Optical systems, camera modules and electronic devices

Abstract

The present invention relates to an optical system, a camera module and an electronic device. The optical system includes, from the object side to the image side, a first lens with positive refractive power; a second lens; a third lens; and a fourth lens, wherein the image side surface of the fourth lens is concave at the optical axis, the object side surface and the image side surface of the fourth lens are both aspherical, and at least one of the object side surface and the image side surface of the fourth lens has an inflection point; the optical system includes an aperture, which is arranged on the object side of the first lens or between the first lens and the fourth lens; the optical system satisfies: 0.5<SL / TTL<0.9; ‑1<SAG31 / CT3<0; SL is the distance from the aperture to the imaging surface of the optical system on the optical axis, TTL is the distance from the object side surface of the first lens to the imaging surface of the optical system on the optical axis, SAG31 is the sag of the object side surface of the third lens, and CT3 is the thickness of the third lens on the optical axis. An optical system that meets the above relationship has excellent imaging quality.

Description

Technical Field

[0001] The present invention relates to the field of optical imaging, and in particular to an optical system, a camera module and an electronic device. Background Art

[0002] In recent years, with the continuous development of photography technology, consumers' demand for more diverse camera modules and higher-quality images has increased. However, for typical camera modules, the relative brightness of the optical system at the edge of the field of view is insufficient when used for macro photography, resulting in poor image quality. Summary of the Invention

[0003] Based on this, it is necessary to provide an optical system, a camera module and an electronic device to address the problem of how to improve the imaging quality of the camera module during macro shooting.

[0004] An optical system, comprising, from the object side to the image side, the following:

[0005] a first lens element having positive refractive power;

[0006] a second lens having refractive power;

[0007] a third lens element having refractive power; and

[0008] a fourth lens having refractive power, wherein the image-side surface of the fourth lens is concave at the optical axis, the object-side surface and the image-side surface of the fourth lens are both aspherical, and at least one of the object-side surface and the image-side surface of the fourth lens has an inflection point;

[0009] The optical system includes an aperture, which is arranged on the object side of the first lens or between the first lens and the fourth lens;

[0010] And the optical system satisfies the relationship:

[0011] 0.5<SL / TTL<0.9;

[0012] -1<SAG31 / CT3<0;

[0013] Wherein, SL is the distance from the aperture to the imaging plane of the optical system on the optical axis, TTL is the distance from the object side surface of the first lens to the imaging plane of the optical system on the optical axis, SAG31 is the sagittal height of the object side surface of the third lens, that is, SAG31 is the vector from the intersection of the object side surface of the third lens on the optical axis to the position of the maximum effective semi-aperture of the surface in the direction parallel to the optical axis, the vector is positive when facing the image side direction of the optical system and negative when facing the object side direction, and CT3 is the thickness of the third lens on the optical axis.

[0014] When the above-mentioned refractive power configuration and relationship of the lenses are met, the optical system has a small field of view characteristic and is conducive to improving the imaging quality during macro photography. At the same time, the optical system will also have the characteristics of a small depth of field and a blurred background. Specifically, when the optical system satisfies the relationship of 0.5<SL / TTL<0.9, the optical system has a central aperture structure, and the aperture will be reasonably set in the optical system, so that the aperture of the object side of the first lens will increase, thereby effectively controlling the light cone angle of the edge field of view light when entering the optical system, adjusting the amount of light entering the optical system, and improving the relative brightness of the edge field of view, thereby improving the imaging quality. When -1<SAG31 / CT3<0 is met, it is conducive to correcting the distortion and field curvature of the optical system and improving the imaging quality. When SAG31 / CT3≥0, the surface shape of the object side of the third lens at the circumference (at the maximum effective semi-aperture) is too smooth, resulting in insufficient refractive power for the light of the off-axis field of view, which is not conducive to the correction of distortion and field curvature aberrations. When SAG31 / CT3≤-1, the object side surface of the third lens is excessively curved at the circumference (at the maximum effective semi-aperture), which may easily lead to poor lens molding and affect the manufacturing yield.

[0015] In one embodiment, the optical system satisfies the relationship:

[0016] 0.4<DT11 / DT42<0.9;

[0017] Wherein, DT11 is the maximum effective semi-aperture of the object-side surface of the first lens, and DT42 is the maximum effective semi-aperture of the image-side surface of the fourth lens. When the above relationship is satisfied, the maximum effective semi-apertures of the object-side surface of the first lens and the image-side surface of the fourth lens are optimally configured, thereby effectively controlling the incident angle of the principal ray and increasing the relative brightness of the peripheral field of view, thereby improving the imaging quality of the optical system.

[0018] In one embodiment, the optical system satisfies the relationship:

[0019] 20mm<OBL<40mm;

[0020] Wherein, OBL is the distance on the optical axis from the object plane of the optical system to the object side surface of the first lens. A subject located on the object plane can form a clear image on the imaging surface of the optical system. When the optical system satisfies the relationship 20mm<OBL<40mm, a subject located on the object plane (or understood as being within this distance range) can form a clear image on the imaging surface of the optical system, thereby fully demonstrating the macro photography performance of the optical system.

[0021] In one embodiment, the optical system satisfies the relationship:

[0022] 0.1<|SAG41| / CT4<2.0;

[0023] Wherein, SAG41 is the sagittal height of the object side surface of the fourth lens, that is, SAG41 is the vector from the intersection of the object side surface of the fourth lens on the optical axis to the position of the maximum effective semi-aperture of the surface in a direction parallel to the optical axis. The vector is positive when facing the image side of the optical system and negative when facing the object side. CT4 is the thickness of the fourth lens on the optical axis. When the above relationship is satisfied, the incident angle of the principal light incident on the imaging surface of the optical system can be reduced, and the incident angle of the light at the maximum field of view on the object side surface of the fourth lens can be effectively controlled. Therefore, when the slope of the object side surface of the fourth lens varies significantly, the reflected energy caused by uneven coating can be reduced, avoiding the generation of stray light.

[0024] In one embodiment, the optical system satisfies the relationship:

[0025] -1≤f1 / f2≤1;

[0026] Among them, f1 is the effective focal length of the first lens, and f2 is the effective focal length of the second lens. The first lens provides positive refractive power for the optical system, which is conducive to better convergence of light and entry into the optical system, so that the optical system has a telephoto characteristic. When the optical system satisfies -1≤f1 / f2<0, the second lens will provide negative refractive power for the optical system, which is conducive to the divergence of light, thereby effectively correcting aberrations. When the optical system satisfies 0<f1 / f2≤1, the principal surface of the optical system moves forward, thereby increasing the focal length of the optical system, so that the optical system has a small field of view and a long focal length, thereby achieving excellent macro shooting effects.

[0027] In one embodiment, the optical system satisfies the relationship:

[0028] FNO≤3.55;

[0029] Wherein, FNO is the aperture number of the optical system. When the above relationship is satisfied, the light throughput of the optical system can be increased, and the optical system can obtain clear detail information of the subject even in a dark environment or insufficient light, thereby improving the imaging quality.

[0030] In one embodiment, the optical system satisfies the relationship:

[0031] 0.5<CT3 / CT2<3.0;

[0032] Where CT2 is the thickness of the second lens on the optical axis, and CT3 is the thickness of the third lens on the optical axis. When the above relationship is satisfied, the relative brightness of the peripheral field of view of the optical system can be effectively improved, and the yield rate of the lens assembly can be improved.

