CN112987252B

CN112987252B - Optical system, infrared receiving module and electronic equipment

Info

Publication number: CN112987252B
Application number: CN202110244092.8A
Authority: CN
Inventors: 邹金华; 李明; 刘彬彬
Original assignee: Jiangxi Jingchao Optical Co Ltd
Current assignee: Jiangxi Jingchao Optical Co Ltd
Priority date: 2021-03-05
Filing date: 2021-03-05
Publication date: 2023-11-07
Anticipated expiration: 2041-03-05
Also published as: CN112987252A

Abstract

The invention relates to an optical system, an infrared receiving module and electronic equipment. The optical system sequentially comprises from an object side to an image side along an optical axis: a first lens element with positive refractive power having a concave image-side surface at a paraxial region; a second lens element with refractive power having a concave object-side surface at a paraxial region; a third lens element with refractive power having a concave image-side surface at a paraxial region; and the optical system satisfies the following conditional expression: FNO is more than or equal to 1.4 and less than or equal to 1.8; TT/f is more than or equal to 0.8 and less than or equal to 1.0; wherein FNO is the f-number of the optical system, TT is the distance from the object side surface of the first lens to the image side surface of the third lens on the optical axis, and f is the effective focal length of the optical system. The optical system has sufficient light flux and can meet the requirement of miniaturization design.

Description

Optical system, infrared receiving module and electronic equipment

Technical Field

The present invention relates to the field of infrared detection, and in particular, to an optical system, an infrared receiving module, and an electronic device.

Background

With the rapid development of technologies such as Time of Flight (TOF) and laser detection and ranging (Light Detection and Ranging, liDAR), infrared light is increasingly used in the fields of face unlocking, automobile autopilot, man-machine interface and game, industrial machine vision and measurement, security monitoring and imaging systems, and the like. As a result, the market demand for optical systems for receiving infrared light is also increasing, and there is an urgent need for optical systems that have a sufficient light flux and that can meet a miniaturized design.

Disclosure of Invention

Based on this, it is necessary to provide an optical system, an infrared receiving module and an electronic device to provide a sufficient amount of light and meet the demand of miniaturization design.

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

a first lens element with positive refractive power having a concave image-side surface at a paraxial region;

a second lens element with refractive power having a concave object-side surface at a paraxial region;

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

and the optical system satisfies the following conditional expression:

1.4≤FNO≤1.8；

0.8≤TT/f≤1.0；

wherein FNO is the f-number of the optical system, TT is the distance from the object side surface of the first lens to the image side surface of the third lens on the optical axis, and f is the effective focal length of the optical system.

In the optical system, the image side surface of the first lens is concave at the paraxial region, which is favorable for light divergence and deflection, and the deflection angle born by each lens of the image side of the first lens can be reduced, so that the deflection angle of the light at each lens is favorable for balancing. The first lens element with positive refractive power is beneficial to shortening the total system length of the optical system so as to meet the requirement of miniaturization design. The object side surface of the second lens is concave at the paraxial region, which is favorable for correcting the field curvature and astigmatism of the optical system, thereby improving the imaging quality of the optical system. The third lens element has a concave image-side surface at a paraxial region thereof, which is beneficial to improving field curvature of the optical system.

When the FNO is more than or equal to 1.4 and less than or equal to 1.8, the light quantity of the optical system can be increased, so that the optical system can acquire clear detail information of a shot object in a low light environment, and meanwhile, the brightness of an edge view field is improved, and the imaging quality of the optical system is improved. When the TT/f is more than or equal to 0.8 and less than or equal to 1.0, the ratio of the TT to the effective focal length of the optical system can be reasonably configured, the total system length of the optical system is reduced, the miniaturized design is realized, and meanwhile, light rays are well converged on an imaging surface of the optical system.

In one embodiment, the optical system satisfies the following conditional expression:

0.6≤tan(HFOV)*(SD32/IMGH)≤1.1；

wherein HFOV is half of the maximum field angle of the optical system, SD32 is the maximum effective half aperture of the image side surface of the third lens, and IMGH is half of the image height corresponding to the maximum field angle of the optical system. When the above conditional expression is satisfied, the view angle of the optical system, the maximum effective half aperture of the image side surface of the third lens and the half image height of the optical system can be reasonably configured, so that the optical system is balanced in large view angle and miniaturized design, and the miniaturization design is realized, and the increase of the view angle of the optical system is facilitated; in addition, the focal depth of shooting and imaging of the optical system is increased, so that the acquisition of the stereoscopic profile information of the object is facilitated. The lower limit of the conditional expression is not beneficial to enlarging the view angle of the optical system while realizing the miniaturization design, thereby being not beneficial to the optical system to have layering sense on the object imaging in a large view field range. Exceeding the upper limit of the above conditional expression, the angle of view of the optical system is too large, making it difficult to correct distortion aberration of the optical system, resulting in the situation of unclear imaging and serious distortion of the image.

0.10mm≤T12+T23≤1.1mm；

wherein T12 is a distance between the image side surface of the first lens element and the object side surface of the second lens element on the optical axis, and T23 is a distance between the image side surface of the second lens element and the object side surface of the third lens element on the optical axis. When the above conditional expression is satisfied, the space between two adjacent lenses of the optical system can be reasonably configured, so that the total system length of the optical system is further shortened, and the miniaturization design of the optical system is facilitated. Below the lower limit of the above conditional expression, the interval between two adjacent lenses is too small, which results in increased sensitivity of the optical system and is unfavorable for assembly of the optical system. Exceeding the upper limit of the above conditional expression, the interval between two adjacent lenses is too large, and the two adjacent lenses need to be connected by connecting elements such as an additional spacer component, thereby increasing the cost of the optical system and being unfavorable for the miniaturization design of the optical system.

1.0≤f1/f≤18.0；

wherein f1 is the effective focal length of the first lens. When the above conditional expression is satisfied, the ratio of the effective focal length of the first lens to the effective focal length of the optical system can be reasonably configured, so that the first lens provides enough positive refractive power for the optical system, which is favorable for converging light rays. When the upper limit of the above condition is exceeded, the first lens element provides insufficient positive refractive power to the optical system, resulting in a decrease in light collecting ability of the optical system. Below the lower limit of the above conditional expression, the first lens element provides excessive positive refractive power for the optical system, which is not beneficial to the correction of aberration generated by the second lens element and the third lens element on the first lens element as a whole, thereby reducing the imaging quality of the optical system.

