Patent ID: 12259472

Reference signs:10—lens;11—first optical surface;12—second optical surface;20—photonic chip;21—cladding layer;22—receiving waveguide core layer;221—first end surface;222—second end surface;23—emission waveguide core layer;24—incident waveguide core layer;25—photoelectric detection module;251—frequency mixer;252—balanced photodetector;26—light splitting module;261—first light splitter;262—second light splitter;27—input waveguide core layer; AA′—first preset direction; BB′—second preset direction; OO′—optical axis; PP′—focal plane; L1—defocus distance; and2—light spot.

DETAILED DESCRIPTION

To make the objectives, technical solutions, and advantages of this application more comprehensible, the following further describes this application in detail with reference to accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely used to explain this application but are not intended to limit this application.

A LiDAR is a radar system that emits a laser beam to detect characteristics such as position, speed, or the like of a target object. From the perspective of working principles, there is no fundamental difference between the LiDAR and microwave radar. The LiDAR emits a detection signal to a target object, then compares a received echo signal reflected from the target object with a local oscillator signal, and can obtain relevant parameters such as distance, azimuth, height, speed, attitude, and even shape of the target object after appropriate processing of the reflected echo signal. Therefore, the LiDAR can be applied to navigation avoidance, obstacle recognition, ranging, speed measurement, autonomous driving and other scenarios of automobile, robot, logistics vehicle, patrol vehicle and other products.

The LiDAR can be divided into a pulse LiDAR and a coherent LiDAR by modulation methods. The coherent LiDAR further includes a frequency modulated continuous wave (FMCW) LiDAR.

In an FMCW LiDAR system, a multi-sided rotating mirror and/or a microelectro-mechanical system (MEMS) galvanometer is usually used to implement beam scanning of a detection signal, to form a detection field of view outside the LiDAR, thereby detecting a target object within the detection field of view. However, when the FMCW LiDAR is working, as the multi-sided rotating mirror rotates and/or the MEMS galvanometer rotates to achieve scanning, a position of a light spot formed by focusing the echo signal on a light receiving device is likely to shift, that is, the foregoing walk-off effect exists. Such a walk-off effect not only affects collection efficiency of the echo signal and reduces the optical coupling efficiency, but also may even cause the LiDAR to lose a capability of detecting signal light, thereby affecting overall performance of the LiDAR.

To resolve the foregoing technical problem, referring toFIG.1toFIG.4, a first aspect of this application provides a LiDAR, which can effectively improve the minimum optical coupling efficiency of the echo signal, thereby improving the light detection performance of the LiDAR.

The LiDAR includes a lens10and a photonic chip20. An optical axis OO′ of the lens10extends along a first preset direction AA′. The lens10is configured to receive an echo signal and output the echo signal to the photonic chip20, and the echo signal is formed after a detection signal emitted by the LiDAR is reflected or scattered by the target object. The photonic chip20and the lens10are spaced apart along the first preset direction AA′. The photonic chip20includes a cladding layer21and two or more receiving waveguide core layers22embedded in the cladding layer21. All the receiving waveguide core layers22are located at an end of the cladding layer21that is closer to the lens10and are spaced apart along a second preset direction BB′. The second preset direction BB′ intersects with the first preset direction AA′. Each receiving waveguide core layer22has a first end surface221and a second end surface222opposite to each other, the first end surface221is closer to the lens10than the second end surface222, and the first end surface221is configured to receive the echo signal output by the lens10; and there is a distance between a first end surface221of at least one receiving waveguide core layer22and a focal plane PP′ of the lens10.

A specific structure of the LiDAR is described below with reference toFIG.1toFIG.10.

As shown inFIG.1toFIG.4, the LiDAR includes a lens10and a photonic chip20.

The lens10is a component for changing an optical path and adjusting a shape of a light spot in the LiDAR. The lens10can be made of plastic or glass.

The optical axis OO′ of the lens10extends along the first preset direction AA′. In other words, the first preset direction AA′ is an extension direction of the optical axis OO′ of the lens10. The lens10is configured to receive an echo signal and output the echo signal to the photonic chip20. When the LiDAR works, the LiDAR can emit a detection signal to a target object within a detection field of view. The detection signal is reflected or scattered by the target object to form the foregoing echo signal. The lens10has a first optical surface11closer to the target object and a second optical surface12farther away from the target object. The echo signal is incident into the lens10through the first optical surface11, directed out of the lens10from the second optical surface12and further emitted to the photonic chip20. The lens10is configured to focus a laser beam incident through the first optical surface11, so that the focused laser beam is incident on the photonic chip20.