[0033] In one embodiment, the optical system satisfies the relationship:

[0034] 0.1<R1 / R9<0.7;

[0035] Wherein, R1 is the radius of curvature of the object side surface of the first lens at the optical axis, and R9 is the radius of curvature of the image side surface of the fourth lens at the optical axis. When the above relationship is satisfied, the incident angle of light entering the optical system can be reduced, thereby reducing the field of view angle of the optical system.

[0036] In one embodiment, the optical system satisfies the relationship:

[0037] -3<(f2+f4) / f<1;

[0038] Where f2 is the effective focal length of the second lens, f4 is the effective focal length of the fourth lens, and f is the effective focal length of the optical system. When the above relationship is satisfied, the effective focal lengths of the second and fourth lenses can be reasonably aligned with the effective focal length of the optical system, ensuring the magnification of the optical system within the macro shooting distance and recognition accuracy, while also reducing aberrations of the optical system and improving the imaging quality of the optical system.

[0039] A camera module comprises a photosensitive element and the optical system described in any one of the above embodiments, wherein the photosensitive element is arranged on the image side of the fourth lens.

[0040] By adopting the above optical system, the camera module has the characteristics of a narrow viewing angle, a small depth of field, and a blurred background. At the same time, when the camera module is used for macro photography, the relative brightness of the edge field of view will be improved, thereby effectively improving the image quality.

[0041] In one embodiment, the camera module satisfies the following relationship:

[0042] TTL / ImgH<2.65;

[0043] Wherein, ImgH is half of the diagonal length of the effective pixel area on the photosensitive element. When the above relationship is satisfied, the camera module can meet the high pixel requirement while maintaining the module size to be small.

[0044] An electronic device comprises a housing and the above-mentioned camera module, wherein the camera module is arranged in the housing.

[0045] By adopting the camera module, the electronic device will have excellent imaging quality when taking macro photos. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 A schematic diagram of an optical system provided in the first embodiment of the present application;

[0047] Figure 2 : spherical aberration diagram (mm), astigmatism diagram (mm), and distortion diagram (%) of the optical system in the first embodiment;

[0048] Figure 3 A schematic diagram of an optical system provided in accordance with a second embodiment of the present application;

[0049] Figure 4 : spherical aberration diagram (mm), astigmatism diagram (mm), and distortion diagram (%) of the optical system in the second embodiment;

[0050] Figure 5 A schematic diagram of an optical system provided in a third embodiment of the present application;

[0051] Figure 6 : spherical aberration diagram (mm), astigmatism diagram (mm), and distortion diagram (%) of the optical system in the third embodiment;

[0052] Figure 7 A schematic diagram of an optical system provided in a fourth embodiment of the present application;

[0053] Figure 8 : spherical aberration diagram (mm), astigmatism diagram (mm), and distortion diagram (%) of the optical system in the fourth embodiment;

[0054] Figure 9 A schematic diagram of an optical system provided in a fifth embodiment of the present application;

[0055] Figure 10 : spherical aberration diagram (mm), astigmatism diagram (mm), and distortion diagram (%) of the optical system in the fifth embodiment;

[0056] Figure 11 A schematic diagram of an optical system provided in accordance with a sixth embodiment of the present application;

[0057] Figure 12 : spherical aberration diagram (mm), astigmatism diagram (mm), and distortion diagram (%) of the optical system in the sixth embodiment;

[0058] Figure 13 A schematic diagram of a camera module provided in one embodiment of the present application;

[0059] Figure 14 A schematic diagram of an electronic device provided in one embodiment of the present application. DETAILED DESCRIPTION

[0060] To facilitate understanding of the present invention, the present invention will be described more fully below with reference to the accompanying drawings. The drawings illustrate preferred embodiments of the present invention. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive disclosure of the present invention.

[0061] It should be noted that when an element is referred to as being "fixed to" another component, it may be directly on the other component or there may be a central element. When an element is considered to be "connected to" another component, it may be directly connected to the other component or there may be a central element at the same time. In contrast, when an element is referred to as being "directly on" another component, there is no intermediate element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only.

[0062] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one skilled in the art to which this invention pertains. The terms used in this specification are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0063] refer to Figure 1 In one embodiment of the present application, the optical system 10 includes, from the object side to the image side, a first lens L1 having positive refractive power, a second lens L2 having refractive power, a third lens L3 having refractive power, and a fourth lens L4 having refractive power. The optical system 10 also includes an aperture STO, which is disposed between the first lens L1 and the second lens L2. The lenses and the aperture STO in the optical system 10 are coaxially arranged, that is, the centers of the lenses and the aperture STO are all located on the same straight line, which can also be referred to as the optical axis of the optical system 10.

[0064] In some embodiments, the aperture STO may also be disposed on the object side of the first lens L1. In other embodiments, the aperture STO is disposed between the first lens L1 and the fourth lens L4, for example, between the second lens L2 and the third lens L3, or between the third lens L3 and the fourth lens L4. Furthermore, in some embodiments, the aperture STO may be disposed on the object side or image side of any lens in the optical system 10. In this case, the projection of the aperture STO on the optical axis overlaps with the projection of the lens on the optical axis. This indicates that the aperture STO can be disposed between the object side of the first lens L1 and the fourth lens L4.

[0065] In this embodiment, the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 each comprise only one lens. However, it should be noted that in some embodiments, any one of the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 may be a lens group consisting of two or more lenses. For example, the first lens L1, the second lens L2, and the third lens L3 each comprise only one lens, while the fourth lens L4 comprises two or more lenses; or the first lens L1 and the second lens L2 each comprise only one lens, while the third lens L3 and the fourth lens L4 each comprise two lenses.

[0066] First lens L1 includes an object-side surface S1 and an image-side surface S2; second lens L2 includes an object-side surface S3 and an image-side surface S4; third lens L3 includes an object-side surface S5 and an image-side surface S6; and fourth lens L4 includes an object-side surface S7 and an image-side surface S8. Furthermore, optical system 10 also includes an imaging surface S11, which is located on the image side of fourth lens L4. After being adjusted by the various lenses of optical system 10, incident light is imaged on imaging surface S11. For ease of understanding, imaging surface S11 can be considered the photosensitive surface of a photosensitive element. Optical system 10 also has an object surface, and a subject located on this object surface forms a clear image on imaging surface S11.

[0067] In this embodiment, both the object-side surface S7 and the image-side surface S8 of the fourth lens L4 are aspherical, and both the object-side surface S7 and the image-side surface S8 of the fourth lens L4 have an inflection point. In some embodiments, both the object-side surface S7 and the image-side surface S8 of the first lens L1 through the fourth lens L4 are aspherical, and at least one of the object-side surface S7 and the image-side surface S8 of the fourth lens L4 has an inflection point. By configuring the fourth lens L4 as an aspherical lens and providing an inflection point on the light-transmitting surface of the fourth lens L4, aberrations of the optical system 10 can be effectively corrected, addressing the problem of visual field distortion. Furthermore, the fourth lens L4 can provide excellent optical effects for the optical system 10 while being relatively small and thin, thereby reducing the volume of the optical system 10 and achieving a compact design.

