CN217639519U

CN217639519U - Small laser radar transmitting system

Info

Publication number: CN217639519U
Application number: CN202220397318.8U
Authority: CN
Inventors: 谭凤泽; 郝成龙; 朱健
Original assignee: Shenzhen Metalenx Technology Co Ltd
Current assignee: Shenzhen Metalenx Technology Co Ltd
Priority date: 2022-02-25
Filing date: 2022-02-25
Publication date: 2022-10-21
Anticipated expiration: 2032-02-25

Abstract

The application provides a small laser radar transmitting system, belongs to optics technical field. The system comprises a first superlens, a second superlens, a third superlens and a light source; the first super lens, the second super lens and the third super lens are sequentially arranged on the light emitting side of the light source along the same optical axis; the ratio of the distance from the light emitting surface of the light source to the third super lens to the equivalent focal length of the system is less than or equal to 1; the ratio of the distance from the light emitting surface of the light source to the first super lens to the equivalent focal length is less than or equal to 0.1. The system reduces the number of lenses, the total length and the working distance in the laser radar transmitting system through the first super lens, the second super lens and the third super lens, reduces the size of the laser radar transmitting system, and promotes the miniaturization of the laser radar. The small laser radar transmitting system provided by the embodiment of the application has the advantages of light weight, small size, simple structure and low cost.

Description

Small laser radar transmitting system

Technical Field

The application relates to the technical field of optics, in particular to a small laser radar transmitting system.

Background

Lidar (Laser detection and Ranging) is a radar system that detects characteristic quantities such as a position, a velocity, and the like of an object by emitting a Laser beam. In general, a lidar includes a transmitting system, a receiving system, an information processing system, and a scanning system. The laser radar transmitting system comprises an optical system and a light source, wherein the optical system and the light source are composed of a plurality of groups of refraction lenses.

In order to reduce the size of the laser radar, the Total Track Length (TTL) and the Working Distance (WD) of the laser radar transmitting system need to be suppressed as much as possible. The total system length of the laser radar transmitting system refers to the distance from the center of the last lens in the transmitting system to the center of the light emitting surface of the light source along the emergent direction. Therefore, the smaller the lens thickness, the smaller the number of lenses, and the shorter the spacing between lenses, the smaller the total system length.

However, in order to ensure the optical performance of the lidar, at least four groups of refractive lenses are required in the conventional lidar transmission system, which makes it difficult to reduce the overall length of the system, and this also makes the miniaturization of the conventional lidar transmission system fall into a bottleneck.

SUMMERY OF THE UTILITY MODEL

In order to solve the technical problem that the total length of a compression system falls into a bottleneck in the prior art, the embodiment of the application provides a small laser radar transmitting system, which comprises a first super lens, a second super lens, a third super lens and a light source;

the first super lens, the second super lens and the third super lens are sequentially arranged on the light emitting side of the light source in the same optical axis manner;

the ratio of the distance from the light emitting surface of the light source to the third super lens to the equivalent focal length of the system is less than or equal to 1;

the ratio of the distance from the light emitting surface of the light source to the first super lens to the equivalent focal length is less than or equal to 0.1.

Optionally, an initial light beam emitted by the light source is sequentially modulated by the first superlens, the second superlens and the third superlens, and is converted into a second light beam;

the divergence angle of the second light beam is less than or equal to 0.1 °.

Optionally, the light source includes a plurality of point light sources arranged in an array.

Optionally, the divergence angle of the point light source is 20 ° full angle.

Optionally, the distance between adjacent point light sources in the light sources is 20 μm.

Optionally, the light source includes 21 point light sources arranged in an array.

Optionally, the thicknesses of the first superlens, the second superlens and the third superlens are less than or equal to 0.3mm.

Optionally, the diameter of the third superlens is less than or equal to 2mm.

Optionally, the distance from the light source to the first superlens is greater than 0.2mm and less than 0.8mm;

the distance between the first superlens and the second superlens is more than 0.5mm and less than 2.0mm;

and the distance between the second super lens and the third super lens is more than 1.5mm and less than 2.5mm.

