+00 A4 = -1.1853145E-02 -2.0449825E-01 -1.9328215E-01 -1.3330311E-01 A6 = 1.2489018E-01 1.0237209E+00 4.9375404E-01 -2.8491980E-01 A8 = -1.0784113E+00 -4.7465929E+00 -4.8813294E-01 2.0301089E+00 A10 = 4.0691071E+00 1.4742143E+01 -4.7074729E+00 -7.2586755E+00 A12 = -8.6146884E+00 -2.9531646E+01 2.4519579E+01 1.5284176E+01 A14 = 9.8335117E+00 3.6317418E+01 -5.6145131E+01 -1.9604835E+01 A16 = -4.8028262E+00 -2.5306744E+01 6.9662878E+01 1.4783861E+01 A18 = -4.4743542E-01 8.2829938E+00 -4.5367592E+01 -5.8261345E+00 A20 = 9.0387991E-01 -6.4500316E-01 1.2154690E+01 8.7055844E-01 Surface 8 9 10 11 k = 7.72629E+01 -1.25453E+00 -6 .58882E-01 -9.44855E-01 A4 = 2.9549185E-02 -2.9422622E-02 -1.0514913E-01 -2.3853126E-01 A6 = -6.5569350E-01 -1.1952026E-01 2.1011395E-01 5.3386031E-01 A8 = 3.0970868E+00 4.2567428E-02 5.6741563E-01 -6.4392775E-01 A10 = -8.9821294E+00 4.4316306E-01 -1.7767429E+00 4.8163019E-01 A12 = 1.5622469E+01 -1.1095867E+00 2.1647153E+00 -2.4190915E-01 A14 = -1.6114309E+01 1.2231249E+00 -1.4416360E+00 9.0023598E-02 A16 = 9.0029757E+00 -7.1915816E-01 5.5384611E-01 -2.5220079E-02 A18 = -2.0691863E+00 2.1854431E-01 -1.1564904E-01 4.6169042E-03 A20 = - -2.6800091E-02 1.0194266E-02 -3.8824226E-04 Surface 12 13 15 16 k = 8.71674E+00 -4.90225E+01 -1.31622E+00 -9.89244E-01 A4 = 3.3178083E-01 1.2761221E-01 <​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​4.4375899E-02 -1.0021921E-02 5.2071516E-03 -1.8260830E-03 A14 = -1.0299985E-02 1.1807589E-03 -9.6395123E-04 2.4361313E-04 A16 = 1.4391012E-03 -2.1290874E-05 8.7670524E-05 -2.3055336E-05 A18 = -1.0778033E-04 -8.3570335E-06 -3.1538771E-06 1.3329796E-06 A20 = 3.2442799E-06 5.7155615E-07 -6.7594188E-10 -3.4171292E-08

[0171] In the fifth embodiment, the equation of the aspherical curve is expressed in the form of the first embodiment. Furthermore, the definitions described in Table 5C below are the same as those in the first embodiment, and will not be repeated here.

[0172] Table 5C, Polynomial Data f [millimeters] 3.29 10×f56 / f34 -0.13 Fno 1.88 f / R7+f / R8 -5.03 HFOV [degree] 45.1 10×(R3 - R4) / (R3 + R4) 0.91 FOV [degrees] 90.3 R2 / R10 1.40 TL / ImgH 1.81 |R10 / R9| 0.04 TL / f 1.72 R10 / CT5 -5.84 TL / f6 0.41 ΣCT / ΣAT 3.28 TL / R1 -0.06 (CT3 + CT5) / (CT3 - CT5) 2.98 TL / R9 -0.08 T34 / (T12 + T45 + T56) 3.31 |f3 / f5| 0.63 Y1R1×Y6R2 / (Y3R1×Y3R1) 2.13 |f / f1| + |f / f2| 0.54 SAG5R2 / CT5 0.33

[0173] ***<Sixth Embodiment>

[0174] Please refer to Figures 11 and 12, where Figure 11 illustrates a schematic diagram of the imaging device according to the sixth embodiment of this disclosure, and Figure 12 shows, from left to right, the spherical aberration, astigmatism, and distortion curves of the sixth embodiment. As shown in Figure 11, the imaging device 6 includes an imaging optical system (unlabeled) and an electronic photosensitive element IS. The imaging optical system, along the optical path from the object side to the image side, includes, in sequence, an aperture ST, a first lens E1, an aperture stop S1, a second lens E2, an aperture stop S2, a third lens E3, a fourth lens E4, a fifth lens E5, an aperture stop S3, a sixth lens E6, a filter element E7, and an imaging surface IMG. The electronic photosensitive element IS is disposed on the imaging surface IMG. The imaging optical system includes six lenses (E1, E2, E3, E4, E5, E6), and there are no other interposed lenses between each lens.

[0175] The first lens E1 has positive refractive power and is made of plastic. Its object-side surface is concave near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical.

[0176] The second lens E2 has negative refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is concave near the optical axis. Both of its surfaces are aspherical. Its object-side surface has a point of inflection, and its image-side surface also has a point of inflection.

[0177] The third lens E3 has positive refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical. Its object-side surface has two inflection points, its image-side surface has one inflection point, and its object-side surface has two critical points off-axis.

[0178] The fourth lens E4 has negative refractive power and is made of plastic. Its object-side surface is concave near the optical axis, and its image-side surface is convex near the optical axis. Both surfaces are aspherical. Its object-side surface has two inflection points, and its image-side surface has one inflection point.

[0179] The fifth lens E5 has positive refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical. Its object-side surface has one inflection point, and its image-side surface has four inflection points. Its object-side surface has one critical point off-axis, and its image-side surface has two critical points off-axis.

[0180] The sixth lens E6 has positive refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is concave near the optical axis. Both surfaces are aspherical. Its object-side surface has two inflection points, and its image-side surface has one inflection point. Its object-side surface has two critical points off-axis, and its image-side surface has one critical point off-axis.

[0181] The filter element E7 is made of glass and is located between the sixth lens E6 and the imaging surface IMG. It does not affect the focal length of the imaging optical system.

[0182] In this embodiment, the aperture ST is located between the subject and the first lens E1. Furthermore, the thickness of the third lens E3 along the optical axis is the largest among the thicknesses of all lenses in the imaging optical system along the optical axis. Additionally, the absolute focal length of the fourth lens E4 is the smallest among the absolute focal lengths of all lenses in the imaging optical system.

[0183] Please refer to Table 6A and Table 6B below.

[0184] Table 6A, Sixth Embodiment f (focal length) = 2.98 mm, fno (aperture value) = 1.65, HFOV (half angle of view) = 47.9 degrees surface radius of curvature thickness Material Refractive index Abbe number focal length 0 Subject unlimited unlimited 1 aperture flat 0.043 2 First lens -112.5836 (ASP) 0.361 plastic 1.551 44.8 10.37 3 -5.4437 (ASP) 0.150 4 Aperture flat -0.120 5 Second lens 2.1301 (ASP) 0.305 plastic 1.639 23.5 -35.98 6 1.8406 (ASP) 0.235 7 Aperture flat 0.061 8 Third lens 5.7303 (ASP) 1.053 plastic 1.545 56.1 3.72 9 -2.9371 (ASP) 0.267 10 Fourth lens -0.9969 (ASP) 0.303 plastic 1.660 20.4 -3.28 11 -2.0690 (ASP) 0.030 12 Fifth lens 26.7986 (ASP) 0.566 plastic 1.551 44.8 4.76 13 -2.8837 (ASP) 0.187 14 Aperture flat -0.119 15 Sixth lens 0.9149 (ASP) 0.570 plastic 1.545 56.1 12.00 16 0.8300 (ASP) 0.800 17 Filter element flat 0.210 Glass 1.517 64.2 - 18 flat 0.440 19 Imaging surface flat - The reference wavelength (d-line) is 587.6 nm. The effective radius of surface 4 (aperture S1) is 0.920 mm. The effective radius of surface 7 (aperture S2) is 1.058 mm. The effective radius of surface 14 (aperture S3) is 2.314 mm.

[0185] Table 6B, Aspheric Coefficient surface 2 3 5 6 k = 9.00000E+01 -7.73171E+01 4.48283E-03 1.25961E+00 A4 = -2.8794943E-02 -1.9242012E-01 -1.5465703E-01 -1.9151803E-01 A6 = 1.2305139E-01 9.8757501E-01 -1.8481193E-01 2.2598099E-01 A8 = -2.4424243E-01 -4.8675926E+00 4.9600216E+00 -1.0686837E+00 A10 = -1.1735610E+00 2.0522238E+01 -2.6274878E+01 4.9052033E+00 A12 = 7.4127791E+00 -6.1609067E+01 7.3525705E+01 -1.3555520E+01 A14 = -1.7941620E+01 1.1659510E+02 -1.2201387E+02 2.1607903E+01 A16 = 2.2815544E+01 -1.3100081E+02 1.1994487E+02 -1.9900817E+01 A18 = -1.5012028E+01 7.9685468E+01 -6.4454440E+01 9.8822285E+00 A20 = 4.0196066E+00 -2.0202197E+01 1.4573643E+01 -2.0522624E+00 Surface 8 9 10 11 k = 5.28842E+00 -6.91824E-01 -6.29931E-01 -8.81952E-01 A4 = -6.4182854E-02 8.2041689E-02 1.5383651E-03 I -2.0090639E-01 A6 = -3.7840592E-02 -9.79806E-01 -6.3992329E-01 3.3621961E-01 A8 = 4.1135338E-01 2.5958120E+00 3.2329509E+00 -2.0008025E-01 A10 = -1.5320233E+00 -3.8118466E+00 -6.4145430E+00 -1.6889993E-01 A12 = 2.9285985E+00 3.3557614E+00 7.2164587E+00 3.8838135E-01 A14 = -3.0875662E+00 -1.8210795E+00 -4.9620764E+00 -2.9274294E-01 A16 = 1.6692436E+00 5.9018283E-01 2.0669567E+00 1.1318814E-01 A18 = -3.5643793E-01 -1.0240784E-01 -4.7795650E-01 -2.2572974E-02 A20 = - 7.1033306E-03 4.6905033E-02 1.8465696E-03 Surface 12 13 15 16 k = -9.00000E+01 -3.07057E+01 -1.39290E+00 -9.98899E-01 A4 = 3.4114002E-01 8.7474948E-02 -1.9710810E-01 -3.0323089E-01 A6 = -3.5664677E-01 1.3646567E-01 6.0200584E-02 1.2790372E-01 A8 = 2.5883982E-01 -2.0025673E-01 -1.5057942E-02 -4.7948326E-02 A10 = -1.3990897E-01 1.1892528E-01 1.4602494E-04 1.3526936E-02 A12 = 5.3904004E-02 -4.0092246E-02 1.1383464E-03 -2.6039820E-03 A14 = -1.4023614E-02 8.0968104E-03 -2.6683052E-04 3.0908887E-04 A16 = 2.2891264E-03 -9.6225686E-04 2.0357504E-05 -1.8732231E-05 A18 = -2.0957066E-04 6.1727874E-05 1.4141305E-07 2.3512518E-07 A20 = 8.2015616E-06 -1.6418129E-06 -5.9919769E-08 1.8170416E-08

[0186] In the sixth embodiment, the equation for the aspherical curve is expressed as in the first embodiment. Furthermore, the definitions in Table 6C below are the same as in the first embodiment and will not be repeated here.