[0068] The calculation of the aspheric surface shape can refer to the aspheric surface formula:

[0069]

[0070] Where Z is the distance from the corresponding point on the aspheric surface to the plane tangent to the vertex of the surface, r is the distance from the corresponding point on the aspheric surface to the optical axis, c is the curvature of the aspheric vertex, k is the cone constant, and Ai is the coefficient corresponding to the i-th higher-order term in the aspheric surface shape formula.

[0071] It should be noted that when a side surface of a lens is described as convex at the optical axis (the central area of ​​the side surface), it can be understood that the area of ​​the side surface of the lens near the optical axis is convex, and therefore the side surface can also be considered to be convex near the axis; when a side surface of a lens is described as concave at the circumference, it can be understood that the area of ​​the side surface near the maximum effective semi-aperture is concave. For example, when the side surface is convex at the optical axis and also convex at the circumference, the shape of the side surface from the center (optical axis) to the edge can be purely convex; or it can first transition from a convex shape at the center to a concave shape, and then become convex when approaching the maximum effective semi-aperture. This is only an example to illustrate the relationship between the optical axis and the circumference. The various shape structures (concave-convex relationship) of the side surface are not fully reflected, but other situations can be deduced based on the above examples.

[0072] Specifically, in some embodiments, the image-side surface S8 of the fourth lens element L4 has an inflection point, and the image-side surface S8 is concave at the optical axis and convex at the circumference. When the fourth lens element L4 has this surface profile, the overall length of the optical system 10 can be shortened while effectively reducing the angle of incidence of the peripheral field of view onto the imaging surface S11, thereby improving the efficiency of light reception by the photosensitive element on the imaging surface S11.

[0073] In some embodiments, the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 are all made of plastic. In other embodiments, the first lens L1 is made of glass, while the second lens L2, the third lens L3, and the fourth lens L4 are all made of plastic. In this case, since the object-side lenses in the optical system 10 are made of glass, these object-side glass lenses are highly resistant to extreme environments and are less susceptible to aging due to the object-side environment. This effectively prevents degradation of image quality and shortened service life of the optical system 10 when exposed to extreme conditions such as high temperatures. Plastic lenses can reduce the weight and manufacturing cost of the optical system 10, while glass lenses can withstand higher temperatures and exhibit excellent optical performance. Of course, the material configuration of the lenses in the optical system 10 is not limited to the above embodiments; any lens can be made of either plastic or glass.

[0074] In some embodiments, an infrared cutoff filter L5 is provided on the image side of the fourth lens L4, or it can be understood that the infrared cutoff filter L5 is provided between the fourth lens L4 and the imaging surface S11. The infrared cutoff filter L5 includes an object-side surface S9 and an image-side surface S10. The infrared cutoff filter L5 is used to filter out infrared light, preventing it from reaching the imaging surface S11, thereby preventing infrared light from interfering with normal imaging. The infrared cutoff filter L5 can be assembled with each lens as part of the optical system 10, or it can be installed between the optical system 10 and the photosensitive element when the optical system 10 and the photosensitive element are assembled into a camera module. In some embodiments, the infrared cutoff filter L5 can also be provided on the object side of the first lens L1. In addition, in some embodiments, the infrared cutoff filter L5 can be omitted, and instead a filter coating can be provided on any lens from the first lens L1 to the fourth lens L4 to achieve the effect of filtering out infrared light.

[0075] As described above, in some embodiments, the optical system 10 may include, in addition to a lens having refractive power, an aperture STO, an infrared cutoff filter L5, a protective glass, a photosensitive element, a reflector for changing the incident light path, and other elements.

[0076] In some embodiments, optical system 10 satisfies the following relationship:

[0077] 0.5<SL / TTL<0.9;

[0078] -1<SAG31 / CT3<0;

[0079] Wherein, SL is the distance on the optical axis from the aperture STO to the imaging plane S11 of the optical system 10, TTL is the distance on the optical axis from the object-side surface S1 of the first lens element L1 to the imaging plane S11 of the optical system 10, SAG31 is the sag of the object-side surface S5 of the third lens element L3, that is, SAG31 is the vector parallel to the optical axis from the intersection of the object-side surface S5 of the third lens element L3 on the optical axis to the position of the maximum effective semi-aperture of the surface, and the vector is positive when facing the image side of the optical system 10 and negative when facing the object side, and CT3 is the thickness of the third lens element L3 on the optical axis, or CT3 can be understood as the center thickness of the third lens element L3. In some embodiments, SL / TTL can be 0.600, 0.610, 0.620, 0.650, 0.700, 0.750, 0.800, 0.830, 0.840, 0.850, or 0.860. In some embodiments, SAG31 / CT3 can be -0.840, -0.830, -0.800, -0.750, -0.600, -0.580, -0.500, -0.400, -0.300, -0.200, -0.150, -0.130, or -0.120. When the above relationship and lens configuration are met, the imaging quality of the optical system 10 during macro photography is improved, and the optical system 10 also has the characteristics of a small depth of field and a blurred background. Specifically, when the optical system 10 satisfies the relationship 0.5<SL / TTL<0.9, the optical system 10 has a central aperture structure, so that the aperture STO will be reasonably set in the optical system 10. In this way, the aperture of the object side surface S1 of the first lens L1 will be increased, thereby effectively controlling the light cone angle of the peripheral field of view light when entering the optical system 10, adjusting the amount of light entering the optical system 10, and increasing the relative brightness of the peripheral field of view, thereby improving the image quality. When the optical system 10 satisfies -1<SAG31 / CT3<0, it is beneficial to correct the distortion and field curvature of the optical system 10 and improve the image quality. However, when SAG31 / CT3≥0, the surface shape of the object side surface S5 of the third lens L3 at the circumference (at the maximum effective semi-aperture) is too smooth, resulting in insufficient refractive power for light in the off-axis field of view, which is not conducive to the correction of distortion and field curvature aberrations. When SAG31 / CT3≤-1, the object-side surface S5 of the third lens L3 is excessively curved at the circumference (the maximum effective semi-aperture), which may easily lead to poor lens molding and affect manufacturing yield.

[0080] In some embodiments, the optical system 10 satisfies the relationship: 0.4 < DT11 / DT42 < 0.9; where DT11 is the maximum effective semi-aperture of the object-side surface S1 of the first lens element L1, and DT42 is the maximum effective semi-aperture of the image-side surface S8 of the fourth lens element L4. In some embodiments, DT11 / DT42 can be 0.580, 0.590, 0.600, 0.650, 0.700, 0.750, 0.800, 0.840, 0.850, 0.860, or 0.870. When this relationship is satisfied, the maximum effective semi-apertures of the object-side surface S1 of the first lens element L1 and the image-side surface S8 of the fourth lens element L4 are optimally configured, thereby effectively controlling the incident angle of the principal ray and increasing the relative brightness of the peripheral field of view, thereby improving the imaging quality of the optical system 10.

[0081] In some embodiments, the optical system 10 satisfies the relationship: 20mm < OBL < 40mm; where OBL is the distance on the optical axis from the object plane of the optical system 10 to the object-side surface S1 of the first lens L1. Objects located on the object plane can form a clear image on the imaging surface S11 of the optical system 10. In some embodiments, OBL can be 26mm, 27mm, 28mm, 29mm, or 30mm. When the optical system 10 satisfies the relationship 20mm < OBL < 40mm, objects located on the object plane (or understood to be within this distance range) can form a clear image on the imaging surface S11 of the optical system 10, thereby fully demonstrating the macro photography performance of the optical system 10.

