CN116819732B

CN116819732B - Optical system, camera module and electronic equipment

Info

Publication number: CN116819732B
Application number: CN202311092465.XA
Authority: CN
Inventors: 山﨑
Original assignee: Jiangxi Oufei Optics Co ltd
Current assignee: Jiangxi Oufei Optics Co ltd
Priority date: 2023-08-29
Filing date: 2023-08-29
Publication date: 2024-01-09
Anticipated expiration: 2043-08-29
Also published as: CN116819732A

Abstract

An optical system, an image capturing module and an electronic device, wherein the optical system has four lenses with refractive power, and the optical system sequentially comprises from an object side to an image side along an optical axis: a first lens element with negative refractive power and a second, third and fourth lens elements with positive refractive power; the object side surface of the first lens element, the object side surface and the image side surface of the second lens element, the image side surface of the third lens element and the object side surface of the fourth lens element are convex at a paraxial region, and the image side surface of the first lens element and the image side surface of the fourth lens element are concave at a paraxial region.

Description

Optical system, camera module and electronic equipment

Technical Field

The invention belongs to the technical field of optical imaging, and particularly relates to an optical system, a camera module and electronic equipment.

Background

In order to improve the recognition capability of an optical system in the automatic driving technology to the environment, the requirement of the optical system for high-precision recognition of objects in a large range is also increasing. However, being able to meet the requirement of high-precision imaging in a wide range generally means that the structure of the optical system is more complex, which eventually leads to an increase in the size and overall length of the imaging module, and is difficult to be applied to light and thin electronic products, so how to achieve miniaturization and good imaging effect of the optical system becomes one of the problems that must be solved in the industry.

Disclosure of Invention

The invention aims to provide an optical system, an imaging module and electronic equipment, which solve the problem that the optical system meets the requirements of miniaturization and good imaging effect.

In order to achieve the purpose of the invention, the invention provides the following technical scheme:

in a first aspect, the present invention provides an optical system, comprising, in order from an object side to an image side along an optical axis: a first lens element with negative refractive power having a convex object-side surface at a paraxial region and a concave image-side surface at a paraxial region; a second lens element with positive refractive power having a convex object-side surface and a convex image-side surface at a paraxial region; a third lens element with positive refractive power having a convex image-side surface at a paraxial region; the fourth lens element with positive refractive power has a convex object-side surface at a paraxial region and a concave image-side surface at a paraxial region.

The optical system satisfies the relation: 0.8< f3/f4<2; wherein f3 is an effective focal length of the third lens, and f4 is an effective focal length of the fourth lens.

The first lens element with negative refractive power has a convex object-side surface at a paraxial region, and a concave image-side surface at a paraxial region, so as to facilitate compression of incident light rays at a large angle and improve refractive power of the first lens element; the second lens element with positive refractive power has convex object-side and image-side surfaces at paraxial regions, which is beneficial to enhancing the positive refractive power of the second lens element and further provides a reasonable light incident angle for introducing marginal light; the third lens element with positive refractive power has a convex image-side surface at a paraxial region, so that the focal length of the third lens element can be increased, the refractive power can be moved backward, the total optical length can be reduced, the tolerance sensitivity can be reduced, and distortion, astigmatism and field curvature can be corrected, thereby meeting the requirements of miniaturization of an optical system, high image quality and matching angle of a photosensitive chip; the fourth lens element with positive refractive power has a convex object-side surface at a paraxial region and a concave image-side surface at a paraxial region, so that the total length of the optical system is effectively shortened, and astigmatism and aberration of the optical system are corrected to achieve miniaturization.

The optical system satisfies the relation, so that the ratio of the effective focal length of the third lens to the effective focal length of the fourth lens is reasonably configured, the refractive power distribution between the lenses is further balanced, the aberration generated by the third lens and the fourth lens is mutually corrected, the aberration generated by the first lens and the second lens is corrected, the aberration correction of the optical system is enhanced, the imaging quality of the optical system is improved, and meanwhile, the size compression is facilitated, so that the optical system is miniaturized.

In one embodiment, the optical system satisfies the relationship: -1.8< f1/f < -1.5; wherein f1 is an effective focal length of the first lens, and f is an effective focal length of the optical system. By making the optical system satisfy the above relation, it is beneficial to reasonably distributing the refractive power of the first lens, providing negative refractive power for the optical system, and the optical system has a larger field angle in the same size compared with a common optical system; meanwhile, the spherical aberration of the optical system is reduced, and the definition of the imaging surface is improved.

In one embodiment, the optical system satisfies the relationship: 3< f2/f <6; wherein f2 is the effective focal length of the second lens, and f is the effective focal length of the optical system. The optical system meets the relational expression, so that the refractive power of the second lens is reasonably distributed, positive refractive power is provided for the optical system, spherical aberration of the optical system is reduced, and definition of an imaging surface is improved.

In one embodiment, the optical system satisfies the relationship: 2< f3/f <5; wherein f3 is an effective focal length of the third lens, and f is an effective focal length of the optical system. The optical system satisfies the relational expression, so that the refractive power of the third lens is reasonably distributed, positive refractive power is provided for the optical system, and the characteristics of reducing the spherical aberration of the optical system and improving the definition of an imaging surface are enhanced.

In one embodiment, the optical system satisfies the relationship: 2.3< f4/f <3.7; wherein f4 is an effective focal length of the fourth lens, and f is an effective focal length of the optical system. The optical system meets the relation, so that the refractive power of the fourth lens is reasonably distributed, positive refractive power is provided for the optical system, spherical aberration of the optical system is reduced, and definition of an imaging surface is improved; meanwhile, the optical system has a longer optical back focus, so that the optical system has enough focusing positions and a space for placing the optical filter is reserved.

