Infrared collimating lens of lidar

Abstract

The application provides an infrared collimating lens of a laser radar, which comprises, in sequence from an object side to an image side along an optical axis, a first lens with negative optical power, a second lens with positive optical power, a third lens with negative optical power, a fourth lens with positive optical power, and a fifth lens with positive optical power, wherein all the lenses are spherical glass lenses, so that the reliability of the lens is greatly improved, and various optical aberrations are corrected by reasonably distributing the optical power and surface shape of each lens, the laser including the entire C band (1530nm-1565nm) can be collimated, and a better collimation effect can be achieved.

Description

Technical Field

[0001] This application belongs to the field of lidar and relates to lidar collimating lens technology, particularly to an infrared collimating lens for lidar. Background Technology

[0002] As a key optical component of lidar, the collimating lens has a significant impact on the collimation quality and echo collection efficiency of the laser beam, thus greatly affecting the ranging accuracy and reliability of the lidar. Currently, lidar commonly uses the infrared band, especially the C-band (1530nm~1565nm), which combines excellent atmospheric penetration with eye-safe characteristics, making it the preferred band for lidar systems. Therefore, the collimating lens of current lidar systems typically needs to be compatible with the infrared band.

[0003] Most existing infrared collimating lenses use plastic or glass-plastic hybrid lenses. However, plastic lenses have problems such as poor thermal stability and easy aging. They are prone to thermal defocusing when the temperature changes, making it difficult to maintain stable performance under wide temperature conditions, thus limiting long-term reliability.

[0004] While all-glass lenses offer good environmental stability and durability, the manufacturing process of glass aspherical lenses is more difficult, and glass lenses are typically spherical lenses, resulting in greater aberrations compared to aspherical lenses.

[0005] Therefore, there is an urgent need to design a new type of infrared collimating lens that combines high stability with excellent performance in the C-band to improve the reliability and adaptability of lidar in complex environments and meet the outdoor use requirements of lidar. Summary of the Invention

[0006] The purpose of this application is to provide an infrared collimating lens to solve the problem that there is currently no infrared collimating lens with high reliability and collimation performance that can be applied to lidar using C-band (1530nm~1565nm) lasers.

[0007] In a first aspect, this application provides an infrared collimating lens for a lidar, comprising, in sequence along the optical axis from the object side to the image side: a first lens having negative optical power; a second lens having positive optical power; a third lens having negative optical power; a fourth lens having positive optical power; and a fifth lens having positive optical power; wherein the first lens, the second lens, the third lens, the fourth lens, and the fifth lens are all spherical glass lenses.

[0008] In one embodiment of this application, the axial distance from the side surface of the first lens to the image plane of the infrared collimating lens is TTL, and the infrared collimating lens satisfies: 30 mm. <TTL<35 mm。

[0009] In one embodiment of this application, the infrared collimating lens collimates the light beam from the lidar and transmits it to an external object, and receives the light returned by the external object and transmits it to the lidar.

[0010] In one embodiment of this application, the object side of the first lens is convex and the image side is concave; the center thickness of the first lens on the optical axis is CT1 and the edge thickness is ET1; the first lens satisfies: CT1 / ET1>0.35.

[0011] In one embodiment of this application, the object side of the second lens is convex and the image side is concave; the center thickness of the second lens on the optical axis is CT2 and the edge thickness is ET2; the second lens satisfies: ET2 / CT2>0.35.

[0012] In one embodiment of this application, the object-side and image-side surfaces of the third lens are both concave, with a center thickness of CT3 and an edge thickness of ET3 on the optical axis; the object-side surface of the fourth lens is concave, and the image-side surface is convex, with a center thickness of CT4 and an edge thickness of ET4 on the optical axis; the object-side and image-side surfaces of the fifth lens are both convex, with a center thickness of CT5 and an edge thickness of ET5 on the optical axis; the third lens, the fourth lens, and the fifth lens satisfy: 0.8 < (CT3 + CT4 + CT5) / (ET3 + ET4 + CT5) < 1.4.

[0013] In one embodiment of this application, the effective focal length of the second lens is f2, the total effective focal length of the infrared collimating lens is f, and the infrared collimating lens satisfies: -2 < f2 / f < 2.

[0014] In one embodiment of this application, the effective focal length of the infrared collimating lens is f, and the infrared collimating lens satisfies: 14 mm < f < 18 mm.