Optionally, the system further comprises a MEMS galvanometer;

the initial light beam emitted by the light source is modulated by the first super lens, the second super lens and the third super lens in sequence and then is converted into a second light beam;

the divergence angle of the second light beam is less than or equal to 0.1 °;

and the second light beam enters the MEMS galvanometer and is scanned through the movement of the MEMS galvanometer.

Optionally, the system further comprises a mirror;

the reflecting mirror is located between the third super lens and the MEMS galvanometer and used for reflecting the second light to the MEMS galvanometer.

Optionally, the first superlens, the second superlens and the third superlens each comprise a substrate and a nanostructure layer;

the nanostructure layer comprises nanostructures arranged in an array;

the nanostructure layer is disposed on the substrate.

Optionally, the period of the nanostructure is greater than or equal to 300nm and less than or equal to 3 μm.

Optionally, the height of the nanostructures is greater than or equal to 300nm, less than or equal to 3 μm.

Optionally, the nanostructure is a polarization insensitive structure.

Optionally, the nanostructure is a polarization-dependent structure.

The small laser radar transmitting system provided by the embodiment of the application at least has the following beneficial effects:

the small laser radar transmitting system provided by the embodiment of the application reduces the number of lenses, the total length of the system and the working distance in the laser radar transmitting system through the first super lens, the second super lens and the third super lens, reduces the size of the laser radar transmitting system and promotes the miniaturization of the laser radar.

The small laser radar transmitting system provided by the embodiment of the application has the advantages of light weight, small size, simple structure and low cost.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments or the background art of the present application, the drawings required to be used in the embodiments or the background art of the present application will be described below.

FIG. 1 is a schematic diagram illustrating an alternative structure of a compact lidar transmission system provided by an embodiment of the present application;

FIG. 2 is a schematic diagram illustrating an alternative structure of a compact lidar transmission system provided by an embodiment of the application;

FIG. 3 is a schematic diagram illustrating an alternative structure of a compact lidar transmission system provided by an embodiment of the application;

FIG. 4 is a schematic diagram illustrating an alternative structure of a nanostructure provided by an embodiment of the present application;

FIG. 5 illustrates a schematic diagram of yet another alternative structure for nanostructures provided by embodiments of the present application;

FIG. 6 is a schematic diagram illustrating an alternative structure of a superstructure unit provided by an embodiment of the present application;

FIG. 7 shows a schematic diagram of yet another alternative structure of a superstructure unit provided by embodiments of the present application;

FIG. 8 is a schematic diagram illustrating yet another alternative structure of a superstructure unit provided by embodiments of the present application;

fig. 9 is a graph showing transmittance versus phase modulation for an alternative nanostructure provided by an embodiment of the present application.

The reference numerals in the drawings denote:

100-first superlens; 200-a second superlens; 300-third superlens; 400-light source.

Detailed Description

To facilitate an understanding of the present application, the present application will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present application are shown in the drawings. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete. Also, in the drawings, the thickness, ratio and size of the components are exaggerated for clarity of explanation.

It will be understood that 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 "mounted," "one end," "the other end," and the like are used herein for illustrative purposes only.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, "a," "an," "the," and "at least one" do not denote a limitation of quantity, but rather are intended to include both the singular and the plural, unless the context clearly dictates otherwise. For example, "a component" means the same as "at least one component" unless the context clearly dictates otherwise. "at least one of" should not be construed as limited to the quantity "one". The term "and/or" includes any and all combinations of one or more of the associated listed items.

The meaning of "comprising" or "comprises" indicates the property, quantity, step, operation, component, part or combination thereof, but does not exclude other properties, quantities, steps, operations, components, parts or combination thereof.