In one embodiment, the optical system satisfies the relationship: 40deg/mm < FOV/f <60deg/mm; wherein FOV is the maximum field angle of the optical system and f is the effective focal length of the optical system. The optical system meets the relation, so that the maximum view angle of the optical system and the effective focal length of the optical system are controlled within a reasonable range, the view finding area of a picture is effectively improved, the optical system has a larger view angle, and a larger monitoring area can be provided when the optical system is applied to a car; meanwhile, the method is also beneficial to properly reducing the effective focal length of the optical system, shortening the total length of the optical system and realizing the miniaturization design. In addition, by controlling the ratio of the maximum field angle of the optical system to the effective focal length of the optical system, the optical system can also have smaller deflection angle of emergent rays, and the problem of dark angles at the edges of the optical system is relieved.

In one embodiment, the optical system satisfies the relationship: 0.2< Ta/Tb <0.4; wherein Ta is a distance between the object side surface of the first lens element and the image side surface of the second lens element on the optical axis, and Tb is a distance between the image side surface of the second lens element and the imaging surface of the optical system on the optical axis. The optical system meets the relation, so that the ratio of the distance from the object side surface of the first lens to the image side surface of the second lens on the optical axis to the distance from the image side surface of the second lens to the imaging surface of the optical system on the optical axis is reasonably configured, the incidence angle of light reaching the imaging surface in the optical system is restrained, and the risk of dark angle is reduced; meanwhile, the total length of the optical system is also shortened, and the miniaturization design is realized.

In one embodiment, the optical system further includes a diaphragm, the diaphragm being located between the second lens and the third lens, the optical system satisfying the relation: 0.25< (Db-Da)/f <0.65; wherein Da is the distance between the image side surface of the second lens and the diaphragm on the optical axis, db is the distance between the diaphragm and the object side surface of the third lens on the optical axis, and f is the effective focal length of the optical system. The optical system is enabled to meet the relation, so that the reasonable configuration of the ratio of the difference between the distance from the object side surface of the diaphragm to the third lens on the optical axis and the distance from the image side surface of the second lens to the diaphragm on the optical axis to the effective focal length of the optical system is facilitated, and the diaphragm is reasonably arranged in the optical system, so that the incident angle of the marginal view field light ray when entering the optical system can be effectively controlled, the light entering quantity of the optical system is regulated, the relative brightness of the marginal view field is improved, the imaging definition is improved, and the imaging quality is further improved.

In one embodiment, the optical system satisfies the relationship: 1< SD11/SD42<1.4; wherein SD11 is the maximum effective aperture of the object side surface of the first lens element, and SD42 is the maximum effective aperture of the image side surface of the fourth lens element. The optical system meets the relation, so that the ratio of the maximum effective caliber of the object side surface of the first lens to the maximum effective caliber of the image side surface of the fourth lens is reasonably configured, the outer diameter size of the lens group in the optical system is further controlled, the thickness of the optical system in the radial direction is reduced, and the requirement of miniaturization of the optical system is met.

In one embodiment, the optical system satisfies the relationship: 4< R11/R12<10; wherein R11 is a radius of curvature of the object side surface of the first lens element at the optical axis, and R12 is a radius of curvature of the image side surface of the first lens element at the optical axis. The optical system meets the relation, so that the ratio of the curvature radius of the object side surface of the first lens at the optical axis to the curvature radius of the image side surface of the first lens at the optical axis is reasonably configured, the shape of the first lens is controlled, the spherical aberration, chromatic aberration and field curvature of the optical system are comprehensively balanced, the risk of generating ghost images is reduced, the resolving power of the optical system is improved, and meanwhile, the processing difficulty of the first lens is reduced. Below the lower limit of the relation, the radius of curvature of the object side surface of the first lens element at the optical axis is too small relative to the radius of curvature of the image side surface of the first lens element at the optical axis, so that the object side surface of the first lens element is excessively bent, and the negative refractive power of the first lens element is insufficient, which is not beneficial to aberration correction of the optical system; exceeding the upper limit of the relation, the radius of curvature of the object side surface of the first lens element at the optical axis is too large relative to the radius of curvature of the image side surface of the first lens element at the optical axis, so that the object side surface of the first lens element is excessively flat, the negative refractive power of the first lens element is excessively high, the light rays of the marginal view field are excessively dispersed, and the distortion of the light ray system is further increased.

In one embodiment, the optical system satisfies the relationship: 5< R42/R41<50; wherein R41 is a radius of curvature of the object side surface of the fourth lens element at the optical axis, and R42 is a radius of curvature of the image side surface of the fourth lens element at the optical axis. The optical system meets the relation, so that the ratio of the curvature radius of the image side surface of the fourth lens to the curvature radius of the object side surface of the fourth lens at the optical axis is reasonably configured, the shape of the fourth lens is controlled, the spherical aberration, chromatic aberration and field curvature of the optical system are comprehensively balanced, the risk of generating ghost images is reduced, the resolving power of the optical system is improved, and meanwhile, the processing difficulty of the fourth lens is reduced.

In one embodiment, the optical system satisfies the relationship: 120deg < fov <130deg; wherein FOV is the maximum field angle of the optical system. The optical system meets the relation, so that the maximum field angle of the optical system is controlled within a reasonable range, the view finding area of a picture is effectively improved, and the optical system has a larger field angle.

