Optical system, lens module and electronic equipment

Abstract

An optical system, a lens module and an electronic device, the optical system has four lenses with refractive power, and the optical system sequentially comprises a first lens with negative refractive power, a second lens with negative refractive power, a third lens with negative refractive power, a fourth lens with negative refractive power, a fifth lens with negative refractive power, a sixth lens with negative refractive power, a fifth lens with negative refractive power, and a sixth lens with negative refractive power, a second lens element with refractive power; a third lens element with positive refractive power having an object-side surface being convex in a paraxial region and an image-side surface being concave in a paraxial region; a fourth lens element with positive refractive power having an object-side surface being convex in a paraxial region and an image-side surface being concave in a paraxial region; the optical system satisfies the relational expression: 0.9 lt; fNOlt, FNOlt; 1.3, 160 degree lt; a FOVlt; 177 DEG C; the optical system has a larger aperture, a larger field angle and a higher image resolution, and is helpful for improving image quality and user experience.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical imaging, and particularly relates to an optical system, a lens module and an electronic device. Background Art

[0002] With the development of technology, especially in the fields of computer vision and image processing, the demand for high-performance optical systems is increasing continuously. ToF (Time of Flight) optical systems are mainly applied to depth perception and three-dimensional imaging, and are widely used in fields such as autonomous driving, robot navigation, virtual reality, and augmented reality. However, the shooting range of existing optical systems is still small, and it is difficult to ensure miniaturization when obtaining a larger field of view angle, and the relative illuminance is low. The imaging quality in low-light environments often fails to meet the requirements of modern applications. Therefore, it is particularly important to develop a lens with a large aperture and a large field of view angle. Summary of the Invention

[0003] The object of the present invention is to provide an optical system, a lens module and an electronic device, specifically a ToF optical system, which has a larger aperture, a larger field of view angle, and higher image resolution.

[0004] To achieve the object of the present invention, the present invention provides the following technical solutions:

[0005] In a first aspect, the present invention provides an optical system, the number of lenses with refractive power is four, and along the optical axis direction from the object side to the image side, it sequentially includes: a first lens with negative refractive power, the object side surface is concave near the circumference, and the image side surface is convex near the circumference; a second lens with refractive power; a third lens with positive refractive power, the object side surface is convex near the optical axis, and the image side surface is concave near the optical axis; a fourth lens with positive refractive power, the object side surface is convex near the optical axis, and the image side surface is concave near the optical axis.

[0006] In the optical system provided by the present application, by matching the refractive powers of the four lenses, a high-quality imaging effect in low light can be achieved; among them, the first lens has negative refractive power, its object side surface is concave at the circumference, and its image side surface is convex at the circumference, which is beneficial to the incidence and convergence of light rays in a large field of view range; the second lens has refractive power, which helps to correct the aberration generated by the front lens; the third lens has positive refractive power, its object side surface is convex near the optical axis, and its image side surface is concave near the optical axis, which is beneficial to delaying the light rays incident from the front lens into the system and delaying the angle; the fourth lens has positive refractive power, which is beneficial to correcting the spherical aberration, coma and distortion generated by the front group of lenses, can shorten the total length, and at the same time can suppress the light ray exit angle, and is also beneficial to the incidence of light rays in a large range onto the image plane.

[0007] In one implementation, the optical system satisfies the following relationships: 0.9 < FNO < 1.3, 160° < FOV < 177°; where FNO is the f-number of the optical system, and FOV is the maximum field of view angle of the optical system. When the above relationships are satisfied, it can ensure that the optical system has the characteristic of a large aperture, allowing the optical system to have sufficient light input, making the captured image clearer; and it can enable the optical system to have the characteristic of a large field of view angle, with a larger shooting range, and the optical system has the characteristics of high pixels and high definition.

[0008] In a second aspect, the present invention also provides a lens module, which includes the optical system according to any one of the implementations in the first aspect and an image sensor chip, and the image sensor chip is disposed on the image side of the optical system.

[0009] In a third aspect, the present invention also provides an electronic device, which includes a housing and the lens module in the second aspect, and the lens module is disposed within the housing. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the implementations of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the implementations or the prior art. Obviously, the drawings in the following description are only some implementations of the present invention, and those of ordinary skill in the art can obtain other drawings based on these drawings without creative efforts.

[0011] Figure 1 It is a schematic structural diagram of the optical system of the first embodiment;

[0012] Figure 2 It is an aberration diagram of the optical system of the first embodiment;

[0013] Figure 3 It is a schematic structural diagram of the optical system of the second embodiment;

[0014] Figure 4 It is an aberration diagram of the optical system of the second embodiment;

[0015] Figure 5 It is a schematic structural diagram of the optical system of the third embodiment;

[0016] Figure 6 It is an aberration diagram of the optical system of the third embodiment;

[0017] Figure 7 It is a schematic structural diagram of the optical system of the fourth embodiment;

[0018] Figure 8 It is an aberration diagram of the optical system of the fourth embodiment;

[0019] Figure 9Schematic structural diagram of the optical system of the fifth embodiment;

[0020] Figure 10 Aberration diagram of the optical system of the fifth embodiment;

[0021] Figure 11 Schematic structural diagram of the optical system of the sixth embodiment;

[0022] Figure 12 Aberration diagram of the optical system of the sixth embodiment;

[0023] Figure 13 Schematic structural diagram of the optical system of the seventh embodiment;

[0024] Figure 14 Aberration diagram of the optical system of the seventh embodiment;

[0025] Figure 15 Schematic diagram of the lens module provided by an embodiment of the present invention;

[0026] Figure 16 Schematic structural diagram of the electronic device provided by an embodiment of the present invention. Specific embodiments

[0027] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0028] In a first aspect, the present invention provides an optical system, and the number of lenses with refractive power is four. Along the optical axis direction from the object side to the image side, it successively includes: a first lens with negative refractive power, the object side surface is concave near the circumference, and the image side surface is convex near the circumference; a second lens with refractive power; a third lens with positive refractive power, the object side surface is convex near the optical axis, and the image side surface is concave near the optical axis; a fourth lens with positive refractive power, the object side surface is convex near the optical axis, and the image side surface is concave near the optical axis.