Embodiments are described herein with reference to cross-section illustrations that are idealized embodiments. Variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments described herein should not be construed as limited to the particular shapes of regions as illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, a region shown or described as flat may typically have rough and/or nonlinear features. Also, the acute angles shown may be rounded. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of a region and are not intended to limit the scope of the claims.

The Working Distance (WD) of a lidar transmission system is the Distance from the light emitting surface of the light source to the surface of the first lens in the transmission system in the emission direction. In addition to reducing the number of lenses, reducing the thickness of the lenses, and shortening the spacing between the lenses, the volume of the lidar transmission system may be reduced by reducing the working distance. It should be noted that the smaller the working distance, the more advantageous the integration of the lidar transmission system.

The collimation degree of the emergent light is one of important indexes for evaluating the optical performance of the laser radar transmitting system. The size of the laser radar transmitting system is reduced by reducing the total length and the working distance of the system, and the premise of ensuring the optical performance is needed. The existing laser radar transmitting system is generally composed of at least four groups of refraction lenses, and the structure is difficult to simultaneously meet the requirements of small total length of the system, small working distance and high collimation degree. However, with the use of laser radar on the ground in the consumer electronics and automotive electronics industries, especially in the application in the special fields such as unmanned aerial vehicles, the miniaturization of laser radar is a problem that needs to be solved.

Therefore, a laser radar transmitting system satisfying a small overall length of the system, a small working distance and a high degree of collimation at the same time is needed.

More specifically, a superlens is a specific application of a supersurface that modulates the phase, amplitude, and polarization of incident light by periodically arranged subwavelength-sized nanostructures.

Fig. 1 and fig. 2 show a compact lidar transmission system provided by an embodiment of the present application. As shown in fig. 1 and 2, the system includes a first superlens 100, a second superlens 200, a third superlens 300, and a light source 400. The first superlens 100, the second superlens 200, and the third superlens 300 are sequentially disposed on a light emitting side of the light source 400 along the optical axis. Specifically, the ratio of the distance from the light emitting surface of the light source 400 to the third superlens 300 to the equivalent focal length of the system is less than or equal to 1. The ratio of the distance from the light emitting surface of the light source 400 to the first superlens 100 to the equivalent focal length of the system is less than or equal to 0.2. The equivalent focal length of the system refers to the equivalent focal length of the optical system composed of the first superlens 100, the second superlens 200, and the third superlens 300.

The initial light beam emitted from the light source 400 is modulated by the first superlens 100, the second superlens 200, and the third superlens 300 in sequence, and then converted into a second light beam, which is emitted from the third superlens 300. Wherein the divergence angle ψ of the second light beam is less than or equal to 0.1 °.

According to the embodiment of the present application, the light source 400 is optionally a point light source including a plurality of point light sources arranged in an array, for example, a point array light source. Preferably, the pitch δ of adjacent point sources in the light source 400 is 20 μm. Further, the divergence angle of the point source in light source 400 is 20 ° in total. In an alternative embodiment, light source 400 comprises 21 point light sources.

In some alternative embodiments, the diameter of the third superlens 300 is less than or equal to 2mm, such that the third superlens 300 converts more of the light beam into the second light beam.

Illustratively, the thicknesses of the first, second, and

third superlenses

100, 200, and 300 are less than or equal to 0.3mm.

Optionally, the distance from the light source 400 to the first superlens 100 is greater than 0.2mm and less than 0.8mm. According to an embodiment of the present application, optionally, the distance between the first superlens 100 and the second superlens 200 is greater than 0.5mm and less than 2.0mm. In some exemplary embodiments, the second superlens 200 and the third superlens 300 are spaced apart by more than 1.5mm and less than 2.5mm.

In yet another alternative embodiment, as shown in FIG. 3, the compact lidar transmission system further includes a MEMS galvanometer 500. The MEMS galvanometer 500 is a Micro-Electro-Mechanical System (MEMS) based Micro-actuatable optical element. The second light beam emitted from the third superlens 300 is reflected by the MEMS galvanometer 500 to be scanned in the irradiation direction. MEMS galvanometer 500 reduces the overall length of the compact lidar transmission system as compared to conventional scanning devices. In some alternative embodiments, the compact lidar transmission system further includes a mirror located between the third superlens 300 and the MEMS galvanometer 500 for reflecting the second beam to the MEMS galvanometer.