In one embodiment, the optical system satisfies the relationship: 1.2< FNO <1.4; wherein FNO is the f-number of the optical system. The optical system can meet the relation, so that the optical system is favorable for having smaller f-number, and the relative brightness of the edge view field is improved, the imaging definition is improved, and the imaging quality is further improved by inhibiting the incident angle of light reaching the imaging surface.

In a second aspect, the present invention further provides an image capturing module, where the image capturing module includes a photosensitive chip and the optical system according to any one of the embodiments of the first aspect, and the photosensitive chip is disposed on an image side of the optical system. The photosensitive surface of the photosensitive chip is positioned on the imaging surface of the optical system, and light rays of objects incident on the photosensitive surface through the lens can be converted into electric signals of images. The photo-sensing chip may be a complementary metal oxide semiconductor (Complementary Metal Oxide Semiconductor, CMOS) or a Charge-coupled Device (CCD). The camera module can be an imaging module integrated on the electronic equipment or an independent lens. By adding the optical system provided by the invention into the image pickup module, the image pickup module can meet miniaturization and has good imaging effect by reasonably designing the surface type and the refractive power of each lens in the optical system.

In a third aspect, the present invention further provides an electronic device, where the electronic device includes a housing and the camera module set in the second aspect, and the camera module set is disposed in the housing. Such electronic devices include, but are not limited to, automobiles, monitors, smart phones, computers, smart watches, and the like. By adding the camera module provided by the invention into the electronic equipment, the electronic equipment can be miniaturized and has good imaging effect.

Drawings

In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings which are used in the description of the embodiments or the prior art will be briefly described, it being obvious that the drawings in the description below are only some embodiments of the invention, and that other drawings can be obtained from these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic structural view of an optical system of a first embodiment;

fig. 2 shows a longitudinal spherical aberration curve, an astigmatic curve, and a distortion curve of the optical system of the first embodiment;

fig. 3 is a schematic structural view of an optical system of a second embodiment;

fig. 4 shows a longitudinal spherical aberration curve, an astigmatic curve, and a distortion curve of the optical system of the second embodiment;

fig. 5 is a schematic structural view of an optical system of a third embodiment;

fig. 6 shows a longitudinal spherical aberration curve, an astigmatic curve, and a distortion curve of the optical system of the third embodiment;

fig. 7 is a schematic structural view of an optical system of a fourth embodiment;

fig. 8 shows a longitudinal spherical aberration curve, an astigmatic curve, and a distortion curve of the optical system of the fourth embodiment;

Fig. 9 is a schematic structural view of an optical system of the fifth embodiment;

fig. 10 shows a longitudinal spherical aberration curve, an astigmatic curve, and a distortion curve of the optical system of the fifth embodiment;

FIG. 11 is a schematic diagram showing the structure of a camera module according to an embodiment of the present invention;

fig. 12 is a schematic structural diagram of an electronic device in an embodiment of the invention.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, are intended to fall within the scope of the present invention.

In a first aspect, the present invention provides an optical system, comprising, in order from an object side to an image side along an optical axis: the first lens element with negative refractive power has a convex object-side surface at a paraxial region and a concave image-side surface at a paraxial region; the second lens element with positive refractive power has a convex object-side surface and a convex image-side surface at a paraxial region; the third lens element with positive refractive power has a convex image-side surface at a paraxial region; the fourth lens element with positive refractive power has a convex object-side surface at a paraxial region and a concave image-side surface at a paraxial region.

The optical system satisfies the relation: 0.8< f3/f4<2; wherein f3 is the effective focal length of the third lens, and f4 is the effective focal length of the fourth lens. Specifically, the value of f3/f4 may be 1.182, 1.634, 1.582, 1.744, 0.914, 0.803, 1.056, 1.975, etc.

By making the optical system satisfy the relation: the ratio of the effective focal length of the third lens to the effective focal length of the fourth lens is reasonably configured, and the refractive power distribution between the lenses is further balanced, so that the aberration generated by the third lens and the fourth lens is mutually corrected, the aberration generated by the first lens and the second lens is corrected, the aberration correction of the optical system is enhanced, the imaging quality of the optical system is improved, and meanwhile, the size compression is facilitated, and the optical system is miniaturized.

In one embodiment, the optical system satisfies the relationship: -1.8< f1/f < -1.5; wherein f1 is the effective focal length of the first lens, and f is the effective focal length of the optical system. Specifically, the value of f1/f may be-1.738, -1.600, -1.577, -1.581, -1.574, -1.503, -1.760, -1.654, etc.

By making the optical system satisfy the above relation, it is beneficial to reasonably distributing the refractive power of the first lens, providing negative refractive power for the optical system, and the optical system has a larger field angle in the same size compared with a common optical system; meanwhile, the spherical aberration of the optical system is reduced, and the definition of the imaging surface is improved.

In one embodiment, the optical system satisfies the relationship: 3< f2/f <6; wherein f2 is the effective focal length of the second lens, and f is the effective focal length of the optical system. Specifically, the f2/f may have values of 4.243, 3.201, 3.149, 3.526, 5.196, 3.013, 5.961, 4.974, etc.

The optical system meets the relational expression, so that the refractive power of the second lens is reasonably distributed, positive refractive power is provided for the optical system, spherical aberration of the optical system is reduced, and definition of an imaging surface is improved.