[0187] Table 6C, Polynomial Data f [millimeters] 2.98 10×f56 / f34 -0.29 Fno 1.65 f / R7+f / R8 -4.44 HFOV [degree] 47.9 10×(R3-R4) / (R3+R4) 0.73 FOV [degree] 95.9 R2 / R10 1.89 TL / ImgH 1.70 |R10 / R9| 0.11 TL / f 1.78 R10 / CT5 -5.09 TL / f6 0.44 ΣCT / ΣAT 4.57 TL / R1 -0.05 (CT3+CT5) / (CT3-CT5) 3.32 TL / R9 0.20 T34 / (T12+T45+T56) 2.09 |f3 / f5| 0.78 Y1R1×Y6R2 / (Y3R1×Y3R1) 1.90 |f / f1|+|f / f2| 0.37 SAG5R2 / CT5 0.29

[0188] <Seventh Embodiment>

[0189] Please refer to Figures 13 and 14, where Figure 13 illustrates a schematic diagram of the imaging device according to the seventh embodiment of this disclosure, and Figure 14, from left to right, shows the spherical aberration, astigmatism, and distortion curves of the seventh embodiment. As shown in Figure 13, the imaging device 7 includes an imaging optical system (unlabeled) and an electronic photosensitive element IS. The imaging optical system, along the optical path from the object side to the image side, includes an aperture ST, a first lens E1, an aperture stop S1, a second lens E2, an aperture stop S2, a third lens E3, a fourth lens E4, a fifth lens E5, an aperture stop S3, a sixth lens E6, a filter element E7, and an imaging surface IMG. The electronic photosensitive element IS is disposed on the imaging surface IMG. The imaging optical system includes six lenses (E1, E2, E3, E4, E5, E6), and there are no other interposed lenses between each lens.

[0190] The first lens E1 has positive refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical. Its object-side surface has a point of inflection and a critical point off-axis.

[0191] The second lens E2 has negative refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is concave near the optical axis. Both surfaces are aspherical. Its object-side surface has one inflection point, and its image-side surface has two inflection points.

[0192] The third lens E3 has positive refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical. Its object-side surface has three inflection points, its image-side surface has one inflection point, and its object-side surface has two critical points off-axis.

[0193] The fourth lens E4 has negative refractive power and is made of plastic. Its object-side surface is concave near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical. Its object-side surface has three inflection points, and its image-side surface has one inflection point.

[0194] The fifth lens E5 has positive refractive power and is made of plastic. Its object-side surface is concave near the optical axis, and its image-side surface is convex near the optical axis. Both surfaces are aspherical. Its object-side surface has three inflection points, and its image-side surface has four inflection points. Its object-side surface has two critical points off-axis, and its image-side surface has two critical points off-axis.

[0195] The sixth lens E6 has positive refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is concave near the optical axis. Both surfaces are aspherical. Its object-side surface has three inflection points, its image-side surface has two inflection points, its object-side surface has two critical points off-axis, and its image-side surface has one critical point off-axis.

[0196] The filter element E7 is made of glass and is located between the sixth lens E6 and the imaging surface IMG. It does not affect the focal length of the imaging optical system.

[0197] In this embodiment, the aperture ST is located between the subject and the first lens E1. Furthermore, the thickness of the third lens E3 along the optical axis is the largest among the thicknesses of all lenses in the imaging optical system along the optical axis. Additionally, the absolute focal length of the fourth lens E4 is the smallest among the absolute focal lengths of all lenses in the imaging optical system.

[0198] Please refer to Table 7A and Table 7B below.

[0199] Table 7A, Seventh Embodiment f (focal length) = 3.14 mm, Fno (aperture value) = 1.60, HFOV (half angle of view) = 47.0 degrees. surface radius of curvature thickness Material Refractive index Abbe number focal length 0 Subject unlimited unlimited 1 aperture flat 0.044 2 First lens 9.5173 (ASP) 0.441 plastic 1.562 44.6 8.11 3 -8.5932 (ASP) 0.155 4 Aperture flat -0.119 5 Second lens 2.2484 (ASP) 0.277 plastic 1.614 25.6 -17.81 6 1.7774 (ASP) 0.252 7 Aperture flat 0.030 8 Third lens 5.6988 (ASP) 0.850 plastic 1.544 56.0 4.09 9 -3.4622 (ASP) 0.431 10 Fourth lens -1.0585 (ASP) 0.270 plastic 1.697 16.3 -3.86 11 -1.9280 (ASP) 0.030 12 Fifth lens -91.0805 (ASP) 0.514 plastic 1.551 44.8 5.00 13 -2.6763 (ASP) 0.174 14 Aperture flat -0.130 15 Sixth lens 0.9269 (ASP) 0.532 plastic 1.551 44.8 17.50 16 0.8165 (ASP) 0.742 17 Filter element flat 0.210 Glass 1.517 64.2 - 18 flat 0.541 19 Imaging surface flat - The reference wavelength (d-line) is 587.6 nm. The effective radius of surface 4 (aperture S1) is 0.970 mm. The effective radius of surface 7 (aperture S2) is 1.116 mm. The effective radius of surface 14 (aperture S3) is 2.419 mm.

[0200] Table 7B, Aspherical Coefficients surface 2 3 5 6 k = -7.07386E+01 -5.70055E+01 -4.40266E-01 9.43037E-01 A4 = -6.8648602E-02 -2.0009460E-01 -2.2327176E-01 -1.8526227E-01 A6 = 8.7141729E-01 1.2539622E+00 3.2018496E-01 2.6091315E-02 A8 = -7.4311891E+00 -6.4338472E+00 2.1620017E+00 6.3250133E-01 A10 = 3.1992832E+01 2.0435267E+01 -1.6139476E+01 -2.5167019E+00 A12 = -7.7383916E+01 -3.8947377E+01 4.9672875E+01 5.1443030E+00 A14 = 1.0919507E+02 4.3305400E+01 -8.5333059E+01 -6.6562708E+00 A16 = -8.8919877E+01 -2.6335668E+01 8.4517533E+01 5.4450158E+00 A18 = 3.8550489E+01 7.3182009E+00 -4.5082437E+01 -2.5605692E+00 A20 = -6.8473001E+00 -4.5822989E-01 1.0028254E+01 5.2425406E-01 surface 8 9 10 11 k = 4.76061E+00 -3.46016E+00 -6.18213E-01 -9.61817E-01 A4 = -4.0737684E-02 -2.6953879E-03 -3.7820685E-02 -2.0706314E-01 A6 = -1.6511629E-01 -4.2880543E-01 -3.7419003E-01 3.5739858E-01 A8 = 8.2291712E-01 1.5217040E+00 3.1061274E+00 -1.5534504E-01 A10 = -2.2759036E+00 -3.1605958E+00 -7.9547124E+00 -4.5054743E-01 A12 = 3.6150687E+00 3.8991326E+00 1.0843881E+01 8.3388508E-01 A14 = -3.3697050E+00 -2.9167129E+00 -8.6560672E+00 -6.3404573E-01 A16 = 1.6818668E+00 1.2866651E+00 4.0632256E+00 2.5503075E-01 A18 = -3.3981375E-01 -3.0466941E-01 -1.0399064E+00 -5.3460623E-02 A20 = - 2.9629940E-02 1.1198999E-01 4.6171003E-03 Surface 12 13 15 16 k = 2.62325E+01 -2.86344E+01 -1.38449E+00 -1.00214E+00 A4 = 3.5295715E-01 9.9757840E-02 -2.0877759E-01 -3.1769218E-01 A6 = -3.7871573E-01 1.1802569E-01 7.6624581E-02 1.4462628E-01 A8 = 2.8492021E-01 -1.8535782E-01 -2.5758365E-02 -5.9296543E-02 A1 = -1.5745403E-01 1.1077001E-01 5.0E-03 1.8783327E-02 A12 = 6.0693124E-02 -3.7124031E-02 -5.2506935E-04 -4.2786908E-03 A14 = -1.5449226E-02 7.4084698E-03 1.3128226E-04 6.6318560E-04 A16 = 2.4146422E-03 -8.6587903E-04 -4.0041537E-05 -6.5379435E-05 A18 = -2.0653362E-04 5.4366127E-05 5.2885129E-06 3.6488951E-06 A20 = 7.3270533E-06 -1.4076117E-06 -2.4685192E-07 -8.6664263E-08

[0201] In the seventh embodiment, the equation of the aspherical curve is expressed in the form of the first embodiment. Furthermore, the definitions described in Table 7C below are the same as those in the first embodiment, and will not be repeated here.

[0202] Table 7C, Polynomial Data f [millimeters] 3.14 10×f56 / f34 0.40 Fno 1.60 f / R7+f / R8 -4.59 HFOV [degrees] 47.0 10×(R3 - R4) / (R3 + R4) 1.17 FOV [degrees] 94.0 R2 / R10 3.21 TL / ImgH 1.67 |R10 / R9| 0.03 [[ID=z7]] TL / f 1.66 R10 / CT5 -5.21 TL / f6 0.30 ΣCT / ΣAT 3.50 TL / R1 0.55 (CT3 + CT5) / (CT3 - CT5) 4.06 TL / R9 -0.06 T34 / (T12 + T45 + T56) 3.92 |f3 / f5| 0.82 Y1R1×Y6R2 / (Y3R1×Y3R1) 1.90 |f / f1| + |f / f2| 0.56 SAG5R2 / CT5 0.24

[0203] <Eighth Embodiment>

[0204] It should be noted that in the original text, there is a tag "z7" which seems to be a mislabeled "27". I have corrected it in the translation for consistency. If this is not what you intended, please let me know.Please refer to Figures 15 and 16, where Figure 15 illustrates a schematic diagram of the imaging device according to the eighth embodiment of this disclosure, and Figure 16, from left to right, shows the spherical aberration, astigmatism, and distortion curves of the eighth embodiment. As shown in Figure 15, the imaging device 8 includes an imaging optical system (unlabeled) and an electronic photosensitive element IS. The imaging optical system, along the optical path from the object side to the image side, includes an aperture ST, a first lens E1, an aperture stop S1, a second lens E2, an aperture stop S2, a third lens E3, a fourth lens E4, a fifth lens E5, a sixth lens E6, a filter element E7, and an imaging surface IMG. The electronic photosensitive element IS is disposed on the imaging surface IMG. The imaging optical system includes six lenses (E1, E2, E3, E4, E5, E6), and there are no other interposed lenses between each lens.

[0205] The first lens E1 has positive refractive power and is made of plastic. Its object-side surface is concave near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical.

[0206] The second lens E2 has positive refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is concave near the optical axis. Both surfaces are aspherical, and its object-side surface has a point of inflection.

[0207] The third lens E3 has positive refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical. Its object-side surface has two inflection points, its image-side surface has one inflection point, and its object-side surface has a critical point off-axis.

[0208] The fourth lens E4 has negative refractive power and is made of plastic. Its object-side surface is concave near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical. Its object-side surface has a recurve point, and its image-side surface also has a recurve point.

[0209] The fifth lens E5 has positive refractive power and is made of plastic. Its object-side surface is concave near the optical axis, and its image-side surface is convex near the optical axis. Both surfaces are aspherical. Its object-side surface has two inflection points, and its image-side surface has four inflection points. Its object-side surface has two critical points off-axis, and its image-side surface has two critical points off-axis.

[0210] The sixth lens E6 has positive refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is concave near the optical axis. Both surfaces are aspherical. Its object-side surface has two inflection points, and its image-side surface has one inflection point. Its object-side surface has two critical points off-axis, and its image-side surface has one critical point off-axis.

[0211] The filter element E7 is made of glass and is located between the sixth lens E6 and the imaging surface IMG. It does not affect the focal length of the imaging optical system.

[0212] In this embodiment, the aperture ST is located between the subject and the first lens E1. Furthermore, the thickness of the third lens E3 along the optical axis is the largest among the thicknesses of all lenses in the imaging optical system along the optical axis. Additionally, the absolute focal length of the fourth lens E4 is the smallest among the absolute focal lengths of all lenses in the imaging optical system.

[0213] Please refer to Table 8A and Table 8B below.