As shown inFIG.1toFIG.4, the photonic chip20is used as a component for receiving the echo signal output by the lens10in the LiDAR, that is, the foregoing light receiving device.

The photonic chip20and the lens10are spaced apart along the first preset direction AA′, that is, the photonic chip20is disposed on the optical axis OO′ of the lens10and does not contact the lens10.

The photonic chip20includes a substrate (not shown), a cladding layer21and a receiving waveguide core layer22. The substrate is a base material during the formation process of the photonic chip20, and a manufacturing material of the substrate may include, but is not limited to, silicon dioxide. Certainly, in another embodiment of this application, the substrate can also be omitted. The cladding layer21is laid on the substrate, is a main structure of the photonic chip20, and is also a structure to which the foregoing receiving waveguide core layer22is attached. A manufacturing material of the cladding layer21may include, but is not limited to, silicon dioxide. The receiving waveguide core layer22is used as a structure for receiving the echo signal output by the lens10in the photonic chip20. A manufacturing material of the receiving waveguide core layer22may include, but is not limited to, silicon and silicon nitride.

The receiving waveguide core layer22is embedded in the cladding layer21, that is, the cladding layer21wraps the receiving waveguide core layer22. A refractive index of the receiving waveguide core layer22is greater than that of the cladding layer21, then the receiving waveguide core layer22and the cladding layer21jointly form an optical waveguide structure, and the echo signal can propagate via total reflection in the receiving waveguide core layer after entering the receiving waveguide core layer22.

The receiving waveguide core layer22is located at one end of the cladding layer21that is closer to the lens10. The receiving waveguide core layer22has a first end surface221and a second end surface222. The first end surface221and the second end surface222are disposed opposite to each other. The first end surface221is closer to the lens10than the second end surface222and is exposed on the end surface of the cladding layer21that faces toward the lens10. The first end surface221is configured to receive the echo signal output by the lens10, and the second end surface222is used for the echo signal to exit the receiving waveguide core layer22. In this embodiment, the receiving waveguide core layer22extends along the first preset direction AA′, and the first end surface221and the second end surface222are disposed opposite to each other along the first preset direction AA′. It can be understood that, in another embodiment of this application, the receiving waveguide core layer22can also extend linearly or curvedly in another direction, and the first end surface221and the second end surface222are disposed opposite to each other along another direction. The echo signal output by the lens10is incident into the receiving waveguide core layer22through the first end surface221, and is emitted out of the receiving waveguide core layer22from the second end surface222after being totally reflected at an interface between the receiving waveguide core layer22and the cladding layer21. Herein, it should be noted that the receiving waveguide core layer22and the cladding layer21have the same width in the figure, but a width relationship therebetween is not limited in this application. The width of the cladding layer21can also be greater than that of the receiving waveguide core layer22, provided that the foregoing receiving waveguide core layer22is provided at the end of the cladding layer21that is closer to the lens10.

In this embodiment, the photonic chip20includes multiple receiving waveguide core layers22, where “multiple” in this application means “two or more.” For example, the photonic chip20may include two, three, four, five, six or more receiving waveguide core layers22. The specific number of receiving waveguide core layers22is not limited herein and can be designed properly by a person skilled in the art based on an actual requirement. All the receiving waveguide core layers22are spaced apart along the second preset direction BB′, that is, any two receiving waveguide core layers22do not come into contact along the second preset direction BB′. The second preset direction BB′ intersects with the first preset direction AA′. That is, in a plane in which the second preset direction BB′ and the first preset direction AA′ are located, the second preset direction BB′ is not parallel to the first preset direction AA′ or the second preset direction BB′ has a component perpendicular to the first preset direction AA′. In this embodiment, the second preset direction BB′ is perpendicular to the first preset direction AA′. It can be understood that, in another embodiment of this application, the second preset direction BB′ and the first preset direction AA′ can also form another angle.