In one embodiment, the optical system satisfies the relationship: 2< f3/f <5; wherein f3 is the effective focal length of the third lens, and f is the effective focal length of the optical system. Specifically, the value of f3/f may be 3.088, 4.192, 4.116, 4.944, 2.935, 2.073, 3.638, 4.529, etc.

The optical system satisfies the relational expression, so that the refractive power of the third lens is reasonably distributed, positive refractive power is provided for the optical system, and the characteristics of reducing the spherical aberration of the optical system and improving the definition of an imaging surface are enhanced.

In one embodiment, the optical system satisfies the relationship: 2.3< f4/f <3.7; wherein f4 is the effective focal length of the fourth lens, and f is the effective focal length of the optical system. Specifically, the value of f4/f may be 2.614, 2.565, 2.602, 2.835, 3.211, 2.306, 3.649, 3.058, etc.

The optical system meets the relation, so that the refractive power of the fourth lens is reasonably distributed, positive refractive power is provided for the optical system, spherical aberration of the optical system is reduced, and definition of an imaging surface is improved; meanwhile, the optical system has a longer optical back focus, so that the optical system has enough focusing positions and a space for placing the optical filter is reserved.

In one embodiment, the optical system satisfies the relationship: 40deg/mm < FOV/f <60deg/mm; where FOV is the maximum field angle of the optical system and f is the effective focal length of the optical system. Specifically, the value of FOV/f may be 40.702 deg/mm, 40.344deg/mm, 40.357deg/mm, 53.517deg/mm, 55.244deg/mm, 46.963deg/mm, 51.698 deg/mm, 59.874 deg/mm, etc.

The optical system meets the relation, so that the maximum view angle of the optical system and the effective focal length of the optical system are controlled within a reasonable range, the view finding area of a picture is effectively improved, the optical system has a larger view angle, and a larger monitoring area can be provided when the optical system is applied to a car; meanwhile, the method is also beneficial to properly reducing the effective focal length of the optical system, shortening the total length of the optical system and realizing the miniaturization design. In addition, by controlling the ratio of the maximum field angle of the optical system to the effective focal length of the optical system, the optical system can also have smaller deflection angle of emergent rays, and the problem of dark angles at the edges of the optical system is relieved.

In one embodiment, the optical system satisfies the relationship: 0.2< Ta/Tb <0.4; wherein Ta is a distance between the object side surface of the first lens element and the image side surface of the second lens element on the optical axis, and Tb is a distance between the image side surface of the second lens element and the imaging surface of the optical system on the optical axis. Specifically, the Ta/Tb values may be 0.243, 0.256, 0.346, 0.295, 0.201, 0.217, 0.388, 0.302, etc.

The optical system meets the relation, so that the ratio of the distance from the object side surface of the first lens to the image side surface of the second lens on the optical axis to the distance from the image side surface of the second lens to the imaging surface of the optical system on the optical axis is reasonably configured, the incidence angle of light reaching the imaging surface in the optical system is restrained, and the risk of dark angle is reduced; meanwhile, the total length of the optical system is also shortened, and the miniaturization design is realized.

In one embodiment, the optical system further comprises a diaphragm, the diaphragm being located between the second lens and the third lens, the optical system satisfying the relation: 0.25< (Db-Da)/f <0.65; wherein Da is the distance from the image side surface of the second lens element to the stop on the optical axis, db is the distance from the stop to the object side surface of the third lens element on the optical axis, and f is the effective focal length of the optical system. Specifically, the value of (Db-Da)/f may be 0.299, 0.321, 0.333, 0.535, 0.520, 0.253, 0.645, 0.462, or the like.

The optical system is enabled to meet the relation, so that the reasonable configuration of the ratio of the difference between the distance from the object side surface of the diaphragm to the third lens on the optical axis and the distance from the image side surface of the second lens to the diaphragm on the optical axis to the effective focal length of the optical system is facilitated, and the diaphragm is reasonably arranged in the optical system, so that the incident angle of the marginal view field light ray when entering the optical system can be effectively controlled, the light entering quantity of the optical system is regulated, the relative brightness of the marginal view field is improved, the imaging definition is improved, and the imaging quality is further improved.

In one embodiment, the optical system satisfies the relationship: 1< SD11/SD42<1.4; wherein SD11 is the maximum effective aperture of the object side surface of the first lens element, and SD42 is the maximum effective aperture of the image side surface of the fourth lens element. Specifically, the SD11/SD42 values may be 1.017, 1.001, 1.006, 1.336, 1.340, 1.256, 1.389, 1.296, etc.

The optical system meets the relation, so that the ratio of the maximum effective caliber of the object side surface of the first lens to the maximum effective caliber of the image side surface of the fourth lens is reasonably configured, the outer diameter size of the lens group in the optical system is further controlled, the thickness of the optical system in the radial direction is reduced, and the requirement of miniaturization of the optical system is met.

In one embodiment, the optical system satisfies the relationship: 4< R11/R12<10; wherein R11 is a radius of curvature of the object side surface of the first lens element at the optical axis, and R12 is a radius of curvature of the image side surface of the first lens element at the optical axis. Specifically, the values of R11/R12 may be 4.717, 4.472, 4.520, 9.061, 6.497, 7.826, 5.836, 8.142, etc.