[0015] In one embodiment of this application, the axial distance from the object side of the first lens to the image side of the fifth lens is TD, the sum of the air gaps on the optical axis between any two adjacent lenses from the first lens to the fifth lens is ∑AT, and the infrared collimating lens satisfies: 1.5 < TD / ∑AT < 3.

[0016] Secondly, this application also provides a light transmission method applied to the infrared collimating lens as described above, comprising: when the light beam is transmitted from a lidar to an external object: the light beam is converged sequentially through a fifth lens and a fourth lens, and diverged through a third lens so that the light beam passes through an aperture stop; after passing through the aperture stop, the light beam is converged through a second lens, and then diverged through a first lens to transmit to the external object; when the light beam is transmitted from the external object to the lidar: the light beam is diverged through the first lens, and converged through the second lens so that the light beam converges at the aperture stop; after passing through the aperture stop, the light beam is diverged through the third lens, and then converged sequentially through the fifth lens and the fourth lens to transmit to the lidar.

[0017] As described above, the infrared collimating lens of the lidar provided in this application includes five spherical glass lenses. Due to the high stability of glass lenses, the reliability of the infrared collimating lens is effectively improved. Moreover, the infrared collimating lens has only five lenses, which are compact in structure. By cooperating with each other to correct aberrations, the lens has good performance. Attached Figure Description

[0018] Figure 1 The diagram shown is a structural schematic of an infrared collimating lens according to an embodiment of this application.

[0019] Figure 2 The diagram shown is a schematic representation of the optical path transmission of an infrared collimating lens according to an embodiment of this application.

[0020] Figure 3 This diagram shows the diffraction circle energy curve of an infrared collimating lens according to an embodiment of this application.

[0021] Figure 4 The diagram shown is a dot plot of an infrared collimating lens as described in an embodiment of this application.

[0022] Figure 5 This diagram shows the MTF curve of an infrared collimating lens according to an embodiment of this application. Detailed Implementation

[0023] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. This application can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, unless otherwise specified, the following embodiments and features in the embodiments can be combined with each other.

[0024] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this application. Therefore, the drawings only show the components related to this application and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0025] In existing technologies, infrared collimating lenses for lidar typically employ plastic or glass-plastic hybrid lenses. However, due to the outdoor applications of lidar, the operating environment often varies significantly, such as temperature. Plastic lenses suffer from poor stability, and environmental changes can lead to a decline in lens performance. Furthermore, the performance of current infrared collimating lenses is insufficient to meet the application requirements of lidar.

[0026] Based on this, this application provides an infrared collimating lens for lidar, which uses five glass lenses for collimation, resulting in high stability, small aberrations and temperature drift, achieving good performance, compact structure, and small overall lens size, thus meeting the miniaturization requirements of lidar.

[0027] The following embodiments of this application provide an infrared collimating lens for a lidar, including but not limited to applications in the laser emission and reception processes of lidar. To facilitate understanding of the technical solution of this application, the following description will take the collimation of the laser beam emitted by the lidar as an example.

[0028] The principle and implementation method of an infrared collimating lens for a lidar according to this embodiment will be described in detail below with reference to the accompanying drawings, so that those skilled in the art can understand the infrared collimating lens of this embodiment without creative effort.

[0029] like Figures 1 to 2 As shown, this embodiment provides an infrared collimating lens for a lidar. The applicable wavelength range of the infrared collimating lens is C-band infrared light. It is a receiver-integrated lens, that is, the infrared collimating lens is used to collimate the lidar beam and transmit it to an external object, and is also used to receive light returned from the external object and transmit it to the lidar.

[0030] Specifically, such as Figure 1 As shown, the infrared collimating lens, along the optical axis from the object side to the image side, includes, in sequence: a first lens L1 with negative optical power; a second lens L2 with positive optical power; a third lens L3 with negative optical power; a fourth lens L4 with positive optical power; and a fifth lens L5 with positive optical power. Here, the object side refers to the side closer to the external object, and the image side refers to the side closer to the lidar. It should be noted that, as... Figure 2As shown, the five lenses each bear a portion of the optical power, so that the light beam is refracted in a relatively smooth manner during collimation, that is, the deflection of the light during refraction will not be too large, thereby reducing the sensitivity of the lens manufacturing tolerance.

[0031] Furthermore, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, and the fifth lens L5 are all glass lenses. Compared to plastic lenses, glass lenses have better stability, ensuring that the infrared collimating lens maintains stable performance when the environment changes, such as temperature variations, thus better meeting the needs of outdoor use. It should also be noted that because glass is less prone to aging, using five glass lenses also extends the lifespan of the infrared collimating lens.