-45≤R3/CT2≤-1；

wherein R3 is the radius of curvature of the object side surface of the second lens on the optical axis, and CT2 is the thickness of the second lens on the optical axis. When the above conditional expression is satisfied, the ratio of the curvature radius of the object side surface of the second lens at the optical axis to the center thickness of the second lens can be reasonably configured, so that the second lens can effectively correct the curvature of field and astigmatism of the optical system, and the imaging quality of the optical system is improved. Below the lower limit of the above conditional expression, the surface shape of the second lens is too gentle, which is unfavorable for correcting the curvature of field and astigmatism of the optical system. Exceeding the upper limit of the above conditional expression, the object side surface of the second lens element tends to be excessively curved near the maximum effective aperture, resulting in increased stray light of the optical system, thereby reducing the imaging quality of the optical system.

0.80mm≤FFL≤1.05mm；

wherein FFL is the shortest distance between the image side surface of the third lens and the imaging surface of the optical system in the optical axis direction. The lower limit of the condition is exceeded, so that the optical system has enough assembly and debugging space during assembly, and the assembly yield of the optical system is improved; meanwhile, the focal depth of the optical system is also increased, so that the optical system can acquire more depth information of the object. Below the upper limit of the above conditional expression, the axial dimension of the optical system is favorably compressed, thereby facilitating the miniaturization design of the optical system.

0.9≤f23/f≤2.5；

wherein f23 is a combined focal length of the second lens and the third lens. When the above conditional expression is satisfied, the ratio of the combined focal length of the second lens and the third lens to the effective focal length of the optical system can be reasonably configured, which is favorable for shortening the total length of the optical system, and meanwhile, the excessive increase of the higher-order spherical aberration of the optical system can be avoided, thereby being favorable for improving the imaging quality of the optical system. Exceeding the upper limit of the above conditional expression, the combined focal length of the second lens and the third lens is too large, which is disadvantageous in shortening the total system length of the optical system while correcting the spherical aberration of the optical system. Below the lower limit of the above conditional expression, the combined focal length of the second lens element and the third lens element is too small, so that the refractive power of the second lens element and the third lens element is too strong, and the spherical aberration is easily overcorrected, thereby reducing the imaging quality of the optical system.

1.2≤(R2+R1)/(R2-R1)≤50；

wherein R1 is a radius of curvature of the object side surface of the first lens element at the optical axis, and R2 is a radius of curvature of the image side surface of the first lens element at the optical axis. When the above conditional expression is satisfied, the radii of curvature of the object side surface and the image side surface of the first lens element at the optical axis can be reasonably configured, and the optical deflection angle borne by the first lens element can be reasonably distributed by matching the surface shape of the image side surface of the first lens element at the paraxial region, so that the maximum field angle of the optical system can be enlarged; meanwhile, the astigmatism of the off-axis view field can be corrected, and the imaging quality of the optical system is improved.

An infrared receiving module, comprising a photosensitive element and the optical system according to any of the above embodiments, wherein the photosensitive element is disposed on an image side of the optical system. The optical system is adopted in the infrared receiving module, which is beneficial to increasing the light quantity of the infrared receiving module and is beneficial to the miniaturization design of the infrared receiving module.

An electronic device comprises a shell and the infrared receiving module, wherein the infrared receiving module is arranged on the shell. The infrared receiving module is adopted in the electronic equipment, so that the light quantity of the electronic equipment is increased, and the miniaturization design of the electronic equipment is facilitated.

Drawings

Fig. 1 is a schematic structural view of an optical system in a first embodiment of the present application;

FIG. 2 is a longitudinal spherical aberration, astigmatism and distortion chart of an optical system according to a first embodiment of the present application;

FIG. 3 is a schematic diagram of an optical system according to a second embodiment of the present application;

FIG. 4 is a longitudinal spherical aberration, astigmatism and distortion chart of an optical system according to a second embodiment of the present application;

fig. 5 is a schematic structural view of an optical system in a third embodiment of the present application;

FIG. 6 is a longitudinal spherical aberration, astigmatism and distortion chart of an optical system according to a third embodiment of the present application;

Fig. 7 is a schematic structural view of an optical system in a fourth embodiment of the present application;

FIG. 8 is a longitudinal spherical aberration, astigmatism and distortion chart of an optical system according to a fourth embodiment of the present application;

fig. 9 is a schematic structural view of an optical system in a fifth embodiment of the present application;

FIG. 10 is a longitudinal spherical aberration, astigmatism and distortion chart of an optical system according to a fifth embodiment of the present application;

fig. 11 is a schematic structural view of an optical system in a sixth embodiment of the present application;

FIG. 12 is a longitudinal spherical aberration diagram, an astigmatic diagram, and a distortion diagram of an optical system according to a sixth embodiment of the present application;

FIG. 13 is a schematic diagram of an infrared receiving module according to an embodiment of the application;

fig. 14 is a schematic diagram of an electronic device according to an embodiment of the application.

Detailed Description

In order that the above objects, features and advantages of the application will be readily understood, a more particular description of the application will be rendered by reference to the appended drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. The present application may be embodied in many other forms than described herein and similarly modified by those skilled in the art without departing from the spirit of the application, whereby the application is not limited to the specific embodiments disclosed below.

In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the device or element being referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the present invention.

Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present invention, the meaning of "plurality" means at least two, for example, two, three, etc., unless specifically defined otherwise.

In the present invention, unless explicitly specified and limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; either directly or indirectly, through intermediaries, or both, may be in communication with each other or in interaction with each other, unless expressly defined otherwise. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.

In the present invention, unless expressly stated or limited otherwise, a first feature "up" or "down" a second feature may be the first and second features in direct contact, or the first and second features in indirect contact via an intervening medium. Moreover, a first feature being "above," "over" and "on" a second feature may be a first feature being directly above or obliquely above the second feature, or simply indicating that the first feature is level higher than the second feature. The first feature being "under", "below" and "beneath" the second feature may be the first feature being directly under or obliquely below the second feature, or simply indicating that the first feature is less level than the second feature.

It will be understood that when an element is referred to as being "fixed" or "disposed" on another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and the like are used herein for illustrative purposes only and are not meant to be the only embodiment.