In still other embodiments of the present application, the compact lidar emission system provided by the embodiments of the present application further includes a mirror. The mirror transmits a second beam to the MEMS galvanometer 500, thereby achieving scanning in the lidar illumination direction by movement of the MEMS galvanometer 500.

Next, a description will be given of a superlens employed in the embodiment of the present application. The first, second, and

third superlenses

100, 200, and 300 in the embodiment of the present application each include a substrate and a nanostructure layer; the nanostructure layer comprises nanostructures arranged in an array; the nanostructure layer is disposed on the substrate.

Fig. 4 and 5 are perspective views illustrating a nanostructure of a superlens employed in a lidar transmission system provided by an embodiment of the present application. Optionally, the superlens may be filled with air or other material that is transparent or translucent in the operating band between the nanostructures. According to embodiments of the present application, the absolute value of the difference between the refractive index of the filled material and the refractive index of the nanostructures should be greater than or equal to 0.5. As shown in fig. 4, the nanostructures may be polarization dependent structures that impart a geometric phase to incident light. As shown in FIG. 5, the nanostructures may be polarization insensitive structures that impart a propagation phase to the incident light.

According to an embodiment of the present application, as shown in fig. 6 to 8, wherein the nanostructure layer comprises superstructure units arranged in an array.

As shown in fig. 6, according to an embodiment of the present application, the superstructure units may be arranged in a fan shape. As shown in fig. 7, according to an embodiment of the present application, the superstructure units may be arranged in an array of regular hexagons. Furthermore, as shown in fig. 8, according to embodiments of the present application, the superstructure units may be arranged in a square array. Those skilled in the art will recognize that the superstructure units included in the nanostructure layer may also include other forms of array arrangements, and all such variations are contemplated within the scope of the present application.

According to embodiments of the present application, the superstructure unit may have a nanostructure. As shown in fig. 6 to 8, according to the embodiment of the present application, a nanostructure is disposed at a central position and/or a vertex position of each nanostructure unit, respectively. According to an embodiment of the present application, the nanostructure is an all-dielectric building block. Optionally, the working wavelength band of the superlens in the embodiment of the present application is a common wavelength band of the laser radar, including a near infrared wavelength band, such as 850nm, 905nm, 940nm, and 1550nm. Optionally, the period of the nanostructures is greater than or equal to 300nm and less than or equal to 3 μm. Optionally, the height of the nanostructures is greater than or equal to 300nm, less than or equal to 3 μm.

According to an embodiment of the present application, the nanostructure has a high transmittance in the near infrared band and an extinction coefficient of less than or equal to 0.1. According to embodiments of the present application, the nanostructures may be formed of at least one of the following materials: titanium oxide, silicon nitride, fused silica, aluminum oxide, gallium nitride, gallium phosphide, amorphous silicon, crystalline silicon, hydrogenated amorphous silicon, and the like.

The transmittance and phase modulation relationship of an alternative nanostructure provided by the embodiments of the present application is shown in fig. 9. FIG. 9 shows a graph of transmittance versus phase modulation for 1200nm high silicon nanostructures in a regular quadrilateral arrangement with a period of 600 nm.

Example 1

Illustratively, the embodiment of the present application provides a compact lidar transmission system, which includes a first superlens 100, a second superlens 200, a third superlens 300, and a light source 400. Wherein, the first superlens 100, the second superlens 200 and the third superlens 300 are sequentially disposed on the light emitting side of the light source 400 along the optical axis. Specifically, the ratio of the distance from the light emitting surface of the light source 400 to the third superlens 300 to the equivalent focal length of the system is less than or equal to 1. The ratio of the distance from the light emitting surface of the light source 400 to the first superlens 100 to the equivalent focal length of the system is less than or equal to 0.2. The light source 400 includes 21 point light sources having a divergence angle of 20 ° at a full angle, and the interval between the adjacent point light sources is 20 μm.