[0029] In the optical system provided by this application, by matching the refractive powers of four lenses, a high-quality imaging effect in low light can be achieved. Among them, the first lens has a negative refractive power, its object side is concave at the circumference, and its image side is convex at the circumference, which is conducive to the incidence and convergence of light in a large field of view. The second lens has a refractive power, which helps to correct the aberration generated by the front lens. The third lens has a positive refractive power, its object side is convex at the paraxial region, and its image side is concave at the paraxial region, which is conducive to delaying the light incident from the front lens into the system and delaying the angle. The fourth lens has a positive refractive power, which is conducive to correcting the spherical aberration, coma and distortion generated by the front group of lenses, can shorten the total length, and at the same time can suppress the light exit angle, and is also conducive to the incidence of light in a large range onto the image plane.

[0030] In one embodiment, the optical system satisfies the relationship: 0.9 < FNO < 1.3; where FNO is the f-number of the optical system. When the above relationship is satisfied, it can ensure that the optical system has the characteristic of a large aperture, allowing the optical system to have sufficient light input and making the captured image clearer. Optionally, the value of FNO can be 0.901, 0.930, 0.949, 0.950, 1.000, 1.050, 1.150, 1.200, 1.250, 1.299.

[0031] In one embodiment, the optical system satisfies the relationship: 160° < FOV < 177°; where FOV is the maximum field of view angle of the optical system. When the above relationship is satisfied, it can make the optical system have the characteristic of a large field of view angle, with a larger shooting range, and the optical system has the characteristics of high pixels and high definition. Optionally, the value of FOV can be 160.001, 163.739, 164.939, 167.292, 169.773, 170.265, 170.543, 173.233, 176.617, 176.999.

[0032] In one embodiment, the optical system satisfies the relationship: 140° < FOV / FNO < 180°. When the above relationship is satisfied, it can make the lens have a large field of view imaging while ensuring a large light input, making the image clearer. Optionally, the value of FOV / FNO can be 140.001, 141.294, 148.056, 156.011, 159.326, 161.688, 166.568, 173.784, 179.519, 179.999.

[0033] In one embodiment, the optical system satisfies the relation: 2.6 < TTL / ImgH < 2.8; where TTL is the distance from the object side surface of the first lens to the imaging surface on the optical axis, and ImgH is half of the image height corresponding to the maximum field of view angle of the optical system. When the above relation is satisfied, the optical system has the characteristic of being ultra-thin, and it is more advantageous for shooting scenes with medium focal distances and miniaturizing the imaging device. Optionally, the value of TTL / ImgH can be 2.601, 2.634, 2.676, 2.703, 2.754, 2.762, 2.776, 2.782, 2.792, 2.799.

[0034] In one embodiment, the optical system satisfies the relation: 1.7 < ImgH / BL < 2.2; where BL is the minimum distance from the image side surface of the fourth lens to the imaging surface. When the above relation is satisfied, on the one hand, there is a larger focusing range during the debugging process of the lens module, and on the other hand, the lens module may actually be used to shoot a target board, and a sufficient back focal length ensures that the lens can find the best focus point in this case. Optionally, the value of ImgH / BL can be 1.701, 1.797, 1.865, 2.029, 2.035, 2.037, 2.057, 2.058, 2.119, 2.199.

[0035] In one embodiment, the optical system satisfies the relation: 1.5 < ImgH / EPD < 2.2; where EPD is the entrance pupil diameter of the optical system. When the above relation is satisfied, under the premise of a certain eye pupil size, the size of the screen can be restricted, and the selection direction of the screen can be clarified. Optionally, the value of ImgH / EPD can be 1.501, 1.594, 1.674, 1.717, 1.724, 1.758, 1.864, 2.027, 2.115, 2.199.

[0036] In one embodiment, the optical system satisfies the relation: -2.9 < f1 / f < -2; where f is the effective focal length of the optical system, and f1 is the effective focal length of the first lens. When the above relation is satisfied, by controlling the ratio of the effective focal length of the first lens to the effective focal length of the entire optical system within a certain range, the refractive power of the first lens will not be too strong for the effective focal length of the entire optical system, and high-order spherical aberration can be corrected, so that the optical system has good imaging quality. Optionally, the value of f1 / f can be -2.001, -2.011, -2.035, -2.118, -2.192, -2.342, -2.545, -2.668, -2.859, -2.899.

[0037] In one embodiment, the optical system satisfies the relation: 5 < |f2| / f < 40; where f2 is the effective focal length of the second lens. When the above relation is satisfied, by controlling the ratio of the effective focal length of the second lens to the effective focal length of the entire optical system within a certain range, the refractive power of the second lens will not be too strong for the effective focal length of the entire optical system, and it can correct the high-order spherical aberration, enabling the optical system to have good imaging quality. Optionally, the value of |f2| / f can be 5.001, 5.119, 5.506, 5.579, 5.829, 6.513, 7.685, 10.485, 37.560, 39.999.