Referring to fig. 1, in some embodiments of the present application, the optical system 100 includes, in order from an object side to an image side, a first lens L1, a second lens L2, and a third lens L3. Specifically, the first lens element L1 includes an object-side surface S1 and an image-side surface S2, the second lens element L2 includes an object-side surface S3 and an image-side surface S4, and the third lens element L3 includes an object-side surface S5 and an image-side surface S6.

The first lens element L1 with positive refractive power is beneficial to shortening the overall system length of the optical system 100 to meet the requirement of miniaturization design. The image side surface S2 of the first lens element L1 is concave at the paraxial region 110, which is beneficial to light divergence and deflection, and can reduce the deflection angle borne by each lens element of the image side of the first lens element L1, thereby balancing the deflection angle of light at each lens element. The second lens element L2 and the third lens element L3 each have refractive power. The object side surface S3 of the second lens element L2 is concave at the paraxial region 110, which is beneficial to correcting curvature of field and astigmatism of the optical system 100, thereby improving the imaging quality of the optical system 100. The image-side surface S6 of the third lens element L3 is concave at the paraxial region 110, which is beneficial to improving the curvature of field of the optical system 100.

In some embodiments, the object-side surface S5 and the image-side surface S6 of the third lens element L3 are aspheric, which is beneficial to improving the flexibility of the design of the third lens element L3, effectively correcting the spherical aberration of the optical system 100, and improving the imaging quality. In some embodiments, at least one of the object-side surface S5 and the image-side surface S6 of the third lens L3 has a inflection point, which is beneficial to correct aberration of the vertical axis field of view, and further improves imaging quality of the optical system 100.

In some embodiments, the second lens element L2 and the third lens element L3 have positive refractive power, which is beneficial to converging light, thereby shortening the overall system length of the optical system 100 and further meeting the requirements of miniaturized design. In other embodiments, the second lens element L2 with positive refractive power and the third lens element L3 with negative refractive power cooperate with the positive refractive power of the first lens element L1 to balance the overall system length and the angle of view, thereby shortening the overall system length and expanding the angle of view of the optical system 100.

In addition, in some embodiments, the optical system 100 is provided with a stop STO, which may be disposed on the object side of the first lens L1 or on the object side of the first lens L1. In some embodiments, the optical system 100 further includes an infrared band-pass filter L4 disposed on the image side of the third lens L3, and the infrared band-pass filter L4 includes an object side surface S7 and an image side surface S8. Further, the optical system 100 further includes an image plane S9 located at the image side of the third lens L3, where the image plane S9 is an imaging plane of the optical system 100, and the incident light can be imaged on the image plane S9 after being adjusted by the first lens L1, the second lens L2 and the third lens L3. It is understood that the infrared band pass filter L4 is used for transmitting infrared light, for example, in some embodiments, the infrared band pass filter L4 may allow infrared light of 930nm-950nm to pass. Thus, in some embodiments, the optical system 100 may be used to receive infrared light, and may be particularly useful in techniques employing infrared light detection such as TOF, liDAR, and the like. Specifically, the optical system 100 may be used in the fields of face unlocking, automatic driving of a car, man-machine interface and game, industrial machine vision and measurement, security monitoring and imaging system, etc., to meet the requirement of receiving infrared light.

In some embodiments, the object side and the image side of each lens of the optical system 100 are both aspheric. The adoption of the aspheric structure can improve the flexibility of lens design, effectively correct spherical aberration and improve imaging quality. In other embodiments, the object side and image side of each lens of the optical system 100 may be spherical. It should be noted that the above embodiments are merely examples of some embodiments of the present application, and in some embodiments, the surfaces of the lenses in the optical system 100 may be aspherical or any combination of spherical surfaces.

In some embodiments, the materials of the lenses in the optical system 100 may be glass or plastic. The plastic lens can reduce the weight of the optical system 100 and the production cost, and the smaller size of the optical system is matched to realize the light and thin design of the optical system. The lens made of glass material provides the optical system 100 with excellent optical performance and high temperature resistance. It should be noted that the materials of the lenses in the optical system 100 may be any combination of glass and plastic, and are not necessarily all glass or all plastic.

It should be noted that the first lens L1 does not mean that there is only one lens, and in some embodiments, there may be two or more lenses in the first lens L1, where the two or more lenses can form a cemented lens, a surface of the cemented lens closest to the object side may be referred to as an object side surface S1, and a surface closest to the image side may be referred to as an image side surface S2. Alternatively, the first lens L1 does not have a cemented lens, but the distance between the lenses is relatively constant, and the object side surface of the lens closest to the object side is the object side surface S1, and the image side surface of the lens closest to the image side is the image side surface S2. In addition, the number of lenses in the second lens L2 or the third lens L3 in some embodiments may be greater than or equal to two, and a cemented lens may be formed between any adjacent lenses, or may be a non-cemented lens.

Further, in some embodiments, the optical system 100 satisfies the conditional expression: FNO is more than or equal to 1.4 and less than or equal to 1.8; where FNO is the f-number of optical system 100. Specifically, the FNO may be: 1.4, 1.42, 1.46, 1.48, 1.50, 1.51, 1.55, 1.58, 1.62, or 1.76. When the above conditional expression is satisfied, the light flux of the optical system 100 can be increased, so that the optical system 100 can obtain clear detailed information of the object under the weak light environment, and meanwhile, the brightness of the edge view field is improved, thereby improving the imaging quality of the optical system 100.

In some embodiments, the optical system 100 satisfies the conditional expression: TT/f is more than or equal to 0.8 and less than or equal to 1.0; where TT is the distance between the object side surface S1 of the first lens element L1 and the image side surface S6 of the third lens element L3 on the optical axis 110, and f is the effective focal length of the optical system 100. Specifically, TT/f may be: 0.855, 0.864, 0.877, 0.896, 0.915, 0.926, 0.955, 0.967, 0.971 or 0.992. When the above conditional expression is satisfied, the ratio of the TT to the effective focal length of the optical system 100 can be reasonably configured, which is favorable for shortening the total system length of the optical system 100, realizing a miniaturized design, and simultaneously, being favorable for better converging light on the imaging surface of the optical system 100.