Further, as shown in fig. 1, a distance d from a light emitting surface of the light source 400 to the first superlens 100 ₁ Equal to 0.6mm. The distance d between the first superlens 100 and the second superlens 200 ₂ Equal to 0.9mm. The distance d between the second and

third superlenses

200 and 300 ₃ Equal to 1.99mm. The working distance WD of the system being equal to d ₁ . The total system length TTL of the system is equal to d ₁ 、d ₂ And d ₃ And (3) is (a).

Preferably, in embodiment 1, the operating band of the compact lidar transmission system is 1550nm. The material of the substrate of the first, second and

third superlenses

100, 200 and 300 is fused silica, and the nanostructure is a silicon cylinder. Wherein the height of the nano structure is 1000nm, and the period is 800nm.

The parameters of the compact lidar transmission system provided in example 1 are shown in table 1. In the light source 400, the parallelism of the second light beam corresponding to each point light source is shown in table 2.

TABLE 1

Parameter(s)	Numerical value
		Total System Length (TTL)	3.5mm
Working Distance (WD)	0.6mm
		Focal Length (FL)	6.2mm
Transmittance of light	80％

TABLE 2

Number of point light source	Parallelism of emergent ray
		1	0.07°
2	0.07°
		3	0.06°
4	0.05°
		5	0.04°
6	0.03°
		7	0.03°
8	0.02°
		9	0.02°
10	0.01°

Example 2

Illustratively, the embodiment of the present application provides a compact lidar transmission system, which includes a first superlens 100, a second superlens 200, a third superlens 300, and a light source 400. Wherein, the first superlens 100, the second superlens 200, and the third superlens 300 are sequentially disposed on a light emitting side of the light source 400 along an optical axis. Specifically, the ratio of the distance from the light emitting surface of the light source 400 to the third superlens 300 to the equivalent focal length of the system is less than or equal to 1. The ratio of the distance from the light emitting surface of the light source 400 to the first superlens 100 to the equivalent focal length of the system is less than or equal to 0.2. The light source 400 includes 21 point light sources having a divergence angle of 20 ° at a full angle, and the pitch between adjacent point light sources is 20 μm.

Further, as shown in FIG. 2, a distance d from a light emitting surface of the light source 400 to the first superlens 100 ₁ Equal to 0.4mm. The distance d between the first superlens 100 and the second superlens 200 ₂ Equal to 1.8mm. The distance d between the second and

third superlenses

200 and 300 ₃ Equal to 2.3mm. The working distance WD of the system being equal to d ₁ . The total system length TTL of the system is equal to d ₁ 、d ₂ And d ₃ The sum of (1).

Preferably, in embodiment 2, the operating band of the compact lidar transmission system is 1550nm. The material of the substrate of the first, second and

third superlenses

The parameters of the compact lidar transmission system provided in example 2 are shown in table 3. In the light source 400, the parallelism of the second light beam corresponding to each point light source is shown in table 4.

TABLE 3

Parameter(s)	Numerical value
		Total length of TTL system	4.5mm
WD working distance	0.4mm
		FL focal length	5.8mm
Transmittance of light	82％

TABLE 4

It should be noted that, since the optical path is reversible, the optical system including at least one superlens in the compact lidar transmitting system provided by the embodiment of the present application may be used in a compact lidar receiving system.

The superlens adopted by the laser radar transmitting system provided by the embodiment of the application can be processed by a semiconductor process to realize mass production. The semiconductor process can reduce the cost of the super lens and improve the consistency of the mass production of the super lens.

To sum up, the small-size lidar transmission system that this application embodiment provided has reduced lens quantity, system overall length and working distance among the lidar transmission system through first super lens, second super lens and third super lens, has reduced lidar transmission system's volume, has promoted lidar's miniaturization. The small laser radar transmitting system provided by the embodiment of the application has the advantages of light weight, small size, simple structure and low cost.