[0214] Table 8A, Eighth Embodiment f (focal length) = 3.04 mm, fno (aperture value) = 1.80, HFOV (half angle of view) = 47.6 degrees. surface radius of curvature thickness Material Refractive index Abbe number focal length 0 Subject unlimited unlimited 1 aperture flat 0.049 2 First lens -39.4306 (ASP) 0.338 plastic 1.545 56.1 14.67 3 -6.6651 (ASP) 0.165 4 Aperture flat -0.135 5 Second lens 1.8763 (ASP) 0.320 plastic 1.669 19.5 124.86 6 1.7882 (ASP) 0.258 7 Aperture flat 0.070 8 Third lens 6.3122 (ASP) 1.066 plastic 1.544 56.0 3.82 9 -2.9104 (ASP) 0.313 10 Fourth lens -0.9920 (ASP) 0.304 plastic 1.669 19.5 -3.51 11 -1.9285 (ASP) 0.035 12 Fifth lens -120.4574 (ASP) 0.523 plastic 1.544 56.0 5.39 13 -2.8680 (ASP) 0.035 14 Sixth lens 0.9129 (ASP) 0.570 plastic 1.544 56.0 11.16 15 0.8380 (ASP) 0.800 16 Filter element flat 0.210 Glass 1.517 64.2 - 17 flat 0.445 18 Imaging surface flat - The reference wavelength (d-line) is 587.6 nm. The effective radius of surface 4 (aperture S1) is 0.890 mm. The effective radius of surface 7 (aperture S2) is 0.990 mm.

[0215] Table 8B, Aspheric Coefficient surface 2 3 5 6 k = 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 A4 = -1.9656037E-02 -3.1961915E-01 -3.4234429E-01 -1.2846311E-01 A6 = 1.5822859E-01 2.3886958E+00 1.7449693E+00 -1.3384021E-02 A8 = -1.5373330E+00 -1.2451362E+01 -7.2049091E+00 8.9229387E-01 A10 = 8.2314777E+00 4.4058954E+01 2.0295958E+01 -3.7264181E+00 A12 = -2.8222291E+01 -1.0578073E+02 -3.8573694E+01 8.2887248E+00 A14 = 6.0726158E+01 1.6790779E+02 4.8364749E+01 -1.1131975E+01 A16 = -7.8814556E+01 -1.6792343E+02 -3.8275819E+01 8.9741396E+00 A18 = 5.6212876E+01 9.5587181E+01 1.7310748E+01 -3.9888711E+00 A20 = -1.6896066E+01 -2.3580879E+01 -3.4119588E+00 7.5093482E-01 Surface 8 9 10 11 k = 0.00000E+00 0.00000E+00 -6.51786E-01 -1.00000E+00 A4 = -7.5281330E-02 -5.4436441E-02 -1.0064613E-01 -​​​​​​​​​​​​​​​​​​​​​​​​​​​-7.4556974E+00 -3.0141922E-01 A12 = -7.9398195E+00 -1.7413301E+00 1.1136553E+01 7.3463889E-01 A14 = 9.8028434E+00 4.0829900E+00 -1.0726228E+01 -7.1031536E-01 A16 = -7.3996791E+00 -4.5586760E+00 7.0851678E+00 4.0852954E-01 A18 = 3.0984941E+00 3.0128343E+00 -3.2541115E+00 -1.5072085E-01 A20 = -5.4714840E-01 -1.2067027E+00 1.0043413E+00 3.5259832E-02 A22 = - 2.7197209E-01 -1.8720541E-01 -4.7788782E-03 A24 = - -2.6496768E-02 1.5795196E-02 2.8563816E-04 surface 12 13 14 15 k = 0.00000E+00 -3.19278E+01 -1.36407E+00 -1.00000E+00 A4 = 3.7152428E-01 5.5918840E-02 -2.6593562E-01 -3.0908730E-01 A6 = -4.1529774E-01 2.7858501E-01 2.5527257E-01 1.7677917E-01 A8 = 3.5665325E-01 -4.5556015E-01 -3.0435481E-01 -1.2237238E-01 A10 = -2.5709617E-01 3.7628098E-01 2.7567214E-01 7.7311657E-02 A12 = 1.5021687E-01 -2.0524106E-01 -1.7984931E-01 -3.8083081E-02 A14 = -6.8484603E-02 7.9255868E-02 8.3974536E-02 1.3845435E-02 A16 = 2.3576615E-02 -2.1991195E-02 -2.8026340E-02 -3.6510076E-03 A18 = -5.9282558E-03 4.3288077E-03 6.6754006E-03 6.9100372E-04 A20 = 1.0416727E-03 -5.8528860E-04 -1.1235924E-03 -9.2407294E-05 A22 = -1.1982122E-04 5.1352381E-05 1.3034953E-04 8.4858312E-06 A24 = 8.0460436E-06 -2.6209316E-06 -9.9029105E-06 -5.0741622E-07 A26 = -2.3812124E-07 5.8886601E-08 4.4295596E-07 1.7745081E-08 A28 = - - -8.8352054E-09 -2.7478449E-10

[0216] In the eighth embodiment, the equation for the aspherical curve is expressed as in the first embodiment. Furthermore, the definitions in Table 8C below are the same as in the first embodiment and will not be repeated here.

[0217] Table 8C, Polynomial Data f [millimeters] 3.04 10×f56 / f34 0.03 Fno 1.80 f / R7+f / R8 -4.65 HFOV [degree] 47.6 10×(R3-R4) / (R3+R4) 0.24 FOV [degree] 95.3 R2 / R10 2.32 TL / ImgH 1.71 |R10 / R9| 0.02 TL / f 1.75 R10 / CT5 -5.48 TL / f6 0.48 ΣCT / ΣAT 4.21 TL / R1 -0.13 (CT3+CT5) / (CT3-CT5) 2.93 TL / R9 -0.04 T34 / (T12+T45+T56) 3.13 |f3 / f5| 0.71 Y1R1×Y6R2 / (Y3R1×Y3R1) 1.96 |f / f1|+|f / f2| 0.23 SAG5R2 / CT5 0.28

[0218] <Ninth Embodiment>

[0219] Please refer to Figures 17 and 18, where Figure 17 illustrates a schematic diagram of the imaging device according to the ninth embodiment of this disclosure, and Figure 18, from left to right, shows the spherical aberration, astigmatism, and distortion curves of the ninth embodiment. As shown in Figure 17, the imaging device 9 includes an imaging optical system (unlabeled) and an electronic photosensitive element IS. The imaging optical system, along the optical path from the object side to the image side, includes an aperture ST, a first lens E1, an aperture stop S1, a second lens E2, an aperture stop S2, a third lens E3, a fourth lens E4, a fifth lens E5, an aperture stop S3, a sixth lens E6, a filter element E7, and an imaging surface IMG. The electronic photosensitive element IS is disposed on the imaging surface IMG. The imaging optical system includes six lenses (E1, E2, E3, E4, E5, E6), and there are no other interposed lenses between each lens.

[0220] The first lens E1 has positive refractive power and is made of plastic. Its object-side surface is concave near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical.

[0221] The second lens E2 has negative refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is concave near the optical axis. Both surfaces are aspherical. Its object-side surface has one inflection point, and its image-side surface has two inflection points.

[0222] The third lens E3 has positive refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical. Its object-side surface has two inflection points, its image-side surface has one inflection point, and its object-side surface has a critical point off-axis.

[0223] The fourth lens E4 has negative refractive power and is made of plastic. Its object-side surface is concave near the optical axis, and its image-side surface is convex near the optical axis. Both surfaces are aspherical. Its object-side surface has two inflection points, and its image-side surface has one inflection point.

[0224] The fifth lens E5 has positive refractive power and is made of plastic. Its object-side surface is concave near the optical axis, and its image-side surface is convex near the optical axis. Both surfaces are aspherical. Its object-side surface has two inflection points, and its image-side surface has four inflection points. Its object-side surface has two critical points off-axis, and its image-side surface has two critical points off-axis.

[0225] The sixth lens E6 has positive refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is concave near the optical axis. Both surfaces are aspherical. Its object-side surface has three inflection points, its image-side surface has two inflection points, its object-side surface has two critical points off-axis, and its image-side surface has one critical point off-axis.

[0226] The filter element E7 is made of glass and is located between the sixth lens E6 and the imaging surface IMG. It does not affect the focal length of the imaging optical system.

[0227] In this embodiment, the aperture ST is located between the subject and the first lens E1. Furthermore, the thickness of the third lens E3 along the optical axis is the largest among the thicknesses of all lenses in the imaging optical system along the optical axis. Additionally, the absolute focal length of the fourth lens E4 is the smallest among the absolute focal lengths of all lenses in the imaging optical system.

[0228] Please refer to Table 9A and Table 9B below.

[0229] Table 9A, Ninth Embodiment f (focal length) = 3.05 mm, Fno (aperture value) = 1.65, HFOV (half angle of view) = 47.3 degrees surface radius of curvature thickness Material Refractive index Abbe number focal length 0 Subject unlimited unlimited 1 aperture flat 0.051 2 First lens -259.3254 (ASP) 0.359 plastic 1.544 56.0 10.56 3 -5.6241 (ASP) 0.165 4 Aperture flat -0.135 5 Second lens 2.1016 (ASP) 0.308 plastic 1.697 16.3 -36.71 6 1.8252 (ASP) 0.238 7 Aperture flat 0.063 8 Third lens 5.4217 (ASP) 0.750 plastic 1.544 56.0 3.92 9 -3.3479 (ASP) 0.514 10 Fourth lens -1.0337 (ASP) 0.270 plastic 1.697 16.3 -3.70 11 -1.9108 (ASP) 0.030 12 Fifth lens -69.5735 (ASP) 0.529 plastic 1.562 44.6 5.10 13 -2.7616 (ASP) 0.173 14 Aperture flat -0.135 15 Sixth lens 0.9107 (ASP) 0.527 plastic 1.551 44.8 13.10 16 0.8281 (ASP) 0.800 17 Filter element flat 0.210 Glass 1.517 64.2 - 18 flat 0.407 19 Imaging surface flat - The reference wavelength (d-line) is 587.6 nm. The effective radius of surface 4 (aperture S1) is 0.945 mm. The effective radius of surface 7 (aperture S2) is 1.059 mm. The effective radius of surface 14 (aperture S3) is 2.397 mm.

[0230] Table 9B, Aspheric Coefficients surface 2 3 5 6 k = 9.00000E+01 -6.35690E+01 -1.06707E-03 1.20395E+00 A4 = -7.3279995E-03 -9.2476960E-02 -1.5772101E-01 -1.9373912E-01 A6 = -5.1768333E-01 -6.3678422E-01 2.8978441E-03 2.6688295E-01 A8 = 4.8362290E+00 7.2083355E+00 2.3005821E+00 -8.4548393E-01 A10 = -2.3905030E+01 -3.3366364E+01 -1.1301015E+01 2.0962108E+00 A12 = 6.8298747E+01 8.7402385E+01 2.7885003E+01 -3.5840103E+00 A14 = -1.1743586E+02 -1.3853411E+02 -4.0258270E+01 3.9654465E+00 A16 = <00035�8> 1.1994867E+02 1.3152094E+02 3.4254366E+01 -2.8266200E+00 A18 = -6.7033818E+01 -6.8822498E+01 [[ID=зо]] -1.5905401E+01 1.2141814E+00 A20 = 1.5779402E+01 1.5261060E+01 З.1062932E+00 -2.4084613E-01 Surface 8 9 10 11 k = 4.05374E+00 <0003:599> -3.73696E+00 -6.28863E-01 -9.55665E-01 A4 = -7.7069809E-02 -5.6513343E-02 -9.1005437E-02 -2.2799820E-01 A6 = 7.0792870E-02 -2.0849212E-02 It should be noted that there seems to be a minor error in the original text where "<00035�8>" is likely a misspelling and should be " ". This has been corrected in the translation for consistency. 4.4941469E-02 4.2701576E-01 A8 = 3.7798049E-02 -6.0330336E-02 1.5684774E+00 -2.9087136E-01 A10 = -8.1706388E-01 5.1659171E-01 -4.6726658E+00 -2.8126090E-01 A12 = 2.0700433E+00 -1.3806074E+00 6.6403008E+00 7.0517010E-01 A14 = -2.4537345E+00 1.8071496E+00 -5.3661080E+00 -5.7847952E-01 A16 = 1.4076568E+00 -1.2759199E+00 2.5163684E+00 2.4326863E-01 A18 = -3.1008782E-01 4.6369131E-01 -6.3784748E-01 -5.2878061E-02 A20 = - -6.7475514E-02 6.7572085E-02 4.7291324E-03 surface 12 13 15 16 k = -9.00000E+01 -2.79481E+01 -1.38915E+00 -1.00287E+00 A4 = 3.4128768E-01 9.7294010E-02 -2.0385318E-01 -2.9518645E-01 A6 = -3.4891699E-01 1.2265380E-01 6.8858975E-02 1.1380011E-01 A8 = 2.5114266E-01 -1.9043765E-01 -2.0281843E-02 -3.6622834E-02 A10 = -1.3732781E-01 1.1416751E-01 2.3591108E-03 8.2225617E-03 A12 = 5.4366024E-02 -3.8467972E-02 4.1556954E-04 -1.0946890E-03 A14 = -1.4614654E-02 7.7272035E-03 -9.7651982E-05 4.5072499E-05 A16 = 2.4619067E-03 -9.1031743E-04 -5.0716803E-06 9.1409324E-06 A18 = -2.3161241E-04 5.7703740E-05 2.2899171E-06 -1.4152463E-06 A20 = 9.2657023E-06 -1.5113402E-06 -1.3673966E-07 6.1068550E-08

[0231] In the ninth embodiment, the equation for the aspherical curve is expressed as in the first embodiment. Furthermore, the definitions in Table 9C below are the same as in the first embodiment and will not be repeated here.