[0082] In some embodiments, the optical system 10 satisfies the relationship: 0.1 < |SAG41| / CT4 < 2.0; where SAG41 is the sag of the object-side surface S7 of the fourth lens element L4, i.e., SAG41 is the vector parallel to the optical axis from the intersection of the object-side surface of the fourth lens element L4 on the optical axis to the position of the maximum effective semi-aperture of the surface, with the vector being positive when oriented toward the image side of the optical system 10 and negative when oriented toward the object side. CT4 is the thickness of the fourth lens element L4 on the optical axis, or CT4 can be understood as the center thickness of the fourth lens element L4. In some embodiments, |SAG41| / CT4 can be 0.220, 0.240, 0.250, 0.300, 0.350, 0.500, 0.600, 0.650, 0.700, 1.000, 1.300, 1.400, 1.430, or 1.450. When the above relationship is satisfied, the incident angle of the principal light incident on the imaging surface S11 of the optical system 10 can be reduced, and the incident angle of the light at the maximum field of view on the object-side surface S7 of the fourth lens element L4 can be effectively controlled. Therefore, when the slope of the object-side surface S7 of the fourth lens element L4 varies significantly, the reflected energy caused by uneven coating can be reduced, thereby avoiding the generation of stray light.

[0083] In some embodiments, the optical system 10 satisfies the relationship: -1 ≤ f1 / f2 ≤ 1; where f1 is the effective focal length of the first lens element L1, and f2 is the effective focal length of the second lens element L2. The first lens element L1 provides positive refractive power to the optical system 10, thereby facilitating better convergence of light rays entering the optical system 10 and imparting a telephoto characteristic to the optical system 10. In some embodiments, f1 / f2 can be -0.700, -0.690, -0.650, -0.400, -0.200, 0.200, 0.400, 0.600, 0.700, 0.750, 0.800, 0.820, or 0.840. Specifically, when the optical system 10 satisfies -1 ≤ f1 / f2 < 0, the second lens element L2 provides negative refractive power to the optical system 10, facilitating divergence of light rays, thereby effectively correcting aberrations. When the optical system 10 satisfies 0<f1 / f2≤1, the principal surface of the optical system 10 moves forward, thereby increasing the focal length of the optical system 10, so that the optical system 10 has a small field of view and a long focal length, thereby achieving excellent macro shooting effects.

[0084] In some embodiments, the optical system 10 satisfies the relationship: FNO ≤ 3.55, where FNO is the aperture number of the optical system 10. In some embodiments, FNO can be 2.50, 2.55, 2.60, 2.70, 2.80, 2.90, 3.00, 3.20, 3.40, 3.45, 3.50, or 3.55. When this relationship is met, the optical system 10 can increase the amount of light passing through it, enabling the optical system 10 to capture clear, detailed information about the subject even in dark environments or low-light conditions, thereby improving imaging quality.

[0085] In some embodiments, the optical system 10 satisfies the relationship: 0.5 < CT3 / CT2 < 3.0, where CT3 is the thickness of the third lens element L3 along the optical axis, and CT2 is the thickness of the second lens element L2 along the optical axis. Alternatively, CT3 can be understood as the center thickness of the third lens element L3, or CT2 can be understood as the center thickness of the second lens element L2. In some embodiments, CT3 / CT2 can be 0.950, 0.960, 1.000, 1.300, 1.500, 1.800, 2.000, 2.200, 2.500, 2.600, 2.650, 2.700, 2.730, or 2.750. Meeting this relationship effectively improves the relative brightness of the peripheral field of view of the optical system 10 and improves the yield rate during lens assembly.

[0086] In some embodiments, the optical system 10 satisfies the relationship: 0.1 < R1 / R9 < 0.7, where R1 is the radius of curvature of the object-side surface S1 of the first lens element L1 at the optical axis, and R9 is the radius of curvature of the image-side surface S8 of the fourth lens element L4 at the optical axis. In some embodiments, R1 / R9 can be 0.220, 0.230, 0.250, 0.300, 0.350, 0.400, 0.450, 0.470, 0.500, 0.520, or 0.530. When this relationship is satisfied, the incident angle of light entering the optical system 10 can be reduced, thereby reducing the field of view of the optical system 10.

[0087] In some embodiments, the optical system 10 satisfies the relationship: -3 < (f2 + f4) / f < 1; where f2 is the effective focal length of the second lens element L2, f4 is the effective focal length of the fourth lens element L4, and f is the effective focal length of the optical system 10. In some embodiments, (f2 + f4) / f can be -2.500, -2.400, -2.000, -1.000, 0.100, 0.200, 0.300, 0.400, or 0.500. When the above relationship is satisfied, the effective focal lengths of the second lens element L2 and the fourth lens element L4 can be appropriately aligned with the effective focal length of the optical system 10, ensuring the magnification of the optical system 10 within the macro shooting distance and recognition accuracy. Furthermore, the aberrations of the optical system 10 can be reduced, thereby improving the imaging quality of the optical system 10.

[0088] In some embodiments, a photosensitive element is provided on the image side of the optical system 10, and the photosensitive element is used to receive light conditioned by the optical system 10. The optical system 10 and the photosensitive element constitute a camera module. In some embodiments, the camera module satisfies the relationship: TTL / ImgH<2.65; wherein ImgH is half of the diagonal length of the effective pixel area on the photosensitive element, or it can be understood that ImgH is half of the diagonal length of the effective pixel area on the imaging surface S11. In some embodiments, TTL / ImgH can be 2.35, 2.40, 2.45, 2.50, 2.55, 2.60 or 2.63. When the above relationship is met, the camera module can meet high pixel requirements while maintaining a small module size.

[0089] Next, the optical system 10 of the present application will be described with more specific and detailed embodiments.

[0090] First embodiment

[0091] refer to Figure 1 and Figure 2In the first embodiment, the optical system 10 includes, from the object side to the image side, a first lens L1 with positive refractive power, an aperture STO, a second lens L2 with negative refractive power, a third lens L3 with positive refractive power, and a fourth lens L4 with negative refractive power. Figure 2 It includes a spherical aberration diagram (mm), an astigmatism diagram (mm), and a distortion diagram (%) of the optical system 10 in the first embodiment, wherein the astigmatism diagram and the distortion diagram are data diagrams at a wavelength of 555 nm.

[0092] The ordinates of the astigmatism diagram and the distortion diagram may be understood as half of the diagonal length of the effective pixel area on the imaging surface S11 of the optical system 10 .

[0093] The object-side surface S1 of the first lens L1 is convex at the optical axis and at the circumference; the image-side surface S2 is convex at the optical axis and at the circumference.

[0094] The object-side surface S3 of the second lens L2 is concave at the optical axis and convex at the circumference; the image-side surface S4 is concave at the optical axis and concave at the circumference.

[0095] The object-side surface S5 of the third lens L3 is concave at the optical axis and concave at the circumference; the image-side surface S6 is convex at the optical axis and convex at the circumference.

[0096] The object-side surface S7 of the fourth lens L4 is convex along the optical axis and concave along the circumference. The image-side surface S8 is concave along the optical axis and convex along the circumference. The image-side surface S8 of the fourth lens L4 has an inflection point.

[0097] Since the image-side surface S8 of the fourth lens L4 has an inflection point and is concave at the optical axis and convex at the circumference, it is beneficial to shorten the overall length of the optical system 10. At the same time, it can effectively reduce the incident angle of the edge field of view incident on the imaging surface S11, thereby improving the efficiency of the photosensitive element on the imaging surface S11 in receiving light.