[0038] In one embodiment, the optical system satisfies the relation: 2.5 < f3 / f < 9; where f3 is the effective focal length of the third lens. When the above relation is satisfied, by controlling the ratio of the effective focal length of the third lens to the effective focal length of the entire optical system within a certain range, the refractive power of the third lens will not be too strong for the effective focal length of the entire optical system, and it can correct the high-order spherical aberration, enabling the optical system to have good imaging quality. Optionally, the value of f3 / f can be 2.601, 2.667, 2.831, 2.843, 3.005, 3.215, 3.812, 5.466, 8.644, 8.999.

[0039] In one embodiment, the optical system satisfies the relation: 1.1 < f4 / f < 1.4; where f4 is the effective focal length of the fourth lens. When the above relation is satisfied, by controlling the ratio of the effective focal length of the fourth lens to the effective focal length of the entire optical system within a certain range, the refractive power of the fourth lens will not be too strong for the effective focal length of the entire optical system, and it can correct the high-order spherical aberration, enabling the optical system to have good imaging quality. Optionally, the value of f4 / f can be 1.101, 1.125, 1.170, 1.260, 1.273, 1.301, 1.305, 1.338, 1.340, 1.399.

[0040] In one embodiment, the optical system satisfies the relation: -1.7 < R1 / f < -1.2; where R1 is the curvature radius of the object side surface of the first lens at the optical axis. When the above relation is satisfied, by controlling the ratio of the curvature radius of the first lens to the effective focal length of the entire optical system within a certain range, the astigmatism of the first lens can be within a reasonable range, and it can effectively balance the astigmatism generated by the front lens, thereby enabling the optical system to have good imaging quality. Optionally, the value of R1 / f can be -1.201, 1.309, -1.422, -1.468, -1.485, -1.547, -1.575, -1.598, -1.654, -1.699.

[0041] In one embodiment, the optical system satisfies the relation: 6 < |R2| / f < 28; R2 is the radius of curvature of the image side surface of the first lens at the optical axis. When the above relation is satisfied, by controlling the ratio of the radius of curvature of the first lens to the effective focal length of the entire optical system within a certain range, the astigmatism of the first lens can be within a reasonable range, and it can effectively balance the astigmatism generated by the previous lens, so that the optical system has good imaging quality. Optionally, the value of |R2| / f can be 6.001, 7.164, 7.465, 10.615, 10.725, 11.173, 11.734, 17.643, 24.600, 27.999.

[0042] In one embodiment, the optical system satisfies the relation: 5 < |R3| / f < 20; R3 is the radius of curvature of the object side surface of the second lens at the optical axis. When the above relation is satisfied, by controlling the ratio of the radius of curvature of the second lens to the effective focal length of the entire optical system within a certain range, the astigmatism of the second lens can be within a reasonable range, and it can effectively balance the astigmatism generated by the previous lens, so that the optical system has good imaging quality. Optionally, the value of |R3| / f can be 5.001, 5.168, 5.761, 7.586, 7.826, 8.178, 9.548, 13.434, 18.904, 19.999.

[0043] In one embodiment, the optical system satisfies the relation: 2.7 < |R4| / f < 40; R4 is the radius of curvature of the image side surface of the second lens at the optical axis. When the above relation is satisfied, by controlling the ratio of the radius of curvature of the second lens to the effective focal length of the entire optical system within a certain range, the astigmatism of the second lens can be within a reasonable range, and it can effectively balance the astigmatism generated by the previous lens, so that the optical system has good imaging quality. Optionally, the value of |R4| / f can be 2.701, 2.784, 5.737, 6.074, 6.974, 7.084, 15.252, 22.844, 35.912, 39.999.

[0044] In one embodiment, the optical system satisfies the relation: 1.2 < R5 / f < 2.8; R5 is the radius of curvature of the object side surface of the third lens at the optical axis. When the above relation is satisfied, by controlling the ratio of the radius of curvature of the third lens to the effective focal length of the entire optical system within a certain range, the astigmatism of the third lens can be within a reasonable range, and it can effectively balance the astigmatism generated by the previous lens, so that the optical system has good imaging quality. Optionally, the value of R5 / f can be 1.201, 1.298, 1.397, 1.427, 1.503, 1.532, 1.695, 2.086, 2.673, 2.799.

[0045] In one embodiment, the optical system satisfies the relation: 3.2 < R6 / f < 5; R6 is the radius of curvature of the image side surface of the third lens at the optical axis. When the above relation is satisfied, by controlling the ratio of the radius of curvature of the third lens to the effective focal length of the entire optical system within a certain range, the astigmatism of the third lens can be within a reasonable range, and it can effectively balance the astigmatism generated by the previous lenses, thereby enabling the optical system to have good imaging quality. Optionally, the value of R6 / f can be 3.201, 3.471, 3.885, 3.891, 3.935, 4.175, 4.260, 4.531, 4.750, 4.999.

[0046] In one embodiment, the optical system satisfies the relation: 1.5 < f / R7 < 2; R7 is the radius of curvature of the object side surface of the fourth lens at the optical axis. When the above relation is satisfied, by controlling the ratio of the radius of curvature of the fourth lens to the effective focal length of the entire optical system within a certain range, the astigmatism of the fourth lens can be within a reasonable range, and it can effectively balance the astigmatism generated by the previous lenses, thereby enabling the optical system to have good imaging quality. Optionally, the value of f / R7 can be 1.501, 1.587, 1.682, 1.687, 1.715, 1.784, 1.816, 1.946, 1.987, 1.999.

[0047] In one embodiment, the optical system satisfies the relation: 1 < R8 / f < 2; R8 is the radius of curvature of the image side surface of the fourth lens at the optical axis. When the above relation is satisfied, by controlling the ratio of the radius of curvature of the fourth lens to the effective focal length of the entire optical system within a certain range, the astigmatism of the fourth lens can be within a reasonable range, and it can effectively balance the astigmatism generated by the previous lenses, thereby enabling the optical system to have good imaging quality. Optionally, the value of R8 / f can be 1.001, 1.047, 1.134, 1.200, 1.334, 1.362, 1.494, 1.695, 1.882, 1.999.