It should be noted that as a detection distance of the detection signal increases, time of flight of the detection signal also increases. During the time of flight of the detection signal, the foregoing scanning device has already shifted by an angle relative to a position when the detection signal is emitted. The angle may gradually increase as the time of flight of the detection signal increases. Therefore, shift of a position at which the echo signal formed after the detection signal is reflected or scattered by the target object finally arrives at the photonic chip20also gradually increases. Because a scanning direction of the LiDAR is actually equivalent to a coupling of a horizontal scanning direction and a vertical scanning direction, shift of a position at which the echo signal finally arrives at the photonic chip has position shift components in directions of the walk-off effect caused in the two scanning directions. Because a field of view in the horizontal scanning direction is larger than a field of view in the vertical scanning direction, a scanning rate in the horizontal scanning direction is generally greater than a scanning rate in the vertical scanning direction, then a position shift component in the direction of the walk-off effect (hereinafter, referred to as a first component direction) caused in the horizontal scanning direction is greater than a position shift component in the direction of the walk-off effect (hereinafter, referred to as a second component direction) caused in the vertical scanning direction. Receiving waveguide core layers22in the photonic chip20are structures for receiving an echo signal. In this embodiment, an arrangement direction of the receiving waveguide core layers22is consistent with the first component direction. It can be understood that, in another embodiment of this application, the arrangement direction of the receiving waveguide core layers22can also be consistent with an actual shift direction of the echo signal on the photonic chip20, which can be specifically implemented by adjusting a disposition angle of the photonic chip20.

Generally, the echo signal output by the lens10forms a light spot2on the side of the lens10with the second optical surface12. To focus light spots2on the photonic chip20, the first end surface221of each receiving waveguide core layer22and the focal plane PP′ of the lens10overlap. The focal plane PP′ of the lens10marked with dotted lines inFIG.2andFIG.4overlap with the first end surface221of the receiving waveguide core layer22. However, in the foregoing solution, when the light spot2is located between two adjacent receiving waveguide core layers22, more energy cannot enter the receiving waveguide core layer22; and if a distance between the two adjacent receiving waveguide core layers22is greater than or equal to the size of the light spot2of the echo signal on the focal plane PP′, it is possible that each receiving waveguide core layer22cannot receive the echo signal at all. That is, the optical coupling efficiency of the photonic chip20is extremely low, and may even be as low as or close to 0. To overcome the foregoing shortcoming, in this application, the photonic chip20is further improved. In some embodiments, there is a distance between the first end surface221of at least one receiving waveguide core layer22and the focal plane PP′ of the lens10(that is, a plane that passes through a focal point of the lens10and that is perpendicular to the optical axis OO′ of the lens10). For ease of description, the distance between the first end surface221of the receiving waveguide core layer22and the focal plane PP′ of the lens10is referred to as a “defocus distance L1” below. The defocus distance L1can be obtained by measuring a distance between the focal plane PP′ and a center point of the first end surface221.

It should be noted that, for the receiving waveguide core layer22whose first end surface221is at the defocus distance L1from the focal plane PP′, the first end surface221of the receiving waveguide core layer22can be closer to the lens10than the focal plane PP′ of the lens10(FIG.2). At this time, the echo signal output by the lens10forms a light spot2on the side of the lens10with the second optical surface12, and an area of projection of the light spot2on the photonic chip20is larger than an area of projection of the light spot2on the focal plane PP′ of the lens10. Certainly, the first end surface221of the receiving waveguide core layer22can also be farther away from the lens10than the focal plane PP′ of the lens10(FIG.4). At this time, the echo signal output by the lens10forms a light spot2on the side of the lens10with the second optical surface12, and an area of projection of the light spot2on the focal plane PP′ of the lens10is less than an area of projection of the light spot2on the photonic chip20. The “area of projection of the light spot2on the photonic chip20” may be an area of orthographic projection of the light spot2on the first end surface221of the receiving waveguide core layer22along a direction parallel to the optical axis OO′ of the lens10(that is, the first preset direction AA′), or may also be an area of oblique projection of the light spot2on the first end surface221of the receiving waveguide core layer22along a direction intersecting with the optical axis OO′ of the lens10. The “area of projection of the light spot2on the focal plane PP′ of the lens10” is an area of orthographic projection of the light spot2on the focal plane PP′ of the lens10along a direction parallel to the optical axis OO′ of the lens10.

Based on the LiDAR in the embodiments of this application, compared with a method for designing the first end surface221of the receiving waveguide core layer22to be coplanar with the focal plane PP′ of the lens10, in the method for setting a distance between the first end surface221of the at least one receiving waveguide core layer22and the focal plane PP′ of the lens10, a light spot2formed by the echo signal output by the lens10on a side of the lens10with the second optical surface12actually forms a larger light spot after being incident on the photonic chip20. In this way, when the light spot2moves to in between two adjacent receiving waveguide core layers22, a ratio of an area of the light spot2incident on the receiving waveguide core layer22to a total area of the light spot becomes larger, and therefore, the optical coupling efficiency of the echo signal can be improved, thereby improving light detection performance of the LiDAR.