[0098] The object-side surface S7 and image-side surface S8 of the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 are all aspherical. By combining the aspherical surfaces of each lens in the optical system 10, the problem of field of view distortion in the optical system 10 can be effectively resolved. It also enables the lenses to achieve excellent optical effects while being relatively small and thin, thereby reducing the size of the optical system 10 and facilitating a miniaturized design of the optical system 10.

[0099] The first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 are all made of plastic. The use of plastic lenses can reduce the manufacturing cost of the optical system 10 and reduce the weight of the optical system 10.

[0100] Depend on Figure 1As can be seen, an infrared cutoff filter L5 is also provided on the image side of fourth lens L4 to filter out infrared light. In some embodiments, infrared cutoff filter L5 is part of optical system 10, for example, assembled to the lens barrel along with each lens. In other embodiments, infrared cutoff filter L5 is installed between optical system 10 and the photosensitive element when the optical system 10 and the photosensitive element are assembled into a camera module.

[0101] In the first embodiment, the optical system 10 satisfies the following relationships:

[0102] SL / TTL=0.869;

[0103] SAG31 / CT3=-0.184;

[0104] Wherein, SL is the distance on the optical axis from the aperture STO to the imaging surface S11 of the optical system 10, TTL is the distance on the optical axis from the object-side surface S1 of the first lens element L1 to the imaging surface S11 of the optical system 10, SAG31 is the sagittal height of the object-side surface S5 of the third lens element L3, that is, SAG31 is the vector from the intersection of the object-side surface S5 of the third lens element L3 on the optical axis to the position of the maximum effective semi-aperture of the surface in a direction parallel to the optical axis, and the vector is positive when facing the image side of the optical system 10 and negative when facing the object side, and CT3 is the thickness of the third lens element L3 on the optical axis, or CT3 can be understood as the center thickness of the third lens element L3. When the above relationship is satisfied, the macro shooting performance of the optical system 10 can be fully demonstrated, thereby facilitating improved imaging quality of the optical system 10 during macro shooting. At the same time, the optical system 10 will also have the characteristics of a small depth of field and a blurred background. Specifically, optical system 10 features a centrally located aperture structure, whereby aperture STO is optimally positioned within optical system 10. This increases the aperture of object-side surface S1 of first lens L1, effectively controlling the cone angle of light entering the peripheral field of view, thereby regulating the amount of light entering the optical system 10 and increasing the relative brightness of the peripheral field of view, thereby improving image quality. Furthermore, satisfying the aforementioned relationship facilitates correcting distortion and field curvature of optical system 10, thereby enhancing image quality.

[0105] DT11 / DT42 = 0.605; where DT11 is the maximum effective semi-aperture of the object-side surface S1 of the first lens element L1, and DT42 is the maximum effective semi-aperture of the image-side surface S8 of the fourth lens element L4. When this relationship is satisfied, the maximum effective semi-apertures of the object-side surface S1 of the first lens element L1 and the image-side surface S8 of the fourth lens element L4 are optimally configured, effectively controlling the incident angle of the principal ray and increasing the relative brightness of the peripheral field of view, thereby improving the imaging quality of the optical system 10.

[0106] OBL = 30mm; where OBL is the distance along the optical axis from the object plane of optical system 10 to the object-side surface S1 of first lens L1. A subject located on the object plane forms a clear image on imaging surface S11 of optical system 10. When this relationship is satisfied, a subject located on the object plane (or within this distance range) forms a clear image on imaging surface S11 of optical system 10, fully demonstrating the macro photography performance of optical system 10.

[0107] |SAG41| / CT4=0.712; where SAG41 is the sag of the object-side surface S7 of the fourth lens element L4, i.e., SAG41 is the vector parallel to the optical axis from the intersection of the object-side surface S7 of the fourth lens element L4 on the optical axis to the position of the maximum effective semi-aperture of the surface. This vector is positive when oriented toward the image side of the optical system 10 and negative when oriented toward the object side. CT4 is the thickness of the fourth lens element L4 along the optical axis. When this relationship is satisfied, the angle of incidence of the principal ray incident on the imaging surface S11 of the optical system 10 can be reduced, while the angle of incidence of the ray at the maximum field of view on the object-side surface S7 of the fourth lens element L4 can be effectively controlled. This reduces the reflected energy caused by uneven coating when the slope of the object-side surface S7 of the fourth lens element L4 varies significantly, thus preventing the generation of stray light.

[0108] f1 / f2 = -0.646; where f1 is the effective focal length of first lens element L1, and f2 is the effective focal length of second lens element L2. First lens element L1 provides positive refractive power to optical system 10, thereby facilitating better convergence of light entering optical system 10 and imparting telephoto characteristics to optical system 10. When this relationship is satisfied, second lens element L2 provides negative refractive power to optical system 10, facilitating divergence of light and effectively correcting aberrations.

[0109] FNO = 3.00, where FNO is the aperture number of the optical system 10. When the above relationship is satisfied, the light throughput of the optical system 10 can be increased, enabling the optical system 10 to obtain clear details of the subject even in dark environments or insufficient light, thereby improving imaging quality.

[0110] CT3 / CT2 = 1.339, where CT3 is the thickness of the third lens element L3 along the optical axis, and CT2 is the thickness of the second lens element L2 along the optical axis. Satisfying this relationship effectively improves the relative brightness of the peripheral field of view of the optical system 10 and increases the yield rate during lens assembly.

[0111] R1 / R9 = 0.459; where R1 is the radius of curvature of the object-side surface S1 of the first lens element L1 at the optical axis, and R9 is the radius of curvature of the image-side surface S8 of the fourth lens element L4 at the optical axis. When this relationship is satisfied, the incident angle of light entering the optical system 10 can be reduced, thereby reducing the field of view of the optical system 10.

[0112] (f2+f4) / f=-2.588; where f2 is the effective focal length of second lens element L2, f4 is the effective focal length of fourth lens element L4, and f is the effective focal length of optical system 10. When this relationship is satisfied, the effective focal lengths of second lens element L2 and fourth lens element L4 are optimally aligned with the effective focal length of optical system 10, ensuring the magnification of optical system 10 within the macro shooting distance and ensuring recognition accuracy. Furthermore, this reduces aberrations in optical system 10, improving the imaging quality of optical system 10.

[0113] In some embodiments, a photosensitive element is disposed on the image side of the optical system 10. The photosensitive element is used to receive light conditioned by the optical system 10. The optical system 10 and the photosensitive element constitute a camera module. In some embodiments, the camera module satisfies the relationship: TTL / ImgH = 2.63. When this relationship is met, the camera module can achieve high pixel requirements while maintaining a compact module size.

[0114] When the above-mentioned lens refractive power configuration and relationship are met, the optical system 10 has a small field of view characteristic, and the macro photography performance of the optical system 10 can be fully demonstrated, thereby improving the image quality of the optical system 10 during macro photography. At the same time, the optical system 10 also has the characteristics of a small depth of field and a blurred background.