In some embodiments, the optical system 100 satisfies the conditional expression: tan (HFOV) is 0.6.ltoreq.SD 32/IMGH.ltoreq.1.1; the HFOV is half of the maximum angle of view of the optical system 100, the SD32 is the maximum effective half aperture of the image side surface S6 of the third lens L3, and the IMGH is half of the image height corresponding to the maximum angle of view of the optical system 100. Specifically, tan (HFOV) × (SD 32/IMGH) may be: 0.636, 0.673, 0.710, 0.725, 0.788, 0.843, 0.852, 0.901, 0.963, or 1. When the above conditional expression is satisfied, the view angle of the optical system 100, the maximum effective half aperture of the image side surface S6 of the third lens L3, and the half image height of the optical system 100 can be reasonably arranged, so that the optical system 100 is balanced between a large view angle and a miniaturized design, and the miniaturized design is realized, and the increase of the view angle of the optical system 100 is facilitated; in addition, the depth of focus of the photographing imaging of the optical system 100 is advantageously increased, thereby facilitating acquisition of stereoscopic profile information of an object. Below the lower limit of the above conditional expression, the miniaturization design is realized while the viewing angle of the optical system 100 is not favorably enlarged, so that the optical system 100 is not favorably provided with a layering sense for imaging an object in a large viewing field range. Exceeding the upper limit of the above conditional expression, the angle of view of the optical system 100 is too large, making it difficult to correct distortion aberration of the optical system 100, resulting in the situation that imaging is unclear and the image is severely deformed.

It should be noted that, in some embodiments, the optical system 100 may match a photosensitive element having a rectangular photosensitive surface, and the imaging surface of the optical system 100 coincides with the photosensitive surface of the photosensitive element. At this time, the effective pixel area on the imaging plane of the optical system 100 has a horizontal direction and a diagonal direction, and the HFOV can be understood as a half of the maximum viewing angle of the diagonal direction of the optical system 100, and the ImgH can be understood as a half of the length of the effective pixel area on the imaging plane of the optical system 100 in the diagonal direction.

In some embodiments, the optical system 100 satisfies the conditional expression: t12+t23 is more than or equal to 0.10mm and less than or equal to 1.1mm; wherein T12 is a distance between the image side surface S2 of the first lens element L1 and the object side surface S3 of the second lens element L2 on the optical axis 110, and T23 is a distance between the image side surface S4 of the second lens element L2 and the object side surface S5 of the third lens element L3 on the optical axis 110. Specifically, t12+t23 may be: 0.179, 0.252, 0.367, 0.412, 0.557, 0.623, 0.771, 0.823, 0.996 or 1.065, in mm. When the above conditional expression is satisfied, the space between two adjacent lenses of the optical system 100 can be reasonably configured, so that the total system length of the optical system 100 is further shortened, and the miniaturization design of the optical system 100 is facilitated. Below the lower limit of the above conditional expression, the interval between the adjacent two lenses is too small, resulting in an increase in sensitivity of the optical system 100, which is unfavorable for assembly of the optical system 100. Beyond the upper limit of the above conditional expression, the interval between two adjacent lenses is too large, and the two adjacent lenses need to be connected by a connecting element such as an additional spacer member, which increases the cost of the optical system 100 and is disadvantageous for the miniaturized design of the optical system 100.

In some embodiments, the optical system 100 satisfies the conditional expression: f1/f is more than or equal to 1.0 and less than or equal to 18.0; wherein f1 is the effective focal length of the first lens L1. Specifically, f1/f may be: 1.34, 2.01, 3.25, 5.36, 7.15, 8.33, 10.21, 12.07, 15.15 or 16.22. When the above conditional expression is satisfied, the ratio of the effective focal length of the first lens L1 to the effective focal length of the optical system 100 can be reasonably configured, so that the first lens L1 provides sufficient positive refractive power for the optical system 100, which is beneficial to converging light rays. When the upper limit of the above condition is exceeded, the first lens element L1 provides insufficient positive refractive power to the optical system 100, resulting in a decrease in the light collecting capability of the optical system 100. Below the lower limit of the above condition, the positive refractive power provided by the first lens element L1 for the optical system 100 is too large, which is not beneficial to the correction of the aberration generated by the second lens element L2 and the third lens element L3 on the whole to the first lens element L1, thereby reducing the imaging quality of the optical system 100, and meanwhile, the surface shape of the first lens element L1 is excessively curved, which is not beneficial to the formation of the first lens element L1, thereby reducing the manufacturing yield of the first lens element L1.

In some embodiments, the optical system 100 satisfies the conditional expression: -45 is less than or equal to R3/CT2 is less than or equal to-1; wherein R3 is a radius of curvature of the object side surface S3 of the second lens element L2 at the optical axis 110, and CT2 is a thickness of the second lens element L2 on the optical axis 110. Specifically, R3/CT2 may be: -40, -32.01, -21.65, -11.33, -9.54, -8.03, -6.52, -5.36, -3.99 or-2.14. When the above conditional expression is satisfied, the ratio of the radius of curvature of the object side surface S3 of the second lens element L2 at the optical axis 100 to the center thickness of the second lens element L2 can be reasonably configured, so that the second lens element L2 can effectively correct the curvature of field and astigmatism of the optical system 100, and improve the imaging quality of the optical system 100. Below the lower limit of the above condition, the surface shape of the second lens L2 is too gentle, which is unfavorable for correcting the curvature of field and astigmatism of the optical system 100. Exceeding the upper limit of the above condition, the object side surface S3 of the second lens element L2 tends to be excessively curved near the maximum effective aperture, resulting in increased stray light of the optical system 100, thereby reducing the imaging quality of the optical system 100.

In some embodiments, the optical system 100 satisfies the conditional expression: FFL is more than or equal to 0.80mm and less than or equal to 1.05mm; wherein FFL is the shortest distance between the image side surface S6 of the third lens L3 and the imaging surface of the optical system 100 in the direction of the optical axis 110. Specifically, the FFL may be: 0.84, 0.86, 0.87, 0.89, 0.91, 0.93, 0.95, 0.97, 1.01 or 1.03, in mm. Exceeding the lower limit of the above conditional expression is beneficial to enabling the optical system 100 to have enough assembly and debugging space during assembly, thereby improving the assembly yield of the optical system 100; at the same time, it is also beneficial to increase the focal depth of the optical system 100, so that the optical system 100 can acquire more depth information of the object. Below the upper limit of the above conditional expression, the axial dimension of the optical system 100 is favorably compressed, thereby facilitating the miniaturization design of the optical system 100.