In this embodiment, there is a distance between a first end surface221of each receiving waveguide core layer22and a focal plane PP′ of the lens10. Certainly, in another embodiment of this application, in all the receiving waveguide core layers22, there may also be distances between the first end surfaces221of some receiving waveguide core layers22and the focal plane PP′ of the lens10, and first end surfaces221of the other receiving waveguide core layers22are coplanar with the focal plane PP′ of the lens10.

It should be additionally noted that the “optical coupling efficiency” in this application refers to a ratio of energy of the echo signal that is received by the receiving waveguide core layer22and that is used for coherent detection together with the local oscillator signal to energy of the echo signal reaching a surface of the photonic chip20. The projection of the light spot2formed by the echo signal output by the lens10on the side of the lens10with the second optical surface12onto the photonic chip20may only cover a first end surface221of one receiving waveguide core layer22, or may cover first end surfaces221of multiple receiving waveguide core layers22. When the light spot2only covers the first end surface221of the receiving waveguide core layer22, the optical coupling efficiency of the echo signal can be obtained by calculating a ratio of an area of projection of the light spot2onto the first end surface221of the receiving waveguide core layer22to an area of the light spot; or when the light spot2covers the first end surfaces221of the multiple receiving waveguide core layers22, the optical coupling efficiency of the echo signal can be obtained by calculating a ratio of the maximum area of projection of the light spot2onto the first end surfaces221of the multiple receiving waveguide core layers22to the area of the light spot.

As shown inFIG.5toFIG.8,FIG.5is a diagram of an optical coupling efficiency curve of echo signals at different defocus distances L1. The abscissa represents a detection distance (or shift of the walk-off effect) measured in meters (if the abscissa represents the shift of the walk-off effect, the shift of the walk-off effect is measured in μm), and the ordinate represents the optical coupling efficiency. A curve S1 inFIG.5represents a preset threshold that needs to be met by the optical coupling efficiency of the echo signal in the LiDAR, and is a horizontal line. An echo signal having optical coupling efficiency greater than the preset threshold after entering the receiving waveguide core layer22is a valid signal. An echo signal having optical coupling efficiency less than the preset threshold after entering the receiving waveguide core layer22is an invalid signal. A curve S2 inFIG.5represents a curve indicating that the optical coupling efficiency of the echo signal entering the receiving waveguide core layer22changes along with a detection distance when the first end surface221of the receiving waveguide core layer22overlaps with the focal plane PP′ of the lens10. Projection of the light spot2corresponding to the curve S2 onto the surface of the photonic chip20is shown inFIG.6. A curve S3 inFIG.5represents a curve indicating that the optical coupling efficiency of the echo signal entering the receiving waveguide core layer22changes along with a detection distance when there is a first defocus distance between the first end surface221of the receiving waveguide core layer22and the focal plane PP′ of the lens10. Projection of the light spot2corresponding to the curve S3 onto the surface of the photonic chip20is shown inFIG.7. A curve S4 inFIG.5represents a curve indicating that the optical coupling efficiency of the echo signal entering the receiving waveguide core layer22changes along with a detection distance when there is a second defocus distance between the first end surface221of the receiving waveguide core layer22and the focal plane PP′ of the lens10. Projection of the light spot corresponding to the curve S4 onto the surface of the photonic chip20is shown inFIG.8. The second defocus distance is greater than the first defocus distance. InFIG.5, the curve S1 is used as a dividing line. For each curve, the greater the part above the curve S1, the greater the optical coupling efficiency of the echo signal in a matching scenario of the photonic chip20corresponding to the curve and the lens10. In addition, the flatter the shape of each curve, the more uniform the optical coupling efficiency of the echo signal in the matching scenario of the photonic chip20corresponding to the curve and the lens10, and the higher the optical coupling efficiency of the light spot2when between two waveguides. On the contrary, the greater the part below the curve S1, the lower the optical coupling efficiency of the echo signal at the defocus distance L1corresponding to the curve. It can be seen fromFIG.5that the optical coupling efficiency of the echo signal in the curve S4 is better than that of the echo signal in the curve S3, and the optical coupling efficiency of the echo signal in the curve S3 is better than that of the echo signal in the curve S2. That is, within a specific defocus range, the optical coupling efficiency increases as the defocus distance increases.

In addition, it should be additionally noted that because the detection distance is small and the energy of the echo signal is high, even if some optical coupling efficiency is reduced during short-distance detection, detection performance of the LiDAR is not greatly affected. Correspondingly, when the detection distance increases and the echo signal is emitted out of one receiving waveguide core layer22and enters another receiving waveguide core layer22, the LiDAR provided in this embodiment of this application can improve the optical coupling efficiency during this process, and then improve the optical coupling efficiency and optical power of the echo signal corresponding to detection for a slightly longer distance, which is of great significance.