[0115] In addition, the lens parameters of the optical system 10 are given in Tables 1 and 2. K in Table 2 is the cone constant, and Ai is the coefficient corresponding to the i-th higher-order term in the aspheric surface formula. The elements from the object plane to the imaging plane S11 are arranged in the order of the elements from top to bottom in Table 1. Surface numbers 1 and 2 represent the object side surface S1 and image side surface S2 of the first lens L1, respectively. 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 Y radius in Table 1 is the radius of curvature of the object side surface or image side surface of the corresponding surface number at the paraxial position (or understood as on the optical axis). The first value in the "Thickness" parameter column of a lens is the thickness of the lens on the optical axis, and the second value is the distance from the image side surface of the lens to the object side surface of the next lens on the optical axis. The "Thickness" parameter in surface number 2 is the distance from the image side surface S4 of the second lens L2 to the aperture STO. The value of the aperture STO parameter listed in the "Thickness" column is the distance on the optical axis from the aperture STO to the vertex of the object side surface of the next lens (the second lens L2 in this embodiment) (the vertex refers to the intersection of the lens and the optical axis). We assume that the direction from the object side surface of the first lens L1 to the image side surface of the last lens is the positive direction of the optical axis. When this value is negative, it indicates that the aperture STO is set to the right of the vertex of the object side surface of the lens (or it can be understood as being located on the image side of the vertex). When the "Thickness" parameter of the aperture STO is positive, the aperture STO is to the left of the vertex of the object side surface of the lens (or it can be understood as being located on the object side of the vertex). The optical axes of the lenses in this embodiment of the present application are on the same straight line, which serves as the optical axis of the optical system 10. The "Thickness" parameter value in surface number 9 is the distance on the optical axis from the image side surface S8 of the fourth lens L4 to the object side surface S9 of the infrared cutoff filter L5. The “thickness” parameter value corresponding to the surface number 11 of the infrared cut filter L5 is the distance from the image-side surface S10 of the infrared cut filter L5 to the image plane (imaging plane S11 ) of the optical system 10 on the optical axis.

[0116] In the first embodiment, the optical system 10 has an effective focal length f=4.140 mm, an aperture number FNO=3.0, a maximum field of view (diagonal viewing angle) FOV=40.1°, and a total optical length TTL=5.208 mm, where the total optical length TTL is the distance along the optical axis from the object-side surface S1 of the first lens element L1 to the imaging surface S11 of the optical system 10.

[0117] In the following examples (Example 1, Example 2, Example 3, Example 4, Example 5, and Example 6), the refractive index, Abbe number, and focal length of each lens are values ​​at a wavelength of 555 nm. Furthermore, the relationship calculations and lens surface profiles of each example are subject to the lens parameters (such as Tables 1, 2, 3, and 4).

[0118] Table 1

[0119]

[0120] Table 2

[0121]

[0122]

[0123] Second embodiment

[0124] refer to Figure 3 and Figure 4 In the second embodiment, the optical system 10 includes, from the object side to the image side, a first lens L1 with positive refractive power, an aperture STO, a second lens L2 with positive refractive power, a third lens L3 with positive refractive power, and a fourth lens L4 with negative refractive power. Figure 4 It includes a spherical aberration diagram (mm), an astigmatism diagram (mm), and a distortion diagram (%) of the optical system 10 in the second embodiment, wherein the astigmatism diagram and the distortion diagram are data diagrams at a wavelength of 555 nm.

[0125] The object-side surface S1 of the first lens L1 is convex at the optical axis and convex at the circumference; the image-side surface S2 is concave at the optical axis and concave at the circumference.

[0126] The object-side surface S3 of the second lens L2 is convex at the optical axis and convex at the circumference; the image-side surface S4 is concave at the optical axis and concave at the circumference.

[0127] The object-side surface S5 of the third lens L3 is concave at the optical axis and concave at the circumference; the image-side surface S6 is convex at the optical axis and convex at the circumference.

[0128] The object-side surface S7 of the fourth lens L4 is concave along the optical axis and concave along the circumference, while the image-side surface S8 is concave along the optical axis and convex along the circumference. The image-side surface S8 of the fourth lens L4 has an inflection point.

[0129] The object-side surface S7 and image-side surface S8 of the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 are all aspherical. By combining the aspherical surfaces of each lens in the optical system 10, the problem of field of view distortion in the optical system 10 can be effectively resolved. It also enables the lenses to achieve excellent optical effects while being relatively small and thin, thereby reducing the size of the optical system 10 and facilitating a miniaturized design of the optical system 10.

[0130] The first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 are all made of plastic. The use of plastic lenses can reduce the manufacturing cost of the optical system 10 and reduce the weight of the optical system 10.

[0131] Depend on Figure 3As can be seen, an infrared cutoff filter L5 is also provided on the image side of fourth lens L4 to filter out infrared light. In some embodiments, infrared cutoff filter L5 is part of optical system 10, for example, assembled to the lens barrel along with each lens. In other embodiments, infrared cutoff filter L5 is installed between optical system 10 and the photosensitive element when the optical system 10 and the photosensitive element are assembled into a camera module.

[0132] In the second embodiment, the effective focal length f of the optical system 10 is 3.968 mm, the aperture number FNO is 2.45, the maximum field angle (diagonal viewing angle) FOV is 50.1°, and the total optical length TTL is 4.62 mm.

[0133] In addition, the parameters of each lens of the optical system 10 are given in Table 3 and Table 4, wherein the definition of each parameter can be obtained from the first embodiment and will not be repeated here.

[0134] Table 3

[0135]

[0136]

[0137] Table 4

[0138]

[0139] From the above data we can get:

[0140]

[0141] Third embodiment

[0142] refer to Figure 5 and Figure 6 In the third embodiment, the optical system 10 includes, from the object side to the image side, a first lens L1 with positive refractive power, an aperture STO, a second lens L2 with positive refractive power, a third lens L3 with negative refractive power, and a fourth lens L4 with negative refractive power. Figure 6 It includes a spherical aberration diagram (mm), an astigmatism diagram (mm), and a distortion diagram (%) of the optical system 10 in the third embodiment, wherein the astigmatism diagram and the distortion diagram are data diagrams at a wavelength of 555 nm.

[0143] The object-side surface S1 of the first lens L1 is convex at the optical axis and convex at the circumference; the image-side surface S2 is concave at the optical axis and concave at the circumference.

[0144] The object-side surface S3 of the second lens L2 is convex at the optical axis and convex at the circumference; the image-side surface S4 is concave at the optical axis and convex at the circumference.

[0145] The object-side surface S5 of the third lens L3 is concave at the optical axis and concave at the circumference; the image-side surface S6 is convex at the optical axis and convex at the circumference.

[0146] The object-side surface S7 of the fourth lens L4 is concave along the optical axis and concave along the circumference, while the image-side surface S8 is concave along the optical axis and convex along the circumference. The image-side surface S8 of the fourth lens L4 has an inflection point.

[0147] The object-side surface S7 and image-side surface S8 of the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 are all aspherical. By combining the aspherical surfaces of each lens in the optical system 10, the problem of field of view distortion in the optical system 10 can be effectively resolved. It also enables the lenses to achieve excellent optical effects while being relatively small and thin, thereby reducing the size of the optical system 10 and facilitating a miniaturized design of the optical system 10.

[0148] The first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 are all made of plastic. The use of plastic lenses can reduce the manufacturing cost of the optical system 10 and reduce the weight of the optical system 10.