The above description is only a specific implementation of the embodiments of the present application, but the scope of the embodiments of the present application is not limited thereto, and any person skilled in the art can easily conceive of changes or substitutions within the technical scope of the embodiments disclosed in the present application, and all the changes or substitutions should be covered by the scope of the embodiments of the present application. Therefore, the protection scope of the embodiments of the present application shall be subject to the protection scope of the claims.

Claims

1. A compact lidar transmission system characterized in that the system comprises a first superlens (100), a second superlens (200), a third superlens (300), and a light source (400);

wherein the first superlens (100), the second superlens (200) and the third superlens (300) are sequentially arranged on the light emitting side of the light source (400) along the same optical axis;

the ratio of the distance from the light emitting surface of the light source (400) to the third super lens (300) to the equivalent focal length of the system is less than or equal to 1;

the ratio of the distance from the light emitting surface of the light source (400) to the first superlens (100) to the equivalent focal length is less than or equal to 0.1.

2. The compact lidar transmission system of claim 1 wherein the initial beam of light from the light source (400) is modulated sequentially by the first superlens (100), the second superlens (200), and the third superlens (300) and converted to a second beam of light;

the divergence angle of the second light beam is less than or equal to 0.1 °.

3. The compact lidar transmission system of claim 1 wherein the light source (400) comprises a plurality of point light sources arranged in an array.

4. A compact lidar transmission system according to claim 3, wherein the divergence angle of the point source is 20 ° throughout.

5. The compact lidar transmission system of claim 3 wherein adjacent ones of the light sources (400) are spaced apart by 20 μm.

6. The compact lidar transmission system of any of claims 3 to 5, wherein said light source (400) comprises 21 point light sources arranged in an array.

7. The compact lidar transmission system of claim 1 wherein the thickness of the first superlens (100), the second superlens (200), and the third superlens (300) is less than or equal to 0.3mm.

8. The compact lidar transmission system of claim 1 wherein the third superlens (300) has a diameter of less than or equal to 2mm.

9. The compact lidar transmission system of claim 1 wherein the distance from the light source (400) to the first superlens (100) is greater than 0.2mm and less than 0.8mm;

the distance between the first superlens (100) and the second superlens (200) is more than 0.5mm and less than 2.0mm;

the distance between the second super lens (200) and the third super lens (300) is larger than 1.5mm and smaller than 2.5mm.

10. The compact lidar transmission system of claim 1 further comprising a MEMS galvanometer (500);

the initial light beam emitted by the light source (400) is modulated by the first superlens (100), the second superlens (200) and the third superlens (300) in sequence and then converted into a second light beam;

the divergence angle of the second light beam is less than or equal to 0.1 °;

the second light beam enters the MEMS galvanometer (500), and scanning is achieved through the movement of the MEMS galvanometer (500).

11. The compact lidar transmission system of claim 10, further comprising a mirror;

the reflecting mirror is positioned between the third super lens (300) and the MEMS galvanometer (500) and is used for reflecting the second light beam to the MEMS galvanometer (500).

12. The compact lidar transmission system of claim 1 wherein the first superlens (100), the second superlens (200), and the third superlens (300) each comprise a substrate and a nanostructure layer;

the nanostructure layer comprises nanostructures arranged in an array;

the nanostructure layer is disposed on the substrate.

13. The compact lidar transmission system of claim 12, wherein the nanostructure has a period of greater than or equal to 300nm and less than or equal to 3 μ ι η.

14. The compact lidar transmission system of claim 12, wherein the height of the nanostructures is greater than or equal to 300nm and less than or equal to 3 μm.

15. The compact lidar transmission system of any of claims 12-14, wherein the nanostructure is a polarization insensitive structure.

16. The compact lidar transmission system of any of claims 12-14, wherein the nanostructure is a polarization dependent structure.