It should be understood that although the calculation method for the optical coupling efficiency is obtained in the foregoing method in this embodiment, in another embodiment of this application, a calculation method for the optical coupling efficiency can also be obtained by calculating a ratio of a sum of areas of projection of the light spot2onto all the receiving waveguide core layers22to an area of the light spot. A specific obtaining method is not limited in this application, provided that the same standard is used for calculation when the curve shown inFIG.5is obtained.

Further, as shown inFIG.2andFIG.4, it can be understood that when there are distances between the first end surfaces221of all the receiving waveguide core layers22and the focal plane PP′ of the lens10, it is possible that distances between first end surfaces221of some receiving waveguide core layers22and the focal plane PP′ of the lens10are first defocus distances, and distances between first end surfaces221of the other receiving waveguide core layers22and the focal plane PP′ of the lens10are second defocus distances. The first defocus distance and the second defocus distance are unequal. To reduce overall processing difficulty of the photonic chip20, in some embodiments, distances between the first end surfaces221of all the receiving waveguide core layers22and the focal plane PP′ of the lens10are designed to be equal along the first preset direction AA′ (that is, the direction of the optical axis OO′ of the lens10).

Further, as shown inFIG.2andFIG.4, it can be understood that the echo signal output by the lens10forms a light spot2on the side of the lens10with the second optical surface12. When the first end surface221of the receiving waveguide core layer22is farther away from the lens10than the focal plane PP′ of the lens10, a distance between the lens10and the first end surface221of the receiving waveguide core layer22is equal to the focal length of the lens10plus the foregoing “defocus distance L1”. To reduce the overall volume of the LiDAR, in some embodiments, the focal plane PP′ of the lens10is designed to be located between the first end surface221and the second end surface222of at least one receiving waveguide core layer22along the first preset direction AA′. At this time, a distance between the lens10and the first end surface221of the receiving waveguide core layer22is equal to the focal length of the lens10minus the foregoing “defocus distance L1”. Preferably, when distances between the first end surfaces221of all the receiving waveguide core layers22and the focal plane PP′ of the lens10are equal along the first preset direction AA′, the focal plane PP′ of the lens10is located between the first end surfaces221and the second end surfaces222of all the receiving waveguide core layers22.

Further, referring toFIG.7andFIG.8again, in a case that the focal length of the lens10and the maximum incident angle of the receiving waveguide core layer22are relatively definite, a value of the defocus distance L1determines a value of the area of the projection of the light spot2formed by the echo signal output by the lens10on the side of the lens10with the second optical surface12onto the photonic chip20, and therefore, determines the optical coupling efficiency of the echo signal. For example, the larger the defocus distance L1, the larger the value of the area of the projection of the light spot2formed by the echo signal output by the lens10on the side of the lens10with the second optical surface12onto the photonic chip20, and possibly, the higher the optical coupling efficiency the echo signal. Certainly, this does not mean that the defocus distance L1is preferably as large as possible. An excessively large defocus distance L1is not conducive to concentration of energy of the light spot2onto the photonic chip20, and also affects optical power for the echo signal to enter the receiving waveguide core layer22. Therefore, to ensure better optical coupling efficiency and optical power for the echo signal to enter the receiving waveguide core layer22, and ensure optimal light detection performance of the LiDAR, a specific limitation on the defocus distance L1may include, but is not limited to, one or more of the following embodiments.

In the first embodiment, 5 μm≤L1≤60 μm. For example, a specific value of the defocus distance L1may be, but is not limited to, 5 μm, 8 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm or 60 μm. Generally, the maximum linear size of the light spot2formed by the echo signal on the surface of the photonic chip20along the second preset direction BB′ is between 3 μm and 20 μm, and the maximum incident angle of the receiving waveguide core layer22is between 10° and 40°. Based on the foregoing parameters, it can be seen that the defocus distance L1is between 3.8 mm to 113 mm. Certainly, not only the size of the light spot2formed by the echo signal needs to fall within a proper range, the LiDAR also needs to have a volume as small as possible, and therefore, the defocus distance L1is preferably between 5 mm and 60 mm.