In some embodiments, the optical system 100 satisfies the conditional expression: f23/f is more than or equal to 0.9 and less than or equal to 2.5; wherein f23 is a combined focal length of the second lens L2 and the third lens L3. Specifically, f23/f may be: 0.975, 1.325, 1.561, 1.685, 1.703, 1.872, 1.963, 2.015, 2.225, or 2.313. When the above conditional expression is satisfied, the ratio of the combined focal length of the second lens L2 and the third lens L3 to the effective focal length of the optical system 100 can be reasonably configured, which is favorable for shortening the total system length of the optical system 100, and meanwhile, the excessive increase of the higher-order spherical aberration of the optical system 100 can be avoided, thereby being favorable for improving the imaging quality of the optical system 100. Exceeding the upper limit of the above conditional expression, the combined focal length of the second lens L2 and the third lens L3 is too large, which is disadvantageous in shortening the overall system length of the optical system 100 while correcting the spherical aberration of the optical system 100. Below the lower limit of the above condition, if the combined focal length of the second lens element L2 and the third lens element L3 is too small, the refractive power of the second lens element L2 and the third lens element L3 as a whole is too strong, which is prone to cause excessive correction of spherical aberration, and thus the imaging quality of the optical system 100 is degraded.

In some embodiments, the optical system 100 satisfies the conditional expression: (R2+R1)/(R2-R1) is less than or equal to 1.2 and less than or equal to 50; wherein R1 is a radius of curvature of the object side surface S1 of the first lens element L1 at the optical axis 110, and R2 is a radius of curvature of the image side surface S2 of the first lens element L1 at the optical axis 110. Specifically, (r2+r1)/(R2-R1) may be: 1.575, 1.785, 1.993, 2.052, 2.133, 2.287, 10.637, 19.852, 30.647, or 47.328. When the above conditional expression is satisfied, the radii of curvature of the object-side surface S1 and the image-side surface S2 of the first lens element L1 at the optical axis 110 can be reasonably configured, and the optical deflection angle borne by the first lens element L1 can be reasonably distributed in cooperation with the surface shape of the image-side surface S2 of the first lens element L1 at the paraxial region 110, thereby being beneficial to expanding the maximum field angle of the optical system 100; and is also beneficial to correcting the astigmatism of the off-axis field of view, thereby improving the imaging quality of the optical system 100.

From the above description of the embodiments, more particular embodiments and figures are set forth below in detail.

First embodiment

Referring to fig. 1 and 2, fig. 1 is a schematic structural diagram of an optical system 100 in a first embodiment, and the optical system 100 includes, in order from an object side to an image side, a stop STO, a first lens element L1 with positive refractive power, a second lens element L2 with negative refractive power, and a third lens element L3 with positive refractive power. Fig. 2 is a graph of longitudinal spherical aberration, astigmatism and distortion of the optical system 100 in the first embodiment, from left to right, where the reference wavelength of the astigmatism graph and the distortion graph is 940nm, and other embodiments are the same.

The object side surface S1 of the first lens element L1 is convex at the paraxial region 110 and convex at the peripheral region;

the image-side surface S2 of the first lens element L1 is concave at the paraxial region 110 and concave at the peripheral region;

the object side surface S3 of the second lens element L2 is concave at the paraxial region 110 and concave at the peripheral region;

the image-side surface S4 of the second lens element L2 is concave at a paraxial region 110 and convex at a peripheral region;

the object side surface S5 of the third lens element L3 is convex at a paraxial region 110 and concave at a peripheral region;

the image-side surface S6 of the third lens element L3 is concave at a paraxial region 110 and convex at a peripheral region.

The object side surface and the image side surface of the first lens element L1, the second lens element L2, and the third lens element L3 are aspheric.

It should be noted that in the present application, when one surface of the lens is described as being convex at the paraxial region 110 (the central region of the surface), it is understood that the region of the surface of the lens near the optical axis 110 is convex. When describing a surface of a lens as concave at the circumference, it is understood that the surface is concave in the area near the maximum effective radius. For example, when the surface is convex at the paraxial region 110 and also convex at the circumference, the shape of the surface from the center (the intersection of the surface and the optical axis 110) to the edge direction may be purely convex; or first transition from a convex shape in the center to a concave shape and then become convex near the maximum effective radius. The various shape structures (concave-convex relationship) of the surface are not fully revealed here only for the purpose of explaining the relationship at the optical axis 110 with the circumference, but other cases may be deduced from the above examples.

The first lens L1, the second lens L2 and the third lens L3 are all made of plastic.

Further, the optical system 100 satisfies the conditional expression: fno=1.4; where FNO is the f-number of optical system 100. When the above conditional expression is satisfied, the light flux of the optical system 100 can be increased, so that the optical system 100 can obtain clear detailed information of the object under the weak light environment, and meanwhile, the brightness of the edge view field is improved, thereby improving the imaging quality of the optical system 100.

The optical system 100 satisfies the conditional expression: TT/f=0.968; where TT is the distance between the object side surface S1 of the first lens element L1 and the image side surface S6 of the third lens element L3 on the optical axis 110, and f is the effective focal length of the optical system 100. When the above conditional expression is satisfied, the ratio of the TT to the effective focal length of the optical system 100 can be reasonably configured, which is favorable for shortening the total system length of the optical system 100, realizing a miniaturized design, and simultaneously, being favorable for better converging light on the imaging surface of the optical system 100.

The optical system 100 satisfies the conditional expression: tan (HFOV) × (SD 32/IMGH) =0.7; the HFOV is half of the maximum angle of view of the optical system 100, the SD32 is the maximum effective half aperture of the image side surface S6 of the third lens L3, and the IMGH is half of the image height corresponding to the maximum angle of view of the optical system 100. When the above conditional expression is satisfied, the view angle of the optical system 100, the maximum effective half aperture of the image side surface S6 of the third lens L3, and the half image height of the optical system 100 can be reasonably arranged, so that the optical system 100 is balanced between a large view angle and a miniaturized design, and the miniaturized design is realized, and the increase of the view angle of the optical system 100 is facilitated; in addition, the focal depth of the photographing imaging of the optical system 100 is increased, so that the acquisition of the stereoscopic profile information of the object is facilitated; furthermore, correction of distortion aberration of the optical system 100 is facilitated, so that the conditions of unclear imaging and serious deformation of the image are avoided.