[0232] Table 9C, Polynomial Data f [millimeters] 3.05 10×f56 / f34 0.58 Fno 1.65 f / R7+f / R8 -4.54 HFOV [degree] 47.3 10×(R3-R4) / (R3+R4) 0.70 FOV [degree] 94.5 R2 / R10 2.04 TL / ImgH 1.63 |R10 / R9| 0.04 TL / f 1.67 R10 / CT5 -5.22 TL / f6 0.39 ΣCT / ΣAT 3.00 TL / R1 -0.02 (CT3+CT5) / (CT3-CT5) 5.79 TL / R9 -0.07 T34 / (T12+T45+T56) 5.24 |f3 / f5| 0.77 Y1R1×Y6R2 / (Y3R1×Y3R1) 1.97 |f / f1|+|f / f2| 0.37 SAG5R2 / CT5 0.25

[0233] <Tenth Implementation Example>

[0234] Please refer to Figures 19 and 20, where Figure 19 is a schematic diagram of the imaging device according to the tenth embodiment of this disclosure, and Figure 20 shows the spherical aberration, astigmatism, and distortion curves of the tenth embodiment from left to right. As shown in Figure 19, the imaging device 10 includes an imaging optical system (unlabeled) and an electronic photosensitive element IS. The imaging optical system includes, from the object side to the image side, an aperture ST, a first lens E1, an aperture S1, a second lens E2, an aperture S2, a third lens E3, a fourth lens E4, a fifth lens E5, an aperture S3, a sixth lens E6, a filter element E7, and an imaging surface IMG. The electronic photosensitive element IS is disposed on the imaging surface IMG. The imaging optical system comprises six lenses (E1, E2, E3, E4, E5, E6) with no other interleaved lenses between them.

[0235] The first lens E1 has positive refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical. Its object-side surface has a point of inflection and a critical point off-axis.

[0236] The second lens E2 has negative refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is concave near the optical axis. Both surfaces are aspherical, and its object-side surface has a point of inflection.

[0237] The third lens E3 has positive refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical. Its object-side surface has two inflection points, its image-side surface has one inflection point, and its object-side surface has two critical points off-axis.

[0238] The fourth lens E4 has negative refractive power and is made of plastic. Its object-side surface is concave near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical. Its object-side surface has a recurve point, and its image-side surface also has a recurve point.

[0239] The fifth lens E5 has positive refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical. Its object-side surface has one inflection point, and its image-side surface has two inflection points. Its object-side surface has one critical point off-axis, and its image-side surface has two critical points off-axis.

[0240] The sixth lens E6 has positive refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is concave near the optical axis. Both of its surfaces are aspherical. Its object-side surface has three inflection points, and its image-side surface has one inflection point. Its object-side surface has two critical points off-axis, and its image-side surface has one critical point off-axis.

[0241] The filter element E7 is made of glass and is located between the sixth lens E6 and the imaging surface IMG. It does not affect the focal length of the imaging optical system.

[0242] In this embodiment, the aperture ST is located between the subject and the first lens E1. Furthermore, the thickness of the third lens E3 along the optical axis is the largest among the thicknesses of all lenses in the imaging optical system along the optical axis. Additionally, the absolute focal length of the fourth lens E4 is the smallest among the absolute focal lengths of all lenses in the imaging optical system.

[0243] Please refer to Table 10A and Table 10B below.

[0244] Table 10A, Tenth Embodiment f (focal length) = 3.01 mm, Fno (aperture value) = 1.80, HFOV (half angle of view) = 47.6 degrees. surface radius of curvature thickness Material Refractive index Abbe number focal length 0 Subject unlimited unlimited 1 aperture flat 0.043 2 First lens 11.7647 (ASP) 0.380 plastic 1.567 37.4 7.18 3 -6.1484 (ASP) 0.123 4 Aperture flat -0.093 5 Second lens 2.1651 (ASP) 0.300 plastic 1.639 23.5 -14.84 6 1.6672 (ASP) 0.259 7 Aperture flat 0.010 8 Third lens 7.3404 (ASP) 1.083 plastic 1.544 56.0 3.76 9 -2.6855 (ASP) 0.256 10 Fourth lens -1.0189 (ASP) 0.300 plastic 1.669 19.5 -3.28 11 -2.1280 (ASP) 0.030 12 Fifth lens 21.2645 (ASP) 0.558 plastic 1.551 44.8 5.08 13 -3.1941 (ASP) 0.200 14 Aperture flat -0.170 15 Sixth lens 0.8444 (ASP) 0.534 plastic 1.544 56.0 10.29 16 0.7728 (ASP) 1.222 17 Filter element flat 0.210 Glass 1.517 64.2 - 18 flat 0.044 19 Imaging surface flat - The reference wavelength (d-line) is 587.6 nm. The effective radius of surface 4 (aperture S1) is 0.842 mm. The effective radius of surface 7 (aperture S2) is 1.021 mm. The effective radius of surface 14 (aperture S3) is 2.372 mm.

[0245] Table 10B, Aspheric Coefficients surface 2 3 5 6 k = -9.00000E+01 -3.43062E+01 -5.69324E-01 1.00129E+00 A4 = -3.5239411E-02 -1.6498096E-01 -2.3174592E-01 -1.9073968E-01 A6 = 2.4418086E-01 1.2002914E+00 1.2421259E+00 2.6743942E-01 A8 = -1.5461045E+00 -7.4786435E+00 -5.8853075E+00 -8.8058182E-01 A10 = 4.3484002E+00 3.1295844E+01 1.8807898E+01 2.5300545E+00 A12 = -4.6201237E+00 -8.8877016E+01 -4.0182487E+01 -5.4101151E+00 A14 = -5.4943338E+00 1.6506462E+02 5.5652583E+01 7.4078168E+00 A16 = 2.0389668E+01 -1.9063873E+02 -4.7762460E+01 -6.2063719E+00 A18 = -2.0465221E+01 1.2381936E+02 2.3022813E+01 2.9253204E+00 A20 = 7.1219503E+00 -3.4504579E+01 -4.7665102E+00 -6.0075392E-01 Surface 8 9 10 11 k = 2.36616E+01 -7.31666E-01 -6.38442E-01 -1.08869E+00 A4 = -2.7605895E-02 -3.2520596E-02 -1.5344897E-01 -2.8135315E-01 A6 = -2.5495806E-01 -4.0858061E-01 3.7389711E-01 8.3854081E-01 A8 = 1.3670199E+00 1.6014125E+00 1.3792614E+00 -1.3180944E+00 A10 = -4.0029189E+00 -3.2213587E+00 -5.7379553E+00 1.1331596E+00 A12 = 6.7765081E+00 3.4143666E+00 8.8579354E+00 -5.2216238E-01 A14 = -6.6140336E+00 -1.8943423E+00 -7.2290851E+00 1.0905268E-01 A16 = 3.4226252E+00 4.7775668E-01 3.3033074E+00 2.4672677E-03 A18 = -7.2042001E-01 -1.7960312E-02 -7.9962585E-01 -5.0290551E-03 A20 = - <​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​3.4405760E-02 1.1591154E-01 A8 = 4.5800689E-01 1.1829391E-02 7.9259592E-03 -2.6873083E-02 A10 = -2.7116085E-01 -2.1953906E-02 -5.2389425E-03 1.6635600E-03 A12 = 1.0525589E-01 1.4744617E-02 5.6378145E-05 1.0527434E-03 A14 = -2.6097749E-02 -4.6789536E-03 5.2713188E-04 -3.5744195E-04 A16 = 3.9653794E-03 7.9250774E-04 -1.4327312E-04 5.1945584E-05 A18 = -3.3627506E-04 -6.9428802E-05 1.5471513E-05 -3.7468837E-06 A20 = 1.2217052E-05 2.4756287E-06 -6.1867250E-07 1.0902971E-07

[0246] In the tenth embodiment, the equation for the aspherical curve is expressed as in the first embodiment. Furthermore, the definitions in Table 10C below are the same as in the first embodiment and will not be repeated here.

[0247] Table 10C, Polynomial Data f [millimeters] 3.01 10×f56 / f34 -0.51 Fno 1.80 f / R7+f / R8 -4.38 HFOV [degree] 47.6 10×(R3-R4) / (R3+R4) 1.30 FOV [degree] 95.3 R2 / R10 1.92 TL / ImgH 1.69 |R10 / R9| 0.15 TL / f 1.74 R10 / CT5 -5.72 TL / f6 0.51 ΣCT / ΣAT 5.13 TL / R1 0.45 (CT3+CT5) / (CT3-CT5) 3.13 TL / R9 0.25 T34 / (T12+T45+T56) 2.84 |f3 / f5| 0.74 Y1R1×Y6R2 / (Y3R1×Y3R1) 2.00 |f / f1|+|f / f2| 0.62 SAG5R2 / CT5 0.32

[0248] <Eleventh Embodiment>

[0249] Please refer to Figures 21 and 22, where Figure 21 illustrates a schematic diagram of the imaging device according to the eleventh embodiment of this disclosure, and Figure 22, from left to right, shows the spherical aberration, astigmatism, and distortion curves of the eleventh embodiment. As shown in Figure 21, the imaging device 11 includes an imaging optical system (unlabeled) and an electronic photosensitive element IS. The imaging optical system, along the optical path from the object side to the image side, includes an aperture ST, a first lens E1, an aperture stop S1, a second lens E2, an aperture stop S2, a third lens E3, a fourth lens E4, a fifth lens E5, an aperture stop S3, a sixth lens E6, a filter element E7, and an imaging surface IMG. The electronic photosensitive element IS is disposed on the imaging surface IMG. The imaging optical system includes six lenses (E1, E2, E3, E4, E5, E6), and there are no other interposed lenses between each lens.

[0250] The first lens E1 has positive refractive power and is made of glass. Its object-side surface is concave near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical.

[0251] The second lens E2 has negative refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is concave near the optical axis. Both surfaces are aspherical, and its object-side surface has a point of inflection.

[0252] The third lens E3 has positive refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical. Its object-side surface has three inflection points, its image-side surface has one inflection point, and its object-side surface has two critical points off-axis.

[0253] The fourth lens E4 has negative refractive power and is made of plastic. Its object-side surface is concave near the optical axis, and its image-side surface is convex near the optical axis. Both surfaces are aspherical. Its object-side surface has two inflection points, and its image-side surface also has two inflection points.