In a second embodiment, D/(2 tan θ)<L1<(W+D)/(2 tan θ), where θ is an angle (that is, the maximum incident angle of the receiving waveguide core layer22) corresponding to a numerical aperture of the receiving waveguide core layer22, W is width of the receiving waveguide core layer22along the second preset direction BB′, and D is the distance between two adjacent receiving waveguide core layers22. Through such setting, on the one hand, the maximum linear size of the light spot2formed by the echo signal in the second preset direction BB′ is larger than the distance between the two adjacent receiving waveguide core layers22, to ensure that the light spot2can enter at least one receiving waveguide core layer22when located between the two receiving waveguide core layers22, thereby improving the optical coupling efficiency of the light spot2when located between the two adjacent receiving waveguide core layers22; on the other hand, the maximum size of the light spot2formed by the echo signal in the second preset direction BB′ is less than a sum of width of the receiving waveguide core layer22and the distance between the two adjacent receiving waveguide core layers22, to prevent an excessively large size of the light spot formed by the echo signal from causing a disadvantage of excessively low optical power of the light spot when entering the receiving waveguide core layer22finally.

Optionally, the photonic chip20meets: 100 nm≤W≤500 nm. For example, a specific value of W can be, but is not limited to, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm or 500 nm. Such setting is intended to ensure that the size of the first end surface221of the receiving waveguide core layer22is appropriate, so that the echo signal propagates in a single mode in the receiving waveguide core layer22. When the value of W exceeds a lower limit of the foregoing formula, the size of the first end surface221of the receiving waveguide core layer22is excessively small, which hinders the light spot2formed by the echo signal output by the lens10on the side of the lens10with the second optical surface12from being incident on the first end surface221of the receiving waveguide core layer22and from propagating within the receiving waveguide core layer22. When the value of W exceeds an upper limit of the foregoing formula, the echo signal is likely to excite multiple modes in the receiving waveguide core layer22, thereby affecting efficiency of subsequent beat frequency together with the local oscillator signal.

Optionally, the photonic chip20meets: 1 μm≤D≤10 μm. For example, a specific value of D may be, but is not limited to, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm. In this design, by designing the value of D properly, when the value of D satisfies the foregoing formula, the value of the distance between the two adjacent receiving waveguide core layers22is more appropriate, and the area of the projection of the light spot2formed by the echo signal output by the lens10on the side of the lens10with the second optical surface12into the gap between the two adjacent receiving waveguide core layers22is small, so that projection of the light spot2onto the surface of the receiving photonic chip20can fall onto the first end surface221of the receiving waveguide core layer22as much as possible, to improve the optical coupling efficiency of the echo signal as much as possible, thereby optimizing the light detection performance of the LiDAR. When the value of D exceeds the lower limit of the foregoing formula, the distance between adjacent receiving waveguide core layers22is excessively small, which is not conducive to overall processing of the photonic chip20and also needs more receiving waveguide core layers22to cover the same detection distance. When the value of D exceeds an upper limit of the foregoing formula, the distance between the two adjacent receiving waveguide core layers22is excessively large, and the area of the projection of the light spot2formed by the echo signal output by the lens10on the side of the lens10with the second optical surface12into the gap between the two adjacent receiving waveguide core layers22is large, and therefore, an area of projection of the light spot2onto the first end surface221of the receiving waveguide core layer22is small, and the optical coupling efficiency of the echo signal is low, which hinders optimization of the light detection performance of the LiDAR.

Further, as shown inFIG.2andFIG.4, it can be understood that distances between any two adjacent receiving waveguide core layers22along the second preset direction BB′ may be unequal. In other words, all the receiving waveguide core layers22may be spaced unequally along the second preset direction BB′. To reduce overall processing difficulty of the photonic chip20, in some embodiments, any two adjacent receiving waveguide core layers22are equally spaced along the second preset direction BB′. That is, all the receiving waveguide core layers22are equally spaced along the second preset direction BB′.

Further, as shown inFIG.9andFIG.10, to improve an integration level of the photonic chip20, the photonic chip20further includes an emission waveguide core layer23. The emission waveguide core layer23is embedded in the foregoing cladding layer21and forms an optical waveguide structure together with the cladding layer21. The emission waveguide core layer is configured to receive a detection signal generated by the LiDAR, and output the detection signal to the outside of the photonic chip20to detect the target object. The LiDAR emits a detection signal to the target object through the photonic chip20, then receives an echo signal reflected or scattered by the target object through the photonic chip20, compares the received echo signal with one local oscillator signal, and can obtain relevant parameters such as distance, azimuth, height, speed, attitude and even a shape of the target object after proper processing. It should be noted that the foregoing lens10can also be configured to receive the detection signal emitted by the LiDAR to the target object, that is, the lens10configured to receive the detection signal and the lens10configured to receive the echo signal are the same lens10. In this case, the detection signal enters the lens10through the second optical surface12and exits the lens10from the first optical surface11, and is directed to the target object after being collimated by the lens10. Certainly, the lens10for receiving the detection signal may also be another lens10independent of the lens10for receiving the echo signal.