[0149] Depend on Figure 5 As can be seen, an infrared cutoff filter L5 is also provided on the image side of fourth lens L4 to filter out infrared light. In some embodiments, infrared cutoff filter L5 is part of optical system 10, for example, assembled to the lens barrel along with each lens. In other embodiments, infrared cutoff filter L5 is installed between optical system 10 and the photosensitive element when the optical system 10 and the photosensitive element are assembled into a camera module.

[0150] In the third embodiment, the effective focal length f of the optical system 10 is 4.08 mm, the aperture number FNO is 3.1, the maximum field angle (diagonal viewing angle) FOV is 38.7°, and the total optical length TTL is 5.21 mm.

[0151] In addition, the parameters of each lens of the optical system 10 are given in Table 5 and Table 6, wherein the definition of each parameter can be obtained from the first embodiment and will not be repeated here.

[0152] Table 5

[0153]

[0154] Table 6

[0155]

[0156]

[0157] From the above data we can get:

[0158]

[0159] Fourth embodiment

[0160] refer to Figure 7 and Figure 8 In the fourth embodiment, the optical system 10 includes, from the object side to the image side, a first lens L1 with positive refractive power, a second lens L2 with negative refractive power, an aperture STO, a third lens L3 with negative refractive power, and a fourth lens L4 with positive refractive power. Figure 8 It includes a spherical aberration diagram (mm), an astigmatism diagram (mm), and a distortion diagram (%) of the optical system 10 in the fourth embodiment, wherein the astigmatism diagram and the distortion diagram are data diagrams at a wavelength of 555 nm.

[0161] The object-side surface S1 of the first lens L1 is convex at the optical axis and at the circumference; the image-side surface S2 is convex at the optical axis and at the circumference.

[0162] The object-side surface S3 of the second lens L2 is convex at the optical axis and convex at the circumference; the image-side surface S4 is concave at the optical axis and concave at the circumference.

[0163] The object-side surface S5 of the third lens L3 is convex at the optical axis and concave at the circumference; the image-side surface S6 is concave at the optical axis and convex at the circumference.

[0164] The object-side surface S7 of the fourth lens L4 is convex along the optical axis and concave along the circumference. The image-side surface S8 is concave along the optical axis and convex along the circumference. The image-side surface S8 of the fourth lens L4 has an inflection point.

[0165] The object-side surface S7 and image-side surface S8 of the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 are all aspherical. By combining the aspherical surfaces of each lens in the optical system 10, the problem of field of view distortion in the optical system 10 can be effectively resolved. It also enables the lenses to achieve excellent optical effects while being relatively small and thin, thereby reducing the size of the optical system 10 and facilitating a miniaturized design of the optical system 10.

[0166] The first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 are all made of plastic. The use of plastic lenses can reduce the manufacturing cost of the optical system 10 and reduce the weight of the optical system 10.

[0167] Depend on Figure 7As can be seen, an infrared cutoff filter L5 is also provided on the image side of fourth lens L4 to filter out infrared light. In some embodiments, infrared cutoff filter L5 is part of optical system 10, for example, assembled to the lens barrel along with each lens. In other embodiments, infrared cutoff filter L5 is installed between optical system 10 and the photosensitive element when the optical system 10 and the photosensitive element are assembled into a camera module.

[0168] In the fourth embodiment, the effective focal length f of the optical system 10 is 4.23 mm, the aperture number FNO is 3.55, the maximum field angle (diagonal viewing angle) FOV is 38.2°, and the total optical length TTL is 5.029 mm.

[0169] In addition, the parameters of each lens of the optical system 10 are given in Table 7 and Table 8, wherein the definition of each parameter can be obtained from the first embodiment and will not be repeated here.

[0170] Table 7

[0171]

[0172] Table 8

[0173]

[0174]

[0175] From the above data we can get:

[0176]

[0177] Fifth embodiment

[0178] refer to Figure 9 and Figure 10 In the fifth embodiment, the optical system 10 includes, from the object side to the image side, a first lens L1 with positive refractive power, a second lens L2 with negative refractive power, an aperture STO, a third lens L3 with negative refractive power, and a fourth lens L4 with positive refractive power. Figure 10 It includes a spherical aberration diagram (mm), an astigmatism diagram (mm), and a distortion diagram (%) of the optical system 10 in the fifth embodiment, wherein the astigmatism diagram and the distortion diagram are data diagrams at a wavelength of 555 nm.

[0179] The object-side surface S1 of the first lens L1 is convex at the optical axis and at the circumference; the image-side surface S2 is convex at the optical axis and at the circumference.

[0180] The object-side surface S3 of the second lens L2 is convex at the optical axis and convex at the circumference; the image-side surface S4 is concave at the optical axis and concave at the circumference.

[0181] The object-side surface S5 of the third lens L3 is convex at the optical axis and concave at the circumference; the image-side surface S6 is concave at the optical axis and convex at the circumference.

[0182] The object-side surface S7 of the fourth lens L4 is convex along the optical axis and convex along the circumference, while the image-side surface S8 is concave along the optical axis and convex along the circumference. The image-side surface S8 of the fourth lens L4 has an inflection point.

[0183] The object-side surface S7 and image-side surface S8 of the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 are all aspherical. By combining the aspherical surfaces of each lens in the optical system 10, the problem of field of view distortion in the optical system 10 can be effectively resolved. It also enables the lenses to achieve excellent optical effects while being relatively small and thin, thereby reducing the size of the optical system 10 and facilitating a miniaturized design of the optical system 10.

[0184] The first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 are all made of plastic. The use of plastic lenses can reduce the manufacturing cost of the optical system 10 and reduce the weight of the optical system 10.

[0185] Depend on Figure 9 As can be seen, an infrared cutoff filter L5 is also provided on the image side of fourth lens L4 to filter out infrared light. In some embodiments, infrared cutoff filter L5 is part of optical system 10, for example, assembled to the lens barrel along with each lens. In other embodiments, infrared cutoff filter L5 is installed between optical system 10 and the photosensitive element when the optical system 10 and the photosensitive element are assembled into a camera module.

[0186] In the fifth embodiment, the effective focal length f of the optical system 10 is 4.10 mm, the aperture number FNO is 2.62, the maximum field angle (diagonal viewing angle) FOV is 38.4°, and the total optical length TTL is 5.00 mm.

[0187] In addition, the lens parameters of the optical system 10 are given in Tables 9 and 10, wherein the definitions of the parameters can be obtained from the first embodiment and are not described in detail here.

[0188] Table 9

[0189]

[0190]

[0191] Table 10

[0192]

[0193] From the above data we can get:

[0194]

[0195]

[0196] Sixth embodiment

[0197] refer to Figure 11 and Figure 12 In the sixth embodiment, the optical system 10 includes, from the object side to the image side, a first lens L1 with positive refractive power, a second lens L2 with negative refractive power, an aperture STO, a third lens L3 with negative refractive power, and a fourth lens L4 with positive refractive power. Figure 12 It includes a spherical aberration diagram (mm), an astigmatism diagram (mm), and a distortion diagram (%) of the optical system 10 in the sixth embodiment, wherein the astigmatism diagram and the distortion diagram are data diagrams at a wavelength of 555 nm.

[0198] The object-side surface S1 of the first lens L1 is convex at the optical axis and at the circumference; the image-side surface S2 is convex at the optical axis and at the circumference.

[0199] The object-side surface S3 of the second lens L2 is concave at the optical axis and convex at the circumference; the image-side surface S4 is concave at the optical axis and concave at the circumference.