[0032] It is worth noting that the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, and the fifth lens L5 are all spherical glass lenses.

[0033] Furthermore, spherical lenses typically exhibit some aberrations. In this embodiment, the five lenses of the infrared collimating lens work together to correct these aberrations, minimizing the overall aberrations of the infrared collimating lens and improving its overall performance. The five lenses will be described in detail below.

[0034] The first lens uses light crown glass, model H-QK3L. The first lens L1 has a convex object surface S1 and a concave image surface S2, forming a meniscus lens with negative optical power. This is used to diverge the light beam, reducing the angle between the principal ray and the optical axis (i.e., the angle between the ray at the center of the beam and the optical axis). This reduces the incident angle of the beam entering subsequent lenses, facilitating aberration calibration and ensuring the principal ray is incident on the image plane at a near-perpendicular angle. Furthermore, the first lens L1 also satisfies: CT1 / ET1 > 0.35, where CT1 is the center thickness of the first lens along the optical axis, and ET1 is the edge thickness of the first lens L1, to prevent the center of the first lens from being too thin and thus lacking sufficient strength, leading to breakage.

[0035] The second lens L2 uses lanthanum flint optical glass, model H-ZLAF90, which has a high refractive index, thus enabling it to have a large optical power. Furthermore, the second lens L2 is a meniscus lens with a large positive optical power, a convex object surface S3, and a concave image surface S4, used to converge the light beam transmitted through the first lens L2 to the stop (STOP) between the second and third lenses L2. For example, the second lens L2 also satisfies: -2 < f2 / f < 2, where f is the total effective focal length of the infrared collimating lens, and f2 is the effective focal length of the second lens L2. This allows the second lens L2 to achieve a large optical power, eliminating the divergence of the light beam by the first lens L1, ensuring the beam converges at the stop, and making the beam transmission smoother, avoiding excessive beam deflection and resulting in large aberrations.

[0036] Furthermore, the second lens L2 also satisfies: ET2 / CT2>0.35, where CT2 is the center thickness of the second lens L2 on the optical axis and ET2 is the edge thickness of the second lens L2. This setting prevents the edge of the second lens L2 from being too thin, which would cause edge chipping during processing, thereby reducing the processing difficulty of the second lens L2, effectively improving the manufacturability of the second lens L2, and reducing processing costs.

[0037] The third lens L3 uses H-QK3L glass. Both the object-side surface S6 and the image-side surface S7 of the third lens L3 are concave to widen the divergence angle of the beam after it converges at the stop, thereby increasing the overall focal length of the infrared collimating lens, preventing premature beam convergence, and providing space for beam correction to assist in aberration correction. Simultaneously, the third lens L3 can also increase the beam diameter while widening the beam divergence angle.

[0038] Both the fourth lens L4 and the fifth lens L5 are made of H-ZLAF90 glass, which has a high refractive index. The object-side surface S8 of the fourth lens L4 is concave, and the image-side surface S9 is convex. Similarly, the object-side surface S10 of the fifth lens L5 is convex, and the image-side surface S11 is convex. Both lenses have positive optical power to converge the light beam and image it on the image plane. It should be noted that by using the fourth lens L4 and the fifth lens L5, the beam converging process involves multiple refractions, resulting in a smoother converging process. This avoids excessive refraction angles during a single refraction, which could lead to a sharp increase in aberrations and thus improve the performance of the infrared collimating lens.

[0039] Furthermore, the third lens L3, the fourth lens L4, and the fifth lens L5 also satisfy: 0.8 < (CT3 + CT4 + CT5) / (ET3 + ET4 + CT5) < 1.4, where CT3 is the central thickness of the third lens L3 on the optical axis, ET3 is the edge thickness of the third lens L3, CT4 is the central thickness of the fourth lens L4 on the optical axis, ET4 is the edge thickness of the fourth lens L4, CT5 is the central thickness of the fifth lens L5 on the optical axis, and ET5 is the edge thickness of the fifth lens L5, so as to reasonably distribute the relationship between the central thickness and the edge thickness among the third lens L3, the fourth lens L4, and the fifth lens L5, thereby improving the manufacturability of the third lens L3, the fourth lens L4, and the fifth lens L5.

[0040] In some optional embodiments, the infrared collimating lens further satisfies: 30 mm < TTL < 35 mm, where TTL is the axial distance from the object side surface S1 of the first lens L1 to the image plane of the infrared collimating lens, so that the length of the infrared collimating lens is within a suitable range, avoiding excessive space occupation due to an overly long infrared collimating lens and meeting the miniaturization requirements of the lens.