In some embodiments, the emission waveguide core layer23is located at one end of the cladding layer21that is closer to the lens10. The emission waveguide core layer23extends along the first preset direction AA′. The optical axis OO′ of the lens10passes through the emission waveguide core layer23. The lens10is also configured to collimate the laser beam output from the emission waveguide core layer23. In some embodiments, an end surface of the emission waveguide core layer23that faces toward the lens10overlaps with the focal plane PP′ of the lens10, and collimated laser beams are parallel beams. At this time, it should be noted that because the end surface of the emission waveguide core layer23is located on the foregoing focal plane PP′ and there is a distance between the first end surface221of the receiving waveguide core layer22and the foregoing focal plane PP′, the end surface of the emission waveguide core layer23that faces toward the lens10and the first end surface221of the receiving waveguide core layer22are not in the same plane. At this time, the end surface of the cladding layer21that is closer to the lens10is a step-shaped surface. It can be understood that, in some other embodiments of this application, there may also be a distance between the end surface of the emission waveguide core layer23that faces toward the lens10and the focal plane PP′ of the lens10, that is, the emission waveguide core layer is disposed relative to the lens in a defocus manner. The first end surfaces221of the emission waveguide core layer23and the receiving waveguide core layer22can be located in the same plane. In this case, the end surface of the cladding layer21that is closer to the lens10is a plane. Further, to ensure that the detection signal emitted through the emission waveguide core layer23and the lens10is parallel beams or approximately parallel beams, the photonic chip20may also include a micro lens (not shown in the figure), and the micro lens is disposed on the end surface of the emission waveguide core layer23that is closer to the lens10and is configured to collimate the detection signal output by the emission waveguide core layer23, so that laser beams passing through the photonic chip20subsequently are approximately parallel beams.

As for positions of the receiving waveguide core layers22relative to the emission waveguide core layer23, as shown inFIG.9, all the receiving waveguide core layers22may be located on the same side of the emission waveguide core layer23along the foregoing second preset direction BB′; or as shown inFIG.10, all the receiving waveguide core layers22may also be disposed separately on two sides of the emission waveguide core layer23along the foregoing second preset direction BB′, that is, at least two receiving waveguide core layers22are located on two sides of the emission waveguide core layer23. It should be noted that, taking the second preset direction BB′ corresponding to a direction of the walk-off effect caused in the horizontal scanning direction as an example, a design in which all the receiving waveguide core layers22are located on the same side of the emission waveguide core layer23is suitable for a situation in which the horizontal scanning direction is a one-way scanning direction, for example, scanning using a rotating mirror; and a design in which the receiving waveguide core layers22are located on two sides of the emission waveguide core layer23separately is suitable for a situation in which a horizontal scanning direction is a two-way scanning direction, for example, scanning using a galvanometer.

Further, as shown inFIG.9andFIG.10, to further improve an integration level of the photonic chip20, in some embodiments, the photonic chip20also includes a photoelectric detection module25. The photoelectric detection module25is configured to receive a local oscillator signal generated by the LiDAR and the echo signal output through the second end surface222of the receiving waveguide core layer22. Each photoelectric detection module25is disposed corresponding to one receiving waveguide core layer22.

In some embodiments, each photoelectric detection module25includes a frequency mixer251and a balanced photodetector252. The frequency mixer251has two input ports, one input port is configured to receive the local oscillator signal generated by the LiDAR, and the other input port is configured to receive the echo signal output by the foregoing receiving waveguide core layer22. The local oscillator signal and the echo signal can be subjected to frequency beating in the frequency mixer251to obtain two beat frequency signals. The frequency mixer251may be a 180-degree frequency mixer251, and a difference between phases of the two beat frequency signals output by the frequency mixer251is 180 degrees. The balanced photodetector252is connected to an output end of the frequency mixer251. The balanced photodetector252is configured to perform balance detection on the two beat frequency signals, thereby obtaining two electrical signals related to the two beat frequency signals. An information processing module of the LiDAR can calculate relevant detection information such as distance, speed and reflectivity of the target object relative to the LiDAR based on the foregoing two electrical signals. It should be noted that a specific manifestation form of the photoelectric detection module25is not limited to inclusion of the frequency mixer251and the balanced photodetector252. A photoelectric detection module25in another specific manifestation form can also be used, provided that the photoelectric detection module25in another specific manifestation form can receive the foregoing local oscillator signal and the foregoing detection signal, and can convert the foregoing beat frequency signal generated based on the local oscillator signal and the detection signal into the foregoing electrical signal. For example, in some other embodiments, the photoelectric detection module25includes a photodetector, and the photodetector not only can be configured to receive the foregoing local oscillator signal and the foregoing detection signal to subject the foregoing local oscillator signal and the foregoing detection signal to frequency beating to generate the foregoing beat frequency signal, but also can convert the generated beat frequency signal into the foregoing electrical signal.