The optical system meets the relation, so that the ratio of the curvature radius of the object side surface of the first lens at the optical axis to the curvature radius of the image side surface of the first lens at the optical axis is reasonably configured, the shape of the first lens is controlled, the spherical aberration, chromatic aberration and field curvature of the optical system are comprehensively balanced, the risk of generating ghost images is reduced, the resolving power of the optical system is improved, and meanwhile, the processing difficulty of the first lens is reduced. Below the lower limit of the relation, the radius of curvature of the object side surface of the first lens element at the optical axis is too small relative to the radius of curvature of the image side surface of the first lens element at the optical axis, so that the object side surface of the first lens element is excessively bent, and the negative refractive power of the first lens element is insufficient, which is not beneficial to aberration correction of the optical system; exceeding the upper limit of the relation, the radius of curvature of the object side surface of the first lens element at the optical axis is too large relative to the radius of curvature of the image side surface of the first lens element at the optical axis, so that the object side surface of the first lens element is excessively flat, the negative refractive power of the first lens element is excessively high, the light rays of the marginal view field are excessively dispersed, and the distortion of the light ray system is further increased.

In one embodiment, the optical system satisfies the relationship: 5< R42/R41<50; wherein R41 is a radius of curvature of the object side surface of the fourth lens element at the optical axis, and R42 is a radius of curvature of the image side surface of the fourth lens element at the optical axis. Specifically, the values of R42/R41 may be 41.746, 13.856, 18.811, 17.847, 5.552, 47.991, 20.633, 32.915, and the like.

The optical system meets the relation, so that the ratio of the curvature radius of the image side surface of the fourth lens to the curvature radius of the object side surface of the fourth lens at the optical axis is reasonably configured, the shape of the fourth lens is controlled, the spherical aberration, chromatic aberration and field curvature of the optical system are comprehensively balanced, the risk of generating ghost images is reduced, the resolving power of the optical system is improved, and meanwhile, the processing difficulty of the fourth lens is reduced.

In one embodiment, the optical system satisfies the relationship: 120deg < fov <130deg; wherein the FOV is the maximum field angle of the optical system. Specifically, the value of the FOV may be 123 deg, 122 deg, 124 deg, 128 deg, 121 deg, 125 deg, 129 deg, 127 deg, etc.

The optical system meets the relation, so that the maximum field angle of the optical system is controlled within a reasonable range, the view finding area of a picture is effectively improved, and the optical system has a larger field angle.

In one embodiment, the optical system satisfies the relationship: 1.2< FNO <1.4; wherein FNO is the f-number of the optical system. Specifically, the value of FNO may be 1.220, 1.230, 1.370, 1.240, 1.280, 1.310, 1.340, 1.390, etc.

The optical system can meet the relation, so that the optical system is favorable for having a smaller aperture, and the relative brightness of the edge view field is improved, the imaging definition is improved, and the imaging quality is further improved by inhibiting the incident angle of light reaching the imaging surface.

In some embodiments, the optical system further comprises a filter, which may be an infrared cut filter or an infrared band pass filter, the infrared cut filter being configured to filter out infrared light, the infrared band pass filter allowing only infrared light to pass. In the application, the optical filter is an infrared band-pass optical filter, and is fixedly arranged relative to each lens in the optical system, and the infrared band-pass optical filter is used for filtering infrared light with a central wavelength and has the effect of filtering background stray light. The filter may be assembled with each lens as part of the optical system, or in other embodiments, the filter may be a separate component from the optical system, and the filter may be mounted between the optical system and the photosensitive chip when the optical system is assembled with the photosensitive chip. It is understood that the optical filter may be made of an optical glass coating, or may be made of colored glass, or may be made of other materials, and may be selected according to actual needs, which is not specifically limited in this embodiment. In other embodiments, the filtering effect may also be achieved by providing a filtering coating on at least one of the first lens to the fourth lens.

In some embodiments, at least one lens in the optical system may have a spherical surface shape, and the design of the spherical surface shape may reduce the difficulty of manufacturing the lens and reduce the manufacturing cost. In some embodiments, at least one lens of the optical system may also have an aspherical surface type, and when at least one side surface (object side surface or image side surface) of the lens is aspherical, the lens may be said to have an aspherical surface type. In some embodiments, the object side surface and the image side surface of each lens can be designed to be aspheric, and the aspheric design can help the optical system to eliminate aberration more effectively and improve imaging quality. In some embodiments, in order to achieve the advantages of manufacturing cost, manufacturing difficulty, imaging quality, assembly difficulty, etc., the design of each lens surface in the optical system may be composed of spherical and aspherical surface patterns.

In some embodiments, at least one lens of the optical system is made of Glass (GL, glass). For example, the first lens L1 closest to the object side is made of glass, and the influence of the environmental temperature change on the optical system can be effectively reduced by utilizing the temperature-eliminating and floating effect of the glass material of the first lens L1, so that the better and stable imaging quality is maintained. In some embodiments, the material of at least one lens in the optical system may also be Plastic (PC), and the Plastic material may be polycarbonate, gum, or the like. The lens with plastic material can reduce the production cost of the optical system, while the lens with glass material can endure higher or lower temperature and has excellent optical effect and better stability. In some embodiments, lenses of different materials may be disposed in the optical system, i.e. a combination of glass lenses and plastic lenses may be used, but the specific configuration relationship may be determined according to practical requirements, which is not meant to be exhaustive.

First embodiment

Referring to fig. 1, the optical system 10 of the present embodiment includes, in order from an object side to an image side along an optical axis:

the first lens element L1 with negative refractive power has a convex object-side surface S1 at a paraxial region and a concave image-side surface S2 at a paraxial region.

The second lens element L2 with positive refractive power has a convex object-side surface S3 at a paraxial region and a convex image-side surface S4 at a paraxial region.