[0041] In some optional embodiments, the infrared collimating lens further satisfies: 0 < TD / f < 3, where TD is the axial distance from the object side surface S1 of the first lens L1 to the image side surface S11 of the fifth lens L5, and f is the effective focal length of the infrared collimating lens, so as to avoid an overly large length of the infrared collimating lens and achieve the requirement of being thin and light.

[0042] In some optional embodiments, a protective glass G6 is further provided between the fifth lens L5 and the image plane of the infrared collimating lens to protect the light outlet inside the emitting lidar.

[0043] In some optional embodiments, the infrared collimating lens further satisfies: 14 mm < f < 18 mm to adapt to the actual application requirements of the lidar.

[0044] In some optional embodiments, the infrared collimating lens further satisfies: 1.5 < TD / ∑AT < 3, where TD is the axial distance from the object side surface S1 of the first lens L1 to the image side surface S11 of the fifth lens L5, and ∑AT is the sum of the air gaps on the optical axis between any two adjacent lenses from the first lens L1 to the fifth lens L5, so that the infrared collimating lens has a reasonable structure, avoiding an overly long overall length of the infrared collimating lens due to excessive gaps between lenses, and at the same time ensuring a certain gap between lenses to avoid interference between the front and rear lenses during the assembly process and prevent the lenses from being easily deformed and damaged.

[0045] This embodiment effectively improves the reliability of the infrared collimating lens by using spherical glass lenses for all lenses, ensuring stable performance even in changing environments and meeting the outdoor application requirements of lidar. Furthermore, this embodiment achieves excellent aberration correction by rationally allocating the optical power and surface shape of each lens, resulting in minimal overall aberrations and improved overall performance. With only five lenses, the infrared collimating lens has a compact structure and small size, meeting miniaturization requirements.

[0046] Those skilled in the art will understand that, without departing from the technical solutions claimed in this application, the number of lenses constituting the infrared collimating lens can be changed to obtain the various results and advantages described in this specification. For example, although five lenses are described as an example in the embodiments, the infrared collimating lens is not limited to including five lenses, and may include other numbers of lenses if necessary.

[0047] Furthermore, to facilitate a better understanding of the infrared collimating lens provided in this application by those skilled in the art, a specific design example of the infrared collimating lens will be described in detail below.

[0048] Specifically, such as Figure 1 The diagram shown is a structural schematic of the infrared collimating lens described in this embodiment. The infrared collimating lens includes, in sequence along the optical axis from the object side to the image side: a first lens L1, a second lens L2, an aperture stop (STOP), a third lens L3, a fourth lens L4, a fifth lens L5, and a protective glass G6.

[0049] Furthermore, the first lens L1 has negative optical power, with its object side S1 being convex and its image side S2 being concave.

[0050] The second lens L2 has positive optical power, with its object side S3 being convex and its image side S4 being concave.

[0051] The third lens L3 has negative optical power, and both its object side S6 and image side S7 are concave.

[0052] The fourth lens L4 has positive optical power, with its object side S8 being concave and its image side S9 being convex.

[0053] The fifth lens L5 has positive optical power, and both its object side S10 and image side S11 are convex surfaces.

[0054] The protective glass G6 has an object side S12 and an image side S13.

[0055] The incident light rays pass sequentially through the surfaces S1 to S13 from the object side and finally form an image on the image side, or they pass sequentially through the surfaces S13 to S1 from the image side and finally illuminate the external object on the object side.

[0056] Furthermore, the first, second, third, fourth, and fifth lenses are all spherical glass lenses to improve the reliability of the infrared collimating lens while reducing the difficulty of lens manufacturing.

[0057] It should be noted that since spherical lenses typically have large aberrations, this embodiment achieves aberration correction between lenses by reasonably allocating the optical power and surface shape of each lens, thereby reducing the overall aberrations of the infrared collimating lens, including but not limited to spherical aberration, coma, astigmatism, field curvature, temperature drift, etc., and improving the overall performance of the infrared collimating lens.

[0058] Specifically, Table 1 below shows the specific settings of each lens surface type and optical power in this embodiment:

[0059]

[0060] Table 1

[0061] Wherein, OBJ represents the object plane; STO represents the aperture stop; and IMA represents the image plane.

[0062] Furthermore, the infrared collimating lens provided in this embodiment is specifically configured as follows: the total lens length is 32.23 mm; the image-side F-number is 1.97; the total effective focal length f is 15.5 mm; the half field of view is 15.2°; the entrance pupil diameter is 8 mm; the maximum image height is 4.185 mm; and the image-side numerical aperture is 0.25.