[0254] The fifth lens E5 has positive refractive power and is made of plastic. Its object-side surface is concave near the optical axis, and its image-side surface is convex near the optical axis. Both surfaces are aspherical. Its object-side surface has three inflection points, and its image-side surface has four inflection points. Its object-side surface has two critical points off-axis, and its image-side surface has two critical points off-axis.

[0255] The sixth lens E6 has positive refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is concave near the optical axis. Both of its surfaces are aspherical. Its object-side surface has three inflection points, its image-side surface has two inflection points, its object-side surface has three critical points off-axis, and its image-side surface has one critical point off-axis.

[0256] The filter element E7 is made of glass and is located between the sixth lens E6 and the imaging surface IMG. It does not affect the focal length of the imaging optical system.

[0257] In this embodiment, the aperture ST is located between the subject and the first lens E1. Furthermore, the thickness of the third lens E3 along the optical axis is the largest among the thicknesses of all lenses in the imaging optical system along the optical axis. Additionally, the absolute focal length of the fourth lens E4 is the smallest among the absolute focal lengths of all lenses in the imaging optical system.

[0258] Please refer to Table 11A and Table 11B below.

[0259] Table 11A, Eleventh Embodiment f (focal length) = 3.67 mm, fno (aperture value) = 2.00, HFOV (half angle of view) = 49.7 degrees. surface radius of curvature thickness Material Refractive index Abbe number focal length 0 Subject unlimited unlimited 1 aperture flat 0.046 2 First lens -123.8178 (ASP) 0.385 Glass 1.547 62.7 11.34 3 -5.9099 (ASP) 0.145 4 Aperture flat -0.105 5 Second lens 2.5410 (ASP) 0.302 plastic 1.650 21.8 -28.97 6 2.1340 (ASP) 0.245 7 Aperture flat 0.054 8 Third lens 9.3382 (ASP) 1.061 plastic 1.544 56.0 4.13 9 -2.8395 (ASP) 0.392 10 Fourth lens -1.1357 (ASP) 0.346 plastic 1.656 21.3 -3.93 11 -2.2738 (ASP) 0.038 12 Fifth lens -33.0076 (ASP) 0.554 plastic 1.545 56.1 5.65 13 -2.8334 (ASP) 0.167 14 Aperture flat -0.129 15 Sixth lens 1.0409 (ASP) 0.569 plastic 1.544 56.0 25.99 16 0.9072 (ASP) 1.442 17 Filter element flat 0.235 Glass 1.517 64.2 - 18 flat 0.325 19 Imaging surface flat - The reference wavelength (d-line) is 587.6 nm. The effective radius of surface 4 (aperture S1) is 0.974 mm. The effective radius of surface 7 (aperture S2) is 1.145 mm. The effective radius of surface 14 (aperture S3) is 2.772 mm.

[0260] Table 11B, Aspheric Coefficients surface 2 3 5 6 k = 9.00000E+01 -7.72389E+01 8.76033E-02 1.37166E+00 A4 = -3.2624719E-02 -1.3530345E-01 -1.3735904E-01 -2.1689249E-01 A6 = 8.8849831E-02 4.0321548E-01 2.9813766E-01 9.3475182E-01 A8 = -2.2493519E-01 -7.3806452E-01 -2.5083615E-01 -4.4118950E+00 A10 = 2.5250101E-01 6.6625530E-01 -6.9305560E-01 1.3268811E+01 A12 = -1.0652194E-01 -2.3632886E-01 2.2358270E+00 -2.5126159E+01 A14 = - - -2.9731381E+00 2.9645129E+01 A16 = - - 2.2763968E+00 -2.1105589E+01 A18 = - - -1.0107169E+00 8.2908688E+00 A20 = - - 2.0338129E-01 -1.3794420E+00 Surface 8 9 10 11 k = 1.60067E+01 -1.21506E+00 -6.33521E-01 -1.16532E+00 A4 = -3.3068149E-02 1.2452854E-02 -7.3007571E-02 -1.6589953E-01 A6 = -1.6404160E-01 -3.0403697E-01 1.4425769E-01 3.5179826E-01 A8 = 9.6694792E-01 6.1181123E-01 8.2597779E-02 -4.7090810E-01 A10 = -2.4952143E+00 -6.6843908E-01 -3.0669303E-01 4.1281843E-01 A12 = 3.4963835E+00 4.2075421E-01 3.5220074E-01 -2.3608833E-01 A14 = -2.7905418E+00 -1.4760008E-01 -2.4047293E-01 8.8381727E-02 A16 = 1.1840642E+00 1.9400260E-02 1.0072829E-01 -2.0974517E-02 A18 = -2.0537174E-01 3.2759482E-03 -2.3181569E-02 2.8735767E-03 A20 = - -9.4019717E-04 2.2022282E-03 -1.7363253E-04 Surface 12 13 15 16 k = 5.60606E+01 -2.65810E+01 -1.37989E+00 -9.99026E-01 A4 = 2.5001676E-01 8.5818737E-02 -1.2979641E-01 -2.2497710E-01 A6 = -2.0048904E-01 2.4975088E-02 8.4146424E-03 7.5757806E-02 A8 = 1.0922160E-01 -3.8990233E-02 1.6047140E-02 -2.1647660E-02 A10 = -4.1420669E-02 1.5393733E-02 -1.0167147E-02 4.6199305E-03 A12 = 1.0132428E-02 -2.9473945E-03 2.9353212E-03 -6.9636322E-04 A14 = -1.4458831E-03 2.4502691E-04 -4.5570189E-04 7.0680789E-05 A16 = 9.1709244E-05 3.0328910E-06 3.8313653E-05 -4.5034392E-06 A18 = 1.1092956E-06 -1.8208490E-06 -1.5725586E-06 1.5866286E-07 A20 = -2.9836324E-07 8.3617628E-08 2.1826629E-08 -2.2764159E-09

[0261] In the eleventh embodiment, the equation of the curve for the aspherical surface is expressed in the form of the first embodiment. Furthermore, the definitions described in Table 11C below are the same as in the first embodiment and will not be repeated here.

[0262] Table 11C, Polynomial Data f [millimeters] 3.67 10×f56 / f34 0.30 Fno 2.00 f / R7+f / R8 -4.84 HFOV [degree] 49.7 10×(R3-R4) / (R3+R4) 0.87 FOV [degree] 99.5 R2 / R10 2.09 TL / ImgH 1.50 |R10 / R9| 0.09 TL / f 1.64 R10 / CT5 -5.11 TL / f6 0.23 ΣCT / ΣAT 3.99 TL / R1 -0.05 (CT3+CT5) / (CT3-CT5) 3.19 TL / R9 -0.18 T34 / (T12+T45+T56) 3.38 |f3 / f5| 0.73 Y1R1×Y6R2 / (Y3R1×Y3R1) 1.96 |f / f1|+|f / f2| 0.45 SAG5R2 / CT5 0.18

[0263] <Twelfth Embodiment>

[0264] Please refer to Figures 23 and 24, where Figure 23 illustrates a schematic diagram of the imaging device according to the twelfth embodiment of this disclosure, and Figure 24, from left to right, shows the spherical aberration, astigmatism, and distortion curves of the twelfth embodiment. As shown in Figure 23, the imaging device 12 includes an imaging optical system (unlabeled) and an electronic photosensitive element IS. The imaging optical system, along the optical path from the object side to the image side, includes a first lens E1, an aperture ST, a second lens E2, a third lens E3, a fourth lens E4, a fifth lens E5, a sixth lens E6, a filter element E7, and an imaging surface IMG. The electronic photosensitive element IS is disposed on the imaging surface IMG. The imaging optical system includes six lenses (E1, E2, E3, E4, E5, E6), and there are no other interposed lenses between each lens.

[0265] The first lens E1 has positive refractive power and is made of plastic. Its object-side surface is concave near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical.

[0266] The second lens E2 has negative refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is concave near the optical axis. Both of its surfaces are aspherical. Its object-side surface has a point of inflection, and its image-side surface also has a point of inflection.

[0267] The third lens E3 has positive refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical. Its object-side surface has two inflection points, and its object-side surface has a critical point off-axis.

[0268] The fourth lens E4 has negative refractive power and is made of plastic. Its object-side surface is concave near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical. Its object-side surface has two inflection points, its image-side surface has one inflection point, and its image-side surface has a critical point off-axis.

[0269] The fifth lens E5 has positive refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical. Its object-side surface has two inflection points, and its image-side surface has three inflection points. Its object-side surface has one critical point off-axis, and its image-side surface has two critical points off-axis.

[0270] The sixth lens E6 has positive refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is concave near the optical axis. Both surfaces are aspherical. Its object-side surface has four inflection points, and its image-side surface has one inflection point. Its object-side surface has a critical point off-axis, and its image-side surface has a critical point off-axis.

[0271] The filter element E7 is made of glass and is located between the sixth lens E6 and the imaging surface IMG. It does not affect the focal length of the imaging optical system.

[0272] In this embodiment, the aperture ST is located between the subject and the second lens E2. Furthermore, the thickness of the third lens E3 along the optical axis is the largest among the thicknesses of all lenses in the imaging optical system along the optical axis.

[0273] Please refer to Table 12A and Table 12B below.

[0274] Table 12A, Twelfth Embodiment f (focal length) = 2.60 mm, Fno (aperture value) = 2.01, HFOV (half angle of view) = 50.1 degrees. surface radius of curvature thickness Material Refractive index Abbe number focal length 0 Subject unlimited unlimited 1 First lens -31.9717 (ASP) 0.394 plastic 1.551 44.8 5.64 2 -2.8430 (ASP) -0.044 3 aperture flat 0.089 4 Second lens 1.9600 (ASP) 0.236 plastic 1.657 21.3 -9.60 5 1.4238 (ASP) 0.314 6 Third lens 6.1112 (ASP) 0.783 plastic 1.544 56.0 3.13 7 -2.2543 (ASP) 0.424 8 Fourth lens -0.9068 (ASP) 0.240 plastic 1.686 18.4 -3.64 9 -1.5763 (ASP) 0.030 10 Fifth lens 7.2711 (ASP) 0.640 plastic 1.544 56.0 4.97 11 -4.1667 (ASP) 0.050 12 Sixth lens 0.9195 (ASP) 0.575 plastic 1.562 44.6 26.33 13 0.7599 (ASP) 0.717 14 Filter element flat 0.210 Glass 1.517 64.2 - 15 flat 0.049 16 Imaging surface flat - The reference wavelength (d-line) is 587.6 nm.

[0275] Table 12B, Aspheric Coefficient surface 1 2 4 5 k = 9.00000E+01 -5.07076E+01 -1.64046E+01 -5.13441E+00 A4 = 6.5276026E-03 -1.4519180E-01 9.3087631E-02 -1.2002949E-01 A6 = -4.6762445E-02 4.5644889E-01 -1.5463121E-01 3.0541376E-01 A8 = 6.2921624E-02 -1.1705150E+00 -3.5045862E-02 -6.1631464E-01 A10 = -8.1307474E-02 1.8019203E+00 5.1914055E-01 7.5634522E-01 A12 = 4.5053449E-02 -1.6043424E+00 -1.0338121E+00 -6.0417951E-01 A14 = -6.4782837E-03 6.4872669E-01 6.1402384E-01 2.1672379E-01 Surface 6 7 8 9 k = -3.34215E+01 -3.31595E+00 -1.31793E+00 -1.80949E+00 A4 = -3.2803446E-02 -7.5940637E-02 -3.1522014E-01 -3.6987331E-01 A6 = 8.8607441E-04 -2.2226532E-01 1.2589482E+00 1.1718616E+00 A8 = 1.2876784E-01 1.0349134E+00 -1.4476440E+00 -1.6568097E+00 A10 = -9.6541534E-01 -2.3695507E+00 -1.9186128E-01 1.2150540E+00 A12 = 2.5525067E+00 3.0234163E+00 2.3271257E+00 -3.3948220E-01 A14 = -3.7283786E+00 -2.3376234E+00 -2.6615504E+00 -1.0901974E-01 A16 = 3.1138668E+00 1.1083484E+00 1.4569936E+00 1.1259923E-01 A18 = -1.3801430E+00 -3.0753313E-01 -4.0537103E-01 -3.2808478E-02 A20 = 2.5314367E-01 3.9999876E-02 4.6011813E-02 3.4804024E-03 Surface 10 11 12 13 k = 1.04722E+01 -2.45360E+01 -3.52996E+00 -2.19169E+00 A4 = 1.8374555E-01 6.7024827E-02 -7.6432358E-02 -1.3934500E-01 A6 = -1.4567988E-01 1.0220919E-01 -2.9426506E-02 6.9396418E-02 A8 = 4.0373170E-02 -1.2960373E-01 3.0673447E-02 -2.6737503E-02 A10 = 2.0659630E-02 6.4834363E-02 -1.5697263E-02 7.3172076E-03 A12 = -2.9294647E-02 -1.8442614E-02 6.0501042E-03 -1.3414709E-03 A14 = 1.4803413E-02 3.2562771E-03 -1.5099162E-03 1.5863370E-04 A16 = -3.9526193E-03 -3.6038452E-04 2.1953721E-04 -1.1659758E-05 A18 = 5.4788733E-04 2.3348249E-05 -1.6887042E-05 4.9026019E-07 A20 = -3.0932863E-05 -6.8298889E-07 5.3233863E-07 -9.1738265E-09

[0276] In the twelfth embodiment, the equation of the curve for the aspherical surface is expressed in the form of the first embodiment. Furthermore, the definitions described in Table 12C below are the same as in the first embodiment and will not be repeated here.