[0048] In one embodiment, the optical system satisfies the relation: 0.18 < (R6 - R5) / f3 < 1.1. When the above relation is satisfied, the refractive power of the optical system is reasonably distributed, enabling the optical system to have a high aberration correction ability while maintaining miniaturization, and better manufacturability can be obtained. Optionally, the value of (R6 - R5) / f3 can be 0.181, 0.184, 0.574, 0.689, 0.743, 0.815, 0.897, 0.967, 1.071, 1.099.

[0049] In one embodiment, the optical system satisfies the relation: 1.3 < ΣCT / ΣET < 1.6; where ΣCT is the sum of the central thicknesses of the first lens to the fourth lens on the optical axis, and ΣAT is the sum of the air spaces of the first lens to the fourth lens on the optical axis. When the above relation is satisfied, sufficient air gaps can be ensured between the lenses and between the last lens and the imaging surface, which is not only beneficial to the structural design and assembly process of the lens barrel and the lenses, but also can better balance distortion; in addition, there is a larger forming and debugging process space, avoiding the risk of stray light caused by appearance problems of the lenses, and achieving a better match between the chief ray angle and the photosensitive chip. Optionally, the value of ΣCT / ΣET can be 1.301, 1.352, 1.396, 1.437, 1.466, 1.474, 1.487, 1.502, 1.575, 1.599.

[0050] In one embodiment, the optical system satisfies the relation: 1 < CT2 / CT1 < 1.7; where CT1 is the central thickness of the first lens on the optical axis, and CT2 is the central thickness of the second lens on the optical axis. When the above relation is satisfied, the central thicknesses of the first lens and the second lens on the optical axis are reasonably controlled, which is beneficial to ensuring the process requirements for the molding of two plastic lenses and is also beneficial to correcting off-axis coma. Optionally, the value of CT2 / CT1 can be 1.001, 1.054, 1.169, 1.299, 1.358, 1.464, 1.550, 1.594, 1.683, 1.699.

[0051] In one embodiment, the optical system satisfies the relation: 2.1 < CT3 / CT2 < 3.2; where CT3 is the central thickness of the third lens on the optical axis. When the above relation is satisfied, the central thicknesses of the second lens and the third lens on the optical axis are reasonably controlled, which is beneficial to ensuring the process requirements for the molding of two plastic lenses and is also beneficial to correcting off-axis coma. Optionally, the value of CT3 / CT2 can be 2.101, 2.143, 2.544, 2.740, 2.837, 2.914, 2.992, 3.043, 3.126, 3.199.

[0052] In one embodiment, the optical system satisfies the relation: 2.5 < CT3 / CT4 < 3.1; where CT4 is the central thickness of the fourth lens on the optical axis. When the above relation is satisfied, the central thicknesses of the third lens and the fourth lens on the optical axis are reasonably controlled, which is beneficial to ensuring the process requirements for the molding of two plastic lenses and is also beneficial to correcting off-axis coma. Optionally, the value of CT3 / CT4 can be 2.501, 2.526, 2.672, 2.695, 2.734, 2.896, 2.973, 3.072, 3.097, 3.099.

[0053] In one embodiment, the optical system satisfies the relation: 0.8 < CT2 / CT4 < 1.3. Satisfying the above relation and reasonably controlling the central thicknesses of the second lens and the fourth lens on the optical axis is beneficial to ensuring the processability requirements for forming two plastic lenses and is also beneficial to correcting off-axis coma. Optionally, the value of CT2 / CT4 can be 0.801, 0.830, 0.926, 0.950, 1.027, 1.063, 1.085, 1.134, 1.247, 1.299.

[0054] In one embodiment, the optical system satisfies the relation: 0.6 < (CT3 + CT4) / ΣCT < 0.71. Satisfying the above relation can achieve thickness complementarity among the lenses, basically forming a "thin - thin - thick - thin" configuration, which has a good effect of canceling aberrations such as spherical aberration, astigmatism, and chromatic aberration, and also has a good complementary effect for extreme environments such as high and low temperatures. Optionally, the value of (CT3 + CT4) / ΣCT can be 0.601, 0.623, 0.649, 0.655, 0.677, 0.685, 0.696, 0.701, 0.704, 0.709.

[0055] In one embodiment, the optical system satisfies the relation: 2.7 < CT3 / ET3 < 3.3; where ET3 is the edge thickness of the third lens at the edge. Satisfying the above relation can ensure that the thickness of the third lens is evenly distributed at different positions, reduce the influence of the thickness non-uniformity of the third lens on the imaging quality of the optical system, and also helps to improve the forming yield of the third lens. Optionally, the value of CT3 / ET3 can be 2.701, 2.794, 2.883, 2.956, 2.957, 2.968, 3.066, 3.143, 3.238, 3.299.

[0056] In one embodiment, the optical system satisfies the relation: 0.3 < SR / SD8 < 0.5; where SR is the effective semi-aperture of the aperture stop in the optical system and SD8 is the effective semi-aperture of the image side of the fourth lens. Satisfying the above relation can, on the one hand, effectively control the vignetting value of the optical system and intercept the light rays with poor imaging quality, thereby improving the resolving power of the optical system; on the other hand, it can avoid the step difference caused by the aperture difference of each lens and improve the assembly stability. Optionally, the value of SR / SD8 can be 0.301, 0.331, 0.357, 0.381, 0.403, 0.428, 0.437, 0.445, 0.478, 0.499.