The optical system 100 satisfies the conditional expression: t12+t23=1.065 mm; wherein T12 is a distance between the image side surface S2 of the first lens element L1 and the object side surface S3 of the second lens element L2 on the optical axis 110, and T23 is a distance between the image side surface S4 of the second lens element L2 and the object side surface S5 of the third lens element L3 on the optical axis 110. When the above conditional expression is satisfied, the space between two adjacent lenses of the optical system 100 can be reasonably configured, so that the total system length of the optical system 100 is further shortened, and the miniaturization design of the optical system 100 is facilitated; at the same time, the sensitivity of the optical system 100 is reduced, thereby facilitating the assembly of the optical system 100; in addition, the cost of the optical system 100 can be reduced.

The optical system 100 satisfies the conditional expression: f1/f=1.41; wherein f1 is the effective focal length of the first lens L1. When the above conditional expression is satisfied, the ratio of the effective focal length of the first lens L1 to the effective focal length of the optical system 100 can be reasonably configured, so that the first lens L1 provides sufficient positive refractive power for the optical system 100, which is beneficial to converging light rays; in addition, the positive refractive power provided by the first lens element L1 for the optical system 100 is not excessively large, which is beneficial to correcting the aberration generated by the first lens element L1 by the second lens element L2 and the third lens element L3, thereby improving the imaging quality of the optical system 100; meanwhile, the surface shape of the first lens L1 is not excessively bent, so that the forming of the first lens L1 is facilitated, and the manufacturing yield of the first lens L1 is improved.

The optical system 100 satisfies the conditional expression: r3/CT 2= -9.03; wherein R3 is a radius of curvature of the object side surface S3 of the second lens element L2 at the optical axis 110, and CT2 is a thickness of the second lens element L2 on the optical axis 110. When the above conditional expression is satisfied, the ratio of the radius of curvature of the object side surface S3 of the second lens L2 at the optical axis 100 to the center thickness of the second lens L2 can be reasonably configured, so that the second lens L2 can effectively correct the curvature of field and the astigmatism of the optical system 100, and meanwhile, the stray light of the optical system 100 can be reduced, thereby improving the imaging quality of the optical system 100.

The optical system 100 satisfies the conditional expression: ffl=0.94 mm; wherein FFL is the shortest distance between the image side surface S6 of the third lens L3 and the imaging surface of the optical system 100 in the direction of the optical axis 110. Exceeding the lower limit of the above conditional expression is beneficial to enabling the optical system 100 to have enough assembly and debugging space during assembly, thereby improving the assembly yield of the optical system 100; at the same time, it is also beneficial to increase the focal depth of the optical system 100, so that the optical system 100 can acquire more depth information of the object. Below the upper limit of the above conditional expression, the axial dimension of the optical system 100 is favorably compressed, thereby facilitating the miniaturization design of the optical system 100.

The optical system 100 satisfies the conditional expression: f23/f=2.313; wherein f23 is a combined focal length of the second lens L2 and the third lens L3. When the above conditional expression is satisfied, the ratio of the combined focal length of the second lens L2 and the third lens L3 to the effective focal length of the optical system 100 can be reasonably configured, which is favorable for shortening the total system length of the optical system 100, and meanwhile, the excessive increase of the higher-order spherical aberration of the optical system 100 can be avoided, thereby being favorable for improving the imaging quality of the optical system 100.

The optical system 100 satisfies the conditional expression: (r2+r1)/(R2-R1) =1.877; wherein R1 is a radius of curvature of the object side surface S1 of the first lens element L1 at the optical axis 110, and R2 is a radius of curvature of the image side surface S2 of the first lens element L1 at the optical axis 110. When the above conditional expression is satisfied, the radii of curvature of the object-side surface S1 and the image-side surface S2 of the first lens element L1 at the optical axis 110 can be reasonably configured, and the optical deflection angle borne by the first lens element L1 can be reasonably distributed in cooperation with the surface shape of the image-side surface S2 of the first lens element L1 at the paraxial region 110, thereby being beneficial to expanding the maximum field angle of the optical system 100; and is also beneficial to correcting the astigmatism of the off-axis field of view, thereby improving the imaging quality of the optical system 100.

In addition, various parameters of the optical system 100 are given in table 1. The image plane S9 in table 1 can be understood as the imaging plane of the optical system 100. The elements from the object plane (not shown) to the image plane S9 are arranged in the order of the elements from top to bottom in table 1. The radius Y in table 1 is the radius of curvature of the object or image side of the corresponding surface number at the optical axis 110. 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 110, and the second value is the distance from the image side surface of the lens element to the rear surface of the image side direction on the optical axis 110.

Note that in this embodiment and the following embodiments, the optical system 100 may not be provided with the infrared band-pass filter L4, but the distance from the image side surface S6 of the third lens L3 to the image surface S9 remains unchanged.

In the first embodiment, the effective focal length f=2.87 mm, the f-number fno=1.40, half of the maximum field angle hfov=39.7° and the optical total length ttl=3.98 mm of the optical system 100.

The reference wavelength of the focal length of each lens is 940nm, and the reference wavelength of the refractive index and Abbe number of each lens is 587.56nm, and other embodiments are the same.

TABLE 1

Further, the aspherical coefficients of the image side or object side of each lens of the optical system 100 are given in table 2. Wherein the plane numbers S1-S6 represent the image side surfaces or the object side surfaces S1-S6, respectively. And K-a20 from top to bottom respectively represent types of aspherical coefficients, where K represents a conic coefficient, A4 represents four times an aspherical coefficient, A6 represents six times an aspherical coefficient, A8 represents eight times an aspherical coefficient, and so on. In addition, the aspherical coefficient formula is as follows:

where Z is the distance from the corresponding point on the aspheric surface to the plane tangential to the surface vertex, r is the distance from the corresponding point on the aspheric surface to the optical axis 110, c is the curvature of the aspheric vertex, k is the conic coefficient, ai is the coefficient corresponding to the i-th higher term in the aspheric surface formula.

TABLE 2

In addition, fig. 2 includes a longitudinal spherical aberration diagram (Longitudinal Spherical Aberration) of the optical system 100, which shows the deviation of the focal point of light rays of different wavelengths after passing through the lens. The ordinate of the longitudinal spherical aberration diagram represents the normalized pupil coordinates (Normalized Pupil Coordinator) from the pupil center to the pupil edge, and the abscissa represents the distance (in mm) from the imaging plane to the intersection of the light ray with the optical axis 110. As can be seen from the longitudinal spherical aberration diagram, the degree of focus deviation of the light beams with the respective wavelengths in the first embodiment tends to be uniform, and the diffuse spots or the halos in the imaging picture are effectively suppressed. Fig. 2 also includes a field profile (ASTIGMATIC FIELD CURVES) of the optical system 100, wherein the S-curve represents the sagittal field profile at 940nm and the T-curve represents the meridional field profile at 940 nm. As can be seen from the figure, the field curvature of the optical system 100 is small, the field curvature and astigmatism of each field of view are well corrected, and the center and the edge of the field of view have clear imaging. Fig. 2 also includes a DISTORTION map (DISTORTION) of the optical system 100, in which it is seen that the DISTORTION of the image caused by the main beam is small and the imaging quality of the system is good.