Further, as shown inFIG.9andFIG.10, to further improve the integration level of the photonic chip20, in some embodiments, the photonic chip20further includes an input waveguide core layer27and a light splitting module26. The input waveguide core layer27is configured to receive the source light signal generated by the LiDAR. The light splitting module26is configured to receive the source light signal output by the input waveguide core layer27and split the source light signal into at least a detection signal and two or more local oscillator signals, the detection signal is output to the emission waveguide core layer23, and the local oscillator signal is output to the photoelectric detection module25.

In some embodiments, the input waveguide core layer27is embedded in the foregoing cladding layer21and forms an optical waveguide structure together with the cladding layer21. The light splitting module26includes a first light splitter261and a second light splitter262. A part of the source light signal output by the input waveguide core layer27is split into the foregoing detection signal by the first light splitter261, and the remaining part of the source light signal output by the input waveguide core layer27is sequentially split into multiple beams of the foregoing local oscillator signals by the first light splitter261and the second light splitter262.

Further, as shown inFIG.9andFIG.10, in some embodiments, the LiDAR also includes a laser (not shown in the figure), and the LiDAR is configured to generate a source light signal.

In some embodiments, the source light signal is generated by a laser and output to the input waveguide core layer27, and a part of the source light signal output by the input waveguide core layer27is split into the foregoing detection signal by the first light splitter261. A remaining part of the source light signal output by the input waveguide core layer27is sequentially split into multiple beams of the foregoing local oscillator signals by the first light splitter261and the second light splitter262. The detection signal output by the first light splitter261is output to the target object via the emission waveguide core layer23. The detection signal is reflected or scattered by the target object to form an echo signal, and both the echo signal and the local oscillator signal are output to the frequency mixer251. The frequency mixer251subjects the echo signal and the local oscillator signal to frequency beating to generate two beat frequency signals, and the two beat frequency signals are output to the balanced photodetector252through two output ends of the frequency mixer251. The two beat frequency signals are subjected to balance detection processing by the balanced photodetector252to generate two electrical signals, and the two electrical signals are output to the information processing module of the LiDAR through the output end of the balanced photodetector252. After the two electrical signals are subjected to information processing by the information processing module of the LiDAR, the relevant detection information such as distance, speed and reflectivity of the target object relative to the LiDAR can be obtained.

In summary, the LiDAR provided in this embodiment of this application includes a lens10and a photonic chip20. There is a distance between the first end surface221of the receiving waveguide core layer22in the photonic chip20and the focal plane PP′ of the lens10, so that the light spot of the echo signal projected to the surface of the photonic chip20is large, and an area of the light spot projected to the first end surface221of the receiving waveguide core layer22accounts for a larger proportion when the light spot is located between two adjacent receiving waveguide core layers22, which can alleviate the current situation of low minimum optical coupling efficiency of the echo signal to some extent. Therefore, the LiDAR can have better detection performance.

A second aspect of this application provides a mobile device, where the mobile device includes the foregoing LiDAR. The mobile device can include, but is not limited to, a smart device such as a vehicle, a robot or an unmanned aerial vehicle. In such a design, the mobile device having the foregoing LiDAR can also alleviate an existing problem that the minimum optical coupling efficiency of an echo signal is low due to a walk-off effect in related art.

The same or similar reference signs in the drawings of the embodiments correspond to the same or similar components. In descriptions of this application, it should be understood that azimuth or position relationships indicated by terms such as “above”, “under”, “left”, and “right” are based on the azimuth or position relationships shown in the accompanying drawings, are merely intended to describe this application and simplify the descriptions, but are not intended to indicate or imply that the specified device or element shall have specific azimuth or be formed and operated in specific azimuth, and therefore, the terms for describing the position relationships in the drawings are only used for exemplary illustration, and should not be construed as a limitation on this patent. A person of ordinary skill in the art can understand specific meanings of the foregoing terms based on a specific situation.

The foregoing descriptions are only preferred embodiments of this application, and are not intended to limit this application. Any modification, equivalent replacement and improvement made within the spirit and principle of this application shall be included within the protection scope of this application.