[0057] In one embodiment, the optical system satisfies the relation: 1.7 < SD1 / SD2 < 1.9; where SD1 is the effective semi-aperture of the object side of the first lens, and SD2 is the effective semi-aperture of the image side of the first lens. Satisfying the above relation facilitates controlling the maximum light-passing aperture of the first lens to achieve the characteristics of a large aperture and a relatively high relative illuminance. Optionally, the value of SD1 / SD2 can be 1.701, 1.736, 1.768, 1.775, 1.782, 1.792, 1.825, 1.854, 1.878, 1.899.

[0058] In one embodiment, the optical system satisfies the relation: 1 < SD1 / ImgH < 1.1. Satisfying the above relation enables a reasonable configuration of the ratio between half of the maximum effective aperture of the object side of the first lens and half of the image height corresponding to the maximum field of view angle of the optical system, which is beneficial to reasonably controlling the size of the object side of the first lens and achieving miniaturization of the optical system. Optionally, the value of SD1 / ImgH can be 1.001, 1.014, 1.024, 1.031, 1.042, 1.049, 1.056, 1.069, 1.074, 1.099.

[0059] In one embodiment, the optical system satisfies the relation: 1.1 < SD1 / SD8 < 1.2. Satisfying the above relation is beneficial to reducing the main ray incident angle, improving the relative illuminance, and enhancing the imaging quality. Optionally, the value of SD1 / SD8 can be 1.101, 1.120, 1.137, 1.148, 1.155, 1.167, 1.168, 1.172, 1.190, 1.199.

[0060] In one embodiment, the optical system satisfies the relation: 2.7 < R6 / SD6 < 3.3; where SD6 is the effective semi-aperture of the image side of the third lens. Optionally, the value of R6 / SD6 can be 2.701, 2.786, 2.857, 2.972, 2.975, 3.070, 3.098, 3.133, 3.271, 3.299.

[0061] In a second aspect, the present invention further provides a lens module, which includes the optical system according to any one of the embodiments in the first aspect and an image sensor chip, and the image sensor chip is disposed on the image side of the optical system.

[0062] In a third aspect, the present invention further provides an electronic device, which includes a housing and the lens module according to the second aspect, and the lens module is disposed inside the housing.

[0063] First Embodiment

[0064] Please refer to Figure 1 and Figure 2, the optical system 10 of this embodiment includes, in sequence from the object side to the image side:

[0065] The first lens L1 has a negative refractive power. At the vicinity of the optical axis 101, the object side surface S1 is concave and the image side surface S2 is convex; at the vicinity of the circumference, the object side surface S1 is concave and the image side surface S2 is convex.

[0066] The second lens L2 has a negative refractive power. At the vicinity of the optical axis 101, the object side surface S3 is convex and the image side surface S4 is concave; at the vicinity of the circumference, the object side surface S3 is concave and the image side surface S4 is convex.

[0067] The third lens L3 has a positive refractive power. At the vicinity of the optical axis 101, the object side surface S5 is convex and the image side surface S6 is concave; at the vicinity of the circumference, the object side surface S5 is convex and the image side surface S6 is concave.

[0068] The fourth lens L4 has a positive refractive power. At the vicinity of the optical axis 101, the object side surface S7 is convex and the image side surface S8 is concave; at the vicinity of the circumference, the object side surface S7 is convex and the image side surface S8 is concave.

[0069] Among them, the first lens L1 to the fourth lens L4 are all made of plastic. In other embodiments, the lens materials can also all be glass, or a combination of glass and plastic, that is, some of them are plastic and the others are glass. In addition, the optical system 10 further includes a diaphragm STO, an infrared filter IR, and an imaging surface IMG. The diaphragm STO is disposed on the object side surface S3 of the second lens L2 for controlling the amount of incident light. The infrared filter IR includes an object side surface S9 and an image side surface L10, where the object side surface S9 faces the fourth lens L4. The effective pixel region of the photosensitive chip is located on the imaging surface IMG.

[0070] The infrared filter IR can be an infrared cut-off filter, which is used to filter out infrared light so that the light incident on the imaging surface IMG is visible light, and the wavelength of the visible light is 380nm - 780nm. The material of the infrared cut-off filter is glass and can be coated on the lens. Of course, in other embodiments, the infrared filter IR can also be an infrared pass filter, which is used to filter visible light and only allow infrared light to pass through, and can be used for infrared imaging, etc.

[0071] Table 1 shows the characteristic table of the optical system 10 of this embodiment. The Y radius in Table 1 is the curvature radius of the object side surface or the image side surface with the corresponding surface number at the optical axis 101. The surface number S1 and the surface number S2 are respectively the object side surface S1 and the image side surface S2 of the first lens L1. That is, in the same lens, the surface with the smaller surface number is the object side surface, and the surface with the larger surface number is the image side surface. The first value in the "thickness" parameter column of the first lens L1 is the thickness of the lens on the optical axis 101, and the second value is the distance from the image side surface of the lens to the subsequent optical surface (the object side surface of the subsequent lens or the diaphragm surface) on the optical axis 101.

[0072] Table 1

[0073]

[0074] Among them, as shown in Table 1, f is the effective focal length of the optical system 10, FNO is the f-number of the optical system 10, FOV is the maximum field of view angle of the optical system 10, TTL is the distance from the object side surface S1 of the first lens L1 to the imaging surface IMG on the optical axis 101, and ImgH is half of the image height corresponding to the maximum field of view angle of the optical system.