[0200] The object-side surface S5 of the third lens L3 is convex at the optical axis and concave at the circumference; the image-side surface S6 is concave at the optical axis and convex at the circumference.

[0201] The object-side surface S7 of the fourth lens L4 is convex along the optical axis and concave along the circumference. The image-side surface S8 is concave along the optical axis and convex along the circumference. The image-side surface S8 of the fourth lens L4 has an inflection point.

[0202] The object-side surface S7 and image-side surface S8 of the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 are all aspherical. By combining the aspherical surfaces of each lens in the optical system 10, the problem of field of view distortion in the optical system 10 can be effectively resolved. It also enables the lenses to achieve excellent optical effects while being relatively small and thin, thereby reducing the size of the optical system 10 and facilitating a miniaturized design of the optical system 10.

[0203] The first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 are all made of plastic. The use of plastic lenses can reduce the manufacturing cost of the optical system 10 and reduce the weight of the optical system 10.

[0204] Depend on Figure 11As can be seen, an infrared cutoff filter L5 is also provided on the image side of fourth lens L4 to filter out infrared light. In some embodiments, infrared cutoff filter L5 is part of optical system 10, for example, assembled to the lens barrel along with each lens. In other embodiments, infrared cutoff filter L5 is installed between optical system 10 and the photosensitive element when the optical system 10 and the photosensitive element are assembled into a camera module.

[0205] In the sixth embodiment, the effective focal length f of the optical system 10 is 4.11 mm, the aperture number FNO is 2.48, the maximum field angle (diagonal viewing angle) FOV is 38.5°, and the total optical length TTL is 5.21 mm.

[0206] In addition, the lens parameters of the optical system 10 are given in Table 11 and Table 12, wherein the definitions of the parameters can be obtained from the first embodiment and are not described in detail here.

[0207] Table 11

[0208]

[0209]

[0210] Table 12

[0211]

[0212] From the above data we can get:

[0213]

[0214] refer to Figure 13 In one embodiment provided in the present application, the optical system 10 is assembled with the photosensitive element 210 to form a camera module 20. At this time, an infrared cutoff filter L5 is provided between the fourth lens L4 and the photosensitive element 210 in this embodiment. The photosensitive element 210 can be a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor). By adopting the optical system 10, the camera module 20 has the characteristics of a small viewing angle, a small depth of field and a blurred background. At the same time, when the camera module 20 is used for macro shooting, the relative brightness of the edge field of view will be improved, thereby effectively improving the image quality during macro shooting.

[0215] In some embodiments, the distance between the photosensitive element 210 and each lens in the optical system 10 is relatively fixed. In this case, the camera module 20 is a fixed-focus module. In other embodiments, a driving mechanism such as a voice coil motor can be provided to enable the photosensitive element 210 to move relative to each lens in the optical system 10, thereby achieving a focusing effect. In some embodiments, a driving mechanism can also be provided to drive the movement of some lenses in the optical system 10, thereby achieving an optical zoom effect.

[0216] refer to Figure 14 , some embodiments of the present application further provide an electronic device 30, and the camera module 20 is applied to the electronic device 30. Specifically, the electronic device 30 includes a shell, and the camera module 20 is installed in the shell. The electronic device 30 includes but is not limited to smart phones, smart watches, e-book readers, vehicle-mounted camera equipment, monitoring equipment, medical equipment (such as endoscopes), tablet computers, biometric equipment (such as fingerprint recognition equipment or pupil recognition equipment, etc.), PDA (Personal Digital Assistant), drones, etc. By adopting the above-mentioned camera module 20, the electronic device 30 has the characteristics of small viewing angle, small depth of field and blurred background when shooting, especially in macro shooting, it will have excellent imaging quality.

[0217] Specifically, in some embodiments, the camera module 20 is applied to a smartphone. The smartphone includes a midframe and a circuit board. The circuit board is disposed in the midframe, and the camera module 20 is mounted in the midframe of the smartphone. The photosensitive element therein is electrically connected to the circuit board. The camera module 20 can serve as a front camera module or a rear camera module of the smartphone.

[0218] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0219] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A telephoto optical system, characterized in that: There are four lenses with refractive power, including the following from object side to image side: a first lens element having positive refractive power; a second lens having refractive power; a third lens element having refractive power; and a fourth lens having refractive power, wherein the image-side surface of the fourth lens is concave at the optical axis, the object-side surface and the image-side surface of the fourth lens are both aspherical, and at least one of the object-side surface and the image-side surface of the fourth lens has an inflection point; The telephoto optical system includes an aperture, which is arranged on the object side of the first lens or between the first lens and the fourth lens; And the telephoto optical system satisfies the relationship: 0.5<SL / TTL<0.9;-1<SAG31 / CT3<0; Wherein, SL is the distance from the aperture to the imaging plane of the telephoto optical system on the optical axis, TTL is the distance from the object-side surface of the first lens to the imaging plane of the telephoto optical system on the optical axis, SAG31 is the sag height of the object-side surface of the third lens, and CT3 is the thickness of the third lens on the optical axis; The telephoto optical system also satisfies the relationship: 2.45≤FNO≤3.55; 2.33≤TTL / ImgH<2.65; Wherein, FNO is the aperture number of the telephoto optical system, and ImgH is half of the diagonal length of the effective pixel area on the imaging plane of the telephoto optical system.

2. The telephoto optical system according to claim 1, wherein: The telephoto optical system satisfies the relationship: 0.4<DT11 / DT42<0.9; DT11 is the maximum effective semi-aperture of the object-side surface of the first lens, and DT42 is the maximum effective semi-aperture of the image-side surface of the fourth lens.

3. The telephoto optical system according to claim 1, wherein: The telephoto optical system satisfies the relationship: 20mm<OBL<40mm; Wherein, OBL is the distance from the object plane of the telephoto optical system to the object side surface of the first lens on the optical axis.

4. The telephoto optical system according to claim 1, wherein: The telephoto optical system satisfies the relationship: 0.1<|SAG41| / CT4<2.0; Wherein, SAG41 is the sag height of the object side surface of the fourth lens, and CT4 is the thickness of the fourth lens on the optical axis.

5. The telephoto optical system according to claim 1, wherein: The telephoto optical system satisfies the relationship: -1≤f1 / f2≤1; Wherein, f1 is the effective focal length of the first lens, and f2 is the effective focal length of the second lens.

6. The telephoto optical system according to claim 1, wherein: The telephoto optical system satisfies the relationship: 0.5<CT3 / CT2<3.0; Wherein, CT2 is the thickness of the second lens on the optical axis.

7. The telephoto optical system according to claim 1, wherein: The telephoto optical system satisfies the relationship: 0.1<R1 / R9<0.7; Wherein, R1 is the curvature radius of the object side surface of the first lens at the optical axis, and R9 is the curvature radius of the image side surface of the fourth lens at the optical axis.

8. The telephoto optical system according to claim 1, wherein: The telephoto optical system satisfies the relationship: -3<(f2+f4) / f<1; Wherein, f2 is the effective focal length of the second lens, f4 is the effective focal length of the fourth lens, and f is the effective focal length of the telephoto optical system.

9. A camera module, characterized in that: A telephoto optical system comprising a photosensitive element and any one of claims 1 to 8, wherein the photosensitive element is arranged on the image side of the fourth lens.

10. An electronic device, characterized in that: It comprises a shell and the camera module according to claim 9, wherein the camera module is arranged in the shell.

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