[0063] Furthermore, the infrared collimating lens provided in this embodiment is specifically configured as follows: ET1 / CT1=0.462, where ET1 is the edge thickness of the first lens and CT1 is the center thickness of the first lens on the optical axis; CT2 / ET2=0.525, where CT2 is the center thickness of the second lens on the optical axis and ET2 is the edge thickness of the second lens; f2 / f=0.757, where f2 is the effective focal length of the second lens and f is the total effective focal length of the infrared collimating lens; TD / f=1.642, where TD is the axial distance from the object side of the first lens to the image side of the fifth lens and f is the total effective focal length of the infrared collimating lens; TD / ∑AT=2.121, where ∑AT is the sum of the air gaps on the optical axis between any two adjacent lenses from the first lens to the fifth lens.

[0064] Based on this, the infrared collimating lens provided in this embodiment, by reasonably allocating the optical power and surface shape of each lens, enables the infrared collimating lens to use only five lenses, and enables the overall aberrations of the infrared collimating lens, including but not limited to spherical aberration, coma, astigmatism, field curvature, temperature drift, etc., to achieve excellent results. As a result, the infrared collimating lens has good performance, a compact structure, and a small size.

[0065] To facilitate those skilled in the art to understand the overall performance of the infrared collimating lens in this embodiment, a simulation is performed using the specific settings of the infrared collimating lens described in this embodiment, and a detailed explanation is provided based on the obtained simulation results.

[0066] like Figure 3 The diagram shows the diffraction entry energy curves of the infrared collimating lens described in this embodiment. The top curve represents the entry energy fraction at an ambient temperature of 20°C. The curve corresponding to the diffraction limit represents the lens's theoretical optimal performance. As shown in the diagram, the curves corresponding to 0°, 6°, and 15° are closely clustered with the curve corresponding to the diffraction limit. Based on this, the infrared collimating lens exhibits good performance at an ambient temperature of 20°C. The middle curve represents the entry energy fraction at an ambient temperature of -40°C, and the bottom curve represents the entry energy fraction at an ambient temperature of 80°C. Compared to 20°C, the curves corresponding to each field of view are relatively dispersed from the curve corresponding to the diffraction limit, but still maintain a high degree of clustering. Based on this, the infrared collimating lens maintains good performance within an ambient temperature range from -40°C to 80°C. That is, the infrared collimating lens provided in this embodiment has a small temperature drift, meeting the needs of outdoor use in environments with significant variations, and exhibits good performance at a normal ambient temperature, i.e., 20°C.

[0067] like Figure 4 The diagram shown is a dot plot of the infrared collimating lens described in this embodiment. The top dot plot is for an ambient temperature of 20°C. As can be seen, the spot size in all field-of-view dot plots is close to the Airy disk, indicating that the infrared collimating lens has good performance across all field-of-view angles. The middle dot plot is for an ambient temperature of -40°C, and the bottom dot plot is for an ambient temperature of 80°C. Compared to 20°C, the dot plots for each field-of-view angle show a trend of increased distortion, but overall, the spot size in the dot plots remains close to the Airy disk. This means that the performance degradation of the infrared collimating lens remains within an acceptable range as the ambient temperature changes from -40°C to 80°C. Therefore, the infrared collimating lens provided in this embodiment not only has good performance at 20°C but also exhibits minimal temperature drift, maintaining good performance across a temperature range from -40°C to 80°C.

[0068] like Figure 5The figure shows a schematic diagram of the MTF (Modulation Transfer Function, also known as OTF) curve described in this embodiment. The topmost curve is the MTF curve at an ambient temperature of 20°C. As can be seen, the 0° meridional curve and the 0° sagittal curve completely overlap. Simultaneously, the 0° curve is close to the diffraction-limited curve, indicating that on-axis aberrations, such as spherical aberration, are well corrected. The curves corresponding to the 6° and 15° fields of view shift downwards overall, meaning the MTF value decreases. Off-axis aberrations increase slowly, the meridional curve separates from the sagittal curve, and astigmatism gradually increases, but all remain relatively small. The middle curve is the MTF curve at an ambient temperature of -40°C, and the bottom curve is the MTF curve at an ambient temperature of 80°C. Compared to 20°C, the curves corresponding to each field of view are relatively dispersed from the diffraction-limited curve, but the degree of dispersion remains small, indicating that the temperature drift of the infrared collimating lens is small.