[0075] In this embodiment, the first lens L1 to the fourth lens L4 are all aspherical lenses. The surface profile x of the aspherical surface can be defined by, but not limited to, the following aspherical formula:

[0076]

[0077] Among them, x is the distance from the corresponding point on the aspherical surface to the plane tangent to the vertex on the axis, h is the distance from the corresponding point on the aspherical surface to the optical axis 101, c is the curvature of the aspherical vertex, k is the conic coefficient, and Ai is the coefficient corresponding to the i-th high-order term in the aspherical surface profile formula. Table 1b gives the high-order term coefficients k, A4, A6, A8, A10, A12, A14, A16, A18, A20, A22, A24, A26, A28, A30 of the aspherical mirror surface that can be used in the first embodiment.

[0078] Table 2

[0079]

[0080]

[0081] Figure 2 In (a), it shows the longitudinal spherical aberration curves of the optical system of the first embodiment at wavelengths of 960.0000 nm, 940.000 nm, and 920.0000 nm. Among them, the abscissa along the X-axis direction represents the focus shift, with the unit of mm, and the ordinate along the Y-axis direction represents the normalized field of view. The longitudinal spherical aberration curve represents the deviation of the convergence points of light rays with different wavelengths after passing through each lens of the optical system. From Figure 2 As can be seen from (a), the spherical aberration value of the optical system in the first embodiment is better, indicating that the imaging quality of the optical system in this embodiment is better.

[0082] Figure 2Figure (b) also shows the astigmatism curve of the optical system of the first embodiment at a wavelength of 940.000 nm. Among them, the abscissa along the X-axis direction represents the focus shift, with the unit of mm, and the ordinate along the Y-axis direction represents the semi-image height, with the unit of mm. T in the astigmatism curve represents the curvature of the imaging surface IMG in the meridional direction, and S represents the curvature of the imaging surface IMG in the sagittal direction. From Figure 2 Figure (b), it can be seen that the astigmatism of the optical system is well compensated.

[0083] Figure 2 Figure (c) also shows the distortion curve of the optical system of the first embodiment at a wavelength of 940.000 nm. Among them, the abscissa along the X-axis direction represents the distortion, and the ordinate along the Y-axis direction represents the semi-image height, with the unit of mm. The distortion curve represents the distortion magnitude values corresponding to different field angles. From Figure 2 Figure (c), it can be seen that at a wavelength of 940.000 nm, the distortion of the optical system is well corrected.

[0084] From Figure 2 Figures (a), (b) and (c), it can be seen that the optical system of this embodiment has small aberrations and good imaging quality, and has good imaging performance.

[0085] Second Embodiment

[0086] Please refer to Figure 3 and Figure 4 , the difference in the structure of the optical system 10 of this embodiment from that of the first embodiment is that the image side surface S2 of the first lens L1 at the optical axis is concave; the object side surface S3 of the second lens L2 at the optical axis is concave, and the image side surface S4 at the circumference is concave; the object side surface S7 of the fourth lens L4 at the circumference is concave, and the image side surface S8 at the circumference is convex.

[0087] Table 3 shows the characteristic table of the optical system 10 of this embodiment. The meanings of all parameters are the same as those of the first embodiment and will not be elaborated here.

[0088] Table 3

[0089]

[0090] Table 3 shows the high-order term coefficients of the aspherical mirror surfaces that can be used in the second embodiment. Among them, each aspherical surface type can be defined by the formula given in the first embodiment.

[0091] Table 4

[0092]

[0093] Figure 4Shows the longitudinal spherical aberration curve, astigmatism curve, and distortion curve of the optical system of the second embodiment. From Figure 4 the aberration diagrams in, it can be seen that the longitudinal spherical aberration, field curvature, and distortion of the optical system are all well controlled, so that the optical system of this embodiment has good imaging quality.

[0094] The third embodiment

[0095] Please refer to Figure 5 and Figure 6 In this embodiment, the structure of the optical system 10 is different from that of the first embodiment in that the image side S2 of the first lens L1 at the optical axis is concave; the object side S3 of the second lens L2 at the optical axis is concave, and the image side S4 at the circumference is concave; the object side S7 of the fourth lens L4 at the circumference is concave, and the image side S8 at the circumference is convex.

[0096] Table 5 shows the characteristic table of the optical system 10 of this embodiment. The meanings of the parameters are the same as those of the first embodiment and will not be elaborated here.

[0097] Table 5

[0098]

[0099] Table 6 shows the higher-order term coefficients of the aspherical mirror surfaces that can be used in the third embodiment. Among them, the aspherical surface types can be defined by the formulas given in the first embodiment.

[0100] Table 6

[0101]

[0102]

[0103] Figure 6 Shows the longitudinal spherical aberration curve, astigmatism curve, and distortion curve of the optical system of the third embodiment. From Figure 6 the aberration diagrams in, it can be seen that the longitudinal spherical aberration, field curvature, and distortion of the optical system are all well controlled, so that the optical system of this embodiment has good imaging quality.

[0104] The fourth embodiment

[0105] Please refer to Figure 7 and Figure 8, the difference in the structure of the optical system 10 of this embodiment from that of the first embodiment lies in that the image side surface S2 of the first lens L1 at the optical axis is concave; the second lens L2 has a positive refractive power, the object side surface S3 at the optical axis is concave, the image side surface S4 at the optical axis is convex, the object side surface S3 at the circumference is convex, and the image side surface S4 at the circumference is concave; the object side surface S7 of the fourth lens L4 at the circumference is concave, and the image side surface S8 at the circumference is convex.

[0106] Table 7 shows the characteristic table of the optical system 10 of this embodiment. The meanings of all parameters are the same as those of the first embodiment and will not be elaborated here.

[0107] Table 7

[0108]

[0109] Table 8 shows the higher-order term coefficients of the aspherical mirror surfaces that can be used in the fourth embodiment. Among them, each aspherical surface type can be defined by the formula given in the first embodiment.