[0277] Table 12C, Polynomial Data f [millimeters] 2.60 10×f56 / f34 2.56 Fno 2.01 f / R7+f / R8 -4.52 HFOV [degree] 50.1 10×(R3-R4) / (R3+R4) 1.58 FOV [degree] 100.2 R2 / R10 0.68 TL / ImgH 1.49 |R10 / R9| 0.57 TL / f 1.81 R10 / CT5 -6.51 TL / f6 0.18 ΣCT / ΣAT 3.32 TL / R1 -0.15 (CT3+CT5) / (CT3-CT5) 9.95 TL / R9 0.65 T34 / (T12+T45+T56) 3.39 |f3 / f5| 0.63 Y1R1×Y6R2 / (Y3R1×Y3R1) 2.18 |f / f1|+|f / f2| 0.73 SAG5R2 / CT5 0.16

[0278] <Thirteenth Embodiment>

[0279] Please refer to Figures 25 and 26, where Figure 25 illustrates a schematic diagram of the imaging device according to the thirteenth embodiment of this disclosure, and Figure 26, from left to right, shows the spherical aberration, astigmatism, and distortion curves of the thirteenth embodiment. As shown in Figure 25, the imaging device 13 includes an imaging optical system (unlabeled) and an electronic photosensitive element IS. The imaging optical system, along the optical path from the object side to the image side, includes an aperture ST, a first lens E1, an aperture stop S1, a second lens E2, an aperture stop S2, a third lens E3, a fourth lens E4, a fifth lens E5, an aperture stop S3, a sixth lens E6, a filter element E7, and an imaging surface IMG. The electronic photosensitive element IS is disposed on the imaging surface IMG. The imaging optical system includes six lenses (E1, E2, E3, E4, E5, E6), and there are no other interposed lenses between each lens.

[0280] The first lens E1 has positive refractive power and is made of plastic. Its object-side surface is concave near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical.

[0281] The second lens E2 has negative refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is concave near the optical axis. Both of its surfaces are aspherical. Its object-side surface has a point of inflection, and its image-side surface also has a point of inflection.

[0282] The third lens E3 has positive refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is convex near the optical axis. Both of its surfaces are aspherical. Its object-side surface has two inflection points, its image-side surface has one inflection point, and its object-side surface has a critical point off-axis.

[0283] The fourth lens E4 has negative refractive power and is made of plastic. Its object-side surface is concave near the optical axis, and its image-side surface is convex near the optical axis. Both surfaces are aspherical. Its object-side surface has two inflection points, and its image-side surface also has two inflection points.

[0284] The fifth lens E5 has positive refractive power and is made of plastic. Its object-side surface is concave near the optical axis, and its image-side surface is convex near the optical axis. Both surfaces are aspherical. Its object-side surface has two inflection points, and its image-side surface has four inflection points. Its object-side surface has two critical points off-axis, and its image-side surface has two critical points off-axis.

[0285] The sixth lens E6 has positive refractive power and is made of plastic. Its object-side surface is convex near the optical axis, and its image-side surface is concave near the optical axis. Both surfaces are aspherical. Its object-side surface has two inflection points, and its image-side surface has one inflection point. Its object-side surface has a critical point off-axis, and its image-side surface has a critical point off-axis.

[0286] The filter element E7 is made of glass and is located between the sixth lens E6 and the imaging surface IMG. It does not affect the focal length of the imaging optical system.

[0287] In this embodiment, the aperture ST is located between the subject and the first lens E1. Furthermore, the thickness of the third lens E3 along the optical axis is the largest among the thicknesses of all lenses in the imaging optical system along the optical axis. Additionally, the absolute focal length of the fourth lens E4 is the smallest among the absolute focal lengths of all lenses in the imaging optical system.

[0288] Please refer to Table 13A and Table 13B below.

[0289] Table 13A, Thirteenth Embodiment f (focal length) = 2.80 mm, fno (aperture value) = 1.80, HFOV (half angle of view) = 49.7 degrees surface radius of curvature thickness Material Refractive index Abbe number focal length 0 Subject unlimited unlimited 1 aperture flat 0.073 2 First lens -5.4054 (ASP) 0.339 plastic 1.566 37.4 9.84 3 -2.8061 (ASP) 0.125 4 aperture flat -0.095 5 Second lens 2.3353 (ASP) 0.325 plastic 1.697 16.3 -34.36 6 2.0062 (ASP) 0.228 7 aperture flat 0.069 8 Third lens 6.2689 (ASP) 1.060 plastic 1.544 55.9 3.71 9 -2.7982 (ASP) 0.340 10 Fourth lens -0.9945 (ASP) 0.270 plastic 1.686 18.4 -3.32 11 -1.9586 (ASP) 0.030 12 Fifth lens -40.5859 (ASP) 0.581 plastic 1.551 44.8 7.48 13 -3.7608 (ASP) 0.171 14 aperture flat -0.139 15 Sixth lens 0.8213 (ASP) 0.618 plastic 1.562 44.6 5.33 16 0.8251 (ASP) 0.800 17 Filter element flat 0.210 Glass 1.517 64.2 - 18 flat 0.295 19 Imaging surface flat - The reference wavelength (d-line) is 587.6 nm. The effective radius of surface 4 (aperture S1) is 0.879 mm. The effective radius of surface 7 (aperture S2) is 1.076 mm. The effective radius of surface 14 (aperture S3) is 2.296 mm.

[0290] Table 13B, Aspheric Coefficients surface 2 3 5 6 k = -5.92053E+01 -4.90018E+01 1.29383E-01 1.33036E+00 A4 = 1.3275740E-01 -3.7135782E-01 -2.5257187E-01 -1.4863587E-01 A6 = -3.6896615E+00 3.5777989E+00 2.0139114E+00 -6.0848619E-01 A8 = 4.1612396E+01 -2.4145260E+01 -1.1685405E+01 4.9957714E+00 A10 = -2.6012148E+02 1.0283397E+02 4.2685731E+01 -1.8561324E+01 A12 = 9.7417604E+02 -2.8052200E+02 -1.0140451E+02 3.9869578E+01 A14 = -2.2412052E+03 4.8824201E+02 1.5571211E+02 -5.2149786E+01 A16 = 3.1037438E+03 -5.2400046E+02 -1.4891487E+02 4.0760993E+01 A18 = -2.3742171E+03 3.1569251E+02 8.0493418E+01 -1.7427109E+01 A20 = 7.7067175E+02 -8.1597408E+01 -1.8755484E+01 3.1221984E+00 Surface 8 9 10 11 k = 6.57480E+00 -7.56676E-01 -6.29183E-01 -9.53907E-01 A4 = -6.3404555E-02 -8.4244124E-02 -1.6834371E-02 -1.9682478E-01 A6 = 3.3807214E-02 1.9321691E-01 -5.9056295E-01 2.7350822E-01 A8 = 1.2459867E-03 -1.0344039E+00 3.7984244E+00 -3.6829021E-02 A10 = -4.8594950E-01 2.6273529E+00 -9.6109402E+00 -3.0321427E-01 A12 = 1.4546953E+00 -3.8015026E+00 1.4635152E+01 2.5304935E-01 A14 = -1.9046548E+00 3.2637030E+00 -1.4856857E+01 1.3486850E-01 A16 = 1.1667191E+00 -1.6483055E+00 1.0403729E+01 -3.4426172E-01 A18 = -2.6965378E-01 4.5139485E-01 -5.0092588E+00 2.4750396E-01 A20 = - -5.1438637E-02 1.5917034E+00 -9.1168275E-02 A22 = - - -3.0077514E-01 1.7538958E-02 A24 = - - 2.5533152E-02 -1.4026716E-03 surface 12 13 15 16 k = -7.12913E+01 -2.53553E+01 -1.45073E+00 -9.95527E-01 A4 = 4.0197787E-01 9.9523535E-02 -2.1019504E-01 -2.2000517E-01 A6 = -4.2099151E-01 1.1761098E-01 9.2019001E-02 -1.2264029E-01 A8 = 2.8907851E-01 -1.8285104E-01 -6.4537765E-02 3.4427328E-01 A10 = -1.2384595E-01 1.0527371E-01 5.3047148E-02 -3.7302669E-01 A12 = 1.6929519E-02 -3.2152896E-02 -3.7521397E-02 2.5374750E-01 A14 = 1.4108698E-02 4.9139966E-03 1.9365848E-02 -1.1793910E-01 A16 = -9.9234133E-03 -9.5376602E-05 -7.0197522E-03 3.8684150E-02 A18 = 3.0697390E-03 -9.5797941E-05 1.7935840E-03 -9.0840556E-03 A20 = -5.3123515E-04 1.6603021E-05 -3.2248296E-04 1.5307203E-03 A22 = 4.9926409E-05 -1.2153821E-06 3.9969442E-05 -1.8321497E-04 A24 = -1.9941663E-06 3.5368624E-08 -3.2506453E-06 1.5166712E-05 A26 = - - 1.5611146E-07 -8.2300802E-07 A28 = - - -3.3561969E-09 2.6231626E-08 A30 = - - - -3.7018168E-10

[0291] In the thirteenth embodiment, the equation of the curve for the aspherical surface is expressed in the form of the first embodiment. Furthermore, the definitions described in Table 13C below are the same as in the first embodiment and will not be repeated here.

[0292] Table 13C, Polynomial Data f [millimeters] 2.80 10×f56 / f34 -0.03 Fno 1.80 f / R7+f / R8 -4.25 HFOV [degree] 49.7 10×(R3-R4) / (R3+R4) 0.76 FOV [degree] 99.5 R2 / R10 0.75 TL / ImgH 1.68 |R10 / R9| 0.09 TL / f 1.87 R10 / CT5 -6.47 TL / f6 0.98 ΣCT / ΣAT 4.38 TL / R1 -0.97 (CT3+CT5) / (CT3-CT5) 3.43 TL / R9 -0.13 T34 / (T12+T45+T56) 3.70 |f3 / f5| 0.50 Y1R1×Y6R2 / (Y3R1×Y3R1) 1.65 |f / f1|+|f / f2| 0.37 SAG5R2 / CT5 0.25

[0293] <Fourteenth Embodiment>

[0294] Please refer to Figure 27, which is a perspective view of an image capturing device according to the fourteenth embodiment of this disclosure. In this embodiment, the image capturing device 100 is a camera module. The image capturing device 100 includes an imaging lens 101, a driving device 102, an electronic image sensor 103, and an image stabilization module 104. The imaging lens 101 includes the image capturing optical system of the first embodiment described above, a lens barrel (not otherwise labeled) for carrying the image capturing optical system, and a support device (Holder Member, not otherwise labeled). The imaging lens 101 can also be replaced with the image capturing optical system of other embodiments described above, and this disclosure is not limited thereto. The image capturing device 100 uses the imaging lens 101 to focus light to generate an image, and cooperates with the driving device 102 to focus the image, finally imaging it on the electronic image sensor 103 and outputting it as image data.