The third lens element L3 with positive refractive power has a concave object-side surface S5 at a paraxial region and a convex image-side surface S6 at a paraxial region.

The fourth lens element L4 with positive refractive power has a convex object-side surface S7 at a paraxial region and a concave image-side surface S8 at a paraxial region.

In addition, the optical system 10 further includes a stop STO, a filter IR, and an imaging plane IMG. In the present embodiment, the stop STO is disposed between the image side surface of the second lens L2 and the object side surface of the third lens L3 of the optical system 10 for controlling the amount of light entering. The optical filter IR is disposed between the fourth lens L4 and the imaging plane IMG, and includes an object side surface S9 and an image side surface S10, and is an infrared band-pass filter, and the infrared cut-off filter is used for passing infrared light, so that the light incident on the imaging plane IMG is only infrared light, the wavelength of visible light is 380nm-780nm, and the infrared band-pass filter may be made of GLASS (GLASS) or Plastic (plastics) and may be coated on the surface thereof. The materials of the first lens L1 to the fourth lens L4 can be GLASS (GLASS) or Plastic (Plastic). The effective pixel area of the photosensitive chip is positioned on the imaging surface, an infrared photosensitive chip is arranged at the IMG of the imaging surface, and the photosensitive chip captures information of different wave bands of an object for subsequent processing.

Table 1a shows various parameters of the optical system 10 of the present embodiment, wherein the Y radius is the radius of curvature of the object side or image side of the corresponding plane number at the optical axis. The surface numbers S1 and S2 are the object side surface S1 and the image side surface S2 of the first lens element L1, respectively, i.e., 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 in the same lens element. The first value in the "thickness" parameter row of the first lens element L1 is the thickness of the lens element on the optical axis, and the second value is the distance from the image side surface of the lens element to the rear surface in the image side direction on the optical axis. The focal length, the refractive index of the material and the Abbe number are all obtained by adopting visible light with the reference wavelength of 940nm, and the units of the radius, the thickness and the focal length of Y are all millimeters (mm).

TABLE 1a

Where 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 angle of the optical system 10, and TTL is the distance from the object side surface of the first lens to the imaging surface on the optical axis, i.e. the total optical length.

In the present embodiment, the object-side surface and the image-side surface of the fourth lens element L4 are aspheric, and the aspheric surface profile x can be defined by, but not limited to, the following aspheric formula:

wherein x is the distance from the corresponding point on the aspheric surface to the plane tangent to the vertex of the surface, h is the distance from the corresponding point on the aspheric surface to the optical axis, c is the curvature of the vertex of the aspheric surface, k is the conic coefficient, ai is the coefficient corresponding to the i-th higher term in the aspheric surface formula. Table 1b shows the higher order coefficients A4, A6, A8, a10, a12, a14, a16 for the aspherical mirrors S7, S8 that can be used in the first embodiment.

TABLE 1b

Fig. 2 (a) shows: the optical system 10 of the first embodiment has a longitudinal spherical aberration curve at a wavelength of 940.0000nm, in which the abscissa along the X-axis represents the focus offset, i.e., the distance (in mm) from the imaging plane to the intersection of the light rays with the optical axis, the ordinate along the Y-axis represents the normalized field of view, and the longitudinal spherical aberration curve represents the focus offset of the light rays at different wavelengths after passing through the lenses of the optical system 10. As can be seen from fig. 2 (a), the degree of focus deviation of the light beams of the respective wavelengths in the first embodiment tends to be uniform, and the diffuse spots or halos in the imaging screen are effectively suppressed, which means that the imaging quality of the optical system 10 in this embodiment is good.

Fig. 2 (b) shows: the optical system 10 of the first embodiment has an astigmatic diagram at a wavelength of 940.0000nm, in which the abscissa in the X-axis direction represents the focus offset and the ordinate in the Y-axis direction represents the angle of view in deg. The S curve in the astigmatic plot represents the sagittal field curve at 940.0000nm and the T curve represents the meridional field curve at 940.0000 nm. As can be seen from fig. 2 (b), the curvature of field of the optical system 10 is small, the curvature of field and astigmatism of each field of view are well corrected, and the center and edges of the field of view have clear imaging.

Fig. 2 (c) shows: the optical system 10 of the first embodiment has a distortion curve at a wavelength of 940.0000 nm. Wherein, the abscissa along the X-axis direction represents the distortion value, the sign is given, and the ordinate along the Y-axis direction represents the image height in mm. The distortion curves represent distortion magnitude values corresponding to different angles of view. As can be seen from fig. 2 (c), at a wavelength of 940.0000nm, the image distortion caused by the main beam is small, and the imaging quality of the system is excellent.

As can be seen from fig. 2 (a), 2 (b) and 2 (c), the optical system 10 of the present embodiment has small aberration, good imaging quality, and good imaging quality.

Second embodiment

Referring to fig. 3, the optical system 10 of the present embodiment includes, in order from an object side to an image side along an optical axis:

The other structures of the second embodiment are the same as those of the first embodiment, and reference is made thereto.

Table 2a shows parameters of the optical system 10 of the present embodiment, in which the focal length, the refractive index of the material, and the abbe number are obtained using visible light having a reference wavelength of 940nm, and the Y radius, the thickness, and the focal length are each in millimeters (mm), and other parameters have the same meaning as those of the first embodiment.