[0110] Table 8

[0111]

[0112] Figure 8 shows the longitudinal spherical aberration curve graph, astigmatism curve graph, and distortion curve graph of the optical system of the fourth embodiment. From Figure 8 the aberration graph, it can be seen that the longitudinal spherical aberration, field curvature, and distortion of the optical system are all well controlled, so the optical system of this embodiment has good imaging quality.

[0113] The Fifth Embodiment

[0114] Please refer to Figure 9 and Figure 10 , the difference in the structure of the optical system 10 of this embodiment from that of the first embodiment lies in that the image side surface S2 of the first lens L1 at the optical axis is concave; the object side surface S3 of the second lens L2 at the optical axis is concave; the object side surface S7 of the fourth lens L4 at the circumference is concave, and the image side surface S8 at the circumference is convex.

[0115] Table 9 shows the characteristic table of the optical system 10 of this embodiment. The meanings of all parameters are the same as those of the first embodiment and will not be elaborated here.

[0116] Table 9

[0117]

[0118] Table 10 shows the higher-order term coefficients of the aspherical mirror surfaces that can be used in the fifth embodiment. Among them, each aspherical surface type can be defined by the formula given in the first embodiment.

[0119] Table 10

[0120]

[0121]

[0122] Figure 10 Shows the longitudinal spherical aberration curve, astigmatism curve and distortion curve of the optical system of the fifth embodiment. From Figure 10 the aberration diagrams, it can be seen that the longitudinal spherical aberration, field curvature and distortion of the optical system are all well controlled, so the optical system of this embodiment has good imaging quality.

[0123] Sixth Embodiment

[0124] Please refer to Figure 11 and Figure 12 , the difference between the structure of the optical system 10 of this embodiment and that of the first embodiment is that the image side S2 of the first lens L1 at the optical axis is concave; the object side S3 of the second lens L2 at the optical axis is concave; the object side S7 of the fourth lens L4 at the circumference is concave, and the image side S8 at the circumference is convex.

[0125] Table 11 shows the characteristic table of the optical system 10 of this embodiment, and the meanings of the parameters are the same as those of the first embodiment, so they will not be elaborated here.

[0126] Table 11

[0127]

[0128] Table 12 shows the higher-order term coefficients of the aspherical mirrors that can be used in the sixth embodiment. Among them, the aspherical surface types can be defined by the formulas given in the first embodiment.

[0129] Table 12

[0130]

[0131] Figure 12 Shows the longitudinal spherical aberration curve, astigmatism curve and distortion curve of the optical system of the sixth embodiment. From Figure 12 the aberration diagrams, it can be seen that the longitudinal spherical aberration, field curvature and distortion of the optical system are all well controlled, so the optical system of this embodiment has good imaging quality.

[0132] Seventh Embodiment

[0133] Please refer to Figure 13 and Figure 14 , the difference between the structure of the optical system 10 of this embodiment and that of the first embodiment is that the object side S3 of the second lens L2 at the optical axis is concave.

[0134] Table 13 shows the characteristic table of the optical system 10 of this embodiment. The meanings of the parameters are the same as those in the first embodiment, and will not be elaborated here.

[0135] Table 13

[0136]

[0137] Table 14 shows the higher-order term coefficients of the aspherical mirrors that can be used in the seventh embodiment. Among them, the aspherical surface types can be defined by the formulas given in the first embodiment.

[0138] Table 14

[0139]

[0140]

[0141] Figure 14 shows the longitudinal spherical aberration curve graph, astigmatism curve graph, and distortion curve graph of the optical system of the seventh embodiment. From Figure 14 the aberration graph, it can be seen that the longitudinal spherical aberration, field curvature, and distortion of the optical system are all well controlled, so that the optical system of this embodiment has good imaging quality.

[0142] Table 15 shows the values of various relational expressions in the optical system 10 of the first embodiment to the seventh embodiment. Among them, E1 in Table 15 is the first embodiment, E2 is the second embodiment, and so on to E7 which is the seventh embodiment.

[0143] Table 15

[0144]

[0145]

[0146] By satisfying the above formulas, the refractive power distribution can be made uniform and reasonable, the aberration is easy to correct, and the image quality is good. The optical system 10 provided by the above embodiments can meet the characteristics of a large aperture and a large field of view angle. The optical system 10 can ensure sufficient light intake and high-definition imaging effects on the basis of ensuring a compact and stable structure.

[0147] Reference Figure 15, an embodiment of the present invention further provides a lens module 20. The lens module 20 includes the optical system 10 in any of the foregoing embodiments and an image sensor chip 201. The image sensor chip 201 is disposed on the image side of the optical system 10, and the two can be fixed by a bracket. The image sensor chip 201 can be a CCD sensor (Charge Coupled Device) or a CMOS sensor (Complementary Metal Oxide Semiconductor). Generally, during assembly, the imaging plane IMG of the optical system 10 overlaps with the photosensitive surface of the image sensor chip 201. By adopting the above optical system 10, the lens module 20 can meet the requirements of a large aperture and a large field of view, while ensuring that the lens module 20 has the characteristics of a compact and stable structure and a small size.

[0148] Reference Figure 16 , an embodiment of the present invention further provides an electronic device 30. The electronic device 30 includes a housing 310 and the lens module 20 in the foregoing embodiment. The lens module 20 is installed in the housing 310. The electronic device 30 can be, but is not limited to, a vehicle lens, a VR (Virtual Reality) glasses, a smart phone, a smart watch, an e-book reader, a tablet computer, a biometric device (such as a fingerprint recognition device or a pupil recognition device, etc.), a PDA (Personal Digital Assistant), etc. Since the above lens module 20 can meet the characteristics of a large aperture and clear imaging, when the above lens module 20 is adopted, the electronic device 30 can meet the requirements of a large aperture and a large field of view, while ensuring the miniaturization of the lens module 20 and reserving space for other components in the electronic device.