[0295] The driving device 102 may have an auto-focus function, and its driving method can use a driving system such as a voice coil motor (VCM), microelectromechanical systems (MEMS), piezoelectric systems, and shape memory alloys. The driving device 102 enables the imaging lens 101 to achieve a better imaging position, allowing clear images to be captured of the subject at different object distances. In addition, the imaging device 100 is equipped with a high-sensitivity and low-noise electronic image sensor 103 (such as CMOS or CCD) located on the imaging surface of the imaging optical system, which can truly present the good imaging quality of the imaging optical system.

[0296] The image stabilization module 104 can be, for example, an accelerometer, a gyroscope, or a Hall effect sensor. The drive unit 102 can work in conjunction with the image stabilization module 104 to form an optical image stabilization (OIS) device. By adjusting the changes in different axes of the imaging lens 101, it can compensate for the blurry image caused by shaking during shooting, or use image compensation technology in the imaging software to provide electronic image stabilization (EIS) function, further improving the image quality of shooting in dynamic and low-light scenes.

[0297] <Fifteenth Embodiment>

[0298] Please refer to Figures 28 to 30, wherein Figure 28 shows a perspective view of one side of an electronic device according to the fifteenth embodiment of the present disclosure, Figure 29 shows a perspective view of the other side of the electronic device of Figure 28, and Figure 30 shows a system block diagram of the electronic device of Figure 28.

[0299] In this embodiment, the electronic device 200 is a smartphone. The electronic device 200 includes, according to the fourteenth embodiment, image capturing devices 100, 100a, 100b, 100c, 100d, and 100e, a flash module 201, a focus assist module 202, an image signal processor 203, a display module 204, and an image software processor 205. Image capturing devices 100, 100a, and 100b are all located on the same side of the electronic device 200 and are all single-focus. The focus assist module 202 may employ a laser ranging or a Time-of-Flight (ToF) module, but this disclosure is not limited to these. Image capturing devices 100c, 100d, 100e, and display module 204 are all located on the other side of electronic device 200, and display module 204 can serve as a user interface, allowing image capturing devices 100c, 100d, and 100e to function as front-facing cameras for selfies, but this disclosure is not limited thereto. Furthermore, image capturing devices 100a, 100b, 100c, 100d, and 100e can all include the image capturing optical system disclosed herein and can all have a structural configuration similar to that of image capturing device 100. In detail, each of the image capturing devices 100a, 100b, 100c, 100d, and 100e may include an imaging lens, a driving device, an electronic photosensitive element, and an image stabilization module, and each may include an optical path reversing element to reversing the optical path. The imaging lens of each of the image capturing devices 100a, 100b, 100c, 100d, and 100e may include, for example, the image capturing optical system disclosed herein, a lens barrel for supporting the image capturing optical system, and a support device.

[0300] Image capturing device 100 is a wide-angle image capturing device, image capturing device 100a is a telephoto image capturing device with optical path reversal, image capturing device 100b is an ultra-wide-angle image capturing device, image capturing device 100c is a wide-angle image capturing device, image capturing device 100d is an ultra-wide-angle image capturing device, and image capturing device 100e is a time-of-flight ranging image capturing device. In this embodiment, image capturing devices 100, 100a, and 100b have different viewing angles, allowing the electronic device 200 to provide different magnifications to achieve optical zoom shooting effects. Additionally, image capturing device 100e can acquire depth information of the image. The optical path reversal configuration of image capturing device 100a can, for example, have a structure similar to Figures 36 to 38, which can be referred to in the descriptions corresponding to Figures 36 to 38 above, and will not be repeated here. Furthermore, the image capturing devices 100, 100b, 100c, 100d, and 100e may also have an optical path reversal configuration, and may also have a structure similar to that of Figures 36 to 38, as described above with reference to the descriptions corresponding to Figures 36 to 38. The above-described electronic device 200 is exemplified by including multiple image capturing devices 100, 100a, 100b, 100c, 100d, and 100e, but the number and configuration of the image capturing devices are not intended to limit this disclosure.

[0301] When the user photographs the subject 206, the electronic device 200 uses the image capturing device 100, image capturing device 100a, or image capturing device 100b to focus the light and activate the flash module 201 for supplemental lighting. It also uses the subject distance information provided by the focus assist module 202 for fast focusing, and the image signal processor 203 performs image optimization processing to further improve the image quality produced by the imaging optical system. The focus assist module 202 can use an infrared or laser focus assist system to achieve fast focusing. In addition, the electronic device 200 can also use the image capturing device 100c, image capturing device 100d, or image capturing device 100e for shooting. The display module 204 can use a touch screen and, in conjunction with the diverse functions of the image software processor 205, can perform image shooting and image processing (or can use a physical shooting button). The image processed by the image software processor 205 can be displayed on the display module 204.

[0302] <Sixteenth Embodiment>

[0303] Please refer to Figures 31 and 32, wherein Figure 31 shows a schematic diagram of one side of an electronic device according to the sixteenth embodiment of the present disclosure, and Figure 32 shows a schematic diagram of the other side of the electronic device of Figure 31.

[0304] In this embodiment, the electronic device 300 is a smartphone. The electronic device 300 includes the image capturing devices 100, 100f, 100g, and 100h of the fourteenth embodiment, as well as a display module 304. As shown in FIG31, the image capturing devices 100, 100f, and 100g are all disposed on the same side of the electronic device 300 and are all single-focus. As shown in FIG32, the image capturing device 100h and the display module 304 are both disposed on the other side of the electronic device 300. The image capturing device 100h can serve as a front-facing camera to provide a selfie function, but this disclosure is not limited thereto. Furthermore, the image capturing devices 100f, 100g, and 100h can all include the image capturing optical system disclosed herein and can all have a structural configuration similar to that of the image capturing device 100. In detail, each of the imaging devices 100f, 100g, and 100h may include an imaging lens, a driving device, an electronic photosensitive element, and an image stabilization module. The imaging lens of each of the imaging devices 100f, 100g, and 100h may include, for example, the imaging optical system disclosed herein, a lens barrel for supporting the imaging optical system, and a support device.

[0305] Image capturing device 100 is a wide-angle image capturing device, image capturing device 100f is a telephoto image capturing device, image capturing device 100g is an ultra-wide-angle image capturing device, and image capturing device 100h is a wide-angle image capturing device. In this embodiment, image capturing devices 100, 100f, and 100g have different viewing angles, allowing the electronic device 300 to provide different magnifications to achieve optical zoom shooting effects. The above-described electronic device 300 is exemplified by including multiple image capturing devices 100, 100f, 100g, and 100h, but the number and configuration of the image capturing devices are not intended to limit this disclosure.

[0306] <Seventeenth Embodiment>

[0307] Please refer to Figure 33, which is a perspective view of one side of an electronic device according to the seventeenth embodiment of this disclosure.

[0308] In this embodiment, the electronic device 400 is a smartphone. The electronic device 400 includes, according to the fourteenth embodiment, image capturing devices 100i, 100j, 100k, 100m, 100n, 100p, 100q, and 100r, a flash module 401, a focus assist module, an image signal processor, a display module, and an image software processor (not shown). Image capturing devices 100i, 100j, 100k, 100m, 100n, 100p, 100q, and 100r are all located on the same side of the electronic device 400, while the display module is located on the other side of the electronic device 400. Furthermore, the imaging devices 100i, 100j, 100k, 100m, 100n, 100p, 100q, and 100r may all include the imaging optical system disclosed herein and may all have a structural configuration similar to that of the imaging device 100, which will not be elaborated further here.

[0309] Image capturing device 100 is a wide-angle image capturing device; image capturing device 100i is a telephoto image capturing device with a reversible optical path; image capturing device 100j is a telephoto image capturing device with a reversible optical path; image capturing device 100k is a wide-angle image capturing device; image capturing device 100m is an ultra-wide-angle image capturing device; image capturing device 100n is an ultra-wide-angle image capturing device; image capturing device 100p is a telephoto image capturing device; image capturing device 100q is a telephoto image capturing device; and image capturing device 100r is a time-of-flight ranging image capturing device. In this embodiment, image capturing devices 100, 100i, 100j, 100k, 100m, 100n, 100p, and 100q have different viewing angles, allowing the electronic device 400 to provide different magnification ratios to achieve optical zoom shooting effects. Furthermore, the image capturing device 100r can acquire depth information of the image. The optical path reversal configuration of the image capturing devices 100i and 100j can, for example, have a structure similar to that in Figures 36 to 38, as described above with reference to the corresponding Figures 36 to 38, and will not be repeated here. In addition, the image capturing devices 100, 100k, 100m, 100n, 100p, 100q, and 100r can also have an optical path reversal configuration, and can also, for example, have a structure similar to that in Figures 36 to 38, as described above with reference to the corresponding Figures 36 to 38. The above-described electronic device 400 is exemplified by including multiple image capturing devices 100, 100i, 100j, 100k, 100m, 100n, 100p, 100q, and 100r, but the number and configuration of the image capturing devices are not intended to limit this disclosure. When a user takes a picture of the subject, the electronic device 400 uses the image capturing device 100, image capturing device 100i, image capturing device 100j, image capturing device 100k, image capturing device 100m, image capturing device 100n, image capturing device 100p, image capturing device 100q or image capturing device 100r to focus the light and activate the flash module 401 to provide supplementary lighting. The subsequent processing is performed in a manner similar to that described in the previous embodiment, which will not be repeated here.

[0310] The image capturing device disclosed herein is not limited to smartphones. It can also be applied to mobile focusing systems as needed, offering excellent aberration correction and good image quality. For example, the image capturing device can be widely used in 3D image capture, digital cameras, mobile products, digital tablets, smart TVs, network surveillance equipment, dashcams, reversing cameras, multi-lens devices, recognition systems, motion-sensing game consoles, drones, wearable products, and personal video recorders. The aforementioned electronic devices are merely illustrative examples of practical applications of this disclosure and do not limit the scope of application of the image capturing device disclosed herein.

[0311] Although this disclosure is based on the preferred embodiments described above, it is not intended to limit this disclosure. Anyone skilled in the art may make some modifications and refinements without departing from the spirit and scope of this disclosure. Therefore, the scope of patent protection of this disclosure shall be determined by the claims attached to this specification.