Second embodiment

Referring to fig. 3 and 4, fig. 3 is a schematic structural diagram of an optical system 100 in a second embodiment, and the optical system 100 includes, in order from an object side to an image side, a stop STO, a first lens element L1 with positive refractive power, a second lens element L2 with negative refractive power, and a third lens element L3 with positive refractive power. Fig. 2 is a graph showing, in order from left to right, longitudinal spherical aberration, astigmatism, and distortion of the optical system 100 in the second embodiment.

the object side surface S5 of the third lens element L3 is convex at the paraxial region 110 and convex at the peripheral region;

In addition, the parameters of the optical system 100 are given in table 3, and the definition of the parameters can be obtained in the first embodiment, which is not described herein.

TABLE 3 Table 3

Further, the aspheric coefficients of the image side or the object side of each lens of the optical system 100 are given in table 4, and the definition of each parameter can be obtained from the first embodiment, which is not described herein.

TABLE 4 Table 4

And, according to the above-provided parameter information, the following data can be deduced:

FNO	1.650	R3/CT2	-40.000
				TT/f	0.992	FFL	0.840mm
T12+T23	0.470mm	f23/f	1.397
				tan(HFOV)*(SD32/IMGH)	0.787	(R2+R1)/(R2-R1)	2.225
f1/f	2.070

in addition, as can be seen from the aberration diagram in fig. 4, the longitudinal spherical aberration, curvature of field and distortion of the optical system 100 are all well controlled, so that the optical system 100 of this embodiment has good imaging quality.

Third embodiment

Referring to fig. 5 and 6, fig. 5 is a schematic structural diagram of an optical system 100 in a third embodiment, where the optical system 100 includes, in order from an object side to an image side, a stop STO, a first lens element L1 with positive refractive power, a second lens element L2 with positive refractive power, and a third lens element L3 with positive refractive power. Fig. 6 is a graph showing longitudinal spherical aberration, astigmatism and distortion of the optical system 100 in the third embodiment in order from left to right.

the image-side surface S4 of the second lens element L2 is convex at the paraxial region 110 and convex at the peripheral region;

In addition, the parameters of the optical system 100 are given in table 5, and the definition of the parameters can be obtained in the first embodiment, which is not described herein.

TABLE 5

Further, the aspheric coefficients of the image side or the object side of each lens of the optical system 100 are given in table 6, and the definition of each parameter can be obtained from the first embodiment, which is not described herein.

TABLE 6

FNO	1.760	R3/CT2	-2.140
				TT/f	0.855	FFL	0.950mm
T12+T23	0.395mm	f23/f	2.010
				tan(HFOV)*(SD32/IMGH)	0.636	(R2+R1)/(R2-R1)	1.575
f1/f	1.340

in addition, as is clear from the aberration diagram in fig. 6, the longitudinal spherical aberration, curvature of field, and distortion of the optical system 100 are all well controlled, so that the optical system 100 of this embodiment has good imaging quality.

Fourth embodiment

Referring to fig. 7 and 8, fig. 7 is a schematic structural diagram of an optical system 100 in a fourth embodiment, and the optical system 100 includes, in order from an object side to an image side, a stop STO, a first lens element L1 with positive refractive power, a second lens element L2 with positive refractive power, and a third lens element L3 with negative refractive power. Fig. 8 is a graph showing longitudinal spherical aberration, astigmatism and distortion of the optical system 100 in the fourth embodiment in order from left to right.

The object side surface S1 of the first lens element L1 is convex at a paraxial region 110 and concave at a peripheral region;

the image-side surface S2 of the first lens element L1 is concave at a paraxial region 110 and convex at a peripheral region;

In addition, the parameters of the optical system 100 are given in table 7, and the definition of the parameters can be obtained in the first embodiment, which is not described herein.

TABLE 7

Further, the aspheric coefficients of the image side or the object side of each lens in the optical system 100 are given in table 8, and the definition of each parameter can be obtained from the first embodiment, which is not described herein.

TABLE 8

FNO	1.650	R3/CT2	-7.290
				TT/f	0.874	FFL	1.030mm
T12+T23	0.230mm	f23/f	0.975
				tan(HFOV)*(SD32/IMGH)	0.761	(R2+R1)/(R2-R1)	47.328
f1/f	16.220

in addition, as is clear from the aberration diagram in fig. 8, the longitudinal spherical aberration, curvature of field, and distortion of the optical system 100 are all well controlled, so that the optical system 100 of this embodiment has good imaging quality.

Fifth embodiment

Referring to fig. 9 and 10, fig. 9 is a schematic structural diagram of an optical system 100 in a fifth embodiment, and the optical system 100 includes, in order from an object side to an image side, a stop STO, a first lens element L1 with positive refractive power, a second lens element L2 with positive refractive power, and a third lens element L3 with negative refractive power. Fig. 10 is a graph showing longitudinal spherical aberration, astigmatism and distortion of the optical system 100 in the fifth embodiment in order from left to right.

the object side surface S3 of the second lens element L2 is concave at the paraxial region 110 and convex at the peripheral region;

the image-side surface S4 of the second lens element L2 is convex at a paraxial region 110 and concave at a peripheral region;

In addition, the parameters of the optical system 100 are given in table 9, and the definition of the parameters can be obtained in the first embodiment, which is not described herein.

TABLE 9

Further, the aspheric coefficients of the image side or the object side of each lens of the optical system 100 are given in table 10, and the definition of each parameter can be obtained from the first embodiment, which is not described herein.

Table 10

FNO	1.650	R3/CT2	-3.210
				TT/f	0.948	FFL	0.840mm
T12+T23	0.206mm	f23/f	1.463
				tan(HFOV)*(SD32/IMGH)	1.000	(R2+R1)/(R2-R1)	1.790
f1/f	2.120

in addition, as is clear from the aberration diagram in fig. 10, the longitudinal spherical aberration, curvature of field, and distortion of the optical system 100 are all well controlled, so that the optical system 100 of this embodiment has good imaging quality.