[0149] The above-disclosed are only some preferred embodiments of the present invention. Of course, the scope of the rights of the present invention cannot be limited thereby. Those of ordinary skill in the art can understand all or part of the processes of implementing the above embodiments, and the equivalent changes made according to the claims of the present invention still fall within the scope covered by the present invention.

Claims

1. An optical system, characterized in that, The number of lenses with refractive power is four, which successively include along the optical axis direction from the object side to the image side: A first lens with negative refractive power, the object side is concave near the circumference, and the image side is convex near the circumference; A second lens with refractive power; A third lens with positive refractive power, the object side is convex near the optical axis, and the image side is concave near the optical axis; A fourth lens with positive refractive power, the object side is convex near the optical axis, and the image side is concave near the optical axis; The optical system satisfies the relationships: 0.9 < FNO < 1.3, 160° < FOV < 177°; where, FNO is the f-number of the optical system, and FOV is the maximum field of view angle of the optical system.

2. The optical system according to claim 1, wherein The optical system satisfies the relationship: 140° < FOV / FNO < 180°.

3. The optical system according to claim 1, wherein The optical system satisfies the relationships: 2.6 < TTL / ImgH < 2.8; and / or, 1.7 < ImgH / BL < 2.2; and / or, 1.5 < ImgH / EPD < 2.2; where, TTL is the distance from the object side of the first lens to the imaging plane on the optical axis, ImgH is half of the image height corresponding to the maximum field of view angle of the optical system, BL is the minimum distance from the image side of the fourth lens to the imaging plane, and EPD is the entrance pupil diameter of the optical system.

4. The optical system according to claim 1, characterized in that, The optical system satisfies the relationships: -2.9 < f1 / f < -2; and / or, 5 < |f2| / f < 40; and / or, 2.5 < f3 / f < 9; and / or 1.1 < f4 / f < 1.4; where, f is the effective focal length of the optical system, f1 is the effective focal length of the first lens, f2 is the effective focal length of the second lens, f3 is the effective focal length of the third lens, and f4 is the effective focal length of the fourth lens.

5. The optical system according to claim 1, characterized in that, The optical system satisfies the relationships: -1.7 < R1 / f < -1.2; and / or, 6 < |R2| / f < 28; and / or, 5 < |R3| / f < 20; and / or, 2.7 < |R4| / f < 40; and / or, 1.2 < R5 / f < 2.8; and / or, 3.2 < R6 / f < 5; and / or, 1.5 < f / R7 < 2; and / or, 1 < R8 / f < 2; where, f is the effective focal length of the optical system, R1 is the curvature radius of the object side of the first lens at the optical axis; R2 is the curvature radius of the image side of the first lens at the optical axis, R3 is the curvature radius of the object side of the second lens at the optical axis; R4 is the curvature radius of the image side of the second lens at the optical axis, R5 is the curvature radius of the object side of the third lens at the optical axis; R6 is the curvature radius of the image side of the third lens at the optical axis, R7 is the curvature radius of the object side of the fourth lens at the optical axis; R8 is the curvature radius of the image side of the fourth lens at the optical axis.

6. The optical system according to claim 1, wherein, The optical system satisfies the relationship: 0.18 < (R6 - R5) / f3 < 1.1; where, R5 is the curvature radius of the object side of the third lens at the optical axis; R6 is the curvature radius of the image side of the third lens at the optical axis, and f3 is the effective focal length of the third lens.

7. The optical system according to claim 1, characterized in that, The optical system satisfies the relationships: 1.3 < ΣCT / ΣET < 1.6; and / or, 1 < CT2 / CT1 < 1.7; and / or, 2.1 < CT3 / CT2 < 3.2; and / or, 2.5 < CT3 / CT4 < 3.1; and / or, 0.8 < CT2 / CT4 < 1.3; and / or, 0.6 < (CT3 + CT4) / ΣCT < 0.71; and / or, 2.7 < CT3 / ET3 < 3.3; where ΣCT is the sum of the central thicknesses of the first lens to the fourth lens on the optical axis, ΣAT is the sum of the air spacings of the first lens to the fourth lens on the optical axis, CT1 is the central thickness of the first lens on the optical axis, CT2 is the central thickness of the second lens on the optical axis, CT3 is the central thickness of the third lens on the optical axis, CT4 is the central thickness of the fourth lens on the optical axis, and ET3 is the edge thickness of the third lens at the edge.

8. The optical system according to claim 1, characterized in that, The optical system satisfies the relationships: 0.3 < SR / SD8 < 0.5; and / or, 1.7 < SD1 / SD2 < 1.9; and / or, 1 < SD1 / ImgH < 1.1; and / or, 1.1 < SD1 / SD8 < 1.2; and / or, 2.7 < R6 / SD6 < 3.3; where SR is the effective semi-aperture of the diaphragm in the optical system, SD8 is the effective semi-aperture of the image side of the fourth lens, SD1 is the effective semi-aperture of the object side of the first lens, SD2 is the effective semi-aperture of the image side of the first lens, ImgH is half of the image height corresponding to the maximum field of view angle of the optical system, R6 is the radius of curvature of the image side of the third lens on the optical axis, and SD6 is the effective semi-aperture of the image side of the third lens.

9. A lens module, characterized in that, Comprising the optical system according to any one of claims 1 to 8 and a photosensitive chip, the photosensitive chip is disposed on the image side of the optical system.

10. An electronic device, characterized in that, The electronic device includes a housing and the lens module according to claim 9, the lens module is disposed within the housing.

Images