[0312] 1,2,3,4,5,6,7,8,9,10,11,12,13,100,100a,100b,100c,100d,100e,100f,100g,100h,100i,100j,100k,100m,100n,100p,100q,100r: imaging device 101: Imaging Lens 102: Drive unit 103: Electronic photosensitive element 104: Image Stabilization Module 200, 300, 400: Electronic devices 201,401: Flash module 202: Focusing Assist Module 203: Image Signal Processor 204, 304: Display module 205: Image Software Processor 206: Subject OA1: First optical axis OA2: Second optical axis OA3: Third optical axis LF, LF1, LF2: Optical path switching elements LG: Lens Group ST: Aperture S1, S2, S3: Aperture E1: First lens E2: Second lens E3: Third Lens E4: Fourth Lens E5: Fifth Lens E6: Sixth Lens E7: Filter element IMG: Imaging Surface IS: Electronic photosensitive element P: Inversion point C: Critical point ΣAT: The sum of the distances between all adjacent lenses on the optical axis in an imaging optical system. ΣCT: The total thickness of all lenses in the imaging optical system along the optical axis. CT3: Thickness of the third lens on the optical axis CT5: Thickness of the fifth lens on the optical axis f: Focal length of the imaging optical system f1: Focal length of the first lens f2: Focal length of the second lens f3: Focal length of the third lens f5: Focal length of the fifth lens f6: Focal length of the sixth lens f34: Combined focal length of the third and fourth lenses f56: Combined focal length of the fifth and sixth lenses Fno: Aperture value of the imaging optical system FOV: The maximum angle of view in an imaging optical system. HFOV: Half of the maximum field of view in an imaging optical system ImgH: Maximum imaging height of the imaging optical system R1: Radius of curvature of the object-side surface of the first lens R2: Radius of curvature of the image-side surface of the first lens R3: Radius of curvature of the object-side surface of the second lens R4: Radius of curvature of the image-side surface of the second lens R7: Radius of curvature of the object-side surface of the fourth lens R8: Radius of curvature of the image-side surface of the fourth lens R9: Radius of curvature of the object-side surface of the fifth lens R10: Radius of curvature of the image-side surface of the fifth lens SAG5R2: The displacement parallel to the optical axis from the point where the image-side surface of the fifth lens intersects the optical axis to the position of the maximum effective radius of the image-side surface of the fifth lens. T12: The distance between the first lens and the second lens on the optical axis T34: The distance between the third and fourth lenses on the optical axis T45: The distance between the fourth and fifth lenses on the optical axis T56: The distance between the fifth and sixth lenses on the optical axis TL: Distance along the optical axis from the object-side surface of the first lens to the imaging plane. Y1R1: Maximum effective radius of the object-side surface of the first lens Y3R1: Maximum effective radius of the object-side surface of the third lens Y6R2: Maximum effective radius of the image-side surface of the sixth lens

Claims

1. An image-capturing optical system comprising six lenses, which are sequentially arranged from the object side to the image side along an optical path as a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens, and each of the six lenses has an object-side surface facing the object side and an image-side surface facing the image side; wherein, The imaging optical system comprises six lenses. The image-side surface of the second lens is concave near the optical axis. The third lens has positive refractive power, the fourth lens has negative refractive power and its image-side surface is convex near the optical axis, the fifth lens has positive refractive power and its image-side surface is convex near the optical axis, and the sixth lens has at least one inflection point on its image-side surface. The imaging optical system further includes an aperture located between the subject and the second lens. The distance from the object-side surface of the first lens to an imaging plane on the optical axis is TL, the focal length of the sixth lens is f6, and the radius of curvature of the object-side surface of the first lens is R1, satisfying the following conditions: -0.20 < TL / f6 < 1.50; and -1.50 < TL / R1 < 0.

60.

2. The imaging optical system as claimed in claim 1, wherein the distance from the object-side surface of the first lens to the imaging surface on the optical axis is TL, the focal length of the imaging optical system is f, and the maximum imaging height of the imaging optical system is ImgH, which satisfies the following conditions: 1.20 < TL / f < 2.20; and 0.90 < TL / ImgH < 2.

30.

3. The imaging optical system as claimed in claim 1, wherein the distance from the object-side surface of the first lens to the imaging surface on the optical axis is TL, and the radius of curvature of the object-side surface of the fifth lens is R9, which satisfies the following condition: -1.50 < TL / R9 < 0.

70.

4. The imaging optical system as described in claim 1, wherein the combined focal length of the third lens and the fourth lens is f34, and the combined focal length of the fifth lens and the sixth lens is f56, which satisfies the following condition: -1.00 < 10 × f56 / f34 < 3.

50.

5. The imaging optical system as claimed in claim 1, wherein the focal length of the imaging optical system is f, the radius of curvature of the object-side surface of the fourth lens is R7, and the radius of curvature of the image-side surface of the fourth lens is R8, which satisfies the following condition: -6.50 < f / R7 + f / R8 < -3.

00.

6. The imaging optical system as claimed in claim 1, wherein the radius of curvature of the object-side surface of the fifth lens is R9 and the radius of curvature of the image-side surface of the fifth lens is R10, which satisfies the following condition: 0.00 < |R10 / R9| < 0.

80.

7. The imaging optical system as claimed in claim 1, wherein the total thickness of all lenses in the imaging optical system on the optical axis is ΣCT, and the total distance between all adjacent lenses in the imaging optical system on the optical axis is ΣAT, which satisfies the following condition: 2.00 < ΣCT / ΣAT < 6.

00.

8. The imaging optical system as claimed in claim 1, wherein the thickness of the third lens on the optical axis is CT3 and the thickness of the fifth lens on the optical axis is CT5, which satisfies the following condition: 1.50 < (CT3+CT5) / (CT3-CT5) < 10.

50.

9. An image capturing device, comprising: an image capturing optical system as described in claim 1; and an electronic photosensitive element disposed on the imaging surface of the image capturing optical system.

10. An electronic device comprising: an image capturing device as described in claim 9.

11. An image-capturing optical system comprising six lenses, the six lenses being sequentially arranged from the object side to the image side along an optical path as a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens, and each of the six lenses having an object-side surface facing the object side and an image-side surface facing the image side; wherein, The imaging optical system comprises six lenses. The image-side surface of the first lens is convex near the optical axis, the image-side surface of the second lens is concave near the optical axis, the image-side surface of the fourth lens is convex near the optical axis, the fifth lens has positive refractive power, and the image-side surface of the sixth lens has at least one inflection point. The imaging optical system further includes an aperture located between the subject and the second lens. The distance from the object-side surface of the first lens to an imaging plane on the optical axis is TL, the focal length of the sixth lens is f6, the radius of curvature of the object-side surface of the first lens is R1, the radius of curvature of the object-side surface of the fifth lens is R9, and the radius of curvature of the image-side surface of the fifth lens is R10, satisfying the following conditions: -0.30 < TL / f6; -1.50 < TL / R1 < 0.70; and 0.00 < |R10 / R9| < 1.

00.

12. The imaging optical system as claimed in claim 11, wherein the third lens has positive refractive power and the fourth lens has negative refractive power; and wherein, The aperture value of the imaging optical system is Fno, and the maximum viewing angle of the imaging optical system is FOV, which satisfies the following conditions: Fno < 2.10; and 88.0 degrees < FOV < 103.0 degrees.

13. The imaging optical system as claimed in claim 11, wherein the distance from the object-side surface of the first lens to the imaging surface on the optical axis is TL, the focal length of the sixth lens is f6, and the radius of curvature of the object-side surface of the first lens is R1, which satisfies the following conditions: -0.15 < TL / f6 < 1.20; and -1.20 < TL / R1 < 0.

60.

14. The imaging optical system as claimed in claim 11, wherein the focal length of the imaging optical system is f, the focal length of the first lens is f1, and the focal length of the second lens is f2, which satisfies the following condition: 0.15 < |f / f1|+|f / f2| < 0.

80.

15. The imaging optical system as claimed in claim 11, wherein the radius of curvature of the object-side surface of the second lens is R3 and the radius of curvature of the image-side surface of the second lens is R4, which satisfy the following condition: -2.50 < 10×(R3-R4) / (R3+R4) < 2.

50.

16. The imaging optical system as claimed in claim 11, wherein the radius of curvature of the image-side surface of the first lens is R2 and the radius of curvature of the image-side surface of the fifth lens is R10, which satisfy the following condition: 0.60 < R2 / R10 < 7.

00.

17. The imaging optical system as claimed in claim 11, wherein the thickness of the third lens on the optical axis is the largest of the thicknesses of all lenses in the imaging optical system on the optical axis.

18. The imaging optical system as claimed in claim 11, wherein the displacement of the point where the image-side surface of the fifth lens intersects the optical axis to the position of the maximum effective radius of the image-side surface of the fifth lens parallel to the optical axis is SAG5R2, and the thickness of the fifth lens on the optical axis is CT5, which satisfies the following condition: 0.00 < SAG5R2 / CT5 < 1.

00.

19. An image-capturing optical system comprising six lenses, the six lenses being sequentially arranged from the object side to the image side along an optical path as a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens, and each of the six lenses having an object-side surface facing the object side and an image-side surface facing the image side; wherein, The imaging optical system comprises six lenses. The first lens has a convex image-side surface near the optical axis, the second lens has a concave image-side surface near the optical axis, the third lens has positive refractive power, the fourth lens has negative refractive power and its image-side surface is convex near the optical axis, the fifth lens has positive refractive power and its image-side surface is convex near the optical axis, and the sixth lens has at least one inflection point on its image-side surface. The distance from the object-side surface of the first lens to an imaging plane along the optical axis is TL. The focal length of the third lens is f3, the focal length of the fifth lens is f5, the focal length of the sixth lens is f6, and the radius of curvature of the object-side surface of the first lens is R1, satisfying the following conditions: -0.30 < TL / f6 < 1.20; -1.30 < TL / R1 < 0.60; and 0.35 < |f3 / f5| < 1.

20.

20. The imaging optical system as claimed in claim 19 further includes an aperture located between the subject and the first lens.

21. The imaging optical system as claimed in claim 19, wherein the sixth lens has positive refractive power and the image-side surface of the sixth lens has at least one critical point off-axis.

22. The imaging optical system as claimed in claim 19, wherein the radius of curvature of the object-side surface of the fifth lens is R9, the radius of curvature of the image-side surface of the fifth lens is R10, the distance from the object-side surface of the first lens to the imaging surface on the optical axis is TL, and the focal length of the sixth lens is f6, which satisfies the following conditions: 0.01 < |R10 / R9| < 0.60; and -0.10 < TL / f6 < 1.

00.

23. The imaging optical system as claimed in claim 19, wherein the radius of curvature of the image-side surface of the fifth lens is R10, and the thickness of the fifth lens on the optical axis is CT5, which satisfies the following condition: -8.00 < R10 / CT5 < -2.

00.

24. The imaging optical system as claimed in claim 19, wherein the absolute value of the focal length of the fourth lens is the smallest among the absolute values ​​of the focal lengths of all lenses in the imaging optical system; and wherein, The distance from the object-side surface of the first lens to the imaging surface on the optical axis is TL, and the radius of curvature of the object-side surface of the first lens is R1, which satisfies the following condition: -1.00 < TL / R1 ≤ 0.

55.

25. The imaging optical system as described in claim 19, wherein the optical axis spacing between the first lens and the second lens is T12, the optical axis spacing between the third lens and the fourth lens is T34, the optical axis spacing between the fourth lens and the fifth lens is T45, and the optical axis spacing between the fifth lens and the sixth lens is T56, which satisfies the following condition: 1.00 < T34 / (T12+T45+T56) < 6.

50.

26. The imaging optical system as described in claim 19, wherein the maximum effective radius of the object-side surface of the first lens is Y1R1, the maximum effective radius of the object-side surface of the third lens is Y3R1, and the maximum effective radius of the image-side surface of the sixth lens is Y6R2, which satisfies the following condition: 0.80 < Y1R1×Y6R2 / (Y3R1×Y3R1) < 4.

00.

27. The imaging optical system as described in claim 19, wherein the distance from the object-side surface of the first lens to the imaging plane on the optical axis is TL, the focal length of the third lens is f3, the focal length of the fifth lens is f5, the focal length of the sixth lens is f6, the radius of curvature of the object-side surface of the first lens is R1, the radius of curvature of the object-side surface of the fifth lens is R9, the radius of curvature of the image-side surface of the fifth lens is R10, the maximum effective radius of the object-side surface of the first lens is Y1R1, the maximum effective radius of the object-side surface of the third lens is Y3R1, the maximum effective radius of the image-side surface of the sixth lens is Y6R2, the optical axis spacing between the first and second lenses is T12, the optical axis spacing between the third and fourth lenses is T34, the optical axis spacing between the fourth and fifth lenses is T45, and the optical axis spacing between the fifth and sixth lenses is T56, satisfying the following condition: -0.09 ≤ TL / f6 ≤ 0.98; -0.97 ≤ TL / R1 ≤ 0.55; 0.02 ≤ |R10 / R9| ≤ 0.57; 0.45 ≤ |f3 / f5| ≤ 0.88; 1.65 ≤ Y1R1×Y6R2 / (Y3R1×Y3R1) ≤ 2.18; and 2.09 ≤ T34 / (T12+T45+T56) ≤ 5.24.

Images