Sixth embodiment

Referring to fig. 11 and 12, fig. 11 is a schematic structural diagram of an optical system 100 in a sixth embodiment, and the optical system 100 includes, in order from an object side to an image side, a stop STO, a first lens element L1 with positive refractive power, a second lens element L2 with positive refractive power, and a third lens element L3 with negative refractive power. Fig. 12 is a graph showing longitudinal spherical aberration, astigmatism and distortion of the optical system 100 in the sixth embodiment in order from left to right.

In addition, the parameters of the optical system 100 are given in table 11, and the definition of the parameters can be obtained in the first embodiment, which is not described herein.

TABLE 11

Further, the aspheric coefficients of the image side or the object side of each lens of the optical system 100 are given in table 12, and the definition of each parameter can be obtained from the first embodiment, which is not described herein.

Table 12

FNO	1.650	R3/CT2	-3.010
				TT/f	0.930	FFL	0.950
T12+T23	0.179mm	f23/f	1.472
				tan(HFOV)*(SD32/IMGH)	0.802	(R2+R1)/(R2-R1)	2.093
f1/f	2.050

in addition, as is clear from the aberration diagram in fig. 12, the longitudinal spherical aberration, curvature of field, and distortion of the optical system 100 are all well controlled, so that the optical system 100 of this embodiment has good imaging quality.

Referring to fig. 13, in some embodiments, the optical system 100 may be assembled with the photosensitive element 210 to form an infrared receiving module 200. At this time, the photosensitive surface of the photosensitive element 210 can be regarded as the image surface S9 of the optical system 100. The infrared receiving module 200 may further be provided with an infrared band-pass filter L4, where the infrared band-pass filter L4 is disposed between the image side surface S6 and the image surface S9 of the third lens L3. Specifically, the photosensitive element 210 may be a charge coupled element (Charge Coupled Device, CCD) or a complementary metal oxide semiconductor device (Complementary Metal-Oxide Semiconductor Sensor, CMOS Sensor). More specifically, the photosensitive element 210 may be an infrared image sensor, and the infrared receiving module 200 is configured to receive infrared light and image the infrared light on the photosensitive element 210. The optical system 100 is adopted in the infrared receiving module 200, which is beneficial to increasing the light flux of the infrared receiving module 200 and is beneficial to miniaturization design of the infrared receiving module 200.

Referring to fig. 13 and 14, in some embodiments, the infrared receiving module 200 may be applied to an electronic device 300, which includes a housing 310, and the infrared receiving module 200 is disposed on the housing 310. Specifically, the electronic device 300 may be, but is not limited to, a portable telephone, a video phone, a smart phone, an electronic book reader, a vehicle-mounted image pickup device such as a car recorder, or a wearable device such as a smart watch. In addition, the electronic device 300 may employ TOF or LiDAR technology, and may be used in fields such as face unlocking, auto-driving, human-machine interface and game, industrial machine vision and measurement, security monitoring and imaging systems, and the like. In some embodiments, the electronic device 300 further comprises an emission module 320, the emission module 320 being configured to emit infrared light, for example, infrared light in the wavelength range of 930nm-950 nm. For example, when the electronic device 300 adopts the TOF technology, the electronic device 300 may be used to obtain depth information of the object to be measured, and the infrared ray emitted by the emission module 320 is received by the infrared receiving module 200 after being reflected by the object to be measured. The infrared receiving module 200 is adopted in the electronic equipment 300, which is beneficial to increasing the light quantity of the electronic equipment 300 and is beneficial to miniaturization design of the electronic equipment 300.

The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

The above examples illustrate only a few embodiments of the invention, which are described in detail and are not to be construed as limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.

Claims

1. An optical system, characterized in that the number of lenses with refractive power in the optical system is three, and the optical system sequentially comprises, from an object side to an image side along an optical axis:

and the optical system satisfies the following conditional expression:

1.4≤FNO≤1.8；

0.8≤TT/f≤1.0；

0.9≤f23/f≤2.5；

wherein FNO is the f-number of the optical system, TT is the distance between the object side surface of the first lens and the image side surface of the third lens on the optical axis, f is the effective focal length of the optical system, and f23 is the combined focal length of the second lens and the third lens.

2. The optical system according to claim 1, wherein the following conditional expression is satisfied:

0.6≤tan(HFOV)*(SD32/IMGH)≤1.1；

wherein HFOV is half of the maximum field angle of the optical system, SD32 is the maximum effective half aperture of the image side surface of the third lens, and IMGH is half of the image height corresponding to the maximum field angle of the optical system.

3. The optical system according to claim 1, wherein the following conditional expression is satisfied:

0.10mm≤T12+T23≤1.1mm；

wherein T12 is a distance between the image side surface of the first lens element and the object side surface of the second lens element on the optical axis, and T23 is a distance between the image side surface of the second lens element and the object side surface of the third lens element on the optical axis.

4. The optical system according to claim 1, wherein the following conditional expression is satisfied:

1.0≤f1/f≤18.0；

Wherein f1 is the effective focal length of the first lens.

5. The optical system according to claim 1, wherein the following conditional expression is satisfied:

-45≤R3/CT2≤-1；

wherein R3 is the radius of curvature of the object side surface of the second lens on the optical axis, and CT2 is the thickness of the second lens on the optical axis.

6. The optical system according to claim 1, wherein the following conditional expression is satisfied:

0.80mm≤FFL≤1.05mm；

wherein FFL is the shortest distance between the image side surface of the third lens and the imaging surface of the optical system in the optical axis direction.

7. The optical system of claim 1, wherein the object side and the image side of the first lens, the second lens, and the third lens are aspheric.

8. The optical system according to claim 1, wherein the following conditional expression is satisfied:

1.2≤(R2+R1)/(R2-R1)≤50；

wherein R1 is a radius of curvature of the object side surface of the first lens element at the optical axis, and R2 is a radius of curvature of the image side surface of the first lens element at the optical axis.

9. An infrared receiving module comprising a photosensitive element and the optical system of any one of claims 1-8, the photosensitive element being disposed on an image side of the optical system.

10. An electronic device comprising a housing and the infrared receiving module of claim 9, wherein the infrared receiving module is disposed on the housing.