[0069] In summary, the infrared collimating lens provided in this application effectively improves the reliability of the infrared collimating lens by setting all lenses as spherical glass lenses, meeting the outdoor use requirements of lidar. Furthermore, by rationally allocating the optical power and surface shape of each lens, the overall aberration of the infrared collimating lens is minimized, resulting in good performance. Moreover, the overall structure is compact, meeting the miniaturization requirements.

[0070] The descriptions of the processes or structures corresponding to the above figures each have their own emphasis. For parts of a process or structure that are not described in detail, please refer to the relevant descriptions of other processes or structures.

[0071] The above embodiments are merely illustrative of the principles and effects of this application and are not intended to limit this application. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this application. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this application should still be covered by the claims of this application.

Claims

1. An infrared collimating lens for a lidar system, characterized in that, Along the optical axis from the object side to the image side, the following are included in sequence: A first lens with negative optical power has a convex object-side surface with a radius of curvature of 44.39 mm and a concave image-side surface with a radius of curvature of 9.03 mm; a second lens with positive optical power has a convex object-side surface with a radius of curvature of 10.11 mm and a concave image-side surface with a radius of curvature of 90.69 mm; a third lens with negative optical power has a concave object-side surface with a radius of curvature of -6.02 mm and a concave image-side surface with a radius of curvature of 19.91 mm; a fourth lens with positive optical power has a concave object-side surface with a radius of curvature of -30.09 mm and a convex image-side surface with a radius of curvature of -11.32 mm; and a fifth lens with positive optical power has a convex object-side surface with a radius of curvature of 13.60 mm and a convex image-side surface with a radius of curvature of -167.24 mm. The first lens, second lens, third lens, fourth lens, and fifth lens are all spherical glass lenses; an aperture stop is provided between the second lens and the third lens; the axial distance from the object-side surface of the first lens to the image plane of the infrared collimating lens is TTL; and the infrared collimating lens satisfies the following condition: 30 mm. <TTL<35 mm。 2. The infrared collimating lens according to claim 1, characterized in that, The infrared collimating lens collimates the light beam from the lidar and transmits it to an external object, and receives the light returned by the external object and transmits it to the lidar.

3. The infrared collimating lens according to claim 1, characterized in that, The first lens has a center thickness of CT1 and an edge thickness of ET1 on the optical axis; the first lens satisfies: CT1 / ET1>0.

35.

4. The infrared collimating lens according to claim 1, characterized in that, The second lens has a center thickness of CT2 and an edge thickness of ET2 on the optical axis; the second lens satisfies: ET2 / CT2>0.

35.

5. The infrared collimating lens according to claim 1, characterized in that, The third lens has a center thickness of CT3 and an edge thickness of ET3 on the optical axis; the fourth lens has a center thickness of CT4 and an edge thickness of ET4 on the optical axis; the fifth lens has a center thickness of CT5 and an edge thickness of ET5 on the optical axis; the third lens, the fourth lens, and the fifth lens satisfy the following condition: 0.8 < (CT3 + CT4 + CT5) / (ET3 + ET4 + CT5) < 1.

4.

6. The infrared collimating lens according to claim 1, characterized in that, The effective focal length of the second lens is f2, the total effective focal length of the infrared collimating lens is f, and the infrared collimating lens satisfies: -2 < f2 / f < 2.

7. The infrared collimating lens according to claim 1, characterized in that, The effective focal length of the infrared collimating lens is f, and the infrared collimating lens satisfies the following condition: 14 mm < f < 18 mm.

8. The infrared collimating lens according to claim 1, characterized in that, The axial distance from the object side of the first lens to the image side of the fifth lens is TD, and the sum of the air gaps on the optical axis between any two adjacent lenses from the first lens to the fifth lens is ∑AT. The infrared collimating lens satisfies: 1.5 < TD / ∑AT < 3.

9. A light transmission method, applied to an infrared collimating lens as described in any one of claims 1 to 8, characterized in that, include: When the light beam is transmitted from the lidar to an external object: the light beam is converged by the fifth lens and the fourth lens in sequence, and then diverged by the third lens so that the light beam passes through the aperture. After the light beam passes through the aperture, it is converged by the second lens and then diverged by the first lens to be transmitted to the external object. When the light beam is transmitted from the external object to the lidar: the light beam diverges through the first lens and converges through the second lens to converge the light beam at the aperture. After the light beam passes through the aperture, it diverges through the third lens and then converges through the fourth and fifth lenses in sequence before being transmitted to the lidar.

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