TABLE 2a

Where f is the focal length of the optical system 10, FNO is the f-number of the optical system 10, FOV is the maximum angle of view of the optical system 10, and TTL is the distance from the object side surface of the first lens to the imaging surface on the optical axis, i.e. the total optical length.

Table 2b gives the higher order coefficients that can be used for each aspherical mirror in the second embodiment, where each aspherical mirror profile can be defined by the formula given in the first embodiment.

TABLE 2b

Fig. 4 (a), 4 (b) and 4 (c) show longitudinal spherical aberration curves, astigmatic curves and distortion curves of the optical system 10 at different focal lengths in the second embodiment, respectively, wherein the longitudinal spherical aberration curves represent the focus deviations of light rays of different wavelengths after passing through the lenses of the optical system 10; astigmatic curves represent meridian field curves and sagittal field curves; the distortion curves represent distortion magnitude values corresponding to different angles of view. As can be seen from the aberration diagram in fig. 4, the longitudinal spherical aberration, curvature of field, and distortion of the optical system 10 are all well controlled, so that the optical system 10 of this embodiment has good imaging quality.

Third embodiment

Referring to fig. 5, the optical system 10 of the present embodiment includes, in order from an object side to an image side along an optical axis:

The other structures of the third embodiment are the same as those of the first embodiment, and reference is made thereto.

Table 3a shows parameters of the optical system 10 of the present embodiment, in which the focal length, the refractive index of the material, and the abbe number are obtained using visible light having a reference wavelength of 940nm, and the Y radius, the thickness, and the focal length are each in millimeters (mm), and other parameters have the same meaning as those of the first embodiment.

TABLE 3a

Table 3b gives the higher order coefficients that can be used for each of the aspherical mirror surfaces in the third embodiment, where each of the aspherical surface types can be defined by the formula given in the first embodiment.

TABLE 3b

Fig. 6 (a), 6 (b) and 6 (c) show longitudinal spherical aberration curves, astigmatic curves and distortion curves of the optical system 10 at different focal lengths in the third embodiment, respectively, wherein the longitudinal spherical aberration curves represent the focus deviations of light rays of different wavelengths after passing through the lenses of the optical system 10; astigmatic curves represent meridian field curves and sagittal field curves; the distortion curves represent distortion magnitude values corresponding to different angles of view. As can be seen from the aberration diagram in fig. 6, the longitudinal spherical aberration, curvature of field, and distortion of the optical system 10 are all well controlled, so that the optical system 10 of this embodiment has good imaging quality.

Fourth embodiment

Referring to fig. 7, the optical system 10 of the present embodiment includes, in order from an object side to an image side along an optical axis:

The fourth embodiment further includes a cover glass CG disposed between the filter IR and the imaging plane IMG, including an object side surface S11 and an image side surface S12, and other structures of the fourth embodiment are the same as those of the first embodiment, and reference is made thereto.

Table 4a shows parameters of the optical system 10 of the present embodiment, in which the focal length, the refractive index of the material, and the abbe number are obtained using visible light having a reference wavelength of 940nm, and the Y radius, the thickness, and the focal length are each in millimeters (mm), and other parameters have the same meaning as those of the first embodiment.

TABLE 4a

Table 4b gives the higher order coefficients that can be used for each aspherical mirror in the fourth embodiment, where each aspherical mirror profile can be defined by the formula given in the first embodiment.

TABLE 4b

Fig. 8 (a), 8 (b) and 8 (c) show longitudinal spherical aberration curves, astigmatic curves and distortion curves of the optical system 10 at different focal lengths in the fourth embodiment, respectively, wherein the longitudinal spherical aberration curves represent the focus deviations of light rays of different wavelengths after passing through the lenses of the optical system 10; astigmatic curves represent meridian field curves and sagittal field curves; the distortion curves represent distortion magnitude values corresponding to different angles of view. As is clear from the aberration diagram in fig. 8, the longitudinal spherical aberration, curvature of field, and distortion of the optical system 10 are all well controlled, so that the optical system 10 of this embodiment has good imaging quality.

Fifth embodiment

Referring to fig. 9, the optical system 10 of the present embodiment includes, in order from an object side to an image side along an optical axis:

The third lens element L3 with positive refractive power has a convex object-side surface S5 at a paraxial region and a convex image-side surface S6 at a paraxial region.

The fifth embodiment further includes a cover glass CG disposed between the filter IR and the imaging plane IMG, including an object side surface S11 and an image side surface S12, and other structures of the fifth embodiment are the same as those of the first embodiment, and reference is made thereto.

Table 5a shows parameters of the optical system 10 of the present embodiment, in which the focal length, the refractive index of the material, and the abbe number are obtained using visible light having a reference wavelength of 940nm, and the Y radius, the thickness, and the focal length are each in millimeters (mm), and other parameters have the same meaning as those of the first embodiment.

TABLE 5a

Table 5b gives the higher order coefficients that can be used for each of the aspherical mirror surfaces in the fifth embodiment, where each of the aspherical surface types can be defined by the formula given in the first embodiment.

TABLE 5b

Fig. 10 (a), 10 (b) and 10 (c) show longitudinal spherical aberration curves, astigmatic curves and distortion curves of the optical system 10 at different focal lengths in the fifth embodiment, respectively, wherein the longitudinal spherical aberration curves represent the focus deviations of light rays of different wavelengths after passing through the lenses of the optical system 10; astigmatic curves represent meridian field curves and sagittal field curves; the distortion curves represent distortion magnitude values corresponding to different angles of view. As is clear from the aberration diagram in fig. 10, the longitudinal spherical aberration, curvature of field, and distortion of the optical system 10 are all well controlled, so that the optical system 10 of this embodiment has good imaging quality.

Table 6 shows values of FOV/f, f1/f, f2/f, f3/f, f4/f, f3/f4, R11/R12, ta/Tb, (Db-Da)/f, FNO, SD11/SD42, R42/R41, FOV in the optical systems of the first to fifth embodiments.

TABLE 6

As can be seen from table 6, the optical systems of the first to fifth embodiments all satisfy the following relations: values of 40deg/mm < FOV/f <60deg/mm, -1.8< f1/f < -1.5 >, 3< f2/f <6, 2< f3/f <5, 2.3< f4/f <3.7, 0.8< f3/f4<2, 4< R11/R12<10, 0.2< Ta/Tb <0.4, 0.25< - (Db-Da)/f <0.65, 1.2< FNO <1.4, 1< SD11/SD42<1.4, 5< R42/R41<50, 120deg < FOV <130 deg.

Referring to fig. 11, the present invention further provides an image capturing module 20, where the image capturing module 20 includes a photosensitive chip 21 and the optical system 10 according to any one of the embodiments of the first aspect, and the photosensitive chip 21 is disposed on an image side of the optical system 10. The photosurface of the photosurface 21 is positioned on the imaging surface of the optical system 10, and light rays of objects incident on the photosurface through the lens can be converted into electric signals of an image. The photo-sensing chip 21 may be a complementary metal oxide semiconductor (Complementary Metal Oxide Semiconductor, CMOS) or a Charge-coupled Device (CCD). The camera module 20 may be an imaging module integrated on the electronic device 30 or may be a stand-alone lens. By adding the optical system 10 provided by the invention into the image pickup module 20, the image pickup module 20 can meet miniaturization and has good imaging effect by reasonably designing the surface type and the refractive power of each lens in the optical system 10.

Referring to fig. 12, the present invention further provides an electronic device 30, where the electronic device 30 includes a housing 31 and the camera module 20, and the camera module 20 is disposed in the housing 31. The electronic device 30 includes, but is not limited to, an automobile, a monitor, a smart phone, a computer, a smart watch, and the like. By adding the camera module 20 provided by the invention into the electronic equipment 30, the electronic equipment 30 can be miniaturized and has good imaging effect.

The foregoing disclosure is only illustrative of the preferred embodiments of the present invention and is not to be construed as limiting the scope of the invention, as it is understood by those skilled in the art that all or part of the procedures described above may be performed and equivalents thereof may be substituted for elements thereof without departing from the scope of the invention as defined in the claims.

Claims

1. An optical system, comprising, in order from an object side to an image side along an optical axis:

a first lens element with negative refractive power having a convex object-side surface at a paraxial region and a concave image-side surface at a paraxial region;

a second lens element with positive refractive power having a convex object-side surface and a convex image-side surface at a paraxial region;

A third lens element with positive refractive power having a convex image-side surface at a paraxial region;

a fourth lens element with positive refractive power having a convex object-side surface at a paraxial region and a concave image-side surface at a paraxial region;

the optical system satisfies the relation: 0.8< f3/f4<2,1.2< FNO <1.4;

wherein f3 is an effective focal length of the third lens, f4 is an effective focal length of the fourth lens, and FNO is an f-number of the optical system.

2. The optical system of claim 1, wherein the optical system satisfies the relationship:

2.3<f4/f<3.7；

wherein f is the effective focal length of the optical system.

3. The optical system of claim 1, wherein the optical system satisfies the relationship:

40deg/mm<FOV/f<60deg/mm；

wherein FOV is the maximum field angle of the optical system and f is the effective focal length of the optical system.

4. The optical system of claim 1, wherein the optical system satisfies the relationship:

0.2<Ta/Tb<0.4；

wherein Ta is a distance between the object side surface of the first lens element and the image side surface of the second lens element on the optical axis, and Tb is a distance between the image side surface of the second lens element and the imaging surface of the optical system on the optical axis.

5. The optical system of claim 1, further comprising a stop positioned between the second lens and the third lens, and wherein the optical system satisfies the relationship:

0.25<(Db-Da)/f<0.65；

wherein Da is the distance between the image side surface of the second lens and the diaphragm on the optical axis, db is the distance between the diaphragm and the object side surface of the third lens on the optical axis, and f is the effective focal length of the optical system.

6. The optical system of claim 1, wherein the optical system satisfies the relationship:

1<SD11/SD42<1.4；

wherein SD11 is the maximum effective aperture of the object side surface of the first lens element, and SD42 is the maximum effective aperture of the image side surface of the fourth lens element.

7. The optical system of claim 1, wherein the optical system satisfies the relationship:

4< R11/R12<10, and/or

5<R42/R41<50；

Wherein R11 is a radius of curvature of the object-side surface of the first lens element at the optical axis, R12 is a radius of curvature of the image-side surface of the first lens element at the optical axis, R41 is a radius of curvature of the object-side surface of the fourth lens element at the optical axis, and R42 is a radius of curvature of the image-side surface of the fourth lens element at the optical axis.

8. The optical system of claim 1, wherein the optical system satisfies the relationship:

120deg<FOV<130deg；

Wherein FOV is the maximum field angle of the optical system.

9. An image pickup module comprising the optical system of any one of claims 1 to 8 and a photosensitive chip, the photosensitive chip being located on an image side of the optical system.

10. An electronic device comprising a housing and the camera module of claim 9, the camera module being disposed within the housing.